Module 7: Figure collecting duct function
Vasopressin control of water flux across the kidney collecting duct.
Vasopressin acts on V2 receptors to increase the level of cyclic AMP that then works through protein kinase A (PKA) to phosphorylate aquaporin 2 (AQP2) located in vesicles. These are transported on microtubules to the apical membrane where they fuse, enabling the phosphorylated AQP2to take up water, which leaves the cell through AQP3 and AQP4 channels in the basolateral membrane. Cyclic AMP can also phosphorylate Ser-133 on cyclic AMP response element-binding protein (CREB) to increase the transcription of both AQP2 and AQP3.