RESUMO
OBJECTIVE: A prevailing concept in neuroscience has been that the adult mammalian central nervous system is incapable of restorative axon regeneration. Recent evidence, however, has suggested that reactivation of intrinsic cellular programs regulated by protein kinase B (Akt)/mammalian target of rapamycin (mTor) signaling may restore this ability. METHODS: To assess this possibility in the brain, we have examined the ability of adenoassociated virus (AAV)-mediated transduction of dopaminergic neurons of the substantia nigra (SN) with constitutively active forms of the kinase Akt and the GTPase Ras homolog enriched in brain (Rheb) to induce regrowth of axons after they have been destroyed by neurotoxin lesion. RESULTS: Both constitutively active myristoylated Akt and hRheb(S16H) induce regrowth of axons from dopaminergic neurons to their target, the striatum. Histological analysis demonstrates that these new axons achieve morphologically accurate reinnervation. In addition, functional reintegration into target circuitry is achieved, as indicated by partial behavioral recovery. INTERPRETATION: We conclude that regrowth of axons within the adult nigrostriatal projection, a system that is prominently affected in Parkinson's disease, can be achieved by activation of Akt/mTor signaling in surviving endogenous mesencephalic dopaminergic neurons by viral vector transduction.
Assuntos
Axônios/fisiologia , Dopamina/fisiologia , Proteínas Monoméricas de Ligação ao GTP/administração & dosagem , Regeneração Nervosa/fisiologia , Neuropeptídeos/administração & dosagem , Proteínas Proto-Oncogênicas c-akt/administração & dosagem , Transdução de Sinais , Animais , Axônios/metabolismo , Dependovirus/genética , Vetores Genéticos/administração & dosagem , Vetores Genéticos/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas Monoméricas de Ligação ao GTP/genética , Regeneração Nervosa/genética , Neurônios/citologia , Neurônios/patologia , Neurônios/virologia , Neuropeptídeos/genética , Doença de Parkinson/genética , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Proteínas Proto-Oncogênicas c-akt/genética , Proteína Enriquecida em Homólogo de Ras do Encéfalo , Transdução de Sinais/genética , Substância Negra/metabolismo , Substância Negra/patologia , Substância Negra/virologiaRESUMO
During mitosis the interconnected Golgi complex of animal cells breaks down to produce both finely dispersed elements and discrete vesiculotubular structures. The endoplasmic reticulum (ER) plays a controversial role in generating these partitioning intermediates and here we highlight the importance of mitotic ER export arrest in this process. We show that experimental inhibition of ER export (by microinjecting dominant negative Sar1 mutant proteins) is sufficient to induce and maintain transformation of Golgi cisternae to vesiculotubular remnants during interphase and telophase, respectively. We also show that buds on the ER, ER exit sites and COPII vesicles are markedly depleted in mitotic cells and COPII components Sec23p, Sec24p, Sec13p and Sec31p redistribute into the cytosol, indicating ER export is inhibited at an early stage. Finally, we find a markedly uneven distribution of Golgi residents over residual exit sites of metaphase cells, consistent with tubulovesicular Golgi remnants arising by fragmentation rather than redistribution via the ER. Together, these results suggest selective recycling of Golgi residents, combined with prebudding cessation of ER export, induces transformation of Golgi cisternae to vesiculotubular remnants in mitotic cells. The vesiculotubular Golgi remnants, containing populations of slow or nonrecycling Golgi components, arise by fragmentation of a depleted Golgi ribbon independently from the ER.
