N-ethylmaleimide causes aquaporin-2 trafficking in the renal inner medullary collecting duct by direct activation of protein kinase A.

The antidiuretic hormone arginine vasopressin increases the osmotic water permeability of the renal collecting ducts by inducing the shuttling of aquaporin-2 (AQP2) water channels from intracellular vesicles to the apical plasma membrane of the principal cells. This process has been demonstrated to be dependent on the cytoskeleton and protein kinase A (PKA). Previous studies in the toad urinary bladder, a functional homologue of the renal collecting duct, have demonstrated that the sulfhydryl reagent N-ethylmaleimide (NEM) is also able to activate the vasopressin-sensitive water permeability pathway in this tissue. The aim of the present study was to investigate the effects of NEM on AQP2 trafficking in a mammalian system. We show that NEM causes translocation of AQP2 from the cytosol to the plasma membrane in rat inner medullary collecting ducts; like the response to arginine vasopressin, this action was also dependent on an intact cytoskeleton and PKA. This effect is not mediated by cAMP but results from direct activation of PKA by NEM.