Lu L, Annerén C, Reedquist K A, Bos J L, Welsh M
Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
Exp Cell Res. 2000 Sep 15;259(2):370-7. doi: 10.1006/excr.2000.4984.
The Src homology 2 (SH2) domain adaptor protein Shb has been shown to transmit NGF- and FGF-2-dependent differentiation signals in PC12 cells. To study if this involves signaling through the small GTPase Rap1, Rap1 activity was assessed in Shb-overexpressing PC12 cells. We demonstrate that NGF and EGF induce Rap1 activation in PC12-Shb cells, while FGF-2 fails to do so. However, PC12 cells expressing Shb with an inactivated SH2 domain do not respond to NGF stimulation with Rap1 activation. The CrkII SH2 domain interacts with Shb and a 130- to 135-kDa phosphotyrosine protein present mainly in PC12-Shb cells and these interactions may thus relate to the effect of Shb on Rap1 activation. Transient expression of RalGDS-RBD or Rap1GAP to block the Rap1 pathway reduces the NGF-dependent neurite outgrowth in PC12-Shb cells. These results suggest a role of Shb in NGF-dependent Rap1 signaling and this pathway may be of significance for neurite outgrowth under certain conditions.
Src同源2（SH2）结构域衔接蛋白Shb已被证明可在PC12细胞中传递神经生长因子（NGF）和碱性成纤维细胞生长因子2（FGF-2）依赖性的分化信号。为了研究这是否涉及通过小GTP酶Rap1进行信号传导，我们在过表达Shb的PC12细胞中评估了Rap1的活性。我们证明，NGF和表皮生长因子（EGF）可诱导PC12-Shb细胞中的Rap1激活，而FGF-2则不能。然而，表达具有失活SH2结构域的Shb的PC12细胞对NGF刺激没有Rap1激活反应。CrkII的SH2结构域与Shb以及一种主要存在于PC12-Shb细胞中的130至135 kDa的磷酸酪氨酸蛋白相互作用，因此这些相互作用可能与Shb对Rap1激活的影响有关。瞬时表达RalGDS-RBD或Rap1GAP以阻断Rap1途径可减少PC12-Shb细胞中NGF依赖性的神经突生长。这些结果表明Shb在NGF依赖性Rap1信号传导中起作用，并且该途径在某些条件下可能对神经突生长具有重要意义。
