de Jong R, van Wijk A, Heisterkamp N, Groffen J
Department of Pathology, Childrens Hospital Los Angeles Research Institute and USC School of Medicine, California 90027, USA.
Oncogene. 1998 Nov 26;17(21):2805-10. doi: 10.1038/sj.onc.1202207.
The SH2-SH3 adaptor protein Crkl has been implicated in the signal transduction pathways of several membrane-bound receptors. Tyrosine phosphorylation of proteins associated with such signalling complexes can generate binding sites for the Crkl SH2-domain and can recruit proteins constitutively bound to Crkl via the Crkl SH3 domain into such complexes. In the current study we show that Crkl, but only a minor amount of the related Crk, form constitutive complexes in vivo with guanine nucleotide exchange factor C3G in 3T3 fibroblasts. Adhesion of both normal and transformed cells to fibronectin or other extracellular matrix proteins consistently induces the tyrosine-phosphorylation of C3G. Adhesion-induced tyrosine phosphorylation of C3G is dependent on an intact cytoskeleton and peaks at 5-10 min after attachment. In contrast, 3T3 cells stably transfected with Bcr/Abl P210 show a prominent reduction in the amount of C3G complexed to Crkl and do not exhibit tyrosine-phosphorylation of C3G upon spreading and attachment. These data establish that integrin-mediated cell adhesion results in Crkl-mediated tyrosine phosphorylation of C3G, a pathway which can be disrupted by Bcr/Abl.
SH2-SH3衔接蛋白Crkl参与了几种膜结合受体的信号转导途径。与此类信号复合物相关的蛋白质的酪氨酸磷酸化可生成Crkl SH2结构域的结合位点，并可通过Crkl SH3结构域将与Crkl组成性结合的蛋白质招募到此类复合物中。在本研究中，我们发现Crkl，但只有少量相关的Crk，在3T3成纤维细胞中与鸟嘌呤核苷酸交换因子C3G在体内形成组成性复合物。正常细胞和转化细胞与纤连蛋白或其他细胞外基质蛋白的粘附持续诱导C3G的酪氨酸磷酸化。粘附诱导的C3G酪氨酸磷酸化依赖于完整的细胞骨架，且在附着后5-10分钟达到峰值。相比之下，稳定转染Bcr/Abl P210的3T3细胞显示，与Crkl复合的C3G量显著减少，并且在铺展和附着时不表现出C3G的酪氨酸磷酸化。这些数据表明，整合素介导的细胞粘附导致Crkl介导的C3G酪氨酸磷酸化，这一途径可被Bcr/Abl破坏。
