GLUT8

GLUT8 is the eighth member of glucose transporter superfamily.

It is characterized by the presence of a dileucine in its N-terminal intracellular domain, which is involved in its retention in still to characterize intracellular compartments.

Molecular cloning
GLUT8, originally named GLUTX1, was cloned almost simultaneously by two different groups.

Contrary to GLUT4, GLUT8 (previously known as GLUTX1) is not insulin-sensitive. In other words, insulin does not promote GLUT8 translocation to the cell surface in neurons as well as in transfected cell lines.

GLUT8 is expressed mostly in neurons and testis, although expression in most other tissues has also been shown at lower levels.

GLUT8, when expressed in Xenopus oocytes, mediates glucose uptake with high affinity. Other hexoses are not good substrates of the transporter. Whether the transporter actually mediates glucose uptake in vivo in the brain has not been evaluated yet.

Mice devoid of both copies of the SLC2A8 gene are viable and do not show any obvious phenotype.

Subcellular localization
Where in the cell GLUT8 is localized in not yet clear. Most GLUT8 is not present at the cell surface. Some co-localization with both the endoplasmic reticulum and late endosomes/lysosomes has been published.

When the N-terminal di-leucine motif is mutated into a di-alanine motif, GLUT8 is located mostly at the cell surface in Xenopus oocytes and mammalian cells such as HEK293 cells and differentiated PC12 cells.