Function, pharmacological correction and maturation of new Indian CFTR gene mutations

International audienceBackground: Cystic fibrosis (CF) is rare in India. Most CF mutations identified are not yet functionally characterized. Hence, genetic counselingand adoption of therapeutic approach are particularly difficult. Our aim was to study the function and maturation of a spectrum of eleven IndianCFTR mutations from classical CF and infertile male patients with CBAVD.Methods: We used Western blot, pharmacology and iodide efflux to study CFTR maturation and chloride transport in BHK cells expressingpEGFP-CFTR constructs for L69H, F87I, S118P, G126S, H139Q, F157C, F494L, E543A, S549N, Y852F and D1270E.Results: Among these CFTR mutants, only L69H is not processed as a c-band and not functional at 37 °C. However, the functions of L69H andS549N and the maturation of L69H are corrected at 27 °C and by the investigational drug VX809.Conclusion: These data should help in developing counseling and therapeutic approaches in India. We identified L69H as a novel class II CFmutation

Functional and Pharmacological Characterization of the Rare CFTR Mutation W361R

International audienceUnderstanding the functional consequence of rare cystic fibrosis (CF) mutations is mandatory for the adoption of precision therapeutic approaches for CF. Here we studied the effect of the very rare CF mutation, W361R, on CFTR processing and function. We applied western blot, patch clamp and pharmacological modulators of CFTR to study the maturation and ion transport properties of pEGFP-WT and mutant CFTR constructs, W361R, F508del and L69H-CFTR, expressed in HEK293 cells. Structural analyses were also performed to study the molecular environment of the W361 residue. Western blot showed that W361R-CFTR was not efficiently processed to a mature band C, similar to F508del CFTR, but unlike F508del CFTR, it did exhibit significant transport activity at the cell surface in response to cAMP agonists. Importantly, W361R-CFTR also responded well to CFTR modulators: its maturation defect was efficiently corrected by VX-809 treatment and its channel activity further potentiated by VX-770. Based on these results, we postulate that W361R is a novel class-2 CF mutation that causes abnormal protein maturation which can be corrected by VX-809, and additionally potentiated by VX-770, two FDA-approved small molecules. At the structural level, W361 is located within a class-2 CF mutation hotspot that includes other mutations that induce variable disease severity. Analysis of the 3D structure of CFTR within a lipid environment indicated that W361, together with other mutations located in this hotspot, is at the edge of a groove which stably accommodates lipid acyl chains. We suggest this lipid environment impacts CFTR folding, maturation and response to CFTR modulators