RESUMO
Mitochondria are central hubs of cellular metabolism and are tightly connected to signaling pathways. The dynamic plasticity of mitochondria to fuse, divide, and contact other organelles to flux metabolites is central to their function. To ensure bona fide functionality and signaling interconnectivity, diverse molecular mechanisms evolved. An ancient and long-overlooked mechanism is the generation of mitochondrial-derived vesicles (MDVs) that shuttle selected mitochondrial cargoes to target organelles. Just recently, we gained significant insight into the mechanisms and functions of MDV transport, ranging from their role in mitochondrial quality control to immune signaling, thus demonstrating unexpected and diverse physiological aspects of MDV transport. This review highlights the origin of MDVs, their biogenesis, and their cargo selection, with a specific focus on the contribution of MDV transport to signaling across cell and organ barriers. Additionally, the implications of MDVs in peroxisome biogenesis, neurodegeneration, metabolism, aging, and cancer are discussed.
Assuntos
Mitocôndrias , Peroxissomos , Mitocôndrias/metabolismo , Peroxissomos/metabolismo , Transporte BiológicoRESUMO
Mitochondrial and peroxisomal anchored protein ligase (MAPL) is a dual ubiquitin and small ubiquitin-like modifier (SUMO) ligase with roles in mitochondrial quality control, cell death and inflammation in cultured cells. Here, we show that MAPL function in the organismal context converges on metabolic control, as knockout mice are viable, insulin-sensitive, and protected from diet-induced obesity. MAPL loss leads to liver-specific activation of the integrated stress response, inducing secretion of stress hormone FGF21. MAPL knockout mice develop fully penetrant spontaneous hepatocellular carcinoma. Mechanistically, the peroxisomal bile acid transporter ABCD3 is a primary MAPL interacting partner and SUMOylated in a MAPL-dependent manner. MAPL knockout leads to increased bile acid production coupled with defective regulatory feedback in liver in vivo and in isolated primary hepatocytes, suggesting cell-autonomous function. Together, our findings establish MAPL function as a regulator of bile acid synthesis whose loss leads to the disruption of bile acid feedback mechanisms. The consequences of MAPL loss in liver, along with evidence of tumor suppression through regulation of cell survival pathways, ultimately lead to hepatocellular carcinogenesis.
Assuntos
Bile , Proteínas Mitocondriais , Ubiquitina-Proteína Ligases , Animais , Camundongos , Bile/metabolismo , Ácidos e Sais Biliares , Fígado/metabolismo , Camundongos Knockout , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinasRESUMO
Dysfunctional mitochondria are removed via multiple pathways, such as mitophagy, a selective autophagy process. Here, we identify an intracellular hybrid mitochondria-lysosome organelle (termed the mitochondria-lysosome-related organelle [MLRO]), which regulates mitochondrial homeostasis independent of canonical mitophagy during hepatocyte dedifferentiation. The MLRO is an electron-dense organelle that has either a single or double membrane with both mitochondria and lysosome markers. Mechanistically, the MLRO is likely formed from the fusion of mitochondria-derived vesicles (MDVs) with lysosomes through a PARKIN-, ATG5-, and DRP1-independent process, which is negatively regulated by transcription factor EB (TFEB) and associated with mitochondrial protein degradation and hepatocyte dedifferentiation. The MLRO, which is galectin-3 positive, is reminiscent of damaged lysosome and could be cleared by overexpression of TFEB, resulting in attenuation of hepatocyte dedifferentiation. Together, results from this study suggest that the MLRO may act as an alternative mechanism for mitochondrial quality control independent of canonical autophagy/mitophagy involved in cell dedifferentiation.
Assuntos
Mitocôndrias , Organelas , Mitocôndrias/metabolismo , Organelas/metabolismo , Lisossomos/metabolismo , Autofagia/fisiologia , Mitofagia/fisiologiaRESUMO
Peroxisomes play a central role in tuning metabolic and signaling programs in a tissue- and cell-type-specific manner. However, the mechanisms by which the status of peroxisomes is communicated and integrated into cellular signaling pathways are not yet understood. Herein, we report the cellular responses to peroxisomal proteotoxic stress upon silencing the peroxisomal protease/chaperone LONP2. Depletion of LONP2 triggered the accumulation of its substrate TYSND1 protease, while the overall expression of peroxisomal proteins, as well as TYSND1-dependent ACOX1 processing appeared normal, reflecting early stages of peroxisomal proteotoxic stress. Consequently, the alteration of peroxisome size and numbers, and luminal protein import failure was coupled with induction of cell-specific cellular stress responses. Specific to COS-7 cells was a strong activation of the integrated stress response (ISR) and upregulation of ribosomal biogenesis gene expression levels. Common changes between COS-7 and U2OS cell lines included repression of the retinoic acid signaling pathway and upregulation of sphingolipids. Cholesterol accumulated in the endomembrane compartments in both cell lines, consistent with evidence that peroxisomes are required for cholesterol flux out of late endosomes. These unexpected consequences of peroxisomal stress provide an important insight into our understanding of the tissue-specific responses seen in peroxisomal disorders.
Assuntos
Endossomos , Transdução de Sinais , Ribossomos , Peptídeo Hidrolases , Regulação para CimaRESUMO
Repeated or prolonged, but not short-term, general anesthesia during the early postnatal period causes long-lasting impairments in memory formation in various species. The mechanisms underlying long-lasting impairment in cognitive function are poorly understood. Here, we show that repeated general anesthesia in postnatal mice induces preferential apoptosis and subsequent loss of parvalbumin-positive inhibitory interneurons in the hippocampus. Each parvalbumin interneuron controls the activity of multiple pyramidal excitatory neurons, thereby regulating neuronal circuits and memory consolidation. Preventing the loss of parvalbumin neurons by deleting a proapoptotic protein, mitochondrial anchored protein ligase (MAPL), selectively in parvalbumin neurons rescued anesthesia-induced deficits in pyramidal cell inhibition and hippocampus-dependent long-term memory. Conversely, partial depletion of parvalbumin neurons in neonates was sufficient to engender long-lasting memory impairment. Thus, loss of parvalbumin interneurons in postnatal mice following repeated general anesthesia critically contributes to memory deficits in adulthood.
Assuntos
Anestesia , Parvalbuminas , Camundongos , Animais , Parvalbuminas/genética , Parvalbuminas/metabolismo , Interneurônios/metabolismo , Neurônios/metabolismo , Células Piramidais/metabolismo , Hipocampo/metabolismo , Transtornos da Memória/induzido quimicamente , Transtornos da Memória/genética , Transtornos da Memória/metabolismoRESUMO
The nervous system spread of alpha-synuclein fibrils is thought to cause Parkinson's disease (PD) and other synucleinopathies; however, the mechanisms underlying internalization and cellular spread are enigmatic. Here, we use confocal and superresolution microscopy, subcellular fractionation, and electron microscopy (EM) of immunogold-labeled α-synuclein preformed fibrils (PFFs) to demonstrate that this form of the protein undergoes rapid internalization and is targeted directly to lysosomes in as little as 2 min. Uptake of PFFs is disrupted by macropinocytic inhibitors and circumvents classical endosomal pathways. Immunogold-labeled PFFs are seen at the highly curved inward edge of membrane ruffles, in newly formed macropinosomes, in multivesicular bodies and in lysosomes. While most fibrils remain in lysosomes, a portion is transferred to neighboring naive cells along with markers of exosomes. These data indicate that PFFs use a unique internalization mechanism as a component of cell-to-cell propagation.
Assuntos
Doença de Parkinson , Sinucleinopatias , Endossomos/metabolismo , Humanos , Lisossomos/metabolismo , Doença de Parkinson/metabolismo , alfa-Sinucleína/metabolismoRESUMO
In our 20th anniversary year, we reflect on how fields have changed since our first issue and here look to the future. In this collection of Voices, our writers speculate on the future: in terms of philosophy, cell states, cell processes, and then how to model cell systems.
Assuntos
Biologia Celular , Biologia do Desenvolvimento , Publicações Periódicas como Assunto/estatística & dados numéricos , Humanos , Fatores de TempoRESUMO
Mitochondrial-derived vesicles (MDVs) are implicated in diverse physiological processes-for example, mitochondrial quality control-and are linked to various neurodegenerative diseases. However, their specific cargo composition and complex molecular biogenesis are still unknown. Here we report the proteome and lipidome of steady-state TOMM20+ MDVs. We identified 107 high-confidence MDV cargoes, which include all ß-barrel proteins and the TOM import complex. MDV cargoes are delivered as fully assembled complexes to lysosomes, thus representing a selective mitochondrial quality control mechanism for multi-subunit complexes, including the TOM machinery. Moreover, we define key biogenesis steps of phosphatidic acid-enriched MDVs starting with the MIRO1/2-dependent formation of thin membrane protrusions pulled along microtubule filaments, followed by MID49/MID51/MFF-dependent recruitment of the dynamin family GTPase DRP1 and finally DRP1-dependent scission. In summary, we define the function of MDVs in mitochondrial quality control and present a mechanistic model for global GTPase-driven MDV biogenesis.
Assuntos
Vesículas Citoplasmáticas/fisiologia , Dinaminas/metabolismo , Dinâmica Mitocondrial/fisiologia , Membranas Mitocondriais/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo , Animais , Células COS , Linhagem Celular Tumoral , Chlorocebus aethiops , Células HEK293 , Células HeLa , Humanos , Lipidômica , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Proteínas do Complexo de Importação de Proteína Precursora Mitocondrial/metabolismo , Doenças Neurodegenerativas/patologia , Fatores de Alongamento de Peptídeos/metabolismo , Ácidos Fosfatídicos/metabolismo , Proteoma/genética , Interferência de RNA , RNA Interferente Pequeno/genéticaRESUMO
Schuler et al. (2021) demonstrate that mitochondrial-derived compartments protect cells from amino acid toxicity by activation of amino acid catabolism through the Ehrlich pathway, thus highlighting the incredible plasticity of mitochondria in rewiring cellular metabolism.
Assuntos
Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Álcoois , Mitocôndrias , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genéticaRESUMO
Mitochondria are dynamic organelles that produce energy and molecular precursors that are essential for myelin synthesis. Unlike in neurons, mitochondria in oligodendrocytes increase intracellular movement in response to glutamatergic activation and are more susceptible to oxidative stress than in astrocytes or microglia. The signaling pathways that regulate these cell type-specific mitochondrial responses in oligodendrocytes are not understood. Here, we visualized mitochondria migrating through thin cytoplasmic channels crossing myelin basic protein-positive compacted membranes and localized within paranodal loop cytoplasm. We hypothesized that local extracellular enrichment of netrin-1 might regulate the recruitment and function of paranodal proteins and organelles, including mitochondria. We identified rapid recruitment of mitochondria and paranodal proteins, including neurofascin 155 (NF155) and the netrin receptor deleted in colorectal carcinoma (DCC), to sites of contact between oligodendrocytes and netrin-1-coated microbeads in vitro. We provide evidence that Src-family kinase activation and Rho-associated protein kinase (ROCK) inhibition downstream of netrin-1 induces mitochondrial elongation, hyperpolarization of the mitochondrial inner membrane, and increases glycolysis. Our findings identify a signaling mechanism in oligodendrocytes that is sufficient to locally recruit paranodal proteins and regulate the subcellular localization, morphology, and function of mitochondria.
Assuntos
Dinâmica Mitocondrial , Receptor DCC , Metabolismo Energético , Fatores de Crescimento Neural/genética , Fatores de Crescimento Neural/metabolismo , Netrina-1 , Oligodendroglia/metabolismo , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Quinases Associadas a rho/metabolismoRESUMO
Mitochondrial plasticity is a key regulator of cell fate decisions. Mitochondrial division involves Dynamin-related protein-1 (Drp1) oligomerization, which constricts membranes at endoplasmic reticulum (ER) contact sites. The mechanisms driving the final steps of mitochondrial division are still unclear. Here, we found that microdomains of phosphatidylinositol 4-phosphate [PI(4)P] on trans-Golgi network (TGN) vesicles were recruited to mitochondria-ER contact sites and could drive mitochondrial division downstream of Drp1. The loss of the small guanosine triphosphatase ADP-ribosylation factor 1 (Arf1) or its effector, phosphatidylinositol 4-kinase IIIß [PI(4)KIIIß], in different mammalian cell lines prevented PI(4)P generation and led to a hyperfused and branched mitochondrial network marked with extended mitochondrial constriction sites. Thus, recruitment of TGN-PI(4)P-containing vesicles at mitochondria-ER contact sites may trigger final events leading to mitochondrial scission.
Assuntos
Mitocôndrias/metabolismo , Dinâmica Mitocondrial , Fosfatos de Fosfatidilinositol/metabolismo , Rede trans-Golgi/metabolismo , 1-Fosfatidilinositol 4-Quinase/genética , 1-Fosfatidilinositol 4-Quinase/metabolismo , Fator 1 de Ribosilação do ADP/genética , Fator 1 de Ribosilação do ADP/metabolismo , Animais , Células COS , Linhagem Celular , Chlorocebus aethiops , Dinaminas/metabolismo , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Células HeLa , Humanos , Microdomínios da Membrana , Mitocôndrias/ultraestrutura , Membranas Mitocondriais/metabolismo , Interferência de RNARESUMO
Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the selective loss of motor neurons leading to paralysis. Mutations in the gene encoding superoxide dismutase 1 (SOD1) are the second most common cause of familial ALS, and considerable evidence suggests that these mutations result in an increase in toxicity due to protein misfolding. We previously demonstrated in the SOD1G93A rat model that misfolded SOD1 exists as distinct conformers and forms deposits on mitochondrial subpopulations. Here, using SOD1G93A rats and conformation-restricted antibodies specific for misfolded SOD1 (B8H10 and AMF7-63), we identified the interactomes of the mitochondrial pools of misfolded SOD1. This strategy identified binding proteins that uniquely interacted with either AMF7-63 or B8H10-reactive SOD1 conformers as well as a high proportion of interactors common to both conformers. Of this latter set, we identified the E3 ubiquitin ligase TNF receptor-associated factor 6 (TRAF6) as a SOD1 interactor, and we determined that exposure of the SOD1 functional loops facilitates this interaction. Of note, this conformational change was not universally fulfilled by all SOD1 variants and differentiated TRAF6 interacting from TRAF6 noninteracting SOD1 variants. Functionally, TRAF6 stimulated polyubiquitination and aggregation of the interacting SOD1 variants. TRAF6 E3 ubiquitin ligase activity was required for the former but was dispensable for the latter, indicating that TRAF6-mediated polyubiquitination and aggregation of the SOD1 variants are independent events. We propose that the interaction between misfolded SOD1 and TRAF6 may be relevant to the etiology of ALS.
Assuntos
Esclerose Lateral Amiotrófica/patologia , Superóxido Dismutase-1/metabolismo , Fator 6 Associado a Receptor de TNF/metabolismo , Esclerose Lateral Amiotrófica/metabolismo , Animais , Anticorpos/imunologia , Linhagem Celular , Modelos Animais de Doenças , Mitocôndrias/metabolismo , Mutagênese Sítio-Dirigida , NF-kappa B/metabolismo , Agregados Proteicos , Dobramento de Proteína , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Ratos , Ratos Transgênicos , Superóxido Dismutase-1/química , Superóxido Dismutase-1/genética , Superóxido Dismutase-1/imunologia , Fator 6 Associado a Receptor de TNF/antagonistas & inibidores , Fator 6 Associado a Receptor de TNF/genética , UbiquitinaçãoRESUMO
Plasma membrane damage and cell death during processes such as necroptosis and apoptosis result from cues originating intracellularly. However, death caused by pore-forming agents, like bacterial toxins or complement, is due to direct external injury to the plasma membrane. To prevent death, the plasma membrane has an intrinsic repair ability. Here, we found that repair triggered by pore-forming agents involved TMEM16F, a calcium-activated lipid scramblase also mutated in Scott's syndrome. Upon pore formation and the subsequent influx of intracellular calcium, TMEM16F induced rapid "lipid scrambling" in the plasma membrane. This response was accompanied by membrane blebbing, extracellular vesicle release, preserved membrane integrity, and increased cell viability. TMEM16F-deficient mice exhibited compromised control of infection by Listeria monocytogenes associated with a greater sensitivity of neutrophils to the pore-forming Listeria toxin listeriolysin O (LLO). Thus, the lipid scramblase TMEM16F is critical for plasma membrane repair after injury by pore-forming agents.
Assuntos
Anoctaminas/metabolismo , Toxinas Bacterianas/toxicidade , Membrana Celular/metabolismo , Vesículas Extracelulares/metabolismo , Proteínas de Choque Térmico/toxicidade , Proteínas Hemolisinas/toxicidade , Fosfatidilserinas/metabolismo , Proteínas de Transferência de Fosfolipídeos/metabolismo , Timócitos/metabolismo , Animais , Anoctaminas/genética , Cálcio/metabolismo , Morte Celular/efeitos dos fármacos , Morte Celular/genética , Membrana Celular/efeitos dos fármacos , Vesículas Extracelulares/efeitos dos fármacos , Listeria monocytogenes/metabolismo , Listeria monocytogenes/patogenicidade , Fígado/citologia , Fígado/metabolismo , Fígado/microbiologia , Fígado/patologia , Lipídeos de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microscopia Eletrônica de Varredura , Neutrófilos/citologia , Neutrófilos/efeitos dos fármacos , Neutrófilos/microbiologia , Neutrófilos/patologia , Proteínas de Transferência de Fosfolipídeos/genética , Baço/citologia , Baço/metabolismo , Baço/microbiologia , Baço/patologia , Timócitos/efeitos dos fármacos , Timócitos/ultraestruturaRESUMO
Antibodies are a key resource in biomedical research yet there are no community-accepted standards to rigorously characterize their quality. Here we develop a procedure to validate pre-existing antibodies. Human cell lines with high expression of a target, determined through a proteomics database, are modified with CRISPR/Cas9 to knockout (KO) the corresponding gene. Commercial antibodies against the target are purchased and tested by immunoblot comparing parental and KO. Validated antibodies are used to definitively identify the most highly expressing cell lines, new KOs are generated if needed, and the lines are screened by immunoprecipitation and immunofluorescence. Selected antibodies are used for more intensive procedures such as immunohistochemistry. The pipeline is easy to implement and scalable. Application to the major ALS disease gene C9ORF72 identified high-quality antibodies revealing C9ORF72 localization to phagosomes/lysosomes. Antibodies that do not recognize C9ORF72 have been used in highly cited papers, raising concern over previously reported C9ORF72 properties.
Assuntos
Esclerose Lateral Amiotrófica/diagnóstico , Anticorpos Monoclonais/química , Proteína C9orf72/genética , Demência Frontotemporal/diagnóstico , Imuno-Histoquímica/normas , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/imunologia , Esclerose Lateral Amiotrófica/metabolismo , Animais , Anticorpos Monoclonais/classificação , Anticorpos Monoclonais/imunologia , Biomarcadores/metabolismo , Proteína C9orf72/imunologia , Sistemas CRISPR-Cas , Linhagem Celular Tumoral , Demência Frontotemporal/genética , Demência Frontotemporal/imunologia , Demência Frontotemporal/metabolismo , Edição de Genes , Expressão Gênica , Células HEK293 , Humanos , Lisossomos/genética , Lisossomos/metabolismo , Lisossomos/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Osteoblastos/metabolismo , Osteoblastos/ultraestrutura , Fagossomos/genética , Fagossomos/metabolismo , Fagossomos/ultraestrutura , Células RAW 264.7RESUMO
Parkinson's disease is a neurodegenerative disorder with motor symptoms linked to the loss of dopaminergic neurons in the substantia nigra compacta. Although the mechanisms that trigger the loss of dopaminergic neurons are unclear, mitochondrial dysfunction and inflammation are thought to have key roles1,2. An early-onset form of Parkinson's disease is associated with mutations in the PINK1 kinase and PRKN ubiquitin ligase genes3. PINK1 and Parkin (encoded by PRKN) are involved in the clearance of damaged mitochondria in cultured cells4, but recent evidence obtained using knockout and knockin mouse models have led to contradictory results regarding the contributions of PINK1 and Parkin to mitophagy in vivo5-8. It has previously been shown that PINK1 and Parkin have a key role in adaptive immunity by repressing presentation of mitochondrial antigens9, which suggests that autoimmune mechanisms participate in the aetiology of Parkinson's disease. Here we show that intestinal infection with Gram-negative bacteria in Pink1-/- mice engages mitochondrial antigen presentation and autoimmune mechanisms that elicit the establishment of cytotoxic mitochondria-specific CD8+ T cells in the periphery and in the brain. Notably, these mice show a sharp decrease in the density of dopaminergic axonal varicosities in the striatum and are affected by motor impairment that is reversed after treatment with L-DOPA. These data support the idea that PINK1 is a repressor of the immune system, and provide a pathophysiological model in which intestinal infection acts as a triggering event in Parkinson's disease, which highlights the relevance of the gut-brain axis in the disease10.
Assuntos
Infecções por Enterobacteriaceae/microbiologia , Infecções por Enterobacteriaceae/fisiopatologia , Intestinos/microbiologia , Doença de Parkinson/genética , Doença de Parkinson/microbiologia , Proteínas Quinases/deficiência , Proteínas Quinases/genética , Animais , Apresentação de Antígeno/imunologia , Autoantígenos/imunologia , Axônios/patologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/patologia , Citrobacter rodentium/imunologia , Citrobacter rodentium/patogenicidade , Modelos Animais de Doenças , Neurônios Dopaminérgicos/imunologia , Neurônios Dopaminérgicos/patologia , Infecções por Enterobacteriaceae/imunologia , Infecções por Enterobacteriaceae/patologia , Feminino , Intestinos/imunologia , Intestinos/patologia , Levodopa/uso terapêutico , Masculino , Camundongos , Mitocôndrias/imunologia , Mitocôndrias/patologia , Neostriado/imunologia , Neostriado/microbiologia , Neostriado/patologia , Neostriado/fisiopatologia , Doença de Parkinson/tratamento farmacológico , Doença de Parkinson/fisiopatologia , Proteínas Quinases/imunologia , Ubiquitina-Proteína Ligases/deficiência , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/imunologiaRESUMO
It has been over 20 years since the identification of the first GTPases that regulate mitochondrial fusion in drosophila, yeast, and mammalian cells. While the molecular identification of these players solidified the new field of mitochondrial dynamics, cell imaging had established the dynamic properties of mitochondria over a century before. The genetic dissection of mitochondrial fusion, fission, and positioning within cells cemented our understanding of the essential nature of this plasticity in health and disease. Loss of either mitochondrial fusion or fission causes embryonic lethality in mice, and mutations in a number of the core fusion/fission machines were identified in patients with neurodegenerative disease. From these early studies, there has been a rapid expansion of research into mitochondrial dynamics within diverse fields of interest, in various model systems. This review will focus on recent work investigating the mechanisms of mitochondrial fusion, where new findings are challenging some longstanding assumptions. We hope to highlight some essential remaining questions and generate a framework for future studies.
Assuntos
Mitocôndrias/metabolismo , Dinâmica Mitocondrial , Animais , Estresse do Retículo Endoplasmático , Humanos , Modelos Biológicos , Doenças Neurodegenerativas/patologia , Especificidade de ÓrgãosRESUMO
Dynamin-related protein 1 (Drp1) constricts mitochondria as a mechanochemical GTPase during mitochondrial division. The Drp1 gene contains several alternative exons and produces multiple isoforms through RNA splicing. Here we performed a systematic analysis of Drp1 transcripts in different mouse tissues and identified a previously uncharacterized isoform that is highly enriched in the brain. This Drp1 isoform is termed Drp1ABCD because it contains four alterative exons: A, B, C, and D. Remarkably, Drp1ABCD is located at lysosomes, late endosomes, and the plasma membrane in addition to mitochondria. Furthermore, Drp1ABCD is concentrated at the interorganelle interface between mitochondria and lysosomes/late endosomes. The localizations of Drp1ABCD at lysosomes, late endosomes, and the plasma membrane require two exons, A and B, that are present in the GTPase domain. Drp1ABCD assembles onto these membranes in a manner that is regulated by its oligomerization and GTP hydrolysis. Experiments using lysosomal inhibitors show that the association of Drp1ABCD with lysosomes/late endosomes depends on lysosomal pH but not their protease activities. Thus, Drp1 may connect mitochondria to endosomal-lysosomal pathways in addition to mitochondrial division.
Assuntos
Encéfalo/metabolismo , Membrana Celular/metabolismo , Dinaminas/metabolismo , Endossomos/metabolismo , Lisossomos/metabolismo , Animais , Dinaminas/análise , Camundongos , Mitocôndrias/metabolismo , Peroxissomos/metabolismo , Isoformas de Proteínas/análise , Isoformas de Proteínas/metabolismoRESUMO
In this Guest Editorial, Heidi McBride introduces our special issue on membranes with a discussion of the contribution of mitochondria to the emergence of the endomembrane system.
Assuntos
Membranas Intracelulares/fisiologia , Mitocôndrias/metabolismo , Mitocôndrias/fisiologia , Animais , Evolução Biológica , Eucariotos , Evolução Molecular , Humanos , Membranas Mitocondriais/metabolismo , Membranas Mitocondriais/fisiologiaRESUMO
Mitochondrial fusion occurs in many eukaryotes, including animals, plants, and fungi. It is essential for cellular homeostasis, and yet the underlying mechanisms remain elusive. Comparative analyses and phylogenetic reconstructions revealed that fungal Fzo1 and animal Mitofusin proteins are highly diverged from one another and lack strong sequence similarity. Bioinformatic analysis showed that fungal Fzo1 proteins exhibit two predicted transmembrane domains, whereas metazoan Mitofusins contain only a single transmembrane domain. This prediction contradicts the current models, suggesting that both animal and fungal proteins share one topology. This newly predicted topology of Mfn1 and Mfn2 was demonstrated biochemically, confirming that the C-terminal, redox-sensitive cysteine residues reside within the intermembrane space (IMS). Functional experiments established that redox-mediated disulfide modifications within the IMS domain are key modulators of reversible Mfn oligomerization that drives fusion. Together, these results lead to a revised understanding of Mfns as single-spanning outer membrane proteins with an Nout-Cin orientation, providing functional insight into the IMS contribution to redox-regulated fusion events.
Assuntos
GTP Fosfo-Hidrolases/metabolismo , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Animais , Biologia Computacional , Células HEK293 , Humanos , Dinâmica Mitocondrial , Oxirredução , Saccharomyces cerevisiae/metabolismoRESUMO
Discoveries spanning several decades have pointed to vital membrane lipid trafficking pathways involving both vesicular and non-vesicular carriers. But the relative contributions for distinct membrane delivery pathways in cell growth and organelle biogenesis continue to be a puzzle. This is because lipids flow from many sources and across many paths via transport vesicles, non-vesicular transfer proteins, and dynamic interactions between organelles at membrane contact sites. This forum presents our latest understanding, appreciation, and queries regarding the lipid transport mechanisms necessary to drive membrane expansion during organelle biogenesis and cell growth.