Beschreibung:
Proper Na+ and K+ homeostasis by the kidney is a key process in the prevention of hypertension, the most prevalent disease in Western societies, and a primary risk factor for cardiovascular disease. The distal part of the nephron, referred to as the Aldosterone Sensitive Distal Nephron (ASDN), plays an important role in this process. There are at least two main regulatory pathways that are involved in the regulation of ions transporters (NCC, ENaC and ROMK or BK channels). One involves the WNK/SPAK/OSR1 kinase cascade, and the other the concerted action of SGK1 kinase and the ubiquitin‐protein ligase NEDD4‐2. Both pathways have been extensively studied, but there remain numerous open questions with respect to their regulation and possible crosstalks. In this project, we investigate the role of a putative adaptor protein (NDFIP2), which may provide the link between NEDD4‐2 and NCC. We first assessed the expression of Ndfip2 mRNA in microdissected tubules, and found that it is predominantly expressed in the proximal tubule and the ASDN. In MDCK‐hNCC cells, expressing human NCC under the control of a tetracycline inducible promotor, as well as endogenous NDFIP2 and NEDD4‐2, we demonstrated by co‐immunoprecipitation that NCC, NEDD4‐2 and NDFIP2 form a complex together. In parallel, we generated inducible, nephron‐specific KO mice (Ndfip2Pax8/LC1). This model allows the doxycycline‐sensitive expression of Cre‐recombinase along the nephron and consequently the deletion of exon 3 of Ndfip2. As the deletion is induced at the age of 3 weeks, compensatory mechanisms that may occur during nephrogenesis are avoided. In whole kidney lysates, only weak Ndfip2 mRNA expression and nearly complete suppression of the NDFIP2 protein is observed, which persist at least up to 2 months after deletion. Our data suggest decreased circulating levels of aldosterone, but no observable changes in NCC expression. When animal are kept under a high Na+ diet (HSD), they demonstrate difficulties to handle Na+ excess and adapt their water consumption.Support or Funding InformationThis work was supported by the Swiss National Science Foundation Grant # 310030_159735 (to OS), the Swiss Kidney.ch NCCR.