Negative Signaling in B Cells

Science's STKE  25 Jan 2000:
Vol. 2000, Issue 16, pp. tw4
DOI: 10.1126/stke.2000.16.tw4

The proteins p62dok and insulin receptor substrate-1 (IRS-1) are structurally very similar, yet, while IRS-1 is involved in stimulating cell proliferation, Yamanashi et al. report that p62dok appears to inhibit proliferation, at least in B cells. When the B-cell receptor (BCR) is stimulated by antigen or is cross-linked, B cells proliferate and secrete antibody. However, when secreted antibody, bound to antigen, induces cross-linking between the BCR and the immunoglobulin receptor FcγRIIB, these responses are inhibited. The authors report that B cells from mice lacking p62dok did not exhibit normal inhibition of cell proliferation in response to BCR/FcγRIIB cross-linking, suggesting a critical role for p62dok in this feedback inhibition pathway. B cells from p62dok-null mice exhibited higher MAP kinase activation than normal B cells upon BCR/FcγRIIB cross-linking, though it is not clear how p62dok might suppress MAP kinase. In normal B cells, p62dok was also tyrosine-phosphorylated upon BCR/FcγRIIB cross-linking, and this appears to involve the tyrosine kinase Lyn.

Yamanashi, Y., Tamura, T., Kanamori, T., Yamane, H., Nariuchi, H., Yamamoto, T., and Baltimore, D. (2000) Role of the rasGAP-associated docking protein p62dok in negative regulation of B cell receptor-mediated signaling. Genes Dev. 14:11-16. [Abstract] [Full Text]