title: Specific cell surface binding sites shared by human Pro-IGF-I Eb-peptides and rainbow trout Pro-IGF-I Ea-4-peptide.
abstract: Human pro-IGF-I Eb-peptide (hEb) and rainbow trout pro-IGF-I Ea-4-peptide (rtEa-4) have recently been shown to share unique biological activities [Gen. Comp. Endocrinol. 126 (2002) 342; Cell. Exp. Cell. Res. 280 (2002) 75]. To further understand the action mechanism of these proteins, we studied the binding properties of hEb-peptide and rtEa-4-peptide to intact human neuroblastoma cells (SK-N-F1) and membrane preparations. Human Eb-peptide and rtEa-4-peptide bind to a high-affinity binding site with an apparent dissociation constant of 3.2+/-1.9 x 10(-11) and 2.9+/-1.8 x 10(-11)M, respectively. Homologous displacement assay demonstrated the presence of a second binding site with an IC(50) of 4.8+/-2.6 x 10(-6)M for hEb-peptide and 2.1+/-0.6 x 10(-6)M for rtEa-4-peptide, respectively. Competition assays showed that hEb-peptide and rtEa-4-peptide shared common binding sites, distinct from those for IGF-I and insulin. In addition, chemical cross-linking studies revealed two specific binding complexes. Our findings support the notion that the initial step of pro-IGF-I E-peptide action is mediated through the interaction with conserved and specific putative membrane receptors on neuroblastoma cells.
authors.affiliation: Department of Molecular and Cell Biology and Biotechnology Center, University of Connecticut, 75 North Eagleville Road, U-3044, Storrs, CT 06269-3044, USA.
authors.forename: Ya-Huei
authors.initials: YH
authors.lastname: Kuo
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Chen
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001932:Brain Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003432:Cross-Linking Reagents; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D009447:Neuroblastoma / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D010455:Peptides; D011498:Protein Precursors; D011956:Receptors, Cell Surface; D007334:Insulin-Like Growth Factor I