title: Guanosine triphosphatase-activating protein-associated protein, but not src-associated protein p68 in mitosis, is a part of insulin signaling complexes.
abstract: The insulin receptor, following insulin stimulation of cells, triggers formation of various signaling complexes. In rat HTC hepatoma cells overexpressing normal human insulin receptors (HTC-IR), p85 regulatory subunit of phosphatidylinositol-3-kinase (PI3K) forms signaling complexes containing the insulin receptor, insulin receptor substrate 1 (IRS-1), guanosine triphosphatase-activating protein (GAP) and 60-70 kDa phosphotyrosine proteins (p60-70). In the present study, we demonstrate that p60-70 interacts directly with the p85 subunit via src homology 2 domain of the latter. Employing antibodies specific to two p85 isoforms, p85alpha and p85beta, we demonstrate that HTC-IR cells express both p85 isoforms, and these isoforms induce the formation of similar signaling complexes in response to insulin. p60-70, present in both alpha-p85alpha and alpha-p85beta immunoprecipitates, is a GAP-associated protein, but is distinct from the p68 src-associated protein in mitosis (Sam68) by several criteria. These data suggest that 1) GAP-associated protein, but not Sam68, is a part of insulin signaling complexes; and 2) p85alpha and p85beta form similar, but distinct, insulin receptor signaling complexes.
authors.affiliation: Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033, USA. csung@hsc.usc.edu
authors.forename: C K
authors.initials: CK
authors.lastname: Sung
authors.forename: W S
authors.initials: WS
authors.lastname: Choi
authors.forename: V
authors.initials: V
authors.lastname: Sanchez-Margalet
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D006801:Humans; D007163:Immunosorbent Techniques; D007328:Insulin / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental; D058619:Maltose-Binding Proteins; D008938:Mitosis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D011994:Recombinant Proteins; D015398:Signal Transduction; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D007328:Insulin; C489559:KHDRBS1 protein, human; D058619:Maltose-Binding Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin