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Ostan NKH, Cole GB, Wang FZ, Reichheld SE, Moore G, Pan C, Yu R, Lai CCL, Sharpe S, Lee HO, Schryvers AB, Moraes TF. A secreted bacterial protein protects bacteria from cationic antimicrobial peptides by entrapment in phase-separated droplets. PNAS NEXUS 2024; 3:pgae139. [PMID: 38633880 PMCID: PMC11022072 DOI: 10.1093/pnasnexus/pgae139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 03/26/2024] [Indexed: 04/19/2024]
Abstract
Mammalian hosts combat bacterial infections through the production of defensive cationic antimicrobial peptides (CAPs). These immune factors are capable of directly killing bacterial invaders; however, many pathogens have evolved resistance evasion mechanisms such as cell surface modification, CAP sequestration, degradation, or efflux. We have discovered that several pathogenic and commensal proteobacteria, including the urgent human threat Neisseria gonorrhoeae, secrete a protein (lactoferrin-binding protein B, LbpB) that contains a low-complexity anionic domain capable of inhibiting the antimicrobial activity of host CAPs. This study focuses on a cattle pathogen, Moraxella bovis, that expresses the largest anionic domain of the LbpB homologs. We used an exhaustive biophysical approach employing circular dichroism, biolayer interferometry, cross-linking mass spectrometry, microscopy, size-exclusion chromatography with multi-angle light scattering coupled to small-angle X-ray scattering (SEC-MALS-SAXS), and NMR to understand the mechanisms of LbpB-mediated protection against CAPs. We found that the anionic domain of this LbpB displays an α-helical secondary structure but lacks a rigid tertiary fold. The addition of antimicrobial peptides derived from lactoferrin (i.e. lactoferricin) to the anionic domain of LbpB or full-length LbpB results in the formation of phase-separated droplets of LbpB together with the antimicrobial peptides. The droplets displayed a low rate of diffusion, suggesting that CAPs become trapped inside and are no longer able to kill bacteria. Our data suggest that pathogens, like M. bovis, leverage anionic intrinsically disordered domains for the broad recognition and neutralization of antimicrobials via the formation of biomolecular condensates.
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Affiliation(s)
- Nicholas K H Ostan
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Gregory B Cole
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Flora Zhiqi Wang
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Sean E Reichheld
- Molecular Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Gaelen Moore
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Chuxi Pan
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Ronghua Yu
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada
| | | | - Simon Sharpe
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
- Molecular Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Hyun O Lee
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Anthony B Schryvers
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
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Transferrin Binding Protein B and Transferrin Binding Protein A2 Expand the Transferrin Recognition Range of Histophilus somni. J Bacteriol 2020; 202:JB.00177-20. [PMID: 32366593 DOI: 10.1128/jb.00177-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 04/24/2020] [Indexed: 01/04/2023] Open
Abstract
The bacterial bipartite transferrin receptor is an iron acquisition system that several important human and animal pathogens require for survival. It consists of the TonB-dependent transporter transferrin binding protein A (TbpA) and the surface lipoprotein transferrin binding protein B (TbpB). Curiously, the Tbps are only found in host-specific pathogens and are themselves host specific, meaning that they will bind to the transferrin of their host species but not to the transferrins of other animal species. While this phenomenon has long been established, neither the steps in the evolutionary process that led to this exquisite adaptation for the host nor the steps that could alter it are known. We sought to gain insight into these processes by studying Tbp specificity in Histophilus somni, an economically important pathogen of cattle. A past study showed that whole cells of H. somni specifically bind bovine transferrin but not transferrin from sheep and goats, two bovids whose transferrins share 93% amino acid sequence identity with bovine transferrin. To our surprise, we found that H. somni can use sheep and goat transferrins as iron sources for growth and that HsTbpB, but not HsTbpA, has detectable affinity for sheep and goat transferrins. Furthermore, a third transferrin binding protein found in H. somni, HsTbpA2, also showed affinity for sheep and goat transferrins. Our results suggest that H. somni TbpB and TbpA2 may contribute to broadening the host transferrin recognition range of H. somni IMPORTANCE Host-restricted pathogens infect a single host species or a narrow range of host species. Histophilus somni, a pathogen that incurs severe economic losses for the cattle industry, infects cattle, sheep, and goats but not other mammals. The transferrin binding proteins, TbpA and TbpB, are thought to be a key iron acquisition system in H. somni; however, despite their importance, H. somni TbpA and TbpB were previously shown to be cattle transferrin specific. In our study, we find that H. somni TbpB and another little-studied Tbp, TbpA2, bind sheep and goat transferrins, as well as bovine transferrin. Our results suggest that TbpB and TbpA2 may allow for host range expansion and provide a mechanism for how host specificity in Tbp-encoding pathogens can be altered.
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Chen A, Arora PD, Lai CC, Copeland JW, Moraes TF, McCulloch CA, Lavoie BD, Wilde A. The scaffold-protein IQGAP1 enhances and spatially restricts the actin-nucleating activity of Diaphanous-related formin 1 (DIAPH1). J Biol Chem 2020; 295:3134-3147. [PMID: 32005666 DOI: 10.1074/jbc.ra119.010476] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 01/24/2020] [Indexed: 11/06/2022] Open
Abstract
The actin cytoskeleton is a dynamic array of filaments that undergoes rapid remodeling to drive many cellular processes. An essential feature of filament remodeling is the spatio-temporal regulation of actin filament nucleation. One family of actin filament nucleators, the Diaphanous-related formins, is activated by the binding of small G-proteins such as RhoA. However, RhoA only partially activates formins, suggesting that additional factors are required to fully activate the formin. Here we identify one such factor, IQ motif containing GTPase activating protein-1 (IQGAP1), which enhances RhoA-mediated activation of the Diaphanous-related formin (DIAPH1) and targets DIAPH1 to the plasma membrane. We find that the inhibitory intramolecular interaction within DIAPH1 is disrupted by the sequential binding of RhoA and IQGAP1. Binding of RhoA and IQGAP1 robustly stimulates DIAPH1-mediated actin filament nucleation in vitro In contrast, the actin capping protein Flightless-I, in conjunction with RhoA, only weakly stimulates DIAPH1 activity. IQGAP1, but not Flightless-I, is required to recruit DIAPH1 to the plasma membrane where actin filaments are generated. These results indicate that IQGAP1 enhances RhoA-mediated activation of DIAPH1 in vivo Collectively these data support a model where the combined action of RhoA and an enhancer ensures the spatio-temporal regulation of actin nucleation to stimulate robust and localized actin filament production in vivo.
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Affiliation(s)
- Anan Chen
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Pam D Arora
- Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Christine C Lai
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - John W Copeland
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | | | - Brigitte D Lavoie
- Department Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Andrew Wilde
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada; Department Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada.
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Complex formation between the Escherichia coli [NiFe]-hydrogenase nickel maturation factors. Biometals 2019; 32:521-532. [DOI: 10.1007/s10534-019-00173-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/18/2019] [Indexed: 11/26/2022]
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Ostan NKH, Yu RH, Ng D, Lai CCL, Pogoutse AK, Sarpe V, Hepburn M, Sheff J, Raval S, Schriemer DC, Moraes TF, Schryvers AB. Lactoferrin binding protein B - a bi-functional bacterial receptor protein. PLoS Pathog 2017; 13:e1006244. [PMID: 28257520 PMCID: PMC5352143 DOI: 10.1371/journal.ppat.1006244] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 03/15/2017] [Accepted: 02/15/2017] [Indexed: 11/18/2022] Open
Abstract
Lactoferrin binding protein B (LbpB) is a bi-lobed outer membrane-bound lipoprotein that comprises part of the lactoferrin (Lf) receptor complex in Neisseria meningitidis and other Gram-negative pathogens. Recent studies have demonstrated that LbpB plays a role in protecting the bacteria from cationic antimicrobial peptides due to large regions rich in anionic residues in the C-terminal lobe. Relative to its homolog, transferrin-binding protein B (TbpB), there currently is little evidence for its role in iron acquisition and relatively little structural and biophysical information on its interaction with Lf. In this study, a combination of crosslinking and deuterium exchange coupled to mass spectrometry, information-driven computational docking, bio-layer interferometry, and site-directed mutagenesis was used to probe LbpB:hLf complexes. The formation of a 1:1 complex of iron-loaded Lf and LbpB involves an interaction between the Lf C-lobe and LbpB N-lobe, comparable to TbpB, consistent with a potential role in iron acquisition. The Lf N-lobe is also capable of binding to negatively charged regions of the LbpB C-lobe and possibly other sites such that a variety of higher order complexes are formed. Our results are consistent with LbpB serving dual roles focused primarily on iron acquisition when exposed to limited levels of iron-loaded Lf on the mucosal surface and effectively binding apo Lf when exposed to high levels at sites of inflammation.
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Affiliation(s)
- Nicholas K. H. Ostan
- Department of Microbiology & Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Rong-Hua Yu
- Department of Microbiology & Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Dixon Ng
- Department of Microbiology & Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | | | | | - Vladimir Sarpe
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Morgan Hepburn
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Joey Sheff
- Department of Chemistry, University of Calgary, Calgary, Alberta, Canada
| | - Shaunak Raval
- Department of Chemistry, University of Calgary, Calgary, Alberta, Canada
| | - David C. Schriemer
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Trevor F. Moraes
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Anthony B. Schryvers
- Department of Microbiology & Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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