Abstract
The presence of high concentrations of IGF-II in cerebrospinal fluid and brain, as well as the prominence of receptors in cortical tissues, make the CNS an attractive site for the study of IGF-II binding and action. B-104 is a transformed rat neuroblastoma cell line whose neuronal qualities include neurotransmitter synthesis and the ability to project axodendritic processes. We observed steady-state binding of 125-I-IGF-II to B-104 membranes between 1.5 and 4 hrs at optimal conditions of 25*C, pH 7-8. Specific binding averaged 12.2±4.0% per 100 ug/ml membrane protein, compared with 125-I-IGF-I binding of 10.1±2.9%. 125-I-IGF-II binding was minimally inhibited (<20%) by insulin concentrations as high as 100 ug/ml. In the presence of unlabeled IGF-II (0.5-5ng/ml), 125-I-IGF-II binding was increased by as much as 50% over baseline; at higher concentrations, 125-I-IGF-II binding was inhibited, with 50% displacement at 50 ng/ml. We observed a similar increase in 125-I-IGF-II binding in the presence of unlabeled IGF-I at concentrations ranging from 1-400 ng/ml. When 125-I-IGF-II was cross-linked to membranes, solubilized, and immunoprecipitated with a specific antibody for the rat IGF-II receptor, a classical type II receptor (Mr∼240K) was visualized upon electrophoresis. These results demonstrate the presence in B-104 cells of a specific high affinity type II receptor, as well as a membrane-bound binding protein, whose existence in conditioned medium was confirmed by activated charcoal assay. B-104 should serve as an appropriate and intriguing in vitro model for future study of IGF receptors and action in the CNS.
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Sturm, M., Pham, H. & Rosenfeld, R. INSULIN-LIKE GROWTH FACTOR-II (IGF-II) RECEPTORS IN RAT NEUROBLASTOMA CELLS. Pediatr Res 21 (Suppl 4), 254 (1987). https://doi.org/10.1203/00006450-198704010-00524
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DOI: https://doi.org/10.1203/00006450-198704010-00524