title: Critical role for scaffolding adapter Gab2 in Fc gamma R-mediated phagocytosis.
abstract: Grb2-associated binder 2 (Gab2), a member of the Dos/Gab subfamily scaffolding molecules, plays important roles in regulating the growth, differentiation, and function of many hematopoietic cell types. In this paper, we reveal a novel function of Gab2 in Fcgamma receptor (FcgammaR)-initiated phagocytosis in macrophages. Upon FcgammaR activation, Gab2 becomes tyrosyl phosphorylated and associated with p85, the regulatory subunit of phosphoinositide 3-kinase (PI3K), and the protein-tyrosine phosphatidylinositol Shp-2. FcgammaR-mediated phagocytosis is severely impaired in bone marrow-derived macrophages from Gab2-/- mice. The defect in phagocytosis correlates with decreased FcgammaR-evoked activation of Akt, a downstream target of PI3K. Using confocal fluorescence microscopy, we find that Gab2 is recruited to the nascent phagosome, where de novo PI3K lipid production occurs. Gab2 recruitment requires the pleckstrin homology domain of Gab2 and is sensitive to treatment with the PI3K inhibitor wortmannin. The Grb2 binding site on Gab2 also plays an auxiliary role in recruitment to the phagosome. Because PI3K activity is required for FcgammaR-mediated phagocytosis, our results indicate that Gab2 acts as a key component of FcgammaR-mediated phagocytosis, most likely by amplifying PI3K signaling in the nascent phagosome.
authors.affiliation: Harvard Institutes of Medicine, 77 Ave. Louis Pasteur, HIM 1047 Boston, MA 02115, USA. hgu@caregroup.harvard.edu
authors.forename: Haihua
authors.initials: H
authors.lastname: Gu
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Botelho
authors.forename: Min
authors.initials: M
authors.lastname: Yu
authors.forename: Sergio
authors.initials: S
authors.lastname: Grinstein
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Neel
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011961:Receptors, Fc / Q000378:metabolism*; D017452:Receptors, IgG; D015398:Signal Transduction / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011961:Receptors, Fc; D017452:Receptors, IgG; C499172:Fcgr2b protein, mouse; C490894:Gab2 protein, mouse; C516725:Ptpn11 protein, mouse