title: Restoration of NBD1 thermal stability is necessary and sufficient to correct ∆F508 CFTR folding and assembly.
abstract: Cystic fibrosis transmembrane conductance regulator (CFTR) (ABCC7), unique among ABC exporters as an ion channel, regulates ion and fluid transport in epithelial tissues. Loss of function due to mutations in the cftr gene causes cystic fibrosis. The most common cystic-fibrosis-causing mutation, the deletion of F508 (ΔF508) from the first nucleotide binding domain (NBD1) of CFTR, results in misfolding of the protein and clearance by cellular quality control systems. The ΔF508 mutation has two major impacts on CFTR: reduced thermal stability of NBD1 and disruption of its interface with membrane-spanning domains (MSDs). It is unknown if these two defects are independent and need to be targeted separately. To address this question, we varied the extent of stabilization of NBD1 using different second-site mutations and NBD1 binding small molecules with or without NBD1/MSD interface mutation. Combinations of different NBD1 changes had additive corrective effects on ∆F508 maturation that correlated with their ability to increase NBD1 thermostability. These effects were much larger than those caused by interface modification alone and accounted for most of the correction achieved by modifying both the domain and the interface. Thus, NBD1 stabilization plays a dominant role in overcoming the ΔF508 defect. Furthermore, the dual target approach resulted in a locked-open ion channel that was constitutively active in the absence of the normally obligatory dependence on phosphorylation by protein kinase A. Thus, simultaneous targeting of both the domain and the interface, as well as being non-essential for correction of biogenesis, may disrupt normal regulation of channel function.
authors.affiliation: Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
authors.forename: Lihua
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
authors.forename: Andrei A
authors.initials: AA
authors.lastname: Aleksandrov
authors.affiliation: Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
authors.forename: Jianli
authors.initials: J
authors.lastname: An
authors.affiliation: Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
authors.forename: Liying
authors.initials: L
authors.lastname: Cui
authors.affiliation: Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
authors.forename: Zhengrong
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
authors.forename: Christie G
authors.initials: CG
authors.lastname: Brouillette
authors.affiliation: Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA. Electronic address: jack_riordan@med.unc.edu.
authors.forename: John R
authors.initials: JR
authors.lastname: Riordan
mesh_terms: D001665:Binding Sites; D015153:Blotting, Western; D002152:Calorimetry, Differential Scanning; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D007700:Kinetics; D008958:Models, Molecular; D010766:Phosphorylation; D017510:Protein Folding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion / Q000235:genetics*; D015398:Signal Transduction; D013696:Temperature
chemical_list: C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator
keywords: CFTR; cystic fibrosis; ion channel; protein folding; thermal stability
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