RT Journal Article
SR Electronic
T1 Protein RS1 (<em>RSC1A1</em>) Downregulates the Exocytotic Pathway of Glucose Transporter SGLT1 at Low Intracellular Glucose via Inhibition of Ornithine Decarboxylase
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 508
OP 521
DO 10.1124/mol.116.104521
VO 90
IS 5
A1 Chakravarthi Chintalapati
A1 Thorsten Keller
A1 Thomas D. Mueller
A1 Valentin Gorboulev
A1 Nadine Schäfer
A1 Ilona Zilkowski
A1 Maike Veyhl-Wichmann
A1 Dietmar Geiger
A1 Jürgen Groll
A1 Hermann Koepsell
YR 2016
UL http://molpharm.aspetjournals.org/content/90/5/508.abstract
AB 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.