Mechanistic Insights into Elastin Degradation by Pseudolysin, the Major Virulence Factor of the Opportunistic Pathogen Pseudomonas aeruginosa

Abstract

Pseudolysin is the most abundant protease secreted by Pseudomonas aeruginosa and is the major extracellular virulence factor of this opportunistic human pathogen. Pseudolysin destroys human tissues by solubilizing elastin. However, the mechanisms by which pseudolysin binds to and degrades elastin remain elusive. In this study, we investigated the mechanism of action of pseudolysin on elastin binding and degradation by biochemical assay, microscopy and site-directed mutagenesis. Pseudolysin bound to bovine elastin fibers and preferred to attack peptide bonds with hydrophobic residues at the P1 and P1’ positions in the hydrophobic domains of elastin. The time-course degradation processes of both bovine elastin fibers and cross-linked human tropoelastin by pseudolysin were further investigated by microscopy. Altogether, the results indicate that elastin degradation by pseudolysin began with the hydrophobic domains on the fiber surface, followed by the progressive disassembly of macroscopic elastin fibers into primary structural elements. Moreover, our site-directed mutational results indicate that five hydrophobic residues in the S1-S1’ sub-sites played key roles in the binding of pseudolysin to elastin. This study sheds lights on the pathogenesis of P. aeruginosa infection.

Thrombospondin-1 protects against pathogen-induced lung injury by limiting extracellular matrix proteolysis

“…Platelet-derived proteins including TSP-1 are found in the airspaces of ARDS patients and correlate with composite injury scores (23), but how they facilitate the course of inflammation and injury has been poorly understood. Certain microbes such as P. aeruginosa can trigger a cascade of injury and cell death through the release of exoproducts such as LPS, flagellin, exotoxins, lipases, and proteases, produce breakage of tight junctional gaps, degrade extracellular matrix proteins that constitute the basement membrane, and potentially cause alveolar barrier disruption that is the hallmark of lung injury (51)(52)(53)(54)(55)(56)(57). The host protects against aggressive lung injury triggered by infection through the release of soluble factors from injured blood vessels and platelets.…”

Pseudomonas aeruginosa in Chronic Lung Infections: How to Adapt Within the Host?

“…The PA proteases are most studied for their ability to cause direct tissue damage, and they are primarily known as virulence factors involved in the pathogenesis of acute infections. LasB, a broad specificity metallo-protease, degrades elastin ( 55 ), disrupts epithelial tight-junctions ( 56 ), and reduce endothelial barrier integrity ( 57 , 58 ). As a consequence, LasB mutants are attenuated in virulence in experimental models of bacteremia ( 59 ), acute pneumonia ( 60 ), or burn wound model ( 61 ).…”

Effect of Human Burn Wound Exudate on Pseudomonas aeruginosa Virulence

“…Among the major virulence factors produced, the blue pigment pyocyanin triggers proinflammatory activity ( 8 ) and the QS-independent regulated pigment pyoverdine is a siderophore involved in iron chelation and acquisition ( 9 ). There is also the secreted protease elastase, which mainly contributes to the destruction of elastin, a component of the host tissues ( 10 ). The major complications due to P. aeruginosa infections are observed in organisms with compromised natural defenses.…”