CD40 ligation results in protein kinase C-independent activation of ERK and JNK in resting murine splenic B cells.
CD40 is a 45- to 50-kDa transmembrane glycoprotein that plays an important role in B cell proliferation, survival, memory, and Ig isotype switching. How CD40 engagement couples to these distal events in B cell activation remains poorly understood. In this study, we have examined signal transduction events mediated by CD40 cross-linking in resting murine splenic B cells. In comparison to signaling via the B cell Ag receptor (BCR), CD40 cross-linking was less effective at activating protein tyrosine kinases. Interestingly, however, CD40 engagement resulted in the phosphorylation of both extracellular signal-regulated protein kinase ( ERK) and the Ras guanine nucleotide exchange factor, Son of sevenless. In addition, both ERK and c-Jun NH2-terminal kinase activities were increased after both CD40 and BCR ligation. Overnight treatment of cells with phorbol ester as well as pharmacologic inhibitors of protein kinase C abrogated these signaling events after BCR treatment; however, no effect was seen on CD40-mediated activation of ERK or c-Jun NH2-terminal kinase, suggesting that the BCR and CD40 differentially utilize protein kinase C to couple with these signaling pathways.[1]References
- CD40 ligation results in protein kinase C-independent activation of ERK and JNK in resting murine splenic B cells. Li, Y.Y., Baccam, M., Waters, S.B., Pessin, J.E., Bishop, G.A., Koretzky, G.A. J. Immunol. (1996) [Pubmed]
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