NSIAD is a rare X-linked condition, caused by activating mutations in the AVPR2 gene coding for the vasopressin V2 receptor (V2R) associated with hyponatremia, despite undetectable plasma vasopressin levels. We have recently provided in vitro evidence that, compared to V2R-wt, expression of activating V2R mutations R137L, R137C and F229V cause a constitutive redistribution of the AQP2 water channel to the plasma membrane, higher basal water permeability and significantly higher basal levels of p256-AQP2 in the F229V mutant but not in R137L or R137C. In this study, V2R mutations were expressed in collecting duct principal cells and the associated signalling was dissected. V2R-R137L and R137C mutants had significantly higher basal pT269-AQP2 levels -independently of S256 and PKA-which were reduced to control by treatment with Rho kinase (ROCK) inhibitor. Interestingly, ROCK activity was found significantly higher in V2R-R137L along with activation of the Gα12/13–Rho–ROCK pathway. Of note, inhibition of ROCK reduced the basal elevated osmotic water permeability to control. To conclude, our data demonstrate for the first time that the gain-of-function mutation of the V2R, R137L causing NSIAD, signals through an alternative PKA-independent pathway that increases AQP2 membrane targeting through ROCK-induced phosphorylation at S/T269 independently of S256 of AQP2.

中文翻译：

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加压素受体2突变体R137L通过增加AQP2膜独立于S256磷酸化的替代途径与不适当的抗利尿作用（NSIAD）的肾病综合征相关联。

NSIAD是一种罕见的X连锁疾病，由激活AVPR2中的突变引起尽管血浆血浆加压素水平未检出，但编码与降钠血症相关的加压素V2受体（V2R）的基因。我们最近提供了体外证据，与V2R-wt相比，激活的V2R突变R137L，R137C和F229V的表达引起AQP2水通道向质膜的组成性重新分布，较高的基础水渗透性和显着较高的p256基础水平-AQP2在F229V突变体中，但不在R137L或R137C中。在这项研究中，V2R突变在收集导管的主细胞中表达，并解剖了相关的信号传导。V2R-R137L和R137C突变体具有较高的基础pT269-AQP2水平-独立于S256和PKA-，通过Rho激酶（ROCK）抑制剂治疗可将其降低。有趣的是 在V2R-R137L中，随着Gα12/ 13–Rho–ROCK途径的激活，ROCK活性明显增高。值得注意的是，ROCK的抑制降低了基础渗透压渗透率至对照水平。总而言之，我们的数据首次证明，导致NSIAD的V2R，R137L的功能获得突变通过另一种独立于PKA的途径发出信号，该途径通过ROCK诱导的S / T269磷酸化作用独立于PKA，从而增加了AQP2膜的靶向性， AQP2的S256。