Cystic Fibrosis Transmembrane Conductance Regulator Can Export Hyaluronan

Abstract

Objectives: Hyaluronan, a major water binding component of the extracellular matrix, is synthesised within the cytosol and exported across the plasma membrane by the ABC-transporter MRP5 in fibroblasts. Although its synthesis is vital for embryogenesis, MRP5-deficient mice are without phenotype, suggesting that another transporter had substituted for the MRP5 protein. Thus, we searched for a compensatory exporter in fibroblasts from MRP5 deficient mice and found that cystic fibrosis transmembrane conductance regulator (CFTR) mRNA was upregulated. Methods: Hyaluronan export was measured in cell culture. The CFTR transporter was knocked out using si-RNA. Blockers of the ABC-transporter family were used to ascertain the hyaluronan transport capabilities functionally. Results: CFTR specific siRNA inhibited hyaluronan export. The tetrasaccharide was exported in undegraded form only from normal human epithelial cells and not from human epithelial cells carrying ΔF508 CFTR. The CFTR inhibitors GlyH-101 and CFTR₁₇₂ reduced hyaluronan export from CFTR-expressing mouse fibroblasts and from human breast cancer cell lines. Bronchial secretions from patients with cystic fibrosis that consist mainly of necrotic epithelia contained at least 40-fold higher concentration of hyaluronan than secretions from patients with acute bronchitis. Conclusions: CFTR transports hyaluronan across the plasma membrane of epithelial cells and this transport mechanism is defective in cystic fibrosis patients.

Filamentous Bacteriophage Promote Biofilm Assembly and Function

“…While performing unrelated experiments that involved supplementing cultures of P. aeruginosa with hyaluronan (HA), a host glycosaminoglycan present in CF airways and abundant in inflamed tissues (Gill et al, 2010; Schulz et al, 2010), we observed the formation of morphologically complex biofilms composed of interlaced structures (Figure 1A and B). The addition of hyaluronidase (HA’ase) dissolved these structures (Figure S1A and B), indicating that HA was essential for their formation.…”

Regulation of cell volume by glycosaminoglycans

“…Export from epithelial cells through CFTR can be inhibited by GlyH101 which clogs the channel from outside and thus does not interfere with the intracellular metabolism [Muanprasat et al, 2004;Schulz et al, 2010]. We inhibited hyaluronan export by zaprinast from mouse fibroblasts, and by GlyH101 from MRP5-deficient mouse fibroblast and a human breast cancer cells that both express the CFTR channel.…”

Hypertonic Saline in Treatment of Pulmonary Disease in Cystic Fibrosis

“…In addition, elevated concentrations of anionic glycosaminoglycans (GAGs) have been found in mucus samples from children with CF [33] (Figure 2). For example, significantly increased bronchial levels of hyaluronic acid have been reported [34], with sputum concentrations 100-fold higher than in acute bronchitis. Moreover, CF sputum has been shown to contain significantly elevated levels of chondroitin [35] and heparan sulphate [36] and in vitro enzymatic digestion of GAGs with chondroitinase ABC rather than protein digestion with trypsin decreased viscoelasticity of CF purulent sputa [37].…”