Jejunal/kidney glucose transporter isoform (Glut-5) is expressed in the human blood-brain barrier.
The recently cloned Glut-5, glucose transporter isoform, is expressed in human jejunum and kidney. Employing previously characterized polyclonal antibodies directed towards the C-terminus region of the derived human Glut-5 peptide and Western blot analysis, a 50-55 kilodalton Glut-5 protein was detected in adult human brain homogenates. The amount of Glut-5 protein in brain was 4-fold lower when compared to the levels in adult kidney. Immunohistochemical analysis using cerebral and cerebellar sections demonstrated Glut-5 immunoreactivity in only some of the Glut-1 and factor VIII-positive brain microvascular endothelial cells, the intravascular red and white blood cells being negative. This selective localization pattern was confirmed by the 5-fold enrichment of Glut-5 vs. a 20-fold enrichment of Glut-1 in an isolated human cerebral cortical microvascular preparation, when compared to whole cerebral homogenates. We conclude that Glut-5 is localized in the endothelial cells of human brain microvasculature. Unlike other fructose using tissues, where Glut-5 may subserve the role of a fructose carrier, in brain where fructose is not used as a substrate, Glut-5 may transport glucose alone. This role of Glut-5 in conjunction with the previously characterized brain endothelial Glut-1 and Glut-3 needs further elucidation.
Mantych
G J
GJ
Division of Neonatology, St. Louis University School of Medicine, Missouri.
James
D E
DE
Devaskar
S U
SU
D001812:Blood-Brain Barrier; D015153:Blotting, Western; D001923:Brain Chemistry; D004730:Endothelium, Vascular / Q000737:chemistry; D051296:Glucose Transporter Type 5; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007583:Jejunum / Q000737:chemistry*; D007668:Kidney / Q000737:chemistry*; D008833:Microcirculation / Q000737:chemistry; D009004:Monosaccharide Transport Proteins / Q000032:analysis*
D051296:Glucose Transporter Type 5; D009004:Monosaccharide Transport Proteins