Insulin-like growth factor I receptors in neuronal and glial cells. Characterization and biological effects in primary culture.
Primary cultures of neuronal and glial cells from 1-day-old neonatal rats contain high affinity receptors for insulin-like growth factor I (IGF-I). The IC50 for displacement of 125I-IGF-I binding by unlabeled IGF-I was 3 nM for neuronal cells and 4 nM for glial cells. Unlabeled insulin was 20-50 times less potent. Apparent molecular mass of the alpha subunits of the IGF-I receptor was 125 kDa in neuronal and 135 kDa in glial cells. IGF-I induced autophosphorylation of the IGF-I receptor beta subunit in lectin-purified membrane preparations in a dose-dependent manner. The major phosphoamino acid of the beta subunit in both cell types was tyrosine in the IGF-I-stimulated state and serine in the basal state. Apparent molecular mass of the beta subunits of the IGF-I receptors was 91 kDa for neuronal and 95 kDa for glial cells. Tyrosine kinase activity of the IGF-I receptors was demonstrated by IGF-I-induced phosphorylation of the exogenous substrate poly(Glu, Tyr) 4:1 in both cell types. IGF-I had no effect on 2-deoxyglucose uptake in neuronal cells. In contrast, in glial cells, IGF-I stimulated 2-deoxyglucose uptake at very high doses, presumably acting via the insulin receptor. The effect of IGF-I as a neurotrophic growth factor in both neuronal and glial cells was demonstrated by its stimulation of [3H]thymidine incorporation. These findings suggest the IGF-I is an important growth factor in nervous tissue-derived cells.
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*; D017451:Receptors, Somatomedin; D011994:Recombinant Proteins / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism*
D017451:Receptors, Somatomedin; D011994:Recombinant Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D011494:Protein Kinases; D011972:Receptor, Insulin