title: Insulin induces chloroquine-sensitive recycling of insulin-like growth factor II receptors but not of glucose transporters in rat adipocytes.
abstract: Incubation of insulin-treated rat adipocytes with chloroquine, in a time- and concentration-dependent manner, was observed to inhibit the insulin-stimulated increase in insulin-like growth factor II (IGF-II) binding activity, whereas no significant change in IGF-II binding was observed in the absence of insulin. The incremental increase of insulin-stimulated IGF-II binding was inhibited 50% by 0.2 mM chloroquine within 15 min and was nearly completely abolished by 60 min. Interestingly, IGF-II binding was never observed to decrease below the binding value in cells without insulin treatment even when incubation was extended to 180 min. Scatchard analysis of IGF-II binding as well as the specific binding of an anti-IGF-II receptor antibody demonstrated that the loss of IGF-II binding in the insulin-stimulated chloroquine-treated adipocytes was due to a decrease in the number of cell-surface IGF-II receptors, whereas the total number of cellular IGF-II receptors was unaltered. The effect of chloroquine was observed to be reversible, temperature-dependent, and sensitive to the metabolic poison KCN. Furthermore, NH4Cl was also observed to inhibit insulin-stimulated increase in IGF-II binding. In contrast, chloroquine or NH4Cl did not inhibit the basal or insulin-stimulated glucose transport activity. Photoaffinity labeling of the glucose transporter with [3H]cytochalasin B also demonstrated that the basal and insulin-stimulated subcellular distribution of the glucose transporters was unaltered by chloroquine treatment. These results suggest that 1) insulin induces a constitutive, acidotropic agent-sensitive recycling of IGF-II receptor and 2) the glucose transporter and IGF-II receptor do not share the same insulin-regulated intracellular trafficking pathways.
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000345:Affinity Labels / Q000378:metabolism; D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D002738:Chloroquine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D010777:Photochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013997:Time Factors
chemical_list: D000345:Affinity Labels; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D017451:Receptors, Somatomedin; D000641:Ammonia; D002738:Chloroquine; D011972:Receptor, Insulin