The investigation of role and localization of glucose transporters (GLUT) in epidermal keratinocytes

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The transport of glucose across the plasma membrane of mammalian cells represents one of the most important cellular nutrient transport events, since glucose plays a central role in cellular homeostasis and metabolism. It has long been established that the plasma membranes of virtually all mammalian cells processes a transport system for glucose of the facilitative diffusion type ; these glucose transporters allows the movement of glucose across the plasma membrane down its chemical gradient either into or out of cells. These transporters include six types, the GLUT1/erythrocyte, GLUT2/liver, GLUT3/brain, GLUT4/muscle-fat, GLUT5/small intestine, and GLUT7/liver microsome. The extent and significance of GLUT expression in human epidermis is largely unknown. Pig epidermis has been suggested to be an appropriate substitute for the human epidermis because of the close similarity in architecture. This study was undertaken to determine the expression of GLUT in pig epidermal keratinocytes and hyperproliferative keratinocytes. We demonstrate, for the first time, that GLUT1 is highly expressed in normal pig skin and that GLUT1 protein is localized in the basal and the immediately suprabasal layer of the epidermis by immunohistochemistry. In addition, GLUT1 protein (45KD) is detected in pig epidermal extracts by Western-blotting. UVB-induced hyperproliferative epidermis showed enhanced GLUT1 expression. The increase in expression of GLUT1 protein were also determined in tape stripping-induced heperproliferative epidermis. No reactivity for GLUT2-GLUT5 was observed in pig epidermal keratinocytes by immunohistochemistry and Western-blotting. Our data suggested that GLUT1 is highly expressed in the basal layers of pig epidermis and that its expression is modulated by keratinocyte proriferation.