Meakin S O, MacDonald J I
John P. Robarts Research Institute, Department of Biochemistry, University of Western Ontario, London, Canada.
J Neurochem. 1998 Nov;71(5):1875-88. doi: 10.1046/j.1471-4159.1998.71051875.x.
We have generated a novel rat TrkA receptor mutant (TrkAS3) by deletion of five conserved residues (493IMENP497) in the juxtamembrane domain. TrkAS3 receptors cannot support nerve growth factor (NGF)-induced cell cycle arrest or neuronal differentiation but retain cell survival responses as well as Ras-dependent mitogenic signaling. Cells of the nnr5 line stably expressing TrkAS3 induce NGF-dependent SHC phosphorylation and phosphatidylinositol 3-kinase, phospholipase Cgamma-1, and prolonged mitogen-activated protein kinase activation to absolute levels comparable to those in PC12 cells. Although the stoichiometry of TrkAS3-SHC binding is reduced, cells overexpressing TrkAS3 exhibit NGF-dependent SHC-Grb-2/Sos binding, essential for Ras activation, as well as NGF-dependent SNT phosphorylation to absolute levels comparable to those in PC12 cells. Collectively, these data suggest that the TrkAS3 deletion either directly affects a novel Ras-independent TrkA binding protein or that the decrease in TrkAS3-SHC association affects a Ras-independent SHC binding protein essential for cell cycle arrest and/or neurite outgrowth.
我们通过缺失近膜结构域中的五个保守残基（493IMENP497）生成了一种新型大鼠TrkA受体突变体（TrkAS3）。TrkAS3受体不能支持神经生长因子（NGF）诱导的细胞周期停滞或神经元分化，但保留细胞存活反应以及Ras依赖性有丝分裂信号传导。稳定表达TrkAS3的nnr5系细胞诱导NGF依赖性SHC磷酸化以及磷脂酰肌醇3激酶、磷脂酶Cγ-1，并使丝裂原活化蛋白激酶的激活延长至与PC12细胞相当的绝对水平。尽管TrkAS3-SHC结合的化学计量减少，但过表达TrkAS3的细胞表现出NGF依赖性SHC-Grb-2/Sos结合（这对Ras激活至关重要）以及NGF依赖性SNT磷酸化至与PC12细胞相当的绝对水平。总体而言，这些数据表明，TrkAS3缺失要么直接影响一种新型的不依赖Ras的TrkA结合蛋白，要么TrkAS3-SHC缔合的减少影响了一种对细胞周期停滞和/或神经突生长至关重要的不依赖Ras的SHC结合蛋白。
