DELETION OF SRC HOMOLOGY-3 DOMAIN RESULTS IN CONSTITUTIVE ACTIVATION OF TEC PROTEIN-TYROSINE KINASE

Tec protein-tyrosine kinase (PTK) is the prototype of a new subfamily of non-receptor type PTKs, and is abundantly expressed in hematopoieti c tissues. We have revealed that Tec is inducibly tyrosine-phosphoryla ted and activated by stimulation with a wide range of cytokines. To ge t more insight into the signaling mechanism through Tee, we have gener ated a constitutively active form of Tec PTK. Deletion of the Src homo logy (SH) 3 domain gave rise to a hyperphosphorylated and activated Te c kinase (Tec Delta SH3). The activity of Tec Delta SH3 was confirmed in 293 cells, as well as in cytokine-dependent hematopoietic cells (BA /F3). Tec Delta SH3 should be a useful tool to study the in vivo subst rates of Tec PTK.