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Mol. Cell. Biol., Aug 1997, 4305-4311, Vol 17, No. 8
S Tridandapani, T Kelley, M Pradhan, D Cooney, LB Justement and KM Coggeshall
Recently, we and others have demonstrated that negative signaling in B
cells selectively induces the tyrosine phosphorylation of a novel inositol
polyphosphate phosphatase, p145SHIP. In this study, we present data
indicating that p145SHIP binds directly a phosphorylated motif,
immunoreceptor tyrosine-based inhibition motif (ITIM), present in the
cytoplasmic domain of Fc gammaRIIB1. Using recombinant SH2 domains, we show
that binding is mediated via the Src homology region 2 (SH2)- containing
inositol phosphatase (SHIP) SH2 domain. SHIP also bound to a phosphopeptide
derived from CD22, raising the possibility that SHIP contributes to
negative signaling by this receptor as well as Fc gammaRIIB1. The
association of SHIP with the ITIM phosphopeptide was activation
independent, while coassociation with Shc was activation dependent.
Furthermore, experiments with Fc gammaRIIB1-deficient B cells demonstrated
a genetic requirement for expression of Fc gammaRIIB1 in the induction of
SHIP phosphorylation and its interaction with Shc. Based on these results,
we propose a model of negative signaling in which co-cross-linking of
surface immunoglobulin and Fc gammaRIIB1 results in sequential tyrosine
phosphorylation of the ITIM, recruitment and phosphorylation of p145SHIP,
and subsequent binding of Shc.
Copyright © 1997, American Society for Microbiology
Recruitment and phosphorylation of SH2-containing inositol phosphatase and Shc to the B-cell Fc gamma immunoreceptor tyrosine-based inhibition motif peptide motif
Department of Microbiology, Ohio State University, Columbus 43210, USA.
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