RESUMO
Activated effector T (TE) cells augment anabolic pathways of metabolism, such as aerobic glycolysis, while memory T (TM) cells engage catabolic pathways, like fatty acid oxidation (FAO). However, signals that drive these differences remain unclear. Mitochondria are metabolic organelles that actively transform their ultrastructure. Therefore, we questioned whether mitochondrial dynamics controls T cell metabolism. We show that TE cells have punctate mitochondria, while TM cells maintain fused networks. The fusion protein Opa1 is required for TM, but not TE cells after infection, and enforcing fusion in TE cells imposes TM cell characteristics and enhances antitumor function. Our data suggest that, by altering cristae morphology, fusion in TM cells configures electron transport chain (ETC) complex associations favoring oxidative phosphorylation (OXPHOS) and FAO, while fission in TE cells leads to cristae expansion, reducing ETC efficiency and promoting aerobic glycolysis. Thus, mitochondrial remodeling is a signaling mechanism that instructs T cell metabolic programming.
Assuntos
Dinâmica Mitocondrial , Linfócitos T/citologia , Linfócitos T/metabolismo , Animais , Diferenciação Celular , Transporte de Elétrons , Ácidos Graxos/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Glicólise , Humanos , Memória Imunológica , Camundongos , Camundongos Endogâmicos C57BL , Oxirredução , Transdução de Sinais , Linfócitos T/imunologiaRESUMO
Mitochondrial membranes define distinct structural and functional compartments. Cristae of the inner mitochondrial membrane (IMM) function as independent bioenergetic units that undergo rapid and transient remodelling, but the significance of this compartmentalized organization is unknown1. Using super-resolution microscopy, here we show that cytosolic IMM vesicles, devoid of outer mitochondrial membrane or mitochondrial matrix, are formed during resting state. These vesicles derived from the IMM (VDIMs) are formed by IMM herniation through pores formed by voltage-dependent anion channel 1 in the outer mitochondrial membrane. Live-cell imaging showed that lysosomes in proximity to mitochondria engulfed the herniating IMM and, aided by the endosomal sorting complex required for transport machinery, led to the formation of VDIMs in a microautophagy-like process, sparing the remainder of the organelle. VDIM formation was enhanced in mitochondria undergoing oxidative stress, suggesting their potential role in maintenance of mitochondrial function. Furthermore, the formation of VDIMs required calcium release by the reactive oxygen species-activated, lysosomal calcium channel, transient receptor potential mucolipin 1, showing an interorganelle communication pathway for maintenance of mitochondrial homeostasis. Thus, IMM compartmentalization could allow for the selective removal of damaged IMM sections via VDIMs, which should protect mitochondria from localized injury. Our findings show a new pathway of intramitochondrial quality control.
Assuntos
Cálcio , Lisossomos , Mitocôndrias , Membranas Mitocondriais , Estresse Oxidativo , Lisossomos/metabolismo , Humanos , Membranas Mitocondriais/metabolismo , Cálcio/metabolismo , Mitocôndrias/metabolismo , Canal de Ânion 1 Dependente de Voltagem/metabolismo , Animais , Canais de Potencial de Receptor Transitório/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Camundongos , Autofagia , Homeostase , Citosol/metabolismoRESUMO
AKT is a serine/threonine kinase that plays an important role in metabolism, cell growth, and cytoskeletal dynamics. AKT is activated by two kinases, PDK1 and mTORC2. Although the regulation of PDK1 is well understood, the mechanism that controls mTORC2 is unknown. Here, by investigating insulin receptor signaling in human cells and biochemical reconstitution, we found that insulin induces the activation of mTORC2 toward AKT by assembling a supercomplex with KRAS4B and RHOA GTPases, termed KARATE (KRAS4B-RHOA-mTORC2 Ensemble). Insulin-induced KARATE assembly is controlled via phosphorylation of GTP-bound KRAS4B at S181 and GDP-bound RHOA at S188 by protein kinase A. By developing a KARATE inhibitor, we demonstrate that KRAS4B-RHOA interaction drives KARATE formation. In adipocytes, KARATE controls insulin-dependent translocation of the glucose transporter GLUT4 to the plasma membrane for glucose uptake. Thus, our work reveals a fundamental mechanism that activates mTORC2 toward AKT in insulin-regulated glucose homeostasis.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/química , Glucose/metabolismo , Insulina/metabolismo , Alvo Mecanístico do Complexo 2 de Rapamicina/química , Proteína rhoA de Ligação ao GTP/química , Células 3T3-L1 , Adipócitos/citologia , Animais , Membrana Celular/metabolismo , Citoesqueleto/metabolismo , Dictyostelium , Transportador de Glucose Tipo 4/metabolismo , Guanosina Difosfato/química , Guanosina Trifosfato/química , Células HEK293 , Humanos , Camundongos , Fosforilação , Transporte Proteico , Proteínas Proto-Oncogênicas c-akt/química , Proteínas Proto-Oncogênicas p21(ras)/química , Proteínas Proto-Oncogênicas p21(ras)/metabolismoRESUMO
CD4+ T cell differentiation requires metabolic reprogramming to fulfil the bioenergetic demands of proliferation and effector function, and enforce specific transcriptional programmes1-3. Mitochondrial membrane dynamics sustains mitochondrial processes4, including respiration and tricarboxylic acid (TCA) cycle metabolism5, but whether mitochondrial membrane remodelling orchestrates CD4+ T cell differentiation remains unclear. Here we show that unlike other CD4+ T cell subsets, T helper 17 (TH17) cells have fused mitochondria with tight cristae. T cell-specific deletion of optic atrophy 1 (OPA1), which regulates inner mitochondrial membrane fusion and cristae morphology6, revealed that TH17 cells require OPA1 for its control of the TCA cycle, rather than respiration. OPA1 deletion amplifies glutamine oxidation, leading to impaired NADH/NAD+ balance and accumulation of TCA cycle metabolites and 2-hydroxyglutarate-a metabolite that influences the epigenetic landscape5,7. Our multi-omics approach revealed that the serine/threonine kinase liver-associated kinase B1 (LKB1) couples mitochondrial function to cytokine expression in TH17 cells by regulating TCA cycle metabolism and transcriptional remodelling. Mitochondrial membrane disruption activates LKB1, which restrains IL-17 expression. LKB1 deletion restores IL-17 expression in TH17 cells with disrupted mitochondrial membranes, rectifying aberrant TCA cycle glutamine flux, balancing NADH/NAD+ and preventing 2-hydroxyglutarate production from the promiscuous activity of the serine biosynthesis enzyme phosphoglycerate dehydrogenase (PHGDH). These findings identify OPA1 as a major determinant of TH17 cell function, and uncover LKB1 as a sensor linking mitochondrial cues to effector programmes in TH17 cells.
Assuntos
Proteínas Quinases Ativadas por AMP , Mitocôndrias , Células Th17 , Glutamina/metabolismo , Interleucina-17/metabolismo , Mitocôndrias/metabolismo , NAD/metabolismo , Fosfoglicerato Desidrogenase/metabolismo , Serina/biossíntese , Serina/metabolismo , Células Th17/citologia , Células Th17/imunologia , Células Th17/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Ciclo do Ácido Cítrico , GTP Fosfo-Hidrolases/deficiência , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismoRESUMO
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
DRP1 plays crucial roles in mitochondrial and peroxisome fission. However, the mechanisms underlying the functional regulation of DRP1 in adipose tissue during obesity remain unclear. To elucidate the metabolic and pathological significance of diminished DRP1 in obese adipose tissue, we utilized adipose tissue-specific DRP1 KO mice challenged with an HFD. We observed significant metabolic dysregulations in the KO mice. Mechanistically, DRP1 exerts multifaceted functions in mitochondrial dynamics and ER-lipid droplet cross-talk in normal mice. Loss-of-function of DRP1 resulted in abnormally giant mitochondrial shapes, distorted mitochondrial membrane structure, and disrupted cristae architecture. Meanwhile, DRP1 deficiency induced the retention of nascent lipid droplets in ER, leading to perturbed overall lipid dynamics in the KO mice. Collectively, dysregulation of the dynamics of mitochondria, ER, and lipid droplets contributes to whole-body metabolic disorders, as evidenced by perturbations in energy metabolites. Our findings demonstrate that DRP1 plays a pivotal role in energy homeostasis in adipose tissue during obesity.
RESUMO
RING-between RING (RBR)-type ubiquitin (Ub) ligases (E3s) such as Parkin receive Ub from Ub-conjugating enzymes (E2s) in response to ligase activation. However, the specific E2s that transfer Ub to each RBR-type ligase are largely unknown because of insufficient methods for monitoring their interaction. To address this problem, we have developed a method that detects intracellular interactions between E2s and activated Parkin. Fluorescent homotetramer Azami-Green fused with E2 and oligomeric Ash (Assembly helper) fused with Parkin form a liquid-liquid phase separation (LLPS) in cells only when E2 and Parkin interact. Using this method, we identified multiple E2s interacting with activated Parkin on damaged mitochondria during mitophagy. Combined with in vitro ubiquitination assays and bioinformatics, these findings revealed an underlying consensus sequence for E2 interactions with activated Parkin. Application of this method to other RBR-type E3s including HOIP, HHARI, and TRIAD1 revealed that HOIP forms an LLPS with its substrate NEMO in response to a proinflammatory cytokine and that HHARI and TRIAD1 form a cytosolic LLPS independent of Ub-like protein NEDD8. Since an E2-E3 interaction is a prerequisite for RBR-type E3 activation and subsequent substrate ubiquitination, the method we have established here can be an in-cell tool to elucidate the potentially novel mechanisms involved in RBR-type E3s.
Assuntos
Enzimas de Conjugação de Ubiquitina , Ubiquitina-Proteína Ligases , Ubiquitina/metabolismo , Enzimas de Conjugação de Ubiquitina/química , Enzimas de Conjugação de Ubiquitina/isolamento & purificação , Enzimas de Conjugação de Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/isolamento & purificação , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitinação , Ligação Proteica , Mitofagia , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Quinase I-kappa B/metabolismoRESUMO
The connectivity of mitochondria is regulated by a balance between fusion and division. Many human diseases are associated with excessive mitochondrial connectivity due to impaired Drp1, a dynamin-related GTPase that mediates division. Here, we report a mitochondrial stress response, named mitochondrial safeguard, that adjusts the balance of fusion and division in response to increased mitochondrial connectivity. In cells lacking Drp1, mitochondria undergo hyperfusion. However, hyperfusion does not completely connect mitochondria because Opa1 and mitofusin 1, two other dynamin-related GTPases that mediate fusion, become proteolytically inactivated. Pharmacological and genetic experiments show that the activity of Oma1, a metalloprotease that cleaves Opa1, is regulated by short pulses of the membrane depolarization without affecting the overall membrane potential in Drp1-knockout cells. Re-activation of Opa1 and Mitofusin 1 in Drp1-knockout cells further connects mitochondria beyond hyperfusion, termed extreme fusion, leading to bioenergetic deficits. These findings reveal an unforeseen safeguard mechanism that prevents extreme fusion of mitochondria, thereby maintaining mitochondrial function when the balance is shifted to excessive connectivity.
Assuntos
Metaloendopeptidases/genética , Metaloendopeptidases/metabolismo , Mitocôndrias/metabolismo , Estresse Fisiológico/fisiologia , Animais , Dinaminas/genética , Dinaminas/metabolismo , Metabolismo Energético , GTP Fosfo-Hidrolases/metabolismo , Técnicas de Inativação de Genes , Células HEK293 , Humanos , Metaloproteases/metabolismo , Camundongos , Mitocôndrias/genética , Dinâmica Mitocondrial/fisiologia , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas Mitocondriais/metabolismo , Estresse Fisiológico/genética , TranscriptomaRESUMO
Mitochondrial dysfunction causes severe congenital cardiac abnormalities and prenatal/neonatal lethality. The lack of sufficient knowledge regarding how mitochondrial abnormalities affect cardiogenesis poses a major barrier for the development of clinical applications that target mitochondrial deficiency-induced inborn cardiomyopathies. Mitochondrial morphology, which is regulated by fission and fusion, plays a key role in determining mitochondrial activity. Dnm1l encodes a dynamin-related GTPase, Drp1, which is required for mitochondrial fission. To investigate the role of Drp1 in cardiogenesis during the embryonic metabolic shift period, we specifically inactivated Dnm1l in second heart field-derived structures. Mutant cardiomyocytes in the right ventricle (RV) displayed severe defects in mitochondrial morphology, ultrastructure and activity. These defects caused increased cell death, decreased cell survival, disorganized cardiomyocytes and embryonic lethality. By characterizing this model, we reveal an AMPK-SIRT7-GABPB axis that relays the reduced cellular energy level to decrease transcription of ribosomal protein genes in cardiomyocytes. We therefore provide the first genetic evidence in mouse that Drp1 is essential for RV development. Our research provides further mechanistic insight into how mitochondrial dysfunction causes pathological molecular and cellular alterations during cardiogenesis.
Assuntos
Dinaminas , Proteínas Ribossômicas , Animais , Dinaminas/genética , Dinaminas/metabolismo , Coração/embriologia , Camundongos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Miócitos Cardíacos/metabolismo , Proteínas Ribossômicas/genética , Proteínas Ribossômicas/metabolismoRESUMO
BACKGROUND AND AIMS: Increased megamitochondria formation and impaired mitophagy in hepatocytes have been linked to the pathogenesis of alcohol-associated liver disease (ALD). This study aims to determine the mechanisms by which alcohol consumption increases megamitochondria formation in the pathogenesis of ALD. APPROACH AND RESULTS: Human alcoholic hepatitis (AH) liver samples were used for electron microscopy, histology, and biochemical analysis. Liver-specific dynamin-related protein 1 (DRP1; gene name DNM1L, an essential gene regulating mitochondria fission ) knockout (L-DRP1 KO) mice and wild-type mice were subjected to chronic plus binge alcohol feeding. Both human AH and alcohol-fed mice had decreased hepatic DRP1 with increased accumulation of hepatic megamitochondria. Mechanistic studies revealed that alcohol feeding decreased DRP1 by impairing transcription factor EB-mediated induction of DNM1L . L-DRP1 KO mice had increased megamitochondria and decreased mitophagy with increased liver injury and inflammation, which were further exacerbated by alcohol feeding. Seahorse flux and unbiased metabolomics analysis showed alcohol intake increased mitochondria oxygen consumption and hepatic nicotinamide adenine dinucleotide (NAD + ), acylcarnitine, and ketone levels, which were attenuated in L-DRP1 KO mice, suggesting that loss of hepatic DRP1 leads to maladaptation to alcohol-induced metabolic stress. RNA-sequencing and real-time quantitative PCR analysis revealed increased gene expression of the cGAS-stimulator of interferon genes (STING)-interferon pathway in L-DRP1 KO mice regardless of alcohol feeding. Alcohol-fed L-DRP1 KO mice had increased cytosolic mtDNA and mitochondrial dysfunction leading to increased activation of cGAS-STING-interferon signaling pathways and liver injury. CONCLUSION: Alcohol consumption decreases hepatic DRP1 resulting in increased megamitochondria and mitochondrial maladaptation that promotes AH by mitochondria-mediated inflammation and cell injury.
Assuntos
Hepatite Alcoólica , Hepatopatias Alcoólicas , Camundongos , Humanos , Animais , Dilatação Mitocondrial , Hepatopatias Alcoólicas/metabolismo , Mitocôndrias/metabolismo , Etanol/toxicidade , Nucleotidiltransferases , Inflamação , Interferons , Dinâmica MitocondrialRESUMO
Mitochondria divide to control their size, distribution, turnover, and function. Dynamin-related protein 1 (Drp1) is a critical mechanochemical GTPase that drives constriction during mitochondrial division. It is generally believed that mitochondrial division is regulated during recruitment of Drp1 to mitochondria and its oligomerization into a division apparatus. Here, we report an unforeseen mechanism that regulates mitochondrial division by coincident interactions of Drp1 with the head group and acyl chains of phospholipids. Drp1 recognizes the head group of phosphatidic acid (PA) and two saturated acyl chains of another phospholipid by penetrating into the hydrophobic core of the membrane. The dual phospholipid interactions restrain Drp1 via inhibition of oligomerization-stimulated GTP hydrolysis that promotes membrane constriction. Moreover, a PA-producing phospholipase, MitoPLD, binds Drp1, creating a PA-rich microenvironment in the vicinity of a division apparatus. Thus, PA controls the activation of Drp1 after the formation of the division apparatus.
Assuntos
Dinaminas/genética , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/genética , Ácidos Fosfatídicos/metabolismo , Fosfolipase D/genética , Testículo/metabolismo , Animais , Sítios de Ligação , Dinaminas/metabolismo , Fibroblastos/metabolismo , Fibroblastos/ultraestrutura , Regulação da Expressão Gênica , Guanosina Trifosfato/metabolismo , Masculino , Camundongos , Mitocôndrias/ultraestrutura , Membranas Mitocondriais/metabolismo , Membranas Mitocondriais/ultraestrutura , Proteínas Mitocondriais/metabolismo , Fosfolipase D/metabolismo , Ligação Proteica , Transdução de Sinais , Estearoil-CoA Dessaturase/genética , Estearoil-CoA Dessaturase/metabolismo , Testículo/ultraestruturaRESUMO
Mitochondrial division is essential for mitosis and metazoan development, but a mechanistic role in cancer biology remains unknown. Here, we examine the direct effects of oncogenic RAS(G12V)-mediated cellular transformation on the mitochondrial dynamics machinery and observe a positive selection for dynamin-related protein 1 (DRP1), a protein required for mitochondrial network division. Loss of DRP1 prevents RAS(G12V)-induced mitochondrial dysfunction and renders cells resistant to transformation. Conversely, in human tumor cell lines with activating MAPK mutations, inhibition of these signals leads to robust mitochondrial network reprogramming initiated by DRP1 loss resulting in mitochondrial hyper-fusion and increased mitochondrial metabolism. These phenotypes are mechanistically linked by ERK1/2 phosphorylation of DRP1 serine 616; DRP1(S616) phosphorylation is sufficient to phenocopy transformation-induced mitochondrial dysfunction, and DRP1(S616) phosphorylation status dichotomizes BRAF(WT) from BRAF(V600E)-positive lesions. These findings implicate mitochondrial division and DRP1 as crucial regulators of transformation with leverage in chemotherapeutic success.
Assuntos
Transformação Celular Neoplásica/genética , Dinaminas/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas ras/metabolismo , Animais , Linhagem Celular Tumoral , Dinaminas/genética , GTP Fosfo-Hidrolases/genética , Células HT29 , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Proteínas Associadas aos Microtúbulos/genética , Proteínas Mitocondriais/genética , Fosforilação , Inibidores de Proteínas Quinases/farmacologia , Serina/metabolismo , Proteínas ras/genéticaRESUMO
During apoptosis, pro-apoptotic BAX and BAK are activated, causing mitochondrial outer membrane permeabilisation (MOMP), caspase activation and cell death. However, even in the absence of caspase activity, cells usually die following MOMP Such caspase-independent cell death is accompanied by inflammation that requires mitochondrial DNA (mtDNA) activation of cGAS-STING signalling. Because the mitochondrial inner membrane is thought to remain intact during apoptosis, we sought to address how matrix mtDNA could activate the cytosolic cGAS-STING signalling pathway. Using super-resolution imaging, we show that mtDNA is efficiently released from mitochondria following MOMP In a temporal manner, we find that following MOMP, BAX/BAK-mediated mitochondrial outer membrane pores gradually widen. This allows extrusion of the mitochondrial inner membrane into the cytosol whereupon it permeablises allowing mtDNA release. Our data demonstrate that mitochondrial inner membrane permeabilisation (MIMP) can occur during cell death following BAX/BAK-dependent MOMP Importantly, by enabling the cytosolic release of mtDNA, inner membrane permeabilisation underpins the immunogenic effects of caspase-independent cell death.
Assuntos
Apoptose , DNA Mitocondrial/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Animais , Linhagem Celular Tumoral , DNA Mitocondrial/genética , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Mitocôndrias/genética , Nucleotidiltransferases/genética , Nucleotidiltransferases/metabolismo , PermeabilidadeRESUMO
Many human diseases, including cancer and neurological abnormalities, are linked to deficiencies of phosphatase and tensin homolog deleted on chromosome ten (PTEN), a dual phosphatase that dephosphorylates both lipids and proteins. PTEN functions in multiple intracellular locations, including the plasma membrane and nucleus. Therefore, a critical challenge to understand the pathogenesis of PTEN-associated diseases is to determine the specific role of PTEN at different locations. Toward this goal, the current study generated a mouse line in which lysine 13, which is critical for the nuclear localization of PTEN, is changed to arginine in the lipid-binding domain using the CRISPR-Ca9 gene-editing system. We found that PTENK13R mice show a strong decrease in the localization of PTEN in the nucleus without affecting the protein stability, phosphatase activity, and phosphorylation in the C-terminal tail region. PTENK13R mice are viable but produce smaller neurons and develop microcephaly. These data demonstrate that PTENK13R mice provide a useful animal model to study the role of PTEN in the nucleus in vivo.
Assuntos
Núcleo Celular , PTEN Fosfo-Hidrolase , Animais , Núcleo Celular/metabolismo , Modelos Animais de Doenças , Camundongos , Mutação , Neurônios/metabolismo , PTEN Fosfo-Hidrolase/genética , PTEN Fosfo-Hidrolase/metabolismo , FosforilaçãoRESUMO
Mitochondrial dynamics is a conserved process by which mitochondria undergo repeated cycles of fusion and fission, leading to exchange of mitochondrial genetic content, ions, metabolites, and proteins. Here, we examine the role of the mitochondrial fusion protein optic atrophy 1 (OPA1) in differentiated skeletal muscle by reducing OPA1 gene expression in an inducible manner. OPA1 deficiency in young mice results in non-lethal progressive mitochondrial dysfunction and loss of muscle mass. Mutant mice are resistant to age- and diet-induced weight gain and insulin resistance, by mechanisms that involve activation of ER stress and secretion of fibroblast growth factor 21 (FGF21) from skeletal muscle, resulting in increased metabolic rates and improved whole-body insulin sensitivity. OPA1-elicited mitochondrial dysfunction activates an integrated stress response that locally induces muscle atrophy, but via secretion of FGF21 acts distally to modulate whole-body metabolism.
Assuntos
Fatores de Crescimento de Fibroblastos/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Resistência à Insulina , Músculos/metabolismo , Atrofia Muscular/patologia , Obesidade/prevenção & controle , Animais , GTP Fosfo-Hidrolases/deficiência , Técnicas de Silenciamento de Genes , CamundongosRESUMO
Defects in PTEN, a critical tumor suppressor, are associated with tumorigenesis and aberrant organ sizes. It has been shown that heterozygous PTEN loss increases brains and neuron size, while the specific loss of nuclear PTEN has the opposite effect. Here, we investigate the impact of a combination of heterozygous PTEN loss and nuclear PTEN loss on the size of various organs, including the brain, liver, thymus, spleen, and inguinal lymph node. We found that the effect of the combination varies among organs. Notably, the combination of heterozygous PTEN loss and nuclear PTEN loss restored the normal size of brains and neurons. In contrast, the liver's size was unaffected by either single PTEN defects or their combination. Strikingly, the size of the inguinal lymph node was greatly increased due to lymphoma by the combination of the two PTEN defects. These data suggest that nuclear PTEN and non-nuclear PTEN function in an antagonistic manner in the brain while acting synergistically in the inguinal lymph node.
Assuntos
Encéfalo/patologia , Núcleo Celular/metabolismo , Linfonodos/patologia , PTEN Fosfo-Hidrolase/genética , PTEN Fosfo-Hidrolase/metabolismo , Animais , Encéfalo/anatomia & histologia , Núcleo Celular/genética , Heterozigoto , Camundongos Knockout , Camundongos Transgênicos , Neurônios/metabolismo , Neurônios/patologiaRESUMO
PTEN and p53 are highly mutated in many cancers. These two tumor suppressors have critical functions in the nucleus, such as DNA repair, cell cycle progression, and genome maintenance. However, the in vivo functional relationship of nuclear PTEN and p53 is unknown. Here, we analyzed the liver of mice in which nuclear PTEN and p53 are individually or simultaneously depleted. We found that nuclear PTEN loss greatly upregulates p53 expression upon oxidative stress, while the loss of p53 potentiates stress-induced accumulation of PTEN in the nucleus. Next, we examined oxidative stress-induced DNA damage in hepatocytes, and found that nuclear PTEN loss aggravated the damage while p53 loss did not. Notably, mice lacking nuclear PTEN had increased hepatocellular carcinoma under oxidative stress, while mice lacking p53 in hepatocytes had accelerated hepatocellular carcinoma and intrahepatic cholangiocarcinoma. The formation of cholangiocarcinoma appears to involve the transformation of hepatocytes into cholangiocarcinoma. Simultaneous loss of nuclear PTEN and p53 exacerbated both types of liver cancers. These data suggest that nuclear PTEN and p53 suppress liver cancers through distinct mechanisms.
Assuntos
Núcleo Celular/metabolismo , Neoplasias Hepáticas/patologia , Estresse Oxidativo , PTEN Fosfo-Hidrolase/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Neoplasias dos Ductos Biliares/patologia , Carcinogênese/metabolismo , Carcinogênese/patologia , Colangiocarcinoma/patologia , Dano ao DNA , Hepatócitos/metabolismo , Cirrose Hepática/patologia , Masculino , Camundongos Knockout , PTEN Fosfo-Hidrolase/deficiência , Proteína Supressora de Tumor p53/deficiência , Regulação para CimaRESUMO
Dynamin-Related-Protein 1 (DRP1) critically regulates mitochondrial and peroxisomal fission in multicellular organisms. However, the impact of DRP1 on other organelles, especially its direct influence on ER functions remains largely unclear. Here, we report that DRP1 translocates to endoplasmic reticulum (ER) in response to ß-adrenergic stimulation. To further investigate the function of DRP1 on ER-lipid droplet (LD) dynamics and the metabolic subsequences, we generated an adipose tissue-specific DRP1 knockout model (Adipo-Drp1flx/flx ). We found that the LDs in adipose tissues of Adipo-Drp1flx/flx mice exhibited more unilocular morphology with larger sizes, and formed less multilocular structures upon cold exposure. Mechanistically, we discovered that abnormal LD morphology occurs because newly generated micro-LDs fail to dissociate from the ER due to DRP1 ablation. Conversely, the ER retention of LDs can be rescued by the overexpressed DRP1 in the adipocytes. The alteration of LD dynamics, combined with abnormal mitochondrial and autophagy functions in adipose tissue, ultimately lead to abnormalities in lipid metabolism in Adipo-Drp1flx/flx mice.
Assuntos
Tecido Adiposo/metabolismo , Dinaminas/metabolismo , Retículo Endoplasmático/metabolismo , Gotículas Lipídicas/metabolismo , Células 3T3 , Adipócitos/metabolismo , Animais , Autofagia/fisiologia , Linhagem Celular , Células HEK293 , Humanos , Metabolismo dos Lipídeos/fisiologia , Masculino , Camundongos , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/fisiologia , Proteínas Mitocondriais/metabolismoRESUMO
Mitochondrial division apparatuses are generally thought to form by oligomerization of Drp1 at pre-determined sites on mitochondria. A recent study by Ji et al. now shows that the Drp1 oligomers on mitochondria move, merge, and mature into a functional division apparatus.