ArticleThe Journal of physiology2005
Determination of transport stoichiometry for two cation-coupled myo-inositol cotransporters: SMIT2 and HMIT.
Article in The Journal of physiology, 2005. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 23 papers.
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Who cites it
23 citing papers in PubMed, 41 citations in OpenAlex.
- Effects of myo-inositol plus alpha-lactalbumin in myo-inositol-resistant PCOS women.Journal of ovarian research · 2018Trial
- The SLC-ome of membrane transport: from molecular discovery to physiology and clinical applications.Physiological reviews · 2026Review
- Metabolism of inositol derivatives by the gut microbiome.Gut microbes · 2025Review
- Novel insights into D-Pinitol based therapies: a link between tau hyperphosphorylation and insulin resistance.Neural regeneration research · 2024Review
- Myo-inositol for insulin resistance, metabolic syndrome, polycystic ovary syndrome and gestational diabetes.Open heart · 2022Article
- The Biomedical Uses of Inositols: A Nutraceutical Approach to Metabolic Dysfunction in Aging and Neurodegenerative Diseases.Biomedicines · 2020Review
- Inositols and metabolic disorders: From farm to bedside.Journal of traditional and complementary medicine · 2020Review
- Inositols in Insulin Signaling and Glucose Metabolism.International journal of endocrinology · 2018Review
- Nutritional and Acquired Deficiencies in Inositol Bioavailability. Correlations with Metabolic Disorders.International journal of molecular sciences · 2017Review
- Polycystic Ovary Syndrome: Insights into the Therapeutic Approach with Inositols.Frontiers in pharmacology · 2017Review
- The "Other" Inositols and Their Phosphates: Synthesis, Biology, and Medicine (with Recent Advances in myo-Inositol Chemistry).Angewandte Chemie (International ed. in English) · 2016Review
- The transport mechanism of the human sodium/myo-inositol transporter 2 (SMIT2/SGLT6), a member of the LeuT structural family.American journal of physiology. Cell physiology · 2014Article
- KCNQ1, KCNE2, and Na+-coupled solute transporters form reciprocally regulating complexes that affect neuronal excitability.Science signaling · 2014Article
- The Concise Guide to PHARMACOLOGY 2013/14: transporters.British journal of pharmacology · 2013Article
- The structural pathway for water permeation through sodium-glucose cotransporters.Biophysical journal · 2011Article
- Targeted metabolomic analyses of cellular models of pelizaeus-merzbacher disease reveal plasmalogen and myo-inositol solute carrier dysfunction.Lipids in health and disease · 2011Article
- Determination of the Na(+)/glucose cotransporter (SGLT1) turnover rate using the ion-trap technique.Biophysical journal · 2011Article
- Article
- The actual ionic nature of the leak current through the Na+/glucose cotransporter SGLT1.Biophysical journal · 2010Article
- Human sodium/inositol cotransporter 2 (SMIT2) transports inositols but not glucose in L6 cells.Archives of biochemistry and biophysics · 2009Article
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Authors and funding
3 authors at 2 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Three different mammalian myo-inositol cotransporters are currently known; two are Na+-coupled (SMIT1 and SMIT2) and one is proton-coupled (HMIT). Although their transport stoichiometries have not been directly determined, significant cooperativities in the Na+ activation of SMIT1 and SMIT2 suggest that more than one Na+ ion drives the transport of each myo-inositol. The two techniques used here to determine transport stoichiometry take advantage of the electrogenicity of both SMIT2 and HMIT expressed in Xenopus oocytes. The first method compares the measurement of charge transferred into voltage-clamped oocytes with the simultaneous uptake of radiolabelled substrate. The second approach uses high accuracy volume measurements to determine the transport-dependent osmolyte uptake and compares it to the amount of charge transported. This method was calibrated using a potassium channel (ROMK2) and was validated with the Na+/glucose cotransporter SGLT1, which has a known stoichiometry of 2 : 1. Volume measurements indicated a stoichiometric ratio of 1.78 +/- 0.27 ion per alpha-methyl-glucose (alphaMG) for SGLT1 whereas the radiotracer uptake method indicated 2.14 +/- 0.05. The two methods yielded a SMIT2 stoichiometry measurement of 1.75 +/- 0.30 and 1.82 +/- 0.10, both in agreement with a 2 Na+:1 myo-inositol stoichiometry. For HMIT, the flux ratio was 1.02 +/- 0.04 charge per myo-inositol, but the volumetric method suggested 0.67 +/- 0.05 charge per myo-inositol molecule. This last value is presumed to be an underestimate of the true stoichiometry of one proton for one myo-inositol molecule due to some proton exchange for osmotically active species. This hypothesis was confirmed by using SGLT1 as a proton-driven glucose cotransporter. In conclusion, despite the inherent difficulty in estimating the osmotic effect of a proton influx, the volumetric method was found valuable as it has the unique capacity of detecting unidentified transported substrates.
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