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The Ca2+ release in microdomains formed by intercompartmental contacts, such as mitochondria-associated endoplasmic reticulum membranes (MAMs), encodes a signal that contributes to Ca2+ homeostasis and cell fate control. However, the composition and function of MAMs remain to be fully defined. Here, we focused on the transient receptor potential vanilloid 1 (TRPV1), a Ca2+-permeable ion channel and a polymodal nociceptor. We found TRPV1 channels in the reticular membrane, including some at MAMs, in a rat cardiomyoblast cell line (SV40-transformed H9c2) by Western blotting, immunostaining, cell fractionation, and proximity ligation assay. We used chemical and genetic probes to perform Ca2+ imaging in four cellular compartments: the endoplasmic reticulum (ER), cytoplasm, mitochondrial matrix, and mitochondrial surface. Our results showed that the ER Ca2+ released through TRPV1 channels is detected at the mitochondrial outer membrane and transferred to the mitochondria. Finally, we observed that prolonged TRPV1 modulation for 30 min alters the intracellular Ca2+ equilibrium and influences the MAM structure or the hypoxia/reoxygenation-induced cell death. Thus, our study provides the first evidence that TRPV1 channels contribute to MAM Ca2+ exchanges. [ABSTRACT FROM AUTHOR]

The heterotrimeric Sec61 protein complex forms the functional core of the so-called translocon that forms an aqueous channel in the endoplasmic reticulum (ER). The primary role of the Sec61 complex is to allow protein import in the ER during translation. Surprisingly, a completely different function in intracellular Ca2+ homeostasis has emerged for the Sec61 complex, and the latter is now accepted as one of the major Ca2+-leak pathways of the ER. In this review, we first discuss the structure of the Sec61 complex and focus on the pharmacology and regulation of the Sec61 complex as a Ca2+-leak channel. Subsequently, we will pay particular attention to pathologies that are linked to Sec61 mutations, such as plasma cell deficiency and congenital neutropenia. Finally, we will explore the relevance of the Sec61 complex as a Ca2+-leak channel in various pathophysiological (ER stress, apoptosis, ischemia-reperfusion) and pathological (type 2 diabetes, cancer) settings. [ABSTRACT FROM AUTHOR]

In this study, we investigated ionic mechanisms involved in growth arrest induced by extracellular ATP in androgen-independent prostate cancer cells. Extracellular ATP reversibly induced a rapid and sustained intracellular pH ([pH.sub.i]) decrease from 7.41 to 7.11. Inhibition of [Ca.sup.2+] influx, lowering extracellular [Ca.sup.2+], and buffering cytoplasmic [Ca.sup.2+] inhibited ATP-induced acidification, thereby demonstrating that acidification is a consequence of [Ca.sup.2+] entry. We show that ATP induced reuptake of [Ca.sup.2+] by the mitochondria and a transient depolarization of the inner mitochondrial membrane. ATP-induced acidification was reduced after the dissipation of the mitochondrial proton gradient by rotenone and carbonyl cyanide p-trifluoromethoxyphenylhydrazone, after inhibition of [Ca.sup.2+] uptake into the mitochondria by ruthenium red, and after inhibition of the [F.sub.0][F.sub.1]-ATPase with oligomycin. ATP-induced acidification was not induced by either stimulation of the [Cl.sup.-]/HC[O.sup.-.sub.3] exchanger or inhibition of the [Na.sup.+]/[H.sup.+] exchanger. In addition, intracellular acidification, induced by an ammonium prepulse method, reduced the amount of releasable [Ca.sup.2+] from the endoplasmic reticulure, assessed by measuring change in cytosolic [Ca.sup.2+] induced by thapsigargin or ATP in a [Ca.sup.2+]-free medium. This latter finding reveals cross talk between [pH.sub.i] and [Ca.sup.2+] homeostasis in which the [Ca.sup.2+]-induced intracellular acidification can in turn regulate the amount of [Ca.sup.2+] that can be released from the endoplasmic reticulum. Furthermore, [pH.sub.i] decrease was capable of reducing cell growth. Taken together, our results suggest that ATP-induced acidification in DU-145 ceils results from specific effect of mitochondrial function and is one of the major mechanisms leading to growth arrest induced by ATP. prostate; cancer; acidification

In response to many stresses, such as oncogene activation or DNA damage, cells can enter cellular senescence, a state of proliferation arrest accompanied by a senescence-associated secretory phenotype (SASP). Cellular senescence plays a key role in many physiopathological contexts, including cancer, aging and aging-associated diseases, therefore, it is critical to understand how senescence is regulated. Calcium ions (Ca2+) recently emerged as pivotal regulators of cellular senescence. However, how Ca2+ levels are controlled during this process is barely known. Here, we report that intracellular Ca2+ contents increase in response to many senescence inducers in immortalized human mammary epithelial cells (HMECs) and that expression of calbindin 1 (CALB1), a Ca2+-binding protein, is upregulated in this context, through the Ca2+-dependent calcineurin/NFAT pathway. We further show that overexpression of CALB1 buffers the rise in intracellular Ca2+ levels observed in senescent cells. Finally, we suggest that increased expression of Ca2+-binding proteins calbindins is a frequent mark of senescent cells. This work thus supports that, together with Ca2+channels, Ca2+-binding proteins modulate Ca2+ levels and flux during cellular senescence. This opens potential avenues of research to better understand the role of Ca2+ and of Ca2+-binding proteins in regulating cellular senescence. [ABSTRACT FROM AUTHOR]

Glucotoxicity-induced β-cell dysfunction in type 2 diabetes is associated with alterations of mitochondria and the endoplasmic reticulum (ER). Both organelles interact at contact sites, defined as mitochondria-associated membranes (MAMs), which were recently implicated in the regulation of glucose homeostasis. The role of MAMs in β-cells is still largely unknown, and their implication in glucotoxicity-associated β-cell dysfunction remains to be defined. Here, we report that acute glucose treatment stimulated ER-mitochondria interactions and calcium (Ca2+) exchange in INS-1E cells, whereas disruption of MAMs altered glucose-stimulated insulin secretion (GSIS). Conversely, chronic incubations with high glucose of either INS-1E cells or human pancreatic islets altered GSIS and concomitantly reduced ER Ca2+ store, increased basal mitochondrial Ca2+, and reduced ATP-stimulated ER-mitochondria Ca2+ exchanges, despite an increase of organelle interactions. Furthermore, glucotoxicity-induced perturbations of Ca2+ signaling are associated with ER stress, altered mitochondrial respiration, and mitochondria fragmentation, and these organelle stresses may participate in increased organelle tethering as a protective mechanism. Last, sustained induction of ER-mitochondria interactions using a linker reduced organelle Ca2+ exchange, induced mitochondrial fission, and altered GSIS. Therefore, dynamic organelle coupling participates in GSIS in β-cells, and over time, disruption of organelle Ca2+ exchange might be a novel mechanism contributing to glucotoxicity-induced β-cell dysfunction. [ABSTRACT FROM AUTHOR]

Effects of hyperprolactinemia on rat prostate growth: evidence of androgeno-dependence. Am J Physiol Endocrinol Metab 280: E120-E129, 2001.--The effects of the polypeptide hormone prolactin (PRL) in the development and regulation of benign prostate hyperplasia (BPH) and also in prostate cancer are not very well characterized. This study examines the action of PRL, either alone or in association with androgens [testosterone (T) or dihydrotestosterone (DHT)], in the rat prostate gland. The effects of PRL and androgens were investigated after 30 and 60 days in control, castrated, castrated with a substitutive implant of T or DHT, and shamoperated Wistar rats. To enhance PRL release, we induced hyperprolactinemia by administering chronic injections of sulpiride (40 mg [multiplied by] [kg.sup.-1] [multiplied by] day-1). Chronic hyperprolactinemia induces enlargement and inflammation of the lateral rat prostate without any histological changes on ventral and dorsal lobes. We also demonstrate that hyperprolactinemia induces Bcl-2 overexpression in the lateral rat prostate and that this could inhibit the level of apoptosis. The in vivo model established here is a useful in vivo approach for studying the hormonal regulation of normal and pathological prostate development. prolactin; testosterone; dihydrotestosterone

The endoplasmic reticulum (ER) is involved in many cellular functions, including protein folding and Ca2+ homeostasis. The ability of cells to respond to the ER stress is critical for cell survival, and disruption in such regulation can lead to apoptosis. ER stress is accompanied by alterations in Ca2+ homeostasis, and the ER Ca2+ store depletion by itself can induce ER stress and apoptosis. Despite that, the ER Ca2+ leak channels activated in response to the ER stress remain poorly characterized. Here we demonstrate that ER Ca2+ depletion during the ER stress occurs via translocon, the ER protein complex involved in translation. Numerous ER stress inducers stimulate the ER Ca2+ leak that can be prevented by translocon inhibitor, anisomycin. Expression of GRP78, an ER stress marker, increased following treatment with puromycin (a translocon opener) and was suppressed by anisomycin, confirming a primary role of translocon in ER stress induction. Inhibition of ER store depletion by anisomycin significantly reduces apoptosis stimulated by the ER stress inducers. We suggest that translocon opening is physiologically modulated by GRP78, particularly during the ER stress. The ability to modulate the ER Ca2+ permeability and subsequent ER stress can lead to development of a novel therapeutic approach. [ABSTRACT FROM AUTHOR]

In pancreatic acinar cells, low, threshold concentrations of acetylcholine (ACh) or cholecystokinin (CCK) induce repetitive local cytosolic Ca2+ spikes in the apical pole, while higher concentrations elicit global signals. We have investigated the process that transforms local Ca2+ spikes to global Ca2+ transients, focusing on the interactions of multiple intracellular messengers. ACh-elicited local Ca2+ spikes were transformed into a global sustained Ca2+ response by cyclic ADP-ribose (cADPR) or nicotinic acid adenine dinucleotide phosphate (NAADP), whereas inositol 1,4,5-trisphosphate (IP3) had a much weaker effect. In contrast, the response elicited by a low CCK concentration was strongly potentiated by IP3, whereas cADPR and NAADP had little effect. Experiments with messenger mixtures revealed a local interaction between IP3 and NAADP and a stronger global potentiating interaction between cADPR and NAADP. NAADP strongly amplified the local Ca2+ release evoked by a cADPR/IP3 mixture eliciting a vigorous global Ca2+ response. Different combinations of Ca2+ releasing messengers can shape the spatio-temporal patterns of cytosolic Ca2+ signals. NAADP and cADPR are emerging as key messengers in the globalization of Ca2+ signals. [ABSTRACT FROM AUTHOR]

Discusses research which aimed to explore the role of translocon complex, present on the endoplasmic reticulum membrane involved in protein translocation, in the activation of store operated calcium entry (SOCE). Possible functional link between the passive leakage via the translocon and SOCE stimulation; Effect of the inhibition of the calcium leak via the translocon by anisomycin; Investigation whether calcium passive leakage occurring specifically through the translocon could activate the store operated channels current via passive leakage activation.

Artificial intelligence (AI) has gained massive interest with the public release of the conversational AI "ChatGPT," but it also has become a matter of concern for academia as it can easily be misused. We performed a quantitative evaluation of the performance of ChatGPT on a medical physiology university examination. Forty-one answers were obtained with ChatGPT and compared to the results of 24 students. The results of ChatGPT were significantly better than those of the students; the median (IQR) score was 75% (66-84%) for the AI compared to 56% (43-65%) for students ( P < 0.001). The exam success rate was 100% for ChatGPT, whereas 29% ( n = 7) of students failed. ChatGPT could promote plagiarism and intellectual laziness among students and could represent a new and easy way to cheat, especially when evaluations are performed online. Considering that these powerful AI tools are now freely available, scholars should take great care to construct assessments that really evaluate student reflection skills and prevent AI-assisted cheating. NEW & NOTEWORTHY The release of the conversational artificial intelligence (AI) ChatGPT has become a matter of concern for academia as it can easily be misused by students for cheating purposes. We performed a quantitative evaluation of the performance of ChatGPT on a medical physiology university examination and observed that ChatGPT outperforms medical students obtaining significantly better grades. Scholars should therefore take great care to construct assessments crafted to really evaluate the student reflection skills and prevent AI-assisted cheating.

The heterotrimeric Sec61 protein complex forms the functional core of the so-called translocon that forms an aqueous channel in the endoplasmic reticulum (ER). The primary role of the Sec61 complex is to allow protein import in the ER during translation. Surprisingly, a completely different function in intracellular Ca 2+ homeostasis has emerged for the Sec61 complex, and the latter is now accepted as one of the major Ca 2+ -leak pathways of the ER. In this review, we first discuss the structure of the Sec61 complex and focus on the pharmacology and regulation of the Sec61 complex as a Ca 2+ -leak channel. Subsequently, we will pay particular attention to pathologies that are linked to Sec61 mutations, such as plasma cell deficiency and congenital neutropenia. Finally, we will explore the relevance of the Sec61 complex as a Ca 2+ -leak channel in various pathophysiological (ER stress, apoptosis, ischemia-reperfusion) and pathological (type 2 diabetes, cancer) settings., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Parys and Van Coppenolle.)

During myocardial infarction, dysregulation of Ca 2+ homeostasis between the reticulum, mitochondria, and cytosol occurs in cardiomyocytes and leads to cell death. Ca 2+ leak channels are thought to be key regulators of the reticular Ca 2+ homeostasis and cell survival. The present study aimed to determine whether a particular reticular Ca 2+ leak channel, the translocon, also known as translocation channel, could be a relevant target against ischemia/reperfusion-mediated heart injury. To achieve this objective, we first used an intramyocardial adenoviral strategy to express biosensors in order to assess Ca 2+ variations in freshly isolated adult mouse cardiomyocytes to show that translocon is a functional reticular Ca 2+ leak channel. Interestingly, translocon activation by puromycin mobilized a ryanodine receptor (RyR)-independent reticular Ca 2+ pool and did not affect the excitation-concentration coupling. Second, puromycin pretreatment decreased mitochondrial Ca 2+ content and slowed down the mitochondrial permeability transition pore (mPTP) opening and the rate of cytosolic Ca 2+ increase during hypoxia. Finally, this translocon pre-activation also protected cardiomyocytes after in vitro hypoxia reoxygenation and reduced infarct size in mice submitted to in vivo ischemia-reperfusion. Altogether, our report emphasizes the role of translocon in cardioprotection and highlights a new paradigm in cardioprotection by functionally uncoupling the RyR-dependent Ca 2+ stores and translocon-dependent Ca 2+ stores.

Background: Ischemic heart diseases are a major cause of death worldwide. Different animal models, including cardiac surgery, have been developed over time. Unfortunately, the surgery models have been reported to trigger an important inflammatory response that might be an effect modifier, where involved molecular processes have not been fully elucidated yet., Objective: We sought to perform a thorough characterization of the sham effect in the myocardium and identify the interfering inflammatory reaction in order to avoid misinterpretation of the data via systems biology approaches., Methods and Results: We combined a comprehensive analytical pipeline of mRNAseq dataset and systems biology analysis to characterize the acute phase response of mouse myocardium at 0 min, 45 min, and 24 h after surgery to better characterize the molecular processes inadvertently induced in sham animals. Our analysis showed that the surgical intervention induced 1209 differentially expressed transcripts (DETs). The clustering of positively co-regulated transcript modules at 45 min fingerprinted the activation of signalization pathways, while positively co-regulated genes at 24 h identified the recruitment of neutrophils and the differentiation of macrophages. In addition, we combined the prediction of transcription factors (TF) regulating DETs with protein-protein interaction networks built from these TFs to predict the molecular network which have induced the DETs. By mean of this retro-analysis of processes upstream gene transcription, we revealed a major role of the Il-6 pathway and further confirmed a significant increase in circulating IL-6 at 45 min after surgery., Conclusion: This study suggests that a strong induction of the IL-6 axis occurs in sham animals over the first 24 h and leads to the induction of inflammation and tissues' homeostasis processes., (Copyright © 2019 Badawi, Paccalet, Harhous, Pillot, Augeul, Van Coppenolle, Lachuer, Kurdi, Crola Da Silva, Ovize and Bidaux.)