Syk is a dual-specificity kinase that self-regulates the signal output from the B-cell antigen receptor
26.10.2010
Heizmann B, Reth M, Infantino S
PNAS 107; Pages: 18563–18568
Upon B-cell activation, the signaling subunits Ig-? and Ig-? of the B-cell antigen receptor become phosphorylated not only on tyrosines but also on serine residues. Using a specific antibody, we
show that serine 197 (S197) in the cytoplasmic tail of Ig-? is phosphorylated upon B-cell antigen receptor activation, and that this modification inhibits the signal output of the B-cell antigen
receptor. Surprisingly, we found that the well-known protein tyrosine kinase Syk (spleen tyrosine kinase) phosphorylates S197 on Ig-?, thus not only activating but also inhibiting signaling from
the B-cell antigen receptor. This finding identifies Syk as a dual-specificity kinase and establishes a previously unexplored paradigm for the self-regulation of biological signaling processes.
