Surprising Substrate Versatility in SLC5A6: Na⁺-COUPLED I⁻ TRANSPORT BY THE HUMAN Na⁺/MULTIVITAMIN TRANSPORTER (hSMVT)
Iodide (I⁻) is an essential constituent of the thyroid hormones triiodothyronine and thyroxine, which are required for the development of the central nervous system in the fetus and newborn. I⁻ uptake in the thyroid is mediated by the Na⁺/I⁻ symporter (NIS). NIS has gained particular medical interes...
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Veröffentlicht in: | The Journal of biological chemistry 2011-01, Vol.286 (1), p.131-137 |
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Sprache: | eng |
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Zusammenfassung: | Iodide (I⁻) is an essential constituent of the thyroid hormones triiodothyronine and thyroxine, which are required for the development of the central nervous system in the fetus and newborn. I⁻ uptake in the thyroid is mediated by the Na⁺/I⁻ symporter (NIS). NIS has gained particular medical interest due to its sensitivity to the environmental pollutant perchlorate (ClO[Formula: see text]) and its implication in radioiodide cancer treatment. Recently, others have shown that I⁻ absorption in the intestine is mediated by NIS (Nicola, J. P., Basquin, C., Portulano, C., Reyna-Neyra, A., Paroder, M., and Carrasco, N. (2009) Am. J. Physiol. Cell Physiol. 296, C654-662). However, their data suggest the participation of other systems in the homeostasis of I⁻, in particular because in vivo uptake studies revealed a ClO[Formula: see text]-insensitive transport component. Here, we describe Na⁺-coupled I⁻ uptake by the human Na⁺/multivitamin transporter (hSMVT), a related protein isolated from the placenta, where it was suggested to supply the fetus with the water-soluble vitamins biotin and pantothenic acid, and α-lipoic acid. hSMVT-mediated Na⁺/I⁻ symport is inhibited by the other three organic hSMVT substrates but not by NIS substrates; notably, hSMVT is insensitive to ClO[Formula: see text]. Because hSMVT is found in the intestine and in many other tissues, we propose that hSMVT may play an important role in the homeostasis of I⁻ in the body. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M110.167197 |