Search Results (89)

Signalling between the ER and mitochondria regulates a number of key cellular functions that are damaged in frontotemporal dementia and related amyotrophic lateral sclerosis (FTD/ALS). This signalling involves close physical contacts between the two organelles that are mediated by the VAPB-PTPIP51 ER–mitochondria “tethering” proteins. A number of studies have shown that mutant genes which cause familial FTD/ALS disrupt the VAPB-PTPIP51 tethers and that this involves activation of GSK3β. TDP43 is one such mutant and altered TDP43 metabolism is central to FTD/ALS pathogenesis. Loss of Sigma-1 receptor function is also seen in FTD/ALS and there is evidence that Sigma-1 receptor agonists can repair damaged ER–mitochondria signalling. However, the underlying mechanisms are not properly understood. In this study, we show that the reference Sigma-1 receptor agonist PRE-084 stimulates VAPB-PTPIP51 binding and rescues FTD/ALS mutant TDP43-induced disruption to the VAPB-PTPIP51 interaction and linked ER–mitochondria Ca²⁺ delivery. We also show that these effects involve inhibition of the kinase GSK3β, a known negative regulator of VAPB-PTPIP51 binding. Finally, we show that ANAVEX2-73, a further Sigma-1 receptor agonist which is in clinical trials for Alzheimer’s disease, also stimulates VAPB-PTPIP51 binding via GSK3β inhibition. Our findings provide novel insights into the mechanisms by which Sigma-1 receptor agonists influence defective ER–mitochondria signalling in FTD/ALS. Full article

Fatty liver disease represents a major metabolic disorder affecting domestic animals worldwide, with significant implications for animal health, welfare, and agricultural productivity. Disrupted communication between mitochondria and other organelles—particularly the endoplasmic reticulum, lipid droplets, and lysosomes—plays a critical role in disease pathogenesis. This review synthesizes knowledge on inter-organellar communication across domestic animals, with emphasis on species-specific adaptations. We address the “Dairy Cow Paradox”—periparturient dairy cows develop severe hepatic steatosis (>30% liver fat), yet under sterile conditions, they have a higher threshold for progressing to sterile steatohepatitis compared to rodents and humans. However, it is critical to note that severe fatty liver in dairy cows is indeed associated with impaired autophagy, inflammation, and liver damage, particularly when accompanied by ketosis or concurrent infections, and 39% of transition cows exhibit moderate to severe lymphocytic hepatitis. We propose that the tolerance to severe steatosis in dairy cows arises from three adaptations: (1) attenuated innate immune sensing via the cGAS-STING pathway; (2) enhanced lipid buffering from perilipin 5 (PLIN5) with a hypothesized ruminant-specific Val152 substitution that may stabilize lipid droplet–mitochondria contacts; and (3) dampened calcium signaling due to ER–mitochondria membrane lipid raft rigidity, elevated inositol 1,4,5-trisphosphate receptor 2 (IP₃R2) expression, and reduced mitochondrial calcium uniporter (MCU) conductance. We contrast this with the inflammatory steatohepatitis common in rodent models driven by calcium overload and mitochondrial DNA (mtDNA) release, and glucocorticoid-mediated mitofusin 1 (MFN1) suppression, causing mitochondrial fragmentation in poultry. We identify critical knowledge gaps, including the need to define bovine and avian mitochondria-associated endoplasmic reticulum membrane (MAM) proteomes and spatially resolve hepatic zonal communication patterns. Targeting organellar communication hubs with nutraceuticals or pharmacological agents offers promising therapeutic strategies. Full article

The kidney is a highly specialized organ that maintains systemic homeostasis through tightly coordinated cellular and molecular mechanisms. Renal parenchymal cells regulate metabolic waste excretion, electrolyte and acid–base balance, and blood pressure control—functions that rely on the dynamic integration of intracellular organelles. Recent advances in molecular and biochemical research have highlighted how inter-organelle communication is essential for preserving renal cell function and adaptive responses to stress. This review focuses on the molecular crosstalk among key organelles—including the nucleus, endoplasmic reticulum (ER), Golgi apparatus, mitochondria, lysosomes, and peroxisomes—primarily in tubular epithelial cells. We discuss how these interactions coordinate metabolic signaling, protein homeostasis, redox balance, and energy production and how their disruption contributes to maladaptive pathways during acute kidney injury (AKI), ultimately promoting chronic kidney disease (CKD) transition. Particular focus is placed on emerging pathways linking organelle dysfunction to inflammation, fibrosis, and metabolic reprogramming. Furthermore, we highlight recent advances in genetics and molecular therapeutics targeting organelle communication, including modulation of ER stress responses, mitochondrial biogenesis, and lysosomal function. Clinically approved agents, such as mTOR inhibitors, and experimental approaches—such as chemical chaperones and mitochondrial transplantation—demonstrate the potential to restore organelle homeostasis and mitigate renal injury. Overall, elucidating the molecular networks governing organelle crosstalk provides critical insights into kidney disease pathogenesis and identifies novel targets for therapeutic intervention in AKI-to-CKD transition. Full article

Mitochondria–endoplasmic reticulum contact sites (MERCs) are known as the specialized areas that are involved in a large number of intracellular signaling pathways that regulate Ca²⁺ homeostasis, lipid transport, mitochondrial dynamics, cell death, and autophagy. Understanding MERC dynamics has important therapeutic implications in cancer, as these contacts regulate fundamental cellular processes and MERCs represent promising targets for therapeutic interventions aimed at improving cancer treatment outcomes. Despite the accumulated data, the role of MERCs in carcinogenesis still remains unknown; thus, it seems promising to search for new tools facilitating the study of MERCs in tumor cells. The structure of MERCs can be examined in great detail using transmission electron microscopy (TEM). Currently, several hundred TEM images are required to obtain reliable data on these contacts. The speed of data processing can be significantly improved by using fast and accurate image analysis techniques based on deep learning models. In this study, five U-Net models with a ResNet34 encoder network were evaluated, including the basic U-Net-Vanilla architecture as well as models incorporating various attention blocks and blocks capturing multilevel image structure, for the segmentation of mitochondria and the endoplasmic reticulum (ER). The best performance on the test dataset was demonstrated by the U-Net-scSE network, with F1 scores of 0.872 for mitochondria and 0.744 for the ER being achieved. Two models were tested for their ability to leverage pre-training on external datasets (Lucchi++, Kasthuri++, and DeepPi-EM). Additionally, models pre-trained on the CEM500K dataset were evaluated after the parameters had been tuned on the data. It was demonstrated by the results that pre-training or the use of pre-trained networks did not lead to an improvement in the IoU and F1 metrics on the test dataset. Subsequent image analysis was conducted to assess two types of MERCs in the segmented images. Finally, the free and user-friendly UltraNet web server was developed for automated analysis of mitochondria, ER, and MERCs using TEM images. Full article

(1) Background: Calcium transfer between the endoplasmic reticulum (ER) and mitochondria through the IP3R–VDAC1 complex at mitochondria-associated ER membranes (MAMs) is essential for cellular homeostasis. Alterations in this signalling axis have been implicated in ageing and cellular senescence. (2) Methods: We developed an in vitro human dermal fibroblast (HDF) model combining replicative senescence and acute oxidative stress to investigate the role of ER–mitochondria coupling in skin ageing and to enable biomolecule screening. (3) Results: In situ proximity ligation assays revealed that replicative senescence significantly increased the number of VDAC1/IP3R complexes per cell (+85% and +72%, p < 0.01), together with elevated cellular reactive oxygen species (+47% and +74%, p < 0.05). Consistently, acute oxidative stress (50 µM t-BHP, 30 min) rapidly increased VDAC1/IP3R complexes (+48%, p < 0.001) and intra-mitochondrial calcium levels (+19%, p < 0.001). These effects persisted for 24 h post-treatment and were associated with impaired mitochondrial function (−27% in the Bioenergetic Health Index, p < 0.05). We also established a flexibility index capturing both acute and long-term adaptations and detecting the protective effects of an orchid extract. (4) Conclusions: ER–mitochondria coupling disruption via the IP3R–VDAC1 complex may contribute to oxidative stress-induced senescence and represent a key mechanism in extrinsic skin ageing. Full article

Background: Glioblastoma (GBM) exhibits marked cellular heterogeneity and resistance to therapy. Calcium (Ca²⁺) signaling at endoplasmic reticulum (ER)–mitochondria contact sites has emerged as a key regulator of mitochondrial function and cell fate; however, its lineage-specific role and therapeutic relevance in GBM remain unclear. Methods: ITPR1 expression was analyzed using single-cell and bulk RNA sequencing (RNA-seq) datasets and validated by immunohistochemistry and survival analyses. Functional studies were conducted using genetic silencing or CRISPR-mediated activation of ITPR1, combined with DRP1 knockdown, Ca²⁺ imaging, transmission electron microscopy, co-immunoprecipitation, mitochondrial fractionation, and mitochondrial functional assays. Therapeutic efficacy was evaluated in orthotopic GBM xenograft models treated with 2-aminoethoxydiphenyl borate (2-APB), temozolomide (TMZ), or their combination. Results: ITPR1 was enriched in mesenchymal-like malignant cell states and associated with higher tumor grade, recurrence, and poor prognosis. ITPR1 knockdown suppressed GBM cell proliferation and tumor growth while promoting intrinsic apoptosis. Mechanistically, loss of ITPR1 impaired ER-to-mitochondria Ca²⁺ transfer, disrupted ER–mitochondria contacts, and altered mitochondrial ultrastructure. This was accompanied by reduced DRP1 Ser616 phosphorylation and mitochondrial recruitment, as well as decreased autophagy and mitophagy activity. Consequently, ITPR1 knockdown led to mitochondrial depolarization, increased mitochondrial reactive oxygen species (ROS) accumulation, and activation of mitochondria-dependent apoptosis. Conversely, DRP1 knockdown attenuated the mitochondrial and pro-survival effects induced by ITPR1 overexpression. In vivo, combined treatment with 2-APB and TMZ resulted in greater tumor suppression and prolonged survival compared with either treatment alone, accompanied by increased apoptosis and reduced proliferation in tumor tissues. Conclusions: ITPR1 promotes GBM progression by sustaining ER–mitochondria Ca²⁺ coupling and DRP1-dependent mitochondrial quality control, thereby maintaining mitochondrial homeostasis and cell survival. Targeting inositol 1,4,5-trisphosphate receptor (IP₃R)-mediated Ca²⁺ signaling with 2-APB enhances the therapeutic efficacy of TMZ, suggesting that ITPR1-centered Ca²⁺ signaling may represent a potential therapeutic vulnerability in aggressive GBM. Full article

Oleanolic acid (OA) is a hydrophobic pentacyclic triterpene widely distributed in the plant kingdom and characterized by broad biological activity, including antioxidant, anti-inflammatory, neuroprotective, renoprotective, and anticancer effects. Increasing evidence suggests, however, that many of these actions are better explained not by single molecular targets, but by OA-dependent modulation of an integrated organelle stress network involving mitochondria, the endoplasmic reticulum (ER), autophagy, mitophagy, and apoptosis. This review critically analyzes the available evidence on the effects of OA on the mitochondria–ER–autophagy–apoptosis axis, with particular emphasis on mechanisms governing the transition between cellular adaptation and cell death. The available literature indicates that, in non-cancer models, OA most commonly lowers reactive oxygen species (ROS), stabilizes mitochondrial function, attenuates the ER stress signature, and promotes adaptive autophagy and mitophagy. In contrast, in many cancer models, OA may enhance mitochondrial dysfunction, lower the threshold for mitochondrial apoptosis, and induce autophagy that can be either protective or cytotoxic depending on the biological context. Overall, the current evidence supports a model in which OA acts as a context-dependent modulator of the organelle stress threshold, shifting the balance of an integrated mitochondria–ER–autophagy–apoptosis network rather than functioning as a uniformly cytoprotective or uniformly proapoptotic compound. At the same time, the literature remains heterogeneous with respect to models, doses, exposure times, and markers used, while poor aqueous solubility and limited bioavailability continue to constrain translation. Future studies should therefore integrate analyses of mitochondria, ER, mitochondria–ER contact sites (MERCS), autophagy, apoptosis, pharmacokinetics, formulation, and safety in order to define the true potential of OA as a modulator of biological stress. Full article

Although LRRK2 mutations modulate systemic glucose homeostasis and metabolic dysfunction precedes Parkinson’s disease (PD) motor symptoms; the way in which pathogenic variants of LRRK2 disrupt astrocytic glucose metabolism and organellar homeostasis remains poorly understood. Here, we demonstrate that LRRK2-I1371V mutation causes profound metabolic and organellar dysfunction in LRRK2-I1371V PD-iPSC-derived astrocytes and U87 cells overexpressing I1371V variant. LRRK2-I1371V astrocytes exhibit significantly reduced GLUT1 expression and cell surface localization, resulting in impaired glucose uptake and decreased lactate production. This metabolic insufficiency correlates with cascading mitochondrial dysfunction, characterized by membrane depolarization, elevated reactive oxygen species, enhanced ubiquitination and reduced proteasomal activity. Reduced LAMP1/LAMP2 expression, impaired lysosomal acidification, and selective cathepsin D deficiency were observed. Accumulation of undegraded cargo was confirmed by transmission electron microscopy upon α-synuclein exposure. ER stress was evident by upregulation of GADD34/CHOP, increased phospho-PERK, and reduced nascent protein synthesis. Increased ER–mitochondrial contact via MAMs and enhanced STIM1-ORAI3 clustering reflect compensatory but ultimately insufficient responses to energy stress. Our results reveal that LRRK2-I1371V induces glucose uptake deficits, leading to energy depletion and integrated ER–mitochondria–lysosome dysfunction, thus indicating restoration of astrocytic metabolic capacity as a potential therapeutic strategy for LRRK2-associated PD. Full article

Mitochondria–endoplasmic reticulum contacts (MERCs) are physical structures formed between mitochondria and the endoplasmic reticulum (ER) through various tethering proteins, playing crucial roles in multiple physiological processes, including Ca²⁺ and lipid exchange between the ER and mitochondria, regulation of mitochondrial morphology and dynamics (fusion and fission), as well as the induction of autophagy and apoptosis. Mitofusin 2 (MFN2), a key mitochondrial fusion protein, has been identified as an essential structural component of MERCs. Our research demonstrates that 16:8 circadian intermittent fasting (CIF) leads to enhanced mitochondrial fusion. The upregulation of MFN2 reinforces MERC stability, thereby facilitating efficient Ca²⁺ transfer between the ER and mitochondria. This process sustains the activity of mitochondrial oxidative phosphorylation (OXPHOS) enzymes, elevates mitochondrial oxygen utilization efficiency, and ultimately augments ATP production. Consequently, these adaptations enhance cardiomyocyte tolerance to hypoxic conditions. This study elucidates a novel mechanism by which MERCs regulate cellular hypoxia resistance and proposes a potential therapeutic strategy for improving acute hypoxia tolerance through the modulation of Ca²⁺ transport at MERCs. Full article

The endoplasmic reticulum (ER) is a central hub of cellular proteostasis, coordinating protein folding, lipid metabolism, calcium signaling, and inter-organelle communication. Disruptions in ER function activate the unfolded protein response (UPR), an evolutionarily conserved signaling network mediated by PERK, IRE1α, and ATF6. Initially viewed primarily as a stress-mitigating mechanism, the UPR is now recognized as a central coordinator of diverse cellular stress-response pathways. This review focuses on mechanistic insights into UPR signaling, with particular emphasis on its crosstalk with oxidative stress regulation, mitochondrial function and mitochondria–ER contact sites, autophagy, inflammatory signaling, and metabolic sensing. The analysis integrates evidence from biochemical and structural studies, genetic and pharmacological perturbation models, and selected in vivo investigations from PubMed and Google Scholar between 2000 and 2025, focusing on mechanistic, experimental and translational studies addressing UPR signaling and ER stress. Together, these studies demonstrate how transient UPR activation promotes cellular adaptation through coordinated transcriptional, translational, and organelle-specific responses. We further discuss how sustained or unresolved ER stress alters UPR outputs, shifting signaling toward maladaptive outcomes such as mitochondrial dysfunction, dysregulated autophagy, oxidative imbalance, and apoptosis. By placing the UPR within a network of interconnected stress pathways, this work provides a framework for understanding how ER proteostasis is linked to cell fate decisions under stress. Full article

Oocytes cultured in vitro are exposed to high oxygen tension and lack follicular antioxidants, leading to redox imbalance. Eicosapentaenoic acid (EPA), a marine long-chain n-3 polyunsaturated fatty acid, possesses strong antioxidant activity. Here, using pigs as a model, we examined the effects of EPA on oocyte in vitro maturation (IVM) and subsequent developmental competence. Cumulus–oocyte complexes were cultured with EPA, followed by assessment of nuclear and cytoplasmic maturation and embryonic development; transcriptomic and proteomic analyses were conducted to explore underlying mechanisms. Supplementation with 10 µM EPA significantly improved maturation and blastocyst rates by reducing spindle defects, facilitating a more uniform organization of cortical granules and mitochondria. EPA increased resolvin E1 accumulation and reduced cumulus-cell apoptosis through downregulation of TNF-α and BAX and upregulation of BCL2. In MII oocytes, EPA lowered apoptosis, DNA damage, and ROS levels while enhancing SOD2 and GPX4 expression. Mitochondrial quality and turnover were improved via upregulation of PPARGC1A, NDUFS2, PINK1, LC3, FIS1, MUL1, and OPA1, alongside strengthened ER–mitochondria contacts. These findings demonstrate that EPA alleviates oxidative stress, optimizes mitochondrial function, and enhances porcine oocyte maturation and developmental competence in a parthenogenetic model, highlighting its potential as a marine-derived functional additive for reproductive biotechnology. Future studies will be required to validate these effects under fertilization-based embryo production systems and to further refine dose–response relationships using expanded embryo-quality endpoints. Full article

Ischemic stroke remains one of the most catastrophic diseases in neurology, in which, due to a disturbance in the cerebral blood flow, the brain is acutely deprived of its oxygen and glucose oligomer, which in turn rapidly leads to energetic collapse and progressive cellular death. There is now increasing evidence that this type of stroke is not simply a type of ‘oxidative stress’ but rather a programmable loss-of-redox homeostasis, within which electron flow and the balance of oxidants/reductants are cumulatively displaced at the level of the single molecule and at the level of the cellular area. The advances being made in cryo-electron microscopy, lipidomics, and spatial omics are coupled with the introduction of a redox code produced by the interaction of the couples NADH/NAD⁺, NADPH/NADP⁺, GSH/GSSG, BH₄/BH₂, and NO/SNO, which determine the end results of the fates of the neurons, glia, endothelium, and pericytes. Within the mitochondria, pathophysiological events, including reverse electron transport, succinate overflow, and permeability transition, are found to be the first events after reperfusion, while signals intercommunicating via ER–mitochondria contact, peroxisomes, and nanotunnels control injury propagation. At the level of the tissue, events such as the constriction of the pericytes, the degradation of the glycocalyx, and the formation of neutrophil extracellular traps underlie microvascular failure (at least), despite the effective recanalization of the vessels. Systemic influences such as microbiome products, oxidized lipids, and free mitochondrial DNA in cells determine the redox imbalance, but this generally occurs outside the brain. We aim to synthesize how the progressive stages of ischemic injury evolve from the cessation of flow to the collapse of the cell structure. Within seconds of injury, there is reverse electron transport (RET) through mitochondrial complex I, with bursts of superoxide (O₂•⁻) and hydrogen peroxide (H₂O₂) being produced, which depletes the stores of superoxide dismutase, catalase, and glutathione peroxidase. Accumulated succinate and iron-induced lipid peroxidation trigger ferroptosis, while xanthine oxidase and NOX2/NOX4, as well as uncoupled eNOS/nNOS, lead to oxidative and nitrosative stress. These cascades compromise the function of neuronal mitochondria, the glial antioxidant capacity, and endothelial–pericyte integrity, leading to the degradation of the glycocalyx with microvascular constriction. Stroke, therefore, represents a continuum of redox disequilibrium, a coordinated biochemical failure linking the mitochondrial metabolism with membrane integrity and vascular homeostasis. Full article

Mitochondrial dynamics are important for cellular health and include morphology, fusion, fission, vesicle formation, transport and contact formation with other organelles. Myosin XIX (Myo19) is an actin-based motor, which competes with TRAK1/2 adaptors of microtubule-based motors for binding to the outer mitochondrial membrane receptors Mitochondrial Rho GTPases 1/2 (Miro). Currently, it is poorly understood how Myo19 contributes to mitochondrial dynamics. Here, we report on a Myo19-deficient mouse model and the ultrastructure of the mitochondria from cells of Myo19-deficient mice and HEK cells, Miro-deficient HEK cells and TRAK1-deficient HAP1 cells. Myo19-deficient mitochondria in MEFs and HEK cells have morphological alterations in the inner mitochondrial membrane with reduced numbers of malformed cristae. In addition, mitochondria in Myo19-deficient cells showed fewer ER–mitochondria contact sites (ERMCSs). In accordance with the ultrastructural observations, Myo19-deficient MEFs had lower oxygen consumption rates and a reduced abundance of OXPHOS supercomplexes. The simultaneous loss of Miro1 and Miro 2 led to a comparable mitochondria phenotype and reduced ERMCSs as observed upon the loss of Myo19. However, the loss of TRAK1 caused only a reduction in the number of cristae, but not ERMCSs. These results demonstrate that both actin- and microtubule-based motors regulate cristae formation, but only Myo19 and its membrane receptor Miro regulate ERMCSs. Full article

Mitochondria-associated membranes (MAMs) are essential for cellular homeostasis. MAMs are specialized contact sites located between the endoplasmic reticulum (ER) and mitochondria and control apoptotic pathways, lipid metabolism, autophagy initiation, and calcium signaling, processes critical to the survival and function of neurons. Although this area of membrane biology remains understudied, increasing evidence links MAM dysfunction to the etiology of major neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS). MAMs consist of a network of protein complexes that mediate molecular exchange and ER–mitochondria tethering. MAMs regulate lipid flow in the brain, including phosphatidylserine and cholesterol; disruption of this process causes membrane instability and impaired synaptic function. Inositol 1,4,5-trisphosphate receptor—voltage-dependent anion channel 1 (IP3R-VDAC1) interactions at MAMs maintain calcium homeostasis, which is required for mitochondria to produce ATP; dysregulation promotes oxidative stress and neuronal death. An effective therapeutic approach for altering neurodegenerative processes is to restore the functional integrity of MAMs. Improving cell-to-cell interactions and modulating MAM-associated proteins may contribute to the restoration of calcium homeostasis and lipid metabolism, both of which are key for neuronal protection. MAMs significantly contribute to the progression of neurodegenerative diseases, making them promising targets for future therapeutic research. This review emphasizes the increasing importance of MAMs in the study of neurodegeneration and their potential as novel targets for membrane-based therapeutic interventions. Full article

Mitochondria-ER contact sites (MERCS) are vital for mitochondrial dynamics, lipid exchange, Ca²⁺ homeostasis, and energy metabolism. We examined whether mitochondrial metabolism changes during the cell cycle depend on MERCS dynamics and are regulated by the outer mitochondrial protein mitochondrial rho GTPase 1 (MIRO1). Wound healing was assessed in mice with fibroblast-specific deletion of MIRO1. Wild-type and MIRO1^-/- fibroblasts and vascular smooth muscle cells were evaluated for proliferation, cell cycle progression, number of MERCS, distance, and protein composition throughout the cell cycle. Restoration of MIRO1 mutants was used to test the role of MIRO1 domains; Ca²⁺ transients and mitochondrial metabolism were evaluated using biochemical, immunodetection, and fluorescence techniques. MERCS increased in number during G1/S compared with during G0, which was accompanied by a notable rise in protein–protein interactions involving VDAC1 and IP3R as well as GRP75 and MIRO1 by proximity-ligation assays. Split-GFP ER/mitochondrial contacts of 40 nm also increased. Mitochondrial Ca²⁺ concentration ([Ca²⁺]), membrane potential, and ATP levels correlated with the formation of MERCS during the cell cycle. MIRO1 deficiency blocked G1/S progression and the cell-cycle-dependent formation of MERCS and altered ER Ca²⁺ release and mitochondrial Ca²⁺ uptake. MIRO1 mutants lacking the Ca²⁺-sensitive EF hands or the transmembrane domain did not rescue cell proliferation or the formation of MERCS. MIRO1 controls an increase in the number of MERCS during cell cycle progression and increases mitochondrial [Ca²⁺], driving metabolic activity and proliferation through its EF hands. Full article