Folding-function relationship of the most common cystic fibrosis-causing CFTR conductance mutants.

Marcel Van Willigen,Peter Van Der Sluijs,Evelien Kruisselbrink,Annelotte M Vonk,Bertrand Kleizen,Ineke Braakman,Hui Ying Yeoh,Jeffrey M Beekman,Maarten R Egmond,Hugo R De Jonge,Cornelis K Van Der Ent

doi:10.26508/lsa.201800172

Marcel Van Willigen, Peter Van Der Sluijs + Show 9 more

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https://doi.org/10.26508/lsa.201800172

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Abstract

Cystic fibrosis is caused by mutations in the CFTR gene, which are subdivided into six classes. Mutants of classes III and IV reach the cell surface but have limited function. Most class-III and class-IV mutants respond well to the recently approved potentiator VX-770, which opens the channel. We here revisited function and folding of some class-IV mutants and discovered that R347P is the only one that leads to major defects in folding. By this criterion and by its functional response to corrector drug VX-809, R347P qualifies also as a class-II mutation. Other class-IV mutants folded like wild-type CFTR and responded similarly to VX-809, demonstrating how function and folding are connected. Studies on both types of defects complement each other in understanding how compounds improve mutant CFTR function. This provides an attractive unbiased approach for characterizing mode of action of novel therapeutic compounds and helps address which drugs are efficacious for each cystic fibrosis disease variant.

Highlights

Cystic fibrosis (CF) is caused by a mutation in CFTR, an anion channel and member of the ABC-transporter family
We investigated whether R347P CFTR that had been rescued by VX-809 became responsive to VX-770 (Fig 4C)
We investigated the structure–function relationship of the most common class-IV CF-causing CFTR mutants, defining a subgroup of CF patients known as the altered-chloride-conductance group (Welsh & Smith, 1993; Castellani et al, 2008)

Summary

Introduction

Cystic fibrosis (CF) is caused by a mutation in CFTR, an anion channel and member of the ABC-transporter family. CFTR consists of two transmembrane-spanning domains (TMD1 and TMD2), two nucleotide-binding domains (NBD1 and NBD2) and an intrinsically disordered regulatory region (R). CFTR domains mostly fold cotranslationally (Kleizen et al, 2005) and need extensive domain assembly to form a fully functional chloride channel. More than 1,800 mutations have been identified in the CFTR gene (http://genet.sickkids.on.ca). Most of these are not well characterized; the CFTR2 database on CF-causing variants was created (Sosnay et al, 2013). The initial version of CFTR2 contained 159 mutations, which account for 96% of all CF patients

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