cDNA cloning and sequence analysis of the glucose transporter from porcine blood-brain barrier

A porcine brain microvessel-derived cDNA library enriched in blood-brain-barrier-specific sequences was constructed by a subtractive cloning procedure. Two cDNA clones from this library were found to encode a glucose transport protein. These clones were used to isolate a nearly full length cDNA from a representative brain microvessel library. Analysis of the amino-acid sequence deduced from the cDNA sequence revealed 97% identity with the human HepG2 glucose carrier. Amino-acid substitutions appear to be clustered in certain regions of the polypeptide. The nucleotide sequences of the 3'-noncoding regions close to the putative polyadenylation sites are highly conserved in glucose transporter mRNAs of different species. The expression of this mRNA has been investigated in various tissues and shown to be decreased in primary cultures of brain microvascular endothelial cells.