Li W, Hu P, Skolnik E Y, Ullrich A, Schlessinger J
Department of Pharmacology, New York University Medical Center, New York 10016.
Mol Cell Biol. 1992 Dec;12(12):5824-33. doi: 10.1128/mcb.12.12.5824-5833.1992.
Signalling proteins such as phospholipase C-gamma (PLC-gamma) or GTPase-activating protein (GAP) of ras contain conserved regions of approximately 100 amino acids termed src homology 2 (SH2) domains. SH2 domains were shown to be responsible for mediating association between signalling proteins and tyrosine-phosphorylated proteins, including growth factor receptors. Nck is an ubiquitously expressed protein consisting exclusively of one SH2 and three SH3 domains. Here we show that epidermal growth factor or platelet-derived growth factor stimulation of intact human or murine cells leads to phosphorylation of Nck protein on tyrosine, serine, and threonine residues. Similar stimulation of Nck phosphorylation was detected upon activation of rat basophilic leukemia RBL-2H3 cells by cross-linking of the high-affinity immunoglobulin E receptors (Fc epsilon RI). Ligand-activated, tyrosine-autophosphorylated platelet-derived growth factor or epidermal growth factor receptors were coimmunoprecipitated with anti-Nck antibodies, and the association with either receptor molecule was mediated by the SH2 domain of Nck. Addition of phorbol ester was also able to stimulate Nck phosphorylation on serine residues. However, growth factor-induced serine/threonine phosphorylation of Nck was not mediated by protein kinase C. Interestingly, approximately fivefold overexpression of Nck in NIH 3T3 cells resulted in formation of oncogenic foci. These results show that Nck is an oncogenic protein and a common target for the action of different surface receptors. Nck probably functions as an adaptor protein which links surface receptors with tyrosine kinase activity to downstream signalling pathways involved in the control of cell proliferation.
信号蛋白，如磷脂酶C-γ（PLC-γ）或ras的GTP酶激活蛋白（GAP），含有约100个氨基酸的保守区域，称为src同源2（SH2）结构域。SH2结构域被证明负责介导信号蛋白与酪氨酸磷酸化蛋白之间的结合，包括生长因子受体。Nck是一种普遍表达的蛋白，仅由一个SH2结构域和三个SH3结构域组成。在这里，我们表明，表皮生长因子或血小板衍生生长因子对完整的人或鼠细胞的刺激会导致Nck蛋白在酪氨酸、丝氨酸和苏氨酸残基上磷酸化。通过高亲和力免疫球蛋白E受体（FcεRI）交联激活大鼠嗜碱性白血病RBL-2H3细胞后，检测到类似的Nck磷酸化刺激。配体激活的、酪氨酸自磷酸化的血小板衍生生长因子或表皮生长因子受体与抗Nck抗体共免疫沉淀，与任一受体分子的结合由Nck的SH2结构域介导。佛波酯的添加也能够刺激Nck在丝氨酸残基上的磷酸化。然而，生长因子诱导的Nck丝氨酸/苏氨酸磷酸化不是由蛋白激酶C介导的。有趣的是，Nck在NIH 3T3细胞中约五倍的过表达导致了致癌灶的形成。这些结果表明，Nck是一种致癌蛋白，是不同表面受体作用的共同靶点。Nck可能作为一种衔接蛋白，将具有酪氨酸激酶活性的表面受体与参与细胞增殖控制的下游信号通路联系起来。
