Article

F508del-CFTR increases intracellular Ca2+ signaling that causes enhanced calcium-dependent Cl− conductance in cystic fibrosis

Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
Biochimica et Biophysica Acta (Impact Factor: 4.66). 08/2011; 1812(11):1385-92. DOI: 10.1016/j.bbadis.2011.08.008
Source: PubMed

ABSTRACT In 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.

Download full-text

Full-text

Available from: Rainer Schreiber, Jun 23, 2015
0 Followers
 · 
179 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: cAMP-stimulated anion conductance is defective in cystic fibrosis. The regulatory domain of CFTR, the anion channel protein encoded by the CF gene, possesses an unusually high density of consensus sequences for phosphorylation by PKA (14 in a stretch of <200 amino acids). Thus it is not surprising that CFTR is viewed primarily as a cAMP-stimulated anion channel, and most studies have focused on this mode of activation. However there is growing evidence that CFTR also responds to Ca2+ mobilizing secretagogues and contributes substantially to cholinergic and purinergic responses in native tissues. G protein coupled receptors that signal through Gαq can stimulate CFTR channels by activating Ca2+-dependent adenylyl cyclase and tyrosine kinases, and also by inhibiting PP2A. Here we review evidence for these novel mechanisms of CFTR activation and discuss how they may help explain previous observations.
    The Journal of Physiology 08/2013; 591(21). DOI:10.1113/jphysiol.2013.261909 · 4.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The most common CF-causing mutations interfere with CFTR trafficking from the endoplasmic reticulum (CFTR-F508del) or prematurely terminate transcription (CFTR-null). We suspected that genotype-specific patterns of CFTR expression would have differential effects on smooth muscle cell calcium signaling and hence vascular tone. We hypothesized that compared to wild-type or CFTR-null aorta, aorta from CFTR-F508del (dF) piglets will have reduced endoplasmic reticulum calcium mobilization and decreased vasoconstriction. Aortic reactivity was assessed by myography, and ratiometric calcium imaging was performed in isolated vascular smooth muscle cells. Aorta from dF piglets had reduced myogenic tone (P<0.001) and decreased constriction to KCl (P<0.05). Combined inhibition of ryanodine and IP3 receptors decreased wild-type and CFTR-null responses to levels seen in dF aorta. Compared to wild-type cells, dF-expressing smooth muscle cells had reduced calcium transients, while CFTR-null cells had decreased baseline intracellular calcium concentrations. Expression of CFTR-F508del interferes with smooth muscle cell calcium handling and decreases aortic responsiveness.
    Journal of cystic fibrosis: official journal of the European Cystic Fibrosis Society 10/2013; DOI:10.1016/j.jcf.2013.10.009 · 3.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cystic Fibrosis (CF) disease is caused by mutations in the CFTR gene (CF transmembrane conductance regulator). F508 deletion is the most represented mutation, and F508del-CFTR is absent of plasma membrane and accumulates into the endoplasmic reticulum (ER) compartment. Using specific Ca2 + genetics cameleon probes, we showed in the human bronchial CF epithelial cell line CFBE that ER Ca2 + concentration was strongly increased compared to non-CF (16HBE) cells, and normalized by the F508del-CFTR corrector agent, VX-809. We also showed that ER F508del-CFTR retention increases SERCA (Sarcoplasmic/Reticulum Ca2 + ATPase) pump activity whereas PMCA (Plasma Membrane Ca2 + ATPase) activities were reduced in these CF cells compared to corrected CF cells (VX-809) and non-CF cells. We are showing for the first time CFTR/SERCA and CFTR/PMCA interactions that are modulated in CF cells and could explain part of Ca2 + homeostasis deregulation due to mislocalization of F508del-CFTR. Using ER or mitochondria genetics Ca2 + probes, we are showing that ER Ca2 + content, mitochondrial Ca2 + uptake, SERCA and PMCA pump, activities are strongly affected by the localization of F508del-CFTR protein.
    Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 02/2015; 1853(5). DOI:10.1016/j.bbamcr.2015.01.010 · 5.30 Impact Factor