1.Phosphorylation of RS1 (RSC1A1) Steers Inhibition of Different Exocytotic Pathways for Glucose Transporter SGLT1 and Nucleoside Transporter CNT1, and an RS1-Derived Peptide Inhibits Glucose Absorption.
Veyhl-Wichmann M1, Friedrich A1, Vernaleken A1, Singh S1, Kipp H1, Gorboulev V1, Keller T1, Chintalapati C1, Pipkorn R1, Pastor-Anglada M1, Groll J1, Koepsell H2. Mol Pharmacol. 2016 Jan;89(1):118-32. doi: 10.1124/mol.115.101162. Epub 2015 Oct 13.
Cellular uptake adapts rapidly to physiologic demands by changing transporter abundance in the plasma membrane. The human gene RSC1A1 codes for a 67-kDa protein named RS1 that has been shown to induce downregulation of the sodium-D-glucose cotransporter 1 (SGLT1) and of the concentrative nucleoside transporter 1 (CNT1) in the plasma membrane by blocking exocytosis at the Golgi. Injecting RS1 fragments into Xenopus laevis oocytes expressing SGLT1 or CNT1 and measuring the expressed uptake of α-methylglucoside or uridine 1 hour later, we identified a RS1 domain (RS1-Reg) containing multiple predicted phosphorylation sites that is responsible for this post-translational downregulation of SGLT1 and CNT1. Dependent on phosphorylation, RS1-Reg blocks the release of SGLT1-containing vesicles from the Golgi in a glucose-dependent manner or glucose-independent release of CNT1-containing vesicles. We showed that upregulation of SGLT1 in the small intestine after glucose ingestion is promoted by glucose-dependent disinhibition of the RS1-Reg-blocked exocytotic pathway of SGLT1 between meals.
2.Development and application of a fluorescent glucose uptake assay for the high-throughput screening of non-glycoside SGLT2 inhibitors.
Wu SH1, Yao CH1, Hsieh CJ1, Liu YW1, Chao YS1, Song JS2, Lee JC3. Eur J Pharm Sci. 2015 Jul 10;74:40-4. doi: 10.1016/j.ejps.2015.03.011. Epub 2015 Mar 27.
Sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors are of current interest as a treatment for type 2 diabetes. Efforts have been made to discover phlorizin-related glycosides with good SGLT2 inhibitory activity. To increase structural diversity and better understand the role of non-glycoside SGLT2 inhibitors on glycemic control, we initiated a research program to identify non-glycoside hits from high-throughput screening. Here, we report the development of a novel, fluorogenic probe-based glucose uptake system based on a Cu(I)-catalyzed [3+2] cycloaddition. The safer processes and cheaper substances made the developed assay our first priority for large-scale primary screening as compared to the well-known [(14)C]-labeled α-methyl-D-glucopyranoside ([(14)C]-AMG) radioactive assay. This effort culminated in the identification of a benzimidazole, non-glycoside SGLT2 hit with an EC50 value of 0.62 μM by high-throughput screening of 41,000 compounds.
3.2-Deoxy-D-Glucose Is a Potent Inhibitor of Biofilm Growth in Escherichia coli.
Sutrina SL1, Griffith MS2, Lafeuille C3. Microbiology. 2016 Apr 5. doi: 10.1099/mic.0.000290. [Epub ahead of print]
Escherichia coli strain 15 (ATCC 9723), which forms robust biofilms, was grown under optimal biofilm conditions in NaCl-free Luria-Bertani broth (LB*) or in LB* supplemented with one of the non-metabolizable analogues 2-deoxy-D-glucose (2DG), α-methyl-D-mannopyranoside (αMM), or α-methyl-D-glucopyranoside (αMG). Biofilm growth was inhibited by mannose analogue 2DG even at very low concentration in unbuffered medium, and the maximal inhibition was enhanced in the presence of either 100 mM KPO4 or 100 mM MOPS, pH 7.5; in buffered medium, concentrations of 0.02 % (1.2 mM) or more inhibited nearly completely. In contrast, mannose analogue αMM, which should not be able to enter the cells but has been reported to inhibit biofilm growth by binding to FimH, did not exhibit strong inhibition even at concentrations up to 1.8 % (108 mM). The glucose analogue αMG inhibited biofilm growth, but much less strongly than 2DG. None of the analogues inhibited planktonic growth or caused a change in pH of the unbuffered medium.
4.SGLT1 sugar transporter/sensor is required for post-oral glucose appetition.
Sclafani A1, Koepsell H2, Ackroff K3. Am J Physiol Regul Integr Comp Physiol. 2016 Apr 1;310(7):R631-9. doi: 10.1152/ajpregu.00432.2015. Epub 2016 Jan 20.
Recent findings suggest that the intestinal sodium-glucose transporter 1 (SGLT1) glucose transporter and sensor mediates, in part, the appetite-stimulation actions of intragastric (IG) glucose and nonmetabolizable α-methyl-d-glucopyranoside (MDG) infusions in mice. Here, we investigated the role of SGLT1 in sugar conditioning using SGLT1 knockout (KO) and C57BL/6J wild-type (WT) mice. An initial experiment revealed that both KO and WT mice maintained on a very low-carbohydrate diet display normal preferences for saccharin, which was used in the flavored conditioned stimulus (CS) solutions. Inexperiment 2, mice were trained to drink one flavored solution (CS+) paired with an IG MDG infusion and a different flavored solution (CS-) paired with IG water infusion. In contrast to WT mice, KO mice decreased rather than increased the intake of the CS+ during training and failed to prefer the CS+ over the CS- in a choice test. Inexperiment 3, the KO mice also decreased their intake of a CS+ paired with IG glucose and avoided the CS+ in a choice test, unlike WT mice, which preferred the CS+ to CS-.