Regulation of the NaCl cotransporter NCC and blood pressure by the ubiquitin E3 ligase CHIP

The thiazide-sensitive sodium-chloride cotransporter (NCC) in the distal convoluted tubule (DCT) plays an important role in sodium reabsorption, blood pressure and potassium homeostasis. Dietary potassium (K + ) intake modulates NCC abundance and activity, with high K + intake promoting NCC degradation and reducing BP. We hypothesized in our previous study that ubiquitin-dependent NCC degradation involves the ubiquitin E3 ligase CHIP (C-terminus of Hsc70-interacting protein)(1). In this study, our aim was to elucidate CHIP's role in NCC degradation and its impact on BP under varying dietary K + conditions. Methods: To explore CHIP’s role in regulating NCC and BP we used complementary in vivo and ex vivo experimental approaches. For in vivo studies, CHIP knockout (KO) and wildtype (WT) control mice were fed diets with varying K + content; low (0%), normal (1%), or high (5%) for five days. BP was monitored using telemetry (24 h recordings) or via tail-cuff plethysmography (early evening). To evaluate the contribution of NCC to BP regulation, mice were treated with the NCC inhibitor hydrochlorothiazide (HCTZ, 37.5 mg/kg body weight). For ex vivo studies, renal tubule suspensions isolated from WT mice were treated with a CHIP-specific inhibitor (10 µM) to evaluate its impact on NCC protein abundance. Additionally, tubules from WT and CHIP KO mice were incubated for various time points with cycloheximide and actinomycin to assess NCC half-life using immunoblotting. Results: Pharmacological CHIP inhibition in renal tubules significantly increased NCC protein levels, demonstrating a role for CHIP in NCC biogenesis. In CHIP KO mice on a normal K + diet, NCC protein abundance was significantly higher compared to WT, with no differences in NCC mRNA, suggesting the effects of CHIP on NCC are post-translational. CHIP KO mice had elevated BP that normalized with HCTZ, highlighting a role for CHIP in BP control. CHIP KO mice demonstrated an attenuated reduction in NCC abundance in response to a high K + diet. Ex vivo, NCC half-life was prolonged in tubules isolated from CHIP KO compared to WT, further confirming CHIP’s role in NCC degradation. Conclusion: Our findings highlight CHIP as a key regulator of NCC degradation, linking CHIP activity to BP regulation. Preliminary studies suggest a role for CHIP in mediating the effects of higher dietary potassium intake on NCC. Understanding the mechanisms by which CHIP regulates NCC, especially under varying dietary K + conditions, offers valuable insights into hypertension pathophysiology and may inform future therapeutic strategies targeting BP control. (1) Kortenoeven, MLA. et al., J Biol Chem 297, (2):100915 (2021). M.A. is supported by a Danish Diabetes and Endocrine Academy postdoctoral fellowship (NNF22SA0079901) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.