RESUMO
CNS myelin inhibits axon growth due to the expression of several growth-inhibitory proteins, including myelin-associated glycoprotein, oligodendrocyte myelin glycoprotein and Nogo. Myelin-associated inhibitory proteins activate rho GTPase in responsive neurons. Rho kinase (ROCK) has been implicated as a critical rho effector in this pathway due to the ability of the pharmacological inhibitor Y-27632 to circumvent myelin-dependent inhibition. Y-27632, however, inhibits the activity of additional kinases. Using three independent approaches, we provide direct evidence that ROCKII is activated in response to the myelin-associated inhibitor Nogo. We demonstrate that Nogo treatment enhances ROCKII translocation to the cellular membrane in PC12 cells and enhances ROCKII kinase activity towards an in vitro substrate. In addition, Nogo treatment enhances phosphorylation of myosin light chain II, a known ROCK substrate. Further, we demonstrate that primary dorsal root ganglia neurons can be rendered insensitive to the inhibitory effects of myelin via infection with dominant negative ROCK. Together these data provide direct evidence for a rho-ROCK-myosin light chain-II signaling cascade in response to myelin-associated inhibitors.
Assuntos
Inibidores do Crescimento/metabolismo , Proteínas da Mielina/metabolismo , Sistema Nervoso/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Amidas/farmacologia , Animais , Miosinas Cardíacas/metabolismo , Células Cultivadas , Inibidores Enzimáticos/farmacologia , Gânglios Espinais/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Proteínas da Mielina/farmacologia , Cadeias Leves de Miosina/metabolismo , Regeneração Nervosa/fisiologia , Plasticidade Neuronal/fisiologia , Proteínas Nogo , Células PC12 , Fosforilação/efeitos dos fármacos , Proteína Quinase C/metabolismo , Proteínas Serina-Treonina Quinases/genética , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , Piridinas/farmacologia , Ratos , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologia , Proteínas rho de Ligação ao GTP/metabolismo , Quinases Associadas a rhoRESUMO
Trauma in the adult mammalian central nervous system (CNS) has devastating clinical consequences due to the failure of injured axons to spontaneously regenerate. Over 20 years ago, pioneering work demonstrated that the non-permissive nature of CNS myelin for axon outgrowth contributes to this regenerative failure. Over the past few years, tremendous progress has been made in our understanding of the inhibitory components of CNS myelin, the axonal receptors that respond to these cues, and the intracellular signaling cascades mediating axon outgrowth inhibition. Several approaches designed to antagonize molecular mediators of axon inhibition have been tested in an effort to promote regenerative growth after CNS injury. These studies have validated the role of many candidate proteins in axon outgrowth inhibition; however, other approaches such as the generation of knockout mice for myelin-associated inhibitors have created new questions in the field.
