title: Insulin-dependent phosphorylation of a 70-kDa protein in light microsomes from rat adipocytes.
abstract: In order to discover possibly novel insulin receptor substrates and/or downstream targets in the insulin signaling pathway, we established a cell-free system for this purpose using purified insulin receptor and subcellular fractions from rat adipocytes as a sourse of cellular substrates. Under these conditions, we have found a 70-kDa protein (pp70) in fat cells that is tyrosine-phosphorylated by the activated insulin receptor. Using sucrose velocity gradient sedimentation we also show that pp70 cofractionate a particulate fraction containing IRS-1 but not with GLUT-4 vesicle-enriched fractions. Our results suggest that pp70 may be an endogenous substrate for the insulin receptor tyrosine kinase.
authors.affiliation: Department of Biochemistry, Boston University School of Medicine, 715 Albany Street, Boston, Massachusetts, 02118, USA.
authors.forename: C
authors.initials: C
authors.lastname: Martinez
authors.forename: G
authors.initials: G
authors.lastname: Vallega
authors.forename: P F
authors.initials: PF
authors.lastname: Pilch
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000737:chemistry* / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D008297:Male; D051379:Mice; D008861:Microsomes / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C526296:Irs1 protein, rat; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; C495692:SLC2A4 protein, human; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; D019000:Phosphotyrosine; D011972:Receptor, Insulin