Hypotonicity stimulates potassium flux through the WNK-SPAK/OSR1 kinase cascade and the Ncc69 sodium-potassium-2-chloride cotransporter in the Drosophila renal tubule

Yipin Wu; Jeffrey N Schellinger; Chou-Long Huang; Aylin R Rodan

doi:10.1074/jbc.M114.577767

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Hypotonicity stimulates potassium flux through the WNK-SPAK/OSR1 kinase cascade and the Ncc69 sodium-potassium-2-chloride cotransporter in the Drosophila renal tubule

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Hypotonicity stimulates potassium flux through the WNK-SPAK/OSR1 kinase cascade and the Ncc69 sodium-potassium-2-chloride cotransporter in the Drosophila renal tubule

Yipin Wu, Jeffrey N Schellinger, Chou-Long Huang and Aylin R Rodan

The Journal of biological chemistry, Vol.289(38), pp.26131-26142

09/19/2014

DOI: 10.1074/jbc.M114.577767

PMCID: PMC4176205

PMID: 25086033

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Abstract

The ability to osmoregulate is fundamental to life. Adult Drosophila melanogaster maintain hemolymph osmolarity within a narrow range. Osmolarity modulates transepithelial ion and water flux in the Malpighian (renal) tubules of the fly, which are in direct contact with hemolymph in vivo, but the mechanisms causing increased transepithelial flux in response to hypotonicity are unknown. Fly renal tubules secrete a KCl-rich fluid. We have previously demonstrated a requirement for Ncc69, the fly sodium-potassium-2-chloride cotransporter (NKCC), in tubule K(+) secretion. Mammalian NKCCs are regulated by a kinase cascade consisting of the with-no-lysine (WNK) and Ste20-related proline/alanine-rich (SPAK)/oxidative stress response (OSR1) kinases. Here, we show that decreasing Drosophila WNK activity causes a reduction in K(+) flux. Similarly, knocking down the SPAK/OSR1 homolog fray also decreases K(+) flux. We demonstrate that a hierarchical WNK-Fray signaling cascade regulates K(+) flux through Ncc69, because (i) a constitutively active Fray mutant rescues the wnk knockdown phenotype, (ii) Fray directly phosphorylates Ncc69 in vitro, and (iii) the effect of wnk and fray knockdown is abolished in Ncc69 mutants. The stimulatory effect of hypotonicity on K(+) flux is absent in wnk, fray, or Ncc69 mutant tubules, suggesting that the Drosophila WNK-SPAK/OSR1-NKCC cascade is an essential molecular pathway for osmoregulation, through its effect on transepithelial ion flux and fluid generation by the renal tubule.

Animals

Drosophila melanogaster

Drosophila Proteins - metabolism

Kidney Tubules - metabolism

Osmolar Concentration

Osmoregulation

Potassium - metabolism

Protein-Serine-Threonine Kinases - metabolism

Sodium-Potassium-Chloride Symporters - metabolism

Details

Title: Subtitle: Hypotonicity stimulates potassium flux through the WNK-SPAK/OSR1 kinase cascade and the Ncc69 sodium-potassium-2-chloride cotransporter in the Drosophila renal tubule
Creators: Yipin Wu - The University of Texas Southwestern Medical Center
Jeffrey N Schellinger - The University of Texas Southwestern Medical Center
Chou-Long Huang - The University of Texas Southwestern Medical Center
Aylin R Rodan - The University of Texas Southwestern Medical Center
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.289(38), pp.26131-26142
DOI: 10.1074/jbc.M114.577767
PMID: 25086033
PMCID: PMC4176205
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Grant note: DK079328 / NIDDK NIH HHS 2P40OD010949-10A1 / NIH HHS R01 GM084947 / NIGMS NIH HHS T32 DK007257 / NIDDK NIH HHS P40 OD010949 / NIH HHS R01 DK059530 / NIDDK NIH HHS DK59530 / NIDDK NIH HHS P30 DK079328 / NIDDK NIH HHS K08 DK091316 / NIDDK NIH HHS DK007257 / NIDDK NIH HHS R01-GM084947 / NIGMS NIH HHS DK091316 / NIDDK NIH HHS
Language: English
Date published: 09/19/2014
Academic Unit: Nephrology; Internal Medicine
Record Identifier: 9984359851002771

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