Brown Matthew D, Bry Lynn, Li Zhigang, Sacks David B
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Thorn 530, Boston, Massachusetts 02115, USA.
J Biol Chem. 2008 Dec 12;283(50):35212-22. doi: 10.1074/jbc.M803477200. Epub 2008 Sep 22.
During infection, enteropathogenic Escherichia coli (EPEC) injects effector proteins into the host cell to manipulate the actin cytoskeleton and promote formation of actin pedestals. IQGAP1 is a multidomain protein that participates in numerous cellular functions, including Rac1/Cdc42 and Ca(2+)/calmodulin signaling and actin polymerization. Here we report that IQGAP1, Ca(2+), and calmodulin modulate actin pedestal formation by EPEC. Infection with EPEC promotes both the interaction of IQGAP1 with calmodulin and the localization of IQGAP1 and calmodulin to actin pedestals while reducing the interaction of IQGAP1 with Rac1 and Cdc42. IQGAP1-null fibroblasts display a reduced polymerization of actin in response to EPEC. In addition, antagonism of calmodulin or chelation of intracellular Ca(2+) reduces EPEC-dependent actin polymerization. Furthermore, IQGAP1 specifically interacts with Tir in vitro and in cells. Together these data identify IQGAP1, Ca(2+), and calmodulin as a novel signaling complex regulating actin pedestal formation by EPEC.
在感染过程中，肠致病性大肠杆菌（EPEC）将效应蛋白注入宿主细胞，以操纵肌动蛋白细胞骨架并促进肌动蛋白基座的形成。IQGAP1是一种多结构域蛋白，参与多种细胞功能，包括Rac1/Cdc42和Ca(2+)/钙调蛋白信号传导以及肌动蛋白聚合。在此我们报告，IQGAP1、Ca(2+)和钙调蛋白调节EPEC诱导的肌动蛋白基座形成。EPEC感染促进IQGAP1与钙调蛋白的相互作用以及IQGAP1和钙调蛋白在肌动蛋白基座上的定位，同时减少IQGAP1与Rac1和Cdc42的相互作用。缺乏IQGAP1的成纤维细胞对EPEC的反应显示肌动蛋白聚合减少。此外，钙调蛋白拮抗剂或细胞内Ca(2+)螯合剂可减少EPEC依赖的肌动蛋白聚合。此外，IQGAP1在体外和细胞中均特异性地与Tir相互作用。这些数据共同确定IQGAP1、Ca(2+)和钙调蛋白是一种新型信号复合物，可调节EPEC诱导的肌动蛋白基座形成。
