The Protease Locus of Francisella tularensis LVS Is Required for Stress Tolerance and Infection in the Mammalian Host

He, Lihong; Nair, Manoj Kumar Mohan; Chen, Yuling; Liu, Xue; Zhang, Mengyun; Hazlett, Karsten R. O.; Deng, Haiteng; Zhang, Jing-Ren

doi:10.1128/iai.00076-16

Cited by 15 publications

(28 citation statements)

References 78 publications

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“…To the best of our knowledge, this study is the first to show that Lon‐2 is critical for animal infection of B. burgdorferi . Despite that Lon homologs have been identified in many microorganisms, the importance of this protein in bacterial fitness and infection has been reported in very few pathogens such as Brucella abortus (Robertson, Kovach, Allen, Ficht, & Roop, ), Salmonella enterica (Takaya et al, ), Francisella tularensis (He et al, ), Yersinia pestis (Herbst et al, ) and Pseudomonas aeruginosa (Breidenstein et al, ). The current study thus expands our understanding about the role of this protease in bacterial pathogenesis.…”

Section: Discussionmentioning

confidence: 99%

The Lon‐2 protease of Borrelia burgdorferi is critical for infection in the mammalian host

Mason

Thompson

Ouyang

2020

Molecular Microbiology

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Borrelia burgdorferi encodes a functional homolog of canonical Lon protease termed Lon-2. To date, the contribution of Lon-2 to B. burgdorferi fitness and infection remains unexplored. Herein, we showed that expression of lon-2 was highly induced during animal infection, suggesting that Lon-2 is important for B. burgdorferi infection. We further generated a lon-2 deletion mutant. Compared with that of wild-type (WT) strain, the infectivity of the mutant was severely attenuated in a murine infection model. Although no growth defect was observed for the mutant in normal BSK-II medium, resistance of the lon-2 mutant to osmotic stress was markedly reduced. In addition, when exposed to tert-Butyl hydroperoxide, survival of the lon-2 mutant was impaired. In addition, we found that the protein levels of RpoS and RpoS-dependent OspC were decreased in the mutant. All these phenotypes were restored to WT or near-WT levels when lon-2 mutation was complemented in cis. Taken together, these results demonstrate that Lon-2 is critical for B. burgdorferi to establish infection and to cope with environmental stresses. This study provides a foundation for further uncovering the direct link between the dual roles of Lon-2 in protein quality control and bacterial pathogenesis.

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Section: Discussionmentioning

confidence: 99%

The Lon‐2 protease of Borrelia burgdorferi is critical for infection in the mammalian host

Mason

Thompson

Ouyang

2020

Molecular Microbiology

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“…Antiserum for recombinant pneumococcal proteins was prepared in New Zealand White rabbits as described previously (64). We first established a protein expression library of pneumococcal genes by individually amplifying coding sequences of target genes from genomic DNA of S. pneumoniae ST556 and cloned behind the glutathione S-transferase (GST) gene in the AscI/NotI site of plasmid pST2700 (65). The inserts of all recombinant plasmids were confirmed by DNA sequencing.…”

Section: Methodsmentioning

confidence: 99%

Novel Immunoprotective Proteins of Streptococcus pneumoniae Identified by Opsonophagocytosis Killing Screen

et al. 2018

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The success of polysaccharide conjugate vaccines represents a major advance in the prevention of pneumococcal disease, but the power of these vaccines is limited by partial spectrum of coverage and high cost. Vaccines using immunoprotective proteins are a promising alternative type of pneumococcal vaccines. In this study, we constructed a library of antisera against conserved pneumococcal proteins predicted to be associated with cell surface or virulence using a combination of bioinformatic prediction and immunization of rabbits with recombinant proteins. Screening of the library by an opsonophagocytosis killing (OPK) assay identified the OPK-positive antisera, which represented 15 (OPK-positive) proteins. Further tests showed that virtually all of these OPK-positive antisera conferred passive protection against lethal infection of virulent pneumococci. More importantly, immunization with recombinant forms of three OPK-positive proteins (SP148, PBP2b, and ScpB), alone or in combination, conferred significant protection against lethal challenge of pneumococcal strains representing capsular serotypes 3, 4, and 6A in a mouse sepsis model. To our best knowledge, this work represents the first example in which novel vaccine candidates are successfully identified by the OPK screening. Our data have also provided further confirmation that the OPK activity may serve as a reliable surrogate for evaluating vaccine efficacy of pneumococcal proteins.

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“…Prior work in E. coli and Pseudomonas protegens suggests that Lon degrades at least one important transcription regulator in each of these organisms (57,58). In LVS, Lon is thought to degrade several virulence-associated factors and has been shown to be important for tolerance to certain stresses (59). Further work will be required to determine whether any of the key regulators of virulence gene expression in F. tularensis, including PigR, MglA, and SspA, serve as the substrates for Lon, or whether Lon might exert regulatory effects in F. tularensis through its ability to interact with the DNA (60,61).…”

Section: Discussionmentioning

confidence: 99%

Polyphosphate Kinase Antagonizes Virulence Gene Expression in Francisella tularensis

2018

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The alarmone ppGpp is a critical regulator of virulence gene expression in In this intracellular pathogen, ppGpp is thought to work in concert with the putative DNA-binding protein PigR and the SspA protein family members MglA and SspA to control a common set of genes. MglA and SspA form a complex that interacts with RNA polymerase (RNAP), and PigR functions by interacting with the RNAP-associated MglA-SspA complex. Prior work suggested that ppGpp indirectly exerts its regulatory effects in by promoting the accumulation of polyphosphate in the cell, which in turn was required for formation of the MglA-SspA complex. Here we show that in , neither polyphosphate nor ppGpp is required for formation of the MglA-SspA complex but that ppGpp promotes the interaction between PigR and the MglA-SspA complex. Moreover, we show that polyphosphate kinase, the enzyme responsible for the synthesis of polyphosphate, antagonizes virulence gene expression in, a finding that is inconsistent with the notion that polyphosphate accumulation promotes virulence gene expression in this organism. Our findings identify polyphosphate kinase as a novel negative regulator of virulence gene expression in and support a model in which ppGpp exerts its positive regulatory effects by promoting the interaction between PigR and the MglA-SspA complex. In , MglA and SspA form a complex that associates with RNA polymerase to positively control the expression of key virulence genes. The MglA-SspA complex works together with the putative DNA-binding protein PigR and the alarmone ppGpp. PigR functions by interacting directly with the MglA-SspA complex, but how ppGpp exerts its effects was unclear. Prior work indicated that ppGpp acts by promoting the accumulation of polyphosphate, which is required for MglA and SspA to interact. Here we show that formation of the MglA-SspA complex does not require polyphosphate. Furthermore, we find that polyphosphate antagonizes the expression of virulence genes in Thus, ppGpp does not promote virulence gene expression in this organism through an effect on polyphosphate.

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The Protease Locus of Francisella tularensis LVS Is Required for Stress Tolerance and Infection in the Mammalian Host

Cited by 15 publications

References 78 publications

The Lon‐2 protease of Borrelia burgdorferi is critical for infection in the mammalian host

The Lon‐2 protease of Borrelia burgdorferi is critical for infection in the mammalian host

Novel Immunoprotective Proteins of Streptococcus pneumoniae Identified by Opsonophagocytosis Killing Screen

Polyphosphate Kinase Antagonizes Virulence Gene Expression in Francisella tularensis

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