Burbelo P D, Miyamoto S, Utani A, Brill S, Yamada K M, Hall A, Yamada Y
Laboratory of Developmental Biology, NIDR, National Institutes of Health, Bethesda, Maryland 20892-4370, USA.
J Biol Chem. 1995 Dec 29;270(52):30919-26. doi: 10.1074/jbc.270.52.30919.
p120GAP forms distinct complexes with two phosphoproteins, p62 and p190. Here we have cloned a cDNA encoding a protein with 51% amino acid identity to p190 (hereafter designated p190-A) and have designated it p190-B. The N-terminal portion of p190-B contained several motifs characteristic of a GTPase domain, while its C terminus contained a Rho GAP domain. A recombinant Rho GAP domain polypeptide showed GAP activity for RhoA, Rac1, and G25K/CDC42Hs. Immunoprecipitation and immunofluorescence studies demonstrated that p190-B protein was expressed in a variety of cells and was localized diffusely in the cytoplasm and in fibrillar patterns that co-localized with the alpha 5 beta 1 integrin receptor for fibronectin. Adhesion of fibronectin-coated latex beads to cells resulted in recruitment of significant amounts of p190-B and Rho to the plasma membrane beneath the site of bead binding. In contrast, beads coated with polylysine or concanavalin A were unable to recruit p190-B or Rho. Additionally, anti-beta 1 or anti-alpha 5 integrin antibody-coated beads were also able to recruit large amounts of p190-B and Rho. These results identify a novel second member of the p190 family and establish the existence of a novel transmembrane link between integrins and a new protein p190-B and Rho.
p120GAP与两种磷蛋白p62和p190形成不同的复合物。在此，我们克隆了一个编码与p190具有51%氨基酸同一性的蛋白质的cDNA（此后称为p190-A），并将其命名为p190-B。p190-B的N端部分包含几个GTPase结构域特有的基序，而其C端包含一个Rho GAP结构域。一种重组Rho GAP结构域多肽对RhoA、Rac1和G25K/CDC42Hs显示出GAP活性。免疫沉淀和免疫荧光研究表明，p190-B蛋白在多种细胞中表达，广泛分布于细胞质中，并以与纤连蛋白的α5β1整合素受体共定位的纤维状模式存在。纤连蛋白包被的乳胶珠与细胞的粘附导致大量的p190-B和Rho募集到珠子结合位点下方的质膜上。相比之下，聚赖氨酸或伴刀豆球蛋白A包被的珠子无法募集p190-B或Rho。此外，抗β1或抗α5整合素抗体包被的珠子也能够募集大量的p190-B和Rho。这些结果鉴定了p190家族的一个新的第二个成员，并确立了整合素与新蛋白p190-B和Rho之间存在一种新的跨膜联系。
