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The American Journal of Physiology - Cell Physiology
Year: 2010  |  Volume: 298  |  Issue: 6  |  Page No.: 1363 - 1375

Regulated transport of sulfate and oxalate by SLC26A2/DTDST

J. F Heneghan, A Akhavein, M. J Salas, B. E Shmukler, L. P Karniski, D. H Vandorpe and S. L. Alper    

Abstract:

Nephrolithiasis in the Slc26a6–/– mouse is accompanied by 50–75% reduction in intestinal oxalate secretion with unchanged intestinal oxalate absorption. The molecular identities of enterocyte pathways for oxalate absorption and for Slc26a6-independent oxalate secretion remain undefined. The reported intestinal expression of SO42– transporter SLC26A2 prompted us to characterize transport of oxalate and other anions by human SLC26A2 and mouse Slc26a2 expressed in Xenopus oocytes. We found that hSLC26A2-mediated [14C]oxalate uptake (K1/2 of 0.65 ± 0.08 mM) was cis-inhibited by external SO42– (K1/2 of 3.1 mM). hSLC26A2-mediated bidirectional oxalate/SO42– exchange exhibited extracellular SO42– K1/2 of 1.58 ± 0.44 mM for exchange with intracellular [14C]oxalate, and extracellular oxalate K1/2 of 0.14 ± 0.11 mM for exchange with intracellular 35SO42–. Influx rates and K1/2 values for mSlc26a2 were similar. hSLC26A2-mediated oxalate/Cl exchange and bidirectional SO42–/Cl exchange were not detectably electrogenic. Both SLC26A2 orthologs exhibited nonsaturable extracellular Cl dependence for efflux of intracellular [14C]oxalate, 35SO42–, or 36Cl. Rate constants for 36Cl efflux into extracellular Cl, SO42–, and oxalate were uniformly 10-fold lower than for oppositely directed exchange. Acidic extracellular pH (pHo) inhibited all modes of hSLC26A2-mediated anion exchange. In contrast, acidic intracellular pH (pHi) selectively activated exchange of extracellular Cl for intracellular 35SO42– but not for intracellular 36Cl or [14C]oxalate. Protein kinase C inhibited hSLC26A2 by reducing its surface abundance. Diastrophic dysplasia mutants R279W and A386V of hSLC26A2 exhibited similar reductions in uptake of both 35SO42– and [14C]oxalate. A386V surface abundance was reduced, but R279W surface abundance was at wild-type levels.

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