Eriksson A, Nånberg E, Rönnstrand L, Engström U, Hellman U, Rupp E, Carpenter G, Heldin C H, Claesson-Welsh L
Ludwig Institute for Cancer Research, Uppsala, Sweden.
J Biol Chem. 1995 Mar 31;270(13):7773-81. doi: 10.1074/jbc.270.13.7773.
Phosphorylated tyrosine residues in receptor tyrosine kinases serve as binding sites for signal transduction molecules. We have identified two autophosphorylation sites, Tyr-988 and Tyr-1018, in the platelet-derived growth factor (PDGF) alpha-receptor carboxyl-terminal tail, which are involved in binding of phospholipase C-gamma (PLC-gamma). The capacities of the Y988F and Y1018F mutant PDGF alpha-receptors, expressed in porcine aortic endothelial cells, to bind PLC-gamma are 60 and 5% of that of the wild-type receptor, respectively. Phosphorylated but not unphosphorylated peptides containing Tyr-1018 are able to compete with the intact receptor for binding to immobilized PLC-gamma SH2 domains; a phosphorylated Tyr-988 peptide competes 10 times less efficiently. The complex between PLC-gamma and the PDGF alpha-receptor is more stable than that of PLC-gamma and the PDGF beta-receptor. However, PDGF stimulation results in a smaller fraction of tyrosine-phosphorylated PLC-gamma and a smaller accumulation of inositol trisphosphate in cells expressing the alpha-receptor as compared with cells expressing the beta-receptor. We conclude that phosphorylated Tyr-988 and Tyr-1018 in the PDGF alpha-receptor carboxyl-terminal tail bind PLC-gamma, but this association leads to only a relatively low level of tyrosine phosphorylation and activation of PLC-gamma.
受体酪氨酸激酶中的磷酸化酪氨酸残基作为信号转导分子的结合位点。我们在血小板衍生生长因子（PDGF）α受体的羧基末端尾部鉴定出两个自磷酸化位点，即Tyr-988和Tyr-1018，它们参与磷脂酶C-γ（PLC-γ）的结合。在猪主动脉内皮细胞中表达的Y988F和Y1018F突变型PDGFα受体结合PLC-γ的能力分别为野生型受体的60%和5%。含有Tyr-1018的磷酸化但非未磷酸化的肽能够与完整受体竞争结合固定化的PLC-γ SH2结构域；磷酸化的Tyr-988肽的竞争效率低10倍。PLC-γ与PDGFα受体之间的复合物比PLC-γ与PDGFβ受体之间的复合物更稳定。然而，与表达β受体的细胞相比，PDGF刺激导致表达α受体的细胞中酪氨酸磷酸化的PLC-γ比例较小，肌醇三磷酸的积累也较少。我们得出结论，PDGFα受体羧基末端尾部的磷酸化Tyr-988和Tyr-1018结合PLC-γ，但这种结合仅导致相对较低水平的酪氨酸磷酸化和PLC-γ的激活。
