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Am J Physiol Cell Physiol. 2014 May 15;306(10):C910-7. doi: 10.1152/ajpcell.00044.2014. Epub 2014 Mar 5.

Human erythrocytes transport dehydroascorbic acid and sugars using the same transporter complex.

Author information

1
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts.
2
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts anthony.carruthers@umassmed.edu.

Abstract

GLUT1, the primary glucose transport protein in human erythrocytes [red blood cells (RBCs)], also transports oxidized vitamin C [dehydroascorbic acid (DHA)]. A recent study suggests that RBC GLUT1 transports DHA as its primary substrate and that only a subpopulation of GLUT1 transports sugars. This conclusion is based on measurements of cellular glucose and DHA equilibrium spaces, rather than steady-state transport rates. We have characterized RBC transport of DHA and 3-O-methylglucose (3-OMG), a transported, nonmetabolizable sugar. Steady-state 3-OMG and DHA uptake in the absence of intracellular substrate are characterized by similar Vmax (0.16 ± 0.01 and 0.13 ± 0.02 mmol·l(-1)·min(-1), respectively) and apparent Km (1.4 ± 0.2 and 1.6 ± 0.7 mM, respectively). 3-OMG and DHA compete for uptake, with Ki(app) of 0.7 ± 0.4 and 1.1 ± 0.1 mM, respectively. Uptake measurements using RBC inside-out-membrane vesicles demonstrate that 3-OMG and DHA compete at the cytoplasmic surface of the membrane, with Ki(app) of 0.7 ± 0.1 and 0.6 ± 0.1 mM, respectively. Intracellular 3-OMG stimulates unidirectional uptake of 3-OMG and DHA. These findings indicate that DHA and 3-OMG bind at mutually exclusive sites at exo- and endofacial surfaces of GLUT1 and are transported via the same GLUT1 complex.

KEYWORDS:

GLUT1; dehydroascorbic acid transport; erythrocyte; glucose transport

PMID:
24598365
PMCID:
PMC4024712
DOI:
10.1152/ajpcell.00044.2014
[Indexed for MEDLINE]
Free PMC Article

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