Evolving concepts of TRPV4 in controlling flow-sensitivity of the renal nephron.

Kidneys are central for whole body water and electrolyte balance by first filtering plasma at the glomeruli and then processing the filtrate along the renal nephron until the final urine is produced. Renal nephron epithelial cells mediate transport of water and solutes which is under the control of systemic hormones as well as local mechanical stimuli arising from alterations in fluid flow. TRPV4 is a mechanosensitive Ca²⁺ channel abundantly expressed in different segments of the renal nephron. The accumulated evidence suggests a critical role for TRPV4 in sensing variations in flow rates. In turn, TRPV4 activation triggers numerous downstream cellular responses stimulated by elevated intracellular Ca²⁺ concentrations [Ca²⁺]_i. In this review, we discuss the recent concepts in flow-mediated regulation of solute homeostasis by TRPV4 in different segments of renal nephron. Specifically, we summarize the evidence for TRPV4 involvement in endocytosis-mediated albumin uptake in the proximal tubule, reactive oxygen species (ROS) generation in the ascending loop of Henle, and maintaining K⁺ homeostasis in the connecting tubule/collecting duct. Finally, we outline the function and significance of TRPV4 in the setting of polycystic kidney disease.