title: Cutting Edge: Transmembrane phosphoprotein Csk-binding protein/phosphoprotein associated with glycosphingolipid-enriched microdomains as a negative feedback regulator of mast cell signaling through the FcepsilonRI.
abstract: Tyrosine phosphorylation in the cytoplasmic domains of FcepsilonRI by the Src family kinase Lyn initiates a signaling cascade leading to mast cell activation. In this study, we show that a recently identified transmembrane protein, Csk-binding protein (Cbp), also known as phospoprotein associated with glycosphingolipid-enriched microdomains (PAG), negatively regulates FcepsilonRI signaling. In rat basophilic leukemia (RBL)-2H3 cells, the levels of tyrosine phosphorylation of Cbp/PAG and its association with Csk, a negative regulator for Lyn, significantly elevate immediately after aggregation of FcepsilonRI. An overexpression of Cbp/PAG in RBL-2H3 cells inhibits FcepsilonRI-mediated cell activation. This is accompanied with decreased levels of tyrosine phosphorylation of FcepsilonRI, association of FcepsilonRI with Lyn, and FcepsilonRI-associated tyrosine kinase activity. These findings combined with the fact that Cbp/PAG, Lyn, and aggregated FcepsilonRI are localized to lipid rafts, suggest that upon FcepsilonRI aggregation Cbp/PAG down-regulates the receptor-associated Lyn activity through relocating Csk to rafts, thereby efficiently mediating feedback inhibition of FcepsilonRI signaling.
authors.affiliation: Division of Hygienic Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Ohtake
authors.forename: Naoki
authors.initials: N
authors.lastname: Ichikawa
authors.forename: Masato
authors.initials: M
authors.lastname: Okada
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yamashita
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation; D015536:Down-Regulation; D006028:Glycosphingolipids / Q000032:analysis; D008407:Mast Cells / Q000276:immunology*; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017455:Receptors, IgE / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases
chemical_list: D006028:Glycosphingolipids; D008565:Membrane Proteins; C408142:Pag1 protein, rat; D010750:Phosphoproteins; D017455:Receptors, IgE; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D002118:Calcium