# High salt-dependent regulation of the Na+/K+/2Cl- co-transporter (NKCC2) ubiquitination by E3-ubiquitin ligases in Thick Ascending Limb

> **NIH DK R03** · WAYNE STATE UNIVERSITY · 2026 · $115,500

## Abstract

HYPERTENSION is considered the leading cause of “loss of health” worldwide, involving the kidney’s inability
to excrete excess salt. During high salt intake the kidneys excrete the extra salt load by increasing the blood
pressure, phenomenon known as the pressure-natriuresis response. On the other hand, salt-sensitive
hypertension is a sustained increase in blood pressure caused by an acute salt intake, which is prevalent in 50%
of African-Americans and in 30% of Caucasians. Enhanced salt retention by the thick ascending limb of Henle’s
loop (TAL) involving the Na+/K+/2Cl- cotransporter (NKCC2) has been described in patients and genetic animal
models of salt-sensitive hypertension. However, the molecular mechanism for this defect is not fully understood.
Ubiquitination is a post-translational modification that regulates expression of channels and transporters.
Recently a novel E3 ubiquitin ligase adaptor F-Box leucine-rich domain 13 (FBXL13) was identified as novel
locus for blood pressure regulation in humans. We found that FBXL13 recognizes and interacts with NKCC2.
We found that the high salt-induced increase in NKCC2 ubiquitination is blunted in FBXL13-KO mice. Global
FBXL13-KO mice show exacerbated total NKCC2 expression. However, the global FBXL13-KO mice show high
levels of ubiquitinated NKCC2, indicating that other E3-ubiquitin ligases or adaptors mediates the ubiquitination
of NKCC2. Moreover, global FBXL13-KO mice are not salt sensitive, nor they develop hypertension. Therefore,
this R03 project aims to discover other E3-ubiquitin ligases that mediates NKCC2 ubiquitination and play a role
on NaCl reabsorption and blood pressure regulation under normal or high salt diet. In Aim I, we hypothesize that
high salt diet stimulates the 48-linked poli-ubiquitination of NKCC2 via multiple E3-ubiquitin ligases. This proposal
is significant to human health because in most hypertensive patients and in animal models of hypertension, the
natriuretic effect of nitric oxi

## Key facts

- **NIH application ID:** 11350956
- **Project number:** 5R03DK140261-02
- **Recipient organization:** WAYNE STATE UNIVERSITY
- **Principal Investigator:** Gustavo R Ares-Sarmiento
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** DK
- **Fiscal year:** 2026
- **Award amount:** $115,500
- **Award type:** 5
- **Project period:** 2025-06-12T00:00:00 → 2027-04-30T00:00:00

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11350956

## Citation

> US National Institutes of Health, RePORTER application 11350956, High salt-dependent regulation of the Na+/K+/2Cl- co-transporter (NKCC2) ubiquitination by E3-ubiquitin ligases in Thick Ascending Limb (5R03DK140261-02). Retrieved via AI Analytics 2026-07-01 from https://api.ai-analytics.org/grant/nih/11350956. Licensed CC0.

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