Acute Stimulation of GLUT1 Cell Surface Localization in Blood‐Brain Barrier Endothelial Cells

Abstract

The human brain relies on constant uptake of glucose from the blood stream for its energy needs. However, the blood‐brain barrier (BBB) prevents simple diffusion of glucose and other substrates from circulation into the brain interstitial fluid. Thus, glucose must be transported across the BBB endothelial cells (ECs) by the glucose transporter, GLUT1. Misregulation of BBB GLUT1 expression or function results in severe cognitive and developmental disorders. Until recently, BBB GLUT1 was believed to be predominantly at the cell surface, and that increased GLUT1‐mediated glucose transport was simply achieved by incorporation of newly synthesized GLUT1 into the plasma membrane. However, recent data from our lab suggest that AMP kinase (AMPK) controls GLUT1 localization between intracellular and cell surface membranes. To understand how AMPK regulate GLUT1 trafficking in BBB ECs, we are using a reversible cell surface biotinylation technique to study GLUT1 kinetics in the presence or absence of AMPK activation. From our preliminary data in basal, murine brain endothelial (bEnd.3) cells we obtain a first order rate constant of exocytosis (kex) and endocytosis (ken) of 0.091min‐1 and 0.436min‐1 respectively for GLUT1 trafficking. Next, we will determine if AMPK stimulates GLUT1 kex or inhibits GLUT1 ken. This will aid in identifying downstream signaling partners in AMPK‐regulated GLUT1 trafficking. Finally, we will test whether signals that couple neuronal activation to increased BBB glucose transport, act via the AMPK pathway. Findings from this study will provide fundamental insights into cerebral glucose transporter misregulation in diseases and may reveal mechanisms for pharmacologic manipulation of the BBB permeability.