STIM1 and cyclic hematopoiesis: Furthermore, silencing of stromal interaction molecule 1 (STIM1), a Ca+2 sensor on the endoplasmic reticulum, attenuated hypoxia-induced increases in rat pulmonary artery smooth muscle cell proliferation by inhibiting NFATc3 nuclear import [38] further supporting a role for NFATc3 in CH-induced pulmonary hypertension in rats.