Abstract: TH-PO348
WNK1 Is a Central Osmolality Sensor for Arginine Vasopressin (AVP) Release
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Basic
November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders
- 1001 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Basic
Authors
- Jin, Xin, Department of Medicine, Division of Nephrology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States
- Xie, Jian, Department of Medicine, Division of Nephrology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States
- Huang, Chou-Long, Department of Medicine, Division of Nephrology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States
Background
Terrestrial animals are subject to constant stress of water deprivation. Maintaining internal osmolality constancy is essential for life. The circumventricular organs (CVO’s) of brain including the organum vasculosum of the lamina terminalis (OVLT) and subfornical organ (SFO) lack a blood-brain barrier. Neurons in OVLT and SFO detect increases in serum osmolality (tonicity) that stimulates the production of AVP in paraventricular nuclei (PVN) to be released in the posterior pituitary. Current hypothesis for osmolality sensors focuses on mechanosensitive membrane proteins. The role of intracellular molecules is unknown.
Methods
Metabolic cage studies were performed in mice with neuronal-specific conditional knockout (cKO) of Wnk1, mice in which WNK1 in OVLT is deleted by stereotaxic injection of Cre-recombinase carrying retrograde AAV virus injected into PVN, and mice in which Kv3.1 channel on OVLT is knock down by injection of shRNA. Urine output, water intake, serum, urine osmolality, serum AVP and copeptin levels were measured. Action potential in OVLT neurons is recorded in isolated brain slice recording
Results
WNK1 kinase in OVLT is activated by water restriction evident by increased serine-382 phospho-WNK1. Neuronal-specific cKO of Wnk1 causes polyuria with decreased urine osmolality that persists in water restriction. Circulating levels of AVP and copeptin are lower in water-restricted cKO mice versus controls. Neuronal tracing using retrograde virus reveals that WNK1 localized in PVN-projecting OVLT neurons is responsible. Hyperosmolality-induced increases in action potential firing in OVLT neurons is blunted by Wnk1 deletion or pharmacological WNK inhibitors. Knockdown of Kv3.1b channel in OVLT by shRNA reproduces the phenotypes.
Conclusion
WNK1 in OVLT detects extracellular hypertonicity leading to AVP release by activating Kv3.1 and increasing action potential firing through OVLT→PVN neuronal network. Our results provide novel insights that an intracellular protein kinase WNK1 functions as an osmosensor for extracellular tonicity. They support the biophysical studies that extraction of water from the catalytic core of WNK kinase domain activates kinase activity.
Funding
- NIDDK Support