Transcriptome analysis on whole kidney of Usp2 knockout mice

Ubiquitylation plays an important role in the control of Na+ homeostasis by the kidney. It is well established that the epithelial Na+ channel ENaC is regulated by the ubiquitin-protein ligase NEDD4-2, limiting ENaC cell surface expression and activity. Ubiquitylation can be reversed by the action of deubiquitylating enzymes (DUBs). One such DUB, USP2-45, was identified previously as an aldosterone-induced protein in the kidney, and is also a circadian output gene. In heterologous expression systems USP2-45 binds to ENaC, deubiquitylates it and enhances channel density and activity at the cell surface. Because the role of USP2-45 in renal Na+ transport had not been studied in vivo, we investigated here the effect of Usp2 gene inactivation in this process. We demonstrate first that the USP2-45 protein has a rhythmic expression with a peak at ZT12. Usp2-KO mice did not show any differences to wild-type littermates with respect to the diurnal control of Na+ or K+ urinary excretion and plasma levels neither on standard diet, nor after acute and chronic changes to low and high Na+ diets, respectively. Moreover, they had similar aldosterone levels either at low or high Na+ diet. Blood pressure measurements using telemetry did not reveal variations as compared to control mice. Usp2-KO did neither display alternations in ENaC or Na+,Cl--cotransporter (NCC) expression, nor were there any changes in regulatory protein levels, as evidenced by immunoblotting and transcriptome analysis. We conclude that USP2-45 is not crucial for the regulation of Na+ balance or maintenance of blood pressure in vivo.

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Pouly D, Debonneville A, Ruffieux-Daidié D, Maillard M, Abriel H, Loffing J, Staub O