Twamley-Stein G M, Pepperkok R, Ansorge W, Courtneidge S A
European Molecular Biology Laboratory, Heidelberg, Germany.
Proc Natl Acad Sci U S A. 1993 Aug 15;90(16):7696-700. doi: 10.1073/pnas.90.16.7696.
Three members of the Src family of protein tyrosine kinases Src, Fyn, and Yes associate with the activated platelet-derived growth factor (PDGF) receptor in vivo. This interaction requires the Src homology 2 (SH2) domain of the Src family member and causes activation of the intrinsic activity of the Src family kinases. We microinjected cells with DNA encoding catalytically inactive forms of the Src and Fyn proteins and examined their effects on PDGF-mediated signaling in vivo. Kinase-inactive Src and Fyn inhibited PDGF-stimulated entry of cells into S phase, whereas kinase-active forms of the proteins had no inhibitory effects. An intact SH2 domain was required for inhibition. Furthermore, when kinase-inactive Fyn was comicroinjected with a plasmid expressing activated Ras, the cells could enter S phase, indicating that the expression of kinase-inactive Fyn did not damage cell viability. Injection of an antibody specific for Src, Fyn, and Yes also reduced signal transduction through the PDGF receptor but only when injected within 8 hr of PDGF stimulation. Together these results indicate that the ubiquitously expressed Src family members are required for PDGF-induced mitogenic signaling.
蛋白酪氨酸激酶Src家族的三个成员Src、Fyn和Yes在体内与活化的血小板衍生生长因子（PDGF）受体相关联。这种相互作用需要Src家族成员的Src同源2（SH2）结构域，并导致Src家族激酶的内在活性激活。我们向细胞中显微注射编码Src和Fyn蛋白催化失活形式的DNA，并在体内研究它们对PDGF介导的信号传导的影响。激酶失活的Src和Fyn抑制PDGF刺激的细胞进入S期，而蛋白的激酶活性形式则没有抑制作用。抑制作用需要完整的SH2结构域。此外，当激酶失活的Fyn与表达活化Ras的质粒共同显微注射时，细胞可以进入S期，这表明激酶失活的Fyn的表达不会损害细胞活力。注射针对Src、Fyn和Yes的特异性抗体也会降低通过PDGF受体的信号转导，但仅在PDGF刺激后8小时内注射时才会如此。这些结果共同表明，普遍表达的Src家族成员是PDGF诱导的有丝分裂信号传导所必需的。
