Lysine acetylation of aquaporin-3 promotes water permeability but is not essential for urine concentrating ability.

Abstract

Aquaporin-3 (AQP3) mediates basolateral water transport in the kidney principal cells contributing to urine concentration. We previously identified the acetylation of lysine 282 (K282) in the C-terminus of AQP3, which we hypothesized as a positive regulator of AQP3 water permeability. AQP3 acetylation (K282Q or Q), or deacetylation (K282R or R) mimetic mutant mice models were created using CRISPR/Cas9. Male and female wild-type (WT) and mutant mice were assigned to hydrating diets and water deprivation protocols. Urine and plasma osmolality in response to acute vasopressin receptor-2 activation with desmopressin (dDAVP) or inhibition by tolvaptan were determined. In vitro water permeability of murine principal kidney cortical collecting duct (mpkCCD) cells stably expressing AQP3 WT, Q, or R was measured. Acetylated AQP3 was prominent in the cortical to inner medullary collecting ducts of dehydrated versus hydrated mice. At baseline the mutations did not affect the kidney transcriptome, AQP3 abundance, nor subcellular localization. Urine osmolality of the mutant mice was within the normal range. With dehydration, all mice excreted a concentrated urine; however, the female Q mutants exhibited significantly greater 24 h urine osmolality than WT, suggesting greater water reabsorption. In response to acute dDAVP, all mice produced a concentrated urine; however, female Q mutants had a more dilute plasma than WT, further suggesting greater water retention. mpkCCD Q mutant cells exhibited greater water permeability than WT and R cells. We conclude that AQP3 K282 acetylation promotes principal cell water permeability in a sex-dependent manner, however, it is not essential for urine concentration.