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Proceedings of the National Academy of... Aug 2022Dynamic regulation of mitochondrial morphology provides cells with the flexibility required to adapt and respond to electron transport chain (ETC) toxins and...
Dynamic regulation of mitochondrial morphology provides cells with the flexibility required to adapt and respond to electron transport chain (ETC) toxins and mitochondrial DNA-linked disease mutations, yet the mechanisms underpinning the regulation of mitochondrial dynamics machinery by these stimuli is poorly understood. Here, we show that pyruvate dehydrogenase kinase 4 (PDK4) is genetically required for cells to undergo rapid mitochondrial fragmentation when challenged with ETC toxins. Moreover, PDK4 overexpression was sufficient to promote mitochondrial fission even in the absence of mitochondrial stress. Importantly, we observed that the PDK4-mediated regulation of mitochondrial fission was independent of its canonical function, i.e., inhibitory phosphorylation of the pyruvate dehydrogenase complex (PDC). Phosphoproteomic screen for PDK4 substrates, followed by nonphosphorylatable and phosphomimetic mutations of the PDK4 site revealed cytoplasmic GTPase, Septin 2 (SEPT2), as the key effector molecule that acts as a receptor for DRP1 in the outer mitochondrial membrane to promote mitochondrial fission. Conversely, inhibition of the PDK4-SEPT2 axis could restore the balance in mitochondrial dynamics and reinvigorates cellular respiration in mitochondrial fusion factor, mitofusin 2-deficient cells. Furthermore, PDK4-mediated mitochondrial reshaping limits mitochondrial bioenergetics and supports cancer cell growth. Our results identify the PDK4-SEPT2-DRP1 axis as a regulator of mitochondrial function at the interface between cellular bioenergetics and mitochondrial dynamics.
Topics: Cell Respiration; GTP Phosphohydrolases; Gene Expression; Mitochondria; Mitochondrial Dynamics; Protein Kinases
PubMed: 35969774
DOI: 10.1073/pnas.2120157119 -
Redox Biology Jun 2022Imbalanced mitochondrial dynamics including inhibited mitochondrial fusion is associated with cardiac dysfunction as well as tumorigenesis. This study sought to explore...
Imbalanced mitochondrial dynamics including inhibited mitochondrial fusion is associated with cardiac dysfunction as well as tumorigenesis. This study sought to explore the effects of promoting mitochondrial fusion on doxorubicin(Dox)-induced cardiotoxicity and its antitumor efficacy, with a focus on the underlying metabolic mechanisms. Herein, the inhibition of Mfn2-mediated mitochondrial fusion was identified as a key phenotype in Dox-induced cardiotoxicity. Restoration of Mfn2-mediated mitochondrial fusion enhanced mitochondrial oxidative metabolism, reduced cellular injury/apoptosis and inhibited mitochondria-derived oxidative stress in the Dox-treated cardiomyocytes. Application of lentivirus expressing Drp1 (mitochondrial fusion inhibitor) or Rote/Anti A (mitochondrial complex I/III inhibitors) blunted the above protective effects of Mfn2. Cardiac-specific Mfn2 transgenic mice showed preserved mitochondrial fusion and attenuated myocardial injury upon Dox exposure in vivo. The suppression of Mfn2-mediated mitochondrial fusion was induced by Dox-elicited upregulation of FoxO1, which inhibited the transcription of Mfn2 by binding to its promoter sites. In the B16 melanoma, Mfn2 upregulation not only attenuated tumor growth alone but also further delayed tumor growth in the presence of Dox. Mechanistically, Mfn2 synergized with the inhibitory action of Dox on glycolysis metabolism in the tumor cells. One common feature in both cardiomyocytes and tumor cells was that Mfn2 increased the ratio of oxygen consumption rate to extracellular acidification rate, suggesting Mfn2 triggered a shift from aerobic glycolysis to mitochondrial oxidative metabolism. In conclusion, targeting Mfn2-mediated mitochondrial fusion may provide a dual therapeutic advantage in Dox-based chemotherapy by simultaneously defending against Dox-induced cardiotoxicity and boosting its antitumor potency via metabolic shift.
Topics: Animals; Apoptosis; Cardiotoxicity; Doxorubicin; GTP Phosphohydrolases; Mice; Mitochondrial Dynamics; Myocytes, Cardiac; Oxidative Stress
PubMed: 35413642
DOI: 10.1016/j.redox.2022.102311 -
Nature Communications Jul 2019Accumulating evidence illustrates a fundamental role for mitochondria in lung alveolar type 2 epithelial cell (AEC2) dysfunction in the pathogenesis of idiopathic...
Accumulating evidence illustrates a fundamental role for mitochondria in lung alveolar type 2 epithelial cell (AEC2) dysfunction in the pathogenesis of idiopathic pulmonary fibrosis. However, the role of mitochondrial fusion in AEC2 function and lung fibrosis development remains unknown. Here we report that the absence of the mitochondrial fusion proteins mitofusin1 (MFN1) and mitofusin2 (MFN2) in murine AEC2 cells leads to morbidity and mortality associated with spontaneous lung fibrosis. We uncover a crucial role for MFN1 and MFN2 in the production of surfactant lipids with MFN1 and MFN2 regulating the synthesis of phospholipids and cholesterol in AEC2 cells. Loss of MFN1, MFN2 or inhibiting lipid synthesis via fatty acid synthase deficiency in AEC2 cells exacerbates bleomycin-induced lung fibrosis. We propose a tenet that mitochondrial fusion and lipid metabolism are tightly linked to regulate AEC2 cell injury and subsequent fibrotic remodeling in the lung.
Topics: Alveolar Epithelial Cells; Animals; Antibiotics, Antineoplastic; Bleomycin; Cells, Cultured; Cholesterol; GTP Phosphohydrolases; Idiopathic Pulmonary Fibrosis; Lipid Metabolism; Mice, Knockout; Mice, Transgenic; Mitochondrial Dynamics; Phospholipids
PubMed: 31358769
DOI: 10.1038/s41467-019-11327-1 -
International Journal of Oral Science Sep 2021Porphyromonas gingivalis (P. gingivalis), a key pathogen in periodontitis, has been shown to accelerate the progression of atherosclerosis (AS). However, the definite...
Porphyromonas gingivalis (P. gingivalis), a key pathogen in periodontitis, has been shown to accelerate the progression of atherosclerosis (AS). However, the definite mechanisms remain elusive. Emerging evidence supports an association between mitochondrial dysfunction and AS. In our study, the impact of P. gingivalis on mitochondrial dysfunction and the potential mechanism were investigated. The mitochondrial morphology of EA.hy926 cells infected with P. gingivalis was assessed by transmission electron microscopy, mitochondrial staining, and quantitative analysis of the mitochondrial network. Fluorescence staining and flow cytometry analysis were performed to determine mitochondrial reactive oxygen species (mtROS) and mitochondrial membrane potential (MMP) levels. Cellular ATP production was examined by a luminescence assay kit. The expression of key fusion and fission proteins was evaluated by western blot and immunofluorescence. Mdivi-1, a specific Drp1 inhibitor, was used to elucidate the role of Drp1 in mitochondrial dysfunction. Our findings showed that P. gingivalis infection induced mitochondrial fragmentation, increased the mtROS levels, and decreased the MMP and ATP concentration in vascular endothelial cells. We observed upregulation of Drp1 (Ser616) phosphorylation and translocation of Drp1 to mitochondria. Mdivi-1 blocked the mitochondrial fragmentation and dysfunction induced by P. gingivalis. Collectively, these results revealed that P. gingivalis infection promoted mitochondrial fragmentation and dysfunction, which was dependent on Drp1. Mitochondrial dysfunction may represent the mechanism by which P. gingivalis exacerbates atherosclerotic lesions.
Topics: Endothelial Cells; Mitochondria; Mitochondrial Dynamics; Porphyromonas gingivalis
PubMed: 34475379
DOI: 10.1038/s41368-021-00134-4 -
Redox Biology May 2021Increasing lines of evidence identified that dexmedetomidine (DEX) exerted protective effects against sepsis-stimulated acute lung injury via anti-inflammation,...
Dexmedetomidine ameliorates endotoxin-induced acute lung injury in vivo and in vitro by preserving mitochondrial dynamic equilibrium through the HIF-1a/HO-1 signaling pathway.
Increasing lines of evidence identified that dexmedetomidine (DEX) exerted protective effects against sepsis-stimulated acute lung injury via anti-inflammation, anti-oxidation and anti-apoptosis. However, the mechanisms remain unclear. Herein, we investigated whether DEX afforded lung protection by regulating the process of mitochondrial dynamics through the HIF-1a/HO-1 pathway in vivo and in vitro. Using C57BL/6J mice exposed to lipopolysaccharide, it was initially observed that preemptive administration of DEX (50μg/kg) alleviated lung pathologic injury, reduced oxidative stress indices (OSI), improved mitochondrial dysfunction, upregulated the expression of HIF-1α and HO-1, accompanied by shifting the dynamic course of mitochondria into fusion. Moreover, HO-1-knockout mice or HO-1 siRNA transfected NR8383 cells were pretreated with HIF-1α stabilizer DMOG and DEX to validate the effect of HIF-1a/HO-1 pathway on DEX-mediated mitochondrial dynamics in a model of endotoxin-induced lung injury. We found that pretreatment with DEX and DMOG distinctly relieved lung injury, decreased the levels of mitochondrial ROS and mtDNA, reduced OSI, increased nuclear accumulation of HIF-1a and HO-1 protein in wild type mice but not HO-1 KO mice. Similar observations were recapitulated in NC siRNA transfected NR8383 cells after LPS stimulation but not HO-1 siRNA transfected cells. Concertedly, DEX reversed the impaired mitochondrial morphology in LPS stimulated-wild type mice or NC siRNA transfected NR8383 cells, upregulated the expression of mitochondrial fusion protein, while downregulated the expression of fission protein in HIF-1a/HO-1 dependent pathway. Altogether, our data both in vivo and in vitro certified that DEX treatment ameliorated endotoxin-induced acute lung injury by preserving the dynamic equilibrium of mitochondrial fusion/fission through the regulation of HIF-1a/HO-1 signaling pathway.
Topics: Acute Lung Injury; Animals; Dexmedetomidine; Endotoxins; Lipopolysaccharides; Mice; Mice, Inbred C57BL; Mitochondrial Dynamics; Oxidative Stress; Rats; Rats, Sprague-Dawley; Signal Transduction
PubMed: 33774474
DOI: 10.1016/j.redox.2021.101954 -
Molecular Cell Sep 2021Mitochondrial dynamics regulated by mitochondrial fusion and fission maintain mitochondrial functions, whose alterations underline various human diseases. Here, we show...
Mitochondrial dynamics regulated by mitochondrial fusion and fission maintain mitochondrial functions, whose alterations underline various human diseases. Here, we show that inositol is a critical metabolite directly restricting AMPK-dependent mitochondrial fission independently of its classical mode as a precursor for phosphoinositide generation. Inositol decline by IMPA1/2 deficiency elicits AMPK activation and mitochondrial fission without affecting ATP level, whereas inositol accumulation prevents AMPK-dependent mitochondrial fission. Metabolic stress or mitochondrial damage causes inositol decline in cells and mice to elicit AMPK-dependent mitochondrial fission. Inositol directly binds to AMPKγ and competes with AMP for AMPKγ binding, leading to restriction of AMPK activation and mitochondrial fission. Our study suggests that the AMP/inositol ratio is a critical determinant for AMPK activation and establishes a model in which AMPK activation requires inositol decline to release AMPKγ for AMP binding. Hence, AMPK is an inositol sensor, whose inactivation by inositol serves as a mechanism to restrict mitochondrial fission.
Topics: AMP-Activated Protein Kinases; Animals; Cell Line; Humans; Inositol; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitochondria; Mitochondrial Dynamics; PC-3 Cells; Phosphoric Monoester Hydrolases; Phosphorylation; Stress, Physiological
PubMed: 34547240
DOI: 10.1016/j.molcel.2021.08.025 -
Cellular and Molecular Life Sciences :... Jun 2022Germ cell formation and embryonic development require ATP synthesized by mitochondria. The dynamic system of the mitochondria, and in particular, the fusion of... (Review)
Review
Germ cell formation and embryonic development require ATP synthesized by mitochondria. The dynamic system of the mitochondria, and in particular, the fusion of mitochondria, are essential for the generation of energy. Mitofusin1 and mitofusin2, the homologues of Fuzzy onions in yeast and Drosophila, are critical regulators of mitochondrial fusion in mammalian cells. Since their discovery mitofusins (Mfns) have been the source of significant interest as key influencers of mitochondrial dynamics, including membrane fusion, mitochondrial distribution, and the interaction with other organelles. Emerging evidence has revealed significant insight into the role of Mfns in germ cell formation and embryonic development, as well as the high incidence of reproductive diseases such as asthenospermia, polycystic ovary syndrome, and gestational diabetes mellitus. Here, we describe the key mechanisms of Mfns in mitochondrial dynamics, focusing particularly on the role of Mfns in the regulation of mammalian fertility, including spermatogenesis, oocyte maturation, and embryonic development. We also highlight the role of Mfns in certain diseases associated with the reproductive system and their potential as therapeutic targets.
Topics: Animals; Drosophila; Female; Fertility; GTP Phosphohydrolases; Male; Mammals; Membrane Fusion; Mitochondria; Mitochondrial Dynamics; Mitochondrial Proteins
PubMed: 35725948
DOI: 10.1007/s00018-022-04386-z -
Proceedings of the National Academy of... Jan 2023Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise...
Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size, and function. Here we have investigated the role of mitochondrial dynamics during exercise in the model organism . We show that in body-wall muscle, a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and physical fitness decline that occur with aging. Maintenance of proper mitochondrial dynamics is essential for physical fitness, its enhancement by exercise training, and exercise-induced remodeling of the proteome. Surprisingly, among the long-lived genotypes we analyzed (,, , , and ), constitutive activation of AMP-activated protein kinase (AMPK) uniquely preserves physical fitness during aging, a benefit that is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for physical fitness to be enhanced by exercise, with our findings together suggesting that exercise may enhance muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining physical fitness and exercise responsiveness during aging and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging.
Topics: Animals; Mitochondrial Dynamics; AMP-Activated Protein Kinases; Aging; Caenorhabditis elegans; Exercise; Physical Fitness; Muscle, Skeletal
PubMed: 36595699
DOI: 10.1073/pnas.2204750120 -
Journal of Biochemistry Mar 2020The mitochondrion is an essential organelle for a wide range of cellular processes, including energy production, metabolism, signal transduction and cell death. To... (Review)
Review
The mitochondrion is an essential organelle for a wide range of cellular processes, including energy production, metabolism, signal transduction and cell death. To execute these functions, mitochondria regulate their size, number, morphology and distribution in cells via mitochondrial division and fusion. In addition, mitochondrial division and fusion control the autophagic degradation of dysfunctional mitochondria to maintain a healthy population. Defects in these dynamic membrane processes are linked to many human diseases that include metabolic syndrome, myopathy and neurodegenerative disorders. In the last several years, our fundamental understanding of mitochondrial fusion, division and degradation has been significantly advanced by high resolution structural analyses, protein-lipid biochemistry, super resolution microscopy and in vivo analyses using animal models. Here, we summarize and discuss this exciting recent progress in the mechanism and function of mitochondrial division and fusion.
Topics: Actins; Animals; Dynamins; Endoplasmic Reticulum; GTP Phosphohydrolases; Humans; Lipid Metabolism; Mitochondria; Mitochondrial Dynamics; Mitophagy
PubMed: 31800050
DOI: 10.1093/jb/mvz106 -
Scientific Reports Apr 2024Mitochondria, the powerhouse and the vital signaling hub of the cell, participate in a variety of biological processes, such as apoptosis, redox responses, cell...
Mitochondria, the powerhouse and the vital signaling hub of the cell, participate in a variety of biological processes, such as apoptosis, redox responses, cell senescence, autophagy, and iron homeostasis. Mitochondria form a mostly tubular network, made up of an outer and a cristeae-forming inner membrane. The network undergoes dynamic fusion and fission that change its morphological structure according to the functional needs. Approximately 1500 mitochondrial proteins encoded by nuclear genome plus over 10 proteins encoded by mitochondrial DNA are folded and assembled in the mitochondria under a high-fidelity control system. These proteins are involved in oxidative phosphorylation, metabolism, network and cristae dynamics, mitophagy, import machinery, ion channels, and mitochondrial DNA maintenance. This Collection gathers original research that advances our understanding of the monitoring techniques and pathophysiological significance of mitochondrial dynamics in health and disease.
Topics: Mitochondrial Dynamics; Humans; Mitochondria; Animals
PubMed: 38688939
DOI: 10.1038/s41598-024-59998-1