Iron and citrate export by a major facilitator superfamily pump regulates metabolism and stress resistance in<i>Salmonella</i>Typhimurium

Frawley, Elaine R.; Crouch, Marie Laure V; Bingham-Ramos, Lacey K.; Robbins, Hannah F.; Wang, Wenliang; Wright, Gerard D.; Fang, Ferric C.

doi:10.1073/pnas.1218274110

Cited by 89 publications

(90 citation statements)

References 49 publications

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“…However, given the significance of iron to bacterial physiology and the presence of redundant host nutritional defense mechanisms to impose iron limitation both in the extracellular compartment and within phagosomes, our observations that GAS possesses machinery to counter iron toxicity were surprising. Although it is possible that the host also employs iron toxicity as a nutritional immune defense, experimental evidence in this regard is limited (48,49). However, our finding that increased intracellular iron accumulation in the ΔpmtA mutant increases its sensitivity to oxidative stress raises another possibility.…”

Section: Discussionmentioning

confidence: 89%

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

et al. 2017

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Group A Streptococcus (GAS) is a human-only pathogen that causes a spectrum of disease conditions. Given its survival in inflamed lesions, the ability to sense and overcome oxidative stress is critical for GAS pathogenesis. PerR senses oxidative stress and coordinates the regulation of genes involved in GAS antioxidant defenses. In this study, we investigated the role of PerR-controlled metal transporter A (PmtA) in GAS pathogenesis. Previously, PmtA was implicated in GAS antioxidant defenses and suggested to protect against zinc toxicity. Here, we report that PmtA is a P 1B4 -type ATPase that functions as an Fe(II) exporter and aids GAS defenses against iron intoxication and oxidative stress. The expression of pmtA is specifically induced by excess iron, and this induction requires PerR. Furthermore, a pmtA mutant exhibited increased sensitivity to iron toxicity and oxidative stress due to an elevated intracellular accumulation of iron. RNA-sequencing analysis revealed that GAS undergoes significant alterations in gene expression to adapt to iron toxicity. Finally, using two mouse models of invasive infection, we demonstrated that iron efflux by PmtA is critical for bacterial survival during infection and GAS virulence. Together, these data demonstrate that PmtA is a key component of GAS antioxidant defenses and contributes significantly to GAS virulence.KEYWORDS bacterial pathogenesis, gene regulation, iron efflux, metal homeostasis, oxidative stress I ron is a critical micronutrient required for bacterial survival and proliferation due to its role as a cofactor in cellular macromolecules involved in metabolism and electron transport. Given the bacterial requirement for iron, hosts limit iron availability to pathogens by using a variety of extracellular and intracellular mechanisms (1, 2). The eukaryotic host recruits an array of extracellular antimicrobial factors to chelate iron present at the microbial colonization surfaces to retard bacterial growth (2-4). As a countermeasure, pathogens employ high-affinity iron importers and iron-scavenging siderophores to acquire metal ions from nutrient-sparse infection sites (5). Consistent with this, the inactivation of iron importers resulted in an attenuated virulence of several pathogens, underscoring their importance to bacterial pathogenesis (5-7). Emerging evidence indicates that the host also employs metal toxicity at microbial colonization surfaces, predominantly within phagosomes, to mediate microbial killing and control bacterial infection (8,9). Host innate immune cells, such as neutrophils and macrophages, accumulate copper and zinc around phagocytosed bacteria and impose metal toxicity (8-12). Conversely, bacteria employ metal efflux pumps to reduce the intracellular metal concentration and negate host-induced metal toxicity (8,11,12). In

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Section: Discussionmentioning

confidence: 89%

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

et al. 2017

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“…As such, the 5448ΔpmtA deletion mutant, which contained higher levels of intracellular Fe(II) than did the WT strain, grew less efficiently in the presence of hydrogen peroxide and superoxide. Similarly, the Salmonella enterica serovar Typhimurium Fe efflux pump STM3944 mutant was shown to be more sensitive to hydrogen peroxide (45). The PerR regulon in GAS controls a variety of genes involved in the response to hydrogen peroxide stress (5).…”

Section: Discussionmentioning

confidence: 99%

The PerR-Regulated P _1B-4 -Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes

et al. 2017

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Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a broad spectrum of human disease. GAS has a requirement for metal homeostasis within the human host and, as such, tightly modulates metal uptake and efflux during infection. Metal acquisition systems are required to combat metal sequestration by the host, while metal efflux systems are essential to protect against metal overload poisoning. Here, we investigated the function of PmtA (PerRregulated metal transporter A), a P 1B-4 -type ATPase efflux pump, in invasive GAS M1T1 strain 5448. We reveal that PmtA functions as a ferrous iron [Fe(II)] efflux system. In the presence of high Fe(II) concentrations, the 5448ΔpmtA deletion mutant exhibited diminished growth and accumulated 5-fold-higher levels of intracellular Fe(II) than did the wild type and the complemented mutant. The 5448ΔpmtA deletion mutant also showed enhanced susceptibility to killing by the Fe-dependent antibiotic streptonigrin as well as increased sensitivity to hydrogen peroxide and superoxide. We suggest that the PerRmediated control of Fe(II) efflux by PmtA is important for bacterial defense against oxidative stress. PmtA represents an exemplar for an Fe(II) efflux system in a host-adapted Gram-positive bacterial pathogen.KEYWORDS iron efflux, PmtA, oxidative stress response, PerR, group A Streptococcus, Streptococcus pyogenes D efense against peroxide is recognized as one of the most widespread stress responses in prokaryotes. A characteristic of the peroxide stress response is the increased expression of peroxidases that can directly remove hydrogen peroxide as well as the induction of systems that can repair damaged proteins and nucleic acids (1, 2). Streptococcus pyogenes (group A Streptococcus [GAS]) coordinates oxidative stress responses through the action of the regulator PerR, which functions as a repressor of oxidative stress defense genes under normal conditions through binding to DNA at per boxes upstream of these genes (3, 4). This stable complex typically exists with Fe as a prosthetic group; in the presence of hydrogen peroxide, Fe causes metal-catalyzed oxidation and damage of the complex, leading to its dissociation and the subsequent transcription of peroxide response genes (3-6). In GAS, the PerR-regulated oxidative stress response encompasses both direct mechanisms, involving the detoxification of reactive oxygen species (ROS), and indirect mechanisms, which involve the repair of biomolecules damaged by oxidative stress. Direct mechanisms involving the enzymatic detoxification of reactive oxygen species are achieved through alkyl hydroperoxidases and glutathione peroxidases (1, 2, 5) as well as a single superoxide dismutase, SodA, which is Mn dependent (7). An example of an indirect response mechanism is PolAI, a DNA polymerase that repairs oxidatively damaged DNA (8).

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“…For example, the major facilitator family includes the tetracyclinemetal ion transporter TetL in Bacillus subtilis (15) and the iron citrate exporter IceT in Salmonella enterica serovar Typhimurium (16). P-type ATPases, which couple the uptake or efflux of cations to ATP hydrolysis, include the cadmium exporter CadA in Staphylococcus aureus and B. subtilis (17,18) and the copper transporter CopA in Escherichia coli (19).…”

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confidence: 99%

A Ferrous Iron Exporter Mediates Iron Resistance in Shewanella oneidensis MR-1

Bennett

Brutinel

Gralnick

2015

Appl Environ Microbiol

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Shewanella oneidensis strain MR-1 is a dissimilatory metal-reducing bacterium frequently found in aquatic sediments. In the absence of oxygen, S. oneidensis can respire extracellular, insoluble oxidized metals, such as iron (hydr)oxides, making it intimately involved in environmental metal and nutrient cycling. Shewanella oneidensis strain MR-1 is a versatile, facultatively anaerobic bacterium that lives in aquatic environments and is capable of respiring numerous organic and inorganic compounds in the absence of oxygen. The respiratory diversity of S. oneidensis has widespread effects on biogeochemical cycling (1) and has therefore been a focus for applications in biotechnology and bioremediation (2). Terminal electron acceptors that S. oneidensis can use, aside from oxygen, include dimethyl sulfoxide (DMSO), trimethylamine N-oxide, fumarate, nitrate, and sulfite (3-6), as well as oxidized metals, such as iron and manganese (hydr)oxides (3, 7), which are abundant in the types of sediments (8) in which Shewanella spp. are often found (1). The molecular mechanisms that allow dissimilatory metal-reducing bacteria to survive under iron-rich conditions, however, are not fully understood.Respiration of ferric iron (Fe 3ϩ ) results in the production of ferrous iron (Fe 2ϩ ), which can remain as aqueous Fe 2ϩ ions or become incorporated into solid-phase minerals (9, 10), depending on the environmental conditions. As iron respiration by S. oneidensis continues, the local concentration of aqueous Fe 2ϩ may increase, and Fe 2ϩ ions can be taken up by cells through transition metal ion uptake systems, primarily the iron transport complex FeoAB (11). At higher concentrations, however, Fe 2ϩ is toxic to cells. Aerobically, Fe 2ϩ toxicity is thought to be caused by oxidative damage from hydroxyl radicals produced through the Fenton reaction (12), but the cause of damage under anaerobic conditions is not well understood. Several possible causes of anaerobic Fe 2ϩ toxicity have been proposed, such as the production of reactive nitrogen species (13) or inhibition of the F o F 1 ATPase (14). Regardless of the basis for toxicity, microorganisms have evolved means of minimizing the cellular damage caused by high concentrations of Fe 2ϩ and other metal ions. One of the well-characterized mechanisms that microorganisms use to prevent metal toxicity is efflux via membrane transporters. Metal efflux proteins are widespread in all three domains of life and comprise multiple protein families and superfamilies.For example, the major facilitator family includes the tetracyclinemetal ion transporter TetL in Bacillus subtilis (15) and the iron citrate exporter IceT in Salmonella enterica serovar Typhimurium (16). P-type ATPases, which couple the uptake or efflux of cations to ATP hydrolysis, include the cadmium exporter CadA in Staphylococcus aureus and B. subtilis (17,18) and the copper transporter CopA in Escherichia coli (19). To date, however, no proteins mediating Fe 2ϩ resistance have been described in S. oneidensis. A transposon scre...

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Iron and citrate export by a major facilitator superfamily pump regulates metabolism and stress resistance inSalmonellaTyphimurium

Cited by 89 publications

References 49 publications

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

The PerR-Regulated P _1B-4 -Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes

A Ferrous Iron Exporter Mediates Iron Resistance in Shewanella oneidensis MR-1

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Iron and citrate export by a major facilitator superfamily pump regulates metabolism and stress resistance inSalmonellaTyphimurium

Cited by 89 publications

References 49 publications

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence

The PerR-Regulated P 1B-4 -Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes

A Ferrous Iron Exporter Mediates Iron Resistance in Shewanella oneidensis MR-1

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The PerR-Regulated P _1B-4 -Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes