Effects of Src homology domain 2 (SH2)-containing inositol phosphatase (SHIP), SH2-containing phosphotyrosine phosphatase (SHP)-1, and SHP-2 SH2 decoy proteins on Fc gamma RIIB1-effector interactions and inhibitory functions.
Coaggregation of Fc gamma RIIB1 with B cell Ag receptors (BCR) leads to inhibition of BCR-mediated signaling via recruitment of Src homology domain 2 (SH2)-containing phosphatases. In vitro peptide binding experiments using phosphotyrosine-containing sequences derived from the immunoreceptor tyrosine-based inhibitory motif (ITIM) known to mediate Fc gamma RIIB1 effects suggest that the receptor uses SH2-containing inositol phosphatase (SHIP) and SH2-containing phosphotyrosine phosphatase (SHP)-1, as well as SHP-2 as effectors. In contrast, coimmunoprecipitation studies of receptor-effector associations suggest that the predominant Fc gamma RIIB1 effector protein is SHIP. However, biologically significant interactions may be lost in such studies if reactants' dissociation rates (Kd) are high. Thus, it is unclear to what extent these assays reflect the relative recruitment of SHIP, SHP-1, and SHP-2 to the receptor in vivo. As an alternative approach to this question, we have studied the effects of ectopically expressed SHIP, SHP-1, or SHP-2 SH2-containing decoy proteins on Fc gamma RIIB1 signaling. Results demonstrate the SHIP is the predominant intracellular ligand for the phosphorylated Fc gamma RIIB1 ITIM, although the SHP-2 decoy exhibits some ability to bind Fc gamma RIIB1 and block Fc receptor function. The SHIP SH2, while not affecting Fc gamma RIIB1 tyrosyl phosphorylation, blocks receptor-mediated recruitment of SHIP, SHIP phosphorylation, recruitment of p52 Shc, phosphatidylinositol 3,4,5-trisphosphate hydrolysis, inhibition of mitogen-activated protein kinase activation, and, albeit more modestly, Fc gamma RIIB1 inhibition of Ca2+ mobilization. Taken together, results implicate ITIM interactions with SHIP as a major mechanism of Fc gamma RIIB1-mediated inhibitory signaling.
Nakamura
K
K
Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA.
Brauweiler
A
A
Cambier
J C
JC
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D006868:Hydrolysis; D047908:Intracellular Signaling Peptides and Proteins; D016393:Lymphoma, B-Cell / Q000201:enzymology / Q000235:genetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009842:Oligopeptides; D010455:Peptides / Q000235:genetics; D018129:Phosphatidylinositol Phosphates / Q000037:antagonists & inhibitors / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D010766:Phosphorylation; D011485:Protein Binding / Q000276:immunology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D011940:Receptor Aggregation / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D017452:Receptors, IgG / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000037:antagonists & inhibitors / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics / Q000276:immunology*
D047908:Intracellular Signaling Peptides and Proteins; D009842:Oligopeptides; D010455:Peptides; D018129:Phosphatidylinositol Phosphates; D011947:Receptors, Antigen, B-Cell; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D014443:Tyrosine; C085706:FLAG peptide; D020928:Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D002118:Calcium