Cardiac glycoside ouabain induces activation of ATF-1 and StAR expression by interacting with the α4 isoform of the sodium pump in Sertoli cells

► The cardiotonic steroid (CTS) ouabain induces in Sertoli cells a signaling cascade. ► This happens by its interaction with the α4 isoform of Na+,K+-ATPase. ► It induces phosphorylation of the activating transforming factor 1 (ATF-1). ► As a consequence, activated ATF-1 stimulates the expression of StAR protein. ► Interactions between endogenous CTS and α4 might be crucial for male fertility.