Reciprocal modulation of insulin and insulin-like growth factor-I receptor affinity by calcium.
In contrast to its stimulation of insulin binding to human placental membranes, calcium inhibited the binding of insulin-like growth factor-I. The effects on receptors for both peptides were half-maximal at 2 mM calcium, and were entirely due to alterations in high affinity binding sites for the respective ligands. Calcium decreased the affinity of insulin-like growth factor-I sites, while stimulating the expression of high affinity insulin sites. Competition by each peptide at the receptor for the other peptide was enhanced by calcium. Modulation by calcium might provide a mechanism to amplify functional differences between the two structurally similar receptors.
D001667:Binding, Competitive; D002118:Calcium / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D007328:Insulin / Q000502:physiology*; D007700:Kinetics; D010455:Peptides / Q000502:physiology*; D010920:Placenta; D011247:Pregnancy; D011972:Receptor, Insulin / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000502:physiology*
D007328:Insulin; D010455:Peptides; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D011972:Receptor, Insulin; D002118:Calcium