EndMT has been reported to contribute to the pathogenesis of PAH. In this study, we aimed to determine the role of Ca 2+ signaling in the development of EndMT in human lung vascular endothelial cells. Our data suggest that TGF-β 1 requires store-operated Ca 2+ entry through STIM1/Orai channels to induce SNAI-mediated EndMT. For the first time, we demonstrated that TGF-β 1 -induced EndMT is a Ca 2+ -dependent event, whereas inhibition of STIM1/Orai interaction attenuated EndMT in response to TGF-β 1 .