title: A Ras activation pathway dependent on Syk phosphorylation of protein kinase C.
abstract: Protein kinase C (PKC) and Syk protein tyrosine kinase play critical roles in immune cell activation including that through the high-affinity IgE receptor, FcepsilonRI. Mechanisms by which PKC activation leads to the activation of Ras, a family of GTPases essential for immune cell activation, have been elusive. We present evidence that Tyr-662 and Tyr-658 of PKCbetaI and PKCalpha, respectively, are phosphorylated by Syk in the membrane compartment of FcepsilonRI-stimulated mast cells. These phosphorylations require prior PKC autophosphorylation of the adjacent serine residues (Ser-661 and Ser-657, respectively) and generate a binding site for the SH2 domain of the adaptor protein Grb-2. By recruiting the Grb-2/Sos complex to the plasma membrane, these conventional PKC isoforms contribute to the full activation of the Ras/extracellular signal-regulated kinase signaling pathway in FcepsilonRI-stimulated mast cells.
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121, USA. yuko@liai.org
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Jiro
authors.initials: J
authors.lastname: Kitaura
authors.forename: Libo
authors.initials: L
authors.lastname: Yao
authors.forename: Robert W
authors.initials: RW
authors.lastname: McHenry
authors.forename: Yu
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Alexandra C
authors.initials: AC
authors.lastname: Newton
authors.forename: Shin
authors.initials: S
authors.lastname: Kang
authors.forename: Roberta M
authors.initials: RM
authors.lastname: Kato
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: David J
authors.initials: DJ
authors.lastname: Rawlings
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kawakami
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001854:Bone Marrow Cells / Q000378:metabolism; D019556:COS Cells; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D005822:Genetic Vectors; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D000072377:Syk Kinase; D014443:Tyrosine / Q000737:chemistry; D018631:ras Proteins / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004792:Enzyme Precursors; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides; D020033:Protein Isoforms; D011506:Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins