RESUMO
Clearance of apoptotic cells (ACs) by phagocytes (efferocytosis) prevents post-apoptotic necrosis and dampens inflammation. Defective efferocytosis drives important diseases, including atherosclerosis. For efficient efferocytosis, phagocytes must be able to internalize multiple ACs. We show here that uptake of multiple ACs by macrophages requires dynamin-related protein 1 (Drp1)-mediated mitochondrial fission, which is triggered by AC uptake. When mitochondrial fission is disabled, AC-induced increase in cytosolic calcium is blunted owing to mitochondrial calcium sequestration, and calcium-dependent phagosome formation around secondarily encountered ACs is impaired. These defects can be corrected by silencing the mitochondrial calcium uniporter (MCU). Mice lacking myeloid Drp1 showed defective efferocytosis and its pathologic consequences in the thymus after dexamethasone treatment and in advanced atherosclerotic lesions in fat-fed Ldlr-/- mice. Thus, mitochondrial fission in response to AC uptake is a critical process that enables macrophages to clear multiple ACs and to avoid the pathologic consequences of defective efferocytosis in vivo.
Assuntos
Macrófagos/citologia , Dinâmica Mitocondrial , Animais , Apoptose , Humanos , Macrófagos/metabolismo , Camundongos , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias/metabolismo , Células Mieloides/metabolismo , Fagócitos/metabolismo , Fagossomos/metabolismoRESUMO
Splicing is a central RNA-based process commonly altered in human cancers; however, how spliceosomal components are co-opted during tumorigenesis remains poorly defined. Here we unravel the core splice factor SF3A3 at the nexus of a translation-based program that rewires splicing during malignant transformation. Upon MYC hyperactivation, SF3A3 levels are modulated translationally through an RNA stem-loop in an eIF3D-dependent manner. This ensures accurate splicing of mRNAs enriched for mitochondrial regulators. Altered SF3A3 translation leads to metabolic reprogramming and stem-like properties that fuel MYC tumorigenic potential in vivo. Our analysis reveals that SF3A3 protein levels predict molecular and phenotypic features of aggressive human breast cancers. These findings unveil a post-transcriptional interplay between splicing and translation that governs critical facets of MYC-driven oncogenesis.
Assuntos
Neoplasias da Mama/metabolismo , Carcinogênese/metabolismo , Células-Tronco Neoplásicas/metabolismo , Biossíntese de Proteínas , Fatores de Processamento de RNA/biossíntese , Spliceossomos/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Carcinogênese/genética , Feminino , Humanos , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Fatores de Processamento de RNA/genética , Spliceossomos/genéticaRESUMO
Mitochondria are highly dynamic organelles that continuously grow, divide, and fuse. The division of mitochondria is crucial for human health. During mitochondrial division, the mechano-guanosine triphosphatase (GTPase) dynamin-related protein (Drp1) severs mitochondria at endoplasmic reticulum (ER)-mitochondria contact sites, where peripheral ER tubules interact with mitochondria. Here, we report that Drp1 directly shapes peripheral ER tubules in human and mouse cells. This ER-shaping activity is independent of GTP hydrolysis and located in a highly conserved peptide of 18 amino acids (termed D-octadecapeptide), which is predicted to form an amphipathic α helix. Synthetic D-octadecapeptide tubulates liposomes in vitro and the ER in cells. ER tubules formed by Drp1 promote mitochondrial division by facilitating ER-mitochondria interactions. Thus, Drp1 functions as a two-in-one protein during mitochondrial division, with ER tubulation and mechano-GTPase activities.
Assuntos
Dinaminas/metabolismo , Dinaminas/fisiologia , Retículo Endoplasmático/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Guanosina Trifosfato/metabolismo , Mitocôndrias/metabolismo , Animais , Dinaminas/genética , Retículo Endoplasmático/efeitos dos fármacos , GTP Fosfo-Hidrolases/genética , Humanos , Camundongos , Camundongos Knockout , Mitocôndrias/efeitos dos fármacos , Dinâmica Mitocondrial , Oligopeptídeos/farmacologiaRESUMO
Mitochondrial morphology shifts rapidly to manage cellular metabolism, organelle integrity, and cell fate. It remains unknown whether innate nucleic acid sensing, the central and general mechanisms of monitoring both microbial invasion and cellular damage, can reprogram and govern mitochondrial dynamics and function. Here, we unexpectedly observed that upon activation of RIG-I-like receptor (RLR)-MAVS signaling, TBK1 directly phosphorylated DRP1/DNM1L, which disabled DRP1, preventing its high-order oligomerization and mitochondrial fragmentation function. The TBK1-DRP1 axis was essential for assembly of large MAVS aggregates and healthy antiviral immunity and underlay nutrient-triggered mitochondrial dynamics and cell fate determination. Knockin (KI) strategies mimicking TBK1-DRP1 signaling produced dominant-negative phenotypes reminiscent of human DRP1 inborn mutations, while interrupting the TBK1-DRP1 connection compromised antiviral responses. Thus, our findings establish an unrecognized function of innate immunity governing both morphology and physiology of a major organelle, identify a lacking loop during innate RNA sensing, and report an elegant mechanism of shaping mitochondrial dynamics.
Assuntos
Dinaminas/metabolismo , Mitocôndrias/fisiologia , Proteínas Serina-Treonina Quinases/metabolismo , RNA/metabolismo , Peixe-Zebra/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Proteína DEAD-box 58/genética , Proteína DEAD-box 58/metabolismo , Dinaminas/genética , Células HCT116 , Células HEK293 , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Mutação , Proteínas Serina-Treonina Quinases/genética , RNA/genética , Transdução de Sinais/genética , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
Mitochondrial morphology dynamics regulate signaling pathways during epithelial cell formation and differentiation. The mitochondrial fission protein Drp1 affects the appropriate activation of EGFR and Notch signaling-driven differentiation of posterior follicle cells in Drosophila oogenesis. The mechanisms by which Drp1 regulates epithelial polarity during differentiation are not known. In this study, we show that Drp1-depleted follicle cells are constricted in early stages and present in multiple layers at later stages with decreased levels of apical polarity protein aPKC. These defects are suppressed by additional depletion of mitochondrial fusion protein Opa1. Opa1 depletion leads to mitochondrial fragmentation and increased reactive oxygen species (ROS) in follicle cells. We find that increasing ROS by depleting the ROS scavengers, mitochondrial SOD2 and catalase also leads to mitochondrial fragmentation. Further, the loss of Opa1, SOD2 and catalase partially restores the defects in epithelial polarity and aPKC, along with EGFR and Notch signaling in Drp1-depleted follicle cells. Our results show a crucial interaction between mitochondrial morphology, ROS generation and epithelial cell polarity formation during the differentiation of follicle epithelial cells in Drosophila oogenesis.
Assuntos
Drosophila , Dinâmica Mitocondrial , Animais , Drosophila/genética , Drosophila/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Dinâmica Mitocondrial/genética , Catalase , Receptores ErbB/genética , Receptores ErbB/metabolismo , Dinaminas/genética , Dinaminas/metabolismo , Proteínas Mitocondriais/metabolismoRESUMO
Mitophagy, a mitochondrial quality control process for eliminating dysfunctional mitochondria, can be induced by a response of dynamin-related protein 1 (Drp1) to a reduction in mitochondrial membrane potential (MMP) and mitochondrial division. However, the coordination between MMP and mitochondrial division for selecting the damaged portion of the mitochondrial network is less understood. Here, we found that MMP is reduced focally at a fission site by the Drp1 recruitment, which is initiated by the interaction of Drp1 with mitochondrial zinc transporter Zip1 and Zn2+ entry through the Zip1-MCU complex. After division, healthy mitochondria restore MMP levels and participate in the fusion-fission cycle again, but mitochondria that fail to restore MMP undergo mitophagy. Thus, interfering with the interaction between Drp1 and Zip1 blocks the reduction of MMP and the subsequent mitophagic selection of damaged mitochondria. These results suggest that Drp1-dependent fission provides selective pressure for eliminating "bad sectors" in the mitochondrial network, serving as a mitochondrial quality surveillance system.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias/metabolismo , Dinâmica Mitocondrial , Proteínas Mitocondriais/metabolismo , Mitofagia , Trifosfato de Adenosina/metabolismo , Animais , Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Proteínas de Transporte de Cátions/genética , Córtex Cerebral/metabolismo , Córtex Cerebral/patologia , Dinaminas , Metabolismo Energético , GTP Fosfo-Hidrolases/genética , Células HEK293 , Células HeLa , Humanos , Potencial da Membrana Mitocondrial , Proteínas Associadas aos Microtúbulos/genética , Mitocôndrias/genética , Mitocôndrias/patologia , Proteínas Mitocondriais/genética , Mutação , Neurônios/metabolismo , Neurônios/patologia , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Ratos Sprague-Dawley , Transdução de Sinais , Fatores de Tempo , Zinco/metabolismoRESUMO
Mitochondrial fission is a tightly regulated process involving multiple proteins and cell signaling. Despite extensive studies on mitochondrial fission factors, our understanding of the regulatory mechanisms remains limited. This study shows the critical role of a mitochondrial GTPase, GTPBP8, in orchestrating mitochondrial fission in mammalian cells. Depletion of GTPBP8 resulted in drastic elongation and interconnectedness of mitochondria. Conversely, overexpression of GTPBP8 shifted mitochondrial morphology from tubular to fragmented. Notably, the induced mitochondrial fragmentation from GTPBP8 overexpression was inhibited in cells either depleted of the mitochondrial fission protein Drp1 (also known as DNM1L) or carrying mutated forms of Drp1. Importantly, downregulation of GTPBP8 caused an increase in oxidative stress, modulating cell signaling involved in the increased phosphorylation of Drp1 at Ser637. This phosphorylation hindered the recruitment of Drp1 to mitochondria, leading to mitochondrial fission defects. By contrast, GTPBP8 overexpression triggered enhanced recruitment and assembly of Drp1 at mitochondria. In summary, our study illuminates the cellular function of GTPBP8 as a pivotal modulator of the mitochondrial division apparatus, inherently reliant on its influence on Drp1.
Assuntos
Dinaminas , Proteínas Associadas aos Microtúbulos , Mitocôndrias , Dinâmica Mitocondrial , Proteínas Monoméricas de Ligação ao GTP , Humanos , Dinaminas/metabolismo , Dinaminas/genética , GTP Fosfo-Hidrolases/metabolismo , GTP Fosfo-Hidrolases/genética , Proteínas de Ligação ao GTP/metabolismo , Proteínas de Ligação ao GTP/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Estresse Oxidativo , Fosforilação , Proteínas Monoméricas de Ligação ao GTP/genética , Proteínas Monoméricas de Ligação ao GTP/metabolismoRESUMO
Aberrant mitochondrial fission/fusion dynamics are frequently associated with pathologies, including cancer. We show that alternative splice variants of the fission protein Drp1 (DNM1L) contribute to the complexity of mitochondrial fission/fusion regulation in tumor cells. High tumor expression of the Drp1 alternative splice variant lacking exon 16 relative to other transcripts is associated with poor outcome in ovarian cancer patients. Lack of exon 16 results in Drp1 localization to microtubules and decreased association with mitochondrial fission sites, culminating in fused mitochondrial networks, enhanced respiration, changes in metabolism, and enhanced pro-tumorigenic phenotypes in vitro and in vivo. These effects are inhibited by siRNAs designed to specifically target the endogenously expressed transcript lacking exon 16. Moreover, lack of exon 16 abrogates mitochondrial fission in response to pro-apoptotic stimuli and leads to decreased sensitivity to chemotherapeutics. These data emphasize the pathophysiological importance of Drp1 alternative splicing, highlight the divergent functions and consequences of changing the relative expression of Drp1 splice variants in tumor cells, and strongly warrant consideration of alternative splicing in future studies focused on Drp1.
RESUMO
The continuous dynamic reshaping of mitochondria by fusion and fission events is critical to keep mitochondrial quality and function under control in response to changes in energy and stress. Maintaining a functional, highly interconnected mitochondrial reticulum ensures rapid energy production and distribution. Moreover, mitochondrial networks act as dynamic signaling hub to adapt to the metabolic demands imposed by contraction, energy expenditure, and general metabolism. However, excessive mitochondrial fusion or fission results in the disruption of the skeletal muscle mitochondrial network integrity and activates a retrograde response from mitochondria to the nucleus, leading to muscle atrophy, weakness and influencing whole-body homeostasis. These actions are mediated via the secretion of mitochondrial-stress myokines such as FGF21 and GDF15. Here we will summarize recent discoveries in the role of mitochondrial fusion and fission in the control of muscle mass and in regulating physiological homeostasis and disease progression.
Assuntos
Mitocôndrias Musculares , Dinâmica Mitocondrial , Músculo Esquelético , Músculo Esquelético/metabolismo , Mitocôndrias Musculares/fisiologia , HumanosRESUMO
Dynamin-related proteins (Drps) mediate a variety of membrane remodelling processes. The Saccharomyces cerevisiae Drp, Vps1, is required for endocytosis, endosomal sorting, vacuole fusion, and peroxisome fission and breakdown. How Drps, and in particular Vps1, can function at so many different subcellular locations is of interest to our understanding of cellular organisation. We found that the peroxisomal membrane protein Pex27 is specifically required for Vps1-dependent peroxisome fission in proliferating cells but is not required for Dnm1-dependent peroxisome fission. Pex27 accumulates in constricted regions of peroxisomes and affects peroxisome geometry upon overexpression. Moreover, Pex27 physically interacts with Vps1 in vivo and is required for the accumulation of a GTPase-defective Vps1 mutant (K42A) on peroxisomes. During nitrogen starvation, a condition that halts cell division and induces peroxisome breakdown, Vps1 associates with the pexophagophore. Pex27 is neither required for Vps1 recruitment to the pexophagophore nor for pexophagy. Our study identifies Pex27 as a Vps1-specific partner for the maintenance of peroxisome number in proliferating yeast cells.
Assuntos
Peroxissomos , Proteínas de Saccharomyces cerevisiae , Peroxissomos/metabolismo , Proteínas de Transporte Vesicular/genética , Proteínas de Transporte Vesicular/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Dinaminas/metabolismo , Membranas Intracelulares/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Mitochondria and peroxisomes are dynamic signaling organelles that constantly undergo fission, driven by the large GTPase dynamin-related protein 1 (DRP1; encoded by DNM1L). Patients with de novo heterozygous missense mutations in DNM1L present with encephalopathy due to defective mitochondrial and peroxisomal fission (EMPF1) - a devastating neurodevelopmental disease with no effective treatment. To interrogate the mechanisms by which DRP1 mutations cause cellular dysfunction, we used human-derived fibroblasts from patients who present with EMPF1. In addition to elongated mitochondrial morphology and lack of fission, patient cells display lower coupling efficiency, increased proton leak and upregulation of glycolysis. Mitochondrial hyperfusion also results in aberrant cristae structure and hyperpolarized mitochondrial membrane potential. Peroxisomes show a severely elongated morphology in patient cells, which is associated with reduced respiration when cells are reliant on fatty acid oxidation. Metabolomic analyses revealed impaired methionine cycle and synthesis of pyrimidine nucleotides. Our study provides insight into the role of mitochondrial dynamics in cristae maintenance and the metabolic capacity of the cell, as well as the disease mechanism underlying EMPF1.
Assuntos
Encefalopatias , Dinaminas , Humanos , Potencial da Membrana Mitocondrial/genética , Dinaminas/genética , Dinaminas/metabolismo , Encefalopatias/genética , Encefalopatias/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Mutação/genética , Mitocôndrias/genética , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismoRESUMO
Mitochondrial dynamics regulate the quality and morphology of mitochondria. Calcium (Ca2+) plays an important role in regulating mitochondrial function. Here, we investigated the effects of optogenetically engineered Ca2+ signaling on mitochondrial dynamics. More specifically, customized illumination conditions could trigger unique Ca2+ oscillation waves to trigger specific signaling pathways. In this study, we found that modulating Ca2+ oscillations by increasing the light frequency, intensity and exposure time could drive mitochondria toward the fission state, mitochondrial dysfunction, autophagy and cell death. Moreover, illumination triggered phosphorylation at the Ser616 residue but not the Ser637 residue of the mitochondrial fission protein, dynamin-related protein 1 (DRP1, encoded by DNM1L), via the activation of Ca2+-dependent kinases CaMKII, ERK and CDK1. However, optogenetically engineered Ca2+ signaling did not activate calcineurin phosphatase to dephosphorylate DRP1 at Ser637. In addition, light illumination had no effect on the expression levels of the mitochondrial fusion proteins mitofusin 1 (MFN1) and 2 (MFN2). Overall, this study provides an effective and innovative approach to altering Ca2+ signaling for controlling mitochondrial fission with a more precise resolution than pharmacological approaches in the temporal dimension.
Assuntos
Cálcio , Dinâmica Mitocondrial , Dinâmica Mitocondrial/fisiologia , Cálcio/metabolismo , Dinaminas/genética , Dinaminas/metabolismo , Mitocôndrias/metabolismo , Fosforilação , Morte Celular , Proteínas Mitocondriais/metabolismoRESUMO
The peroxisomal disease adrenoleukodystrophy (X-ALD) is caused by loss of the transporter of very-long-chain fatty acids (VLCFAs), ABCD1. An excess of VLCFAs disrupts essential homeostatic functions crucial for axonal maintenance, including redox metabolism, glycolysis and mitochondrial respiration. As mitochondrial function and morphology are intertwined, we set out to investigate the role of mitochondrial dynamics in X-ALD models. Using quantitative 3D transmission electron microscopy, we revealed mitochondrial fragmentation in corticospinal axons in Abcd1- mice. In patient fibroblasts, an excess of VLCFAs triggers mitochondrial fragmentation through the redox-dependent phosphorylation of DRP1 (DRP1S616). The blockade of DRP1-driven fission by the peptide P110 effectively preserved mitochondrial morphology. Furthermore, mRNA inhibition of DRP1 not only prevented mitochondrial fragmentation but also protected axonal health in a Caenorhabditis elegans model of X-ALD, underscoring DRP1 as a potential therapeutic target. Elevated levels of circulating cell-free mtDNA in patients' CSF align this leukodystrophy with primary mitochondrial disorders. Our findings underscore the intricate interplay between peroxisomal dysfunction, mitochondrial dynamics and axonal integrity in X-ALD, shedding light on potential avenues for therapeutic intervention.
Assuntos
Membro 1 da Subfamília D de Transportadores de Cassetes de Ligação de ATP , Adrenoleucodistrofia , Dinaminas , Dinâmica Mitocondrial , Adrenoleucodistrofia/metabolismo , Adrenoleucodistrofia/patologia , Adrenoleucodistrofia/genética , Animais , Dinâmica Mitocondrial/fisiologia , Humanos , Camundongos , Dinaminas/metabolismo , Dinaminas/genética , Membro 1 da Subfamília D de Transportadores de Cassetes de Ligação de ATP/genética , Caenorhabditis elegans , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Axônios/patologia , Axônios/metabolismo , Fibroblastos/metabolismo , Fibroblastos/patologia , Masculino , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Modelos Animais de Doenças , Tratos Piramidais/patologia , Tratos Piramidais/metabolismo , Fragmentos de Peptídeos , GTP Fosfo-HidrolasesRESUMO
HHATL, previously implicated in cardiac hypertrophy in the zebrafish model, has emerged as a prioritized HCM risk gene. We identified six rare mutations in HHATL, present in 6.94 % of nonsarcomeric HCM patients (5/72). Moreover, a decrease of HHATL in the heart tissue from HCM patients and cardiac hypertrophy mouse model using transverse aortic constriction was observed. Despite this, the precise pathogenic mechanisms underlying HHATL-associated cardiac hypertrophy remain elusive. In this study, we observed that HHATL downregulation in H9C2 cells resulted in elevated expression of hypertrophic markers and reactive oxygen species (ROS), culminating in cardiac hypertrophy and mitochondrial dysfunction. Notably, the bioactive form of SHH, SHHN, exhibited a significant increase, while the mitochondrial fission protein dynamin-like GTPase (DRP1) decreased upon HHATL depletion. Intervention with the SHH inhibitor RU-SKI 43 or DRP1 overexpression effectively prevented Hhatl-depletion-induced cardiac hypertrophy, mitigating disruptions in mitochondrial morphology and membrane potential through the SHH/DRP1 axis. In summary, our findings suggest that HHATL depletion activates SHH signaling, reducing DRP1 levels and thereby promoting the expression of hypertrophic markers, ROS generation, and mitochondrial dysfunction, ultimately leading to cardiac hypertrophy. This study provides additional compelling evidence supporting the association of HHATL with cardiac hypertrophy.
Assuntos
Cardiomegalia , Regulação para Baixo , Dinaminas , Proteínas Hedgehog , Espécies Reativas de Oxigênio , Dinaminas/metabolismo , Dinaminas/genética , Animais , Proteínas Hedgehog/metabolismo , Proteínas Hedgehog/genética , Cardiomegalia/metabolismo , Cardiomegalia/genética , Cardiomegalia/patologia , Espécies Reativas de Oxigênio/metabolismo , Humanos , Regulação para Baixo/genética , Transdução de Sinais , Camundongos , Ratos , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Mitocôndrias/genéticaRESUMO
Podocytes are essential to maintaining the integrity of the glomerular filtration barrier, but they are frequently affected in lupus nephritis (LN). Here, we show that the significant upregulation of Drp1S616 phosphorylation in podocytes promotes mitochondrial fission, leading to mitochondrial dysfunction and podocyte injury in LN. Inhibition or knockdown of Drp1 promotes mitochondrial fusion and protects podocytes from injury induced by LN serum. In vivo, pharmacological inhibition of Drp1 reduces the phosphorylation of Drp1S616 in podocytes in lupus-prone mice. Podocyte injury is reversed when Drp1 is inhibited, resulting in the alleviation of proteinuria. Mechanistically, complement component C5a (C5a) upregulates the phosphorylation of Drp1S616 and promotes mitochondrial fission in podocytes. Moreover, the expression of C5a receptor 1 (C5aR1) is notably upregulated in podocytes in LN. C5a-C5aR1 axis-controlled phosphorylation of Drp1S616 and mitochondrial fission are substantially suppressed when C5aR1 is knocked down by siRNA. Moreover, lupus-prone mice treated with C5aR inhibitor show reduced phosphorylation of Drp1S616 in podocytes, resulting in significantly less podocyte damage. Together, this study uncovers a novel mechanism by which the C5a-C5aR1 axis promotes podocyte injury by enhancing Drp1-mediated mitochondrial fission, which could have significant implications for the treatment of LN.
Assuntos
Complemento C5a , Dinaminas , Nefrite Lúpica , Dinâmica Mitocondrial , Podócitos , Receptor da Anafilatoxina C5a , Podócitos/metabolismo , Podócitos/patologia , Nefrite Lúpica/metabolismo , Nefrite Lúpica/patologia , Nefrite Lúpica/etiologia , Animais , Receptor da Anafilatoxina C5a/metabolismo , Receptor da Anafilatoxina C5a/genética , Camundongos , Dinaminas/metabolismo , Dinaminas/genética , Complemento C5a/metabolismo , Humanos , Fosforilação , Modelos Animais de Doenças , Mitocôndrias/metabolismo , Transdução de Sinais , FemininoRESUMO
The mechanisms that link environmental and intracellular stimuli to mitochondrial functions, including fission/fusion, ATP production, metabolite biogenesis, and apoptosis, are not well understood. Here, we demonstrate that the nutrient-sensing mechanistic/mammalian target of rapamycin complex 1 (mTORC1) stimulates translation of mitochondrial fission process 1 (MTFP1) to control mitochondrial fission and apoptosis. Expression of MTFP1 is coupled to pro-fission phosphorylation and mitochondrial recruitment of the fission GTPase dynamin-related protein 1 (DRP1). Potent active-site mTOR inhibitors engender mitochondrial hyperfusion due to the diminished translation of MTFP1, which is mediated by translation initiation factor 4E (eIF4E)-binding proteins (4E-BPs). Uncoupling MTFP1 levels from the mTORC1/4E-BP pathway upon mTOR inhibition blocks the hyperfusion response and leads to apoptosis by converting mTOR inhibitor action from cytostatic to cytotoxic. These data provide direct evidence for cell survival upon mTOR inhibition through mitochondrial hyperfusion employing MTFP1 as a critical effector of mTORC1 to govern cell fate decisions.
Assuntos
Proteínas de Membrana/metabolismo , Mitocôndrias/enzimologia , Dinâmica Mitocondrial , Serina-Treonina Quinases TOR/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Apoptose , Sistemas CRISPR-Cas , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Sobrevivência Celular , Dinaminas/genética , Dinaminas/metabolismo , Fatores de Iniciação em Eucariotos/genética , Fatores de Iniciação em Eucariotos/metabolismo , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina , Proteínas de Membrana/genética , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/ultraestrutura , Dinâmica Mitocondrial/efeitos dos fármacos , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilação , Inibidores de Proteínas Quinases/farmacologia , Interferência de RNA , Transdução de Sinais , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/genética , TransfecçãoRESUMO
Mitochondria have their own DNA (mtDNA), which encodes essential respiratory subunits. Under live imaging, mitochondrial nucleoids, composed of several copies of mtDNA and DNA-binding proteins, such as mitochondrial transcription factor A (TFAM), actively move inside mitochondria and change the morphology, in concert with mitochondrial membrane fission. Here we found the mitochondrial inner membrane-anchored AAA-ATPase protein ATAD3A mediates the nucleoid dynamics. Its ATPase domain exposed to the matrix binds directly to TFAM and mediates nucleoid trafficking along mitochondria by ATP hydrolysis. Nucleoid trafficking also required ATAD3A oligomerization via an interaction between the coiled-coil domains in intermembrane space. In ATAD3A deficiency, impaired nucleoid trafficking repressed the clustered and enlarged nucleoids observed in mitochondrial fission-deficient cells resulted in dispersed distribution of small nucleoids observed throughout the mitochondrial network, and this enhanced respiratory complex formation. Thus, mitochondrial fission and nucleoid trafficking cooperatively determine the size, number, and distribution of nucleoids in mitochondrial network, which should modulate respiratory complex formation.
Assuntos
Mitocôndrias , Proteínas Mitocondriais , ATPases Associadas a Diversas Atividades Celulares/genética , ATPases Associadas a Diversas Atividades Celulares/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Dinâmica Mitocondrial/genética , DNA Mitocondrial/genéticaRESUMO
Celastrol, a bioactive molecule extracted from the plant Tripterygium wilfordii Hook F., possesses anti-inflammatory, anti-obesity and anti-tumour properties. Despite its efficacy in improving erythema and scaling in psoriatic mice, the specific therapeutic mechanism of celastrol in atopic dermatitis (AD) remains unknown. This study aims to examine the role and mechanism of celastrol in AD using TNF-α-stimulated HaCaT cells and DNCB-induced Balb/c mice as in vitro and in vivo AD models, respectively. Celastrol was found to inhibit the increased epidermal thickness, reduce spleen and lymph node weights, attenuate inflammatory cell infiltration and mast cell degranulation and decrease thymic stromal lymphopoietin (TSLP) as well as various inflammatory factors (IL-4, IL-13, TNF-α, IL-5, IL-31, IL-33, IgE, TSLP, IL-17, IL-23, IL-1ß, CCL11 and CCL17) in AD mice. Additionally, celastrol inhibited Ezrin phosphorylation at Thr567, restored mitochondrial network structure, promoted translocation of Drp1 to the cytoplasm and reduced TNF-α-induced cellular reactive oxygen species (ROS), mitochondrial ROS (mtROS) and mitochondrial membrane potential (MMP) production. Interestingly, Mdivi-1 (a mitochondrial fission inhibitor) and Ezrin-specific siRNAs lowered inflammatory factor levels and restored mitochondrial reticular formation, as well as ROS, mtROS and MMP production. Co-immunoprecipitation revealed that Ezrin interacted with Drp1. Knocking down Ezrin reduced mitochondrial fission protein Drp1 phosphorylation and Fis1 expression while increasing the expression of fusion proteins Mfn1 and Mfn2. The regulation of mitochondrial fission and fusion by Ezrin was confirmed. Overall, celastrol may alleviate AD by regulating Ezrin-mediated mitochondrial fission and fusion, which may become a novel therapeutic reagent for alleviating AD.
Assuntos
Citocinas , Proteínas do Citoesqueleto , Dermatite Atópica , Camundongos Endogâmicos BALB C , Dinâmica Mitocondrial , Triterpenos Pentacíclicos , Triterpenos , Animais , Dinâmica Mitocondrial/efeitos dos fármacos , Triterpenos Pentacíclicos/farmacologia , Dermatite Atópica/tratamento farmacológico , Dermatite Atópica/patologia , Dermatite Atópica/metabolismo , Humanos , Triterpenos/farmacologia , Camundongos , Citocinas/metabolismo , Proteínas do Citoesqueleto/metabolismo , Proteínas do Citoesqueleto/genética , Linfopoietina do Estroma do Timo , Modelos Animais de Doenças , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Células HaCaT , Fosforilação/efeitos dos fármacosRESUMO
Tumor necrosis factor α (TNFα), a proinflammatory cytokine, plays a significant role in mediating the effects of acute inflammation in response to allergens, pollutants, and respiratory infections. Previously, we showed that acute exposure to TNFα induces mitochondrial fragmentation in human airway smooth muscle (hASM) cells, which is associated with increased expression of dynamin-related protein 1 (DRP1). Phosphorylation of DRP1 at serine 616 (pDRP1S616) promotes its translocation and binding to the outer mitochondrial membrane (OMM) and mediates mitochondrial fragmentation. Previously, we reported that TNFα exposure triggers protein unfolding and triggers an endoplasmic reticulum (ER) stress response involving phosphorylation of inositol-requiring enzyme 1α (pIRE1α) at serine 724 (pIRE1αS724) and subsequent splicing of X-box binding protein 1 (XBP1s) in hASM cells. We hypothesize that TNFα-mediated activation of the pIRE1αS724/XBP1s ER stress pathway in hASM cells transcriptionally activates genes that encode kinases responsible for pDRP1S616 phosphorylation. Using 3-D confocal imaging of MitoTracker green-labeled mitochondria, we found that TNFα treatment for 6 h induces mitochondrial fragmentation in hASM cells. We also confirmed that 6 h TNFα treatment activates the pIRE1α/XBP1s ER stress pathway. Using in silico analysis and ChIP assay, we showed that CDK1 and CDK5, kinases involved in the phosphorylation of pDRP1S616, are transcriptionally targeted by XBP1s. TNFα treatment increased the binding affinity of XBP1s on the promoter regions of CDK1 and CDK5, and this was associated with an increase in pDRP1S616 and mitochondria fragmentation. This study reveals a new underlying molecular mechanism for TNFα-induced mitochondrial fragmentation in hASM cells.NEW & NOTEWORTHY Airway inflammation is increasing worldwide. Proinflammatory cytokines mediate an adaptive mechanism to overcome inflammation-induced cellular stress. Previously, we reported that TNFα mediates hASM cellular responses, leading to increased force and ATP consumption associated with increased O2 consumption, and oxidative stress. This study indicates that TNFα induces ER stress, which induces mitochondrial fragmentation via pIRE1αS724/XBP1s mediated CDK1/5 upregulation and pDRP1S616 phosphorylation. Mitochondrial fragmentation may promote hASM mitochondrial biogenesis to maintain healthy mitochondrial pool.
Assuntos
Citocinas , Fator de Necrose Tumoral alfa , Humanos , Fator de Necrose Tumoral alfa/metabolismo , Fosforilação , Citocinas/metabolismo , Miócitos de Músculo Liso/metabolismo , Inflamação , Serina/metabolismoRESUMO
Neuroinflammation and mitochondrial dysfunction are closely intertwined with the pathophysiology of neurological disorders. Recent studies have elucidated profound alterations in mitochondrial dynamics across a spectrum of neurological disorders. Dynamin-related protein 1 (DRP1) emerges as a pivotal regulator of mitochondrial fission, with its dysregulation disrupting mitochondrial homeostasis and fueling neuroinflammation, thereby exacerbating disease severity. In addition to its role in mitochondrial dynamics, DRP1 plays a crucial role in modulating inflammation-related pathways. This review synthesizes important functions of DRP1 in the central nervous system (CNS) and the impact of epigenetic modification on the progression of neurodegenerative diseases. The intricate interplay between neuroinflammation and DRP1 in microglia and astrocytes, central contributors to neuroinflammation, is expounded upon. Furthermore, the use of DRP1 inhibitors to influence the activation of microglia and astrocytes, as well as their involvement in processes such as mitophagy, mitochondrial oxidative stress, and calcium ion transport in CNS-mediated neuroinflammation, is scrutinized. The modulation of microglia to astrocyte crosstalk by DRP1 and its role in inflammatory neurodegeneration is also highlighted. Overall, targeting DRP1 presents a promising avenue for ameliorating neuroinflammation and enhancing the therapeutic management of neurological disorders.