Localizing glucose transport proteins: active investigation of passive carriers.

glucose transporter: a basolateral protein in hepatocytes and intestine and kidney cells. ABSTRACT The " liver " isoform of the facilitated diffusion glucose transporter is expressed predominantly in liver, intestine, kidney, and pancreatic islet p-cells. The apparent molecular mass of the transporter in liver, kidney, and intestine is different, as detected by Western blot analysis of membrane proteins using antipeptide antibodies. However, as assessed by Northern blot analysis and molecular cloning, the same mRNA is expressed in these tissues, indicating that there are tissue-specific posttranslational modifications of the same transporter polypeptide. As determined by immunofluorescence analysis on frozen tissue sections, the liver glucose transporter is present on the sinusoidal membrane of hepatocytes, on the basolateral membrane of fully differentiated ab-sorptive intestine epithelial cells, and on the baso-lateral membrane of proximal tubule cells of the kidney nephron. This localization is consistent with the involvement of the liver glucose transporter in several key steps of glucose metabolism: glucose uptake and release by the liver and absorption or reabsorption by epithelial cells of the intestine and kidney, respectively. Thorens B, Lodish HF, Brown D. Differential local-ization of two glucose transporter iso-forms in rat kidney. ABSTRACT The localization of two glucose transporter isoforms was mapped in the rat kidney: the high-Michaelis