title: Negative regulation of Lyn protein-tyrosine kinase by c-Cbl ubiquitin-protein ligase in Fc epsilon RI-mediated mast cell activation.
abstract: BACKGROUND
  Recent studies have demonstrated that c-Cbl functions as a ubiquitin-protein ligase toward immune receptors and non-receptor protein-tyrosine kinase Syk by facilitating their ubiquitination and subsequent targeting to proteasomes. However, it was not clear whether Src family kinase Lyn is regulated by the Cbl family of ubiquitin-protein ligases.
  
  
  RESULTS
  Aggregation of the high affinity IgE receptor (Fc epsilon RI) induces the rapid ubiquitination of Lyn in rat basophilic leukaemia RBL-2H3 cells. Treatment of cells with a proteasome inhibitor enhances the ubiquitination of Lyn. Stimulation of Fc epsilon RI results in the association of Lyn with c-Cbl and Cbl-b, both of which then become tyrosine phosphorylated. Co-transfection study shows that both c-Cbl and Cbl-b could induce the ubiquitination of activated Lyn in COS cells. Furthermore, over-expression of membrane-anchored form of c-Cbl inhibits the Fc epsilon RI-mediated degranulation and cytokine gene production in RBL-2H3 cells by the down-regulation of the kinase activity of Lyn through the enhanced ubiquitination.
  
  
  CONCLUSIONS
  These results demonstrate that Lyn is down-regulated by c-Cbl-mediated ubiquitination and subsequent degradation in proteasome after Fc epsilon RI stimulation in mast cells. Targeting of c-Cbl in the lipid raft results in the inhibition of Fc epsilon RI-mediated mast cell activation.
authors.affiliation: Division of Proteomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Shinkou
authors.initials: S
authors.lastname: Kyo
authors.forename: Kiyonao
authors.initials: K
authors.lastname: Sada
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Qu
authors.forename: Koichiro
authors.initials: K
authors.lastname: Maeno
authors.forename: S M Shahjahan
authors.initials: SM
authors.lastname: Miah
authors.forename: Keiko
authors.initials: K
authors.lastname: Kawauchi-Kamata
authors.forename: Hirohei
authors.initials: H
authors.lastname: Yamamura
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D015471:Leukemia, Basophilic, Acute / Q000473:pathology; D008407:Mast Cells / Q000166:cytology*; D010766:Phosphorylation; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D011518:Proto-Oncogene Proteins; D017455:Receptors, IgE; D025801:Ubiquitin; D014443:Tyrosine; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D001619:beta-N-Acetylhexosaminidases