title: Soft substrate up-regulates the interaction of STIM1 with store-operated Ca2+ channels that lead to normal epithelial cell apoptosis.
abstract: We have demonstrated that soft substrate induced apoptosis in polarized cells, but not in transformed cells by disturbance of Ca(2+) homeostasis. This study aims to further investigate the regulatory mechanisms underlying the disruption of Ca(2+)-signaling integrity in soft substrate-induced epithelial apoptosis. Soft substrate up-regulated the store-operated Ca(2+) (SOC) entry across the plasma membrane of normal cervical epithelial cells, which resulted in increased cytosolic Ca(2+) levels. Concomitantly, soft substrate induced the aggregation and translocation of stromal interacting molecule 1 (STIM1) toward the cell periphery to colocalize with Orai1, an essential pore subunit of SOC channel, detected by fluorescence resonance energy transfer approach and confocal image analyses. The disturbed Ca(2+) homeostasis resulted in the activation of mu-calpain, which cleaved alpha-spectrin, induced actin disorganization, and caused apoptosis. In contrast, soft substrate did not disturb Ca(2+) homeostasis or induce apoptosis in cervical cancer cells. Chelating extracellular Ca(2+) by EGTA and down-regulated SOC entry by small interfering RNA targeting STIM1 or inhibitors targeting Ca(2+)-binding site of calpain significantly inhibited soft substrate-induced activation of mu-calpain and epithelial cell apoptosis. Thus, soft substrate up-regulates the interaction of STIM1 with SOC channels, which results in the activation of mu-calpain and subsequently induces normal epithelial cell apoptosis.
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Wen-Tai
authors.initials: WT
authors.lastname: Chiu
authors.forename: Ming-Jer
authors.initials: MJ
authors.lastname: Tang
authors.forename: Hsiao-Chun
authors.initials: HC
authors.lastname: Jao
authors.forename: Meng-Ru
authors.initials: MR
authors.lastname: Shen
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D002154:Calpain / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002584:Cervix Uteri / Q000166:cytology; D003094:Collagen / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D006706:Homeostasis; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism*; D000071740:ORAI1 Protein; D000071737:Stromal Interaction Molecule 1; D015854:Up-Regulation / Q000187:drug effects*; D002583:Uterine Cervical Neoplasms / Q000473:pathology
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D015544:Inositol 1,4,5-Trisphosphate; D003094:Collagen; D002154:Calpain; C449002:mu-calpain; D002118:Calcium