Mediation by the Protein-tyrosine Kinase Tec of Signaling between the B Cell Antigen Receptor and Dok-1

• Published in: The Journal of biological chemistry Vol. 275; no. 32; pp. 24945 - 24952
• Main Authors: Yoshida, Koji, Yamashita, Yoshihiro, Miyazato, Akira, Ohya, Ken-ichi, Kitanaka, Akira, Ikeda, Uichi, Shimada, Kazuyuki, Yamanaka, Takeo, Ozawa, Keiya, Mano, Hiroyuki
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 11.08.2000; American Society for Biochemistry and Molecular Biology
• Subjects: B-Lymphocytes; Burkitt Lymphoma; Cell Line; DNA-Binding Proteins - metabolism; Dok1 protein; Humans; Nerve Tissue Proteins; Nuclear Proteins - metabolism; Phosphoproteins - metabolism; Phosphorylation; ras GTPase-Activating Proteins - metabolism; Receptors, Antigen, B-Cell - physiology; Receptors, Steroid; Receptors, Thyroid Hormone; Recombinant Fusion Proteins - metabolism; RNA-Binding Proteins; Signal Transduction; src Homology Domains; Tec protein; Transfection; Tumor Cells, Cultured; Zinc Fingers
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M909012199

A variety of growth factor receptors induce the tyrosine phosphorylation of a nonreceptor protein-tyrosine kinase Tec as well as that of a Tec-binding protein of 62 kDa. Given the similarity in properties between this 62-kDa protein and p62Dok-1, the possibility that these two proteins are identical was investigated. Overexpression of a constitutively active form of Tec in a pro-B cell line induced the hyperphosphorylation of endogenous Dok-1. Tec also associated with Dok-1 in a phosphorylation-dependent manner in 293 cells. Tec mediated marked phosphorylation of Dok-1 both in vivo and in vitro, and this effect required both the Tec homology and Src homology 2 domains of Tec in addition to its kinase activity. Expression of Dok-1 in 293 cells induced inhibition of Ras activity, suggesting that Dok-1 is a negative regulator of Ras. In the immature B cell line Ramos, cross-linking of the B cell antigen receptor (BCR) resulted in tyrosine phosphorylation of Dok-1, and this effect was markedly inhibited by expression of dominant negative mutants of Tec. Furthermore, overexpression of Dok-1 inhibited activation of the c-fos promoter induced by stimulation of the BCR. These results suggest that Tec is an important mediator of signaling from the BCR to Dok-1.