GLUT8

GLUT8, originally named GLUTX1, was cloned almost simultaneously by two different groups.{{cite journal |vauthors=Ibberson M, Uldry M, Thorens B | title = GLUTX1, a novel mammalian glucose transporter expressed in the central nervous system and insulin-sensitive tissues | journal = J. Biol. Chem. | volume = 275 | issue = 7 | pages = 4607–12 | year = 2000 | pmid = 10671487 | doi = 10.1074/jbc.275.7.4607 | doi-access = free }}{{cite journal |vauthors=Doege H, Schürmann A, Bahrenberg G, Brauers A, Joost HG | title = GLUT8, a novel member of the sugar transport facilitator family with glucose transport activity | journal = J. Biol. Chem. | volume = 275 | issue = 21 | pages = 16275–80 | year = 2000 | pmid = 10821868 | doi = 10.1074/jbc.275.21.16275 | doi-access = free }}

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Contrary to GLUT4, GLUT8 (previously known as GLUTX1) is not insulin-sensitive.{{Citation needed|date=August 2009}} In other words, insulin does not promote GLUT8 translocation to the cell surface in neurons as well as in transfected cell lines.{{Citation needed|date=August 2008}}

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.{{cite journal |vauthors=Widmer M, Uldry M, Thorens B | title = GLUT8 subcellular localization and absence of translocation to the plasma membrane in PC12 cells and hippocampal neurons | journal = Endocrinology | volume = 146 | issue = 11 | pages = 4727–36 | year = 2005 | pmid = 16109784 | doi = 10.1210/en.2005-0668 | doi-access = free }}

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 HEK 293 cells and differentiated PC12 cells.{{Citation needed|date=August 2008}}

GLUT8 function in vivo remains to be defined, despite suggestions that it may play a role in fertility, being expressed at high levels in testes and in the acrosomal part of spermatozoa.{{cite journal |vauthors=Schürmann A, Axer H, Scheepers A, Doege H, Joost HG | title = The glucose transport facilitator GLUT8 is predominantly associated with the acrosomal region of mature spermatozoa | journal = Cell Tissue Res. | volume = 307 | issue = 2 | pages = 237–42 |date=February 2002 | pmid = 11845330 | doi = 10.1007/s00441-001-0499-2 | s2cid = 20138373 }} Furthermore, GLUT8 appears to play an important role in the energy metabolism of sperm cells.{{cite journal |vauthors=Gawlik V, Schmidt S, Scheepers A, Wennemuth G, Augustin R, Aumüller G, Moser M, Al-Hasani H, Kluge R, Joost HG, Schürmann A | title = Targeted disruption of Slc2a8 (GLUT8) reduces motility and mitochondrial potential of spermatozoa | journal = Mol. Membr. Biol. | volume = 25 | issue = 3 | pages = 224–35 |date=April 2008 | pmid = 18428038 | doi = 10.1080/09687680701855405 | pmc = 2557070 }}

GLUT8, when expressed in Xenopus oocytes, mediates glucose uptake with high affinity. Other hexoses are not good substrates of the transporter.

Mice devoid of both copies of the SLC2A8 gene are viable, fertile and do not show any obvious phenotype.{{cite journal |vauthors=Membrez M, Hummler E, Beermann F, Haefliger JA, Savioz R, Pedrazzini T, Thorens B | title = GLUT8 is dispensable for embryonic development but influences hippocampal neurogenesis and heart function | journal = Mol. Cell. Biol. | volume = 26 | issue = 11 | pages = 4268–76 | year = 2006 | pmid = 16705176 | doi = 10.1128/MCB.00081-06 | pmc = 1489108 }} They are not diabetic, showing that GLUT8 is unlikely to play major roles in glucose homeostasis.{{Citation needed|date=August 2008}}

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Category:Membrane proteins

Category:Solute carrier family