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Imelio JA, Trajtenberg F, Mondino S, Zarantonelli L, Vitrenko I, Lemée L, Cokelaer T, Picardeau M, Buschiazzo A. Signal-sensing triggers the shutdown of HemKR, regulating heme and iron metabolism in the spirochete Leptospira biflexa. PLoS One 2024; 19:e0311040. [PMID: 39325783 PMCID: PMC11426443 DOI: 10.1371/journal.pone.0311040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2024] [Accepted: 09/11/2024] [Indexed: 09/28/2024] Open
Abstract
Heme and iron metabolic pathways are highly intertwined, both compounds being essential for key biological processes, yet becoming toxic if overabundant. Their concentrations are exquisitely regulated, including via dedicated two-component systems (TCSs) that sense signals and regulate adaptive responses. HemKR is a TCS present in both saprophytic and pathogenic Leptospira species, involved in the control of heme metabolism. However, the molecular means by which HemKR is switched on/off in a signal-dependent way, are still unknown. Moreover, a comprehensive list of HemKR-regulated genes, potentially overlapped with iron-responsive targets, is also missing. Using the saprophytic species Leptospira biflexa as a model, we now show that 5-aminolevulinic acid (ALA) triggers the shutdown of the HemKR pathway in live cells, and does so by stimulating the phosphatase activity of HemK towards phosphorylated HemR. Phospho~HemR dephosphorylation leads to differential expression of multiple genes, including of heme metabolism and transport systems. Besides the heme-biosynthetic genes hemA and the catabolic hmuO, which we had previously reported as phospho~HemR targets, we now extend the regulon identifying additional genes. Finally, we discover that HemR inactivation brings about an iron-deficit tolerant phenotype, synergistically with iron-responsive signaling systems. Future studies with pathogenic Leptospira will be able to confirm whether such tolerance to iron deprivation is conserved among Leptospira spp., in which case HemKR could play a vital role during infection where available iron is scarce. In sum, HemKR responds to abundance of porphyrin metabolites by shutting down and controlling heme homeostasis, while also contributing to integrate the regulation of heme and iron metabolism in the L. biflexa spirochete model.
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Affiliation(s)
- Juan Andrés Imelio
- Laboratory of Molecular & Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Felipe Trajtenberg
- Laboratory of Molecular & Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Sonia Mondino
- Laboratory of Molecular & Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | | | - Iakov Vitrenko
- Plateforme Technologique Biomics, C2RT, Institut Pasteur, Université Paris Cité, Paris, France
| | - Laure Lemée
- Plateforme Technologique Biomics, C2RT, Institut Pasteur, Université Paris Cité, Paris, France
| | - Thomas Cokelaer
- Plateforme Technologique Biomics, C2RT, Institut Pasteur, Université Paris Cité, Paris, France
- Bioinformatics and Biostatistics Hub, Institut Pasteur, Paris, France
| | - Mathieu Picardeau
- Biology of Spirochetes Unit, Institut Pasteur, Université Paris Cité, Paris, France
| | - Alejandro Buschiazzo
- Laboratory of Molecular & Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Dept of Microbiology, Institut Pasteur, Université Paris Cité, Paris, France
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Hoque NJ, Weinert EE. Control of bacterial second messenger signaling and motility by heme-based direct oxygen-sensing proteins. Curr Opin Microbiol 2023; 76:102396. [PMID: 37864983 DOI: 10.1016/j.mib.2023.102396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/15/2023] [Accepted: 09/21/2023] [Indexed: 10/23/2023]
Abstract
Bacteria sense and respond to their environment, allowing them to maximize their survival and growth under changing conditions, such as oxygen levels. Direct oxygen-sensing proteins allow bacteria to rapidly sense concentration changes and adapt by regulating signaling pathways and/or cellular machinery. Recent work has identified roles for direct oxygen-sensing proteins in controlling second messenger levels and motility machinery, as well as effects on biofilm formation, virulence, and motility. In this review, we discuss recent progress in understanding O2-dependent regulation of cyclic di-GMP signaling and motility and highlight the emerging importance in controlling bacterial physiology and behavior.
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Affiliation(s)
- Nushrat J Hoque
- Department of Chemistry, Penn State University, University Park, PA 16802, USA
| | - Emily E Weinert
- Department of Chemistry, Penn State University, University Park, PA 16802, USA; Department of Biochemistry & Molecular Biology, Penn State University, University Park, PA 16802, USA.
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Stuffle EC, Suzuki T, Orillard E, Watts KJ. The Aer2 chemoreceptor from Vibrio vulnificus is a tri-PAS-heme oxygen sensor. Mol Microbiol 2023; 119:59-73. [PMID: 36420630 PMCID: PMC10107281 DOI: 10.1111/mmi.15007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/25/2022]
Abstract
The marine pathogen Vibrio vulnificus senses and responds to environmental stimuli via two chemosensory systems and 42-53 chemoreceptors. Here, we present an analysis of the V. vulnificus Aer2 chemoreceptor, VvAer2, which is the first V. vulnificus chemoreceptor to be characterized. VvAer2 is related to the Aer2 receptors of other gammaproteobacteria, but uncharacteristically contains three PAS domains (PAS1-3), rather than one or two. Using an E. coli chemotaxis hijack assay, we determined that VvAer2, like other Aer2 receptors, senses and responds to O2 . All three VvAer2 PAS domains bound pentacoordinate b-type heme and exhibited similar O2 affinities. PAS2 and PAS3 both stabilized O2 via conserved Iβ-Trp residues, but PAS1, which was easily oxidized in vitro, was unaffected by Iβ-Trp replacement. Our results support a model in which PAS1 is largely dispensable for O2 -mediated signaling, whereas PAS2 modulates PAS3 signaling, and PAS3 signals to the downstream domains. Each PAS domain appeared to be positionally optimized, because PAS swapping caused altered signaling properties, and neither PAS1 nor PAS2 could replace PAS3. Our findings strengthen previous conclusions that Aer2 receptors are O2 sensors, but with distinct N-terminal domain arrangements that facilitate, modulate and tune responses based on environmental signals.
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Affiliation(s)
- Erwin C Stuffle
- Division of Microbiology and Molecular Genetics, Loma Linda University, California, Loma Linda, USA
| | - Tise Suzuki
- Division of Biochemistry, Loma Linda University, California, Loma Linda, USA
| | - Emilie Orillard
- College of Health Sciences, Western University of Health Sciences, California, Pomona, USA
| | - Kylie J Watts
- Division of Microbiology and Molecular Genetics, Loma Linda University, California, Loma Linda, USA
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New Roles for HAMP Domains: the Tri-HAMP Region of Pseudomonas aeruginosa Aer2 Controls Receptor Signaling and Cellular Localization. J Bacteriol 2022; 204:e0022522. [PMID: 35916529 PMCID: PMC9487508 DOI: 10.1128/jb.00225-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Aer2 chemoreceptor from Pseudomonas aeruginosa is an O2 sensor involved in stress responses, virulence, and tuning the behavior of the chemotaxis (Che) system. Aer2 is the sole receptor of the Che2 system. It is soluble, but membrane associated, and forms complexes at the cell pole during stationary phase. The domain arrangement of Aer2 is unusual, with a PAS sensing domain sandwiched between five HAMP domains, followed by a C-terminal kinase-control output domain. The first three HAMP domains form a poly-HAMP chain N-terminal to the PAS sensing domain. HAMP domains are often located between signal input and output domains, where they transduce signals. Given that HAMP1 to 3 reside N-terminal to the input-output pathway, we undertook a systematic examination of their function in Aer2. We found that HAMP1 to 3 influence PAS signaling over a considerable distance, as the majority of HAMP1, 2 and 3 mutations, and deletions of helical phase stutters, led to nonresponsive signal-off or off-biased receptors. PAS signal-on lesions that mimic activated Aer2 also failed to override N-terminal HAMP signal-off replacements. This indicates that HAMP1 to 3 are critical coupling partners for PAS signaling and likely function as a cohesive unit and moveable scaffold to correctly orient and poise PAS dimers for O2-mediated signaling in Aer2. HAMP1 additionally controlled the clustering and polar localization of Aer2 in P. aeruginosa. Localization was not driven by HAMP1 charge, and HAMP1 signal-off mutants still localized. Employing HAMP as a clustering and localization determinant, as well as a facilitator of PAS signaling, are newly recognized roles for HAMP domains. IMPORTANCE P. aeruginosa is an opportunistic pathogen that interprets environmental stimuli via 26 chemoreceptors that signal through 4 distinct chemosensory systems. The second chemosensory system, Che2, contains a receptor named Aer2 that senses O2 and mediates stress responses and virulence and tunes chemotactic behavior. Aer2 is membrane associated, but soluble, and has three N-terminal HAMP domains (HAMP1 to 3) that reside outside the signal input-output pathway of Aer2. In this study, we determined that HAMP1 to 3 facilitate O2-dependent signaling from the PAS sensing domain and that HAMP1 controls the formation of Aer2-containing polar foci in P. aeruginosa. Both of these are newly recognized roles for HAMP domains that may be applicable to other non-signal-transducing HAMP domains and poly-HAMP chains.
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