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Vrla GD, Esposito M, Zhang C, Kang Y, Seyedsayamdost MR, Gitai Z. Cytotoxic alkyl-quinolones mediate surface-induced virulence in Pseudomonas aeruginosa. PLoS Pathog 2020; 16:e1008867. [PMID: 32925969 PMCID: PMC7515202 DOI: 10.1371/journal.ppat.1008867] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 09/24/2020] [Accepted: 08/04/2020] [Indexed: 12/28/2022] Open
Abstract
Surface attachment, an early step in the colonization of multiple host environments, activates the virulence of the human pathogen P. aeruginosa. However, the downstream toxins that mediate surface-dependent P. aeruginosa virulence remain unclear, as do the signaling pathways that lead to their activation. Here, we demonstrate that alkyl-quinolone (AQ) secondary metabolites are rapidly induced upon surface association and act directly on host cells to cause cytotoxicity. Surface-induced AQ cytotoxicity is independent of other AQ functions like quorum sensing or PQS-specific activities like iron sequestration. We further show that packaging of AQs in outer-membrane vesicles (OMVs) increases their cytotoxicity to host cells but not their ability to stimulate downstream quorum sensing pathways in bacteria. OMVs lacking AQs are significantly less cytotoxic, suggesting these molecules play a role in OMV cytotoxicity, in addition to their previously characterized role in OMV biogenesis. AQ reporters also enabled us to dissect the signal transduction pathways downstream of the two known regulators of surface-dependent virulence, the quorum sensing receptor, LasR, and the putative mechanosensor, PilY1. Specifically, we show that PilY1 regulates surface-induced AQ production by repressing the AlgR-AlgZ two-component system. AlgR then induces RhlR, which can induce the AQ biosynthesis operon under specific conditions. These findings collectively suggest that the induction of AQs upon surface association is both necessary and sufficient to explain surface-induced P. aeruginosa virulence. Pseudomonas aeruginosa is one of the most intensely studied bacterial pathogens and is a leading cause of hospital-acquired infections in the United States. An intriguing aspect of P. aeruginosa is its ability increase its virulence following attachment to a solid surface, suggesting that these bacteria use mechano-transduction to regulate pathogenesis. However, the cytotoxins that mediate host-cell killing in response to surface attachment remain unknown. Here, we use a microscopy-based host-cell killing assay to show that the alkyl-quinolone (AQ) family of secreted small molecules is both necessary and sufficient to explain surface-induced virulence. We further show that these compounds are upregulated rapidly following bacterial surface attachment and that packaging of AQs into secreted outer membrane vesicles enhances AQ cytotoxicity. This work thus fills a major gap in our understanding of surface sensing in P. aeruginosa and provides new methods for investigating surface-dependent signaling pathways.
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Affiliation(s)
- Geoffrey D. Vrla
- Department of Molecular Biology, Princeton University, Princeton, NJ, Unites States of America
| | - Mark Esposito
- Department of Molecular Biology, Princeton University, Princeton, NJ, Unites States of America
| | - Chen Zhang
- Department of Chemistry, Princeton University, Princeton, NJ, Unites States of America
| | - Yibin Kang
- Department of Molecular Biology, Princeton University, Princeton, NJ, Unites States of America
| | | | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, NJ, Unites States of America
- * E-mail:
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Abstract
In the pathogen Pseudomonas aeruginosa, LasR is a quorum sensing (QS) master regulator that senses the concentration of secreted autoinducers as a proxy for bacterial cell density. Counterintuitively, previous studies showed that saturating amounts of the LasR ligand, 3OC12-HSL, fail to induce the full LasR regulon in low-density liquid cultures. Here we demonstrate that surface association, which is necessary for many of the same group behaviors as QS, promotes stronger QS responses. We show that lasR is upregulated upon surface association, and that surface-associated bacteria induce LasR targets more strongly in response to autoinducer than planktonic cultures. This increased sensitivity may be due to surface-dependent lasR induction initiating a positive feedback loop through the small RNA, Lrs1. The increased sensitivity of surface-associated cells to QS is affected by the type IV pilus (TFP) retraction motors and the minor pilins. The coupling of physical surface responses and chemical QS responses could enable these bacteria to trigger community behaviors more robustly when they are more beneficial.
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Affiliation(s)
- Sara K Chuang
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08540, USA
| | - Geoffrey D Vrla
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08540, USA
| | - Kathrin S Fröhlich
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08540, USA
- Department of Biology I, Microbiology, Ludwig-Maximilians-University Munich, D-82152, Martinsried, Germany
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08540, USA.
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Fica-Contreras SM, Shuster SO, Durfee ND, Bowe GJK, Henning NJ, Hill SA, Vrla GD, Stillman DR, Suralik KM, Sandwick RK, Choi S. Glycation of Lys-16 and Arg-5 in amyloid-β and the presence of Cu 2+ play a major role in the oxidative stress mechanism of Alzheimer's disease. J Biol Inorg Chem 2017; 22:1211-1222. [PMID: 29038915 DOI: 10.1007/s00775-017-1497-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Accepted: 10/09/2017] [Indexed: 01/21/2023]
Abstract
Extensive research has linked the amyloid-beta (Aβ) peptide to neurological dysfunction in Alzheimer's disease (AD). Insoluble Aβ plaques in the AD patient brain contain high concentrations of advanced glycation end-products (AGEs) as well as transition metal ions. This research elucidated the roles of Aβ, sugars, and Cu2+ in the oxidative stress mechanism of AD at the molecular level. Mass spectral (MS) analysis of the reactions of Aβ with two representative sugars, ribose-5-phosphate (R5P) and methylglyoxal (MG), revealed Lys-16 and Arg-5 as the primary glycation sites. Quantitative analysis of superoxide [Formula: see text] production by a cyt c assay showed that Lys-16 generated four times as much [Formula: see text] as Arg-5. Lys-16 and Arg-5 in Aβ1-40 are both adjacent to histidine residues, which are suggested to catalyze glycation. Additionally, Lys-16 is close to the central hydrophobic core (Leu-17-Ala-21) and to His-13, both of which are known to lower the pKa of the residue, leading to increased deprotonation of the amine and an enhanced glycation reactivity compared to Arg-5. Gel electrophoresis results indicated that all three components of AD plaques-Aβ1-40, sugars, and Cu2+-are necessary for DNA damage. It is concluded that the glycation of Aβ1-40 with sugars generates significant amounts of [Formula: see text], owing to the rapid glycation of Lys-16 and Arg-5. In the presence of Cu2+, [Formula: see text] converts to hydroxyl radical (HO·), the source of oxidative stress in AD.
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Affiliation(s)
| | - Sydney O Shuster
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Nathaniel D Durfee
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Gregory J K Bowe
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Nathaniel J Henning
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Staci A Hill
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Geoffrey D Vrla
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - David R Stillman
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Kelly M Suralik
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Roger K Sandwick
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA
| | - Sunhee Choi
- Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT, 05753, USA.
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Win Z, Vrla GD, Steucke KE, Sevcik EN, Hald ES, Alford PW. Smooth muscle architecture within cell-dense vascular tissues influences functional contractility. Integr Biol (Camb) 2014; 6:1201-10. [DOI: 10.1039/c4ib00193a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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