• Joana Raquel Martins, Patthara Kongsuphol, Eva Sammels, Shehrazade Dahimène, Fadi Aldehni, Luka Alexander Clarke, Rainer Schreiber, Humbert de Smedt, Margarida D Amaral, and Karl Kunzelmann.
• Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
• Biochim. Biophys. Acta. 2011 Nov 1; 1812 (11): 1385-92.

AbstractIn many cells, increase in intracellular calcium ([Ca(2+)](i)) activates a Ca(2+)-dependent chloride (Cl(-)) conductance (CaCC). CaCC is enhanced in cystic fibrosis (CF) epithelial cells lacking Cl(-) transport by the CF transmembrane conductance regulator (CFTR). Here, we show that in freshly isolated nasal epithelial cells of F508del-homozygous CF patients, expression of TMEM16A and bestrophin 1 was unchanged. However, calcium signaling was strongly enhanced after induction of expression of F508del-CFTR, which is unable to exit the endoplasmic reticulum (ER). Since receptor-mediated [Ca(2+)](i) increase is Cl(-) dependent, we suggested that F508del-CFTR may function as an ER chloride counter-ion channel for Ca(2+). This was confirmed by expression of the double mutant F508del/G551D-CFTR, which remained in the ER but had no effects on [Ca(2+)](i). Moreover, F508del-CFTR could serve as a scavenger for inositol-1,4,5-trisphosphate [IP3] receptor binding protein released with IP(3) (IRBIT). Our data may explain how ER-localized F508del-CFTR controls intracellular Ca(2+) signaling.2011 Elsevier B.V. All rights reserved.

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