title: Monoclonal antibodies to receptors for insulin and somatomedin-C.
abstract: Three monoclonal antibodies, designated alpha IR-1, alpha IR-2, and alpha IR-3, were prepared by fusing FO myeloma cells with spleen cells from a mouse immunized with a partially purified preparation of insulin receptors from human placenta. These antibodies were characterized by their ability to immunoprecipitate solubilized receptors labeled with 125I-insulin or 125I-somatomedin-C in the presence or absence of various concentrations of unlabeled insulin or somatomedin-C. alpha IR-1 preferentially immunoprecipitates insulin receptors and also less effectively immunoprecipitates somatomedin-C receptors, while alpha IR-2 and alph IR-3 preferentially immunoprecipitate somatomedin-C receptors, but may also weakly immunoprecipitate insulin receptors. These three monoclonal antibodies, as well as A410, a rabbit polyclonal antibody, were used to immunoprecipitate insulin and somatomedin-C receptors from solubilized human lymphoid (IM-9) cells and human placenta membranes that had been 125I-labeled with lactoperoxidase. Analysis of the immunoprecipitates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that both receptors are composed of alpha and beta subunits. The beta subunit of the insulin receptor (immunoprecipitated by alpha IR-1 and A410) has a slightly more rapid mobility than the corresponding subunit of the somatomedin-C receptor (immunoprecipitated by alpha IR-2 and alpha IR-3). Interestingly, the alpha subunit of the placenta somatomedin-C receptor has a slightly faster mobility than its counterpart from IM-9 cells. Immunoprecipitation of receptor that had been reduced and denatured to generate isolated subunits indicates that alpha IR-2 and alpha IR-3 interact with the alpha subunit of the somatomedin-C receptor while A410 interacts with both subunits of the insulin receptor. alpha IR-1 failed to react with reduced and denatured receptors.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D001667:Binding, Competitive; D002460:Cell Line; D005260:Female; D006801:Humans; D007163:Immunosorbent Techniques; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I; D007784:Lactoperoxidase; D008221:Lymphoid Tissue / Q000032:analysis; D010920:Placenta / Q000032:analysis; D011247:Pregnancy; D011972:Receptor, Insulin / Q000276:immunology*; D011956:Receptors, Cell Surface / Q000276:immunology*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007328:Insulin; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007784:Lactoperoxidase; D011972:Receptor, Insulin