Modulation of the aquaporin-2 localization in renal principal cells

In response to the antidiuretic hormone arginine-vasopressin (AVP), inducing elevated levels of the second messenger 3’,5’-cyclic adenosine monophosphate (cAMP) and the activation of the cAMP-dependent protein kinase (protein kinase A, PKA), the water channel aquaporin-2 (AQP2) is redistributed from intracellular vesicles into the plasma membrane of renal collecting duct principal cells. Its insertion into the plasma membrane induces the water reabsorption from primary urine and fine-tunes body water homeostasis. Dysregulation of this process causes or is associated with water balance disorders, such as diabetes insipidus (DI) (Olesen and Fenton, 2021; Christ-Crain and Gaisl, 2021). The mechanisms which control the AQP2 localization are not completely understood. The main part of this thesis describes the discovery of a hitherto unknown role of aurora kinase A (AURKA) in the control of the AQP2 localization. Two AURKA-selective inhibitors, aurora-A inhibitor I and alisertib, inhibited the cAMP-dependent AQP2 redistribution in two cell models by effects on the actin cytoskeleton. Novel derivatives of aurora-A inhibitor I provided insights into the structure–activity–relationship (SAR) of the inhibitor. Filamentous (F-) actin containing stress fibers can either serve as transport tracks for AQP2-bearing vesicles en route to the plasma membrane (Nedvetsky et al., 2007; Sasaki, Yui and Noda, 2014) or as a physical barrier by blocking the vesicles’ access to the plasma membrane (Klussmann et al., 2001; Tamma et al., 2001; Simon et al., 1993). Aurora-A inhibitor I induced the depolymerization of the actin transport tracks by activating the actin-depolymerizing protein cofilin-1 (CFL1). In contrast, alisertib promoted the formation of the actin barrier. Alisertib did not affect the CFL1 activity and must thus control the actin cytoskeleton and the AQP2 localization via different mechanisms. The second part builds on published work on the antimycotic drug fluconazole, which elicits antidiuretic effects by inducing the AQP2 redistribution to the plasma membrane of renal principal cells in the absence of AVP (Vukićević et al., 2019). The antimycotic drug tebuconazole was identified as another interesting candidate to modulate the AQP2 localization, which is of potential interest for treating certain forms of DI. In the third part, the molecular phenotype of a novel heterozygous mutation of the AQP2 gene, causing autosomal dominant nephrogenic DI (NDI), was characterized. The mutation led to an intracellular retention of AQP2 and an increase in the complex glycosylation of the protein. This thesis contributes to a better understanding of the molecular mechanisms underlying the AVP-induced AQP2 redistribution. Further, it opens new perspectives for the treatment of water balance disorders with modulators of the AQP2 localization.

Author dc:creator

• Baltzer, Sandrine Marina

Advisors dc:contributor.advisor

• Süssmuth, Roderich
• Klussmann, Enno

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-15953

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/17174