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 mol.116.104521
DO 10.1124/mol.116.104521
A1 Chakravarthi Chintalapati
A1 Thorsten Keller
A1 Thomas D Mueller
A1 Valentin Gorboulev
A1 Nadine Schaefer
A1 Ilona Zilkowski
A1 Maike Veyhl-Wichmann
A1 Dietmar Geiger
A1 Juergen Groll
A1 Hermann Koepsell
YR 2016
UL http://molpharm.aspetjournals.org/content/early/2016/08/23/mol.116.104521.abstract
AB Na+-D-glucose cotransporter SGLT1 is rate-limiting for glucose absorption in small intestine. Shortly after intake of glucose-rich food SGLT1 abundance in the luminal membrane of small intestine is increased. This upregulation occurs via glucose-induced acceleration of the release of SGLT1-containing vesicles from 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 the concentrative nucleoside transporter CNT1. 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 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 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 biomedical important role of ODC1 in regulation of glucose homeostasis.