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Recent discoveries in biology have highlighted the importance of protein and RNA-based condensates as an alternative to classical membrane-bound organelles. Here, we demonstrate the design of pure RNA condensates from nanostructured, star-shaped RNA motifs. We generate condensates using two different RNA nanostar architectures: multi-stranded nanostars whose binding interactions are programmed via linear overhangs, and single-stranded nanostars whose interactions are programmed via kissing loops. Through systematic sequence design, we demonstrate that both architectures can produce orthogonal (distinct and immiscible) condensates, which can be individually tracked via fluorogenic aptamers. We also show that aptamers make it possible to recruit peptides and proteins to the condensates with high specificity. Successful co-transcriptional formation of condensates from single-stranded nanostars suggests that they may be genetically encoded and produced in living cells. We provide a library of orthogonal RNA condensates that can be modularly customized and offer a route toward creating systems of functional artificial organelles for the task of compartmentalizing molecules and biochemical reactions.

Microglia, the immune cells of the central nervous system, are dynamic and heterogenous cells. While single cell RNA sequencing has become the conventional methodology for evaluating microglial state, transcriptomics do not provide insight into functional changes, identifying a critical gap in the field. Here, we propose a novel organelle phenotyping approach in which we treat live human induced pluripotent stem cell-derived microglia (iMGL) with organelle dyes staining mitochondria, lipids, lysosomes and acquire data by live-cell spectral microscopy. Dimensionality reduction techniques and unbiased cluster identification allow for recognition of microglial subpopulations with single-cell resolution based on organelle function. We validated this methodology using lipopolysaccharide and IL-10 treatment to polarize iMGL to an "inflammatory" and "anti-inflammatory" state, respectively, and then applied it to identify a novel regulator of iMGL function, complement protein C1q. While C1q is traditionally known as the initiator of the complement cascade, here we use organelle phenotyping to identify a role for C1q in regulating iMGL polarization via fatty acid storage and mitochondria membrane potential. Follow up evaluation of microglia using traditional read outs of activation state confirm that C1q drives an increase in microglia pro-inflammatory gene production and migration, while suppressing microglial proliferation. These data together validate the use of a novel organelle phenotyping approach and enable better mechanistic investigation of molecular regulators of microglial state.

Photobodies (PBs) are membraneless subnuclear organelles that self-assemble via concentration-dependent liquid-liquid phase separation (LLPS) of the plant photoreceptor and thermosensor phytochrome B (PHYB). The current PHYB LLPS model posits that PHYB phase separates randomly in the nucleoplasm regardless of the cellular or nuclear context. Here, we established a robust Oligopaints method in Arabidopsis to determine the positioning of individual PBs. We show surprisingly that even in PHYB overexpression lines - where PHYB condensation would be more likely to occur randomly - PBs positioned at twelve distinct subnuclear locations distinguishable by chromocenter and nucleolus landmarks, suggesting that PHYB condensation occurs nonrandomly at preferred seeding sites. Intriguingly, warm temperatures reduce PB number by inducing the disappearance of specific thermo-sensitive PBs, demonstrating that individual PBs possess different thermosensitivities. These results reveal a nonrandom PB nucleation model, which provides the framework for the biogenesis of spatially distinct individual PBs with diverse environmental sensitivities within a single plant nucleus.

The endoplasmic reticulum (ER) forms an interconnected network of tubules stretching throughout the cell. Understanding how ER functionality relies on its structural organization is crucial for elucidating cellular vulnerability to ER perturbations, which have been implicated in several neuronal pathologies. One of the key functions of the ER is enabling Ca[Formula: see text] signaling by storing large quantities of this ion and releasing it into the cytoplasm in a spatiotemporally controlled manner. Through a combination of physical modeling and live-cell imaging, we demonstrate that alterations in ER shape significantly impact its ability to support efficient local Ca[Formula: see text] releases, due to hindered transport of luminal content within the ER. Our model reveals that rapid Ca[Formula: see text] release necessitates mobile luminal buffer proteins with moderate binding strength, moving through a well-connected network of ER tubules. These findings provide insight into the functional advantages of normal ER architecture, emphasizing its importance as a kinetically efficient intracellular Ca[Formula: see text] delivery system.

Pinpointing functional, structural, and redox-sensitive cysteines is a central challenge of chemoproteomics. Here, we present a protocol comprising two dual-enrichment cysteine chemoproteomic techniques that enable capture of cysteines (Cys-LoC) and quantification of cysteine oxidation state (Cys-LOx) in a localization-specific manner. We describe steps for utilizing TurboID-mediated protein biotinylation for enrichment of compartment-specific proteins, followed by click-mediated biotinylation and enrichment of cysteine-containing peptides. Thus, changes to compartment-specific cysteine identification and redox state can be assessed in a variety of contexts. For complete details on the use and execution of this protocol, please refer to Yan et al. (2023).1.

Numerous biological systems contain vesicle-like biomolecular compartments without membranes, which contribute to diverse functions including gene regulation, stress response, signaling, and skin barrier formation. Coacervation, as a form of liquid-liquid phase separation (LLPS), is recognized as a representative precursor to the formation and assembly of membrane-less vesicle-like structures, although their formation mechanism remains unclear. In this study, a coacervation-driven membrane-less vesicle-like structure is constructed using two proteins, GG1234 (an anionic intrinsically disordered protein) and bhBMP-2 (a bioengineered human bone morphogenetic protein 2). GG1234 formed both simple coacervates by itself and complex coacervates with the relatively cationic bhBMP-2 under acidic conditions. Upon addition of dissolved bhBMP-2 to the simple coacervates of GG1234, a phase transition from spherical simple coacervates to vesicular condensates occurred via the interactions between GG1234 and bhBMP-2 on the surface of the highly viscoelastic GG1234 simple coacervates. Furthermore, the shell structure in the outer region of the GG1234/bhBMP-2 vesicular condensates exhibited gel-like properties, leading to the formation of multiphasic vesicle-like compartments. A potential mechanism is proposed for the formation of the membrane-less GG1234/bhBMP-2 vesicle-like compartments. This study provides a dynamic process underlying the formation of biomolecular multiphasic condensates, thereby enhancing the understanding of these biomolecular structures.

We present super-resolution microscopy of isolated functional mitochondria, enabling real-time studies of structure and function (voltages) in response to pharmacological manipulation. Changes in mitochondrial membrane potential as a function of time and position can be imaged in different metabolic states (not possible in whole cells), created by the addition of substrates and inhibitors of the electron transport chain, enabled by the isolation of vital mitochondria. By careful analysis of structure dyes and voltage dyes (lipophilic cations), we demonstrate that most of the fluorescent signal seen from voltage dyes is due to membrane bound dyes, and develop a model for the membrane potential dependence of the fluorescence contrast for the case of super-resolution imaging, and how it relates to membrane potential. This permits direct analysis of mitochondrial structure and function (voltage) of isolated, individual mitochondria as well as submitochondrial structures in the functional, intact state, a major advance in super-resolution studies of living organelles.

Membrane contact sites (MCSs) are hubs allowing various cell organelles to coordinate their activities. The dynamic nature of these sites and their small size hinder analysis by current imaging techniques. To overcome these limitations, we here design a series of reversible chemogenetic reporters incorporating improved, low-affinity variants of splitFAST, and study the dynamics of different MCSs at high spatiotemporal resolution, both in vitro and in vivo. We demonstrate that these versatile reporters suit different experimental setups well, allowing one to address challenging biological questions. Using these probes, we identify a pathway in which calcium (Ca2+) signalling dynamically regulates endoplasmic reticulum-mitochondria juxtaposition, characterizing the underlying mechanism. Finally, by integrating Ca2+-sensing capabilities into the splitFAST technology, we introduce PRINCESS (PRobe for INterorganelle Ca2+-Exchange Sites based on SplitFAST), a class of reporters to simultaneously detect MCSs and measure the associated Ca2+ dynamics using a single biosensor. Studying membrane contact sites at high spatiotemporal resolution is still challenging. Here, authors introduce a series of dynamic chemogenetic reporters to visualize these subcellular regions and study the associated calcium signals. [ABSTRACT FROM AUTHOR]

Mitochondria are dynamic, intracellular organelles with a separate genome originating from prokaryotes. They perform numerous functions essential for cellular metabolism and energy production. Mitochondrial‐derived vesicles (MDVs) are single or double membrane‐enclosed vesicles, formed and released from the mitochondrial sub‐compartments into the cytosol, in response to various triggers. MDVs interact with other organelles such as lysosomes and peroxisomes or may be incorporated and excreted via extracellular vesicles (EVs). MDVs selectively incorporate diverse protein and lipid cargoes and are involved in various functions such as mitochondrial quality control, immunomodulation, energy complementation, and compartmentalization and transport. This review aims to provide a summary of the current knowledge of MDVs biogenesis, release, cargoes, and roles. [ABSTRACT FROM AUTHOR]

Neuronal information processing depends on converting membrane depolarizations into compartmentalized biochemical signals that can modify neuronal activity and structure. However, our understanding of how neurons translate electrical signals into specific biochemical responses remains limited, especially in the soma where gene expression and ion channel function are crucial for neuronal activity. Here, I emphasize the importance of physically compartmentalizing action potential‐triggered biochemical reactions within the soma. Emerging evidence suggests that somatic endoplasmic reticulum–plasma membrane (ER‐PM) junctions are specialized organelles that coordinate electrical and biochemical signaling. The juxtaposition of ion channels and signaling proteins at a prominent subset of these sites enables compartmentalized calcium and cAMP‐dependent protein kinase (PKA) signaling. I explore the hypothesis that these PKA‐containing ER‐PM junctions serve as critical sites for translating membrane depolarizations into PKA signals and identify key gaps in knowledge of the assembly, regulation, and neurobiological functions of this somatic signaling system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Selective autophagy is characterized by its ability to specifically degrade a certain substrate, rather than causing widespread cell autophagy. • The mechanisms underlying selective autophagy can be broadly dispersed in three steps: designation, targeting and sequestration, and degradation. • Numerous human diseases and their progression are closely linked to aberrant selective autophagy. • Deciphering the molecular mechanisms underlying selective autophagy provides a theoretical framework for treating relevant clinical disorders. • Regulation of selective autophagy by discovering and developing small-molecule agents has great clinical application prospects for the treatment of related diseases. Autophagy is an evolutionarily conserved turnover process for intracellular substances in eukaryotes, relying on lysosomal (in animals) or vacuolar (in yeast and plants) mechanisms. In the past two decades, emerging evidence suggests that, under specific conditions, autophagy can target particular macromolecules or organelles for degradation, a process termed selective autophagy. Recently, accumulating studies have demonstrated that the abnormality of selective autophagy is closely associated with the occurrence and progression of many human diseases, including neurodegenerative diseases, cancers, metabolic diseases, and cardiovascular diseases. This review aims at systematically and comprehensively introducing selective autophagy and its role in various diseases, while unravelling the molecular mechanisms of selective autophagy. By providing a theoretical basis for the development of related small-molecule drugs as well as treating related human diseases, this review seeks to contribute to the understanding of selective autophagy and its therapeutic potential. In this review, we systematically introduce and dissect the major categories of selective autophagy that have been discovered. We also focus on recent advances in understanding the molecular mechanisms underlying both classical and non-classical selective autophagy. Moreover, the current situation of small-molecule drugs targeting different types of selective autophagy is further summarized, providing valuable insights into the discovery of more candidate small-molecule drugs targeting selective autophagy in the future. On the other hand, we also reveal clinically relevant implementations that are potentially related to selective autophagy, such as predictive approaches and treatments tailored to individual patients. [ABSTRACT FROM AUTHOR]

Tapetal cells, like other parietal layer cells were small and oblong in the beginning. Shortly afterwards they incvcased in size and became binucleate, their cytoplasm being densely staincd with haematoxylin. Not a fow cells of the tapetum showed chromatin qranules in their nuclei. At the pollen tetrad stage, the tapetal cells had attained their maximum growth. The submicroscopic structure of the tapetal cells of the barley anthers has been investigated at the stages of a late tetrad and uninucleate pollen qrain before and after vacuolization. The tapetal cells of the barley as regards their structure and functions at these stages of development may be characterized as secretary ones. Their cytoplasm is abundant with cell organells. Numerous mitochondria and a Golgi apparatus are in close vicini ty with the cisterns of an endoplasmic reticulum. The presence of ribosomes on the onter cisternae of the stack relates the entire structure to the endoplasmic reticulum. Ocmiophilic substances apper in several places with respect to the tapetal cells. At the stage of an uninucleate pollen grain instead of the degenerated pr imary walls, surrounding every tapetal cell, a new wall is formed, which consists mainly of sporopollenin. [ABSTRACT FROM AUTHOR]

Photosynthetic eukaryotes have metabolic pathways that occur in distinct subcellular compartments. However, because metabolites synthesized in one compartment, including fixed carbon compounds and reductant generated by photosynthetic electron flows, may be integral to processes in other compartments, the cells must efficiently move metabolites among the different compartments. This review examines the various photosynthetic electron flows used to generate ATP and fixed carbon and the trafficking of metabolites in the green alga Chlamydomomas reinhardtii; information on other algae and plants is provided to add depth and nuance to the discussion. We emphasized the trafficking of metabolites across the envelope membranes of the two energy powerhouse organelles of the cell, the chloroplast and mitochondrion, the nature and roles of the major mobile metabolites that move among these compartments, and the specific or presumed transporters involved in that trafficking. These transporters include sugar-phosphate (sugar-P)/inorganic phosphate (Pi) transporters and dicarboxylate transporters, although, in many cases, we know little about the substrate specificities of these transporters, how their activities are regulated/coordinated, compensatory responses among transporters when specific transporters are compromised, associations between transporters and other cellular proteins, and the possibilities for forming specific 'megacomplexes' involving interactions between enzymes of central metabolism with specific transport proteins. Finally, we discuss metabolite trafficking associated with specific biological processes that occur under various environmental conditions to help to maintain the cell's fitness. These processes include C4 metabolism in plants and the carbon concentrating mechanism, photorespiration, and fermentation metabolism in algae. [ABSTRACT FROM AUTHOR]

Interorganelle contacts facilitate material exchanges and sustain the structural and functional integrity of organelles. Lipid droplets (LDs) of adipocytes are responsible for energy storage and mobilization responding to body needs. LD biogenesis defects compromise the lipid-storing capacity of adipocytes, resulting in ectopic lipid deposition and metabolic disorders, yet how the uniquely large LDs in adipocytes attain structural and functional maturation is incompletely understood. Here we show that the mammalian adipocyte-specific protein CLSTN3B is crucial for adipocyte LD maturation. CLSTN3B employs an arginine-rich segment to promote extensive contact and hemifusion-like structure formation between the endoplasmic reticulum (ER) and LD, allowing ER-to-LD phospholipid diffusion during LD expansion. CLSTN3B ablation results in reduced LD surface phospholipid density, increased turnover of LD-surface proteins, and impaired LD functions. Our results establish the central role of CLSTN3B in the adipocyte-specific LD maturation pathway that enhances lipid storage and maintenance of metabolic health under caloric overload in mice of both sexes. Proper lipid storage in adipocytes is critical for preventing ectopic lipid deposition and maintaining metabolic health. Here, the authors show the important role of the adipocyte-specific gene clstn3b in promoting lipid droplet maturation and enhancing the lipid storage capacity of adipocytes. [ABSTRACT FROM AUTHOR]

Although DNAzyme sensors have been widely developed for imaging metal ions, their application in specific subcellular compartments remains challenging due to low spatial controllability. Here we present a locally activatable, DNAzyme‐based sensing technology that enables subcellular compartment‐specific imaging of metal ions through ribosomal RNA (rRNA) regulated signal amplification. The system leverages a subcellularly encoded rRNA to locally activate DNAzyme‐based sensors, and further drives signal amplification via multiple turnover cleavage of molecular beacons, to significantly enhance sensitivity and spatial precision for metal‐ion imaging in specific organelles (e.g. mitochondria) or membraneless compartments (e.g. cytosol). Furthermore, we demonstrate that the system allows in situ monitoring of subcellular dynamics of mitochondrial Zn2+ during ischemia and the drug intervention. This study expands the DNAzyme toolbox for investigating the role of subcellular metal‐ion dynamics in disease processes. [ABSTRACT FROM AUTHOR]

Radial glia (RG) are the main progenitor cell type in the developing cortex. These cells are highly polarized, with a long basal process spanning the entire thickness of the cortex and acting as a support for neuronal migration. The RG cell terminates by an endfoot that contacts the pial (basal) surface. A shorter apical process also terminates with an endfoot that faces the ventricle, with a primary cilium protruding in the cerebrospinal fluid. These cell domains have particular subcellular compositions that are critical for the correct functioning of RG. When altered, this can affect proper development of the cortex, ultimately leading to cortical malformations, associated with different pathological outcomes. In this review, we focus on the current knowledge concerning the cell biology of these bipolar stem cells and discuss the role of their polarity in health and disease. [ABSTRACT FROM AUTHOR]

Peri-nuclear clustering (PNC) of chloroplasts has largely been described in senescent and pathogen- or reactive oxygen species-stressed cells. Stromules, tubular plastid extensions, are also observed under similar conditions. Coincident observations of PNC and stromules associate the two phenomena in facilitating retrograde signaling between chloroplasts and the nucleus. However, PNC incidence in non-stressed cells under normal growth and developmental conditions, when stromules are usually not observed, remains unclear. Using transgenic Arabidopsis expressing different organelle-targeted fluorescent proteins, we show that PNC is a dynamic subcellular phenomenon that continues in the absence of light and is not dependent on stromule formation. PNC is facilitated by tandem plastid–endoplasmic reticulum (ER) dynamics created through membrane contact sites between the two organelles. While PNC increases upon ER membrane expansion, some plastids may remain in the peri-nuclear region due to their localization in ER-lined nuclear indentions. Moreover, some PNC plastids may sporadically extend stromules into ER-lined nuclear grooves. Our findings strongly indicate that PNC is not an exclusive response to stress caused by pathogens, high light, or exogenous H2O2 treatment, and does not require stromule formation. However, morphological and behavioral alterations in ER and concomitant changes in tandem, plastid–ER dynamics play a major role in facilitating the phenomenon. [ABSTRACT FROM AUTHOR]

In sepsis, inflammation, and nutrient deficiencies endanger cellular homeostasis and survival. Autophagy is primarily a mechanism of cellular survival under fasting conditions. However, autophagy-dependent cell death, known as autophagic cell death, is proinflammatory and can exacerbate sepsis. Autophagy also regulates various types of non-inflammatory and inflammatory cell deaths. Non-inflammatory apoptosis tends to suppress inflammation, however, inflammatory necroptosis, pyroptosis, ferroptosis, and autophagic cell death lead to the release of inflammatory cytokines and damage-associated molecular patterns (DAMPs) and amplify inflammation. The selection of cell death mechanisms is complex and often involves a mixture of various styles. Similarly, protective autophagy and lethal autophagy may be triggered simultaneously in cells. How cells balance the regulatory mechanisms of these processes is an area of interest that is still under investigation. Therapies aimed at modulating autophagy are considered promising. Enhancing autophagy helps clear and recycle damaged organelles and reduce the burden of inflammatory processes while inhibiting excessive autophagy, which could prevent autophagic cell death. In this review, we introduce recent advances in research and the complex regulatory system of autophagy in sepsis. [ABSTRACT FROM AUTHOR]

Hydrogel-based tissue expansion combined with mass spectrometry (MS) offers an emerging spatial proteomics approach. Here, we present a filter-aided expansion proteomics (FAXP) strategy for spatial proteomics analysis of archived formalin-fixed paraffin-embedded (FFPE) specimens. Compared to our previous ProteomEx method, FAXP employed a customized tip device to enhance both the stability and throughput of sample preparation, thus guaranteeing the reproducibility and robustness of the workflow. FAXP achieved a 14.5-fold increase in volumetric resolution. It generated over 8 times higher peptide yield and a 255% rise in protein identifications while reducing sample preparation time by 50%. We also demonstrated the applicability of FAXP using human colorectal FFPE tissue samples. Furthermore, for the first time, we achieved bona fide single-subcellular proteomics under image guidance by integrating FAXP with laser capture microdissection. Hydrogel-based tissue expansion proteomics represents an emerging spatial proteomics approach. Here, the authors develop the filter-aided expansion proteomics (FAXP) strategy, enabling proteomic analysis of single cells and nuclei in formalin-fixed paraffin-embedded (FFPE) tissue sections. [ABSTRACT FROM AUTHOR]

Peroxisomes are organelles that are central to lipid metabolism and chemical detoxification. Despite advances in our understanding of peroxisome biogenesis, the mechanisms maintaining peroxisomal membrane proteins remain to be fully elucidated. We show here that mammalian FAF2/UBXD8, a membrane-associated cofactor of p97/VCP, maintains peroxisomal homeostasis by modulating the turnover of peroxisomal membrane proteins such as PMP70. In FAF2-deficient cells, PMP70 accumulation recruits the autophagy adaptor OPTN (Optineurin) to peroxisomes and promotes their autophagic clearance (pexophagy). Pexophagy is also induced by p97/VCP inhibition. FAF2 functions together with p97/VCP to negatively regulate pexophagy rather than as a factor for peroxisome biogenesis. Our results strongly suggest that p97/VCPFAF2-mediated extraction of ubiquitylated peroxisomal membrane proteins (e.g., PMP70) prevents peroxisomes from inducing nonessential autophagy under steady state conditions. These findings provide insight into molecular mechanisms underlying the regulation of peroxisomal integrity by p97/VCP and its associated cofactors. The mechanisms maintaining peroxisomal membrane proteins remain to be fully elucidated. Here, the authors report that p97/VCP and FAF2/UBXD8 modulate the turnover of peroxisomal membrane proteins to prevent autophagic degradation of peroxisomes. [ABSTRACT FROM AUTHOR]

The initiation of microtubule formation is facilitated by γ-tubulin and γ-Tubulin Ring Complex (γ-TuRC) in various microtubule-organizing centers (MTOCs). While the heterogeneity of tissue-specific MTOCs and γ-TuRC in Drosophila testis has been described, their molecular composition and physiological significance are poorly understood. We investigated the testis-specific distribution and biochemical interaction of the canonical γ-TuRC proteins Grip163 and Grip84. We found that while Grip163 is present on the centrosome and basal body, Grip84 localizes to the centrosome and Golgi in spermatocytes and colocalizes with the testis-specific γ-Tubulin complexes (t-γ-TuC) at the basal body, apical nuclear tip, and near the elongated mitochondria after meiosis. We also showed the apical nuclear tip localization of some γ-TuRC interacting partners and proved their binding to t-γ-TuC proteins. These results highlight and prove the importance of the different γ-TuRCs in organizing the diverse MTOCs present during the extensive rearrangement of cell organelles during the spermatogenesis of Drosophila. The heterogeneous distribution of various γ-tubulin binding complexes contributes to the formation of diverse microtubule-organizing centers and the comprehensive rearrangement of cellular organelles during spermatogenesis in Drosophila. [ABSTRACT FROM AUTHOR]

Organelles in cells are appropriately positioned, despite crowding in the cytoplasm. However, our understanding of the force required to move large organelles, such as the nucleus, inside the cytoplasm is limited, in part owing to a lack of accurate methods for measurement. We devised a method to apply forces to the nucleus of living Caenorhabditis elegans embryos to measure the force generated inside the cell. We used a centrifuge polarizing microscope to apply centrifugal force and orientation-independent differential interference contrast microscopy to characterize the mass density of the nucleus and cytoplasm. The cellular forces moving the nucleus toward the cell center increased linearly at ~12 pN/μm depending on the distance from the center. The frictional coefficient was ~980 pN s/μm. The measured values were smaller than the previously reported estimates for sea urchin embryos. The forces were consistent with the centrosome-organelle mutual pulling model for nuclear centration. The frictional coefficient was reduced when microtubules were shorter or detached from nuclei in mutant embryos, demonstrating the contribution of astral microtubules. Finally, the frictional coefficient was higher than a theoretical estimate, indicating the contribution of uncharacterized properties of the cytoplasm. [ABSTRACT FROM AUTHOR]

The Golgi apparatus is the central hub of the cellular endocrine pathway and plays a crucial role in processing, transporting, and sorting proteins and lipids. Simultaneously, it is a highly dynamic organelle susceptible to degradation or fragmentation under various physiological or pathological conditions, potentially contributing to the development of numerous human diseases. Autophagy serves as a vital pathway for eukaryotes to manage intracellular and extracellular stress and maintain homeostasis by targeting damaged or redundant organelles for removal. Recent research has revealed that autophagy mechanisms can specifically degrade Golgi components, known as Golgiphagy. This review summarizes recent findings on Golgiphagy while also addressing unanswered questions regarding its mechanisms and regulation, aiming to advance our understanding of the role of Golgiphagy in human disease. [ABSTRACT FROM AUTHOR]

A wave of new research on compartments in the cell called 'membraneless organelles' suggests that they are created through a process of phase separation, an idea from the early days of cell biology that has been revived. However, some question the biological relevance. Cyrus Martin explores the history and current debate. A wave of new research on structures in the cell called 'membraneless organelles' claims that they are created through a process of phase separation, an idea that may fundamentally be at odds with more classical models based on the study of complexes at smaller scales. [ABSTRACT FROM AUTHOR]

The intermitochondrial cement (IMC) is a prominent germ granule that locates among clustered mitochondria in mammalian germ cells. Serving as a key platform for Piwi-interacting RNA (piRNA) biogenesis; however, how the IMC assembles among mitochondria remains elusive. Here, we identify that Tudor domain-containing 1 (TDRD1) triggers IMC assembly via phase separation. TDRD1 phase separation is driven by the cooperation of its tetramerized coiled-coil domain and dimethylarginine-binding Tudor domains but is independent of its intrinsically disordered region. TDRD1 is recruited to mitochondria by MILI and sequentially enhances mitochondrial clustering and triggers IMC assembly via phase separation to promote piRNA processing. TDRD1 phase separation deficiency in mice disrupts IMC assembly and piRNA biogenesis, leading to transposon de-repression and spermatogenic arrest. Moreover, TDRD1 phase separation is conserved in vertebrates but not in invertebrates. Collectively, our findings demonstrate a role of phase separation in germ granule formation and establish a link between membrane-bound organelles and membrane-less organelles. [Display omitted] • TDRD1 undergoes phase separation via oligomerization of coiled-coil domain • Tudor domains facilitate TDRD1 phase separation by recognizing sDMA • TDRD1 phase separation deficiency disrupts IMC assembly and piRNA biogenesis in mice • TDRD1 phase separation is conserved in vertebrates but not in invertebrates Gao et al. address the mechanism governing the assembly of mitochondrial-associated germ granules (IMCs) in mammalian germ cells. The IMC component TDRD1 undergoes phase separation to trigger IMC assembly, which is essential for piRNA biogenesis, transposon silencing, and male fertility in mice. [ABSTRACT FROM AUTHOR]

Communication between subcellular organelles is crucial for a synchronized cellular response which drives the search for chemical tools to simultaneously visualize dual organelles to unveil these dynamic interactions. A polarity‐sensitive dual organelle targeting dioxaborine derivative, namely DOBEL, which stains lipid droplets (LDs) and endoplasmic reticulum (ER) simultaneously is introduced. This report is the first to demonstrate how the intrinsic difference in micropolarity drives the visualization of LDs in the green channel while ER in the red channel involves a single probe. The in situ emission spectra inside these organelles allow polarity quantification, further leading to deciphering the unique microenvironments in different cell lines. Exploiting ratiometric fluorescence imaging revealed how the micropolarity inside both LDs and ER alters during Ferroptosis. Altogether, DOBEL can be used as a superior imaging tool for monitoring LD‐ER interaction during regular status and ferroptosis‐related diseases in living cells. [ABSTRACT FROM AUTHOR]

Unambiguous targeting of cellular structures for in situ cryo-electron microscopy in the heterogeneous, dense and compacted environment of the cytoplasm remains challenging. Here, we have developed a cryogenic correlative light and electron microscopy (cryo-CLEM) workflow that utilizes thin cells grown on a mechanically defined substratum for rapid analysis of organelles and macromolecular complexes by cryo-electron tomography (cryo-ET). We coupled these advancements with optogenetics to redistribute perinuclearlocalised organelles to the cell periphery, allowing visualisation of organelles that would otherwise be positioned in cellular regions too thick for cryo-ET. This reliable and robust workflowallows for fast in situ analyses without the requirement for cryo-focused ion beam milling. Using this protocol, cells can be frozen, imaged by cryo-fluorescence microscopy and be ready for batch cryo-ET within a day. [ABSTRACT FROM AUTHOR]

Eukaryotic cells are compartmentalized into membrane-bound organelles that must coordinate their responses to stimuli. One way that organelles communicate is via membrane contact sites (MCSs), sites of close apposition between organelles used for the exchange of ions, lipids and information. In this Cell Science at a Glance article and the accompanying poster, we describe an explosion of new methods that have led to exciting progress in this area and discuss key examples of how these methods have advanced our understanding of MCSs. We discuss how diffraction-limited and super-resolution fluorescence imaging approaches have provided important insight into the biology of interorganelle communication.We also describe how the development of multiple proximity-based methods has enabled the detection ofMCSswith high accuracy and precision. Finally, we assess howrecent advances in electronmicroscopy (EM), considered the gold standard for detecting MCSs, have allowed the visualization of MCSs and associated proteins in 3D at ever greater resolution. [ABSTRACT FROM AUTHOR]

Lysosomes, crucial cellular organelles, undergo bidirectional transport along microtubules, mediated by motor proteins such as cytoplasmic dynein-1 (dynein) and various kinesins. While the kinesin-3 family member KIF1C is established in mediating anterograde vesicle transport, its role in lysosomal transport remains unclear. Our study reveals that KIF1C unexpectedly supports the retrograde transport of lysosomes, driven by dynein, and contributes to their perinuclear localization. Notably, while KIF1C facilitates this perinuclear positioning, its motor activity is not required and, instead, exerts an inhibitory effect on this process. Mechanistically, KIF1C facilitates this process by interacting with the dynein-activating adaptor Hook3, which associates with the lysosome-anchored protein RUFY3. This regulatory mechanism is critical for the efficient degradation of cargo in autophagic and endocytic pathways. Our findings identify an unconventional, non-motor role for KIF1C in activating dynein-driven lysosomal transport, expanding our understanding of its functional diversity in cellular trafficking. KIF1C mediates dynein-driven retrograde transport of lysosomes by interacting with Hook3 and RUFY3, independent of its motor activity. This ensures perinuclear lysosomal positioning, essential for efficient autophagic and endocytic degradation. [ABSTRACT FROM AUTHOR]

As most traditional drugs used to treat central nervous system (CNS) diseases have a single therapeutic target, many of them cannot treat complex diseases or diseases whose mechanism is unknown and cannot effectively reverse the root changes underlying CNS diseases. This raises the question of whether multiple functional components are involved in the complex pathological processes of CNS diseases. Organelles are the core functional units of cells, and the replacement of damaged organelles with healthy organelles allows the multitargeted and integrated modulation of cellular functions. The development of therapies that target independent functional units in the cell, specifically, organelle-based therapies, is rapidly progressing. This article comprehensively discusses the pathogenesis of mitochondrial homeostasis disorders, which involve mitochondria, one of the most important organelles in CNS diseases, and the machanisms of mitochondrion-based therapies, as well as current preclinical and clinical studies on the efficacy of therapies targeting mitochondrial to treat CNS diseases, to provide evidence for use of organelle-based treatment strategies in the future. [ABSTRACT FROM AUTHOR]

Mitochondria are essential organelles within cells, playing various roles in numerous cellular processes, including differentiation, growth, apoptosis, energy conversion, metabolism, and cellular immunity. The phenotypic variation of mitochondria is specific to different tissues and cell types, resulting in significant differences in their function, morphology, and molecular characteristics. Asthma is a chronic, complex, and heterogeneous airway disease influenced by external factors such as environmental pollutants and allergen exposure, as well as internal factors at the tissue, cellular, and genetic levels, including lung and airway structural cells, immune cells, granulocytes, and mast cells. Therefore, a comprehensive understanding of the specific responses of mitochondria to various external environmental stimuli and internal changes are crucial for elucidating the pathogenesis of asthma. Previous research on mitochondrial-targeted therapy for asthma has primarily focused on antioxidants. Consequently, it is necessary to summarize the multifaceted roles of mitochondria in the pathogenesis of asthma to discover additional strategies targeting mitochondria in this context. In this review, our goal is to describe the changes in mitochondrial function in response to various exposure factors across different cell types and other relevant factors in the context of asthma, utilizing a new mitochondrial terminology framework that encompasses cell-dependent mitochondrial characteristics, molecular features, mitochondrial activity, function, and behavior. [ABSTRACT FROM AUTHOR]

An extensive network of chaperones and folding factors is responsible for maintaining a functional proteome, which is the basis for cellular life. The underlying proteostatic mechanisms are not isolated within organelles, rather they are connected over organellar borders via signalling processes or direct association via contact sites. This review aims to provide a conceptual understanding of proteostatic mechanisms across organelle borders, not focussing on individual organelles. This discussion highlights the precision of these finely tuned systems, emphasising the complicated balance between cellular protection and adaptation to stress. In this review, we discuss widely accepted aspects while shedding light on newly discovered perspectives. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) and lysosomes are vital organelles that play crucial roles in various physiological and pathological processes. However, simultaneous two-color visualization of these two organelles using a single probe for cell homeostasis monitoring remains a challenge due to the lack of rational design strategies. To address this issue, we have developed an aggregation-induced emission (AIE) fluorescent probe named TPE-NDI-Mor with an electron donor (D)–acceptor (A) structure, which can stain both LDs and lysosomes with high selectivity through green and red fluorescence imaging, respectively. A detailed mechanism study revealed that TPE-NDI-Mor, with a twisted intramolecular charge transfer (TICT) effect, shows a high affinity for a polar microenvironment. Additionally, the probe also demonstrates good stability, high anti-interference performance and a large Stokes shift, making it suitable for visualizing cell homeostasis and further disease diagnosis by tracking the dynamic changes of LDs and lysosomes. [ABSTRACT FROM AUTHOR]

Cells have used compartmentalization to implement complex biological processes involving thousands of enzyme cascade reactions. Enzymes are spatially organized into the cellular compartments to carry out specific and efficient reactions in a spatiotemporally controlled manner. These compartments are divided into membrane‐bound and membraneless organelles. Mimicking such cellular compartment systems has been a challenge for years. A variety of artificial scaffolds, including liposomes, polymersomes, proteins, nucleic acids, or hybrid materials have been used to construct artificial membrane‐bound or membraneless compartments. These artificial compartments may have great potential for applications in biosynthesis, drug delivery, diagnosis and therapeutics, among others. This review first summarizes the typical examples of cellular compartments. In particular, the recent studies on cellular membraneless organelles (biomolecular condensates) are reviewed. We then summarize the recent advances in the construction of artificial compartments using engineered platforms. Finally, we provide our insights into the construction of biomimetic systems and the applications of these systems. This review article provides a timely summary of the relevant perspectives for the future development of artificial compartments, the building blocks for the construction of artificial organelles or cells. [ABSTRACT FROM AUTHOR]

Introduction: The University of Wisconsin (UW) and histidine-tryptophan-ketoglutarate (HTK) are the most popular organ-preservative solutions. Ultrastructure of organelles reflects the functionality of cells, but less is understood about ultrastructural changes of hepatocytes after machine perfusion (MP) with HTK, than with UW solution. Methods: We evaluated the ultrastructure of hepatocytes preserved in HTK solution during hypothermic (4°C) and midthermic (22°C) MP (HMP and MMP, respectively) temperatures using osmium maceration scanning electron microscopy. Results: The functional ultrastructure of mitochondria in hepatocytes was maintained immediately after HMP and MMP. After 2 h in a porcine isolated liver reperfusion model (IRM) that simulates transplanted liver grafts, mitochondrial cristae became denser and some large vacuoles that we assumed were autophagosomes were detected in hepatocytes after HMP. Autophagy functions in the suppression of reactive oxygen generation and subsequent apoptosis, and these findings indicated that HMP is more effective than MMP when livers are preserved in HTK solution. Conclusion: The present findings contradict the previous findings of the UW solution that MMP is more effective than HMP. Thus, various combinations of conditions for MP should be carefully optimized before changing preservatives. [ABSTRACT FROM AUTHOR]

GABARAP is a member of the ATG8 family of ubiquitin-like autophagy related proteins. It was initially discovered as a facilitator of GABA-A receptor translocation to the plasma membrane and has since been shown to promote the intracellular transport of a variety of other proteins under non-autophagic conditions. We and others have shown that GABARAP interacts with the Type II phosphatidylinositol 4-kinase, PI4K2A, and that this interaction is important for autophagosome-lysosome fusion. Here, we identify a 7-amino acid segment within the PI4K2A catalytic domain that contains the GABARAP interaction motif (GIM). This segment resides in an exposed loop that is not conserved in the other mammalian Type II PI 4-kinase, PI4K2B, explaining the specificity of GABARAP binding to the PI4K2A isoform. Mutation of the PI4K2A GIM inhibits GABARAP binding and PI4K2A-mediated recruitment of cytosolic GABARAP to subcellular organelles. We further show that GABARAP binds to mono-phosphorylated phosphoinositides, PI3P, PI4P, and PI5P, raising the possibility that these lipids contribute to the binding energies that drive GABARAP-protein interactions on membranes. [ABSTRACT FROM AUTHOR]

Phospholipid homeostasis comprises an intricate network of communication between mitochondria, peroxisomes, the endoplasmic reticulum, and the Golgi apparatus. Disruptions to the function of one type of organelle triggers cell-wide changes in the structures and functions of other organelles. Volume electron microscopy (vEM) is an emerging technology that allows 3D visualization of organelle morphology and communication changes upon disruption of phospholipid homeostasis. Mathematical descriptors of organelle morphology and interorganelle contacts can increase the depth of data obtained from vEM datasets and standardize analyses across the field. Many organelle diseases share common pathological features, and organelle communication breakdown has been identified in many disease states such as Parkinson's disease. The presence of membrane-bound organelles with specific functions is one of the main hallmarks of eukaryotic cells. Organelle membranes are composed of specific lipids that govern their function and interorganelle communication. Discoveries in cell biology using imaging and omic technologies have revealed the mechanisms that drive membrane remodeling, organelle contact sites, and metabolite exchange. The interplay between multiple organelles and their interdependence is emerging as the next frontier for discovery using 3D reconstruction of volume electron microscopy (vEM) datasets. We discuss recent findings on the links between organelles that underlie common functions and cellular pathways. Specifically, we focus on the metabolism of ether glycerophospholipids that mediate organelle dynamics and their communication with each other, and the new imaging techniques that are powering these discoveries. [ABSTRACT FROM AUTHOR]

This review highlights the complexity of renal epithelial cell membrane architectures and organelles through careful review of ultrastructural and physiological studies published over the past several decades. We also showcase the vital roles played by the actin cytoskeleton and actin-associated myosin motor proteins in regulating cell type-specific physiological functions within the cells of the renal epithelium. The purpose of this review is to provide a fresh conceptual framework to explain the structure-function relationships that exist between the actin cytoskeleton, organelle structure, and cargo transport within the mammalian kidney. With recent advances in technologies to visualize the actin cytoskeleton and associated proteins within intact kidneys, it has become increasingly imperative to reimagine the functional roles of these proteins in situ to provide a rationale for their unique, cell type-specific functions that are necessary to establish and maintain complex physiological processes. [ABSTRACT FROM AUTHOR]

The neuronal endoplasmic reticulum (ER) consists of a dynamic, tubular network that extends all the way from the soma into dendrites, axons, and synapses. This morphology gives rise to an enormous membrane surface area that, through the presence of tethering proteins, lipid transfer proteins, and ion channels, plays critical roles in local calcium regulation, membrane dynamics, and the supply of ions and lipids to other organelles. Here, we summarize recent advances that highlight the various roles of the neuronal ER in axonal growth, repair, and presynaptic function. We review the variety of contact sites between the ER and other axonal organelles and describe their influence on neurodevelopment and neurotransmission. [ABSTRACT FROM AUTHOR]

Super‐resolution imaging techniques, such as structured illumination microscopy (SIM), have enabled researchers to obtain nanoscale organelle‐level outputs in living systems, but they impose additional stringent requirements on fluorescence probes. However, high‐performance, custom‐designed SIM probes that can explain underlying biological processes remain unavailable. Herein, a customizable engineering toolkit is developed for the facile assembly of SIM probes suitable for subcellular component detection. This toolkit is used to customize a fluorescent molecule, CPC (coumarin–phenylhydrazine–carboxyl), capable of simultaneously monitoring peroxynitrite (ONOO−) and polarity distribution in mitochondria and lipid droplets (LDs), respectively, through functional ON–OFF mechanisms. The customized CPC molecule demonstrated excellent imaging capabilities under SIM, enabled the successful localization of multiple organelles, and reliably tracked the distribution of different components, thus facilitating the study of the interplay between organelles. Using CPC, the physical transition of intracellular LDs is demonstrated from heterogeneity to homogeneity. This was specifically observed during ferroptosis where the polarity of the LDs increased and their morphology became more contracted. Furthermore, the loss of LDs functionality could not counteract the accumulation of ONOO− within the mitochondria, leading to the decoupling of mitochondrial LDs during ferroptosis. These results confirmed the potential mechanism of LDs dysfunction and decoupling triggered via cumulative mitochondrial oxidative stress during ferroptosis. To summarize, this toolkit will be a powerful tool for examining subtle variations among components during the interplay between different organelles, thus offering novel avenues for understanding and treating related diseases. [ABSTRACT FROM AUTHOR]

Lamellar bodies (LBs) are tissue-specific lysosome-related organelles in type II alveolar cells that are the main site for the synthesis, storage, and secretion of pulmonary surfactants. Defects in pulmonary surfactants lead to a variety of respiratory and immune-related disorders. LB biogenesis is closely related to their function, but the underlying regulatory mechanism is largely unclear. Here, we found that deficiency of HPS6, a subunit of BLOC-2 (biogenesis of lysosome-related organelles complex-2), led to a reduction of the steady-state concentration of vacuolar-type H+-ATPase and an increase in the luminal pH of LBs. Furthermore, we observed increased LB size, accumulated surfactant proteins, and altered lipid profiling of lung tissue and BAL fluid due to HPS6 deficiency. These findings suggest that HPS6 regulates the distribution of vacuolar-type H+-ATPase on LBs to maintain its luminal acidity and LB homeostasis. This may provide new insights into the LB pathology. [ABSTRACT FROM AUTHOR]

Background: Eukaryotic cells are highly compartmentalized by a variety of organelles that carry out specific cellular processes. The position of these organelles within the cell is elaborately regulated and vital for their function. For instance, the position of lysosomes relative to the nucleus controls their degradative capacity and is altered in pathophysiological conditions. The molecular components orchestrating the precise localization of organelles remain incompletely understood. A confounding factor in these studies is the fact that organelle positioning is surprisingly non-trivial to address e.g., perturbations that affect the localization of organelles often lead to secondary phenotypes such as changes in cell or organelle size. These phenotypes could potentially mask effects or lead to the identification of false positive hits. To uncover and test potential molecular components at scale, accurate and easy-to-use analysis tools are required that allow robust measurements of organelle positioning. Results: Here, we present an analysis workflow for the faithful, robust, and quantitative analysis of organelle positioning phenotypes. Our workflow consists of an easy-to-use Fiji plugin and an R Shiny App. These tools enable users without background in image or data analysis to (1) segment single cells and nuclei and to detect organelles, (2) to measure cell size and the distance between detected organelles and the nucleus, (3) to measure intensities in the organelle channel plus one additional channel, (4) to measure radial intensity profiles of organellar markers, and (5) to plot the results in informative graphs. Using simulated data and immunofluorescent images of cells in which the function of known factors for lysosome positioning has been perturbed, we show that the workflow is robust against common problems for the accurate assessment of organelle positioning such as changes of cell shape and size, organelle size and background. Conclusions: OrgaMapper is a versatile, robust, and easy-to-use automated image analysis workflow that can be utilized in microscopy-based hypothesis testing and screens. It effectively allows for the mapping of the intracellular space and enables the discovery of novel regulators of organelle positioning. [ABSTRACT FROM AUTHOR]

We investigated whether the elimination of two major enzymes responsible for triacylglycerol synthesis altered the structure and physical state of organelle membranes under mild heat shock conditions in the fission yeast, Schizosaccharomyces pombe. Our study revealed that key intracellular membrane structures, lipid droplets, vacuoles, the mitochondrial network, and the cortical endoplasmic reticulum were all affected in mutant fission yeast cells under mild heat shock but not under normal growth conditions. We also obtained direct evidence that triacylglycerol-deficient cells were less capable than wild-type cells of adjusting their membrane physical properties during thermal stress. The production of thermoprotective molecules, such as HSP16 and trehalose, was reduced in the mutant strain. These findings suggest that an intact system of triacylglycerol metabolism significantly contributes to membrane protection during heat stress. [ABSTRACT FROM AUTHOR]

Organelles have unique structures and molecular compositions for their functions and have been classified accordingly. However, many organelles are heterogeneous and in the process of maturation and differentiation. Because traditional methods have a limited number of parameters and spatial resolution, they struggle to capture the heterogeneous landscapes of organelles. Here, we present a method for multiparametric particle-based analysis of organelles. After disrupting cells, fluorescence microscopy images of organelle particles labeled with 6 to 8 different organelle markers were obtained, and their multidimensional data were represented in two-dimensional uniform manifold approximation and projection (UMAP) spaces. This method enabled visualization of landscapes of 7 major organelles as well as the transitional states of endocytic organelles directed to the recycling and degradation pathways. Furthermore, endoplasmic reticulum–mitochondria contact sites were detected in these maps. Our proposed method successfully detects a wide array of organelles simultaneously, enabling the analysis of heterogeneous organelle landscapes. Organelles have unique structures and molecular composition, but can form heterogeneous populations and change substantially during maturation and differentiation, and traditional methods have failed to reflect these variations. In this study, the authors introduce a multi-parametric, fluorescence spectroscopy method that allows simultaneous visualization of a wide array of organelles in different maturation states. [ABSTRACT FROM AUTHOR]

The evolution of intracellular organelles by endosymbiosis is considered rare. Two recent studies suggest that endosymbioses between nitrogen-fixing bacteria and eukaryotic algae are approaching levels of integration comparable to cellular organelles, helping to solve the problem of oceanic nitrogen limitation. [ABSTRACT FROM AUTHOR]

Integration of living cells with extrinsic functional entities gives rise to bioaugmented nanobiohybrids, which hold tremendous potential across diverse fields such as cell therapy, biocatalysis, and cell robotics. This study presents a biocompatible method for incorporating multilayered functional liposomes onto the cell surface, creating extracellular artificial organelles or exorganelles. The introduction of various extrinsic functionalities to cells is achieved without comprising their viabilities. The integration of extrinsic enzymatic reactions is exemplified through the cascade reaction involving glucose oxidase and horseradish peroxidase. Furthermore, our protocol offers the design flexibility to customize liposome compositions, thereby providing effective cell modification. The versatility of the liposome‐based exorganelle approach establishes an advanced chemical tool, empowering cells with novel functionalities that surpass or are complementary to their innate capabilities. [ABSTRACT FROM AUTHOR]

Oxidative phosphorylation (OXPHOS) in the mitochondrial inner membrane is a therapeutic target in many diseases. Neural stem cells (NSCs) show progress in improving mitochondrial dysfunction in the central nervous system (CNS). However, translating neural stem cell-based therapies to the clinic is challenged by uncontrollable biological variability or heterogeneity, hindering uniform clinical safety and efficacy evaluations. We propose a systematic top-down design based on membrane self-assembly to develop neural stem cell-derived oxidative phosphorylating artificial organelles (SAOs) for targeting the central nervous system as an alternative to NSCs. We construct human conditionally immortal clone neural stem cells (iNSCs) as parent cells and use a streamlined closed operation system to prepare neural stem cell-derived highly homogenous oxidative phosphorylating artificial organelles. These artificial organelles act as biomimetic organelles to mimic respiration chain function and perform oxidative phosphorylation, thus improving ATP synthesis deficiency and rectifying excessive mitochondrial reactive oxygen species production. Conclusively, we provide a framework for a generalizable manufacturing procedure that opens promising prospects for disease treatment. Regulating oxidative phosphorylation and restoring redox homeostasis are crucial in neurological disorders. Here, the authors develop a top-down membrane self-assembly strategy to develop stem cell-derived artificial organelles (SAOs) that mimic mitochondrial oxidative phosphorylation without the risks associated with stem cell therapy. [ABSTRACT FROM AUTHOR]

Contact sites between lipid droplets and other organelles are essential for cellular lipid and energy homeostasis. Detection of these contact sites at nanometer scale over time in living cells is challenging. Here, we developed a tool kit for detecting contact sites based on Fluorogen-Activated Bimolecular complementation at CONtact sites, FABCON, using a reversible, low affinity split fluorescent protein, splitFAST. FABCON labels contact sites with minimal perturbation to organelle interaction. Via FABCON, we quantitatively demonstrated that endoplasmic reticulum (ER)- and mitochondria (mito)-lipid droplet contact sites are dynamic foci in distinct metabolic conditions, such as during lipid droplet biogenesis and consumption. An automated analysis pipeline further classified individual contact sites into distinct subgroups based on size, likely reflecting differential regulation and function. Moreover, FABCON is generalizable to visualize a repertoire of organelle contact sites including ER-mito. Altogether, FABCON reveals insights into the dynamic regulation of lipid droplet-organelle contact sites and generates new hypotheses for further mechanistical interrogation during metabolic switch. [ABSTRACT FROM AUTHOR]

Background: Lipid droplet (LD) is a metabolically active organelle, which changes dynamically with the metabolic state and energy requirements of cells. Proteins that either insert into the LD phospholipid monolayer or are present in the cytoplasm, playing a crucial role in lipid homeostasis and signaling regulation, are known as LD-associated proteins. Methods: The keywords "lipid droplets" and "metabolic diseases" were used to obtain literature on LD metabolism and pathological mechanism. After searching databases including Scopus, OVID, Web of Science, and PubMed from 2013 to 2024 using terms like "lipid droplets", "lipid droplet-associated proteins", "fatty liver disease", "diabetes", "diabetic kidney disease", "obesity", "atherosclerosis", "hyperlipidemia", "natural drug monomers" and "natural compounds", the most common natural compounds were identified in about 954 articles. Eventually, a total of 91 studies of 10 natural compounds reporting in vitro or in vivo studies were refined and summarized. Results: The most frequently used natural compounds include Berberine, Mangostin, Capsaicin, Caffeine, Genistein, Epigallocatechin-3-gallate, Chlorogenic acid, Betaine, Ginsenoside, Resveratrol. These natural compounds interact with LD-associated proteins and help ameliorate abnormal LDs in various metabolic diseases. Conclusion: Natural compounds involved in the regulation of LDs and LD-associated proteins hold promise for treating metabolic diseases. Further research into these interactions may lead to new therapeutic applications. [ABSTRACT FROM AUTHOR]

The species complex Mesodinium rubrum / major, common red tide-forming ciliates, has been intensively studied with regards to its ecological roles in global marine ecosystems and the evolutionary aspects of its "stolen" organelles (kleptoplasty and karyoklepty). Nonetheless, the taxonomy of the species within the complex remains unclear. A new marine Mesodinium species isolated from Gomso Bay, Korea, was cultivated under mixotrophic conditions by providing Teleaulax amphioxeia, a red cryptomonad, as prey. Cells of the new isolate consisted of two portions separated by two types of polykinetids. The number of polykinetid associated with the equatorial ciliary belt was approximately 38, and each consisting of two rows of up to 18 alternating kinetosomes each. There was an equal number of cirral polykinetids, each consisting of 16 kinetosomes organized into four longitudinal rows having five, five, four, and two kinetosomes, respectively (in anti-clockwise direction). The two kinds of kinetids and their associated microtubules and fibers were structurally similar to those of M. rubrum from Denmark. However, the Korean Mesodinium species was characterized by its broad posterior portion, 20-22 tentacles, and a cytopharyngeal annulus. Molecular phylogeny based on internal transcribed spacer sequences placed the Korean isolate in clade B of the M. rubrum / major species complex, rather than in clade F representing the neotype of M. rubrum. Based on morphological, ultrastructural, and molecular data, we propose the Korean strain as a new marine Mesodinium species, M. annulatum. [ABSTRACT FROM AUTHOR]