Lysine Acetylation of Aquaporin-3 in Renal Principal Cell Mediates Water Homeostasis
Authors: Huynh Nha Van , Mendoza Luciano , Rehage Cassidy , Patel Margi , Hyndman Kelly 
Published: May 2024

The kidneys function to maintain water homeostasis. High plasma osmolality activates the release of the antidiuretic hormone vasopressin (AVP), which acts on the kidneys through its receptor AVPR2 on the principal cell (PC) to increase apical aquaporin-2 (AQP2) and basolateral AQP3 abundance for enhanced water reabsorption. However, unlike AQP2, the regulation mechanism(s) of AQP3 is unclear. We previously identified a novel AQP3 post-translational modification: acetylation of lysine 282 (K282), which we hypothesize to positively regulate PC water permeability. We developed mouse models of acetylated AQP3 by mutating K282 to glutamine (K282Q; Q mutant) and deacetylated AQP3 by mutating K282 to arginine (K282R; R mutant), on C57BL/6J background to determine the functional consequences of lysine acetylated AQP3. Male and female mice (10-15 weeks old) received a standard chow diet and free access to water. We first investigated the responses to endogenous AVPR2 activation by subjecting the mice to 18-hr overnight water deprivation and compared to mice with ad libitum water access (ad lib). All dehydrated mice (males WT 3087 ± 291 mOsm/kg, n = 8; Q 3688 ± 113 mOsm/kg, n = 6; R 3447 ± 171 mOsm/kg, n = 11; females WT 3393 ± 266 mOsm/kg, n = 8; Q 3586 ± 206 mOsm/kg, n = 9; R 3749 ± 126 mOsm/kg, n = 10) had higher urine osmolality than ad lib mice (males WT 2409 ± 165 mOsm/kg, n = 8; Q 2428 ± 316 mOsm/kg, n = 7; R 1960 ± 196 mOsm/kg, n = 7; females WT 2281 ± 96 mOsm/kg, n = 8; Q 1935 ± 190 mOsm/kg, n = 11; R 2279 ± 249, n = 7, two-way ANOVA p[treatment] <0.0001 for both sexes). However, there were no significant differences among the genotypes in both sexes [two-way ANOVA p[sex] > 0.05). For plasma osmolality, all dehydrated mice in both sexes (males WT 332 ± 2 mOsm/kg, n = 10; Q 324 ± 2 mOsm/kg, n = 8; R 323 ± 2 mOsm/kg n = 11; females WT 316 ± 3 mOsm/kg, n =10; Q 320 ± 2 mOsm/kg, n = 10; R 308 ± 3 mOsm/kg, n = 11) had higher values than ad lib mice (males WT 314 ± 3 mOsm/kg, n = 10; Q 309 ± 1 mOsm/kg, n = 9; R 313 ± 3 mOsm/kg n = 10; females WT 312 ± 2 mOsm/kg, n =11; Q 305 ± 2 mOsm/kg, n = 11; R 301 ± 4 mOsm/kg, n = 10, 2-way ANOVA p[treatment] < 0.0001 for males and = 0.0006 for females). Female R mutants had lower plasma osmolality than WTs and Q in both ad lib and dehydrated groups (2-way ANOVA p[genotype] = 0.0045). In males, compared to WTs, Q and R mutants had similar plasma osmolality in the ad lib but lower in dehydrated group (2-way ANOVA p[genotype] = 0.0359). This suggests that deacetylated AQP3 may result in a reset osmostat, although this remains to be explored further. We next compared the responses of WT and Q mutants to 4-hour exogenous AVPR2 activation by dDAVP (10 ng, i.p). Q females exhibited lower plasma osmolality than WT females (286 ± 4 vs. 305 ± 2 mOsm/kg, n = 11 for both, Student’s t-test p = 0.0005) suggesting lysine acetylation of AQP3 leads to acute enhancement of water permeability. However, there were no significant differences between Q and WT males (300 ± 5 (n = 7) vs. 303 ± 2 mOsm/kg (n = 8), Student’s t-test p > 0.05). Therefore, we conclude that lysine acetylation of AQP3 contributes to renal PC water permeability and this may be sex-dependent. Thus, acetylated AQP3 is a novel mechanism to maintain water homeostasis. R01DK128001. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.