title: Regulation of Cbl molecular interactions by the co-receptor molecule CD43 in human T cells.
abstract: CD43, one of the most abundant glycoproteins on the T cell surface, has been implicated in selection and maturation of thymocytes and migration, adhesion, and activation of mature T cells. The adapter molecule Cbl has been shown to be a negative regulator of Ras. Furthermore, it may also regulate intracellular signaling through the formation of several multi-molecular complexes. Here we investigated the role of Cbl in the CD43-mediated signaling pathway in human T cells. Unlike T cell receptor signaling, the interaction of the adapter protein Cbl with Vav and phosphatidylinositol 3-kinase, resulting from CD43-specific signals, is independent of Cbl tyrosine phosphorylation, suggesting an alternative mechanism of interaction. CD43 signals induced a Cbl serine phosphorylation-dependent interaction with the tau-isoform of 14-3-3. protein. Protein kinase C-mediated Cbl serine phosphorylation was required for this interaction, because the PKC inhibitor RO-31-8220 prevented it, as well as 14-3-3 dimerization. Moreover, mutation of Cbl serine residues 619, 623, 639, and 642 abolished the interaction between Cbl and 14-3-3. Overexpression of Cbl in Jurkat cells inhibited the CD43-dependent activation of the mitogen-activated protein kinase (MAPK) pathway and AP-1 transcriptional activity, confirming nevertheless a negative role for Cbl in T cell signaling. However, under normal conditions, PKC activation resulting from CD43 engagement was required to activate the MAPK pathway, suggesting that phosphorylation of Cbl on serine residues by PKC and its association with 14-3-3 molecules may play a role in preventing the Cbl inhibitory effect on the Ras-MAPK pathway. These data suggest that by inducing its phosphorylation on serine residues, CD43-mediated signals may regulate the molecular associations and functions of the Cbl adapter protein.
authors.affiliation: Instituto de Biotecnologia/Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, MOR 62250, Mexico.
authors.forename: G
authors.initials: G
authors.lastname: Pedraza-Alva
authors.forename: S
authors.initials: S
authors.lastname: Sawasdikosol
authors.forename: Y C
authors.initials: YC
authors.lastname: Liu
authors.forename: L B
authors.initials: LB
authors.lastname: Mérida
authors.forename: M E
authors.initials: ME
authors.lastname: Cruz-Muñoz
authors.forename: F
authors.initials: F
authors.lastname: Oceguera-Yañez
authors.forename: S J
authors.initials: SJ
authors.lastname: Burakoff
authors.forename: Y
authors.initials: Y
authors.lastname: Rosenstein
mesh_terms: D048948:14-3-3 Proteins; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018797:Cell Cycle Proteins; D004789:Enzyme Activation; D017930:Genes, Reporter; D006801:Humans; D019169:Jurkat Cells; D051917:Leukosialin; D008213:Lymphocyte Activation; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D050722:Oncogene Protein v-cbl; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D011940:Receptor Aggregation; D015682:Retroviridae Proteins, Oncogenic / Q000276:immunology / Q000378:metabolism*; D012694:Serine / Q000235:genetics / Q000378:metabolism; D012795:Sialoglycoproteins / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018797:Cell Cycle Proteins; D051917:Leukosialin; D020928:Mitogen-Activated Protein Kinases; D050722:Oncogene Protein v-cbl; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D015682:Retroviridae Proteins, Oncogenic; D012694:Serine; D012795:Sialoglycoproteins; D014446:Tyrosine 3-Monooxygenase; C465014:SPN protein, human; C496618:VAV1 protein, human