SERCA2 regulates Piezo1 channel activation and contributes to the cardiac function and baroreflex in mice

Piezo1 channels play important roles in physiological processes such as tactile sensation, blood pressure (BP) control, cardiac development, inflammatory responses as well as in disease processes. Sarco-endoplasmic reticulum Ca²⁺-transporting ATPase (SERCA) is the only active protein in the SR that orchestrates calcium homeostasis by translocation of Ca²⁺ from the cytoplasm to the sarcoplasmic reticulum. It has been shown that SERCA2 inhibits Piezo1 function in mammals by directly acting on the Piezo1 mechano-transduction module of mechanosensitive ion channels. In this study, we investigated whether SERCA2 regulates Piezo1 activation indirectly by modulating Ca²⁺ homeostasis. We showed that treatment with a Piezo1 agonist Yoda1 (5 µM) markedly increased the viability and ATP synthesis of primary cardiomyocytes as well as intracellular Ca²⁺ content through activation of Piezo1, and upregulated the expression of Piezo1 and SERCA2 in the cardiomyocytes. However, si-Piezo1 transfection resulted in downregulation of SERCA2 expression with opposite effects on viability and ATP synthesis and intracellular Ca²⁺ content that could not be reversed by application of Yoda1. Interestingly, application of a SERCA2 channel inhibitor paxilline (Pax, 10 µM) reversed the inhibitory effect of si-Piezo1 transfection on cardiomyocyte function. Using patch clamping and Ca²⁺ transient analyses in cardiomyocytes, we demonstrated that application of Pax inhibited Yoda1-mediated Ca²⁺ currents and APD₅₀, confirming that Piezo1 activation by Yoda1 was significantly inhibited by Pax. Furthermore, application of Yoda1 was able to reverse si-SERCA2 transfection-induced impairment of myocardial function. Microinjection of Yoda1 and Pax into nodose ganglion (NG) in HFD-HTN model rats also demonstrated that the effect of Yoda1 was inhibited in the presence of Pax, thus confirming that Pax inhibited intracellular Ca²⁺ recycling by SERCA2. These results demonstrate for the first time that the application of Pax inhibits the recycling of intracellular Ca²⁺ by SERCA2 and reverses the reduction in cardiomyocyte function caused by downregulation of Piezo1 expression.