# Molecular mechanisms of WNK-SPAK/OSR1 regulation of transepithelial ion transport in the Drosophila renal tubule

> **NIH NIH R01** · UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH · 2020 · $343,125

## Abstract

PROJECT SUMMARY
Disorders of transepithelial ion transport underlie clinical disorders of extracellular volume, blood pressure, and
electrolytes, but molecular mechanisms of transepithelial ion transport are difficult to directly examine in the
mammalian nephron. The applicants' long-term goal is to better understand epithelial ion transport
mechanisms relevant to human kidney function, in sufficient molecular detail to define new therapeutic
strategies. The overall objective of this application is to identify regulators of a kinase cascade, consisting of
WNK (With No Lysine) and SPAK/OSR1 (Ste20-related proline alanine rich kinase/oxidative stress response)
kinases, that plays an essential role in sodium and potassium homeostasis through the regulation of renal
transepithelial ion transport. The application builds on three recent findings: Cl- directly binds to the WNK
kinase domain to inhibit autophosphorylation and activation; the scaffold protein Mo25 (Mouse protein
25/Cab39) enhances the activity of SPAK/OSR1; and low potassium diet activates WNK-SPAK/OSR1
signaling. The central hypothesis is that transepithelial ion flux is directly regulated by transported ions (Cl- and
K+) through modulation of WNK-SPAK/OSR1 signaling, while Mo25 provides additional regulatory control. The
rationale is that better understanding of these molecular mechanisms will allow the design of novel
therapeutics with fewer off-target effects. Guided by strong preliminary data, the central hypothesis will be
tested by pursuing three specific aims: 1) Determine the roles of Cl- and K+ in the regulation of WNK isoforms
in transepithelial ion transport; 2) Determine the role of Mo25 in WNK signaling in a transporting epithelium;
and 3) Probe tubule physiology using newly developed chemical WNK inhibitors. The approach is innovative
by bridging fundamental molecular insights gained from biophysical studies, with the functional physiological
roles of those molecular mechanisms, using newly developed platforms and tools to probe questions of
transporting epithelium biology. Assays have been established, and demonstrated feasible in the investigators'
hands, to examine regulation of Drosophila and mammalian WNKs by Cl- and K+ in vitro and in the fly renal
tubule, and to measure intracellular Cl- in live tubules, with temporal resolution; and to measure transepithelial
ion flux in genetically modified, or pharmacologically treated, tubules. The proposed research is significant,
because it is expected to advance understanding of molecular mechanisms of WNK-SPAK/OSR1 regulation in
a transporting renal epithelium. The studies will determine: 1) how quickly changes in intracellular Cl- change
WNK activity; 2) whether WNKs act as K+ sensors; and 3) the role of Mo25 in transepithelial ion transport. In
addition, these studies will further develop recently identified pharmacological WNK inhibitors, which will be a
useful tool for further probing the biology of WNK-SPAK/OSR1 signalin...

## Key facts

- **NIH application ID:** 9944643
- **Project number:** 5R01DK110358-06
- **Recipient organization:** UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH
- **Principal Investigator:** AYLIN RACHEL RODAN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $343,125
- **Award type:** 5
- **Project period:** 2016-12-08 → 2021-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9944643

## Citation

> US National Institutes of Health, RePORTER application 9944643, Molecular mechanisms of WNK-SPAK/OSR1 regulation of transepithelial ion transport in the Drosophila renal tubule (5R01DK110358-06). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9944643. Licensed CC0.

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