RESUMO
Compartmentalization of membrane transport and signaling processes is of pivotal importance to eukaryotic cell function. While plasma membrane compartmentalization and dynamics are well known to depend on the scaffolding function of septin GTPases, the roles of septins at intracellular membranes have remained largely elusive. Here, we show that the structural and functional integrity of the Golgi depends on its association with a septin 1 (SEPT1)-based scaffold, which promotes local microtubule nucleation and positioning of the Golgi. SEPT1 function depends on the Golgi matrix protein GM130 (also known as GOLGA2) and on centrosomal proteins, including CEP170 and components of γ-tubulin ring complex (γ-Turc), to facilitate the perinuclear concentration of Golgi membranes. Accordingly, SEPT1 depletion triggers a massive fragmentation of the Golgi ribbon, thereby compromising anterograde membrane traffic at the level of the Golgi.
Assuntos
Autoantígenos/genética , Centrossomo/metabolismo , Complexo de Golgi/metabolismo , Proteínas de Membrana/genética , Proteínas Associadas aos Microtúbulos/genética , Microtúbulos/metabolismo , Septinas/genética , Células 3T3-L1 , Animais , Autoantígenos/metabolismo , Transporte Biológico , Compartimento Celular , Linhagem Celular , Centrossomo/ultraestrutura , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Regulação da Expressão Gênica , Complexo de Golgi/ultraestrutura , Células HEK293 , Células HeLa , Humanos , Células Jurkat/metabolismo , Células Jurkat/ultraestrutura , Proteínas de Membrana/metabolismo , Camundongos , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Epitélio Pigmentado da Retina/citologia , Epitélio Pigmentado da Retina/metabolismo , Septinas/antagonistas & inibidores , Septinas/metabolismo , Transdução de SinaisRESUMO
Mitochondrial dysfunction manifests as different neurological diseases, but the mechanisms underlying the clinical variability remain poorly understood. To clarify whether different brain cells have differential sensitivity to mitochondrial dysfunction, we induced mitochondrial DNA (mtDNA) depletion in either neurons or astrocytes of mice, by inactivating Twinkle (TwKO), the replicative mtDNA helicase. Here we show that astrocytes, the most abundant cerebral cell type, are chronically activated upon mtDNA loss, leading to early-onset spongiotic degeneration of brain parenchyma, microgliosis and secondary neurodegeneration. Neuronal mtDNA loss does not, however, cause symptoms until 8 months of age. Findings in astrocyte-TwKO mimic neuropathology of Alpers syndrome, infantile-onset mitochondrial spongiotic encephalopathy caused by mtDNA maintenance defects. Our evidence indicates that (1) astrocytes are dependent on mtDNA integrity; (2) mitochondrial metabolism contributes to their activation; (3) chronic astrocyte activation has devastating consequences, underlying spongiotic encephalopathy; and that (4) astrocytes are a potential target for interventions.