Sieh M, Bolen J B, Weiss A
Howard Hughes Medical Institute, Department of Medicine, University of California, San Francisco 94143.
EMBO J. 1993 Jan;12(1):315-21. doi: 10.1002/j.1460-2075.1993.tb05659.x.
CD45 is a tyrosine phosphatase expressed in all hematopoietic cells which is important for signal transduction through the T cell antigen receptor (TCR). Studies using CD45-deficient cells have revealed that Lck, a tyrosine kinase thought to be essential for TCR signaling, is hyperphosphorylated on Y505 in the absence of CD45. This site of tyrosine phosphorylation negatively regulates the function of the Src family of kinases. Here we provide evidence that CD45 can modulate the binding of the Lck to an 11 amino acid tyrosine phosphorylated peptide containing the carboxy-terminus of Lck (lckP). Significantly, CD45 did not influence the binding of Fyn, PLC gamma 1, GAP and Vav to the same phosphopeptide. Lck protein which bound the peptide was dephosphorylated on Y505 and consisted of only 5-10% of the total cellular Lck. Interestingly, there was a marked increase in binding 15-30 min after CD4 or TCR cross-linking. Taken together, our data suggest that CD45 specifically modulates the conformation of Lck in a manner consistent with the intramolecular model of regulation of Src-like kinases.
CD45是一种在所有造血细胞中表达的酪氨酸磷酸酶，它对于通过T细胞抗原受体（TCR）进行信号转导很重要。使用CD45缺陷细胞的研究表明，Lck（一种被认为对TCR信号传导至关重要的酪氨酸激酶）在没有CD45的情况下，其Y505位点会发生过度磷酸化。酪氨酸磷酸化的这个位点会负向调节Src激酶家族的功能。在此，我们提供证据表明，CD45可以调节Lck与一个包含Lck羧基末端的11个氨基酸的酪氨酸磷酸化肽段（lckP）的结合。值得注意的是，CD45不影响Fyn、PLCγ1、GAP和Vav与同一磷酸肽的结合。与该肽段结合的Lck蛋白在Y505位点发生去磷酸化，且仅占细胞总Lck的5 - 10%。有趣的是，在CD4或TCR交联后15 - 30分钟，结合明显增加。综上所述，我们的数据表明，CD45以与Src样激酶调节的分子内模型一致的方式特异性地调节Lck的构象。
