title: Reversal by insulin of concanavalin A inhibition of myotube formation and evidence for common binding sites.
abstract: Concanavalin A (Con A) inhibits fusion of trypsin-treated myoblasts. This inhibition is reversed by the addition of supraphysiological concentrations (4 micrograms/ml) of insulin either during continuous presence in culture or by pulse additions at 36 and 48 h of culture, just before the time that cultures not treated with Con A undergo myoblast fusion. This reversal is not due to the mitogenic effects of insulin. Under reversal conditions, no specific displacement of bound [125I]iodo-Con A was detected nor did insulin stimulate metabolite uptake. Cell surface replicas of hemocyanin-tagged Con A showed that insulin reversal of the inhibition of myotube formation correlated with the alteration of Con A-binding sites from a clustered configuration present in the inhibited cells to a dispersed state correlated with normal myotube formation. Although a causal relationship has yet to be shown, the data suggest that insulin-mediated reversal of Con A inhibition of myoblast fusion may be related to the ability of insulin at supraphysiological levels to alter the translational mobility of cell surface components containing glucose and/or mannose residues capable of binding Con A. Evidence is presented which suggests that insulin and Con A share common binding sites, since in the physiological range of insulin concentrations (1 ng/ml), Con A pretreatments results in an inhibition of specific [125I]iodo-insulin binding, and antagonistic interactions of insulin and Con A on metabolite uptake and cell proliferation occur. Thus, it appears that the insulin receptors of developing skeletal muscle are glycoproteins containing glycopyranosides.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002642:Chick Embryo; D003208:Concanavalin A / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D011952:Receptors, Concanavalin A / Q000187:drug effects / Q000378:metabolism*; D011955:Receptors, Drug / Q000378:metabolism*
chemical_list: D007328:Insulin; D011952:Receptors, Concanavalin A; D011955:Receptors, Drug; D003208:Concanavalin A; D011972:Receptor, Insulin; D002118:Calcium