title: Expression of GLUT8 in mouse intestine: identification of alternative spliced variants.
abstract: GLUT8 is a facilitative glucose transporter composed of 10 exons coding for a 477 amino acids protein. It is mainly expressed in the testis, but it has also been studied in a number of tissues such as brain, adipose tissue, and liver. In this work, we have characterized the expression of GLUT8 in the small and large intestine under normal physiological conditions. Protein assay revealed low GLUT8 protein levels in the intestine compared to the testis, with higher levels in the colon than in the small intestine. Immunohistochemistry studies showed an intracellular localization of GLUT8 in enterocytes and colonocytes with a supranuclear distribution next to the apical membrane. GLUT8 immunoreactivity was also detected in the crypt cells. Interestingly, we have identified three additional transcriptional variants in mouse intestine (mGLUT-SP1, mGLUT8-SP2, and mGLUT8-SP3) produced by the deletion of one, two, and four exons, respectively, whereas only the entire mRNA was detected in the testis. Expression of these alternative variants did not have an effect on glucose consumption in 3T3-L1 cells. Although the specific function of GLUT8 in intestine remains unclear, the alternative splicing of GLUT8 could reflect a mechanism for the regulation of the gene expression in a tissue-specific manner by targeting GLUT8 mRNA for nonsense-mediated decay.
authors.affiliation: Department of Physiology, Pharmacology and Toxicology, Experimental Sciences and Health Faculty, University CEU - Cardenal Herrera, E-46113 Moncada, Valencia, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Romero
authors.forename: Olga
authors.initials: O
authors.lastname: Gomez
authors.forename: Jose
authors.initials: J
authors.lastname: Terrado
authors.forename: Jose E
authors.initials: JE
authors.lastname: Mesonero
mesh_terms: D041721:3T3-L1 Cells; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D005947:Glucose / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000033:anatomy & histology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013737:Testis / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D020033:Protein Isoforms; C498628:Slc2a8 protein, mouse; D005947:Glucose