RESUMEN
SHPTP2 is a ubiquitously expressed tyrosine-specific protein phosphatase that contains two amino-terminal Src homology 2 (SH2) domains responsible for its association with tyrosine-phosphorylated proteins. In this study, expression of dominant interfering mutants of SHPTP2 was found to inhibit insulin stimulation of c-fos reporter gene expression and activation of the 42-kDa (Erk2) and 44-kDa (Erk1) mitogen-activated protein kinases. Cotransfection of dominant interfering SHPTP2 mutants with v-Ras or Grb2 indicated that SHPTP2 regulated insulin signaling either upstream of or in parallel to Ras function. Furthermore, phosphotyrosine blotting and immunoprecipitation identified the 125-kDa focal adhesion kinase (pp125FAK) as a substrate for insulin-dependent tyrosine dephosphorylation. These data demonstrate that SHPTP2 functions as a positive regulator of insulin action and that insulin signaling results in the dephosphorylation of tyrosine-phosphorylated pp125FAK.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Insulina/farmacología , Proteínas Quinasas Activadas por Mitógenos , Proteínas Tirosina Fosfatasas/metabolismo , Transducción de Señal/fisiología , Animales , Células CHO , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Moléculas de Adhesión Celular/química , Moléculas de Adhesión Celular/metabolismo , Extractos Celulares/química , Cricetinae , ADN Complementario , Quinasa 1 de Adhesión Focal , Proteína-Tirosina Quinasas de Adhesión Focal , Proteína Adaptadora GRB2 , Genes Reporteros , Genes fos/genética , Péptidos y Proteínas de Señalización Intracelular , Proteína Quinasa 1 Activada por Mitógenos , Proteína Quinasa 3 Activada por Mitógenos , Mutación/fisiología , Fosforilación , Fosfotirosina , Proteína Tirosina Fosfatasa no Receptora Tipo 11 , Proteína Tirosina Fosfatasa no Receptora Tipo 6 , Proteínas Tirosina Fosfatasas/genética , Proteínas Tirosina Quinasas/química , Proteínas Tirosina Quinasas/metabolismo , Proteínas/fisiología , Transducción de Señal/efectos de los fármacos , Transcripción Genética , Transfección , Tirosina/análogos & derivados , Tirosina/análisis , Proteínas ras/fisiologíaRESUMEN
Adenylate cyclase specific activities in membranes isolated from chicken embryo fibroblasts transformed by Rous sarcoma virus are significantly lower than the specific activity of the enzyme in normal membranes. Since normal and transformed membranes have different phospholipid and fatty acid compositions, adenylate cyclase activities were examined in normal and transformed membranes which had been supplemented with polar head groups or fatty acids. Basal, fluoride, and prostaglandin E1-stimulated activities changed systematically with phospholipid composition. Increases in the primary amino group of the phospholipid polar head groups or the average degree of fatty acid unsaturation both inhibited adenylate cyclase activity. In general, adenylate cyclase activities in normal membranes were more sensitive to phospholipid compositional changes compared to adenylate cyclase in transformed membranes. The data indicate that the lower adenylate cyclase activities in transformed membranes are not solely attributable to phospholipid changes but do suggest that increases in the percentage of phosphatidylethanolamine may contribute to the lower adenylate cyclase activities in transformed membranes.