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The shc oncogene product is tyrosine-phosphorylated by Src family kinases and after its phosphorylation interacts with the adapter protein Grb2 (growth factor receptor-bound protein 2). In turn, Grb2 interacts with the guanine nucleotide exchange factor for Ras, mSOS. Because several Src family kinases participate in T cell activation and Shc functions upstream of Ras, the role of Shc in T cell signaling was examined. Shc was phosphorylated on tyrosine after activation through the T cell receptor (TCR), and subsequently interacted with Grb2 and mSOS. The Src homology region 2 (SH2) domain of Shc directly interacted with the tyrosine-phosphorylated ζ chain of the TCR. Thus, Shc may couple TCR activation to the Ras signaling pathway.