Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.
Microbiol Immunol. 2009 Nov;53(11):629-35. doi: 10.1111/j.1348-0421.2009.00167.x.
Efficient downregulation of CXCR4 cell surface expression by introduction of the CD63 gene has previously been reported by us. In the present study, it was found that CD63 and its mutant efficiently interact with CXCR4 in live cells and that CD63-induced downregulation and interaction are significantly abrogated by the N-linked glycosylation inhibitor, TM. Furthermore, the downregulation and interaction were clearly attenuated by alternation of all three N-linked glycosylation sites in CD63. Either CD63 or CD63DeltaN formed a complex with CXCR4 at the Golgi apparatus and the late endosomes, while CD63 GD mutants lost the ability to form a complex with CXCR4 exclusively at the Golgi apparatus. These findings suggest that CD63 interacts with CXCR4 through the N-linked glycans-portion of the CD63 protein and that the complex induces direction of CXCR4 trafficking to the endosomes/lysosomes, rather than to the plasma membrane. At the Golgi apparatus, there may be lysosome protein (CD63)-associated machinery that influences trafficking of other membrane proteins.
我们之前曾报道过，通过引入 CD63 基因可以有效地下调 CXCR4 的细胞表面表达。在本研究中，我们发现 CD63 及其突变体能在活细胞中与 CXCR4 有效相互作用，而 N-连接糖基化抑制剂 TM 显著阻断了 CD63 诱导的下调和相互作用。此外，CD63 中三个 N-连接糖基化位点的改变明显减弱了下调和相互作用。CD63 或 CD63DeltaN 在高尔基体和晚期内体与 CXCR4 形成复合物，而 CD63 GD 突变体完全丧失了在高尔基体与 CXCR4 形成复合物的能力。这些发现表明，CD63 通过 CD63 蛋白的 N-连接糖基部分与 CXCR4 相互作用，并且该复合物诱导 CXCR4 向内体/溶酶体的运输方向，而不是向质膜。在高尔基体上，可能存在影响其他膜蛋白运输的溶酶体蛋白（CD63）相关机制。
