Insulin-like growth factor I receptors on mouse neuroblastoma cells. Two beta subunits are derived from differences in glycosylation.
We have characterized receptors for the insulin-like growth factor (IGF-I) on the mouse neuroblastoma cell line N18 as well as NG108, the hybrid cell line of N18 and rat glioma (C6). In this cell-free system, IGF-I and insulin stimulated the phosphorylation of 95-kDa and 105-kDa proteins. Using appropriate antibodies we were able to demonstrate that the IGF-I receptor beta subunit has two subtypes of 95 kDa and 105 kDa. On the other hand, insulin receptor beta subunit is a separate single 95-kDa protein. Enzymatic digestion of IGF-I receptor beta subunit subtypes by glycopeptidase F resulted in similar molecular masses (84 kDa and 86 kDa) on SDS-PAGE, which suggests that the difference in molecular masses between two subtypes is attributable to the differences in N-linked complex-type carbohydrate chains on the extracellular domain of beta subunits. This conclusion is further supported by peptides of similar molecular mass following staphylococcal V8 protease digestion. Analysis of IGF-I receptor beta subunit subtypes in these cells may provide insights into the mechanism of action of IGF-I on neural tissues.
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Diabetes Branch, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Wilson
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GL
Leroith
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D000818:Animals; D002460:Cell Line; D007328:Insulin / Q000494:pharmacology; D009447:Neuroblastoma / Q000032:analysis*; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D011972:Receptor, Insulin / Q000032:analysis* / Q000276:immunology / Q000502:physiology; D017451:Receptors, Somatomedin
D007328:Insulin; D010750:Phosphoproteins; D017451:Receptors, Somatomedin; D011972:Receptor, Insulin