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XB-ART-39797
J Am Soc Nephrol 2009 Jun 01;206:1314-22. doi: 10.1681/ASN.2008050542.
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Renal and brain isoforms of WNK3 have opposite effects on NCCT expression.

Glover M , Zuber AM , O'Shaughnessy KM .


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Mutations in the WNK kinases WNK1 and WNK4 cause a rare familial form of hypertension (Gordon syndrome) by increasing expression of the thiazide-sensitive co-transporter NCCT in the kidney. Regulation of NCCT expression involves a scaffold of proteins composed of several kinases, including the third member of the WNK kinase family, WNK3. This protein, expressed in several tissues including kidney and brain, displays splice variation around exons 18 and 22. We expressed these proteins in Xenopus oocytes and found that the renal isoform of WNK3 increased but the brain isoform decreased NCCT expression and activity. Introduction of a kinase-inactivating mutation into renal WNK3 reversed its action on NCCT, and the same mutation in the brain isoforms led to loss of function. We also studied the effect of phosphorylation of a key NCCT threonine (T58) on the effects of WNK3/4 coexpression; NCCT mutants with a T58A or T58D substitution had the same surface expression as T58 but had significantly altered transporter activity; however, both isoforms of WNK3 as well as WNK4 still modulated expression of these NCCT mutants. Finally, experiments using kinase-dead STE20/SPS1-related proline/alanine-rich kinase (SPAK), a putative downstream target for WNKs, revealed that brain WNK3 acts in tandem with SPAK, whereas renal WNK3 seems to upregulate NCCT through a SPAK-independent pathway. Taken together, these results suggest that the C-terminal motifs contributed by exons 18 and 22 play an important role in the actions of WNK3 isoforms on NCCT.

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Species referenced: Xenopus laevis
Genes referenced: slc12a3 slc12a3l stk24 stk39 wnk1 wnk3 wnk4

References [+] :
ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). 2002, Pubmed