Localization of transferrin receptors and insulin-like growth factor II receptors in vesicles from 3T3-L1 adipocytes that contain intracellular glucose transporters.

Abstract

Abstract. Transferrin receptors in detergent extracts of subcellular membrane fractions prepared from 3T3-L1 adipocytes were measured by a binding assay. There was a small but significant increase (1.2-fold) in the amount of receptor in a crude plasma membrane fraction and a 40% decrease in the number of transferrin receptors in microsomal membranes prepared from insulin-treated cells, when compared with corresponding fractions from control cells. Intracellular vesicles containing insulin-responsive glucose transporters (GT) have been isolated by immunoadsorption from the microsomal fraction (Biber, J. W., and G. E. Lienhard. 1986. J. Biol. Chem. 261:16180-16184). All of the transferrin receptors in this fraction were localized in these vesicles; however, because the GT vesicles contain '~30-fold fewer transferrin receptors than GT, on the average only one vesicle in three contains a transferrin receptor.The binding of ~25I-pentamannose 6-phosphate BSA to 3T3-L1 adipocytes at 4°C was used to monitor surface insulin-like growth factor II (IGF-II)/mannose 6-phosphate receptors. Exposure of cells to insulin at 37°C for 5 min resulted in a 2.5-4.5-fold increase in surface receptors. There was a corresponding 20% decrease in the amount of IGF-II receptors in the microsomal membranes prepared from insulin-treated cells, as assayed by immunoblotting. Moreover, the IGF-II receptors and GT were located in the same intracellular vesicles, since antibodies to the carboxyterminal peptide of either protein immunoadsorbed vesicles containing 70-95 % of both proteins initially present in the microsomal fraction. In conjunction with other studies, these results indicate that in 3T3-L1 adipocytes, three membrane proteins (the GT, the transferrin receptor, and the IGF-II receptor) respond similarly to insulin, by redistributing to the surface from intracellular compartment(s) in which they are colocalized.

Compartment ablation analysis of the insulin-responsive glucose transporter (GLUT4) in 3T3-L1 adipocytes

“…Moreover, Tanner and Lienhard [7] showed that, at least in adipocytes, GLUT1, TfR and M6PR are colocalized in an intracellular vesicle population. It is now well established that these membrane proteins recycle between an intracellular pool and the plasma membrane, and that this recycling involves the endosomal system (for a review, see [9]).…”

“…Numerous endosomal membrane proteins, including the mannose-6-phosphate receptor (M6PR) [5], the transferrin receptor (TfR) [6,7], GLUT1 [8] and the α2-macroglobulin receptor also translocate to the plasma membrane upon insulin stimulation in adipocytes. Moreover, Tanner and Lienhard [7] showed that, at least in adipocytes, GLUT1, TfR and M6PR are colocalized in an intracellular vesicle population.…”

“…TfRs located at the cell surface rapidly exchange with an intracellular pool of receptors which comprises 50-70 % of the total receptor complement in adipocytes [6,7]. Horseradish peroxidase (HRP)-conjugated transferrin (Tf-HRP) binds specifically to the TfR and its recycling characteristics are identical to those of unconjugated transferrin [18].…”

Relationship between free iron and glycated hemoglobin in uncontrolled type 2 diabetes patients associated with complications

“…Insulin influences the iron uptake and storage by increasing the cell surface transferrin receptors (1), reciprocally iron influences the insulin activity by interfering with glucose uptake and utilization (2). Iron causes hyperinsulinaemia by decreasing the insulin uptake and metabolism by hepatocytes (3).…”

Sedimentation and immunological analyses of GLUT4 and α2‐Na,K‐ATPase subunit‐containing vesicles from rat skeletal muscle: evidence for segregation

“…This observation may signify that these proteins are colocalized in a single intracellular pool enabling them to be recruited to the PM simultaneously upon insulin stimulation. Such a proposition is not without precedent given that other proteins, such as the transferrin receptor and the mannose 6-phosphate receptor, whose cellular distribution is also affected by insulin, have been colocalized with intracellular GLUT4 in 3T3-L1 adipocytes [13]. In an attempt to address this question and gain further insights into the nature of the intracellular pools containing the insulin-senstive GLUT4 transporter and the subunits of the Na,K-ATPase we have, in this investigation, studied the sedimentation and immunological characteristics of intracellular membranes containing these proteins.…”