title: Protein RS1 (RSC1A1) Downregulates the Exocytotic Pathway of Glucose Transporter SGLT1 at Low Intracellular Glucose via Inhibition of Ornithine Decarboxylase.
abstract: Na+-d-glucose cotransporter 1 (SGLT1) is rate-limiting for glucose absorption in the small intestine. Shortly after intake of glucose-rich food, SGLT1 abundance in the luminal membrane of the small intestine is increased. This upregulation occurs via glucose-induced acceleration of the release of SGLT1-containing vesicles from the trans-Golgi network (TGN), which is regulated by a domain of protein RS1 (RSC1A1) named RS1-Reg. Dependent on phosphorylation, RS1-Reg blocks release of vesicles containing SGLT1 or concentrative nucleoside transporter 1. The hypothesis has been raised that RS1-Reg binds to different receptor proteins at the TGN, which trigger release of vesicles with different transporters. To identify the presumed receptor proteins, two-hybrid screening was performed. Interaction with ornithine decarboxylase 1 (ODC1), the rate-limiting enzyme of polyamine synthesis, was observed and verified by immunoprecipitation. Binding of RS1-Reg mutants to ODC1 was characterized using surface plasmon resonance. Inhibition of ODC1 activity by RS1-Reg mutants and the ODC1 inhibitor difluoromethylornithine (DFMO) was measured in the absence and presence of glucose. In addition, short-term effects of DFMO, RS1-Reg mutants, the ODC1 product putrescine, and/or glucose on SGLT1 expressed in oocytes of Xenopus laevis were investigated. High-affinity binding of RS1-Reg to ODC1 was demonstrated, and evidence for a glucose binding site in ODC1 was provided. Binding of RS1-Reg to ODC1 inhibits the enzymatic activity at low intracellular glucose, which is blunted at high intracellular glucose. The data suggest that generation of putrescine by ODC1 at the TGN stimulates release of SGLT1-containing vesicles. This indicates a biomedically important role of ODC1 in regulation of glucose homeostasis.
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Chakravarthi
authors.initials: C
authors.lastname: Chintalapati
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Thorsten
authors.initials: T
authors.lastname: Keller
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Mueller
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Valentin
authors.initials: V
authors.lastname: Gorboulev
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Nadine
authors.initials: N
authors.lastname: Schäfer
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Ilona
authors.initials: I
authors.lastname: Zilkowski
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Maike
authors.initials: M
authors.lastname: Veyhl-Wichmann
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Dietmar
authors.initials: D
authors.lastname: Geiger
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.).
authors.forename: Jürgen
authors.initials: J
authors.lastname: Groll
authors.affiliation: Institute of Anatomy and Cell Biology (C.C., V.G., M.V.-W., H.K.), and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute (T.K., T.D.M., N.S., D.G., H.K.), University of Würzburg, Würzburg, Germany; and Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Würzburg, Germany (I.Z., J.G.) Hermann@koepsell.de.
authors.forename: Hermann
authors.initials: H
authors.lastname: Koepsell
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D000518:Eflornithine / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005089:Exocytosis / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D042541:Intracellular Space / Q000378:metabolism; D007700:Kinetics; D008757:Methylglucosides / Q000494:pharmacology; D008954:Models, Biological; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D010695:Phlorhizin / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D000072417:Protein Domains; D011994:Recombinant Proteins / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1 / Q000378:metabolism*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014982:Xenopus laevis
chemical_list: D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; C101014:RSC1A1 protein, human; D011994:Recombinant Proteins; D051269:Sodium-Glucose Transporter 1; D010695:Phlorhizin; D009955:Ornithine Decarboxylase; D005947:Glucose; D000518:Eflornithine