Search

Twelve new and four known alkaloids including five different structural scaffolds were isolated from the sponge

Mechanistic target of rapamycin mTOR complex 1 (mTORC1) plays a key role in the integration of various environmental signals to regulate cell growth and metabolism. mTORC1 is recruited to the lysosome where it is activated by its interaction with GTP-bound Rheb GTPase. However, the regulatory mechanism of Rheb activity remains largely unknown. Here, we show that ubiquitination governs the nucleotide-bound status of Rheb. Lysosome-anchored E3 ligase RNF152 catalyzes Rheb ubiquitination and promotes its binding to the TSC complex. EGF enhances the deubiquitination of Rheb through AKT-dependent USP4 phosphorylation, leading to the release of Rheb from the TSC complex. Functionally, ubiquitination of Rheb is linked to mTORC1-mediated signaling and consequently regulates tumor growth. Thus, we propose a mechanistic model whereby Rheb–mediated mTORC1 activation is dictated by a dynamic opposing act between Rheb ubiquitination and deubiquitination that are catalyzed by RNF152 and USP4 respectively.

Background: Excessive salt intake is considered as an important risk factor for cognitive impairment, which might be the consequence of imbalanced intestinal homeostasis. Objective: To investigate the effects of dietary salt on the gut microbiota and cognitive performance and the underlying mechanisms. Methods: Adult female C57BL/6 mice were maintained on either normal chow (control group, CON) or sodium-rich chow containing 8% NaCl (high-salt diet, HSD) for 8 weeks. Spatial learning and memory ability, short-chain fatty acids (SCFAs) concentrations, gut bacterial flora composition, blood-brain barrier permeability, and proinflammatory cytokine levels and apoptosis in the brain were evaluated. Results: The mice fed a HSD for 8 weeks displayed impaired learning and memory abilities. HSD significantly reduced the proportions of Bacteroidetes (S24-7 and Alloprevotella) and Proteobacteria and increased that of Firmicutes (Lachnospiraceae and Ruminococcaceae). SCFA concentrations decreased in the absolute concentrations of acetate, propionate, and butyrate in the fecal samples from the HSD-fed mice. The HSD induced both BBB dysfunction and microglial activation in the mouse brain, and increased the IL-1β, IL-6, and TNF-α expression levels in the cortex. More importantly, the degree of apoptosis was higher in the cortex and hippocampus region of mice fed the HSD, and this effect was accompanied by significantly higher expression of cleaved caspase-3, caspase-3, and caspase-1. Conclusion: The HSD directly causes cognitive dysfunction in mice by eliciting an inflammatory environment and triggering apoptosis in the brain, and these effects are accompanied by gut dysbiosis, particularly reduced SCFA production.

CD4+ T cells are the central element of the adaptive immune responses and protect the body from a variety of pathogens. Starting from naive cells, CD4+ T cells can differentiate into various effector cell subsets with specialized functions including T helper (Th) 1, Th2, Th17, regulatory T (Treg) and T follicular helper (Tfh) cells. Among them, Tregs and Th17 cells show a strong plasticity allowing the functional adaptation to various physiological and pathological environments during immune responses. Although they are derived from the same precursor cells and their differentiation pathways are interrelated, the terminally differentiated cells have totally opposite functions. Studies have shown that Tregs and Th17 cells have rather complex interplays in viral infection: Th17 cells may contribute to immune activation and disease progression while Tregs may inhibit this process and play a key role in the maintenance of immune homoeostasis, possibly at the cost of compromised viral control. In this review, we take respiratory syncytial virus (RSV), hepatitis B virus (HBV)/hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections as examples to discuss these interplays and their impacts on disease progression in viral infection.

Given the growing evidence of a link between gut microbiota (GM) dysbiosis and multiple sclerosis (MS), fecal microbiota transplantation (FMT), aimed at rebuilding GM, has been proposed as a new therapeutic approach to MS treatment. To evaluate the viability of FMT for MS treatment and its impact on MS pathology, we tested FMT in mice with experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We provide evidence that FMT can rectify altered GM to some extent with a therapeutic effect on EAE. We also found that FMT led to reduced activation of microglia and astrocytes and conferred protection on the blood-brain barrier (BBB), myelin, and axons in EAE. Taken together, our data suggest that FMT, as a GM-based therapy, has the potential to be an effective treatment for MS.

Five new pyrazin-2(1H)-one derivatives, ochramides A-D (1-4) and ochralate A (5), as well as three known analogues (6-8) were isolated from the fermentation broth of the marine coral-derived halotolerant Aspergillus ochraceus LCJ11-102 in a nutrient-limited medium containing 10% NaI. Their chemical structures were determined by analyzing NMR and X-ray diffraction data. Compounds 2, 5 and 6 showed antimicrobial activities against Enterobacter aerogenes with the MIC values of 40.0, 18.9, and 20.1 μM, respectively.

Cardiotoxicity limits the clinical applications of doxorubicin (Dox), which mechanism might be excess generation of intracellular ROS. Quercetin (Que) is a flavonoid that possesses anti-oxidative activities, exerts myocardial protection. We hypothesized that the cardioprotection against Dox injury of Que involved 14-3-3γ, and mitochondria. To investigate the hypothesis, we treated primary cardiomyocytes with Dox and determined the effects of Que pretreatment with or without 14-3-3γ knockdown. We analyzed various cellular and molecular indexes. Our data showed that Que attenuated Dox-induced toxicity in cardiomyocytes by upregulating 14-3-3γ expression. Que pretreatment increased cell viability, SOD, catalase, and GPx activities, GSH levels, MMP and the GSH/GSSG ratio; decreased LDH and caspase-3 activities, MDA and ROS levels, mPTP opening and the percentage of apoptotic cells. However, Que's cardioprotection were attenuated by knocking down 14-3-3γ expression using pAD/14-3-3γ-shRNA. In conclusion, Que protects cardiomyocytes against Dox injury by suppressing oxidative stress and improving mitochondrial function via 14-3-3γ.

Understanding the mechanisms of early cardiac fate determination may lead to better approaches in promoting heart regeneration. We used a mesoderm posterior 1 (Mesp1)-Cre/Rosa26-EYFP reporter system to identify microRNAs (miRNAs) enriched in early cardiac progenitor cells. Most of these miRNA genes bear MESP1-binding sites and active histone signatures. In a calcium transient-based screening assay, we identified miRNAs that may promote the cardiomyocyte program. An X-chromosome miRNA cluster, miR-322/-503, is the most enriched in the Mesp1 lineage and is the most potent in the screening assay. It is specifically expressed in the looping heart. Ectopic miR-322/-503 mimicking the endogenous temporal patterns specifically drives a cardiomyocyte program while inhibiting neural lineages, likely by targeting the RNA-binding protein CUG-binding protein Elav-like family member 1 (Celf1). Thus, early miRNAs in lineage-committed cells may play powerful roles in cell-fate determination by cross-suppressing other lineages. miRNAs identified in this study, especially miR-322/-503, are potent regulators of early cardiac fate.

Myotonic dystrophy 1 (DM1) is a common form of muscular dystrophy. Although several animal models have been established for DM1, myoblast cell models are still important because they offer an efficient cellular alternative for studying cellular and molecular events. Though C2C12 myoblast cells have been widely used to study myogenesis, resistance to gene transfection, or viral transduction, hinders research in C2C12 cells. Here, we describe an optimized protocol that includes daily maintenance, transfection and transduction procedures to introduce genes into C2C12 myoblasts and the induction of myocyte differentiation. Collectively, these procedures enable best transfection/transduction efficiencies, as well as consistent differentiation outcomes. The protocol described in establishing DM1 myoblast cell models would benefit the study of myotonic dystrophy, as well as other muscular diseases.

Summary YAP, a key effector of Hippo pathway, is activated by its translocation from cytoplasm to nucleus to regulate gene expression and promote tumorigenesis. Although the mechanism by which YAP is suppressed in cytoplasm has been well-studied, how the activated YAP is sequestered in the nucleus remains unknown. Here, we demonstrate that YAP is a nucleocytoplasmic shuttling protein and its nuclear export is controlled by SET1A-mediated mono-methylation of YAP at K342, which disrupts the binding of YAP to CRM1. YAP mimetic methylation knockin mice are more susceptible to colorectal tumorigenesis. Clinically, YAP K342 methylation is reversely correlated with cancer survival. Collectively, our study identifies SET1A-mediated mono-methylation at K342 as an essential regulatory mechanism for regulating YAP activity and tumorigenesis.

Myotonic dystrophy is a neuromuscular disease of RNA toxicity. The disease gene DMPK harbors expanded CTG trinucleotide repeats on its 3′-UTR. The transcripts of this mutant DMPK led to misregulation of RNA-binding proteins including MBNL1 and Celf1. In myoblasts, CUG-expansion impaired terminal differentiation. In this study, we formally tested how the abundance of Celf1 regulates normal myocyte differentiation, and how Celf1 expression level mediates CUG-expansion RNA toxicity-triggered impairment of myocyte differentiation. As the results, overexpression of Celf1 largely recapitulated the defects of myocytes with CUG-expansion, by increasing myocyte cycling. Knockdown of endogenous Celf1 level led to precocious myotube formation, supporting a negative connection between Celf1 abundance and myocyte terminal differentiation. Finally, knockdown of Celf1 in myocyte with CUG-expansion led to partial rescue, by promoting cell cycle exit. Our results suggest that Celf1 plays a distinctive and negative role in terminal myocyte differentiation, which partially contribute to DM1 RNA toxicity. Targeting Celf1 may be a valid strategy in correcting DM1 muscle phenotypes, especially for congenital cases.