Functional insulin-like growth factor I receptors are expressed by neural-derived continuous cell lines

High affinity insulin-like growth factor I (IGF-I) receptors are expressed by two human neural derived cell lines, SK-N-SH and SK-N-MC. Specific [125I]IGF-I binding to crude membranes was 23.4% for SK-N-SH and 10.7% for SK-N-MC, with 50% inhibition of binding by unlabeled IGF-I between 0.6-0.7 nM. Scatchard analysis of crude membrane binding was linear, whereas Scatchard analysis after wheat germ agglutinin purification of the receptor became curvilinear. The IGF-I receptor alpha-subunits of SK-N-SH have an apparent Mr of 126K, whereas that for SK-N-MC is 132K. Despite these differences in alpha-subunit structure both cell lines demonstrate IGF-I-induced autophosphorylation of their own beta-subunits as well as specific IGF-I induced tyrosine kinase activity, suggesting normal coupling between the ligand-binding alpha-subunit and the tyrosine kinase-containing beta-subunit. Furthermore, IGF-I stimulated iododeoxyuridine uptake in both SK-N-SH and SK-N-MC in a dose-dependent manner, suggesting that these cells may be used to study the role of IGF-I action on neural tissues.