Bcl-2 Suppresses Sarcoplasmic/Endoplasmic Reticulum Ca2+-ATPase Expression in Cystic Fibrosis Airways

This is the publisher's version, also available electronically from http://www.atsjournals.org/doi/abs/10.1164/rccm.200807-1104OC#.U85pbrHDutsRationale: Modulation of the activity of sarcoendoplasmic reticulum calcium ATPase (SERCA) can profoundly affect Ca2+ homeostasis. Although altered calcium homeostasis is a characteristic of cystic fibrosis (CF), the role of SERCA is unknown. Objectives: This study provides a comprehensive investigation of expression and activity of SERCA in CF airway epithelium. A detailed study of the mechanisms underlying SERCA changes and its consequences was also undertaken. Methods: Lung tissue samples (bronchus and bronchiole) from subjects with and without CF were evaluated by immunohistochemistry. Protein and mRNA expression in primary non-CF and CF cells was determined by Western and Northern blots. Measurements and Main Results: SERCA2 expression was decreased in bronchial and bronchiolar epithelia of subjects with CF. SERCA2 expression in lysates of polarized tracheobronchial epithelial cells from subjects with CF was decreased by 67% as compared with those from subjects without CF. Several non-CF and CF airway epithelial cell lines were also probed. SERCA2 expression and activity were consistently decreased in CF cell lines. Adenoviral expression of mutant F508 cystic fibrosis transmembrane regulator gene (CFTR), inhibition of CFTR function pharmacologically (CFTRinh172), or stable expression of antisense oligonucleotides to inhibit CFTR expression caused decreased SERCA2 expression. In CF cells, SERCA2 interacted with Bcl-2, leading to its displacement from caveolae-related domains of endoplasmic reticulum membranes, as demonstrated in sucrose density gradient centrifugation and immunoprecipitation studies. Knockdown of SERCA2 using siRNA enhanced epithelial cell death due to ozone, hydrogen peroxide, and TNF-α. Conclusions: Reduced SERCA2 expression may alter calcium signaling and apoptosis in CF. These findings decrease the likelihood of therapeutic benefit of SERCA inhibition in CF.Supported by R01-ES014448 from the National Institute of Environmental Health Sciences, National Institutes of Health, and by the Max and Yetta Karasik Family Foundation (C.W.W.); R01-HL080322 and CF Foundation Resources Development Program Grant RDP CORE C: R026-R02 (S.R.); P01AG12993 from the National Institute of Aging (C.S.); K12 KL2RR025779 from the National Center for Research Resources (S.A.); by the Scientist Development Grant award (0830418N) from the American Heart Association (A.A.)