Molecular cloning of the bovine blood-brain barrier glucose transporter cDNA and demonstration of phylogenetic conservation of the 5'-untranslated region.

The brain-type glucose transporter (GLUT-1) is a blood-brain barrier (BBB)-specific gene. The isolation of BBB-specific genes from total brain cDNA libraries is difficult because the brain capillary endothelium, which makes up the BBB in vivo, constitutes <0.2% of brain volume. Therefore, the present studies describe the preparation of a bovine brain capillary cDNA library in the lambdagt11 vector and the cloning of the BBB GLUT-1 cDNA. The cDNA sequenced was full length, as confirmed by primer extension analysis. The 5'-untranslated region (UTR) of the bovine GLUT-1 was 67 and 75% homologous with 5'-UTR sequences of the rabbit and human GLUT-1 through nucleotide overlaps of 116 and 159, respectively. A unique proline-rich sequence near the N-terminus of the bovine GLUT-1 was not found in other species and this correlated with marked immunoreactivity of the bovine, but not the human or rat, BBB GLUT-1 protein with an antiserum directed against the 15 amino acids at the N-terminus. In conclusion, these studies describe the cloning of the GLUT-1 cDNA from a BBB cDNA library. The extensive phylogenetic conservation of the 5'-UTR suggests the GLUT-1 gene may be subject to translational control in the regulation of BBB glucose transport.