Abstract
In previous studies, we identified binding sites for Sm/IGFs on cultured astroglial cells purified from neonatal rat cerebral cortices by high resolution autoradiography. To further characterize these binding sites, we performed traditional binding studies. Binding for each Sm/IGF is specific, saturable and reversible, and 90% of the binding occurs within 6 hours at 4°C. Competitive binding with Sm-C/IGF-I yields curvilinear Scatchard plots, while studies with IGF-II and MSA yields linear plots, suggesting that two receptor species bind Sm-C/IGF-I and one binds IGF-II and MSA. These findings are supported by affinity crosslinking studies with labeled Sm/IGFs, using disuccinimidyl suberate as a crosslinking agent, followed by solubilization, reduction and analysis on SDS PAGE. 125I-Sm-C/IGF-I binds to moieties with Mr of 260K (the type II receptor) and 130K (α subunit of the type I receptor), while 125I-IGF-II and 125I-MSA binds primarily to the Mr 260K moiety. Concurrent studies of Sm/IGF stimulation of 3H-thymidine incorporation into astroglial cells reveal that both IGF-II and MSA are more potent than Sm-C/IGF-I. These data suggest that astroglial cells possess both type I and type II Sm/IGF receptors and that proliferation in response to Sm/IGFs can be mediated through type II receptors.
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Han, V., D'ercole, A., Lauder, J. et al. 100 RECEPTOR BINDING OF SOMATOMEDIN/INSULIN-LIKE GROWTH FACTORS (Sm/IGFs) ON CULTURED RAT ASTROGLIAL CELLS. Pediatr Res 19, 620 (1985). https://doi.org/10.1203/00006450-198506000-00120
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DOI: https://doi.org/10.1203/00006450-198506000-00120