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

Abstract

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.

Disturbed Ca2+-signaling by chloroacetaldehyde: A possible cause for chronic ifosfamide nephrotoxicity

“…These effects could be due to the property of CAA to react with sulfhydryl groups [3]. Modification of PKA activity by sulfhydryl reagents has been described [35,36]. Furthermore, there is evidence for inhibition of the NCX by covalent modification of cysteine residues [37].…”

Mechanisms of Hyposmotic Volume Regulation in Isolated Nematocytes of the Anthozoan <i>Aiptasia diaphana</i>

“…5 shows that 4 mM NEM had a dual effect: It reduced sharply the maximum hyposmotical increase of the A/A 0 ratio seen previously from 1.12±0.001 in the NEMfree controls to 1.02±0.003 (p<0.05), which was only slightly higher than the A/A 0 of 0.98±0.001 observed after restoration of isosmotic ASW. Since NEM targets functionally crucial thiols in aquaporins [35,36], and blocks oxytocin-induced water transport in frog urinary bladder [37], it could well have inactivated the aquaporins responsible for the initial increase in A/A 0 ratio. Given that the concentration of NEM used here was higher than 2 mM [2], it is possible that its action was not only through thiol but also through amino groups.…”