Insulin-responsive glucose transporters are concentrated in a cell surface-derived membrane fraction of 3T3-L1 adipocytes.
The recently proposed mechanistic concept of a receptor-regulated entrance compartment for hexose transport formed by microvilli on 3T3-L1 adipocytes predicted a preferential localization of glucose transporters in these structures. The cytochalasin B-binding technique was used to determine in basal and insulin-stimulated cells the distribution of glucose transporters between plasma membranes, low density microsomes (LDM) and two cell surface-derived membrane fractions prepared by a hydrodynamic shearing technique. The shearing procedure applied prior to homogenization yielded a low density surface-derived vesicle (LDSV) fraction which contained nearly 60% of the cellular glucose transporters and the total insulin-sensitive transporter pool. The rest of the glucose transporter population was localized within the plasma membrane (5%) and the LDM fraction (37%). Pretreatment of the cells with insulin (20 mU/ml for 10 min) reduced the transporter content of the LDSV fraction by 40% and increased that of the plasma membrane fraction 4-fold. The transporter containing LDSV fraction was clearly differentiated from the LDM fraction by its low specific galactosyltransferase activity and its insulin-sensitivity. Scanning electron microscopy revealed that the LDSV fraction contained a rather uniform population of spherical vesicles of 100-200 nm in diameter.
Lange
K
K
Institut für Pharmakologie, Freie Universität Berlin, FRG.
Brandt
U
U
D000273:Adipose Tissue / Q000032:analysis* / Q000187:drug effects / Q000648:ultrastructure; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis*; D002498:Centrifugation; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003571:Cytochalasin B / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D008855:Microscopy, Electron, Scanning; D008861:Microsomes / Q000032:analysis; D008871:Microvilli / Q000032:analysis; D009004:Monosaccharide Transport Proteins / Q000032:analysis* / Q000378:metabolism
D007328:Insulin; D009004:Monosaccharide Transport Proteins; D003571:Cytochalasin B