整合蛋白β3近膜端α螺旋中的E726Q突变影响细胞膜与肌动蛋白皮质层相互作用继而诱导细胞膜形成突起小泡

A Single E726Q Mutation in the Membrane Proximal α-Helix of Integrin β3 Subunit Induces Membrane Blebbing by Disrupting the Membrane-Actin Cortex Interaction

整合蛋白β亚基胞浆段近膜端α螺旋在与诸多蛋白如踝蛋白(talin)、α-辅肌动蛋白(α-actinin)或者骨架蛋白(skelemin)等的结合上发挥着重要的功能。本研究的目的是通过对α螺旋上5个保守的带电荷氨基酸(R724,K725,E726,E731和E733)的研究,采用定点突变的方法,从而明确其在介导β3与骨架蛋白结合中的作用。实验结果表明,表达有突变型整合蛋白αⅡbβ3E726Q的CHO细胞株在固相化的纤维蛋白原上伸展不良,表型最显著。除此之外,E726Q突变可以诱导CHOαⅡbβ3E726Q细胞株在固相化的纤维蛋白原上的细胞膜起泡现象,且这种突起小泡(blebs)可以被肌凝蛋白轻链ATPase抑制剂blebbistatin所抑制。结论:整合蛋白β3亚基近膜端α螺旋在将细胞膜锚定到膜下肌动蛋白皮质层(submembraneous actin cortex)方面发挥重要作用。

The membrane proximal α helix of integrin β subunit cytoplasmic tails plays an important functional role by interacting with various intracellular proteins,namely talin,α-actinin or skelemin.This study was designed to investigate the functional role of 5 highly conserved charged amino acids（R^724,K^725,E^726,E^731,E^733） within this α helix by site-directed mutagenesis.The result showed that CHO cells expressing the αⅡbβ3E726Q mutant had the most prominent phenotype and characterized by defective cell spreading on immobilized fibrinogen.In addition,this E726Q mutation induced membrane blebbing in cells adherent on fibrinogen,and this blebbing could be inhibited by the myosin light chain ATPase inhibitor blebbistatin. It is concluded that the membrane proximal α-helix of integrin β3 subunit is important in linking the phospholipid membrane to the submembraneous actin cortex.