Pseudomonas aeruginosa protease IV degrades surfactant proteins and inhibits surfactant host defense and biophysical functions.
Pulmonary surfactant has two distinct functions within the lung: reduction of surface tension at the air-liquid interface and participation in innate host defense. Both functions are dependent on surfactant-associated proteins. Pseudomonas aeruginosa is primarily responsible for respiratory dysfunction and death in cystic fibrosis patients and is also a leading pathogen in nosocomial pneumonia. P. aeruginosa secretes a number of proteases that contribute to its virulence. We hypothesized that P. aeruginosa protease IV degrades surfactant proteins and results in a reduction in pulmonary surfactant host defense and biophysical functions. Protease IV was isolated from cultured supernatant of P. aeruginosa by gel chromatography. Incubation of cell-free bronchoalveolar lavage fluid with protease IV resulted in degradation of surfactant proteins (SP)-A, -D, and -B. SPs were degraded in a time- and dose-dependent fashion by protease IV, and degradation was inhibited by the trypsin-like serine protease inhibitor Nalpha-p-tosyl-L-lysine-chloromethyl ketone (TLCK). Degradation by protease IV inhibited SP-A- and SP-D-mediated bacterial aggregation and uptake by macrophages. Surfactant treated with protease IV was unable to reduce surface tension as effectively as untreated surfactant, and this effect was inhibited by TLCK. We speculate that protease IV may be an important contributing factor to the development and propagation of acute lung injury associated with P. aeruginosa via loss of surfactant function within the lung.
Malloy
Jaret L
JL
Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
Veldhuizen
Ruud A W
RA
Thibodeaux
Brett A
BA
O'Callaghan
Richard J
RJ
Wright
Jo Rae
JR
D000595:Amino Acid Sequence; D000818:Animals; D001422:Bacterial Adhesion / Q000187:drug effects; D055592:Biophysical Phenomena; D001703:Biophysics; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D016466:CHO Cells; D002449:Cell Aggregation / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004926:Escherichia coli / Q000502:physiology; D007107:Immune System / Q000187:drug effects*; D016676:Macrophages, Alveolar / Q000382:microbiology; D008297:Male; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000235:genetics / Q000494:pharmacology*; D010743:Phospholipids / Q000378:metabolism / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D037662:Pulmonary Surfactant-Associated Protein A / Q000187:drug effects / Q000378:metabolism*; D037663:Pulmonary Surfactant-Associated Protein D / Q000187:drug effects / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000276:immunology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012486:Salmonella typhimurium / Q000502:physiology
D010743:Phospholipids; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D010447:Peptide Hydrolases; C030732:protease IV