epidermal-growth-factor and mannose-6-phosphate

Topics: alpha-Macroglobulins; Animals; Asialoglycoproteins; Diphtheria Toxin; Endocytosis; Epidermal Growth Factor; Growth Substances; Humans; Leukemia; Ligands; Mannosephosphates; Receptors, Cell Surface; Receptors, Transferrin; Toxins, Biological; Transferrin; Tumor Cells, Cultured

Mannose 6-phosphate, insulin like growth factors I and II (IGF I, IGF II), insulin and epidermal growth factor (EGF) induce a 1.5- to 2-fold increase of mannose 6-phosphate binding sites at the cell surface of human skin fibroblasts. The increase is completed within 10-15 min, is dose and temperature dependent, reversible and transient even in the presence of the effectors. It is due to a redistribution of mannose 6-phosphate/IGF II receptors from internal membranes to the cell surface, while the affinity of the receptors is not affected. Combinations of mannose 6-phosphate with IGF I, IGF II or EGF stimulate the redistribution of the receptor to the cell surface in an additive manner, while combinations of the growth factors result in a non-additive stimulation of redistribution. The redistribution is not dependent on extracellular calcium and appears also to be independent of changes of free intracellular calcium. Pre-treatment of fibroblasts with cholera toxin or pertussis toxin increases the number of cell surface receptors 2- and 1.5-fold, respectively. Neither of the toxins affects the redistribution of mannose 6-phosphate/IGF II receptors induced by the growth factors, while both toxins abolish the receptor redistribution induced by mannose 6-phosphate. These results suggest a multiple regulation of the cell surface expression of mannose 6-phosphate/IGF II receptors by Gs- and Gi-like proteins sensitive to cholera toxin and pertussis toxin and by stimulation of mannose 6-phosphate/IGF II, IGF I and EGF receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Calcium; Cells, Cultured; Cyclic AMP; Drug Synergism; Epidermal Growth Factor; GTP-Binding Proteins; Histocytochemistry; Humans; Insulin; Insulin-Like Growth Factor II; Mannosephosphates; Receptor, IGF Type 2; Receptors, Cell Surface; Receptors, Somatomedin; Signal Transduction