Downregulation of the Ras-mitogen-activated protein kinase pathway by the EphB2 receptor tyrosine kinase is required for ephrin-induced neurite retraction
Downregulation of the Ras-mitogen-activated protein kinase pathway by the EphB2 receptor tyrosine kinase is required for ephrin-induced neurite retraction
复制标题
DOI：
10.1128/mcb.21.21.7429-7441.2001
复制
发表时间：
2001-11-01
影响因子：
5.3
通讯作者：
Pawson, T
中科院分区：
文献类型：
--
作者：
Elowe, S;Holland, SJ;Pawson, T
聚集型ephrin-B1激活EphB2受体酪氨酸激酶可诱导分化的NG108神经元细胞生长锥塌陷和神经突缩回。我们研究了与ephb2诱导的这些神经元细胞骨架重组相关的细胞质信号事件。我们发现，与其他受体酪氨酸激酶不同，EphB2诱导gtp结合Ras的显著下调，从而导致细胞外信号调节激酶（ERK）丝裂原活化蛋白激酶（MAPK）途径的下调。在COS-1细胞中，内源性EphB2的刺激对Ras-MAPK通路有类似的抑制作用。ephrin B1刺激NG108神经元细胞诱导Ras失活，需要EphB2酪氨酸激酶活性，并被截断形式的p120-Ras gtpase激活蛋白（p120-RasGAP）阻断，这表明EphB2通过SH2结构域蛋白p120-RasGAP信号抑制Ras- mapk通路。抑制Ras活性似乎在功能上很重要，因为Ras的组成型活性变体的表达会损害EphB2诱导神经突收缩的能力。此外，EphB2可减弱NG108细胞附着纤维连接蛋白诱导的ERK活化升高，表明EphB2受体可调节整合素信号传导至Ras GTPase。这些结果表明，EphB2的主要功能是使Ras-MAPK通路失活，从而促进细胞骨架重组和神经元生长锥的粘附反应。EphB2是数量最多的受体酪氨酸激酶家族的成员。
Activation of the EphB2 receptor tyrosine kinase by clustered ephrin-B1 induces growth cone collapse and neurite retraction in differentiated NG108 neuronal cells. We have investigated the cytoplasmic signaling events associated with EphB2-induced cytoskeletal reorganization in these neuronal cells. We find that unlike other receptor tyrosine kinases, EphB2 induces a pronounced downregulation of GTP-bound Ras and consequently of the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. A similar inhibition of the Ras-MAPK pathway was observed on stimulation of endogenous EphB2 in COS-1 cells. Inactivation of Ras, induced by ephrin B1 stimulation of NG108 neuronal cells, requires EphB2 tyrosine kinase activity and is blocked by a truncated form of p120-Ras GTPase-activating protein (p120-RasGAP), suggesting that EphB2 signals through the SH2 domain protein p120-RasGAP to inhibit the Ras-MAPK pathway. Suppression of Ras activity appears functionally important, since expression of a constitutively active variant of Ras impaired the ability of EphB2 to induce neurite retraction. In addition, EphB2 attenuated the elevation in ERK activation induced by attachment of NG108 cells to fibronectin, indicating that the EphB2 receptor can modulate integrin signaling to the Ras GTPase. These results suggest that a primary function of EphB2, a member of the most populous family of receptor tyrosine kinases, is to inactivate the Ras-MAPK pathway in a fashion that contributes to cytoskeletal reorganization and adhesion responses in neuronal growth cones.