Improvement of Chloride Transport Defect by Gonadotropin-Releasing Hormone (GnRH) in Cystic Fibrosis Epithelial Cells

Nathalie Benz,Pascal Trouvé,Mathieu Kerbiriou,Sophie Le Hir,Marie-Laure Calvez,Claude Férec,Frédéric Becq,Caroline Norez

doi:10.1371/journal.pone.0088964

Abstract

Cystic fibrosis (CF), the most common autosomal recessive disease in Caucasians, is due to mutations in the CFTR gene. F508del, the most frequent mutation in patients, impairs CFTR protein folding and biosynthesis. The F508del-CFTR protein is retained in the endoplasmic reticulum (ER) and its traffic to the plasma membrane is altered. Nevertheless, if it reaches the cell surface, it exhibits a Cl− channel function despite a short half-life. Pharmacological treatments may target the F508del-CFTR defect directly by binding to the mutant protein or indirectly by altering cellular proteostasis, and promote its plasma membrane targeting and stability. We previously showed that annexine A5 (AnxA5) directly binds to F508del-CFTR and, when overexpressed, promotes its membrane stability, leading to the restoration of some Cl− channel function in cells. Because Gonadotropin-Releasing Hormone (GnRH) increases AnxA5 expression in some cells, we tested it in CF cells. We showed that human epithelial cells express GnRH-receptors (GnRH-R) and that GnRH induces an AnxA5 overexpression and an increased Cl− channel function in F508del-CFTR cells, due to an increased stability of the protein in the membranes. Beside the numerous physiological implications of the GnRH-R expression in epithelial cells, we propose that a topical use of GnRH is a potential treatment in CF.

Highlights

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians
Among potential proteins that bind to CFTR, we demonstrated that annexin A5 (AnxA5) binds directly to Wt- and F508del-CFTR when the channel is in the plasma membrane of cells
Because the genetic background is only comparable between CFBE41o2/corr and CFBE41o2/F508del cells, statistical analysis was only performed for these cells and a higher mRNA expression was observed in CFBE41o2/F508del cells

Summary

Introduction

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians. It is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein [1]. CFTR which is a member of the ATPbinding cassette (ABC) transporter superfamily, functions as an ion channel [1,2]. It is mostly expressed in the apical membrane of epithelial cells and helps to maintain the fluid and electrolyte balance across the cell membrane. Wild-type CFTR (Wt-CFTR) biogenesis initiates in the ER where the protein is coreglycosylated, leading to an immature precursor form known as band B (,145 KDa). It further undergoes maturation and glycosylation through the Golgi, originating a complex mature form (band C, ,170-kDa) [4]. Once phosphorylated by protein kinase A (PKA) in the R domain, CFTR functions as an ATPgated chloride (Cl2) channel [8]

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