Regulation of ITAM signaling by specific sequences in Ig-β B cell antigen receptor subunit

Sylvanie Cassard, Daniel Choquet, Wolf Herman Fridman, Christian Bonnerot
J. Biol. Chem.. 1996-09-27; 271(39): 23786-23791
DOI: 10.1074/jbc.271.39.23786

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1. J Biol Chem. 1996 Sep 27;271(39):23786-91.

Regulation of ITAM signaling by specific sequences in Ig-beta B cell antigen
receptor subunit.

Cassard S(1), Choquet D, Fridman WH, Bonnerot C.

Author information:
(1)CJF 95-01, INSERM, Institut Curie, 75231 Paris cedex 05, France.

B cell antigen receptors (BCR) are composed of an antigen binding subunit, the
membrane Ig, and Ig-alpha/Ig-beta heterodimers, that contain a transducing motif
named ITAM for « immuno-receptor tyrosine-based activation motif. » Ig-alpha and
Ig-beta ITAMs only differ by four amino acids located before the second conserved
tyrosine (DCSM in Ig-alpha and QTAT in Ig-beta), which determine the in vitro
association of Ig-alpha with the src kinase fyn. We have previously shown that
Ig-alpha and Ig-beta BCR subunits activate different signaling pathways by
expressing, in B cells, FcgammaRII chimeras containing the cytoplasmic tails of
Ig-alpha or Ig-beta. We report here that the signaling capacity of Ig-beta ITAM
is regulated by peptide sequences located inside (QTAT region) or outside the
ITAM (flanking sequences). Furthermore, when isolated, Ig-alpha and Ig-beta ITAM
have similar abilities as the entire Ig-alpha tail and the whole BCR in
triggering tyrosine kinase activation, an increase of intracellular calcium
concentration as well as late events of cell activation as assessed by cytokine
secretion. These data show that alterations that modify the ability of Ig-alpha
and Ig-beta to interact in vitro with the src kinase fyn (switch between QTAT and
DCSM) also determine signal transduction capabilities of these molecules
expressed in B cells.

DOI: 10.1074/jbc.271.39.23786
PMID: 8798606 [Indexed for MEDLINE]

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