Mechanosensing in the Renal Tubule: Ion Channels, Ca 2+ Signaling, and the Integration of Mechanical Cues along the Nephron.

Abstract

Renal tubular epithelia continuously experience mechanical forces generated by luminal flow and pressure, yet these cues vary dramatically across nephron segments. Despite the declining fluid shear stress from proximal tubule to the collecting duct, the abundance and diversity of mechanosensitive channels increase distally, suggesting that distal segments integrate multiple mechanical inputs rather than fluid shear stress alone. Tubular cells decode at least two spatially segregated cues: tangential drag at the apical surface, sensed by structures such as microvilli and the primary cilium, and circumferential wall tension transmitted to the basolateral domain during flow-driven distension. This multidimensional information is translated into segment-specific physiological responses by compartmentalized Ca 2+ signaling, which rapidly couples mechanosensitive ion channels and mechanochemical pathways, including flow-induced ATP release and purinergic purinergic receptor activation, to spatially restricted subcellular microdomains. These domain-specific Ca 2+ codes control polarity, ion transport, cytoskeletal organization, and transcription, while interfacing with slower hormonal modulatory signals. Importantly, dysfunction of mechanosensitive Ca 2+ signaling has direct pathological relevance: polycystin mutations disrupt ciliary Ca 2+ homeostasis in autosomal dominant polycystic kidney disease, while aberrant mechanotransduction through PIEZO1 and integrin-coupled adhesions supports profibrotic remodeling. This review examines the subcellular domains involved in renal mechanotransduction, focusing primarily on the distal nephron: the apical membrane, the primary cilium, and the basolateral domain including stretch-activated channels and extracellular matrix-coupled adhesions. It highlights how channels and G protein-coupled receptors shape distinct Ca 2+ codes that fine-tune epithelial function along the nephron and identifies key gaps linking mechanosensing to tubular pathophysiology.