Caffeine inhibits glucose transport by binding at the GLUT1 nucleotide-binding site

Glucose transporter 1 (GLUT1) is the primary glucose transport protein of the cardiovascular system and astroglia. A recent study proposes that caffeine uncompetitive inhibition of GLUT1 results from interactions at an exofacial GLUT1 site. Intracellular ATP is also an uncompetitive GLUT1 inhibitor...

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Bibliographic Details
Published in:American Journal of Physiology: Cell Physiology 2015-05, Vol.308 (10), p.C827-C834
Main Authors: Sage, Jay M, Cura, Anthony J, Lloyd, Kenneth P, Carruthers, Anthony
Format: Article
Language:English
Subjects:
3-O-Methylglucose - metabolism
Adenosine triphosphatase
Adenosine Triphosphate - metabolism
Binding Sites
Biological Transport - drug effects
Biological Transport - physiology
Caffeine
Caffeine - pharmacology
Cytochalasin B - metabolism
Erythrocyte Membrane - metabolism
Erythrocytes
Erythrocytes - drug effects
Erythrocytes - metabolism
Glucose
Glucose - metabolism
Glucose Transporter Type 1 - metabolism
Humans
Proteins
Signal Transduction - drug effects
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Summary:Glucose transporter 1 (GLUT1) is the primary glucose transport protein of the cardiovascular system and astroglia. A recent study proposes that caffeine uncompetitive inhibition of GLUT1 results from interactions at an exofacial GLUT1 site. Intracellular ATP is also an uncompetitive GLUT1 inhibitor and shares structural similarities with caffeine, suggesting that caffeine acts at the previously characterized endofacial GLUT1 nucleotide-binding site. We tested this by confirming that caffeine uncompetitively inhibits GLUT1-mediated 3-O-methylglucose uptake in human erythrocytes [Vmax and Km for transport are reduced fourfold; Ki(app) = 3.5 mM caffeine]. ATP and AMP antagonize caffeine inhibition of 3-O-methylglucose uptake in erythrocyte ghosts by increasing Ki(app) for caffeine inhibition of transport from 0.9 ± 0.3 mM in the absence of intracellular nucleotides to 2.6 ± 0.6 and 2.4 ± 0.5 mM in the presence of 5 mM intracellular ATP or AMP, respectively. Extracellular ATP has no effect on sugar uptake or its inhibition by caffeine. Caffeine and ATP displace the fluorescent ATP derivative, trinitrophenyl-ATP, from the GLUT1 nucleotide-binding site, but d-glucose and the transport inhibitor cytochalasin B do not. Caffeine, but not ATP, inhibits cytochalasin B binding to GLUT1. Like ATP, caffeine renders the GLUT1 carboxy-terminus less accessible to peptide-directed antibodies, but cytochalasin B and d-glucose do not. These results suggest that the caffeine-binding site bridges two nonoverlapping GLUT1 endofacial sites-the regulatory, nucleotide-binding site and the cytochalasin B-binding site. Caffeine binding to GLUT1 mimics the action of ATP but not cytochalasin B on sugar transport. Molecular docking studies support this hypothesis.
ISSN:0363-6143
1522-1563
DOI:10.1152/ajpcell.00001.2015