scholarly journals A type VII secretion system in Group B Streptococcus mediates cytotoxicity and virulence

2021 ◽  
Author(s):  
Brady L Spencer ◽  
Uday Tak ◽  
Jéssica C Mendonça ◽  
Prescilla E Nagao ◽  
Michael Niederweis ◽  
...  
Keyword(s):  
Group B Streptococcus ◽  
Bioinformatic Analysis ◽  
Secretion System ◽  
Effector Proteins ◽  
Brain Endothelium ◽  
Secretion Systems ◽  
Gram Positive Bacteria ◽  
Type Vii Secretion ◽  
Type Vii Secretion System ◽  
Group B

Type VII secretion systems (T7SS) have been identified in Actinobacteria and Firmicutes and have been shown to secrete effector proteins with functions in virulence, host toxicity, or interbacterial killing in a few genera. Bioinformatic analysis indicates that Group B streptococcal (GBS) isolates encode four distinct subtypes of T7SS machinery, three of which encode adjacent putative T7SS effectors with WXG and LXG motifs. However, the function of T7SS in GBS pathogenesis is not known. Here we show that the most abundant GBS T7SS subtype is important for virulence and cytotoxicity in brain endothelium and that these phenotypes are dependent on the WXG100 effector EsxA. We further show that the WXG motif is required for cytotoxicity in brain endothelium and that EsxA is a pore-forming protein. This work reveals the importance of a T7SS in host-GBS interactions and has implications for the functions of T7SS effectors in other Gram-positive bacteria.

scholarly journals A type VII secretion system in Group B Streptococcus mediates cytotoxicity and virulence

2021 ◽  
Vol 17 (12) ◽  
pp. e1010121
Author(s):  
Brady L. Spencer ◽  
Uday Tak ◽  
Jéssica C. Mendonça ◽  
Prescilla E. Nagao ◽  
Michael Niederweis ◽  
...  
Keyword(s):  
Group B Streptococcus ◽  
Bioinformatic Analysis ◽  
Effector Proteins ◽  
Dependent Manner ◽  
Secretion Systems ◽  
Gram Positive Bacteria ◽  
Type Vii Secretion ◽  
Type Vii Secretion System ◽  
Group B

Type VII secretion systems (T7SS) have been identified in Actinobacteria and Firmicutes and have been shown to secrete effector proteins with functions in virulence, host toxicity, and/or interbacterial killing in a few genera. Bioinformatic analysis indicates that isolates of Group B Streptococcus (GBS) encode at least four distinct subtypes of T7SS machinery, three of which encode adjacent putative T7SS effectors with WXG and LXG motifs. However, the function of T7SS in GBS pathogenesis is unknown. Here we assessed the role of the most abundant GBS T7SS subtype during GBS pathogenesis. In a murine model of hematogenous meningitis, mice infected with GBS lacking a functional T7SS or lacking the secreted WXG100 effector EsxA exhibited less mortality, lower bacterial burdens in tissues, and decreased inflammation in the brain compared to mice infected with the parental GBS strain. We further showed that this T7SS induces cytotoxicity in brain endothelium and that EsxA contributes to these cytotoxicity phenotypes in a WXG motif-dependent manner. Finally, we determined that EsxA is a pore-forming protein, thus demonstrating the first role for a non-mycobacterial EsxA homolog in pore formation. This work reveals the importance of a T7SS in host–GBS interactions and has implications for T7SS effector function in other Gram-positive bacteria.

scholarly journals A type VII secretion system of Streptococcus gallolyticus subsp. gallolyticus contributes to gut colonization and the development of colon tumors

2021 ◽  
Vol 17 (1) ◽  
pp. e1009182
Author(s):  
John Culver Taylor ◽  
Xinsheng Gao ◽  
Juan Xu ◽  
Michael Holder ◽  
Joseph Petrosino ◽  
...  
Keyword(s):  
Bacterial Culture ◽  
Secretion System ◽  
Host Cells ◽  
Secretion Systems ◽  
Colon Tumors ◽  
Type Vii Secretion ◽  
Streptococcus Gallolyticus ◽  
Gut Colonization ◽  
Type Vii Secretion System

Streptococcus gallolyticus subspecies gallolyticus (Sgg) has a strong clinical association with colorectal cancer (CRC) and actively promotes the development of colon tumors. However, the molecular determinants involved in Sgg pathogenicity in the gut are unknown. Bacterial type VII secretion systems (T7SS) mediate pathogen interactions with their host and are important for virulence in pathogenic mycobacteria and Staphylococcus aureus. Through genome analysis, we identified a locus in Sgg strain TX20005 that encodes a putative type VII secretion system (designated as SggT7SST05). We showed that core genes within the SggT7SST05 locus are expressed in vitro and in the colon of mice. Western blot analysis showed that SggEsxA, a protein predicted to be a T7SS secretion substrate, is detected in the bacterial culture supernatant, indicating that this SggT7SST05 is functional. Deletion of SggT7SST05 (TX20005Δesx) resulted in impaired bacterial adherence to HT29 cells and abolished the ability of Sgg to stimulate HT29 cell proliferation. Analysis of bacterial culture supernatants suggest that SggT7SST05-secreted factors are responsible for the pro-proliferative activity of Sgg, whereas Sgg adherence to host cells requires both SggT7SST05-secreted and bacterial surface-associated factors. In a murine gut colonization model, TX20005Δesx showed significantly reduced colonization compared to the parent strain. Furthermore, in a mouse model of CRC, mice exposed to TX20005 had a significantly higher tumor burden compared to saline-treated mice, whereas those exposed to TX20005Δesx did not. Examination of the Sgg load in the colon in the CRC model suggests that SggT7SST05-mediated activities are directly involved in the promotion of colon tumors. Taken together, these results reveal SggT7SST05 as a previously unrecognized pathogenicity determinant for Sgg colonization of the colon and promotion of colon tumors.

scholarly journals ESX secretion system: The gatekeepers of mycobacterial survivability and pathogenesis

2020 ◽  
Author(s):  
Sadhana Roy ◽  
Debika Ghatak ◽  
Payel Das ◽  
Somdeb BoseDasgupta
Keyword(s):  
Metal Ion ◽  
Current Knowledge ◽  
Ion Homeostasis ◽  
Secretion System ◽  
Special Focus ◽  
Host Immune System ◽  
Secretion Systems ◽  
Metal Ion Homeostasis ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

AbstractMycobacterium tuberculosis, the causative agent of Tuberculosis has plagued humankind for ages and has surfaced stronger than ever with the advent of drug resistance. Mycobacteria are adept at evading the host immune system and establishing infection by engaging host factors and secreting several virulence factors. Hence these secretion systems play a key role in mycobacterial pathogenesis. The type VII secretion system or ESX (early secretory antigenic target (ESAT6) secretion) system is one such crucial system that comprises five different pathways having distinct roles in mycobacterial proliferation, pathogenesis, cytosolic escape within macrophages, regulation of macrophage apoptosis, metal ion homeostasis, etc. ESX 1–5 systems are implicated in the secretion of a plethora of proteins, of which only a few are functionally characterized. Here we summarize the current knowledge of ESX secretion systems of mycobacteria with a special focus on ESX-1 and ESX-5 systems that subvert macrophage defenses and help mycobacteria to establish their niche within the macrophage.

scholarly journals Structure of the extracellular region of the bacterial type VIIb secretion system subunit EsaA

2020 ◽  
Author(s):  
Timothy A. Klein ◽  
Dirk W. Grebenc ◽  
Shil Y. Gandhi ◽  
Vraj S. Shah ◽  
Youngchang Kim ◽  
...  
Keyword(s):  
Structural Information ◽  
Cell Envelope ◽  
Critical Role ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Type Vii Secretion ◽  
Streptococcus Gallolyticus ◽  
Extracellular Region

SummaryGram-positive bacteria use type VII secretion systems (T7SSs) to export effector proteins that manipulate the physiology of nearby prokaryotic and eukaryotic cells. Several mycobacterial T7SSs have established roles in virulence. By contrast, recent work has demonstrated that the genetically distinct T7SSb pathway found in Firmicutes bacteria more often functions to mediate interbacterial competition. A lack of structural information on the T7SSb has limited the understanding of effector export by this protein secretion apparatus. In this work, we present the 2.4Å crystal structure of the extracellular region of the elusive T7SSb subunit EsaA from Streptococcus gallolyticus. Our structure reveals that homodimeric EsaA is an elongated, arrow-shaped protein with a surface-accessible ‘tip’, which serves as a receptor for lytic bacteriophages in some species of bacteria. Because it is the only T7SSb subunit large enough to traverse the thick peptidoglycan layer of Firmicutes bacteria, we propose that EsaA plays a critical role in transporting effectors across the entirety of the Gram-positive cell envelope.

scholarly journals Structure of the mycobacterial ESX-5 type VII secretion system pore complex

2021 ◽  
Vol 7 (26) ◽  
pp. eabg9923
Author(s):  
Katherine S. H. Beckham ◽  
Christina Ritter ◽  
Grzegorz Chojnowski ◽  
Daniel S. Ziemianowicz ◽  
Edukondalu Mullapudi ◽  
...  
Keyword(s):  
Fundamental Principle ◽  
Secretion System ◽  
Dynamic State ◽  
Secretion Systems ◽  
Type Vii Secretion ◽  
High Resolution Structure ◽  
Conformational Plasticity ◽  
Type Vii Secretion System ◽  
Membrane Spanning ◽  
Bacterial Secretion

The ESX-5 type VII secretion system is a membrane-spanning protein complex key to the virulence of mycobacterial pathogens. However, the overall architecture of the fully assembled translocation machinery and the composition of the central secretion pore have remained unknown. Here, we present the high-resolution structure of the 2.1-megadalton ESX-5 core complex. Our structure captured a dynamic, secretion-competent conformation of the pore within a well-defined transmembrane section, sandwiched between two flexible protein layers at the cytosolic entrance and the periplasmic exit. We propose that this flexibility endows the ESX-5 machinery with large conformational plasticity required to accommodate targeted protein secretion. Compared to known secretion systems, a highly dynamic state of the pore may represent a fundamental principle of bacterial secretion machineries.

scholarly journals EsaB is a core component of the Staphylococcus aureus Type VII secretion system

2017 ◽  
Author(s):  
M. Guillermina Casabona ◽  
Grant Buchanan ◽  
Martin Zoltner ◽  
Catriona P. Harkins ◽  
Matthew T.G. Holden ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Fluorescent Protein ◽  
Iron Acquisition ◽  
Yellow Fluorescent Protein ◽  
Secretion System ◽  
Secretion Systems ◽  
Core Component ◽  
Type Vii Secretion ◽  
Bacterial Competition ◽  
Type Vii Secretion System

AbstractType VII secretion systems (T7SS) are found in many bacteria and secrete proteins involved in virulence and bacterial competition. In Staphylococcus aureus the small ubiquitin-like EsaB protein has been previously implicated as having a regulatory role in the production of the EsxC substrate. Here we show that in the S. aureus RN6390 strain, EsaB does not genetically regulate production of any T7 substrates or components, but is indispensable for secretion activity. Consistent with EsaB being a core component of the T7SS, loss of either EsaB or EssC are associated with upregulation of a common set of iron acquisition genes. However, a further subset of genes were dysregulated only in the absence of EsaB. In addition, fractionation revealed that although an EsaB fusion to yellow fluorescent protein partially localised to the membrane, it was still membrane-localised when the T7SS was absent. Taken together our findings suggest that EsaB has T7SS-dependent and T7SS-independent roles in S. aureus.

scholarly journals The beneficial rhizobacterium Bacillus velezensis acquires iron from roots via a type VII secretion system for colonization

2021 ◽  
Author(s):  
Yunpeng Liu ◽  
Xia Shu ◽  
Lin Chen ◽  
Huihui Zhang ◽  
Haichao Feng ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Root Colonization ◽  
Secretion System ◽  
Root Cell ◽  
Plant Colonization ◽  
Secretion Systems ◽  
Bacillus Velezensis ◽  
Root Cells ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

Niche colonization is the key for bacterial adaptation to the environment, and competition for iron largely determines root colonization by rhizosphere microbes. Pathogenic and beneficial symbiotic bacteria use various unique secretion systems to support plant colonization or acquire limited resources from the environment. However, ubiquitous nonsymbiotic beneficial rhizobacteria have never been reported to use a unique secretion system to facilitate colonization. Here, we show that the type VII secretion system (T7SS) of the beneficial rhizobacterium Bacillus velezensis SQR9 contributes to root colonization. Knocking out T7SS and the major secreted protein YukE in SQR9 caused a significant decrease in root colonization. Moreover, the T7SS and YukE caused iron loss in plant roots in the early stage after inoculation, which contributed to root colonization by SQR9. Interestingly, purified YukE, but not inactivated YukE, could change the permeability of root cells. We speculated that secreted YukE might be directly inserted into the root cell membrane to cause iron leakage, indicating that the bacterial protein and root cell membrane interact directly. Moreover, a bacterial siderophore and the T7SS may be coordinately involved in iron acquisition by B. velezensis SQR9 for efficient root colonization. We showed that the beneficial rhizobacterium B. velezensis SQR9 could acquire iron from roots via the T7SS for rapid colonization. These findings provide the first insight into the function of the unique secretion system in nonsymbiotic beneficial rhizobacteria and reveal a novel mutualism in which plants and bacteria might share iron in a sequential manner.

scholarly journals Rerouting of an Esx substrate pair from the ESX-1 type VII secretion system to ESX-5 by modifying a PE/PPE substrate pair

2020 ◽  
Author(s):  
Merel P.M. Damen ◽  
Trang H. Phan ◽  
Roy Ummels ◽  
Alba Rubio-Canalejas ◽  
Wilbert Bitter ◽  
...  
Keyword(s):  
Secretion System ◽  
Extracellular Proteins ◽  
Secretion Systems ◽  
Secretion Pathway ◽  
Type Vii Secretion ◽  
Wide Range ◽  
Type Vii Secretion System ◽  
Chaperone Binding ◽  
Determining Factor ◽  
Determinant Factor

AbstractType VII secretion systems (T7SSs) secrete a wide range of extracellular proteins that play important roles in bacterial viability and in host-pathogen interactions of pathogenic mycobacteria. There are five subtypes of mycobacterial T7SSs, called ESX-1 to ESX-5, and four classes of T7SS substrates, namely the Esx, PE, PPE and Esp proteins. At least some of these substrates are secreted as heterodimers. The ESX systems mediate the secretion of specific members of the Esx, PE and PPE proteins, raising the question how these substrates are recognized in a system-specific fashion. PE/PPE heterodimers interact with their cognate EspG chaperones, which recently has been shown to determine their designated secretion pathway. Both structural and pulldown analysis suggest that EspG is unable to interact with Esx proteins and therefore the determining factor for system-specificity of these substrates remains unknown. In this study, we have investigated the secretion specificity of the ESX-1 substrate pair EsxB_1/EsxA_1 (MMAR_0187/MMAR _0188) in Mycobacterium marinum. While this substrate pair was hardly secreted when ectopically expressed, secretion was observed when EsxB_1/EsxA_1 was co-expressed together with PE35/PPE68_1 (MMAR_0185/MMAR_0186), which are encoded by the same operon. Surprisingly, co-expressing EsxB_1/EsxA_1 with a modified PE35/PPE68_1 version that carried the EspG5 chaperone binding domain, previously shown to redirect this substrate pair to the ESX-5 system, also resulted in co-secretion of EsxB_1/EsxA_1 via ESX-5. Our data suggest a secretion model in which PE35/PPE68_1 is a determinant factor for the system-specific secretion of EsxB_1/EsxA_1.

scholarly journals Characterization of Staphylococcus aureus EssB, an integral membrane component of the Type VII secretion system: atomic resolution crystal structure of the cytoplasmic segment

2012 ◽  
Vol 449 (2) ◽  
pp. 469-477 ◽  
Author(s):  
Martin Zoltner ◽  
Paul K. Fyfe ◽  
Tracy Palmer ◽  
William N. Hunter
Keyword(s):  
Staphylococcus Aureus ◽  
Protein Interactions ◽  
Protein Translocation ◽  
Secretion System ◽  
Full Length ◽  
Protein Protein Interactions ◽  
Gram Positive Bacteria ◽  
Type Vii Secretion ◽  
Early Secretory Antigenic Target ◽  
Type Vii Secretion System

The Type VII protein translocation/secretion system, unique to Gram-positive bacteria, is a key virulence determinant in Staphylococcus aureus. We aim to characterize the architecture of this secretion machinery and now describe the present study of S. aureus EssB, a 52 kDa bitopic membrane protein essential for secretion of the ESAT-6 (early secretory antigenic target of 6 kDa) family of proteins, the prototypic substrate of Type VII secretion. Full-length EssB was heterologously expressed in Escherichia coli, solubilized from the bacterial membrane, purified to homogeneity and shown to be dimeric. A C-terminal truncation, EssB∆C, and two soluble fragments termed EssB-N and EssB-C, predicted to occur on either side of the cytoplasmic membrane, have been successfully purified in a recombinant form, characterized and, together with the full-length protein, used in crystallization trials. EssB-N, the 25 kDa N-terminal cytoplasmic fragment, gave well-ordered crystals and we report the structure, determined by SAD (single-wavelength anomalous diffraction) targeting an SeMet (selenomethionine) derivative, refined to atomic (1.05 Å; 1 Å=0.1 nm) resolution. EssB-N is dimeric in solution, but crystallizes as a monomer and displays a fold comprised of two globular domains separated by a cleft. The structure is related to that of serine/threonine protein kinases and the present study identifies that the Type VII secretion system exploits and re-uses a stable modular entity and fold that has evolved to participate in protein–protein interactions in a similar fashion to the catalytically inert pseudokinases.

scholarly journals Mycobacterial ESX-1 secretion system mediates host cell lysis through bacterium contact-dependent gross membrane disruptions

2017 ◽  
Vol 114 (6) ◽  
pp. 1371-1376 ◽  
Author(s):  
William H. Conrad ◽  
Morwan M. Osman ◽  
Jonathan K. Shanahan ◽  
Frances Chu ◽  
Kevin K. Takaki ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Host Cell ◽  
Cell Membranes ◽  
Secretion System ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Vii Secretion ◽  
Membrane Lysis ◽  
Type Vii Secretion System ◽  
Host Cell Membranes

Mycobacterium tuberculosisandMycobacterium marinumare thought to exert virulence, in part, through their ability to lyse host cell membranes. The type VII secretion system ESX-1 [6-kDa early secretory antigenic target (ESAT-6) secretion system 1] is required for both virulence and host cell membrane lysis. Both activities are attributed to the pore-forming activity of the ESX-1–secreted substrate ESAT-6 because multiple studies have reported that recombinant ESAT-6 lyses eukaryotic membranes. We too find ESX-1 ofM. tuberculosisandM. marinumlyses host cell membranes. However, we find that recombinant ESAT-6 does not lyse cell membranes. The lytic activity previously attributed to ESAT-6 is due to residual detergent in the preparations. We report here that ESX-1–dependent cell membrane lysis is contact dependent and accompanied by gross membrane disruptions rather than discrete pores. ESX-1–mediated lysis is also morphologically distinct from the contact-dependent lysis of other bacterial secretion systems. Our findings suggest redirection of research to understand the mechanism of ESX-1–mediated lysis.

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