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Maintaining Low Ca 2+ Level in the Endoplasmic Reticulum Restores Abnormal Endogenous F508del‐CFTR Trafficking in Airway Epithelial Cells
Author(s) -
Norez Caroline,
Antigny Fabrice,
Becq Frédéric,
Vandebrouck Clarisse
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00409.x
Subject(s) - cyclopiazonic acid , cystic fibrosis transmembrane conductance regulator , endoplasmic reticulum , calnexin , microbiology and biotechnology , thapsigargin , biology , cystic fibrosis , calcium , calcium signaling , calcium in biology , medicine , intracellular , calreticulin , genetics
The most common mutation in cystic fibrosis, F508del, results in cystic fibrosis transmembrane conductance regulator protein (CFTR) that is retained in the endoplasmic reticulum (ER). Retention is dependent on chaperone proteins, many of which, like calnexin, require calcium for optimal activity. Here, we show that a limited and a maintained ER calcium level is sufficient to inhibit the F508del–CFTR/calnexin interaction and to restore the cAMP‐dependent CFTR chloride transport, thus showing the correction of abnormal trafficking. We used Western blot analysis, iodide efflux and calcium measurement techniques applied to the human airway epithelial cystic fibrosis cell line CF15 (F508del/F508del). The inhibition of ER calcium pump, with thapsigargin, curcumin, 2,5‐di( t ‐butyl)hydroquinone or cyclopiazonic acid, maintains a threshold levels of calcium that is correlated to the recovery of endogenous F508del‐CFTR transport activity. In particular, cyclopiazonic acid restores a 2‐aminoethyoxydiphenyl borate‐sensitive F508del‐CFTR trafficking with an EC 50 of 915 n m . By contrast, the 1,4,5‐trisphosphate or IP 3 receptor activators, i.e., ATP and histamine, while transiently emptying the ER intracellular calcium store, did not affect the trafficking of F508del‐CFTR. Our data suggest that decreasing the ER calcium level is not sufficient to restore the defective trafficking of F508del‐CFTR, whereas decreasing and also maintaining low ER calcium level allow correction of defective biosynthetic pathway of endogenous F508del‐CFTR in human airway epithelial cells.