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Dual role of the tyrosine activation motif of the Ig‐alpha protein during signal transduction via the B cell antigen receptor.
Author(s) -
Flaswinkel H.,
Reth M.
Publication year - 1994
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1994.tb06237.x
Subject(s) - biology , microbiology and biotechnology , b cell receptor , signal transduction , b cell , antibody , genetics
The B cell antigen receptor (BCR) is a multimeric protein complex consisting of the ligand binding immunoglobulin molecule and the Ig‐alpha/beta heterodimer that mediates intracellular signalling by coupling the receptor to protein tyrosine kinases (PTKs). Transfection of the Ig‐alpha deficient myeloma cell line J558L microns with expression vectors coding for mutated Ig‐alpha allowed us to test the function of the tyrosines in the cytoplasmic region of Ig‐alpha in the context of the BCR. Furthermore we expressed Ig‐alpha mutations as chimeric CD8‐Ig‐alpha molecules on K46 B lymphoma cells and tested their signalling capacity in terms of PTK activation and release of calcium. We show here that the conserved tyrosine residues in the cytoplasmic portion of Ig‐alpha have a dual role. First, they are required for efficient activation of PTKs during signal induction and second, one of them is subject to phosphorylation by activated src‐related PTKs. Phosphorylation on tyrosine in the cytoplasmic portion of Ig‐alpha is discussed as a possible mechanism to couple the BCR to SH2 domain‐carrying molecules.