Insulin-stimulated translocation of glucose transporters in the isolated rat adipose cells: Characterization of subcellular fractions

• Published in: Biochimica et biophysica acta Vol. 763; no. 4; pp. 393 - 407
• Main Authors: Simpson, Ian A., Yver, Dena R., Hissin, Paul J., Wardzala, Lawrence J., Karnieli, Eddy, Salans, Lester B., Cushman, Samuel W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 19.12.1983; Elsevier; North-Holland
• Subjects: Adipose Tissue - drug effects; Adipose Tissue - metabolism; Adipose Tissue - ultrastructure; Animals; Biological and medical sciences; Biological Transport - drug effects; Carrier Proteins - metabolism; Cell Membrane - metabolism; Endocrine pancreas; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; Glucose transporter distribution; Hormones. Régulation; Insulin; Insulin - pharmacology; Male; Microscopy, Electron; Microsomes - metabolism; Microsomes - ultrastructure; Monosaccharide Transport Proteins; Rat adipose tissue; Rats; Rats, Inbred Strains; Subcellular fractionation; Subcellular Fractions - metabolism; Subcellular Fractions - ultrastructure; Vertebrates: endocrinology; Subcellular fractionation; SDS; Glucose transporter distribution; galactosyltransferase; Hepes; Insulin; Rat adipose tissue; sialyltransferase; Adipocyte; Protein hormone; Vertebrata; Mammalia; Cell fraction; Rat; Biological transport; Rodentia; Glucose; Metabolism
• ISSN: 0167-4889; 0006-3002; 1879-2596; 1878-2434
• DOI: 10.1016/0167-4889(83)90101-5

Insulin stimulates glucose transport in rat adipose cells through the translocation of glucose transporters from an intracellular pool to the plasma membrane. A detailed characterization of the morphology, protein composition and marker enzyme content of subcellular fractions of these cells, prepared by differential ultracentrifugation, and of the distribution of glucose transporters among these fractions is now described. Glucose transporters were measured using specific d-glucose-inhibitable [ 3H]cytochalasin B binding. In the basal state, roughly 90% of the cells' glucose transporters are associated with a low-density microsomal, Golgi marker enzyme-enriched membrane fraction. However, the distributions of glucose transporters and Golgi marker enzyme activities over all fractions are clearly distinct. Incubation of intact cells with insulin increases the number of glucose transporters in the plasma membrane fraction 4–5-fold and correspondingly decreases the intracellular pool, without influencing any other characteristics of the subcellular fractions examined or the estimated total number of glucose transporters (3.7·10 6/cell). Insulin does not influence the K d of the glucose transporters in the plasma membrane fraction for cytochalasin B binding (98 nM), but lowers that in the intracellular pool (from 141 to 93 nM). The calculated turnover numbers of the glucose transporters in the plasma membrane vesicles from basal and insulin-stimulated cells are similar (15·10 3 mol of glucose/min per mol of transporters at 37°C), whereas insulin appears to increase the turnover number in the plasma membrane of intact cells roughly 4-fold. These results suggest that (1) the intracellular pool of glucose transporters may comprise a specialized membrane species, (2) intracellular glucose transporters may undergo conformational changes during their cycling to the plasma membrane in response to insulin, and (3) the translocation of glucose transporters may represent only one component in the mechanism through which insulin regulates glucose transport in the intact cell.