EssC is a specificity determinant for Staphylococcus aureus type VII secretion

Jäger, Franziska; Kneuper, Holger; Palmer, Tracy

doi:10.1099/mic.0.000650

Cited by 28 publications

(39 citation statements)

References 35 publications

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“…Our results are in line with a study that suggested that a segment comprising domains D2 or D3 targets EsxB, EsxC, and EsxD, whereas EsxA binds elsewhere (29). Secretion of the small Esx substrates also requires chaperone EsaE by a yet unknown mechanism (18).…”

Section: Discussionsupporting

confidence: 92%

“…Analyses of S. aureus genomes revealed four alleles of EssC with sequence variations in the 3=-terminal region (4). Experiments in which four EssC alleles were swapped showed that secretion of EsxC but not EsxA depends on the variable C-terminal segment of EssC encompassing part of domain D2 and the entire domain D3, suggesting that EsxC is targeted to this C-terminal region of EssC for secretion while EsxA binds elsewhere (29).…”

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confidence: 99%

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Substrate Interaction with the EssC Coupling Protein of the Type VIIb Secretion System

et al. 2020

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Staphylococcus aureus employs the type VIIb secretion system (T7SSb) to secrete effector proteins that either have antibacterial activities or promote bacterial persistence in mouse infection models. Here, we present the crystal structure of the ATPase domain D3 of the EssC coupling protein from S. aureus USA300_FPR3757, an integral component of the T7SSb complex, resolved at a 1.7-Å resolution. EssC-D3 shares structural homology with FtsK/SpoIII-like ATPase domains of T7SSa and T7SSb and exhibits a conserved pocket on the surface with differential amino acid composition. In T7SSa, substrate EsxB interacts with the D3 domain through this pocket. Here, we identify amino acids in this pocket that are essential for effector protein secretion in the T7SSb. Our results reveal that the adjacent ATPase domain D2 is a substrate binding site on EssC and that substrates bound to D2 require domain D3 for further transport. Point mutations in the Walker B motif of domain D3 have diametric effects on secretion activity, either abolishing or boosting it, pointing to a critical role of domain D3 in the substrate transport. Finally, we identify ATPase domain D3 as a virulence determinant of S. aureus USA300_FPR3757 using an invertebrate in vivo infection model. IMPORTANCE The emergence of antibiotic-resistant bacteria poses a rising problem in antibiotic treatment (S. Boyle-Vavra and R. S. Daum, Lab Invest 87:3–9, 2007, https://doi.org/10.1038/labinvest.3700501). We have used the multidrug-resistant S. aureus USA300_FPR3757 as a model organism to study the T7SSb. Effector proteins of this system have been associated with abscess formation and bacterial persistence in mouse models (M. L. Burts, A. C. DeDent, and D. M. Missiakas, Mol Microbiol 69:736–746, 2008, https://doi.org/10.1111/j.1365-2958.2008.06324.x; M. L. Burts, W. A. Williams, K. DeBord, and D. M. Missiakas, Proc Natl Acad Sci U S A 102:1169–1174, 2005, https://doi.org/10.1073/pnas.0405620102). We determined the structure of the essential ATPase domain D3 of the T7SSb at atomic resolution and validated a surface-exposed pocket as a potential drug target to block secretion. Furthermore, our study provides new mechanistic insights into the T7SSb substrate transport.

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Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Substrate Interaction with the EssC Coupling Protein of the Type VIIb Secretion System

et al. 2020

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“…5), and displayed an increased membrane permeability in presence of LA. However, as all the T7SS mutants showed increased sensitivity to FA, it seems counterintuitive that LA incorporation was impacted more in ΔesxC than in ΔessC given the central role of EssC in T7 secretion [11][12][13] . In the incorporation experiments which were performed in presence of low non-inhibitory LA concentration (10 µM), it is possible that EsxC that accumulates in the membrane ( Supplementary Fig.…”

Section: Discussionmentioning

confidence: 99%

The type VII secretion system protects Staphylococcus aureus against antimicrobial host fatty acids

Tchoupa

Watkins

Jones

et al. 2020

Sci Rep

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The Staphylococcus aureus type VII secretion system (T7SS) exports several proteins that are pivotal for bacterial virulence. The mechanisms underlying T7SS-mediated staphylococcal survival during infection nevertheless remain unclear. Here we report that S. aureus lacking T7SS components are more susceptible to host-derived antimicrobial fatty acids. Unsaturated fatty acids such as linoleic acid (LA) elicited an increased inhibition of S. aureus mutants lacking T7SS effectors EsxC, EsxA and EsxB, or the membrane-bound ATPase EssC, compared to the wild-type (WT). T7SS mutants generated in different S. aureus strain backgrounds also displayed an increased sensitivity to LA. Analysis of bacterial membrane lipid profiles revealed that the esxC mutant was less able to incorporate LA into its membrane phospholipids. Although the ability to bind labelled LA did not differ between the WT and mutant strains, LA induced more cell membrane damage in the T7SS mutants compared to the WT. Furthermore, proteomic analyses of WT and mutant cell fractions revealed that, in addition to compromising membranes, T7SS defects induce oxidative stress and hamper their response to LA challenge. Thus, our findings indicate that T7SS contribute to maintaining S. aureus membrane integrity and homeostasis when bacteria encounter antimicrobial fatty acids.

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“…system (73,74). The EccC-related protein EssC SA (75,76) includes a twin-FHA domain that is essential for secretion (77). FHA domains also mediate oligomerization (78)(79)(80).…”

Section: Figmentioning

confidence: 99%

EspM Is a Conserved Transcription Factor That Regulates Gene Expression in Response to the ESX-1 System

Sanchez

Ferrell

Chirakos

et al. 2020

mBio

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Pathogenic mycobacteria encounter multiple environments during macrophage infection. Temporally, the bacteria are engulfed into the phagosome, lyse the phagosomal membrane, and interact with the cytosol before spreading to another cell. Virulence factors secreted by the mycobacterial ESX-1 (ESAT-6-system-1) secretion system mediate the essential transition from the phagosome to the cytosol. It was recently discovered that the ESX-1 system also regulates mycobacterial gene expression in Mycobacterium marinum (R. E. Bosserman, T. T. Nguyen, K. G. Sanchez, A. E. Chirakos, et al., Proc Natl Acad Sci U S A 114:E10772–E10781, 2017, https://doi.org/10.1073/pnas.1710167114), a nontuberculous mycobacterial pathogen, and in the human-pathogenic species M. tuberculosis (A. M. Abdallah, E. M. Weerdenburg, Q. Guan, R. Ummels, et al., PLoS One 14:e0211003, 2019, https://doi.org/10.1371/journal.pone.0211003). It is not known how the ESX-1 system regulates gene expression. Here, we identify the first transcription factor required for the ESX-1-dependent transcriptional response in pathogenic mycobacteria. We demonstrate that the gene divergently transcribed from the whiB6 gene and adjacent to the ESX-1 locus in mycobacterial pathogens encodes a conserved transcription factor (MMAR_5438, Rv3863, now espM). We prove that EspM from both M. marinum and M. tuberculosis directly and specifically binds the whiB6-espM intergenic region. We show that EspM is required for ESX-1-dependent repression of whiB6 expression and for the regulation of ESX-1-associated gene expression. Finally, we demonstrate that EspM functions to fine-tune ESX-1 activity in M. marinum. Taking the data together, this report extends the esx-1 locus, defines a conserved regulator of the ESX-1 virulence pathway, and begins to elucidate how the ESX-1 system regulates gene expression. IMPORTANCE Mycobacterial pathogens use the ESX-1 system to transport protein substrates that mediate essential interactions with the host during infection. We previously demonstrated that in addition to transporting proteins, the ESX-1 secretion system regulates gene expression. Here, we identify a conserved transcription factor that regulates gene expression in response to the ESX-1 system. We demonstrate that this transcription factor is functionally conserved in M. marinum, a pathogen of ectothermic animals; M. tuberculosis, the human-pathogenic species that causes tuberculosis; and M. smegmatis, a nonpathogenic mycobacterial species. These findings provide the first mechanistic insight into how the ESX-1 system elicits a transcriptional response, a function of this protein transport system that was previously unknown.

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EssC is a specificity determinant for Staphylococcus aureus type VII secretion

Cited by 28 publications

References 35 publications

Substrate Interaction with the EssC Coupling Protein of the Type VIIb Secretion System

Substrate Interaction with the EssC Coupling Protein of the Type VIIb Secretion System

The type VII secretion system protects Staphylococcus aureus against antimicrobial host fatty acids

EspM Is a Conserved Transcription Factor That Regulates Gene Expression in Response to the ESX-1 System

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