Functional interaction of RasGAP-binding proteins Dok-1 and Dok-2 with the Tec protein tyrosine kinase.

The Dok adaptor family of proteins binding to RasGAP, consisting of Dok-1 and Dok-2, are critical regulators in cell proliferation. These molecules are partners and/or substrates of different protein tyrosine kinases considered as oncoproteins. Here, we show that Dok-1 and Dok-2 are the major tyrosine-phosphorylated proteins associated to Tec, a protein tyrosine kinase expressed in T cells. Furthermore, we evaluate the effect of Dok-1 or Dok-2 on Tec-mediated signalling pathways in T cells. Here, we provide evidence that Dok-1 and Dok-2 proteins are involved in a negative feedback regulation of Tec via a downregulation of its tyrosine phosphorylation and downstream signalling pathways including the Ras pathway. Either Dok-1 or Dok-2 therefore represents a mean of potent retrograde control for protein tyrosine kinase signalling, and then possibly of tumor development.