Signaling through the B cell antigen receptor (BCR) results in rapid increases in tyrosine phosphorylation on a number of proteins. The BCR associates with two classes of tyrosine kinase: Src-family kinase (Src-protein-tyrosine kinase [PTK]; Lyn, Fyn, Blk, or Lck) and Syk kinase. We have investigated the interaction between the Src-PTK and the Syk kinase in the BCR signaling. In contrast to wild-type B cells, BCR-mediated tyrosine phosphorylation of Syk and activation of its in vitro kinase activity were profoundly reduced in lyn-negative cells. The requirement of the Src-PTK to induce tyrosine phosphorylation and activation of Syk was also demonstrated by cotransfection of syk and src-PTK cDNAs into COS cells. These results suggest that the Src-PTK associated with BCR phosphorylates the tyrosine residue(s) of Syk upon receptor stimulation, enhancing the activity of Syk.
Syk activation by the Src-family tyrosine kinase in the B cell receptor signaling.
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T Kurosaki, M Takata, Y Yamanashi, T Inazu, T Taniguchi, T Yamamoto, H Yamamura; Syk activation by the Src-family tyrosine kinase in the B cell receptor signaling.. J Exp Med 1 May 1994; 179 (5): 1725–1729. doi: https://doi.org/10.1084/jem.179.5.1725
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