scholarly journals Mycobacterium tuberculosis Toxin CpnT Is an ESX-5 Substrate and Requires Three Type VII Secretion Systems for Intracellular Secretion

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
B. Izquierdo Lafuente ◽  
R. Ummels ◽  
C. Kuijl ◽  
W. Bitter ◽  
A. Speer
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Host Cells ◽  
Secretion Systems ◽  
Macrophage Infection ◽  
Content Type ◽  
Secretion Pathway ◽  
Terminal Domain ◽  
Type Vii Secretion ◽  
Type Vii Secretion System ◽  
Axenic Conditions

ABSTRACT CpnT, a NAD+ glycohydrolase, is the only known toxin that is secreted by Mycobacterium tuberculosis. CpnT is composed of two domains; the C-terminal domain is the toxin, whereas the N-terminal domain is required for secretion. CpnT shows characteristics of type VII secretion (T7S) substrates, including a predicted helix-turn-helix domain followed by a secretion motif (YxxxE). Disruption of this motif indeed abolished CpnT secretion. By analyzing different mutants, we established that CpnT is specifically secreted by the ESX-5 system in Mycobacterium marinum under axenic conditions and during macrophage infection. Surprisingly, intracellular secretion of CpnT was also dependent on both ESX-1 and ESX-4. These secretion defects could be partially rescued by coinfection with wild-type bacteria, indicating that secreted effectors are involved in this process. In summary, our data reveal that three different type VII secretion systems have to be functional in order to observe intracellular secretion of the toxin CpnT. IMPORTANCE For decades, it was believed that the intracellular pathogen M. tuberculosis does not possess toxins. Only fairly recently it was discovered that CpnT is a potent secreted toxin of M. tuberculosis, causing necrotic cell death in host cells. However, until now the secretion pathway remained unknown. In our study, we were able to identify CpnT as a substrate of the mycobacterial type VII secretion system. Pathogenic mycobacteria have up to five different type VII secretion systems, called ESX-1 to ESX-5, which play distinct roles for the pathogen during growth or infection. We were able to elucidate that CpnT is exclusively secreted by the ESX-5 system in bacterial culture. However, to our surprise we discovered that, during infection studies, CpnT secretion relies on intact ESX-1, ESX-4, and ESX-5 systems. We elucidate for the first time the intertwined interplay of three different and independent secretion systems to secrete one substrate during infection.

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 Structure and dynamics of the ESX-5 type VII secretion system of Mycobacterium tuberculosis

2020 ◽  
Author(s):  
Catalin M. Bunduc ◽  
Dirk Fahrenkamp ◽  
Jiri Wald ◽  
Roy Ummels ◽  
Wilbert Bitter ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protein Transport ◽  
Cell Envelope ◽  
Transmembrane Helix ◽  
Transport Systems ◽  
Secretion Systems ◽  
Type Vii Secretion ◽  
Membrane Complex ◽  
Type Vii Secretion System ◽  
Inner Membrane Complex

AbstractMycobacterium tuberculosis causes one of the most important infectious diseases in humans, leading to 1.5 million deaths every year. Specialized protein transport systems, called type VII secretion systems (T7SSs), are central for its virulence, but also crucial for nutrient and metabolite transport across the mycobacterial cell envelope. Here we present the first structure of an intact T7SS inner membrane complex of M. tuberculosis. We show how the 2.32 MDa, 165 transmembrane helices-containing ESX-5 assembly is restructured and stabilized as a trimer of dimers by the MycP5 protease. A trimer of MycP5 caps a central periplasmic dome-like chamber formed by three EccB5 dimers, with the proteolytic sites facing towards the cavity. This chamber suggests a central secretion and processing conduit. Complexes without MycP5 show disruption of the EccB5 periplasmic assembly and increased flexibility, highlighting the importance of this component for complex integrity. Beneath the EccB5-MycP5 chamber, dimers of the EccC5 ATPase assemble into three four-transmembrane helix bundles, which together seal the potential central secretion channel. Individual cytoplasmic EccC5 domains adopt two distinctive conformations, likely reflecting different secretion states. Our work suggests a novel mechanism of protein transport and provides a structural scaffold to aid drug development against the major human pathogen.

scholarly journals WhiB5, a Transcriptional Regulator That Contributes to Mycobacterium tuberculosis Virulence and Reactivation

2012 ◽  
Vol 80 (9) ◽  
pp. 3132-3144 ◽  
Author(s):  
Stefano Casonato ◽  
Axel Cervantes Sánchez ◽  
Hirohito Haruki ◽  
Monica Rengifo González ◽  
Roberta Provvedi ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Chronic Infection ◽  
Null Mutant ◽  
Wild Type ◽  
Secretion Systems ◽  
Content Type ◽  
Type Vii Secretion ◽  
Expression Of Genes ◽  
Genes Encoding

ABSTRACTThe proteins belonging to the WhiB superfamily are small global transcriptional regulators typical of actinomycetes. In this paper, we characterize the role of WhiB5, aMycobacterium tuberculosisprotein belonging to this superfamily. A null mutant was constructed inM. tuberculosisH37Rv and was shown to be attenuated during both progressive and chronic mouse infections. Mice infected with the mutant had smaller bacillary burdens in the lungs but a larger inflammatory response, suggesting a role of WhiB5 in immunomodulation. Most interestingly, thewhiB5mutant was not able to resume growth after reactivation from chronic infection, suggesting that WhiB5 controls the expression of genes involved in this process. The mutant was also more sensitive than the wild-type parental strain toS-nitrosoglutathione (GSNO) and was less metabolically active following prolonged starvation, underscoring the importance of GSNO and starvation in development and maintenance of chronic infection. DNA microarray analysis identified 58 genes whose expression is influenced by WhiB5, includingsigM, encoding an alternative sigma factor, and genes encoding the constituents of two type VII secretion systems, namely, ESX-2 and ESX-4.

scholarly journals Role of Metal-Dependent Regulation of ESX-3 Secretion in Intracellular Survival of Mycobacterium tuberculosis

2016 ◽  
Vol 84 (8) ◽  
pp. 2255-2263 ◽  
Author(s):  
Emir Tinaztepe ◽  
Jun-Rong Wei ◽  
Jenelle Raynowska ◽  
Cynthia Portal-Celhay ◽  
Victor Thompson ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Cell Envelope ◽  
Bacterial Pathogen ◽  
Transcriptional Response ◽  
Secretion Systems ◽  
Content Type ◽  
Type Vii Secretion ◽  
Significant Difference ◽  
Iron And Zinc

More people die every year fromMycobacterium tuberculosisinfection than from infection by any other bacterial pathogen. Type VII secretion systems (T7SS) are used by both environmental and pathogenic mycobacteria to secrete proteins across their complex cell envelope. In the nonpathogenMycobacterium smegmatis, the ESX-1 T7SS plays a role in conjugation, and the ESX-3 T7SS is involved in metal homeostasis. InM. tuberculosis, these secretion systems have taken on roles in virulence, and they also are targets of the host immune response. ESX-3 secretes a heterodimer composed of EsxG (TB9.8) and EsxH (TB10.4), which impairs phagosome maturation in macrophages and is essential for virulence in mice. Given the importance of EsxG and EsxH during infection, we examined their regulation. WithM. tuberculosis, the secretion of EsxG and EsxH was regulated in response to iron and zinc, in accordance with the previously described transcriptional response of theesx-3locus to these metals. While iron regulated theesx-3expression in bothM. tuberculosisandM. smegmatis, there is a significant difference in the dynamics of this regulation. InM. smegmatis, theesx-3locus behaved like other iron-regulated genes such asmbtB. InM. tuberculosis, both iron and zinc modestly repressedesx-3expression. Diminished secretion of EsxG and EsxH in response to these metals altered the interaction ofM. tuberculosiswith macrophages, leading to impaired intracellularM. tuberculosissurvival. Our findings detail the regulatory differences ofesx-3inM. tuberculosisandM. smegmatisand demonstrate the importance of metal-dependent regulation of ESX-3 for virulence inM. tuberculosis.

scholarly journals Comparative Genomics ofesxGenes from Clinical Isolates of Mycobacterium tuberculosis Provides Evidence for Gene Conversion and Epitope Variation

2011 ◽  
Vol 79 (10) ◽  
pp. 4042-4049 ◽  
Author(s):  
Swapna Uplekar ◽  
Beate Heym ◽  
Véronique Friocourt ◽  
Jacques Rougemont ◽  
Stewart T. Cole
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Dna Sequences ◽  
Antigenic Variation ◽  
Clinical Isolates ◽  
Nucleotide Polymorphisms ◽  
Secretion Systems ◽  
Human Immune System ◽  
Single Nucleotide ◽  
Content Type ◽  
Type Vii Secretion

ABSTRACTThe 23-membered Esx protein family is involved in the host-pathogen interactions ofMycobacterium tuberculosis. These secreted proteins are among the most immunodominant antigens recognized by the human immune system and have thus been used to develop vaccines and immunodiagnostic tests for tuberculosis (TB). Gene pairs for 10 Esx proteins are contained in the ESX-1 to ESX-5 loci, encoding type VII secretion systems. A subset of Esx proteins can be further classified into the Mtb9.9, QILSS, and TB10.4 subfamilies. To survey genetic diversity in the Esx family and its potential for antigenic variation, we sequenced allesxgenes from 108 clinical isolates ofM. tuberculosisfrom different clades by using a targeted approach. A total of 109 unique single nucleotide polymorphisms (SNPs) were observed, and 59 of these were nonsynonymous. Some of the resultant amino acid substitutions affect known Esx epitopes, including two in the EsxB (CFP-10) and EsxH (TB10.4) antigens. Assessment of the SNP distribution across the Esx proteins revealed high genetic variability, especially in the Mtb9.9 and QILSS subfamilies, and more conservation in the ESX-1 to ESX-4 loci. Comparison of the DNA sequences of variableesxgenes provided clear evidence for recombination events between different genes in the same strain, some of which are predicted to truncate the corresponding protein. Many of these polymorphisms escape detection by ultrahigh-throughput sequencing using short sequence reads, as such approaches cannot distinguish between closely related genes. Theesxgene family is dynamic, and sequence changes likely lead to immune variation.

scholarly journals CFP-10 from Mycobacterium tuberculosis Selectively Activates Human Neutrophils through a Pertussis Toxin-Sensitive Chemotactic Receptor

2014 ◽  
Vol 83 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Amanda Welin ◽  
Halla Björnsdottir ◽  
Malene Winther ◽  
Karin Christenson ◽  
Tudor Oprea ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Pertussis Toxin ◽  
Human Neutrophils ◽  
Content Type ◽  
Chaperone Function ◽  
Type Vii Secretion ◽  
Chaperone Protein ◽  
Type Vii Secretion System ◽  
G Protein Coupled

Upon infection withMycobacterium tuberculosis, neutrophils are massively recruited to the lungs, but the role of these cells in combating the infection is poorly understood. Through a type VII secretion system,M. tuberculosisreleases a heterodimeric protein complex, containing a 6-kDa early secreted antigenic target (ESAT-6) and a 10-kDa culture filtrate protein (CFP-10), that is essential for virulence. Whereas the ESAT-6 component possesses multiple virulence-related activities, no direct biological activity of CFP-10 has been shown, and CFP-10 has been described as a chaperone protein for ESAT-6. We here show that the ESAT-6:CFP-10 complex induces a transient release of Ca2+from intracellular stores in human neutrophils. Surprisingly, CFP-10 rather than ESAT-6 was responsible for triggering the Ca2+response, in a pertussis toxin-sensitive manner, suggesting the involvement of a G-protein-coupled receptor. In line with this, the response was accompanied by neutrophil chemotaxis and activation of the superoxide-producing NADPH-oxidase. Neutrophils were unique among leukocytes in responding to CFP-10, as monocytes and lymphocytes failed to produce a Ca2+signal upon stimulation with theM. tuberculosisprotein. Hence, CFP-10 may contribute specifically to neutrophil recruitment and activation duringM. tuberculosisinfection, representing a novel biological role for CFP-10 in the ESAT-6:CFP-10 complex, beyond the previously described chaperone function.

scholarly journals The Prophage and Plasmid Mobilome as a Likely Driver of Mycobacterium abscessus Diversity

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Rebekah M. Dedrick ◽  
Haley G. Aull ◽  
Deborah Jacobs-Sera ◽  
Rebecca A. Garlena ◽  
Daniel A. Russell ◽  
...  
Keyword(s):  
Mycobacterium Abscessus ◽  
Genomic Variation ◽  
Host Cells ◽  
Clinical Isolates ◽  
Genetic Constitution ◽  
Secretion Systems ◽  
Emerging Pathogen ◽  
Content Type ◽  
Type Vii Secretion

ABSTRACT Mycobacterium abscessus is an emerging pathogen that is often refractory to antibiotic control. Treatment is further complicated by considerable variation among clinical isolates in both their genetic constitution and their clinical manifestations. Here, we show that the prophage and plasmid mobilome is a likely contributor to this variation. Prophages and plasmids are common, abundant, and highly diverse, and code for large repertoires of genes influencing virulence, antibiotic susceptibility, and defense against viral infection. At least 85% of the strains we describe carry one or more prophages, representing at least 17 distinct and diverse sequence “clusters,” integrated at 18 different attB locations. The prophages code for 19 distinct configurations of polymorphic toxin and toxin-immunity systems, each with WXG-100 motifs for export through type VII secretion systems. These are located adjacent to attachment junctions, are lysogenically expressed, and are implicated in promoting growth in infected host cells. Although the plethora of prophages and plasmids confounds the understanding of M. abscessus pathogenicity, they also provide an abundance of tools for M. abscessus engineering. IMPORTANCE Mycobacterium abscessus is an important emerging pathogen that is challenging to treat with current antibiotic regimens. There is substantial genomic variation in M. abscessus clinical isolates, but little is known about how this influences pathogenicity and in vivo growth. Much of the genomic variation is likely due to the large and varied mobilome, especially a large and diverse array of prophages and plasmids. The prophages are unrelated to previously characterized phages of mycobacteria and code for a diverse array of genes implicated in both viral defense and in vivo growth. Prophage-encoded polymorphic toxin proteins secreted via the type VII secretion system are common and highly varied and likely contribute to strain-specific pathogenesis.

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 Crystallographic observation of the movement of the membrane-distal domain of the T7SS core component EccB1 fromMycobacterium tuberculosis

2016 ◽  
Vol 72 (2) ◽  
pp. 139-144
Author(s):  
Xiao-Qian Xie ◽  
Xiao-Li Zhang ◽  
Chao Qi ◽  
De-Feng Li ◽  
Joy Fleming ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Atpase Activity ◽  
Virulence Factors ◽  
Conformational Changes ◽  
Secretion System ◽  
Secretion Systems ◽  
Core Component ◽  
Substrate Transport ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

The protein EccB1, a core component of the type VII secretion system (T7SS) ofMycobacterium tuberculosis, has been identified as an ATPase and is essential for the secretion of virulence factors by the ESX-1 system. In a previous study, EccB1 structures were determined in two different conformations. Here, two new conformations are identified and described. These four conformations present snapshots of the swinging movement of the membrane-distal domain A2. The movement of this domain involves conformational changes in two flexible loops (loop A, residues 243–264, and loop B, residues 324–341) which are rich in proline and glycine residues and connect domain A2 to domains C1 and B2. It is proposed that the movement of this domain is related to the ATPase activity of EccB1 and its homologues, as well as to the substrate transport of ESX secretion systems.

scholarly journals Modification of a PE/PPE substrate pair reroutes an Esx substrate pair from the mycobacterial ESX-1 type VII secretion system to the ESX-5 system

2020 ◽  
Vol 295 (18) ◽  
pp. 5960-5969 ◽  
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 ◽  
Bacterial Type

Bacterial type VII secretion systems secrete a wide range of extracellular proteins that play important roles in bacterial viability and in interactions of pathogenic mycobacteria with their hosts. Mycobacterial type VII secretion systems consist of five subtypes, ESX-1–5, and have four substrate classes, namely, Esx, PE, PPE, and Esp proteins. At least some of these substrates are secreted as heterodimers. Each ESX system mediates the secretion of a specific set of Esx, PE, and PPE proteins, raising the question of how these substrates are recognized in a system-specific fashion. For the PE/PPE heterodimers, it has been shown that they interact with their cognate EspG chaperone and that this chaperone determines the designated secretion pathway. However, both structural and pulldown analyses have suggested that EspG cannot interact with the Esx proteins. Therefore, the determining factor for system specificity of the Esx proteins remains unknown. Here, we investigated the secretion specificity of the ESX-1 substrate pair EsxB_1/EsxA_1 in Mycobacterium marinum. Although this substrate pair was hardly secreted when homologously expressed, it was secreted when co-expressed together with the PE35/PPE68_1 pair, indicating that this pair could stimulate secretion of the EsxB_1/EsxA_1 pair. Surprisingly, co-expression of 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 redirection and co-secretion of the Esx pair via ESX-5. Our results suggest a secretion model in which PE35/PPE68_1 determines the system-specific secretion of EsxB_1/EsxA_1.

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