WNK1 is a central osmolality sensor that regulates arginine vasopressin secretion

PURPOSE OF REVIEW: Maintaining constant cellular osmolality is essential for physiological function in terrestrial animals. However, the molecular identity of the brain sensor(s) that detect extracellular hypertonicity and trigger arginine vasopressin (AVP) release has remained elusive. Early hypotheses emphasized the involvement of membrane mechanosensitive channels. More recent studies using purified proteins and heterologous expression systems have revealed that intracellular with-no-lysine (K) kinases (WNKs) possess intrinsic osmosensitivity. This review highlights emerging insights into how WNK1 senses environmental changes and regulates AVP secretion, thereby contributing to the maintenance of systemic water homeostasis. RECENT FINDINGS: Recent studies have identified WNK1 as an intracellular osmolality sensor that detects changes in extracellular tonicity and regulates AVP release. Specifically, the catalytic activity of WNK1 in neurons of the brain's circumventricular organs is enhanced by physiological increases in extracellular osmolality. This activation of WNK1 stimulates the downstream OSR1/SPAK kinase cascade and modulates Kv3.1 channel activity, ultimately increasing neuronal excitability and action potential firing. Consequently, these signaling events promote AVP release, contributing to the maintenance of systemic water homeostasis. SUMMARY: These findings underscore the critical role of intracellular kinase signaling in osmolality sensing, offering a new conceptual framework for understanding the regulation of water balance and identifying potential therapeutic targets for disorders associated with impaired osmoregulation.