Aquaporin water channel (AQP)

Renal epithelial aquaporin water channels, primarily Aquaporin-1 (AQP1), Aquaporin-2 (AQP2), Aquaporin-3 (AQP3), and Aquaporin-4 (AQP4), are specialized membrane proteins that facilitate the rapid transport of water across the renal tubular epithelium [1][4]. AQP1 is constitutively expressed in the proximal tubule and descending thin limb, where it mediates the majority of constitutive water reabsorption [3]. AQP2 is the most clinically significant therapeutic target, located in the collecting duct; its translocation to the apical membrane is dynamically regulated by arginine vasopressin (AVP) via V2 receptors to control urine concentration [2][5]. AQP3 and AQP4 are located on the basolateral membrane of the collecting duct, providing the exit pathway for water into the interstitium [4]. Dysregulation of these channels is central to water balance disorders, including nephrogenic diabetes insipidus, where AQP2 is defective or unresponsive, and fluid retention states like heart failure or SIADH [3][5]. While direct pharmacological blockers of the aquaporin pore are not yet in widespread clinical use, indirect modulation through vasopressin receptor antagonists (vaptans) is a standard treatment for hyponatremia and congestion [1][3].

Other names

AquaporinWater channelCHIP28WCH-CDAquaporin-CD

Indirect modulation via Vasopressin V2 receptor antagonism (preventing AQP2 apical membrane translocation); direct pore inhibition (experimental); transcriptional regulation of AQP expression; downregulation of protein abundance.