Dubreuil Catherine I, Winton Matthew J, McKerracher Lisa
Département de pathologie et biologie cellulaire, Université de Montréal, Montréal, QC H3T 1J4, Canada.
J Cell Biol. 2003 Jul 21;162(2):233-43. doi: 10.1083/jcb.200301080. Epub 2003 Jul 14.
Growth inhibitory proteins in the central nervous system (CNS) block axon growth and regeneration by signaling to Rho, an intracellular GTPase. It is not known how CNS trauma affects the expression and activation of RhoA. Here we detect GTP-bound RhoA in spinal cord homogenates and report that spinal cord injury (SCI) in both rats and mice activates RhoA over 10-fold in the absence of changes in RhoA expression. In situ Rho-GTP detection revealed that both neurons and glial cells showed Rho activation at SCI lesion sites. Application of a Rho antagonist (C3-05) reversed Rho activation and reduced the number of TUNEL-labeled cells by approximately 50% in both injured mouse and rat, showing a role for activated Rho in cell death after CNS injury. Next, we examined the role of the p75 neurotrophin receptor (p75NTR) in Rho signaling. After SCI, an up-regulation of p75NTR was detected by Western blot and observed in both neurons and glia. Treatment with C3-05 blocked the increase in p75NTR expression. Experiments with p75NTR-null mutant mice showed that immediate Rho activation after SCI is p75NTR dependent. Our results indicate that blocking overactivation of Rho after SCI protects cells from p75NTR-dependent apoptosis.
中枢神经系统（CNS）中的生长抑制蛋白通过向细胞内GTP酶Rho发出信号来阻断轴突生长和再生。目前尚不清楚中枢神经系统创伤如何影响RhoA的表达和激活。在这里，我们在脊髓匀浆中检测到结合GTP的RhoA，并报告在大鼠和小鼠中，脊髓损伤（SCI）在RhoA表达无变化的情况下使RhoA激活超过10倍。原位Rho-GTP检测显示，神经元和神经胶质细胞在脊髓损伤病变部位均表现出Rho激活。应用Rho拮抗剂（C3-05）可逆转Rho激活，并使受伤小鼠和大鼠中TUNEL标记细胞的数量减少约50%，表明激活的Rho在中枢神经系统损伤后的细胞死亡中起作用。接下来，我们研究了p75神经营养因子受体（p75NTR）在Rho信号传导中的作用。脊髓损伤后，通过蛋白质印迹法检测到p75NTR上调，并且在神经元和神经胶质细胞中均观察到。用C3-05处理可阻断p75NTR表达的增加。对p75NTR基因敲除突变小鼠的实验表明，脊髓损伤后Rho的立即激活依赖于p75NTR。我们的结果表明，阻断脊髓损伤后Rho的过度激活可保护细胞免受p75NTR依赖性凋亡。
