Molecular cloning of the mouse APS as a member of the LnK family adaptor proteins

Engagement of cell-surface receptors leads to activation of protein tyrosin e kinases, which in turn phosphorylate various downstream enzymes and adapt or proteins. Lnk is an adaptor protein that appears to be involved in signa l transduction in lymphocytes, and forms an adaptor protein family with SH2 -B. We tried to identify another member of the adaptor protein family and i solated the mouse APS (adaptor molecule containing PH and SH2 domains). APS contains a proline-rich region, PH and SH2 domains, and a putative tyrosin e phosphorylation site at the C-terminal, and the overall structure resembl es those of Lnk and SH2-B. APS is expressed in brain, kidney, muscle, and m ature B cells in spleen. Mouse APS gene consists of 8 coding exons and is d educed to map to chromosome 5. APS is tyrosine phosphorylated at the C-term inal phosphorylation site conserved among the Lnk family adaptor proteins b y stimulation of IL-5 or IL-3 as well as by crosslinking of B cell receptor complex. These results suggest that APS is a member of the Lnk family adap tor protein and likely plays a role in signaling in B cells. (C) 2000 Acade mic Press.