title: Assembly of insulin/insulin-like growth factor-1 hybrid receptors in vitro.
abstract: Insulin and Mn/MgATP treatment of immunoaffinity-purified alpha beta heterodimeric insulin receptors induced the formation of an alpha 2 beta 2 heterotetrameric insulin receptor complex. In contrast, insulin-like growth factor-1 (IGF-1) treatment was completely ineffective in inducing the association of alpha beta heterodimeric insulin receptors. Similarly, IGF-1 or Mn/MgATP, but not insulin, treatment of immunoaffinity-purified alpha beta heterodimeric IGF-1 receptors induced the formation of an alpha 2 beta 2 heterotetrameric IGF-1 receptor complex. A monoclonal antibody specific for the insulin receptor (MA5) completely immunoprecipitated all the insulin binding activity from both the alpha 2 beta 2 heterotetrameric and alpha beta heterodimeric insulin receptor complexes but did not immunoprecipitate IGF-1 receptors. Conversely, the IGF-1 receptor-specific monoclonal antibody (alpha IR-3) immunoprecipitated all the IGF-1 binding activity, but not insulin receptors. The simultaneous treatment of pooled equal amounts of alpha beta heterodimeric insulin and IGF-1 receptors with a combination of insulin and IGF-1 resulted in the formation of alpha 2 beta 2 heterotetrameric insulin and IGF-1 receptor complexes. However, in the mixed alpha 2 beta 2 heterotetrameric receptor fraction MA5 immunoprecipitated 94% of the insulin binding in addition to 27% of the IGF-1 binding activity whereas alpha IR-3 immunoprecipitated 97% of the IGF-1 binding in addition to 38% of the insulin binding activity. Treatment of the mixed alpha beta heterodimeric insulin and IGF-1 receptors with Mn/MgATP also resulted in the formation of cross-immunoreactive (42-46%) alpha 2 beta 2 heterotetrameric receptors. These data directly demonstrate the formation of insulin/IGF-1 hybrid receptors by both a combination of insulin plus IGF-1 or Mn/MgATP treatment of purified human placenta alpha beta heterodimeric insulin and IGF-1 half-receptors in vitro.
authors.affiliation: Department of Physiology and Biophysics, University of Iowa, Iowa City 52242.
authors.forename: J L
authors.initials: JL
authors.lastname: Treadway
authors.forename: B D
authors.initials: BD
authors.lastname: Morrison
authors.forename: I D
authors.initials: ID
authors.lastname: Goldfine
authors.forename: J E
authors.initials: JE
authors.lastname: Pessin
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D055503:Protein Multimerization; D011972:Receptor, Insulin / Q000302:isolation & purification / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin
chemical_list: D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D008345:Manganese; D007334:Insulin-Like Growth Factor I; D000255:Adenosine Triphosphate; D011972:Receptor, Insulin; D008274:Magnesium