Indig F E, Diaz-Gonzalez F, Ginsberg M H
Department of Vascular Biology, The Scripps Research Institute, 10666 N. Torrey Pines Rd, La Jolla, CA 92307, USA.
Biochem J. 1997 Oct 1;327 ( Pt 1)(Pt 1):291-8. doi: 10.1042/bj3270291.
The platelet integrin, alphaIIbbeta3 (GPIIb-IIIa), and the tetraspanin, CD9, are integral membrane proteins that are abundant in platelet membranes. We have identified several proteins, including CD9, which were co-precipitated by anti-alphaIIbbeta3 antibody from untreated, resting platelets that were solubilized with the poly(oxyethylene) non-ionic detergent, Brij-35. Immunoblot and quantitative immunoprecipitation showed that the association of alphaIIbbeta3 with CD9 is specific and stoichiometric. The interaction between CD9 and alphaIIbbeta3 is probably hydrophobic, as Triton X-100 and hydrophobic detergents of the Brij series completely dissociated the CD9-alphaIIbbeta3 complex. Recombinant CD9 and alphaIIbbeta3 can associate after transfection into Chinese hamster ovary cells, as seen by co-immunoprecipitation and co-localization in the periphery of spreading cells and in the lamellipodia of cells plated on fibrinogen. This co-localization is absent from focal adhesions. Furthermore, anti-CD9-coated latex beads clustered alphaIIbbeta3 with CD9. This work indicates that the tetraspanin, CD9, is associated with beta3 integrins in resting platelets and transfected cells.
血小板整合素αIIbβ3（糖蛋白IIb-IIIa）和四跨膜蛋白CD9是血小板膜中丰富的整合膜蛋白。我们已经鉴定出几种蛋白质，包括CD9，它们在用聚（氧乙烯）非离子去污剂Brij-35溶解的未处理的静息血小板中，能被抗αIIbβ3抗体共沉淀。免疫印迹和定量免疫沉淀表明，αIIbβ3与CD9的结合是特异性的且呈化学计量关系。CD9与αIIbβ3之间的相互作用可能是疏水的，因为Triton X-100和Brij系列的疏水去污剂能完全解离CD9-αIIbβ3复合物。通过共免疫沉淀以及在铺展细胞周边和铺在纤维蛋白原上的细胞的片状伪足中的共定位可以看出，重组CD9和αIIbβ3转染到中国仓鼠卵巢细胞后可以相互结合。这种共定位在粘着斑中不存在。此外，抗CD9包被的乳胶珠使αIIbβ3与CD9聚集在一起。这项工作表明，四跨膜蛋白CD9在静息血小板和转染细胞中与β3整合素相关联。
