Article

The ABC protein turned chloride channel whose failure causes cystic fibrosis

Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, New York, NY 10021, USA.
Nature (Impact Factor: 41.46). 04/2006; 440(7083):477-83. DOI: 10.1038/nature04712
Source: PubMed

ABSTRACT

CFTR chloride channels are encoded by the gene mutated in patients with cystic fibrosis. These channels belong to the superfamily of ABC transporter ATPases. ATP-driven conformational changes, which in other ABC proteins fuel uphill substrate transport across cellular membranes, in CFTR open and close a gate to allow transmembrane flow of anions down their electrochemical gradient. New structural and biochemical information from prokaryotic ABC proteins and functional information from CFTR channels has led to a unifying mechanism explaining those ATP-driven conformational changes.

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Available from: Paola Vergani
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    • "Part of the reason for this uncertainty is the presence of basal ATPase activity of ABC transporters in the absence of substrates, especially in in vitro assays (Woo et al., 2012). In the ATP-dependent anion channel CFTR it has been shown that only one ATP molecule is hydrolyzed by its asymmetric NBD heterodimer per functional cycle (Gadsby et al., 2006). In addition, in human MRP1 (a fused TMD 1 -NBD 1 -TMD 2 -NBD 2 ABC transporter), ATP hydrolysis predominantly occurs in the second NBD (Zhang et al., 2003). "
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    ABSTRACT: ABC transporters form the largest of all transporter families, and their structural study has made tremendous progress over recent years. However, despite such advances, the precise mechanisms that determine the energy-coupling between ATP hydrolysis and the conformational changes following substrate binding remain to be elucidated. Here, we present our thermodynamic analysis for both ABC importers and exporters, and introduce the two new concepts of differential-binding energy and elastic conformational energy into the discussion. We hope that the structural analysis of ABC transporters will henceforth take thermodynamic aspects of transport mechanisms into account as well.
    Preview · Article · Sep 2015 · Protein & Cell
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    • "The cystic fibrosis transmembrane conductance regulator (CFTR) is located in the apical membrane in various epithelial tissues in the human body, including lungs, the intestinal tract, pancreatic ducts, testes and sweat glands [1]. CFTR is not only responsible for the transport of chloride ions but also acts as a bicarbonate anion and glutathione channel [2] [3]. "
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    ABSTRACT: The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl(-) channel that is essential for electrolyte and fluid homeostasis. Preliminary evidence indicates that CFTR is a mechanosensitive channel. In lung epithelia, CFTR is exposed to different mechanical forces such as shear stress (Ss) and membrane distention. The present study questioned whether Ss and/or stretch influences CFTR activity (wiltype, ∆F508, G551D). Human CFTR (hCFTR) was heterologously expressed in Xenopus oocytes and the response to the mechanical stimulus and forskolin/IBMX (FI) was measured by two-electrode voltage-clamp experiments. Ss had no influence on hCFTR activity. Injection of an intracellular analogous solution to increase cell volume alone did not affect hCFTR activity. However, hCFTR activity was augmented by injection after pre-stimulation with FI. The response to injection was similar in channels carrying the common mutations ∆F508 and G551D compared to wild type hCFTR. Stretch-induced CFTR activation was further assessed in Ussing chamber measurements using Xenopus lung preparations. Under control conditions increased hydrostatic pressure (HP) decreased the measured ion current including activation of a Cl(-) secretion that was unmasked by the CFTR inhibitor GlyH-101. These data demonstrate activation of CFTR in vitro and in a native pulmonary epithelium in response to mechanical stress. Mechanosensitive regulation of CFTR is highly relevant for pulmonary physiology that relies on ion transport processes facilitated by pulmonary epithelial cells.
    Full-text · Article · Sep 2015 · Biochimica et Biophysica Acta
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    • "Cystic fibrosis (CF) is a lethal genetic disease caused by a lack of functional cystic fibrosis transmembrane conductance regulator (CFTR), an apical Cl − channel in epithelial cells123. CFTR is a member of the ATP Binding Cassette (ABC) superfamily made of two membrane-spanning domains (MSDs), which form the channel pore, two cytoplasmic nucleotide-binding domains (NBDs), which regulate channel gating[4], and a unique phosphorylated cytoplasmic regulatory domain (RD) that regulates channel activity[5]. The most prevalent CFTR mutation, a deletion of phenylalanine at position 508 in NBD1 (F508del), accounts for approximately 70% of all CF chromosomes worldwide[6]. "
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    ABSTRACT: The cystic fibrosis transmembrane conductance regulator (CFTR) is the only member of the ATP-binding cassette (ABC) superfamily that functions as a chloride channel. The predicted structure of CFTR protein contains two membrane-spanning domains (MSDs), each followed by a nucleotide binding domain (NBD1 and NBD2). The opening of the Cl(-) channel is directly linked to ATP-driven tight dimerization of CFTR's NBD1 and NBD2 domains. The presence of a heterodimeric interfaces (HI) region in NBD1 and NBD2 generated a head to tail orientation necessary for channel activity. This process was also suggested to promote important conformational changes in the associated transmembrane domains of CFTR, which may impact the CFTR plasma membrane stability. To better understand the role of the individual HI region in this process, we generated recombinant CFTR protein with suppressed HI-NBD1 and HI-NBD2. Our results indicate that HI-NBD2 deletion leads to the loss of the dimerization profile of CFTR that affect its plasma membrane stability. We conclude that, in addition to its role in Cl(-) transport, HI-NBD2 domain confers membrane stability of CFTR by consolidating its quaternary structure through interactions with HI-NBD1 region. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Jun 2015 · Biochimica et Biophysica Acta
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