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Kirchenwitz M, Halfen J, von Peinen K, Prettin S, Kollasser J, Zur Lage S, Blankenfeldt W, Brakebusch C, Rottner K, Steffen A, Stradal TEB. RhoB promotes Salmonella survival by regulating autophagy. Eur J Cell Biol 2023; 102:151358. [PMID: 37703749 DOI: 10.1016/j.ejcb.2023.151358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/05/2023] [Accepted: 08/29/2023] [Indexed: 09/15/2023] Open
Abstract
Salmonella enterica serovar Typhimurium manipulates cellular Rho GTPases for host cell invasion by effector protein translocation via the Type III Secretion System (T3SS). The two Guanine nucleotide exchange (GEF) mimicking factors SopE and -E2 and the inositol phosphate phosphatase (PiPase) SopB activate the Rho GTPases Rac1, Cdc42 and RhoA, thereby mediating bacterial invasion. S. Typhimurium lacking these three effector proteins are largely invasion-defective. Type III secretion is crucial for both early and later phases of the intracellular life of S. Typhimurium. Here we investigated whether and how the small GTPase RhoB, known to localize on endomembrane vesicles and at the invasion site of S. Typhimurium, contributes to bacterial invasion and to subsequent steps relevant for S. Typhimurium lifestyle. We show that RhoB is significantly upregulated within hours of Salmonella infection. This effect depends on the presence of the bacterial effector SopB, but does not require its phosphatase activity. Our data reveal that SopB and RhoB bind to each other, and that RhoB localizes on early phagosomes of intracellular S. Typhimurium. Whereas both SopB and RhoB promote intracellular survival of Salmonella, RhoB is specifically required for Salmonella-induced upregulation of autophagy. Finally, in the absence of RhoB, vacuolar escape and cytosolic hyper-replication of S. Typhimurium is diminished. Our findings thus uncover a role for RhoB in Salmonella-induced autophagy, which supports intracellular survival of the bacterium and is promoted through a positive feedback loop by the Salmonella effector SopB.
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Affiliation(s)
- Marco Kirchenwitz
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Jessica Halfen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Kristin von Peinen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Silvia Prettin
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Jana Kollasser
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Susanne Zur Lage
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Wulf Blankenfeldt
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Cord Brakebusch
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Klemens Rottner
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany; Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
| | - Anika Steffen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Theresia E B Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
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Wu T, Zhang B, Lu J, Huang A, Wu H, Qiao J, Ruan H. Label-free relative quantitative proteomics reveals extracellular vesicles as a vehicle for Salmonella effector protein delivery. Front Microbiol 2022; 13:1042111. [PMID: 36590436 PMCID: PMC9797957 DOI: 10.3389/fmicb.2022.1042111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 11/02/2022] [Indexed: 12/23/2022] Open
Abstract
Extracellular vesicles are small vesicles with a diameter of 30-150 nm that are actively secreted by eukaryotic cells and play important roles in intercellular communication, immune responses, and tumorigenesis. Previous studies have shown that extracellular vesicles are involved in the process of Salmonella enterica serovar Typhimurium (S. Typhimurium) infection. However, changes in the protein content of extracellular vesicles elicited by S. Typhimurium infection have not been determined. Here, we extracted the extracellular vesicles with high purity from S. Typhimurium-infected Henle-407 cells, a kind of human intestinal epithelial cells, by ultracentrifugation combined with an extracellular vesicles purification kit, and analyzed their protein composition using label-free relative quantitative proteomics. The extracted extracellular vesicles exhibited an oval vesicular structure under electron microscopy, with a mean diameter of 140.4 ± 32.4 nm. The exosomal marker proteins CD9, CD63, and HSP70 were specifically detected. Compared with the uninfected group, nearly 1,234 specifically loaded proteins were uncovered in S. Typhimurium-infected Henle-407 cells. Among them were 409 S. Typhimurium-derived specific proteins, indicating a significant alteration in protein composition of extracellular vesicles by S. Typhimurium infection. Notably, these proteins included 75 secretory proteins and over 300 non-secretory proteins of S. Typhimurium, implicating novel pathways for bacterial protein delivery, although it remains unclear if their loading into extracellular vesicles is active or passive. To investigate the roles of these extracellular proteins, we exemplified the function of SopB, a well-known T3SS effector protein, and showed that the extracellular SopB could be taken up by RAW264.7 macrophages, activating the phosphorylation of Akt. This study provides new insights into the mechanism of Salmonella infection through extracellular vesicles that transport virulence proteins to uninfected neighboring cells to facilitate further infection.
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Affiliation(s)
- Tao Wu
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, China
| | - Biao Zhang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, China
| | - Juane Lu
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, China
| | - Ailin Huang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, China
| | - Hao Wu
- Key Laboratory of Systems Bioengineering, Ministry of Education, Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Jianjun Qiao
- Key Laboratory of Systems Bioengineering, Ministry of Education, Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Haihua Ruan
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, China,*Correspondence: Haihua Ruan,
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Chu BX, Li YN, Liu N, Yuan LX, Chen SY, Zhu YH, Wang JF. Salmonella Infantis Delays the Death of Infected Epithelial Cells to Aggravate Bacterial Load by Intermittent Phosphorylation of Akt With SopB. Front Immunol 2021; 12:757909. [PMID: 34804044 PMCID: PMC8602575 DOI: 10.3389/fimmu.2021.757909] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/19/2021] [Indexed: 11/13/2022] Open
Abstract
Salmonella Infantis has emerged as a major clinical pathogen causing gastroenteritis worldwide in recent years. As an intracellular pathogen, Salmonella has evolved to manipulate and benefit from the cell death signaling pathway. In this study, we discovered that S. Infantis inhibited apoptosis of infected Caco-2 cells by phosphorylating Akt. Notably, Akt phosphorylation was observed in a discontinuous manner: immediately 0.5 h after the invasion, then before peak cytosolic replication. Single-cell analysis revealed that the second phase was only induced by cytosolic hyper-replicating bacteria at 3-4 hpi. Next, Akt-mediated apoptosis inhibition was found to be initiated by Salmonella SopB. Furthermore, Akt phosphorylation increased mitochondrial localization of Bcl-2 to prevent Bax oligomerization on the mitochondrial membrane, maintaining the mitochondrial network homeostasis to resist apoptosis. In addition, S. Infantis induced pyroptosis, as evidenced by increased caspase-1 (p10) and GSDMS-N levels. In contrast, cells infected with the ΔSopB strain displayed faster but less severe pyroptosis and had less bacterial load. The results indicated that S. Infantis SopB-mediated Akt phosphorylation delayed pyroptosis, but aggravated its severity. The wild-type strain also caused more severe diarrhea and intestinal inflammatory damage than the ΔSopB strain in mice. These findings revealed that S. Infantis delayed the cells' death by intermittent activation of Akt, allowing sufficient time for replication, thereby causing more severe inflammation.
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Affiliation(s)
| | | | | | | | | | | | - Jiu-Feng Wang
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, China Agricultural University, Beijing, China
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García-Gil A, Galán-Enríquez CS, Pérez-López A, Nava P, Alpuche-Aranda C, Ortiz-Navarrete V. SopB activates the Akt-YAP pathway to promote Salmonella survival within B cells. Virulence 2019; 9:1390-1402. [PMID: 30103648 PMCID: PMC6177241 DOI: 10.1080/21505594.2018.1509664] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
B cells are a target of Salmonella infection, allowing bacteria survival without inducing pyroptosis. This event is due to downregulation of Nlrc4 expression and lack of inflammasome complex activation, which impairs the secretion of IL-1β. YAP phosphorylation is required for downregulation of Nlrc4 in B cells during Salmonella infection; however, the microorganism’s mechanisms underlying the inhibition of the NLRC4 inflammasome in B cells are not fully understood. Our findings demonstrate that the Salmonella effector SopB triggers a signaling cascade involving PI3K, PDK1 and mTORC2 that activates Akt with consequent phosphorylation of YAP. When we deleted sopB in Salmonella, infected B cells that lack Rictor, or inhibited the signaling cascade using a pharmacological approach, we were able to restore the function of the NLRC4 inflammasome in B cells and the ability to control the infection. Furthermore, B cells from infected mice exhibited activation of Akt and YAP phosphorylation, suggesting that Salmonella also triggers this pathway in vivo. In summary, our data demonstrate that the Salmonella effector inositide phosphate phosphatase SopB triggers the PI3K-Akt-YAP pathway to inhibit the NLRC4 inflammasome in B cells. This study provides further evidence that Salmonella triggers cellular mechanisms in B lymphocytes to manipulate the host environment by turning it into a survival niche to establish a successful infection.
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Affiliation(s)
- Abraham García-Gil
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Carlos Samuel Galán-Enríquez
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Araceli Pérez-López
- b Department of Pediatrics , University of California San Diego , San Diego , CA , USA
| | - Porfirio Nava
- c Departamento de Fisiología , Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Celia Alpuche-Aranda
- d Centro de Investigación Sobre Enfermedades Infecciosa , Instituto Nacional de Salud Pública, SSA , Cuernavaca , México
| | - Vianney Ortiz-Navarrete
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
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Hu GQ, Yang YJ, Qin XX, Qi S, Zhang J, Yu SX, Du CT, Chen W. Salmonella Outer Protein B Suppresses Colitis Development via Protecting Cell From Necroptosis. Front Cell Infect Microbiol 2019; 9:87. [PMID: 31024858 PMCID: PMC6465518 DOI: 10.3389/fcimb.2019.00087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/12/2019] [Indexed: 12/30/2022] Open
Abstract
Salmonella effectors translocated into epithelial cells contribute to the pathogenesis of infection. They mediate epithelial cell invasion and subsequent intracellular replication. However, their functions in vivo have not been well-identified. In this study, we uncovered a role for Salmonella outer protein B (SopB) in modulating necroptosis to facilitate bacteria escape epithelial cell and spread to systemic sites through a Salmonella-induced colitis model. Mice infected with SopB deleted strain ΔsopB displayed increased severity to colitis, reduced mucin expression and increased bacterial translocation. In vitro study, we found there was an increased goblet cell necroptosis following ΔsopB infection. Consistently, mice infected with ΔsopB had a strong upregulation of mixed lineage kinase domain-like (MLKL) phosphorylation. Deletion of MLKL rescued severity of tissue inflammatory, improved mucin2 expression and abolished the increased bacterial translocation in mice infected with ΔsopB. Intriguingly, the expression of sopB in LS174T cells was downregulated. The temporally regulated SopB expression potentially switched the role from epithelial cell invasion to bacterial transmission. Collectively, these results indicated a role for SopB in modulating the onset of necroptosis to increased bacteria pathogenesis and translocated to systemic sites.
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Affiliation(s)
- Gui-Qiu Hu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Yong-Jun Yang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Xiao-Xia Qin
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Shuai Qi
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Jie Zhang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Shui-Xing Yu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Chong-Tao Du
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Wei Chen
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
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Hu GQ, Song PX, Chen W, Qi S, Yu SX, Du CT, Deng XM, Ouyang HS, Yang YJ. Cirtical role for Salmonella effector SopB in regulating inflammasome activation. Mol Immunol 2017; 90:280-286. [PMID: 28846926 DOI: 10.1016/j.molimm.2017.07.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 05/08/2017] [Accepted: 07/19/2017] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Salmonella is known to evolve many mechanisms to avoid or delay inflammasome activation which remain largely unknown. In this study, we investigated whether the SopB protein critical to bacteria virulence capacity was an effector that involved in the regulation of inflammasome activation. METHODS BMDMs from NLRC4-, NLRP3-, caspase-1/-11-, IFI16- and AIM2-deficient mice were pretreated with LPS, and subsequently stimulated with a series of SopB-related strains of Salmonella, inflammasome induced cell death, IL-1β secretion, cleaved caspase-1 production and ASC speckle formation were detected. RESULTS We found that SopB could inhibit host IL-1β secretion, caspase-1 activation and inflammasome induced cell death using a series of SopB-related strains of Salmonella; however the reduction of IL-1β secretion was not dependent on sensor that contain PYD domain, such as NLRP3, AIM2 or IFI16, but dependent on NLRC4. Notably, SopB specifically prevented ASC oligomerization and the enzymatic activity of SopB was responsible for the inflammasome inhibition. Furthermore, inhibition of Akt signaling induced enhanced inflammasome activation. CONCLUSIONS These results revealed a novel role in inhibition of NLRC4 inflammasome for Salmonella effector SopB.
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Affiliation(s)
- Gui-Qiu Hu
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Pei-Xuan Song
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Wei Chen
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Shuai Qi
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Shui-Xing Yu
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Chong-Tao Du
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Xu-Ming Deng
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Hong-Sheng Ouyang
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China
| | - Yong-Jun Yang
- Key Laboratory of Zoonosis, Ministry of Education, College of Animal Medicine, Jilin University, Changchun 130062, China.
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Ruan H, Zhang Z, Tian L, Wang S, Hu S, Qiao JJ. The Salmonella effector SopB prevents ROS-induced apoptosis of epithelial cells by retarding TRAF6 recruitment to mitochondria. Biochem Biophys Res Commun 2016; 478:618-23. [PMID: 27473656 DOI: 10.1016/j.bbrc.2016.07.116] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 07/26/2016] [Indexed: 11/18/2022]
Abstract
Microbial pathogens enter host cells by injecting effector proteins of the Type III secretion system (T3SS), which facilitate pathogen translocation across the host cell membrane. These effector proteins exert their effects by modulating a variety of host innate immune responses, thereby facilitating bacterial replication and systemic infection. Salmonella enterica serovar typhimurium (S.typhimurium) is a clinically important pathogen that causes food poisoning and gastroenteritis. The SopB effector protein of S. typhimurium, encoded by Salmonella pathogenicity islands (SPI)-1 T3SS, protects host epithelial cells from infection-induced apoptosis. However, how SopB influences apoptosis induction remains unclear. Here, we investigated the mechanism of SopB action in host cells. We found that SopB inhibits infection-induced apoptosis by attenuating the production of reactive oxygen species (ROS) in mitochondria, the crucial organelles for apoptosis initiation. Further investigation revealed that SopB binds to cytosolic tumor necrosis factor receptor associated factor 6 (TRAF6) and forms a trap preventing the mitochondrial recruitment of TRAF6, an essential event for ROS generation within mitochondria. By studying the response of Traf6(+/+) and Traf6(-/-)mouse embryonic fibroblasts to S. typhimurium infection, we found that TRAF6 promoted apoptosis by increasing ROS accumulation, which led to increased Bax/Bcl-2 ratio, Bax recruitment to mitochondrial membrane, and release of Cyt c into the cytoplasm. These findings show that SopB suppresses host cell apoptosis by binding to TRAF6 and preventing mitochondrial ROS generation.
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Affiliation(s)
- Haihua Ruan
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, 300134, China.
| | - Zhen Zhang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, 300134, China
| | - Li Tian
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300192, China
| | - Suying Wang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, 300134, China
| | - Shuangyan Hu
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, 300134, China
| | - Jian-Jun Qiao
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300192, China.
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Ruan HH, Li Y, Zhang XX, Liu Q, Ren H, Zhang KS, Zhao H. Identification of TRAF6 as a ubiquitin ligase engaged in the ubiquitination of SopB, a virulence effector protein secreted by Salmonella typhimurium. Biochem Biophys Res Commun 2014; 447:172-7. [PMID: 24704445 DOI: 10.1016/j.bbrc.2014.03.126] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 03/25/2014] [Indexed: 10/25/2022]
Abstract
The phosphoinositide phosphatase SopB is one of the effectors injected by Salmonella typhimurium (S.typhimurium) that diversifies its function through a ubiquitin-dependent differential localization. However, it is unclear which E3 ubiquitin ligase is responsible for ubiquitination of SopB. Based on the E1-E2-E3 trio of enzymes responsible for the ubiquitin activation and translocation to substrate proteins, we constructed an in vitro assay of SopB ubiquitination. Using this assay, we purified an E3 ubiquitin ligase, TRAF6, from the Henle-407 S100 extraction that may be responsible for the ubiquitination of SopB. To investigate the functional correlation of TRAF6, we showed that recombinant TRAF6 specifically ubiquitinates SopB in a dose-dependent manner in vitro. Upon infection, the ubiquitination of SopB was absolutely blocked by TRAF6 deletion, as shown in Traf6(-/-) mouse embryonic fibroblasts (MEFs) compared with Traf6(+/+) MEFs. However, the ectopic expression of TRAF6 in Traf6(-/-) MEFs rescued the two species of ubiquitin-conjugated SopB, which strengthens the role of TRAF6 in SopB ubiquitination. The analysis of E2 revealed that UbcH5c and not other E2 conjugating enzymes are required for TRAF6-mediated SopB ubiquitination both in vitro and in vivo. In summary, these results suggest the relevance of UbcH5c/TRAF6 in SopB during S.typhimurium infection and thereby imply that S.typhimurium has evolved a mechanism of utilizing the host's E3 ubiquitin ligase to modify and modulate the function of its effector protein in order to ensure pathogen and host cell survival.
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Affiliation(s)
- Hai-Hua Ruan
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China.
| | - Ye Li
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China
| | - Xi-Xuan Zhang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China
| | - Qiang Liu
- Institute of Radiation Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin Key Laboratory of Molecular Nuclear Medicine, Tianjin 300192, China
| | - He Ren
- Key Laboratory of Breast Cancer Prevention and Therapy, Tianjin Medical University Cancer Hospital, Tianjin 300071, China
| | - Kun-Sheng Zhang
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China
| | - Hui Zhao
- Tianjin Key Laboratory of Food Science and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China.
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Roblin P, Lebrun P, Rucktooa P, Dewitte F, Lens Z, Receveur-Brechot V, Raussens V, Villeret V, Bompard C. The structural organization of the N-terminus domain of SopB, a virulence factor of Salmonella, depends on the nature of its protein partners. Biochim Biophys Acta 2013; 1834:2564-72. [PMID: 24075929 DOI: 10.1016/j.bbapap.2013.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 09/03/2013] [Accepted: 09/18/2013] [Indexed: 01/17/2023]
Abstract
The TTSS is used by Salmonella and many bacterial pathogens to inject virulence factors directly into the cytoplasm of target eukaryotic cells. Once translocated these so-called effector proteins hijack a vast array of crucial cellular functions to the benefit of the bacteria. In the bacterial cytoplasm, some effectors are stabilized and maintained in a secretion competent state by interaction with specific type III chaperones. In this work we studied the conformation of the Chaperone Binding Domain of the effector named Salmonella Outer protein B (SopB) alone and in complex with its cognate chaperone SigE by a combination of biochemical, biophysical and structural approaches. Our results show that the N-terminus part of SopB is mainly composed by α-helices and unfolded regions whose organization/stabilization depends on their interaction with the different partners. This suggests that the partially unfolded state of this N-terminal region, which confers the adaptability of the effector to bind very different partners during the infection cycle, allows the bacteria to modulate numerous host cells functions limiting the number of translocated effectors.
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Affiliation(s)
- Pierre Roblin
- INRA Biopolymères, Interactions et Assemblages, Rue de la Geraudière, 44316 Nantes, France; Synchrotron SOLEIL, L'orme des Merisiers, Saint Aubin, BP 48, 91192 Gif sur Yvette Cedex, France.
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Perrett CA, Zhou D. Salmonella type III effector SopB modulates host cell exocytosis. Emerg Microbes Infect 2013; 2:e32. [PMID: 26038467 PMCID: PMC3675406 DOI: 10.1038/emi.2013.31] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 03/16/2013] [Accepted: 03/14/2013] [Indexed: 11/09/2022]
Abstract
Salmonella enterica pathogenesis is dependent on its ability to enter and replicate inside host cells. Replication occurs inside the Salmonella-containing vacuole (SCV), a vacuolar compartment that is modified by bacterial effectors secreted through the two type III secretion systems (T3SS-1 and T3SS-2). Type III effectors interact with the host cell endocytic pathway to aid replication. We investigated whether Salmonella effector proteins may also interact with the host's exocytic pathway. A secreted alkaline phosphatase (SEAP) assay indicated three Salmonella effectors inhibited the secretory pathway, although only Salmonella outer protein B (SopB) was confirmed to block exocytosis using a vesicular stomatitis virus glycoprotein-green fluorescent protein (VSVG-GFP) transport assay. The 4-phosphatase activity of SopB was crucial to its effect on exocytosis. The interaction with the secretory pathway could potentially be important for providing replicating Salmonella with nutrients, contributing membrane material necessary for SCV biogenesis, altering antibacterial peptide/protein secretion or manipulating cell surface proteins important in the host response to infection.
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Affiliation(s)
- Charlotte A Perrett
- Department of Biological Sciences, Purdue University , West Lafayette, IN 47907, USA
| | - Daoguo Zhou
- Department of Biological Sciences, Purdue University , West Lafayette, IN 47907, USA
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