STIM1 regulates platelet-derived growth factor-induced migration and Ca2+ influx in human airway smooth muscle cells.

It is suggested that migration of airway smooth muscle (ASM) cells plays an important role in the pathogenesis of airway remodeling in asthma. Increases in intracellular Ca(2+) concentrations (Ca(2+)) regulate most ASM cell functions related to asthma, such as contraction and proliferation. Recently, STIM1 was identified as a sarcoplasmic reticulum (SR) Ca(2+) sensor that activates Orai1, the Ca(2+) channel responsible for store-operated Ca(2+) entry (SOCE). We investigated the role of STIM1 in Ca(2+) and cell migration induced by platelet-derived growth factor (PDGF)-BB in human ASM cells. Cell migration was assessed by a chemotaxis chamber assay. Human ASM cells express STIM1, STIM2, and Orai1 mRNAs. SOCE activated by thapsigargin, an inhibitor of SR Ca(2+)-ATPase, was significantly blocked by STIM1 siRNA and Orai1 siRNA but not by STIM2 siRNA. PDGF-BB induced a transient increase in Ca(2+) followed by sustained Ca(2+) elevation. Sustained increases in Ca(2+) due to PDGF-BB were significantly inhibited by a Ca(2+) chelating agent EGTA or by siRNA for STIM1 or Orai1. The numbers of migrating cells were significantly increased by PDGF-BB treatment for 6 h. Knockdown of STIM1 and Orai1 by siRNA transfection inhibited PDGF-induced cell migration. Similarly, EGTA significantly inhibited PDGF-induced cell migration. In contrast, transfection with siRNA for STIM2 did not inhibit the sustained elevation of Ca(2+) or cell migration induced by PDGF-BB. These results demonstrate that STIM1 and Orai1 are essential for PDGF-induced cell migration and Ca(2+) influx in human ASM cells. STIM1 could be an important molecule responsible for airway remodeling.