Identification of a mammalian silicon transporter

Sarah Ratcliffe, Ravin Jugdaohsingh, Julien Vivancos, Alan Marron, Rupesh Deshmukh, Jian Feng Ma, Namiki Mitani-Ueno, Jack Robertson, John Wills, Mark V Boekschoten, Michael Muller, Robert C Mawhinney, Stephen D Kinrade, Paul Isenring, Richard R Bélanger, Jonathan Powell

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Silicon (Si) has long been known to play a major physiological and structural role in certain organisms, including diatoms, sponges, and many higher plants, leading to the recent identification of multiple proteins responsible for Si transport in a range of algal and plant species. In mammals, despite several convincing studies suggesting that silicon is an important factor in bone development and connective tissue health, there is a critical lack of understanding about the biochemical pathways that enable Si homeostasis. Here we report the identification of a mammalian efflux Si transporter, namely Slc34a2 (also termed NaPiIIb) a known sodium-phosphate co-transporter, which was upregulated in rat kidney following chronic dietary Si deprivation. Normal rat renal epithelium demonstrated punctate expression of Slc34a2 and when the protein was heterologously expressed in Xenopus laevis oocytes, Si efflux activity (i.e. movement of Si out of cells) was induced and was quantitatively similar to that induced by the known plant Si transporter OsLsi2 in the same expression system. Interestingly, Si efflux appeared saturable over time, but it did not vary as a function of extracellular HPO4 2- or Na+ 43 concentration, suggesting that Slc34a2 harbors a functionally independent transport site for Si operating in the reverse direction to the site for phosphate. Indeed, in rats with dietary Si depletion-induced upregulation of transporter expression, there
was increased urinary phosphate excretion. This is the first evidence of an active Si transport protein in mammals and points towards an important role for Si in vertebrates and explains interactions between dietary phosphate and silicon.
Original languageEnglish
Pages (from-to)C550-C561
Number of pages12
JournalAmerican Journal of Physiology
Issue number5
Early online date8 Feb 2017
Publication statusPublished - 1 May 2017


  • silicon
  • transport
  • slc34a2
  • Xenopus laevis oocytes
  • rat kidneys

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