Molecular dissection of the semaphorin 4D receptor Plexin-B1-stimulated R-Ras GTPase-activating protein activity and neurite remodeling in hippocampal neurons
Molecular dissection of the semaphorin 4D receptor Plexin-B1-stimulated R-Ras GTPase-activating protein activity and neurite remodeling in hippocampal neurons
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DOI：
10.1523/jneurosci.3257-04.2004
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发表时间：
2004-12-15
影响因子：
5.3
通讯作者：
Negishi, M
中科院分区：
文献类型：
--
作者：
Oinuma, I;Katoh, H;Negishi, M
丛蛋白充当排斥性轴突引导分子信号蛋白的受体。信号蛋白 4D (Sema4D) 受体的胞质结构域 Plexin-B1 具有两个独立的 Ras GTP 酶激活蛋白 (GAP) 同源结构域：C1 和 C2。最近，我们报道了 Rho 家族小 GTPase Rnd1 与 Plexin-B1 结合，Plexin-B1-Rnd1 复合物刺激 R-Ras 的 GTPase 活性，响应 Sema4D 诱导海马神经元生长锥塌陷。然而，Plexin-B1 表现出 GAP 活性的分子机制仍不清楚。在本报告中，研究了 Rnd1 和 Sema4D 在 Plexin-B1 刺激的 R-Ras GAP 活性和神经突重塑中的关键作用。含有 C1 结构域的 Plexin-B1 胞质结构域的 N 端区域与含有 C2 结构域的 C 端区域相互作用，而 Rnd1 会破坏这种相互作用。另一方面，Sema4D 诱导 Rnd1 结合的 Plexin-B1 聚集，同时细胞中 R-Ras 失活。在 Rnd1 存在的情况下，Plexin-B1 重组胞质结构域的抗体聚类会触发 R-Ras GAP 活性。 Plexin-B1 胞外结构域的缺失会导致受体的配体独立聚集，使受体在 Rnd1 存在的情况下持续活跃，并诱导 COS-7 细胞收缩并抑制海马神经元中的神经突生长。这些结果表明，Rnd1 打开 Plexin-B1 的两个 R-Ras GAP 结构域，并且 Sema4D 诱导的受体聚集刺激海马神经元中的 R-Ras GAP 活性和神经突重塑。
Plexins serve as receptors for repulsive axonal guidance molecules semaphorins. The cytoplasmic domain of the semaphorin 4D (Sema4D) receptor, Plexin-B1 has two separated Ras GTPase-activating protein (GAP)-homologous domains, C1 and C2. Recently, we reported that the Rho family small GTPase Rnd1 associates with Plexin-B1, and the Plexin-B1-Rnd1 complex stimulates GTPase activity of R-Ras, inducing growth cone collapse in hippocampal neurons in response to Sema4D. However, the molecular mechanisms by which Plexin-B1 exhibits the GAP activity remain unclear. In this report, critical roles of Rnd1 and Sema4D in Plexin-B1-stimulated R-Ras GAP activity and neurite remodeling were examined. The N-terminal region of the cytoplasmic domain of Plexin-B1 containing the C1 domain interacts with the C-terminal region containing the C2 domain, and Rnd1 disrupts this interaction. On the other hand, Sema4D induces clustering of Rnd1-bound Plexin-B1, in parallel with inactivation of R-Ras in cells. Antibody clustering of the recombinant cytoplasmic domain of Plexin-B1 in the presence of Rnd1 triggers the R-Ras GAP activity. Deletion of the extracellular domain of Plexin-B1 causes ligand-independent clustering of the receptor, rendering the receptor constitutively active in the presence of Rnd1, and induces contraction of COS-7 cells and inhibition of neurite outgrowth in hippocampal neurons. These results indicate that Rnd1 opens the two R-Ras GAP domains of Plexin-B1, and Sema4D-induced receptor clustering stimulates R-Ras GAP activity and neurite remodeling in hippocampal neurons.