title: The inositol phosphatase SHIP-2 down-regulates FcgammaR-mediated phagocytosis in murine macrophages independently of SHIP-1.
abstract: FcgammaR-mediated phagocytosis of IgG-coated particles is a complex process involving the activation of multiple signaling enzymes and is regulated by the inositol phosphatases PTEN (phosphatase and tensin homolog deleted on chromosome 10) and SHIP-1 (Src homology [SH2] domain-containing inositol phosphatase). In a recent study we have demonstrated that SHIP-2, an inositol phosphatase with high-level homology to SHIP-1, is involved in FcgammaR signaling. However, it is not known whether SHIP-2 plays a role in modulating phagocytosis. In this study we have analyzed the role of SHIP-2 in FcgammaR-mediated phagocytosis using independent cell models that allow for manipulation of SHIP-2 function without influencing the highly homologous SHIP-1. We present evidence that SHIP-2 translocates to the site of phagocytosis and down-regulates FcgammaR-mediated phagocytosis. Our data indicate that SHIP-2 must contain both the N-terminal SH2 domain and the C-terminal proline-rich domain to mediate its inhibitory effect. The effect of SHIP-2 is independent of SHIP-1, as overexpression of dominant-negative SHIP-2 in SHIP-1-deficient primary macrophages resulted in enhanced phagocytic efficiency. Likewise, specific knockdown of SHIP-2 expression using siRNA resulted in enhanced phagocytosis. Finally, analysis of the molecular mechanism of SHIP-2 down-regulation of phagocytosis revealed that SHIP-2 down-regulates upstream activation of Rac. Thus, we conclude that SHIP-2 is a novel negative regulator of FcgammaR-mediated phagocytosis independent of SHIP-1.
authors.affiliation: Molecular, Cellular, and Developmental Biology Program, The Ohio State University, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Ai
authors.forename: Amita
authors.initials: A
authors.lastname: Maturu
authors.forename: Wesley
authors.initials: W
authors.lastname: Johnson
authors.forename: Yijie
authors.initials: Y
authors.lastname: Wang
authors.forename: Clay B
authors.initials: CB
authors.lastname: Marsh
authors.forename: Susheela
authors.initials: S
authors.lastname: Tridandapani
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D005799:Genes, Dominant; D006801:Humans; D000072181:Inositol Polyphosphate 5-Phosphatases; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010587:Phagocytosis; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D017452:Receptors, IgG / Q000276:immunology / Q000378:metabolism*; D012756:Sheep; D018909:src Homology Domains
chemical_list: C499172:Fcgr2b protein, mouse; C485700:Fcgr3 protein, mouse; D034741:RNA, Small Interfering; D017452:Receptors, IgG; D051057:Proto-Oncogene Proteins c-akt; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606430:INPP5D protein, human; C098706:INPPL1 protein, human; C000606433:Inpp5d protein, mouse; C000606435:Inppl1 protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases