Polarized distribution of glucose transporter isoforms in Caco-2 cells.

Abstract

We have examined the expression and cellular location offacilitated glucose transporter proteins (GLUT1, -3, and -5) in a human colonic epithelial cell line (Caco-2) by using peptide-specific antibodies. A differential cellular distribution of these transporters was observed in differentiated (>14 days postconfluence) Caco-2 cells by immunofluorescence and immunoelectron microscopy. GLUTi was localized primarily to the basolateral membrane, whereas GLUT3 was predominantly localized to the apical membrane. GLUTS, which was detected in only =40% offully differentiated Caco-2 cells, was found primarily in the apical membrane but was also present in both basolateral and intracellular membranes. A Na+-independent glucose transport system in the apical membrane of Caco-2 cells has been described previously [Blais, A., Bissonnette, A. & Berteloot, A. (1987) (7), the insulin-regulated movement of GLUT4 from intracellular tubulo-vesicles to the cell surface (8), and the targeting of GLUT2 to the basolateral membrane in kidney and intestinal epithelial cells (9). By using GLUT1/GLUT4 chimeric proteins, it has recently been shown that the amino-terminal 19 amino acids of GLUT4 are both necessary and sufficient for intracellular sequestration (10).The purpose of the present studies was to examine the targeting of various glucose transporter isoforms in epithelial cells in order to establish a system that would enable a molecular dissection of polarized sorting of membrane proteins. Previous studies of glucose transport kinetics in a human colonic adenocarcinoma cell line (Caco-2) have indicated the presence of a facilitated transport system at the apical and basolateral surfaces (11). Using isoform-specific antibodies, we show in these studies that Caco-2 cells express high levels of GLUT1, GLUT3, and GLUT5. Importantly, each of these isoforms displays a unique subcellular distri- 7556The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

The Human AC133 Hematopoietic Stem Cell Antigen Is also Expressed in Epithelial Cells and Targeted to Plasma Membrane Protrusions

“…4, J-L). Mosaic expression of the AC133 antigen in postconfluent Caco-2 cells is reminiscent of that reported for several brush-border hydrolases (19,20) and transporters (21). The intensity of immunostaining for the AC133 antigen at the apical membrane was variable (compare Fig.…”

Streptozotocin diabetes and the expression of GLUT1 at the brush border and basolateral membranes of intestinal enterocytes

“…The effects of diabetes on enterocyte expression of GLUT1 have not previously been studied, presumably because of the reported absence of this protein in enterocytes from non-diabetic animals [8]. GLUT1 is, however, expressed in Caco-2 cells, a colonic cell line which displays enterocyte-like properties [7].…”

“…Although the protein is found in certain transporting cells e.g. renal proximal tubule and Caco-2 cells [6,7], there is, to date, no evidence for its expression in normal small intestinal epithelium [8]. In the present study we have used confocal immunofluorescence microscopy of rat jejunum, together with Western blotting of BBM and BLM prepared from intestinal mucosa, in order to examine the normal enterocyte distribution of *Corresponding author.…”

Hyperglycaemia-induced subcellular redistribution of GLUT1 glucose transporters in cultured human term placental trophoblast cells

“…The precise molecular basis of such isoform-specific intracellular sorting remains to be clarified but, apart from one study [46], there is now considerable agreement about a recruitment of GLUT1 to the cell surface under basal conditions in a number of cell types expressing it [20, 47±49]. Differential targeting information could reside in particular in the amino acid sequence of the four unique hydrophilic domains which display the highest degree of sequence heterogeneity among the GLUT family [21]. Moreover, specific post-translational modification of the molecules or interaction of the transporters with cytoskeletal elements could account for the distinct subcellular localisation of various glucose carriers [50].…”

“…This binding is saturable and competitively inhibited by peptide 480±492 [19]. The antiserum cross-reacts with the HepG2 glucose transporter [20] as well as with GLUT1 in Caco-2 cells [21].…”