title: Mouse glucose transporter 9 splice variants are expressed in adult liver and kidney and are up-regulated in diabetes.
abstract: A novel glucose transporter (GLUT), mouse GLUT9 (mGLUT9), was recently cloned from mouse 7-d embryonic cDNA. Several splice variants of mGLUT9 were described, two of which were cloned (mGLUT9a and mGLUT9a Delta 209-316). This study describes the cloning and characterization of another splice variant, mGLUT9b. Cloned from adult liver, mGLUT9b is identical to mGLUT9a except at the amino terminus. Based on analysis of the genomic structure, the different amino termini result from alternative transcriptional/translational start sites. Expression and localization of these two mGLUT9 splice variants were examined in control and diabetic adult mouse tissues and in cell lines. RT-PCR analysis demonstrated expression of mGLUT9a in several tissues whereas mGLUT9b was observed primarily in liver and kidney. Using a mGLUT9-specific antibody, Western blot analysis of total membrane fractions from liver and kidney detected a single, wide band, migrating at approximately 55 kDa. This band shifted to a lower molecular mass when deglycosylated with peptide-N-glycosidase F. Both forms were present in liver and kidney. Immunohistochemical localization demonstrated basolateral distribution of mGLUT9 in liver hepatocytes and the expression of mGLUT9 in specific tubules in the outer cortex of the kidney. To investigate the alternative amino termini, mGLUT9a and mGLUT9b were overexpressed in kidney epithelium cell lines. Subcellular fractions localized both forms to the plasma membrane. Immunofluorescent staining of polarized Madin Darby canine kidney cells overexpressing mGLUT9 depicted a basolateral distribution for both splice variants. Finally, mGLUT9 protein expression was significantly increased in the kidney and liver from streptozotocin-induced diabetic mice compared with nondiabetic animals.
authors.affiliation: Washington University School of Medicine, Department of Obstetrics/Gynelcology, Box 8064, St. Louis, Missouri 63110, USA.
authors.forename: Chithra
authors.initials: C
authors.lastname: Keembiyehetty
authors.forename: Robert
authors.initials: R
authors.lastname: Augustin
authors.forename: Mary O
authors.initials: MO
authors.lastname: Carayannopoulos
authors.forename: Sarah
authors.initials: S
authors.lastname: Steer
authors.forename: Andrei
authors.initials: A
authors.lastname: Manolescu
authors.forename: Chris I
authors.initials: CI
authors.lastname: Cheeseman
authors.forename: Kelle H
authors.initials: KH
authors.lastname: Moley
mesh_terms: D000367:Age Factors; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D005260:Female; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics* / Q000378:metabolism*; D007668:Kidney / Q000502:physiology*; D008099:Liver / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D012016:Reference Values; D015854:Up-Regulation; D014982:Xenopus laevis
chemical_list: D051246:Glucose Transport Proteins, Facilitative; C498775:Slc2a9 protein, mouse