title: Dual phosphorylation of phosphoinositide 3-kinase adaptor Grb2-associated binder 2 is responsible for superoxide formation synergistically stimulated by Fc gamma and formyl-methionyl-leucyl-phenylalanine receptors in differentiated THP-1 cells.
abstract: The class Ia phosphoinositide (PI) 3-kinase consisting of p110 catalytic and p85 regulatory subunits is activated by Tyr kinase-linked membrane receptors such as FcgammaRII through the association of p85 with the phosphorylated receptors or adaptors. The heterodimeric PI 3-kinase is also activated by G protein-coupled chemotactic fMLP receptors, and activation of the lipid kinase plays an important role in various immune responses, including superoxide formation in neutrophils. Although fMLP-induced superoxide formation is markedly enhanced in FcgammaRII-primed neutrophils, the molecular mechanisms remain poorly characterized. In this study, we identified two Tyr-phosphorylated proteins, c-Cbl (Casitas B-lineage lymphoma) and Grb2-associated binder 2 (Gab2), as PI 3-kinase adaptors that are Tyr phosphorylated upon the stimulation of FcgammaRII in differentiated neutrophil-like THP-1 cells. Interestingly, Gab2 was, but c-Cbl was not, further Ser/Thr phosphorylated by fMLP. Thus, the adaptor Gab2 appeared to be dually phosphorylated at the Ser/Thr and Tyr residues through the two different types of membrane receptors. The Ser/Thr phosphorylation of Gab2 required the activation of extracellular signal-regulated kinase, and fMLP receptor stimulation indeed activated extracellular signal-regulated kinase in the cells. Enhanced superoxide formation in response to Fcgamma and fMLP was markedly attenuated when the Gab2 Ser/Thr phosphorylation was inhibited. These results show the importance of the dual phosphorylation of PI 3-kinase adaptor Gab2 for the enhanced superoxide formation in neutrophil-type cells.
authors.affiliation: Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Momose
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kurosu
authors.forename: Noriko
authors.initials: N
authors.lastname: Tsujimoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Kontani
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tsujita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishina
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Katada
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000378:metabolism; D004357:Drug Synergism; D005419:Flavonoids / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism* / Q000502:physiology; D018129:Phosphatidylinositol Phosphates / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D044042:Receptors, Formyl Peptide / Q000502:physiology*; D017452:Receptors, IgG / Q000378:metabolism / Q000502:physiology*; D012694:Serine / Q000037:antagonists & inhibitors / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D013912:Threonine / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D005419:Flavonoids; C409587:GRAP2 protein, human; D018129:Phosphatidylinositol Phosphates; D044042:Receptors, Formyl Peptide; D017452:Receptors, IgG; C060974:phosphatidylinositol 3,4,5-triphosphate; D013481:Superoxides; D013912:Threonine; D012694:Serine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one