Membrane IgM-induced tyrosine phosphorylation of CD19 requires a CD19 domain that mediates association with components of the B cell antigen receptor complex.

摘要: CD19 enhances membrane IgM (mIgM) signaling and is required for B lymphocyte responses to T-dependent Ags. tyrosine phosphorylated when mIgM ligated binds SH2 domain-containing proteins. We suggest that the basis phosphorylation association of with Syk other components complex. IgM, CD22, Ig-alpha, Ig-beta, were coimmunoprecipitated from detergent lysates lymphocytes. The was maintained a chimeric form containing only transmembrane domain proximal 17 amino acids cytoplasmic encoded by exon 6. This sequence sufficient mediate association, as synthetic peptide 6-encoded region adsorbs Syk. Deletion juxtamembrane 6 abolishes these acids, which contain no tyrosines, also reduces mIgM-induced remainder domain. Coligating this mutant restores phosphorylation. Thus, discrete regulates in activation cells mIgM.