Erythroid glucose transporters.

PURPOSE OF REVIEW

Animals are heterotrophic and use sugar as their principal source of carbon. Every cell possesses at least one hexose transport system and of all cells, human erythrocytes express the highest level of the facilitative glucose transporter 1 (GLUT1). On the basis of human data, it was assumed that all mammalian erythrocytes express GLUT1 and that this transporter functions similarly in red cells of different species.

RECENT FINDINGS

Analyses of erythrocytes from diverse mammalian species showed that GLUT1 is restricted to those few mammals who are unable to synthesize ascorbic acid from glucose comprising higher primates, guinea pigs, and fruit bats. In humans, erythroid differentiation results in a dramatic GLUT1-mediated increase in the transport of an oxidized form of vitamin C, L-dehydroascorbic acid. This preferential L-dehydroascorbic acid uptake is regulated by the association of GLUT1 with stomatin, an integral erythrocyte membrane protein. In species that produce ascorbic acid, erythroid GLUT1 expression appears to be limited to the fetal and neonatal period. In the case of murine erythrocytes, glucose transport function is thereafter achieved by GLUT4, a GLUT originally characterized by its sensitivity to insulin.

SUMMARY

Recent research has shown that erythrocyte expression of GLUT-type transporters varies between mammalian species and that their functions in this context can differ. These data identify new arrangements of GLUT members in red cell metabolism.