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Gene Expression and Receptor Binding of Insulin‐Like Growth Factor‐II in Pig Choroid Plexus Epithelial Cells
Author(s) -
Nilsson Christer,
Blay Pilar,
Nielsen Finn C.,
Gammeltoft Steen
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09345.x
Subject(s) - choroid plexus , receptor , biology , endocrinology , insulin like growth factor , medicine , insulin like growth factor 1 receptor , insulin receptor , tyrosine kinase , receptor tyrosine kinase , microbiology and biotechnology , insulin like growth factor 2 , growth factor , insulin , biochemistry , insulin resistance , central nervous system
To elucidate the function of insulin‐like growth factor‐II (IGF‐II) in the choroid plexus, the gene expression and receptor binding of IGF‐II were studied in isolated epithelial cells from the porcine choroid plexus. The choroid plexus expressed multiple IGF‐II transcripts of 1.2, 1.6, 2.4, and 4.4 kb, at levels higher than those found in porcine liver and kidney. These data suggest that IGF‐II is synthesized by the choroid plexus. Choroid plexus epithelial cells contained high levels of IGF‐I receptors on the cell surface whereas very low levels of receptor binding were found for 125 I‐IGF‐II and I25l‐insulin. Solubilization of epithelial cells showed that a large proportion of the IGF‐I receptors were present in the detergent‐insoluble fraction whereas IGF‐II receptors and insulin receptors were concentrated in the detergent‐soluble fraction. These results suggest that IGF‐I receptors are located in clathrin‐coated pits of the plasma membrane whereas IGF‐II receptors and insulin receptors are present in endosomal vesicles. The tyrosine kinase activity of the IGF‐I receptor β‐subunit was stimulated by IGF‐I, IGF‐II, and insulin, in order of potency, suggesting that these peptides exert a regulatory function in the chdroid plexus epithelium. In conclusion, we propose that the IGF‐I receptor tyrosine kinase on the surface of the epithelial cells in the pig choroid plexus mediates effects of IGF‐I and IGF‐II, whereas IGF‐II receptors are down‐regulated due to the synthesis and secretion of IGF‐II in these cells.