PALMITOYLATION OF THE GLUCOSE-TRANSPORTER IN BLOOD-BRAIN-BARRIER CAPILLARIES

Palmitoylation of GLUT1 was investigated in brain capillaries. The glu cose transporter was shown to be palmitoylated using [H-3]palmitate la beling and immunoprecipitation. The labeling was sensitive to methanol ic KOH or hydroxylamine hydrolysis, indicating the presence of an este r or thioester bond. The released fatty acid was analyzed by reverse-p hase HPLC and was identified as [H-3]palmitate. Specificity of the imm unoprecipitation was assessed by competitive inhibition of anti-GLUT1 binding with a synthetic C-terminal peptide against which the antibody was raised. In vivo studies were performed using capillaries isolated from control rats, streptozotocin-induced diabetic rats and diet-indu ced hyperglycemic rats. Glycemia was increased 2- and 5-fold in the hy perglycemic and diabetic groups, respectively. GLUT1 expression was ev aluated in the three groups by Western blot analysis. A 36% decrease i n GLUT1 expression was observed in the diabetic group, while there was no significant variation in GLUT1 expression in the hyperglycemic gro up. Palmitoylation of GLUT1 was increased in both diet-induced hypergl ycemic and diabetic groups. These results suggest that palmitoylation may be involved in the regulation of glucose transport activity in hyp erglycemia.