Epac1–/– and Epac2–/– mice exhibit deficient epithelial Na+ channel regulation and impaired urinary Na+ conservation

Abstract

Exchange proteins directly activated by cAMP (Epacs) are abundantly expressed in the renal tubules. We used genetic and pharmacological tools in combination with balance, electrophysiological, and biochemical approaches to examine the role of Epac1 and Epac2 in renal sodium handling. We demonstrate that Epac1 –/– and Epac2 –/– mice exhibit a delayed anti-natriuresis to dietary sodium restriction despite augmented aldosterone levels. This was associated with a significantly lower response to the epithelial Na + channel (ENaC) blocker amiloride, reduced ENaC activity in split-opened collecting ducts, and defective posttranslational processing of α and γENaC subunits in the KO mice fed with a Na + -deficient diet. Concomitant deletion of both isoforms led to a marginally greater natriuresis but further increased aldosterone levels. Epac2 blocker ESI-05 and Epac1&2 blocker ESI-09 decreased ENaC activity in Epac WT mice kept on the Na + -deficient diet but not on the regular diet. ESI-09 injections led to natriuresis in Epac WT mice on the Na + -deficient diet, which was caused by ENaC inhibition. In summary, our results demonstrate similar but nonredundant actions of Epac1 and Epac2 in stimulation of ENaC activity during variations in dietary salt intake. We speculate that inhibition of Epac signaling could be instrumental in treatment of hypertensive states associated with ENaC overactivation.

Independent regulation of Piezo1 activity by principal and intercalated cells of the collecting duct

“…Single-channel activity of Yoda-1-activated Piezo1 channel was determined in cell-attached patches on the apical membrane in freshly isolated split-opened collecting ducts and on the basolateral membrane in freshly isolated collecting ducts, as shown in representative images in Figure 6 . Gradual activation of Piezo1 by Yoda-1 was detected under voltage-clamp conditions (− Vp =− 60 mV), as previously described ( 47 , 53 ). To assess single channel conductance, pipette voltage was changed from -Vp = −100 mV to +60 mV for at 30 s. PCs and ICs were visually identified by their polygonal and round shape, respectively.…”

Lessons learned about epithelial sodium channels from transgenic mouse models

“…Activation of the cAMP pathway promoted ENaC trafficking to the apical membrane [46] and increased ENaC open probability [47]. Exchange proteins directly activated by cAMP (Epacs) are abundantly expressed in the renal tubules and constitutive knockout mice for Epac1 and Epac2 provided evidence that single or combined deletion impaired stimulation of ENaC and compromised renal sodium conservation in response to dietary sodium deficiency [48 ▪ ]. Mammalian Ste20-like protein kinase 3 (MST3/STK24) is mainly expressed in the thick ascending tubule, and at lower levels in the distal convoluted tubules.…”

Epac: A Promising Therapeutic Target for Vascular Diseases: A Review

“…However, another study found that inhibition of Epac can treat hypertension caused by epithelial Na + channel over-activation. Although more careful and long-term studies are needed to confirm the efficacy and safety of Epac inhibitors ( Tomilin et al, 2022 ), the potential therapeutic effect of Epac in renal diseases has attracted increasing interest from researchers.…”

“…The etiology is complex, making their diagnosis and treatment difficult. Despite their different expression levels, current studies show that both Epac1 and Epac2 are critical for kidney function adjustment (Cherezova et al, 2019;Tomilin et al, 2022). Chronic kidney disease (CKD), characterized by renal fibrosis, is a global health problem.…”