Cystic fibrosis transmembrane conductance regulator is an epithelial cell receptor for clearance of Pseudomonas aeruginosa from the lung

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel, but its relationship to the primary clinical manifestation of CF, chronic Pseudomonas aeruginosa pulmonary infection, is unclear. We report that CFTR is a cellular receptor for binding, endocytosing, and clearing P. aeruginosa from the normal lung. Murine cells expressing recombinant human wild-type CFTR ingested 30-100 times as many P. aeruginosa as cells lacking CFTR or expressing mutant ⌬F508 CFTR protein.Purified CFTR inhibited ingestion of P. aeruginosa by human airway epithelial cells. The first extracellular domain of CFTR specifically bound to P. aeruginosa and a synthetic peptide of this region inhibited P. aeruginosa internalization in vivo, leading to increased bacterial lung burdens. CFTR clears P. aeruginosa from the lung, indicating a direct connection between mutations in CFTR and the clinical consequences of CF.

Airway epithelial control of Pseudomonas aeruginosa infection in cystic fibrosis

“…In transgenic CFTR-knockout mice, NF-κB nuclear translocation occurs much later in the airway epithelial cells [28], probably contributing more to the harmful inflammation that ensues in this environment instead of the protective inflammation that occurs when functional CFTR is present. Overall, this scenario wherein WT-CFTR binding of P. aeruginosa leads to protection and failure of this interaction in CF leads to infection is supported by data obtained in numerous in vitro and, importantly, in υivo, studies demonstrating CFTR-dependent responses to P. aeruginosa in a variety of lung epithelial cell lines and in transgenic animals [8][9][10][11][12][27][28][29]31,36]. Thus, it seems that CFTR facilitates bacterial clearance and modulates innate immunity towards P. aeruginosa in lung epithelial cells by being the linchpin needed for coordinating multiple host responses involved in resisting infection and maintaining tissue homeostasis in the long run.…”

“…P. aeruginosa recognition by WT-CFTR is due to the specific binding of amino acids 108-117 to the conserved bacterial outer core LPS [11,12,27]. CFTR binding to P. aeruginosa results in release of interleukin-1b from preformed stores in lung epithelial cells within 2-15 min [28], followed by rapid formation (5-15 min) of CFTR-containing lipid rafts in the plasma membrane, with P. aeruginosa cells attached to the CFTR.…”

“…NF-κB nuclear translocation is dependent on the signaling adaptor protein myeloid differentiation factor 88 (MyD88) [28]. An additional component of the WT-CFTRdependent response to P. aeruginosa is endocytosis by the epithelial cells and subsequent clearance of infected epithelial cells by desquamation over the next few hours [11,27]. Over the next 3-12 h, NF-κB-dependent gene transcription and protein secretion ensues that initiates a neutrophil influx into the lung tissue to remove residual surviving bacteria [29].…”

“…Although in some CF patients there are mutant CFTR alleles that allow production of near normal levels of membrane CFTR, many are defective in chloride channel function and are associated with persistent P. aeruginosa infection. Anecdotal observation of delayed P. aeruginosa colonization in patients with some 'mild' mutant CFTR alleles indicate that these alleles might be associated with retention of normal recognition of this pathogen and resultant initiation of effective innate immunity [12,27,30].…”

CFTR expression and activity from the human CFTR locus in BAC vectors, with regulatory regions, isolated by a single-step procedure

“…An additional component of the wild-type CFTR-dependent response to P. aeruginosa is endocytosis of bacteria by the epithelial cells, and the subsequent clearance of infected epithelial cells by desquamation. 25,26 In this study, and for the first time to our knowledge, we report on the circularization and transfer into bacterial cells of YAC 37AB12, which contains an insert spanning the intact human CFTR locus plus additional 5 0 and 3 0 DNA. We have produced two versions of this circular BAC that differ in the 5 0 upstream DNA by about 25 kb.…”