The transmembrane domain of glycoprotein Ibβ is critical to efficient expression of glycoprotein Ib-IX complex in the plasma membrane
The transmembrane domain of glycoprotein Ibβ is critical to efficient expression of glycoprotein Ib-IX complex in the plasma membrane
复制标题
DOI：
10.1074/jbc.m600924200
复制
发表时间：
2006-08-11
影响因子：
4.8
通讯作者：
Li, Renhao
中科院分区：
文献类型：
--
作者：
Mo, Xi;Lu, Nan;Li, Renhao
血小板中糖蛋白（GP）Ib-IX-V复合物表达的缺乏通常是由其三个亚基（GP Ib α、GP Ib β或GP IX）突变引起的。在受体复合物的有效表面表达中所有三个亚基的要求已在中国仓鼠卵巢细胞中再现。在这里，我们探讨了跨膜结构域在GP Ib-IX复合物表达中的作用以及这些结构域之间的潜在相互作用。用不相关的序列替换GP Ib β或GP Ib β的跨膜结构域，而不是GP IX的跨膜结构域，显著降低了瞬时转染的中国仓鼠卵巢细胞中GP Ib-IX复合物的表面表达。Ib β跨膜结构域的替换产生最大的影响。此外，发现Ib β跨膜结构域中的几个单位点突变显著降低GPIb的总体表达以及表面表达，这可能是通过干扰Ib α和Ib β跨膜结构域之间的相互作用，进而降低GP Ib α在细胞中的稳定性。Ib α跨膜结构域中的突变S503 V和S503 L部分逆转了Ib β跨膜结构域中突变H139 L的表达降低效应，但不逆转其他突变，表明这两个极性残基之间存在特异性相互作用。总之，我们的结果已经证明了Ib β跨膜结构域的重要性，通过其与Ib α对应物的相互作用，GP Ib-IX复合物的正确组装和有效的表面表达。
Lack of expression of glycoprotein (GP) Ib-IX-V complex in platelets often results from mutations in its three subunits: GP Ib alpha, GP Ib beta, or GP IX. The requirement of all three subunits in the efficient surface expression of the receptor complex has been reproduced in Chinese hamster ovary cells. Here, we probed the role of the transmembrane domains in expression of the GP Ib-IX complex and potential interactions between these domains. Replacing the transmembrane domains of either GP Ib beta or GP Ib beta, but not that of GP IX, with unrelated sequences markedly diminished surface expression of the GP Ib-IX complex in transiently transfected Chinese hamster ovary cells. Replacement of the Ib beta transmembrane domain produced the largest effect. Furthermore, several single-site mutations in the Ib beta transmembrane domain were found to significantly decrease overall expression as well as surface expression of GPIb , probably by perturbing the interaction between the Ib alpha and Ib beta transmembrane domains and in turn reducing the stability of GP Ib alpha in the cell. Mutations S503V and S503L in the Ib alpha transmembrane domain partly reversed the expression-decreasing effect of mutation H139L, but not the others, in the Ib beta transmembrane domain, suggesting a specific interaction between these two polar residues. Together, our results have demonstrated the importance of the Ib beta transmembrane domain, through its interaction with the Ib alpha counterpart, to the proper assembly and efficient surface expression of the GP Ib-IX complex.