Dual Influence of Aldosterone on AQP2 Expression in Cultured Renal Collecting Duct Principal Cells

Udo Hasler,David Mordasini,Matthieu Bianchi,Alain Vandewalle,Eric Féraille,Pierre-Yves Martin

doi:10.1074/jbc.m212388200

Udo Hasler, David Mordasini + Show 4 more

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https://doi.org/10.1074/jbc.m212388200

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Abstract

In the renal collecting duct (CD) the major physiological role of aldosterone is to promote Na+ reabsorption. In addition, aldosterone may also influence CD water permeability elicited by vasopressin (AVP). We have previously shown that endogenous expression of the aquaporin-2 (AQP2) water channel in immortalized mouse cortical CD principal cells (mpkCCDC14) grown on filters is dramatically increased by administration of physiological concentrations of AVP. In the present study, we investigated the influence of aldosterone on AQP2 expression in mpkCCDC14 cells by RNase protection assay and Western blot analysis. Aldosterone reduced AQP2 mRNA and protein expression when administered together with AVP for short periods of time (< or =24 h). For longer periods of time, however, aldosterone increased AQP2 protein expression despite sustained low expression levels of AQP2 mRNA. Both events were dependent on mineralocorticoid receptor occupancy because they were both induced by a low concentration of aldosterone (10-9 m) and were abolished by the mineralocorticoid receptor antagonist canrenoate. Inhibition of lysosomal AQP2 protein degradation increased AQP2 protein expression in AVP-treated cells, an effect that was potentiated by aldosterone. Finally, both aldosterone and actinomycin D delayed AQP2 protein decay following AVP washout, but in a non-cumulative manner. Taken together, our data suggest that aldosterone tightly modulates AQP2 protein expression in cultured mpkCCDC14 cells by increasing AQP2 protein turnover while maintaining low levels of AQP2 mRNA expression.

Highlights

Water permeability of the renal collecting duct (CD)1 depends almost exclusively on the antidiuretic hormone [8-arginine]vasopressin (AVP), which exerts its action principally through tight regulation of aquaporin-2 (AQP2) expression
We have previously shown that endogenous expression of the aquaporin-2 (AQP2) water channel in immortalized mouse cortical CD principal cells grown on filters is dramatically increased by administration of physiological concentrations of AVP
In a first set of experiments, endogenous AQP2 expression was first increased by pretreating mpkCCDC14 cells with 10Ϫ9 M AVP for 24 h after which time the cells were subjected to additional periods of incubation (3– 48 h) in the continuous presence of AVP and in the presence or absence of 10Ϫ6 M aldosterone (Fig. 1, A and B)

Summary

Introduction

Water permeability of the renal collecting duct (CD) depends almost exclusively on the antidiuretic hormone [8-arginine]vasopressin (AVP), which exerts its action principally through tight regulation of aquaporin-2 (AQP2) expression. AVP increases CD water permeability by binding to the vasopressin V2-receptor located in the basolateral membrane of CD principal cells, an event that promotes AQP2 translocation from intracellular storage vesicles to the apical membrane [8]. Declining levels of circulating AVP quickly lead to endocytotic retrieval of apical AQP2 and to reduced CD water permeability [8] Besides this rapid action, AVP controls AQP2 expression over longer periods of time (from several hours to several days) [9]. Aldosterone promotes Naϩ reabsorption principally by increasing whole cell abundance and cell membrane expression of apical epithelial Naϩ channels and basolateral Na,K-ATPase units in the late portion of the distal tubule and in the collecting duct [22,23,24,25].

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