Kidney Week

Abstract: TH-PO0030

WNK1 Kinase Domain Is Sufficient for Central Osmosensing for Arginine Vasopressin Release

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic Research
  October 22, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Jin, Xin, University of Iowa Health Care, Iowa City, Iowa, United States

Xin Jin

• Xie, Jian, University of Iowa Health Care, Iowa City, Iowa, United States

Jian Xie, PhD

• Amir, Mohammad, University of Iowa Health Care, Iowa City, Iowa, United States

Mohammad Amir, PhD

• Huang, Chou-Long, University of Iowa Health Care, Iowa City, Iowa, United States

Chou-Long Huang, MD, PhD

Background

Sensory neurons in the circumventricular organs (CVOs) of the brain detect serum hyperosmolality leading to arginine vasopressin (AVP) release. We reported that WNK1 in CVO neurons detects hyperosmolality, activating OSR1/SPAK and the Kv3.1 channel to increase action potential firing for AVP release. Structural and biophysical studies have shown that WNK1 kinase domain can sense dehydration. Boyd-Shiwarski et al. reported that the C-terminal intrinsically disordered regions (IDRs) of WNK1 form condensate in response to cellular dehydration to activate NKCC1 for regulatory volume recovery. We employed WNK1-SPAK/OSR1-Kv3.1-AVP release as experimental system to examine the mechanism of WNK1 activation by osmolality.

Methods

Kv3.1 current +/- hypertonic stimulation (HTS, 5 mM NaCl) was measured by whole-cell patch-clamp in WNK1/3 double knockout cells expressing recombinant full-length WNK1 or WNK1(1-491) plus SPAK and Kv3.1. WNK kinase activity was assayed by p-WNK1 and p-OSR1/SPAK. OVLT-specific Wnk1 deletion was carried out by stereotaxic injection of AAV virus carrying Cre-recombinase into homozygous Wnk1-floxed allele mice (Wnk1^f/f). AAV carrying WNK1(1-491) or variants were co-injected into OVLT. Metabolic cage clearance studies and AVP concentrations were quantified.

Results

HTS stimulated Kv3.1 in cells expressing WNK1 (1-491), SPAK, and Kv3.1. Additionally, HTS enhanced WNK1 kinase activity evidenced by autophosphorylation of WNK1 (1-491) and p-SPAK/OSR1. Kinase-dead WNK1 failed to increase Kv3.1 current with HTS. In vivo, mice with OVLT-specific Wnk1 deletion had polyuria, relative urinary hypotonicity that persisted with water restriction. Water restriction-stimulated increases in circulating AVP levels were blunted in OVLT Wnk1-deleted mice. Transgenic expression of WNK1(1-491) in OVLT restored water homeostasis and enhanced AVP release during water restriction.

Conclusion

Amino acids 1-491 of WNK1 containing the kinase domain and preceding N-terminus are sufficient for sensing hyperosmolality and AVP release through SPAK/OSR1-Kv3.1 axis. We propose and will discuss two distinct mechanisms of osmosensing, one involves the kinase domain for central osmosensing and AVP release, the other for cell volume regulation that involves condensation of WNK1 IDRs.

Acknowledgment

This work was supported in part by the NIH (DK111542 to C.L.H.)

Funding

• NIDDK Support