Annexin A5 increases the cell surface expression and the chloride channel function of the ΔF508-cystic fibrosis transmembrane regulator

Abstract

Cystic fibrosis (CF) is caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In CF, the most common mutant DeltaF508-CFTR is misfolded, is retained in the ER and is rapidly degraded. If conditions could allow DeltaF508-CFTR to reach and to stabilize in the plasma membrane, it could partially correct the CF defect. We have previously shown that annexin V (anxA5) binds to both the normal CFTR and the DeltaF508-CFTR in a Ca(2+)-dependent manner and that it regulates the chloride channel function of Wt-CFTR through its membrane integration. Our aim was to extend this finding to the DeltaF508-CFTR. Because some studies show that thapsigargin (Tg) increases the DeltaF508-CFTR apical expression and induces an increased [Ca(2+)](i) and because anxA5 relocates and binds to the plasma membrane in the presence of Ca(2+), we hypothesized that the Tg effect upon DeltaF508-CFTR function could involve anxA5. Our results show that raised anxA5 expression induces an augmented function of DeltaF508-CFTR due to its increased membrane localization. Furthermore, we show that the Tg effect involves anxA5. Therefore, we suggest that anxA5 is a potential therapeutic target in CF.

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

“…8, 9). According to our previous work [28], [29], we found that the presence of F508del-CFTR was increased in membranes. Our results showing in the CFBE41o−/F508del cells an increased CFTR membrane localization after GnRH treatment could not be related to the additional plasmid inserted in the CFBE41o- cells because in biotinylation experiments without GnRH, the amount of CFTR in 16HBE14o- cells is not different than in CFBE41o−/corr cells.…”

“…Among proteins that directly bind to CFTR, we previously showed that AnxA5 binds to NBD1 and, when over expressed, may restore some Cl − channel function due to an increased stabilization of CFTR in membranes [28], [29]. AnxA5 belongs to the annexin family which is characterized by calcium-dependent phospholipid binding.…”

“…Because our previous results showed that raised AnxA5 expression induced an augmented function of F508del-CFTR due to increased membrane localization [29], the aim of the present study was to highlight a mean to increase AnxA5 expression in F508del-CFTR expressing cells, using a drug with no side effect upon cell survival. Because it was previously showed that AnxA5 is synthesized in gonadotropes and in various cell types under the effect of gonadotropin-releasing hormone (GnRH) or some of its analogs, through mitogen activated protein kinase (MAPK), we tested the hypothesis that GnRH could increase AnxA5 expression in a human epithelial cell line and subsequently induce an increased F508del-CFTR function [30]–[32].…”

The calpain-caspase 12-caspase 3 cascade leading to apoptosis is altered in F508del-CFTR expressing cells

“…Pr. D.C. Grüenert (San Francisco, CA, U.S.A) kindly provided the normal human bronchial polarized epithelial cells 16HBE14oexpressing the normal CFTR, their CF counterparts CFBE41oexpressing the F508del-CFTR and the corrected CFBE41o-cells [46][47][48][49][50]. The cells were cultured in Eagle's minimal essential medium (MEM) supplemented with 10% FBS and glutamine on an extracellular matrix (CellBind Corning, Bioblock).…”

Functional Interactions between BKCaα‐Subunit and Annexin A5: Implications in Apoptosis

“…The annexins are a structurally related family of Ca 2+ -sensitive proteins which participate in a wide range of cellular functions, including cellular signalling, cell migration, proliferation, and apoptosis [ 18 – 21 ]. These proteins have been shown to interact with a number of ion channels and are important in both membrane trafficking and modifying of ion channel function [ 1 , 22 , 23 ]. Using a proteomics-based approach, which previously identified heme oxygenase-2 (HO-2) as O 2 -sensing protein partner of BK Ca , we also identified ANXA5 as a potential interacting protein of BK Ca [ 24 ].…”