GLUT1 GLUCOSE-TRANSPORTER - DIFFERENTIAL GENE-TRANSCRIPTION AND MESSENGER-RNA BINDING TO CYTOSOLIC AND POLYSOME PROTEINS IN BRAIN AND PERIPHERAL-TISSUES

The ratio of GLUT1 mRNA to actin mRNA in brain was 6- to 13- fold grea ter than the corresponding ratio in spleen, lung, testis, heart, and s keletal muscle in the rat. However, the ratio of GLUT1 transcription r ate to actin transcription rate is comparable in brain and the five ot her organs. Organ extracts were fractionated into cytosol and polysome s, and ultraviolet light cross-linking studies were performed with the se proteins and P-32-labeled GLUT1 mRNA containing the 3'-untranslated region (UTR) generated from transcription plasmids. The cytosol of br ain, lung, spleen, C6 glioma cells in tissue culture, and freshly isol ated bovine brain capillaries express a pair of 95 kDa and 74 kDa prot eins, designated collectively as p88, and the polysome fraction of bra in, testis, or C6 glioma cells express a 44-kDa protein, designated p4 4. In a middle cerebral artery occlusion model, brain cytosol p88 was up-regulated and p44 was down-regulated. These findings are consistent with the hypothesis that GLUT1 gene expression is subject to regulati on at the post-transcriptional level. (C) 1998 Elsevier Science B.V. A ll rights reserved.