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Yang S, Zeng J, Yu J, Sun R, Tuo Y, Bai H. Insights into Chlamydia Development and Host Cells Response. Microorganisms 2024; 12:1302. [PMID: 39065071 PMCID: PMC11279054 DOI: 10.3390/microorganisms12071302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 06/15/2024] [Accepted: 06/23/2024] [Indexed: 07/28/2024] Open
Abstract
Chlamydia infections commonly afflict both humans and animals, resulting in significant morbidity and imposing a substantial socioeconomic burden worldwide. As an obligate intracellular pathogen, Chlamydia interacts with other cell organelles to obtain necessary nutrients and establishes an intracellular niche for the development of a biphasic intracellular cycle. Eventually, the host cells undergo lysis or extrusion, releasing infectious elementary bodies and facilitating the spread of infection. This review provides insights into Chlamydia development and host cell responses, summarizing the latest research on the biphasic developmental cycle, nutrient acquisition, intracellular metabolism, host cell fates following Chlamydia invasion, prevalent diseases associated with Chlamydia infection, treatment options, and vaccine prevention strategies. A comprehensive understanding of these mechanisms will contribute to a deeper comprehension of the intricate equilibrium between Chlamydia within host cells and the progression of human disease.
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Affiliation(s)
| | | | | | | | | | - Hong Bai
- Tianjin Key Laboratory of Cellular and Molecular Immunology (The Educational Ministry of China), Tianjin Institute of Immunology, Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China; (S.Y.); (J.Z.); (J.Y.); (R.S.); (Y.T.)
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Hall BA, Senior KE, Ocampo NT, Samanta D. Coxiella burnetii-containing vacuoles interact with host recycling endosomal proteins Rab11a and Rab35 for vacuolar expansion and bacterial growth. Front Cell Infect Microbiol 2024; 14:1394019. [PMID: 38841112 PMCID: PMC11150555 DOI: 10.3389/fcimb.2024.1394019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 05/01/2024] [Indexed: 06/07/2024] Open
Abstract
Introduction Coxiella burnetii is a gram-negative obligate intracellular bacterium and a zoonotic pathogen that causes human Q fever. The lack of effective antibiotics and a licensed vaccine for Coxiella in the U.S. warrants further research into Coxiella pathogenesis. Within the host cells, Coxiella replicates in an acidic phagolysosome-like vacuole termed Coxiella-containing vacuole (CCV). Previously, we have shown that the CCV pH is critical for Coxiella survival and that the Coxiella Type 4B secretion system regulates CCV pH by inhibiting the host endosomal maturation pathway. However, the trafficking pattern of the 'immature' endosomes in Coxiella- infected cells remained unclear. Methods We transfected HeLa cells with GFP-tagged Rab proteins and subsequently infected them with mCherry-Coxiella to visualize Rab protein localization. Infected cells were immunostained with anti-Rab antibodies to confirm the Rab localization to the CCV, to quantitate Rab11a and Rab35- positive CCVs, and to quantitate total recycling endosome content of infected cells. A dual-hit siRNA mediated knockdown combined with either immunofluorescent assay or an agarose-based colony-forming unit assay were used to measure the effects of Rab11a and Rab35 knockdown on CCV area and Coxiella intracellular growth. Results The CCV localization screen with host Rab proteins revealed that recycling endosome-associated proteins Rab11a and Rab35 localize to the CCV during infection, suggesting that CCV interacts with host recycling endosomes during maturation. Interestingly, only a subset of CCVs were Rab11a or Rab35-positive at any given time point. Quantitation of Rab11a/Rab35-positive CCVs revealed that while Rab11a interacts with the CCV more at 3 dpi, Rab35 is significantly more prevalent at CCVs at 6 dpi, suggesting that the CCV preferentially interacts with Rab11a and Rab35 depending on the stage of infection. Furthermore, we observed a significant increase in Rab11a and Rab35 fluorescent intensity in Coxiella-infected cells compared to mock, suggesting that Coxiella increases the recycling endosome content in infected cells. Finally, siRNA-mediated knockdown of Rab11a and Rab35 resulted in significantly smaller CCVs and reduced Coxiella intracellular growth, suggesting that recycling endosomal Rab proteins are essential for CCV expansion and bacterial multiplication. Discussion Our data, for the first time, show that the CCV dynamically interacts with host recycling endosomes for Coxiella intracellular survival and potentially uncovers novel host cell factors essential for Coxiella pathogenesis.
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Affiliation(s)
- Brooke A. Hall
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, United States
| | - Kristen E. Senior
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, United States
| | - Nicolle T. Ocampo
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, United States
| | - Dhritiman Samanta
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, United States
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Challagundla N, Phadnis D, Gupta A, Agrawal-Rajput R. Host Lipid Manipulation by Intracellular Bacteria: Moonlighting for Immune Evasion. J Membr Biol 2023; 256:393-411. [PMID: 37938349 DOI: 10.1007/s00232-023-00296-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 10/11/2023] [Indexed: 11/09/2023]
Abstract
Lipids are complex organic molecules that fulfill energy demands and sometimes act as signaling molecules. They are mostly found in membranes, thus playing an important role in membrane trafficking and protecting the cell from external dangers. Based on the composition of the lipids, their fluidity and charge, their interaction with embedded proteins vary greatly. Bacteria can hijack host lipids to satisfy their energy needs or to conceal themselves from host cells. Intracellular bacteria continuously exploit host, from their entry into host cells utilizing host lipid machinery to exiting through the cells. This acquisition of lipids from host cells helps in their disguise mechanism. The current review explores various mechanisms employed by the intracellular bacteria to manipulate and acquire host lipids. It discusses their role in manipulating host membranes and the subsequence impact on the host cells. Modulating these lipids in macrophages not only serve the purpose of the pathogen but also modulates the macrophage energy metabolism and functional state. Additionally, we have explored the intricate pathogenic relationship and the potential prospects of using this knowledge in lipid-based therapeutics to disrupt pathogen dominance.
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Affiliation(s)
- Naveen Challagundla
- Immunology Lab, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar, Gujarat, 382426, India
| | - Deepti Phadnis
- Immunology Lab, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar, Gujarat, 382426, India
| | - Aakriti Gupta
- Immunology Lab, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar, Gujarat, 382426, India
| | - Reena Agrawal-Rajput
- Immunology Lab, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar, Gujarat, 382426, India.
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Park YP, Roach T, Soh S, Zeumer-Spataro L, Choi SC, Ostrov DA, Yang Y, Morel L. Molecular Mechanisms of Lupus Susceptibility Allele PBX1D. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2023; 211:727-734. [PMID: 37486226 PMCID: PMC10530199 DOI: 10.4049/jimmunol.2300362] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 07/03/2023] [Indexed: 07/25/2023]
Abstract
Pre-B cell leukemia homeobox 1 (PBX1) controls chromatin accessibility to a large number of genes in various cell types. Its dominant negative splice isoform, PBX1D, which lacks the DNA and Hox-binding domains, is expressed more frequently in the CD4+ T cells from lupus-prone mice and patients with systemic lupus erythematosus than healthy control subjects. PBX1D overexpression in CD4+ T cells impaired regulatory T cell homeostasis and expanded inflammatory CD4+ T cells. In this study, we showed that PBX1 message expression is downregulated by activation in CD4+ T cells as well as in B cells. PBX1D protein was less stable than the normal isoform, PBX1B, and it is degraded through the ubiquitin-proteasome-dependent pathway. The DNA binding domain lacking in PBX1D has two putative ubiquitin binding sites, K292 and K293, that are predicted to be in direct contact with DNA. Mutation of K292-293 reduced PBX1B stability to a level similar to PBX1D and abrogated DNA binding. In addition, contrary to PBX1B, PBX1D is retained in the cytoplasm without the help of the cofactors MEIS or PREP1, indicating a different requirement for nuclear translocation. Overall, these findings suggest that multiple post-transcriptional mechanisms are responsible for PBX1D loss of function and induction of CD4+ T cell inflammatory phenotypes in systemic lupus erythematosus.
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Affiliation(s)
- Yuk Pheel Park
- Department of Microbiology, Immunology, and Molecular Genetics, University of Texas Health San Antonio, TX 78229-3900, USA
| | - Tracoyia Roach
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida, College of Medicine, Gainesville, FL32610, USA
| | - Sujung Soh
- Research Institute of Women’s Health, Sookmyung Women’s University, 100 Cheongparo 47-gil, Yongsan-Gu, Seoul 04310, South Korea, USA
| | - Leilani Zeumer-Spataro
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida, College of Medicine, Gainesville, FL32610, USA
| | - Seung-Chul Choi
- Department of Microbiology, Immunology, and Molecular Genetics, University of Texas Health San Antonio, TX 78229-3900, USA
| | - David A. Ostrov
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida, College of Medicine, Gainesville, FL32610, USA
| | - Young Yang
- Research Institute of Women’s Health, Sookmyung Women’s University, 100 Cheongparo 47-gil, Yongsan-Gu, Seoul 04310, South Korea, USA
| | - Laurence Morel
- Department of Microbiology, Immunology, and Molecular Genetics, University of Texas Health San Antonio, TX 78229-3900, USA
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Clemente TM, Angara RK, Gilk SD. Establishing the intracellular niche of obligate intracellular vacuolar pathogens. Front Cell Infect Microbiol 2023; 13:1206037. [PMID: 37645379 PMCID: PMC10461009 DOI: 10.3389/fcimb.2023.1206037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/21/2023] [Indexed: 08/31/2023] Open
Abstract
Obligate intracellular pathogens occupy one of two niches - free in the host cell cytoplasm or confined in a membrane-bound vacuole. Pathogens occupying membrane-bound vacuoles are sequestered from the innate immune system and have an extra layer of protection from antimicrobial drugs. However, this lifestyle presents several challenges. First, the bacteria must obtain membrane or membrane components to support vacuole expansion and provide space for the increasing bacteria numbers during the log phase of replication. Second, the vacuole microenvironment must be suitable for the unique metabolic needs of the pathogen. Third, as most obligate intracellular bacterial pathogens have undergone genomic reduction and are not capable of full metabolic independence, the bacteria must have mechanisms to obtain essential nutrients and resources from the host cell. Finally, because they are separated from the host cell by the vacuole membrane, the bacteria must possess mechanisms to manipulate the host cell, typically through a specialized secretion system which crosses the vacuole membrane. While there are common themes, each bacterial pathogen utilizes unique approach to establishing and maintaining their intracellular niches. In this review, we focus on the vacuole-bound intracellular niches of Anaplasma phagocytophilum, Ehrlichia chaffeensis, Chlamydia trachomatis, and Coxiella burnetii.
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Affiliation(s)
| | | | - Stacey D. Gilk
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, United States
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Larson CL, Pullman W, Beare PA, Heinzen RA. Identification of Type 4B Secretion System Substrates That Are Conserved among Coxiella burnetii Genomes and Promote Intracellular Growth. Microbiol Spectr 2023; 11:e0069623. [PMID: 37199620 PMCID: PMC10269450 DOI: 10.1128/spectrum.00696-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 04/21/2023] [Indexed: 05/19/2023] Open
Abstract
Coxiella burnetii is a Gram-negative pathogen that infects a variety of mammalian hosts. Infection of domesticated ewes can cause fetal abortion, whereas acute human infection normally manifests as the flu-like illness Q fever. Successful host infection requires replication of the pathogen within the lysosomal Coxiella-containing vacuole (CCV). The bacterium encodes a type 4B secretion system (T4BSS) that delivers effector proteins into the host cell. Disruption of C. burnetii T4BSS effector export abrogates CCV biogenesis and bacterial replication. Over 150 C. burnetii T4BSS substrates have been designated often based on heterologous protein translocation by the Legionella pneumophila T4BSS. Cross-genome comparisons predict that many of these T4BSS substrates are truncated or absent in the acute-disease reference strain C. burnetii Nine Mile. This study investigated the function of 32 proteins conserved among diverse C. burnetii genomes that are reported to be T4BSS substrates. Despite being previously designated T4BSS substrates, many of the proteins were not translocated by C. burnetii when expressed fused to the CyaA or BlaM reporter tags. CRISPR interference (CRISPRi) indicated that of the validated C. burnetii T4BSS substrates, CBU0122, CBU1752, CBU1825, and CBU2007 promote C. burnetii replication in THP-1 cells and CCV biogenesis in Vero cells. When expressed in HeLa cells tagged at its C or N terminus with mCherry, CBU0122 localized to the CCV membrane and the mitochondria, respectively. Collectively, these data further define the repertoire of bona fide C. burnetii T4BSS substrates. IMPORTANCE Coxiella burnetii secretes effector proteins via a T4BSS that are required for successful infection. Over 150 C. burnetii proteins are reported to be T4BSS substrates and often by default considered putative effectors, but few have assigned functions. Many C. burnetii proteins were designated T4BSS substrates using heterologous secretion assays in L. pneumophila and/or have coding sequences that are absent or pseudogenized in clinically relevant C. burnetii strains. This study examined 32 previously reported T4BSS substrates that are conserved among C. burnetii genomes. Of the proteins tested that were previously designated T4BSS substrates using L. pneumophila, most were not exported by C. burnetii. Several T4BSS substrates that were validated in C. burnetii also promoted pathogen intracellular replication and one trafficked to late endosomes and the mitochondria in a manner suggestive of effector activity. This study identified several bona fide C. burnetii T4BSS substrates and further refined the methodological criteria for their designation.
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Affiliation(s)
- Charles L. Larson
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
- Innate Immunity and Pathogenesis Section, Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Willis Pullman
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Paul A. Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
- Genomics Research Section, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Robert A. Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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Yadav A, Brewer MN, Elshahed MS, Shaw EI. Comparative Transcriptomics and Genomics from Continuous Axenic Media Growth Identifies Coxiella burnetii Intracellular Survival Strategies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.06.527305. [PMID: 36798183 PMCID: PMC9934583 DOI: 10.1101/2023.02.06.527305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Coxiella burnetii (Cb) is an obligate intracellular pathogen in nature and the causative agent of acute Q fever as well as chronic diseases. In an effort to identify genes and proteins crucial to their normal intracellular growth lifestyle, we applied a "Reverse evolution" approach where the avirulent Nine Mile Phase II strain of Cb was grown for 67 passages in chemically defined ACCM-D media and gene expression patterns and genome integrity from various passages was compared to passage number one following intracellular growth. Transcriptomic analysis identified a marked downregulation of the structural components of the type 4B secretion system (T4BSS), the general secretory (sec) pathway, as well as 14 out of 118 previously identified genes encoding effector proteins. Additional downregulated pathogenicity determinants genes included several chaperones, LPS, and peptidoglycan biosynthesis. A general marked downregulation of central metabolic pathways was also observed, which was balanced by a marked upregulation of genes encoding transporters. This pattern reflected the richness of the media and diminishing anabolic and ATP-generation needs. Finally, genomic sequencing and comparative genomic analysis demonstrated an extremely low level of mutation across passages, despite the observed Cb gene expression changes following acclimation to axenic media.
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Affiliation(s)
- Archana Yadav
- Department of Microbiology and Molecular Genetics. Oklahoma State University. Stillwater, OK.USA
| | - Melissa N. Brewer
- Department of Microbiology and Molecular Genetics. Oklahoma State University. Stillwater, OK.USA
- Biological Sciences. Southeastern Oklahoma State University. Durant, OK. USA
| | - Mostafa S. Elshahed
- Department of Microbiology and Molecular Genetics. Oklahoma State University. Stillwater, OK.USA
| | - Edward I. Shaw
- Department of Microbiology and Molecular Genetics. Oklahoma State University. Stillwater, OK.USA
- Department of Biomedical Sciences. Philadelphia College of Osteopathic Medicine. Moultrie, GA. USA
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Yadav A, Brewer MN, Elshahed MS, Shaw EI. Comparative transcriptomics and genomics from continuous axenic media growth identifies Coxiella burnetii intracellular survival strategies. Pathog Dis 2023; 81:ftad009. [PMID: 37193663 PMCID: PMC10237335 DOI: 10.1093/femspd/ftad009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 04/17/2023] [Accepted: 05/15/2023] [Indexed: 05/18/2023] Open
Abstract
Coxiella burnetii (Cb) is an obligate intracellular pathogen in nature and the causative agent of acute Q fever as well as chronic diseases. In an effort to identify genes and proteins crucial to their normal intracellular growth lifestyle, we applied a 'reverse evolution' approach where the avirulent Nine Mile Phase II strain of Cb was grown for 67 passages in chemically defined ACCM-D media and gene expression patterns and genome integrity from various passages was compared to passage number one following intracellular growth. Transcriptomic analysis identified a marked downregulation of the structural components of the type 4B secretion system (T4BSS), the general secretory (Sec) pathway, as well as 14 out of 118 previously identified genes encoding effector proteins. Additional downregulated pathogenicity determinants genes included several chaperones, LPS, and peptidoglycan biosynthesis. A general marked downregulation of central metabolic pathways was also observed, which was balanced by a marked upregulation of genes encoding transporters. This pattern reflected the richness of the media and diminishing anabolic, and ATP-generation needs. Finally, genomic sequencing and comparative genomic analysis demonstrated an extremely low level of mutation across passages, despite the observed Cb gene expression changes following acclimation to axenic media.
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Affiliation(s)
- Archana Yadav
- Department of Microbiology and Molecular Genetics, Oklahoma State University,, 74078 Stillwater, OK, United States
| | - Melissa N Brewer
- Department of Microbiology and Molecular Genetics, Oklahoma State University,, 74078 Stillwater, OK, United States
- Biological Sciences, Southeastern Oklahoma State University, 74078 Durant, OK, United States
| | - Mostafa S Elshahed
- Department of Microbiology and Molecular Genetics, Oklahoma State University,, 74078 Stillwater, OK, United States
| | - Edward I Shaw
- Department of Microbiology and Molecular Genetics, Oklahoma State University,, 74078 Stillwater, OK, United States
- Department of Biomedical Sciences, Philadelphia College of Osteopathic Medicine, 74078 Moultrie, GA, United States
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Sahu R, Rawool DB, Vinod VK, Malik SVS, Barbuddhe SB. Current approaches for the detection of Coxiella burnetii infection in humans and animals. J Microbiol Methods 2020; 179:106087. [PMID: 33086105 DOI: 10.1016/j.mimet.2020.106087] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/14/2020] [Accepted: 10/14/2020] [Indexed: 02/09/2023]
Abstract
Q fever (coxiellosis), caused by Coxiella burnetii, is an emerging or re-emerging zoonotic disease of public health significance and with worldwide distribution. As a causal agent of the one among the 13 global priority zoonoses, having the infectious dose as low as one bacterium, C. burnetii has been regarded as an obligate intracellular bacterial pathogen. The agent has been classified as a Group B bioterrorism agent by the Centre for Disease Control and Prevention (CDC), and the disease is included in the World Organisation for Animal Health (OIE) list of notifiable diseases. It is mainly transmitted through airborne route in humans and animals. Isolation of C. burnetii, using standard routine laboratory culture techniques was impossible until formulation of axenic-based medium. However, it is still to be included among routinely isolated laboratory pathogen, accounting prolonged incubation period (~7 days) and requirement of specific oxygen concentration (2.5% O2). Therefore, indirect diagnostic tools have been mainly used for its diagnosis. So far serology has been mostly used for testing for C. burnetii infection. The detection of C. burnetii DNA by PCR in various clinical samples have also been widely used. The disease has remained largely under-reported, underdiagnosed and as a masked zoonosis; and therefore, needs to be explored through well-planned scientific studies for knowing its true status and likely it impact in humans and animals by employing state-of-the-art diagnostics, identifying its diverse and new host range, as well as risk factors involved in different geo-climatic, behavioural and social settings as well as risk groups. Here, we reviewed the current approaches used for the detection of C. burnetii infection in humans and animals at the population and individual level.
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Affiliation(s)
- Radhakrishna Sahu
- Division of Veterinary Public Health, ICAR- Indian Veterinary Research Institute, Izatnagar 243 122, India
| | - Deepak B Rawool
- ICAR- National Research Centre on Meat, Hyderabad 500 092, India
| | - Valil Kunjukunju Vinod
- Division of Veterinary Public Health, ICAR- Indian Veterinary Research Institute, Izatnagar 243 122, India
| | - S V S Malik
- Division of Veterinary Public Health, ICAR- Indian Veterinary Research Institute, Izatnagar 243 122, India
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Karam J, Méresse S, Kremer L, Daher W. The roles of tetraspanins in bacterial infections. Cell Microbiol 2020; 22:e13260. [PMID: 32902857 DOI: 10.1111/cmi.13260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/22/2020] [Accepted: 07/24/2020] [Indexed: 12/18/2022]
Abstract
Tetraspanins, a wide family composed of 33 transmembrane proteins, are associated with different types of proteins through which they arbitrate important cellular processes such as fusion, adhesion, invasion, tissue differentiation and immunological responses. Tetraspanins share a comparable structural design, which consists of four hydrophobic transmembrane domains with cytoplasmic and extracellular loops. They cooperate with different proteins, including other tetraspanins, receptors or signalling proteins to compose functional complexes at the cell surface, designated tetraspanin-enriched microdomains (TEM). Increasing evidences establish that tetraspanins are exploited by numerous intracellular pathogens as a doorway for entering and replicating within human cells. Although previous surveys focused mainly on viruses and parasites, it is now becoming clear that bacteria interact with tetraspanins, using TEM as a "gateway" to infection. In this review, we examine the biological functions of tetraspanins that are relevant to bacterial infective procedures and consider the available data that reveal how different bacteria benefit from host cell tetraspanins in infection and in the pathogenesis of diseases. We will also emphasise the stimulating potentials of targeting tetraspanins for preventing bacterial infectious diseases, using specific neutralising antibodies or anti-adhesion peptide-based therapies. Such innovative therapeutic opportunities may deliver alternatives for fighting difficult-to-manage and drug-resistant bacterial pathogens.
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Affiliation(s)
- Jona Karam
- Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, Montpellier, France
| | | | - Laurent Kremer
- Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, Montpellier, France.,INSERM, IRIM, Montpellier, France
| | - Wassim Daher
- Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, Montpellier, France.,INSERM, IRIM, Montpellier, France
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Samanta D, Clemente TM, Schuler BE, Gilk SD. Coxiella burnetii Type 4B Secretion System-dependent manipulation of endolysosomal maturation is required for bacterial growth. PLoS Pathog 2019; 15:e1007855. [PMID: 31869379 PMCID: PMC6953889 DOI: 10.1371/journal.ppat.1007855] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 01/10/2020] [Accepted: 12/05/2019] [Indexed: 01/24/2023] Open
Abstract
Upon host cell infection, the obligate intracellular bacterium Coxiella burnetii resides and multiplies within the Coxiella–Containing Vacuole (CCV). The nascent CCV progresses through the endosomal maturation pathway into a phagolysosome, acquiring endosomal and lysosomal markers, as well as acidic pH and active proteases and hydrolases. Approximately 24–48 hours post infection, heterotypic fusion between the CCV and host endosomes/lysosomes leads to CCV expansion and bacterial replication in the mature CCV. Initial CCV acidification is required to activate C. burnetii metabolism and the Type 4B Secretion System (T4BSS), which secretes effector proteins required for CCV maturation. However, we found that the mature CCV is less acidic (pH~5.2) than lysosomes (pH~4.8). Further, inducing CCV acidification to pH~4.8 causes C. burnetii lysis, suggesting C. burnetii actively regulates pH of the mature CCV. Because heterotypic fusion with host endosomes/lysosomes may influence CCV pH, we investigated endosomal maturation in cells infected with wildtype (WT) or T4BSS mutant (ΔdotA) C. burnetii. In WT-infected cells, we observed a significant decrease in proteolytically active, LAMP1-positive endolysosomal vesicles, compared to mock or ΔdotA-infected cells. Using a ratiometric assay to measure endosomal pH, we determined that the average pH of terminal endosomes in WT-infected cells was pH~5.8, compared to pH~4.75 in mock and ΔdotA-infected cells. While endosomes progressively acidified from the periphery (pH~5.5) to the perinuclear area (pH~4.7) in both mock and ΔdotA-infected cells, endosomes did not acidify beyond pH~5.2 in WT-infected cells. Finally, increasing lysosomal biogenesis by overexpressing the transcription factor EB resulted in smaller, more proteolytically active CCVs and a significant decrease in C. burnetii growth, indicating host lysosomes are detrimental to C. burnetii. Overall, our data suggest that C. burnetii inhibits endosomal maturation to reduce the number of proteolytically active lysosomes available for heterotypic fusion with the CCV, possibly as a mechanism to regulate CCV pH. The obligate intracellular bacterium Coxiella burnetii causes human Q fever, which manifests as a flu-like illness but can develop into a life-threatening and difficult to treat endocarditis. C. burnetii, in contrast to many other intracellular bacteria, thrives within a lysosome-like vacuole in host cells. However, we previously found that the C. burnetii vacuole is not as acidic as lysosomes and increased acidification kills the bacteria, suggesting that C. burnetii regulates the pH of its vacuole. Here, we discovered that C. burnetii blocks endolysosomal maturation and acidification during host cell infection, resulting in fewer lysosomes in the host cell. Moreover, increasing lysosomes in the host cells inhibited C. burnetii growth. Together, our study suggests that C. burnetii regulates vacuole acidity and blocks endosomal maturation in order to produce a permissive intracellular niche.
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Affiliation(s)
- Dhritiman Samanta
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Tatiana M. Clemente
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Baleigh E. Schuler
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Stacey D. Gilk
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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Dependency of Coxiella burnetii Type 4B Secretion on the Chaperone IcmS. J Bacteriol 2019; 201:JB.00431-19. [PMID: 31501284 DOI: 10.1128/jb.00431-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/03/2019] [Indexed: 12/22/2022] Open
Abstract
Macrophage parasitism by Coxiella burnetii, the cause of human Q fever, requires the translocation of proteins with effector functions directly into the host cell cytosol via a Dot/Icm type 4B secretion system (T4BSS). Secretion by the analogous Legionella pneumophila T4BSS involves signal sequences within the C-terminal and internal domains of effector proteins. The cytoplasmic chaperone pair IcmSW promotes secretion and binds internal sites distinct from signal sequences. In the present study, we investigated requirements of C. burnetii IcmS for host cell parasitism and effector translocation. A C. burnetii icmS deletion mutant (ΔicmS) exhibited impaired replication in Vero epithelial cells, deficient formation of the Coxiella-containing vacuole, and aberrant T4BSS secretion. Three secretion phenotypes were identified from a screen of 50 Dot/Icm substrates: IcmS dependent (secreted by only wild-type bacteria), IcmS independent (secreted by both wild-type and ΔicmS bacteria), or IcmS inhibited (secreted by only ΔicmS bacteria). Secretion was assessed for N-terminal or C-terminal truncated forms of CBU0794 and CBU1525. IcmS-inhibited secretion of CBU1525 required a C-terminal secretion signal whereas IcmS-dependent secretion of CBU0794 was directed by C-terminal and internal signals. Interchange of the C-terminal 50 amino acids of CBU0794 and CBU1525 revealed that sites within the C terminus regulate IcmS dependency. Glutathione S-transferase-tagged IcmSW bound internal sequences of IcmS-dependent and -inhibited substrates. Thus, the growth defect of the C. burnetii ΔicmS strain is associated with a loss of T4BSS chaperone activity that both positively and negatively regulates effector translocation.IMPORTANCE The intracellular pathogen Coxiella burnetii employs a type 4B secretion system (T4BSS) that promotes growth by translocating effectors of eukaryotic pathways into host cells. T4BSS regulation modeled in Legionella pneumophila indicates IcmS facilitates effector translocation. Here, we characterized type 4B secretion by a Coxiella ΔicmS mutant that exhibits intracellular growth defects. T4BSS substrates demonstrated increased, equivalent, or decreased secretion by the ΔicmS mutant relative to wild-type Coxiella Similar to the Legionella T4BSS, IcmS dependency in Coxiella was determined by C-terminal and/or internal secretion signals. However, IcmS inhibited secretion of some effectors by Coxiella that were previously shown to be translocated by Legionella Thus, Coxiella has a unique IcmS regulatory mechanism that both positively and negatively regulates T4BSS export.
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Mezouar S, Omar Osman I, Melenotte C, Slimani C, Chartier C, Raoult D, Mege JL, Devaux CA. High Concentrations of Serum Soluble E-Cadherin in Patients With Q Fever. Front Cell Infect Microbiol 2019; 9:219. [PMID: 31293984 PMCID: PMC6598114 DOI: 10.3389/fcimb.2019.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 06/07/2019] [Indexed: 12/19/2022] Open
Abstract
Cadherins switching is a hallmark of neoplasic processes. The E-cadherin (E-cad) subtype is one of the surface molecules regulating cell-to-cell adhesion. After its cleavage by sheddases, a soluble fragment (sE-cad) is released that has been identified as a pro-carcinogenic inflammatory signal in several bacteria-induced cancers. Recently we reported that Q fever, a disease due to Coxiella burnetii infection, can be complicated by occurrence of non-Hodgkin lymphoma (NHL). Therefore, we studied E-cad switching in Q fever. The sE-cad levels were found increased in the sera of acute and persistent Q fever patients, whereas they remained at the baseline in controls groups of healthy donors, people cured of Q fever, patients suffering from unrelated inflammatory diseases, and past Q fever patients who developed NHL. These results indicate that sE-cad can be considered as a new biomarker of C. burnetii infection rather than a marker of NHL-associated to Q fever. We wondered if changes in sE-cad reflected variations in the CDH1 gene transcription. The expression of E-cad mRNA and its intracellular ligand β-catenin was down-regulated in peripheral blood mononuclear cells (PBMCs) of patients with either acute or persistent forms of Q fever. Indeed, a lower cell-surface expression of E-cad was measured in a minority (<5%) subpopulation of HLADR+/CD16+ monocytes from patients with acute Q fever. However, a very strong increase in E-cad expression was observed on more than 30% of the HLADR+/CD16+ monocytes of persistent Q fever patients, a cell subpopulation known to be a target for C. burnetii in humans. An experimental in vitro infection of healthy donors' PBMCs with C. burnetii, was performed to directly evaluate the link between C. burnetii interaction with PBMCs and their E-cad expression. A significant increase in the percentage of HLADR+/CD16+ monocytes expressing E-cad was measured after PBMCs had been incubated for 8 h with C. burnetii Nine Mile strain. Altogether, these data demonstrate that C. burnetii severely impairs the E-cad expression in circulating cells of Q fever patients.
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Affiliation(s)
- Soraya Mezouar
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
| | - Ikram Omar Osman
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
| | - Cléa Melenotte
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
| | - Camélia Slimani
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
| | - Céline Chartier
- APHM, IHU-Méditerranée Infection, UF Immunologie, Marseille, France
| | - Didier Raoult
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
| | - Jean-Louis Mege
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France.,APHM, IHU-Méditerranée Infection, UF Immunologie, Marseille, France
| | - Christian A Devaux
- Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France.,CNRS, Marseille, France
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14
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Abstract
The entry of pathogens into nonphagocytic host cells has received much attention in the past three decades, revealing a vast array of strategies employed by bacteria and viruses. A method of internalization that has been extensively studied in the context of viral infections is the use of the clathrin-mediated pathway. More recently, a role for clathrin in the entry of some intracellular bacterial pathogens was discovered. Classically, clathrin-mediated endocytosis was thought to accommodate internalization only of particles smaller than 150 nm; however, this was challenged upon the discovery that Listeria monocytogenes requires clathrin to enter eukaryotic cells. Now, with discoveries that clathrin is required during other stages of some bacterial infections, another paradigm shift is occurring. There is a more diverse impact of clathrin during infection than previously thought. Much of the recent data describing clathrin utilization in processes such as bacterial attachment, cell-to-cell spread and intracellular growth may be due to newly discovered divergent roles of clathrin in the cell. Not only does clathrin act to facilitate endocytosis from the plasma membrane, but it also participates in budding from endosomes and the Golgi apparatus and in mitosis. Here, the manipulation of clathrin processes by bacterial pathogens, including its traditional role during invasion and alternative ways in which clathrin supports bacterial infection, is discussed. Researching clathrin in the context of bacterial infections will reveal new insights that inform our understanding of host-pathogen interactions and allow researchers to fully appreciate the diverse roles of clathrin in the eukaryotic cell.
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Affiliation(s)
- Eleanor A Latomanski
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Hayley J Newton
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
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15
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Make It a Sweet Home: Responses of Chlamydia trachomatis to the Challenges of an Intravacuolar Lifestyle. Microbiol Spectr 2019; 7. [PMID: 30848236 DOI: 10.1128/microbiolspec.bai-0005-2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Intravacuolar development has been adopted by several bacteria that grow inside a host cell. Remaining in a vacuole, as opposed to breaching the cytosol, protects the bacteria from some aspects of the cytosolic innate host defense and allows them to build an environment perfectly adapted to their needs. However, this raises new challenges: the host resources are separated from the bacteria by a lipid bilayer that is nonpermeable to most nutrients. In addition, the area of this lipid bilayer needs to expand to accommodate bacterial multiplication. This requires building material and energy that are not directly invested in bacterial growth. This article describes the strategies acquired by the obligate intracellular pathogen Chlamydia trachomatis to circumvent the difficulties raised by an intravacuolar lifestyle. We start with an overview of the origin and composition of the vacuolar membrane. Acquisition of host resources is largely, although not exclusively, mediated by interactions with membranous compartments of the eukaryotic cell, and we describe how the inclusion modifies the architecture of the cell and distribution of the neighboring compartments. The second part of this review describes the four mechanisms characterized so far by which the bacteria acquire resources from the host: (i) transport/diffusion across the vacuole membrane, (ii) fusion of this membrane with host compartments, (iii) direct transfer of lipids at membrane contact sites, and (iv) engulfment by the vacuole membrane of large cytoplasmic entities.
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16
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Noncanonical Inhibition of mTORC1 by Coxiella burnetii Promotes Replication within a Phagolysosome-Like Vacuole. mBio 2019; 10:mBio.02816-18. [PMID: 30723133 PMCID: PMC6428759 DOI: 10.1128/mbio.02816-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Coxiella burnetii is an intracellular pathogenic bacterium that replicates within a lysosomal vacuole. Biogenesis of the Coxiella-containing vacuole (CCV) requires effector proteins delivered into the host cell cytosol by the type 4B secretion system (T4BSS). Modifications to lysosomal physiology required for pathogen replication within the CCV are poorly understood. Mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) is a master kinase that regulates lysosome structure and function. Nutrient deprivation inhibits mTORC1, which promotes cell catabolism in the form of accelerated autophagy and increased lysosome biosynthesis. Here, we report that C. burnetii growth is enhanced by T4BSS-dependent inhibition of mTORC1 that does not activate autophagy. Canonical inhibition of mTORC1 by starvation or inhibitor treatment that induces autophagic flux does not benefit C. burnetii growth. Furthermore, hyperactivation of mTORC1 impairs bacterial replication. These findings indicate that C. burnetii inhibition of mTORC1 without accelerated autophagy promotes bacterial growth. The Q fever agent Coxiella burnetii is a Gram-negative bacterium that invades macrophages and replicates inside a specialized lysosomal vacuole. The pathogen employs a type 4B secretion system (T4BSS) to deliver effector proteins into the host cell that modify the Coxiella-containing vacuole (CCV) into a replication-permissive niche. Mature CCVs are massive degradative organelles that acquire lysosomal proteins. Inhibition of mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) kinase by nutrient deprivation promotes autophagy and lysosome fusion, as well as activation of the transcription factors TFE3 and TFEB (TFE3/B), which upregulates expression of lysosomal genes. Here, we report that C. burnetii inhibits mTORC1 as evidenced by impaired localization of mTORC1 to endolysosomal membranes and decreased phosphorylation of elF4E-binding protein 1 (4E-BP1) and S6 kinase 1 in infected cells. Infected cells exhibit increased amounts of autophagy-related proteins protein 1A/1B-light chain 3 (LC3) and p62 as well as of activated TFE3. However, C. burnetii did not accelerate autophagy or block autophagic flux triggered by cell starvation. Activation of autophagy or transcription by TFE3/B increased CCV expansion without enhancing bacterial replication. By contrast, knockdown of tuberous sclerosis complex 1 (TSC1) or TSC2, which hyperactivates mTORC1, impaired CCV expansion and bacterial replication. Together, these data demonstrate that specific inhibition of mTORC1 by C. burnetii, but not amplified cell catabolism via autophagy, is required for optimal pathogen replication. These data reveal a complex interplay between lysosomal function and host cell metabolism that regulates C. burnetii intracellular growth.
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17
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Best A, Abu Kwaik Y. Nutrition and Bipartite Metabolism of Intracellular Pathogens. Trends Microbiol 2019; 27:550-561. [PMID: 30655036 DOI: 10.1016/j.tim.2018.12.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 11/20/2018] [Accepted: 12/20/2018] [Indexed: 12/29/2022]
Abstract
The host is a nutrient-rich niche for microbial pathogens, but one that comes with obstacles and challenges. Many intracellular pathogens like Legionella pneumophila, Coxiella burnetii, Listeria monocytogenes, and Chlamydia trachomatis have developed bipartite metabolism within their hosts. This style of metabolic regulation enables pathogen sensing of specific nutrients to engage them into catabolic and anabolic processes, and contributes to temporal and spatial pathogen phenotypic modulation. Not only have intracellular pathogens adapted their metabolism to the host, they have also acquired idiosyncratic strategies to exploit host nutritional supplies and intercept metabolites. Francisella tularensis and Anaplasma phagocytophilum alter host autophagy, Shigella flexneri intercepts all host pyruvate, while L. pneumophila induces host protein degradation and blocks protein translation. Strategies of pathogen manipulation of host nutrients could serve as therapeutic targets.
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Affiliation(s)
- Ashley Best
- Department of Microbiology and Immunology, College of Medicine, University of Louisville, KY, USA
| | - Yousef Abu Kwaik
- Department of Microbiology and Immunology, College of Medicine, University of Louisville, KY, USA; Center for Predictive Medicine, College of Medicine, University of Louisville, KY, USA.
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18
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Allgood SC, Neunuebel MR. The recycling endosome and bacterial pathogens. Cell Microbiol 2018; 20:e12857. [PMID: 29748997 PMCID: PMC5993623 DOI: 10.1111/cmi.12857] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 04/05/2018] [Accepted: 04/27/2018] [Indexed: 12/29/2022]
Abstract
Bacterial pathogens have developed a wide range of strategies to survive within human cells. A number of pathogens multiply in a vacuolar compartment, whereas others can rupture the vacuole and replicate in the host cytosol. A common theme among many bacterial pathogens is the use of specialised secretion systems to deliver effector proteins into the host cell. These effectors can manipulate the host's membrane trafficking pathways to remodel the vacuole into a replication-permissive niche and prevent degradation. As master regulators of eukaryotic membrane traffic, Rab GTPases are principal targets of bacterial effectors. This review highlights the manipulation of Rab GTPases that regulate host recycling endocytosis by several bacterial pathogens, including Chlamydia pneumoniae, Chlamydia trachomatis, Shigella flexneri, Salmonella enterica serovar Typhimurium, Uropathogenic Escherichia coli, and Legionella pneumophila. Recycling endocytosis plays key roles in a variety of cellular aspects such as nutrient uptake, immunity, cell division, migration, and adhesion. Though much remains to be understood about the molecular basis and the biological relevance of bacterial pathogens exploiting Rab GTPases, current knowledge supports the notion that endocytic recycling Rab GTPases are differentially targeted to avoid degradation and support bacterial replication. Thus, future studies of the interactions between bacterial pathogens and host endocytic recycling pathways are poised to deepen our understanding of bacterial survival strategies.
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Affiliation(s)
| | - M. Ramona Neunuebel
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
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19
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Miller HE, Larson CL, Heinzen RA. Actin polymerization in the endosomal pathway, but not on the Coxiella-containing vacuole, is essential for pathogen growth. PLoS Pathog 2018; 14:e1007005. [PMID: 29668757 PMCID: PMC5927470 DOI: 10.1371/journal.ppat.1007005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 04/30/2018] [Accepted: 04/02/2018] [Indexed: 12/15/2022] Open
Abstract
Coxiella burnetii is an intracellular bacterium that replicates within an expansive phagolysosome-like vacuole. Fusion between the Coxiella-containing vacuole (CCV) and late endosomes/multivesicular bodies requires Rab7, the HOPS tethering complex, and SNARE proteins, with actin also speculated to play a role. Here, we investigated the importance of actin in CCV fusion. Filamentous actin patches formed around the CCV membrane that were preferred sites of vesicular fusion. Accordingly, the mediators of endolysosomal fusion Rab7, VAMP7, and syntaxin 8 were concentrated in CCV actin patches. Generation of actin patches required C. burnetii type 4B secretion and host retromer function. Patches decorated with VPS29 and VPS35, components of the retromer, FAM21 and WASH, members of the WASH complex that engage the retromer, and Arp3, a component of the Arp2/3 complex that generates branched actin filaments. Depletion by siRNA of VPS35 or VPS29 reduced CCV actin patches and caused Rab7 to uniformly distribute in the CCV membrane. C. burnetii grew normally in VPS35 or VPS29 depleted cells, as well as WASH-knockout mouse embryo fibroblasts, where CCVs are devoid of actin patches. Endosome recycling to the plasma membrane and trans-Golgi of glucose transporter 1 (GLUT1) and cationic-independent mannose-6-phosphate receptor (CI-M6PR), respectively, was normal in infected cells. However, siRNA knockdown of retromer resulted in aberrant trafficking of GLUT1, but not CI-M6PR, suggesting canonical retrograde trafficking is unaffected by retromer disruption. Treatment with the specific Arp2/3 inhibitor CK-666 strongly inhibited CCV formation, an effect associated with altered endosomal trafficking of transferrin receptor. Collectively, our results show that CCV actin patches generated by retromer, WASH, and Arp2/3 are dispensable for CCV biogenesis and stability. However, Arp2/3-mediated production of actin filaments required for cargo transport within the endosomal system is required for CCV generation. These findings delineate which of the many actin related events that shape the endosomal compartment are important for CCV formation.
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Affiliation(s)
- Heather E. Miller
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Charles L. Larson
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Robert A. Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
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20
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Luedtke BE, Mahapatra S, Lutter EI, Shaw EI. The Coxiella Burnetii type IVB secretion system (T4BSS) component DotA is released/secreted during infection of host cells and during in vitro growth in a T4BSS-dependent manner. Pathog Dis 2018; 75:3753448. [PMID: 28449081 DOI: 10.1093/femspd/ftx047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 04/20/2017] [Indexed: 01/01/2023] Open
Abstract
Coxiella burnetii is a Gram-negative intracellular pathogen and is the causative agent of the zoonotic disease Q fever. To cause disease, C. burnetii requires a functional type IVB secretion system (T4BSS) to transfer effector proteins required for the establishment and maintenance of a membrane-bound parasitophorous vacuole (PV) and further modulation of host cell process. However, it is not clear how the T4BSS interacts with the PV membrane since neither a secretion pilus nor an extracellular pore forming apparatus has not been described. To address this, we used the acidified citrate cysteine medium (ACCM) along with cell culture infection and immunological techniques to identify the cellular and extracellular localization of T4BSS components. Interestingly, we found that DotA and IcmX were secreted/released in a T4BSS-dependent manner into the ACCM. Analysis of C. burnetii-infected cell lines revealed that DotA colocalized with the host cell marker CD63 (LAMP3) at the PV membrane. In the absence of bacterial protein synthesis, DotA also became depleted from the PV membrane. These data are the first to identify the release/secretion of C. burnetii T4BSS components during axenic growth and the interaction of a T4BSS component with the PV membrane during infection of host cells.
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Affiliation(s)
- Brandon E Luedtke
- Department of Biology, University of Nebraska at Kearney, Kearney, NE 68849, USA
| | - Saugata Mahapatra
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, USA
| | - Erika I Lutter
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, USA
| | - Edward I Shaw
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, USA
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21
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Allgood SC, Romero Dueñas BP, Noll RR, Pike C, Lein S, Neunuebel MR. Legionella Effector AnkX Disrupts Host Cell Endocytic Recycling in a Phosphocholination-Dependent Manner. Front Cell Infect Microbiol 2017; 7:397. [PMID: 28944216 PMCID: PMC5596087 DOI: 10.3389/fcimb.2017.00397] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 08/23/2017] [Indexed: 11/14/2022] Open
Abstract
The facultative intracellular bacterium Legionella pneumophila proliferates within amoebae and human alveolar macrophages, and it is the causative agent of Legionnaires' disease, a life-threatening pneumonia. Within host cells, L. pneumophila establishes a replicative haven by delivering numerous effector proteins into the host cytosol, many of which target membrane trafficking by manipulating the function of Rab GTPases. The Legionella effector AnkX is a phosphocholine transferase that covalently modifies host Rab1 and Rab35. However, a detailed understanding of the biological consequence of Rab GTPase phosphocholination remains elusive. Here, we broaden the understanding of AnkX function by presenting three lines of evidence that it interferes with host endocytic recycling. First, using immunogold transmission electron microscopy, we determined that GFP-tagged AnkX ectopically produced in mammalian cells localizes at the plasma membrane and tubular membrane compartments, sites consistent with targeting the endocytic recycling pathway. Furthermore, the C-terminal region of AnkX was responsible for association with the plasma membrane, and we determined that this region was also able to bind the phosphoinositide lipids PI(3)P and PI(4)P in vitro. Second, we observed that mCherry-AnkX co-localized with Rab35, a regulator of recycling endocytosis and with major histocompatibility class I protein (MHC-I), a key immunoregulatory protein whose recycling from and back to the plasma membrane is Rab35-dependent. Third, we report that during infection of macrophages, AnkX is responsible for the disruption of endocytic recycling of transferrin, and AnkX's phosphocholination activity is critical for this function. These results support the hypothesis that AnkX targets endocytic recycling during host cell infection. Finally, we have demonstrated that the phosphocholination activity of AnkX is also critical for inhibiting fusion of the Legionella-containing vacuole (LCV) with lysosomes.
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Affiliation(s)
- Samual C Allgood
- Department of Biological Sciences, University of DelawareNewark, DE, United States
| | | | - Rebecca R Noll
- Department of Biological Sciences, University of DelawareNewark, DE, United States
| | - Colleen Pike
- Department of Biological Sciences, University of DelawareNewark, DE, United States
| | - Sean Lein
- Department of Biological Sciences, University of DelawareNewark, DE, United States
| | - M Ramona Neunuebel
- Department of Biological Sciences, University of DelawareNewark, DE, United States
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