BINDING OF INSULIN-LIKE GROWTH FACTOR-II (IGF-II) BY HUMAN CATION-INDEPENDENT MANNOSE 6-PHOSPHATE RECEPTOR IGF-II RECEPTOR EXPRESSED IN RECEPTOR-DEFICIENT MOUSE L-CELLS

Mouse L cells deficient in expression of the murine cation-independent mannose 6-phosphate receptor/insulin-like growth factor II receptor (CI-MPR/ IGF-IIR) were stably transfected with a plasmid containing the cDNA for the human receptor. Transfected cells expressed high levels of the human receptor which functioned in the transport of lysosomal enzymes and was capable of binding 126I-IGF-II, both at the cell surface and intracellularly. Cell surface binding of 126I-IGF-II by the receptor could be inhibited by pretreatment of cells with antibodies to the receptor or by coincubation with the lysosomal enzyme, β-glucuronidase. Expression of the receptor conferred on transfected cells the ability to internalize and degrade 125I-IGF-II. Cells transfected with the parental vector and those expressing the human CI-MPR/IGF-IIR were found to express an atypical binding site for IGF-II that was distinct from the CI-MPR/IGF-IIR and the type IIGF-receptor. The availability of two cell lines, one of which overexpresses the human CI-MPR/IGF-IIR and one deficient in expression of the murine receptor, may help in the analysis of the role of the receptor in mediating the biological effects of IGF-II. They should also be useful in examining the significance of binding of ligands, such as transforming growth factor-β1 precursor and proliferin to this receptor. © 1990 by The American Society for Cell Biology.