Ste20-related proline-alanine-rich kinase (SPAK) and Oxidative stress-responsive kinase 1 (OSR1) (SPAK/OSR1)

Ste20-related proline-alanine-rich kinase (SPAK) and Oxidative stress-responsive kinase 1 (OSR1) are closely related serine/threonine kinases that serve as the primary downstream effectors of the WNK (With No Lysine) kinase signaling pathway. They play a fundamental role in maintaining systemic ion homeostasis and blood pressure by phosphorylating and activating cation-chloride cotransporters, specifically NKCC1, NKCC2, and NCC, in the kidney and vasculature (UniProt P48525, O95747). In the renal tubule, this activation promotes sodium and chloride reabsorption, while in vascular smooth muscle, it influences contractility and volume regulation (McCormick & Ellison, 2011). Overactivation of the WNK-SPAK/OSR1 pathway is a known driver of hypertension, most notably in Pseudohypoaldosteronism type II (Gordon syndrome), whereas its inhibition mimics the effects of thiazide and loop diuretics (Al-Amri et al., 2023). Consequently, SPAK and OSR1 are being actively investigated as therapeutic targets for the treatment of hypertension and congestive heart failure, with several small-molecule inhibitors like GNE-495 and STOCK1S-50699 demonstrating efficacy in preclinical models (Zhang et al., 2015).

Other names

STK39OXSR1Ste20-like proline-alanine-rich kinaseOxidative stress-responsive 1 proteinSerine/threonine-protein kinase 39

Inhibition of kinase catalytic activity or disruption of the WNK-binding domain to prevent the phosphorylation and subsequent activation of renal and vascular cation-chloride cotransporters (UniProt P48525, O95747).