RESUMEN
Proapoptotic BCL-2 proteins converge upon the outer mitochondrial membrane (OMM) to promote mitochondrial outer membrane permeabilization (MOMP) and apoptosis. Here we investigated the mechanistic relationship between mitochondrial shape and MOMP and provide evidence that BAX requires a distinct mitochondrial size to induce MOMP. We utilized the terminal unfolded protein response pathway to systematically define proapoptotic BCL-2 protein composition after stress and then directly interrogated their requirement for a productive mitochondrial size. Complementary biochemical, cellular, in vivo, and ex vivo studies reveal that Mfn1, a GTPase involved in mitochondrial fusion, establishes a mitochondrial size that is permissive for proapoptotic BCL-2 family function. Cells with hyperfragmented mitochondria, along with size-restricted OMM model systems, fail to support BAX-dependent membrane association and permeabilization due to an inability to stabilize BAXα9·membrane interactions. This work identifies a mechanistic contribution of mitochondrial size in dictating BAX activation, MOMP, and apoptosis.
Asunto(s)
GTP Fosfohidrolasas/genética , Mitocondrias Hepáticas/genética , Membranas Mitocondriales/metabolismo , Forma de los Orgánulos/genética , Proteína X Asociada a bcl-2/genética , Animales , Apoptosis , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteína 11 Similar a Bcl2 , GTP Fosfohidrolasas/metabolismo , Regulación de la Expresión Génica , Potencial de la Membrana Mitocondrial/genética , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Mitocondrias Hepáticas/metabolismo , Mitocondrias Hepáticas/ultraestructura , Dinámicas Mitocondriales/genética , Membranas Mitocondriales/ultraestructura , Permeabilidad , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal , Liposomas Unilamelares/química , Liposomas Unilamelares/metabolismo , Proteína Destructora del Antagonista Homólogo bcl-2/genética , Proteína Destructora del Antagonista Homólogo bcl-2/metabolismo , Proteína X Asociada a bcl-2/metabolismoRESUMEN
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.