Calprotectin-mediated zinc chelation inhibits Pseudomonas aeruginosa protease activity in cystic fibrosis sputum.
2021 Apr 29;pii: JB.00100-21. doi: 10.1128/JB.00100-21
induces pathways indicative of low zinc availability in the cystic fibrosis (CF) lung environment. To learn more about zinc access in CF, we grew strain PAO1 directly in expectorated CF sputum. The Zur transcriptional repressor controls the response to low intracellular zinc, and we used the NanoString methodology to monitor levels of Zur-regulated transcripts including those encoding a zincophore system, a zinc importer, and paralogs of zinc containing proteins that do not require zinc for activity. Zur-controlled transcripts were induced in sputum-grown compared to control cultures, but not if the sputum was amended with zinc. Amendment of sputum with ferrous iron did not reduce expression of Zur-regulated genes. A reporter fusion to a Zur-regulated promoter had variable activity in grown in sputum from different donors, and this variation inversely correlated with sputum zinc concentrations. Recombinant human calprotectin (CP), a divalent-metal binding protein released by neutrophils, was sufficient to induce a zinc-starvation response in grown in laboratory medium or zinc-amended CF sputum indicating that CP is functional in the sputum environment. Zinc metalloproteases comprise a large fraction of secreted zinc-binding proteins. Here we show that recombinant CP inhibited both LasB-mediated casein degradation and LasA-mediated lysis of , which was reversible with added zinc. These studies reveal the potential for CP-mediated zinc chelation to post-translationally inhibit zinc metalloprotease activity and thereby impact the protease-dependent physiology and/or virulence of in the CF lung environment.The factors that contribute to worse outcomes in individuals with cystic fibrosis (CF) with chronic infections are not well understood. Therefore, there is a need to understand environmental factors within the CF airway that contribute to colonization and infection. We demonstrate that growing bacteria in CF sputum induces a zinc-starvation response that inversely correlates with sputum zinc levels. Additionally, both calprotectin and a chemical zinc chelator inhibit the proteolytic activities of LasA and LasB proteases suggesting that extracellular zinc chelators can influence proteolytic activity and thus virulence and nutrient acquisition .
J Bacteriol|2021 Apr 29