Syk activation by the Src-family tyrosine kinase in the B cell receptor signaling.
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.
Kurosaki
T
T
Department of Cardiovascular Molecular Biology, Lederle Laboratories, Pearl River, New York 10965.
Takata
M
M
Yamanashi
Y
Y
Inazu
T
T
Taniguchi
T
T
Yamamoto
T
T
Yamamura
H
H
D000818:Animals; D002460:Cell Line; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src); D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D014162:Transfection
D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D011947:Receptors, Antigen, B-Cell; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D000072377:Syk Kinase