The B cell receptor promotes B cell activation and proliferation through a non-ITAM tyrosine in the Igalpha cytoplasmic domain.
In addition to the tyrosines of the Igalpha and beta immunoreceptor tyrosine-based activation motifs (ITAMs), the evolutionarily conserved Igalpha non-ITAM tyrosine 204 becomes phosphorylated upon antigen recognition by the B cell receptor (BCR). Here we demonstrate that splenic B cells from mice with a targeted mutation of Igalpha Y204 exhibited an isolated defect in T cell-independent B cell activation, proliferation, and antibody response upon BCR engagement, yet normal BCR capping, antigen internalization, antigen presentation, and T cell-dependent antibody production. Mutant B cells, present in normal numbers, exhibited unimpaired BCR-induced spleen tyrosine kinase (Syk) phosphorylation but reduced B cell linker protein (BLNK) phosphorylation, calcium flux, and nuclear factor kappaB (NFkappaB), c-jun N-terminal kinase (JNK), and extracellular signal-regulated kinase ( ERK) activation. These results suggest that Igalpha non-ITAM tyrosine 204 promotes a distinct cellular response, namely T-independent B cell proliferation and differentiation via phosphorylation of the adaptor BLNK.[1]References
- The B cell receptor promotes B cell activation and proliferation through a non-ITAM tyrosine in the Igalpha cytoplasmic domain. Patterson, H.C., Kraus, M., Kim, Y.M., Ploegh, H., Rajewsky, K. Immunity (2006) [Pubmed]
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