title: Protein interactions of Src homology 2 (SH2) domain-containing inositol phosphatase (SHIP): association with Shc displaces SHIP from FcgammaRIIb in B cells.
abstract: Our recent studies revealed that the inositol phosphatase Src homology 2 (SH2) domain-containing inositol phosphatase (SHIP) is phosphorylated and associated with Shc exclusively under negative signaling conditions in B cells, which is due to recruitment of the SHIP SH2 domain to the FcgammaRIIb. In addition, we reported that SHIP-Shc interaction involves both SHIP SH2 and Shc phosphotyrosine binding domains. These findings reveal a paradox in which the single SH2 domain of SHIP is simultaneously engaged to two different proteins: Shc and FcgammaRIIb. To resolve this paradox, we examined the protein interactions of SHIP. Our results demonstrated that isolated FcgammaRIIb contains SHIP but not Shc; likewise, Shc isolates contain SHIP but not FcgammaRIIb. In contrast, SHIP isolates contain both proteins, revealing two separate pools of SHIP: one bound to FcgammaRIIb and one bound to Shc. Kinetic studies reveal rapid SHIP association with FcgammaRIIb but slower and more transient association with Shc. Affinity measurements using a recombinant SHIP SH2 domain and phosphopeptides derived from FcgammaRIIb (corresponding to Y273) and Shc (corresponding to Y317) revealed an approximately equal rate of binding but a 10-fold faster dissociation rate for FcgammaRIIb compared with Shc phosphopeptide and yielding in an affinity of 2.1 microM for FcgammaRIIb and 0.26 microM for Shc. These findings are consistent with a model in which SHIP transiently associates with FcgammaRIIb to promote SHIP phosphorylation, whereupon SHIP binds to Shc and dissociates from FcgammaRIIb.
authors.affiliation: Department of Microbiology, Ohio State University, OH 43210, USA.
authors.forename: S
authors.initials: S
authors.lastname: Tridandapani
authors.forename: M
authors.initials: M
authors.lastname: Pradhan
authors.forename: J R
authors.initials: JR
authors.lastname: LaDine
authors.forename: S
authors.initials: S
authors.lastname: Garber
authors.forename: C L
authors.initials: CL
authors.lastname: Anderson
authors.forename: K M
authors.initials: KM
authors.lastname: Coggeshall
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008954:Models, Biological; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D017452:Receptors, IgG / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D018909:src Homology Domains