Abstract
cDNAs encoding facilitated-diffusion glucose transporters GULT1, GULT3, GULT4, and GULT5 were introduced into the rat pancreas by in-vivo electroporation method, and their expression and localization in pancreatic acinar cells were examined immunohistochemically. GLUT1 was localized at the basolateral membrane, whereas GLUT3 and GLUT5 were at the apical membrane. Restriction of GLUT3 and GLUT5 to the apical membrane makes a marked contrast to their localization to the entire plasma membrane when expressed in hepatocytes in situ. Such differential localization may be due to differential apical targeting mechanism: direct targeting in acinar cells and indirect transcytotic delivery in hepatocytes in situ. GLUT4 was present in the membrane of zymogen secretory granules in the cytoplasm in acinar cells. This observation suggests that GLUT4 is segregated to the regulated secretory pathway. Expression of glucose transporters in situ is a useful method in analyzing the targeting mechanism of membrane proteins in cells of tissues in situ.
