A bacterial site 2 protease contributes to RNA phage resistance by targeting phage lysis protein

Read the full article See related articles

Listed in

This article is not in any list yet, why not save it to one of your lists.
Log in to save this article

Abstract

Lytic phages culminate their lifecycle by causing lysis of the infected host cell. Despite extensive research on the molecular mechanisms of phage lysis, our understanding of anti-phage resistance mechanisms during the lysis stage remains less understood. Here, we demonstrated that MucP, a site 2 protease of Pseudomonas aeruginosa (PA), mitigates the activity of the RNA phage PP7 lysis protein (LP), which contains a transmembrane (TM) helix, suggesting that MucP act as a resistance mechanism against PP7-induced lysis. We identified an LP variant (LP*) having enhanced helical propensity due to P26L and S40L mutations, which was unaffected by MucP and exhibited killing activity against PA strains that are resistant to the wild type LP, with an inverse correlation between MucP activity and LP susceptibility. A PP7 mutant with LP* exhibited MucP-escaper phenotype such as discernable plaque formation on MucP-expressing cells. These results suggest that MucP targets the RNA phage LP at the TM helix in certain strains, providing a resistance function compromising phage lysis by utilizing an existing bacterial enzyme in PA.

SIGNIFICANCE

Host cell lysis is the last step of the phage lifecycle, occurring only when the progeny virions reach a certain number. The factors influencing coordinated lysis have not been well-studied, particularly in the context of the evolutionary arms race between phages and their hosts. Our study identifies MucP, a membrane protease in Pseudomonas aeruginosa (PA), as a resistance mechanism against the RNA phage PP7 by destabilizing its lysis protein (LP), which has lower helical tendency at the transmembrane (TM) domain. An LP variant with higher helical tendency exhibits strong killing activity against PA strains normally resistant to LP-mediated killing, revealing an inverse correlation between MucP activity and LP susceptibility in various PA clinical stains. Given that MucP is a conserved protease critical for mucoid conversion in PA, we propose that MucP offers a phage resistance mechanism or an intrinsic or nonprofessional defense mechanism against the RNA phages, which varies among the phenotypically diverse PA isolates.

SYNOPSIS

  • Pseudomonas aeruginosa MucP, a site 2 protease, destabilizes the PP7 lysis protein (LP).

  • Helical propensity of the LP transmembrane domain affects MucP-susceptibility.

  • Clinical strains with higher MucP activity exhibit greater LP and RNA phage resistance.

  • PP7* with MucP-resistant LP* shows broadened spectrum with no less reduced infectivity.

Abstract Figure

Article activity feed