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DOI: 10.1055/s-2006-933907
Mucosal antimicrobial peptides accumulate in airway mucins
Antimicrobial peptides (AMPs) and mucins are components of the airway secretions and both contribute to the innate host defense system of the lung. One of the prominent physical features of AMPs is their strong positive charge at neutral pH. Mucins are macromolecular molecules with heavily glycosylated side chains containing sialic acid and N-acetylgalactosamine-6-sulfate that determine their strong negative charge. It was the aim of the study to test whether these opposite charges result in interactions between the two classes of molecules. We used a lectin based assay to measure binding of mucins isolated from porcine gastric mucosa to the cathelicidin LL-37 coated to multiwell plates and found that LL-37 electrostatically interacts with mucins. To test whether this interaction impacts on the functions of the AMP we used an antimicrobial assay studying the survival of Pseudomonas aeruginosa and Streptococcus pneumoniae in the presence of mucins and LL-37 at different concentrations. Addition of mucins to solutions of LL-37 significantly decreased the antimicrobial activity of the peptide. We then tested whether LL-37 is bound to mucins in airway secretions from human subjects and found that a significant proportion of the peptide and its propeptide is bound to high-molecular weight components. Together these data show that cationic AMPs interact with anionic mucins in airway secretions. Functions of AMPs are modulated by this interaction.