Cytokine expression and AIF-1-mediated activation of Rac2 in vascular smooth muscle cells: a role for Rac2 in VSMC activation.
Cytokine expression and AIF-1-mediated activation of Rac2 in vascular smooth muscle cells: a role for Rac2 in VSMC activation.
复制标题
DOI：
10.1152/ajpcell.00334.2006
复制
发表时间：
2007-02
期刊：
影响因子：
--
通讯作者：
Ying Tian;M. Autieri
中科院分区：
文献类型：
--
作者：
Ying Tian;M. Autieri
同种异体移植物炎症因子-1(AIF-1)是一种胞浆内钙结合的炎症反应支架蛋白，参与血管平滑肌细胞(VSMC)的迁移和增殖。本研究的目的是研究可能调节VSMC激活的AIF-1功能蛋白相互作用。通过细菌双杂交筛选，我们鉴定了AIF-1与小GTP酶rac2之间的分子相互作用，并通过下拉和共定位实验证实了这一点。这是意想不到的，因为rac2的表达被认为仅限于造血细胞。Rac2/AIF-1的相互作用是功能性的，因为功能丧失、点突变的AIF-1不与Rac2相互作用；Rac2与AIF-1共存于VSMC的细胞质中，并在血小板衍生生长因子刺激下共定位到板足；AIF-1在VSMC中的表达导致Rac2激活。由于Rac2在VSMC中的功能还没有被描述，所以我们主要研究它在这些细胞中的功能。炎性细胞因子可诱导VSMC中Rac2蛋白的表达，VSMC中的Rac2激活也受炎性细胞因子的影响。Rac2的表达和激活模式不同于普遍表达的rac1。我们推测，rac2参与了VSMC的激活。逆转录病毒在原代VSMC中的过表达导致NADPH氧化级联反应的迁移和激活，并增加了rac2效应蛋白pak1及其近端效应蛋白ERK1/2和p38的激活(P<；0.05对于ALL)。本研究的主要观点表明，AIF-1和rac2在VSMC中的功能相互作用导致了rac2的激活，而rac2在炎症驱动的VSMC损伤反应中具有潜在的作用。
Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein involved in vascular smooth muscle cell (VSMC) migration and proliferation. The objective of this study is to characterize AIF-1 functional protein interactions that may regulate VSMC activation. Through use of a bacterial two-hybrid screen, we identified a molecular interaction between AIF-1 and the small GTPase, Rac2, which was verified by pull-down and colocalization experiments. This was unexpected in that Rac2 expression had been considered to be restricted to hematopoietic cells. The Rac2/AIF-1 interaction is functional, in that a loss-of-function, point-mutated AIF-1 does not interact with Rac2; Rac2 colocalizes with AIF-1 in the cytoplasm of VSMC and cotranslocates to lamellopodia upon platelet-derived growth factor stimulation; and AIF-1 expression in VSMC leads to Rac2 activation. Because Rac2 function in VSMC had not been described, we focused on characterization of its function in these cells. Rac2 protein expression in VSMC is inducible by inflammatory cytokines, and Rac2 activation in VSMC is also responsive to inflammatory cytokines. Rac2 expression and activation patterns differ from the ubiquitously expressed Rac1. We hypothesized that Rac2 participates in VSMC activation. Retroviral overexpression of Rac2 in primary VSMC leads to increased migration, activation of the NADPH oxidation cascade, and increased activation of the Rac2 effector protein Pak1 and its proximal effectors, ERK1/2, and p38 (P < 0.05 for all). The major points of this study indicate a functional interaction between AIF-1 and Rac2 in VSMC leading to Rac2 activation and a potential function for Rac2 in inflammation-driven VSMC response to injury.