title: Essential and unique roles of PIP5K-gamma and -alpha in Fcgamma receptor-mediated phagocytosis.
abstract: The actin cytoskeleton is dynamically remodeled during Fcgamma receptor (FcgammaR)-mediated phagocytosis in a phosphatidylinositol (4,5)-bisphosphate (PIP(2))-dependent manner. We investigated the role of type I phosphatidylinositol 4-phosphate 5-kinase (PIP5K) gamma and alpha isoforms, which synthesize PIP(2), during phagocytosis. PIP5K-gamma-/- bone marrow-derived macrophages (BMM) have a highly polymerized actin cytoskeleton and are defective in attachment to IgG-opsonized particles and FcgammaR clustering. Delivery of exogenous PIP(2) rescued these defects. PIP5K-gamma knockout BMM also have more RhoA and less Rac1 activation, and pharmacological manipulations establish that they contribute to the abnormal phenotype. Likewise, depletion of PIP5K-gamma by RNA interference inhibits particle attachment. In contrast, PIP5K-alpha knockout or silencing has no effect on attachment but inhibits ingestion by decreasing Wiskott-Aldrich syndrome protein activation, and hence actin polymerization, in the nascent phagocytic cup. In addition, PIP5K-gamma but not PIP5K-alpha is transiently activated by spleen tyrosine kinase-mediated phosphorylation. We propose that PIP5K-gamma acts upstream of Rac/Rho and that the differential regulation of PIP5K-gamma and -alpha allows them to work in tandem to modulate the actin cytoskeleton during the attachment and ingestion phases of phagocytosis.
authors.affiliation: Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Yuntao S
authors.initials: YS
authors.lastname: Mao
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamaga
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhu
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Wei
authors.forename: Hui-Qiao
authors.initials: HQ
authors.lastname: Sun
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Mia
authors.initials: M
authors.lastname: Yun
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Gilbert
authors.initials: G
authors.lastname: Di Paolo
authors.forename: Michael
authors.initials: M
authors.lastname: Bennett
authors.forename: Ira
authors.initials: I
authors.lastname: Mellman
authors.forename: Charles S
authors.initials: CS
authors.lastname: Abrams
authors.forename: Pietro
authors.initials: P
authors.lastname: De Camilli
authors.forename: Christopher Y
authors.initials: CY
authors.lastname: Lu
authors.forename: Helen L
authors.initials: HL
authors.lastname: Yin
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010587:Phagocytosis; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D020033:Protein Isoforms; D017452:Receptors, IgG; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase