Characterization of glucose transporter in cultured human retinal pigment epithelial cells: gene expression and effect of growth factors

Abstract

Purpose: To investigate gene and protein expression of glucose transporter isoforms in cultured human retinal pigment epithelial cells. To investigate growth factor-dependent stimulation of glucose transport and the effect of growth factors on the gene and protein expression in retinal pigment epithelial cells.

Methods: Glucose transport activity was analyzed by [3H]2-deoxyglucose uptake studies. Gene and protein expression of glucose transporter isoforms were analyzed by polymerase chain reaction, Northern blot analysis, and Western blot analysis.

Results: Polymerase chain reaction, nucleotide sequencing, and Southern blot analyses revealed that the retinal pigment epithelial cells express GLUT-1, -3, and -5 genes. Northern and Western blot analysis detected only GLUT-1 transcripts and protein. A 24-hour exposure to fetal bovine serum (15%), basic fibroblast growth factor (50 ng/ml), platelet-derived growth factor (10 ng/ml), epidermal growth factor (50 ng/ml), and insulin-like growth factor-1 (50 ng/ml) significantly stimulated [3H]2-deoxyglucose uptake in cultured human retinal pigment epithelial cells. Western blot analysis showed that serum and platelet-derived growth factor induced an increase of GLUT-1 protein in the membrane preparation in the cells. Serum, fibroblast growth factor, platelet-derived growth factor, and insulin-like growth factor-1 did not increase GLUT-1 gene expression to an appreciable level, as shown by Northern blot analysis.

Conclusion: Cultured human retinal pigment epithelial cells dominantly express GLUT-1 gene and protein with minor expression of GLUT-3 and -5 genes. Fetal bovine serum, fibroblast growth factor, platelet-derived growth factor, epidermal growth factor, and insulin-like growth factor-1 significantly, although modestly, increase glucose transport activity of the cells.