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Kambarev S, Borghesan E, Miller CN, Myeni S, Celli J. The Brucella abortus Type IV Effector BspA Inhibits MARCH6-Dependent ERAD To Promote Intracellular Growth. Infect Immun 2023; 91:e0013023. [PMID: 37129527 PMCID: PMC10187129 DOI: 10.1128/iai.00130-23] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 04/10/2023] [Indexed: 05/03/2023] Open
Abstract
Brucella abortus, the intracellular causative agent of brucellosis, relies on type IV secretion system (T4SS) effector-mediated modulation of host cell functions to establish a replicative niche, the Brucella-containing vacuole (BCV). Brucella exploits the host's endocytic, secretory, and autophagic pathways to modulate the nature and function of its vacuole from an endocytic BCV (eBCV) to an endoplasmic reticulum (ER)-derived replicative BCV (rBCV) to an autophagic egress BCV (aBCV). A role for the host ER-associated degradation pathway (ERAD) in the B. abortus intracellular cycle was recently uncovered, as it is enhanced by the T4SS effector BspL to control the timing of aBCV-mediated egress. Here, we show that the T4SS effector BspA also interferes with ERAD, yet to promote B. abortus intracellular proliferation. BspA was required for B. abortus replication in bone marrow-derived macrophages and interacts with membrane-associated RING-CH-type finger 6 (MARCH6), a host E3 ubiquitin ligase involved in ERAD. Pharmacological inhibition of ERAD and small interfering RNA (siRNA) depletion of MARCH6 did not affect the replication of wild-type B. abortus but rescued the replication defect of a bspA deletion mutant, while depletion of the ERAD component UbxD8 affected replication of B. abortus and rescued the replication defect of the bspA mutant. BspA affected the degradation of ERAD substrates and destabilized the MARCH6 E3 ligase complex. Taken together, these findings indicate that BspA inhibits the host ERAD pathway via targeting of MARCH6 to promote B. abortus intracellular growth. Our data reveal that targeting ERAD components by type IV effectors emerges as a multifaceted theme in Brucella pathogenesis.
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Affiliation(s)
- Stanimir Kambarev
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Elizabeth Borghesan
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Cheryl N. Miller
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Sebenzile Myeni
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Jean Celli
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
- Department of Microbiology and Molecular Genetics, Larner College of Medicine at the University of Vermont, Burlington, Vermont, USA
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Xie C, Shang Q, Mo C, Xiao Y, Wang G, Xie J, Jiang D, Xiao X. Early Secretory Pathway-Associated Proteins SsEmp24 and SsErv25 Are Involved in Morphogenesis and Pathogenicity in a Filamentous Phytopathogenic Fungus. mBio 2021; 12:e0317321. [PMID: 34933451 PMCID: PMC8689567 DOI: 10.1128/mbio.03173-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 11/15/2021] [Indexed: 12/28/2022] Open
Abstract
Proper protein secretion is critical for fungal development and pathogenesis. However, the potential roles of proteins involved in the early secretory pathway are largely undescribed in filamentous fungi. p24 proteins are cargo receptors that cycle between the endoplasmic reticulum (ER) and Golgi apparatus in the early secretory pathway and recruit cargo proteins to nascent vesicles. This study characterized the function of two p24 family proteins (SsEmp24 and SsErv25) in a phytopathogenic fungus, Sclerotinia sclerotiorum. Both SsEmp24 and SsErv25 were upregulated during the early stages of S. sclerotiorum infection. ΔSsEmp24 mutant and ΔSsErv25 mutant displayed abnormal vegetative growth and sclerotium formation, were defective in infection cushion formation, and showed lower virulence on host plants. ΔSsEmp24 mutant had a more severe abnormal phenotype than ΔSsErv25 mutant, implying that SsEmp24 could play a central role in the early secretory pathway. Similar to their Saccharomyces cerevisiae counterparts, SsEmp24 interacted with SsErv25 and predominantly colocalized in the ER or nuclear envelope. The absence of SsEmp24 or SsErv25 led to defective in protein secretion in S. sclerotiorum, including the pathogenicity-related extracellular hydrolytic enzymes and effectors. It is proposed that SsEmp24 and SsErv25, components in the early secretory pathway, are involved in modulating morphogenesis and pathogenicity in S. sclerotiorum by mediating protein secretion. IMPORTANCE Understanding the reproduction and pathogenesis mechanism of phytopathogens could provide new opinions to effectively control fungal diseases. Although it has been known that effectors and extracellular hydrolytic enzymes secreted by phytopathogenic fungi play important roles in fungus-host interactions, the secretion system for the delivery of virulence factors to the host is still largely undescribed. Although the role of the early secretory pathway-associated p24 proteins in S. cerevisiae has been well characterized, the function of these proteins in filamentous fungi was scarcely known prior to this study. The present research provides evidence that p24 proteins participate in the reproduction and pathogenesis of phytopathogenic fungi through the mediation of protein secretion. This research advances our understanding of p24 proteins in filamentous phytopathogenic fungi. In addition, the candidate cargos of the two p24 proteins, SsEmp24 and SsErv25, were screened out by comparative proteomics, which could aid the identification of novel development and virulence-associated factors in phytopathogenic fungi.
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Affiliation(s)
- Chong Xie
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
| | - Qingna Shang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Hongshan Laboratory, Wuhan, Hubei Province, China
| | - Chenmi Mo
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
| | - Yannong Xiao
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
| | - Gaofeng Wang
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
| | - Jiatao Xie
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Hongshan Laboratory, Wuhan, Hubei Province, China
| | - Daohong Jiang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Hongshan Laboratory, Wuhan, Hubei Province, China
| | - Xueqiong Xiao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, China
- Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China
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Almeida C. A potential third-order role of the host endoplasmic reticulum as a contact site in interkingdom microbial endosymbiosis and viral infection. Environ Microbiol Rep 2021; 13:255-271. [PMID: 33559322 DOI: 10.1111/1758-2229.12938] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The normal functioning of eukaryotic cells depends on the compartmentalization of metabolic processes within specific organelles. Interactions among organelles, such as those between the endoplasmic reticulum (ER) - considered the largest single structure in eukaryotic cells - and other organelles at membrane contact sites (MCSs) have also been suggested to trigger synergisms, including intracellular immune responses against pathogens. In addition to the ER-endogenous functions and ER-organelle MCSs, we present the perspective of a third-order role of the ER as a host contact site for endosymbiotic microbial non-pathogens and pathogens, from endosymbiont bacteria to parasitic protists and viruses. Although understudied, ER-endosymbiont interactions have been observed in a range of eukaryotic hosts, including protists, plants, algae, and metazoans. Host ER interactions with endosymbionts could be an ER function built from ancient, conserved mechanisms selected for communicating with mutualistic endosymbionts in specific life cycle stages, and they may be exploited by pathogens and parasites. The host ER-'guest' interactome and traits in endosymbiotic biology are briefly discussed. The acknowledgment and understanding of these possible mechanisms might reveal novel evolutionary perspectives, uncover the causes of unexplained cellular disorders and suggest new pharmacological targets.
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Affiliation(s)
- Celso Almeida
- ENDOBIOS Biotech®, Praceta Progresso Clube n° 6, 2725-110 Mem-Martins, Portugal
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Kitaeva AB, Gorshkov AP, Kirichek EA, Kusakin PG, Tsyganova AV, Tsyganov VE. General Patterns and Species-Specific Differences in the Organization of the Tubulin Cytoskeleton in Indeterminate Nodules of Three Legumes. Cells 2021; 10:cells10051012. [PMID: 33923032 PMCID: PMC8146709 DOI: 10.3390/cells10051012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [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: 02/28/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 01/28/2023] Open
Abstract
The tubulin cytoskeleton plays an important role in establishing legume–rhizobial symbiosis at all stages of its development. Previously, tubulin cytoskeleton organization was studied in detail in the indeterminate nodules of two legume species, Pisum sativum and Medicago truncatula. General as well as species-specific patterns were revealed. To further the understanding of the formation of general and species-specific microtubule patterns in indeterminate nodules, the tubulin cytoskeleton organization was studied in three legume species (Vicia sativa, Galega orientalis, and Cicer arietinum). It is shown that these species differ in the shape and size of rhizobial cells (bacteroids). Immunolocalization of microtubules revealed the universality of cortical and endoplasmic microtubule organization in the meristematic cells, infected cells of the infection zone, and uninfected cells in nodules of the three species. However, there are differences in the endoplasmic microtubule organization in nitrogen-fixing cells among the species, as confirmed by quantitative analysis. It appears that the differences are linked to bacteroid morphology (both shape and size).
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Dickinson MS, Anderson LN, Webb-Robertson BJM, Hansen JR, Smith RD, Wright AT, Hybiske K. Proximity-dependent proteomics of the Chlamydia trachomatis inclusion membrane reveals functional interactions with endoplasmic reticulum exit sites. PLoS Pathog 2019; 15:e1007698. [PMID: 30943267 PMCID: PMC6464245 DOI: 10.1371/journal.ppat.1007698] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 04/15/2019] [Accepted: 03/12/2019] [Indexed: 11/18/2022] Open
Abstract
Chlamydia trachomatis is the most common cause of bacterial sexually transmitted infection, responsible for millions of infections each year. Despite this high prevalence, the elucidation of the molecular mechanisms of Chlamydia pathogenesis has been difficult due to limitations in genetic tools and its intracellular developmental cycle. Within a host epithelial cell, chlamydiae replicate within a vacuole called the inclusion. Many Chlamydia-host interactions are thought to be mediated by the Inc family of type III secreted proteins that are anchored in the inclusion membrane, but their array of host targets are largely unknown. To investigate how the inclusion membrane proteome changes over the course of an infected cell, we have adapted the APEX2 system of proximity-dependent biotinylation. APEX2 is capable of specifically labeling proteins within a 20 nm radius in living cells. We transformed C. trachomatis to express the enzyme APEX2 fused to known inclusion membrane proteins, allowing biotinylation and purification of inclusion-associated proteins. Using quantitative mass spectrometry against APEX2 labeled samples, we identified over 400 proteins associated with the inclusion membrane at early, middle, and late stages of epithelial cell infection. This system was sensitive enough to detect inclusion interacting proteins early in the developmental cycle, at 8 hours post infection, a previously intractable time point. Mass spectrometry analysis revealed a novel, early association between C. trachomatis inclusions and endoplasmic reticulum exit sites (ERES), functional regions of the ER where COPII-coated vesicles originate. Pharmacological and genetic disruption of ERES function severely restricted early chlamydial growth and the development of infectious progeny. APEX2 is therefore a powerful in situ approach for identifying critical protein interactions on the membranes of pathogen-containing vacuoles. Furthermore, the data derived from proteomic mapping of Chlamydia inclusions has illuminated an important functional role for ERES in promoting chlamydial developmental growth.
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Affiliation(s)
- Mary S. Dickinson
- Department of Global Health, Graduate Program in Pathobiology, University of Washington, Seattle, WA, United States of America
- Department of Medicine, Division of Allergy and Infectious Diseases, Center for Emerging and Reemerging Infectious Disease (CERID), University of Washington, Seattle, WA, United States of America
| | - Lindsey N. Anderson
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | | | - Joshua R. Hansen
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Richard D. Smith
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Aaron T. Wright
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
- The Gene and Linda Voiland College of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, United States of America
| | - Kevin Hybiske
- Department of Global Health, Graduate Program in Pathobiology, University of Washington, Seattle, WA, United States of America
- Department of Medicine, Division of Allergy and Infectious Diseases, Center for Emerging and Reemerging Infectious Disease (CERID), University of Washington, Seattle, WA, United States of America
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Fattouh N, Cazevieille C, Landmann F. Wolbachia endosymbionts subvert the endoplasmic reticulum to acquire host membranes without triggering ER stress. PLoS Negl Trop Dis 2019; 13:e0007218. [PMID: 30893296 PMCID: PMC6426186 DOI: 10.1371/journal.pntd.0007218] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 02/05/2019] [Indexed: 12/15/2022] Open
Abstract
The reproductive parasites Wolbachia are the most common endosymbionts on earth, present in a plethora of arthropod species. They have been introduced into mosquitos to successfully prevent the spread of vector-borne diseases, yet the strategies of host cell subversion underlying their obligate intracellular lifestyle remain to be explored in depth in order to gain insights into the mechanisms of pathogen-blocking. Like some other intracellular bacteria, Wolbachia reside in a host-derived vacuole in order to replicate and escape the immune surveillance. Using here the pathogen-blocking Wolbachia strain from Drosophila melanogaster, introduced into two different Drosophila cell lines, we show that Wolbachia subvert the endoplasmic reticulum to acquire their vacuolar membrane and colonize the host cell at high density. Wolbachia redistribute the endoplasmic reticulum, and time lapse experiments reveal tight coupled dynamics suggesting important signalling events or nutrient uptake. Wolbachia infection however does not affect the tubular or cisternal morphologies. A fraction of endoplasmic reticulum becomes clustered, allowing the endosymbionts to reside in between the endoplasmic reticulum and the Golgi apparatus, possibly modulating the traffic between these two organelles. Gene expression analyses and immunostaining studies suggest that Wolbachia achieve persistent infections at very high titers without triggering endoplasmic reticulum stress or enhanced ERAD-driven proteolysis, suggesting that amino acid salvage is achieved through modulation of other signalling pathways. Wolbachia are a genus of intracellular bacteria living in symbiosis with millions of arthropod species. They have the ability to block the transmission of arboviruses when introduced into mosquito vectors, by interfering with the cellular resources exploited by these viruses. Despite the biomedical interest of this symbiosis, little is known about the mechanisms by which Wolbachia survive and replicate in the host cell. We show here that the membrane composing the Wolbachia vacuole is acquired from the endoplasmic reticulum, a central organelle required for protein and lipid synthesis, and from which originates a vesicular trafficking toward the Golgi apparatus and the secretory pathway. Wolbachia modify the distribution of this organelle which is a potential source of membrane and likely of nutrients as well. In contrast to some intracellular pathogenic bacteria, the effect of Wolbachia on the cell homeostasis does not induce a stress on the endoplasmic reticulum. One of the consequences of such a stress would be an increased proteolysis used to relieve the cell from an excess of misfolded proteins. Incidentally, this suggests that Wolbachia do not acquire amino acids from the host cell through this strategy.
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Affiliation(s)
| | - Chantal Cazevieille
- MRI-COMET, Plateau de microscopie électronique, U1051 INM, Hôpital Saint Eloi, Montpellier, France
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Ghanim M, Achor D, Ghosh S, Kontsedalov S, Lebedev G, Levy A. 'Candidatus Liberibacter asiaticus' Accumulates inside Endoplasmic Reticulum Associated Vacuoles in the Gut Cells of Diaphorina citri. Sci Rep 2017; 7:16945. [PMID: 29208900 PMCID: PMC5717136 DOI: 10.1038/s41598-017-16095-w] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/06/2017] [Indexed: 01/10/2023] Open
Abstract
Citrus greening disease known also as Huanglongbing (HLB) caused by the phloem-limited bacterium 'Candidatus Liberibacter asiaticus' (CLas) has resulted in tremendous losses and the death of millions of trees worldwide. CLas is transmitted by the Asian citrus psyllid Diaphorina citri. The closely-related bacteria 'Candidatus Liberibacter solanacearum' (CLso), associated with vegetative disorders in carrots, is transmitted by the carrot psyllid Bactericera trigonica. A promising approach to prevent the transmission of these pathogens is to interfere with the vector-pathogen interactions, but our understanding of these processes is limited. It was recently reported that CLas induced changes in the nuclear architecture, and activated programmed cell death, in D. citri midgut cells. Here, we used electron and fluorescent microscopy and show that CLas induces the formation of endoplasmic reticulum (ER)-associated bodies. The bacterium recruits those ER structures into Liberibacter containing vacuoles (LCVs), in which bacterial cells seem to propagate. ER- associated LCV formation was unique to CLas, as we could not detect these bodies in B. trigonica infected with CLso. ER recruitment is hypothesized to generate a safe replicative body to escape cellular immune responses in the insect gut. Understanding the molecular interactions that undelay these responses will open new opportunities for controlling CLas.
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Affiliation(s)
- Murad Ghanim
- Department of Entomology, Volcani Center, Rishon LeZion, Israel.
| | - Diann Achor
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA
| | - Saptarshi Ghosh
- Department of Entomology, Volcani Center, Rishon LeZion, Israel
| | | | - Galina Lebedev
- Department of Entomology, Volcani Center, Rishon LeZion, Israel
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA.
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA.
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Murray R, Flora E, Bayne C, Derré I. IncV, a FFAT motif-containing Chlamydia protein, tethers the endoplasmic reticulum to the pathogen-containing vacuole. Proc Natl Acad Sci U S A 2017; 114:12039-12044. [PMID: 29078338 PMCID: PMC5692559 DOI: 10.1073/pnas.1709060114] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Membrane contact sites (MCS) are zones of contact between the membranes of two organelles. At MCS, specific proteins tether the organelles in close proximity and mediate the nonvesicular trafficking of lipids and ions between the two organelles. The endoplasmic reticulum (ER) integral membrane protein VAP is a common component of MCS involved in both tethering and lipid transfer by binding directly to proteins containing a FFAT [two phenylalanines (FF) in an acidic tract (AT)] motif. In addition to maintaining cell homeostasis, MCS formation recently emerged as a mechanism by which intracellular pathogens hijack cellular resources and establish their replication niche. Here, we investigated the mechanism by which the Chlamydia-containing vacuole, termed the inclusion, establishes direct contact with the ER. We show that the Chlamydia protein IncV, which is inserted into the inclusion membrane, displays one canonical and one noncanonical FFAT motif that cooperatively mediated the interaction of IncV with VAP. IncV overexpression was sufficient to bring the ER in close proximity of IncV-containing membranes. Although IncV deletion partially decreased VAP association with the inclusion, it did not suppress the formation of ER-inclusion MCS, suggesting the existence of redundant mechanisms in MCS formation. We propose a model in which IncV acts as one of the primary tethers that contribute to the formation of ER-inclusion MCS. Our results highlight a previously unidentified mechanism of bacterial pathogenesis and support the notion that cooperation of two FFAT motifs may be a common feature of VAP-mediated MCS formation. Chlamydia-host cell interaction therefore constitutes a unique system to decipher the molecular mechanisms underlying MCS formation.
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Affiliation(s)
- Rebecca Murray
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908
| | - Elizabeth Flora
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908
| | - Charlie Bayne
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908
| | - Isabelle Derré
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908
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Zimmermann-Meisse G, Prévost G, Jover E. Above and beyond C5a Receptor Targeting by Staphylococcal Leucotoxins: Retrograde Transport of Panton-Valentine Leucocidin and γ-Hemolysin. Toxins (Basel) 2017; 9:toxins9010041. [PMID: 28117704 PMCID: PMC5308273 DOI: 10.3390/toxins9010041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [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: 11/16/2016] [Revised: 01/10/2017] [Accepted: 01/16/2017] [Indexed: 12/03/2022] Open
Abstract
Various membrane receptors associated with the innate immune response have recently been identified as mediators of the cellular action of Staphylococcus aureus leucotoxins. Two of these, the Panton–Valentine leucotoxin LukS-PV/LukF-PV and the γ-hemolysin HlgC/HlgB, bind the C5a complement-derived peptide receptor. These leucotoxins utilize the receptor to induce intracellular Ca2+ release from internal stores, other than those activated by C5a. The two leucotoxins are internalized with the phosphorylated receptor, but it is unknown whether they divert retrograde transport of the receptor or follow another pathway. Immunolabeling and confocal microscopic techniques were used to analyze the presence of leucotoxins in endosomes, lysosomes, endoplasmic reticulum, and Golgi. The two leucotoxins apparently followed retrograde transport similar to that of the C5a peptide-activated receptor. However, HlgC/HlgB reached the Golgi network very early, whereas LukS-PV/LukF-PV followed slower kinetics. The HlgC/HlgB leucotoxin remained in neutrophils 6 h after a 10-min incubation of the cells in the presence of the toxin with no signs of apoptosis, whereas apoptosis was observed 3 h after neutrophils were incubated with LukS-PV/LukF-PV. Such retrograde transport of leucotoxins provides a novel understanding of the cellular effects initiated by sublytic concentrations of these toxins.
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Affiliation(s)
- Gaëlle Zimmermann-Meisse
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
| | - Gilles Prévost
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
| | - Emmanuel Jover
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
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10
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Taguchi Y, Imaoka K, Kataoka M, Uda A, Nakatsu D, Horii-Okazaki S, Kunishige R, Kano F, Murata M. Yip1A, a novel host factor for the activation of the IRE1 pathway of the unfolded protein response during Brucella infection. PLoS Pathog 2015; 11:e1004747. [PMID: 25742138 PMCID: PMC4350842 DOI: 10.1371/journal.ppat.1004747] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 02/12/2015] [Indexed: 12/03/2022] Open
Abstract
Brucella species replicate within host cells in the form of endoplasmic reticulum (ER)-derived vacuoles. The mechanisms by which the bacteria are sequestered into such vacuoles and obtain a continuous membrane supply for their replication remain to be elucidated. In the present study, we provided several lines of evidence that demonstrate the mechanism by which B. abortus acquires the ER-derived membrane. First, during Brucella infection, the IRE1 pathway, but not the PERK and ATF6 pathways, of the unfolded protein response (UPR) was activated in a time-dependent manner, and the COPII vesicle components Sar1, Sec23, and Sec24D were upregulated. Second, a marked accretion of ER-derived vacuoles was observed around replicating bacteria using fluorescent microscopy and electron microscopy. Third, we identified a novel host factor, Yip1A, for the activation of the IRE1 pathway in response to both tunicamycin treatment and infection with B. abortus. We found that Yip1A is responsible for the phosphorylation of IRE1 through high-order assembly of Ire1 molecules at ER exit sites (ERES) under the UPR conditions. In Yip1A-knockdown cells, B. abortus failed to generate the ER-derived vacuoles, and remained in endosomal/lysosomal compartments. These results indicate that the activation of the IRE1 pathway and the subsequent formation of ER-derived vacuoles are critical for B. abortus to establish a safe replication niche, and that Yip1A is indispensable for these processes. Furthermore, we showed that the autophagy-related proteins Atg9 and WIPI1, but not DFCP1, were required for the biogenesis of the ER-derived membrane compartments. On the basis of our findings, we propose a model for intracellular Brucella replication that exploits the host UPR and ER-derived vacuole formation machineries, both of which depend on Yip1A-mediated IRE1 activation. The genus Brucella is a serious intracellular pathogen that causes brucellosis in a wide range of animals including humans. Infection with Brucella spp. results in a significant economic and health burden due to its high infectivity, chronic nature, and difficulties in vaccine production. Better understanding of the host-pathogen interplay that supports Brucella replication is essential for the development of effective treatments for brucellosis. The unfolded protein response (UPR) has been implicated in the pathogenesis of several viral and bacterial infections. These pathogens modulate individual pathways of the UPR to enable their replication in host cells. Autophagy has also been linked to the survival of several intracellular pathogens. They subvert autophagic machineries of host cells to establish their safe replication niche. In the present study, we show that the activation of the IRE1 pathway of the UPR and the subsequent formation of ER-derived vacuoles are crucial for intracellular survival of B. abortus. In addition, we identified a novel host factor Yip1A that is responsible for these processes. Characterization of the function of Yip1A will provide new insights into the molecular mechanisms by which Brucella spp. replicates in host cells.
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Affiliation(s)
- Yuki Taguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
| | - Koichi Imaoka
- Department of Veterinary Science, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan
| | - Michiyo Kataoka
- Department of Pathology, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan
| | - Akihiko Uda
- Department of Veterinary Science, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan
| | - Daiki Nakatsu
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
| | - Sakuya Horii-Okazaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
| | - Rina Kunishige
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
| | - Fumi Kano
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
- PRESTO, Japan Science and Technology Agent, Kawaguchi, Saitama, Japan
| | - Masayuki Murata
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
- * E-mail:
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11
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Hubber A, Arasaki K, Nakatsu F, Hardiman C, Lambright D, De Camilli P, Nagai H, Roy CR. The machinery at endoplasmic reticulum-plasma membrane contact sites contributes to spatial regulation of multiple Legionella effector proteins. PLoS Pathog 2014; 10:e1004222. [PMID: 24992562 PMCID: PMC4081824 DOI: 10.1371/journal.ppat.1004222] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Accepted: 05/16/2014] [Indexed: 11/18/2022] Open
Abstract
The Dot/Icm system of the intracellular pathogen Legionella pneumophila has the capacity to deliver over 270 effector proteins into host cells during infection. Important questions remain as to spatial and temporal mechanisms used to regulate such a large array of virulence determinants after they have been delivered into host cells. Here we investigated several L. pneumophila effector proteins that contain a conserved phosphatidylinositol-4-phosphate (PI4P)-binding domain first described in the effector DrrA (SidM). This PI4P binding domain was essential for the localization of effectors to the early L. pneumophila-containing vacuole (LCV), and DrrA-mediated recruitment of Rab1 to the LCV required PI4P-binding activity. It was found that the host cell machinery that regulates sites of contact between the plasma membrane (PM) and the endoplasmic reticulum (ER) modulates PI4P dynamics on the LCV to control localization of these effectors. Specifically, phosphatidylinositol-4-kinase IIIα (PI4KIIIα) was important for generating a PI4P signature that enabled L. pneumophila effectors to localize to the PM-derived vacuole, and the ER-associated phosphatase Sac1 was involved in metabolizing the PI4P on the vacuole to promote the dissociation of effectors. A defect in L. pneumophila replication in macrophages deficient in PI4KIIIα was observed, highlighting that a PM-derived PI4P signature is critical for biogenesis of a vacuole that supports intracellular multiplication of L. pneumophila. These data indicate that PI4P metabolism by enzymes controlling PM-ER contact sites regulate the association of L. pneumophila effectors to coordinate early stages of vacuole biogenesis. The intracellular pathogen Legionella pneumophila encodes at least 270 effectors that modulate trafficking of the pathogen-occupied vacuole. The mechanisms by which effectors are controlled in host cells are of key interest. Spatial and temporal regulation of effector function has been proposed to involve effector binding to host phosphoinositides. We present results showing that L. pneumophila utilizes the host kinase PI4KIIIα to generate PI4P on the bacterial vacuole and this signature mediates the localization of DrrA and subsequent recruitment of the GTPase Rab1. Additionally, it was found that the host PI4P phosphatase Sac1 was involved in consuming PI4P on the vacuole, which reduced DrrA-mediated recruitment of Rab1 to the LCV. Our data supports the recent concept that PI4KIIIα is important for generation of the plasma-membrane pool of PI4P in host cells, and demonstrates a functional consequence for PI4P-binding by an L. pneumophila effector protein.
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Affiliation(s)
- Andree Hubber
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, Japan
- * E-mail: (AH); (CRR)
| | - Kohei Arasaki
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo, Japan
| | - Fubito Nakatsu
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Camille Hardiman
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - David Lambright
- Program in Molecular Medicine and Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Pietro De Camilli
- Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, Japan
| | - Hiroki Nagai
- Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, Japan
| | - Craig R. Roy
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail: (AH); (CRR)
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12
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Akamatsu A, Wong HL, Fujiwara M, Okuda J, Nishide K, Uno K, Imai K, Umemura K, Kawasaki T, Kawano Y, Shimamoto K. An OsCEBiP/OsCERK1-OsRacGEF1-OsRac1 module is an essential early component of chitin-induced rice immunity. Cell Host Microbe 2014; 13:465-76. [PMID: 23601108 DOI: 10.1016/j.chom.2013.03.007] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 01/17/2013] [Accepted: 03/04/2013] [Indexed: 11/30/2022]
Abstract
OsCEBiP, a chitin-binding protein, and OsCERK1, a receptor-like kinase, are plasma membrane (PM) proteins that form a receptor complex essential for fungal chitin-driven immune responses in rice. The signaling events immediately following chitin perception are unclear. Investigating the spatiotemporal regulation of the rice small GTPase OsRac1, we find that chitin induces rapid activation of OsRac1 at the PM. Searching for OsRac1 interactors, we identified OsRacGEF1 as a guanine nucleotide exchange factor for OsRac1. OsRacGEF1 interacts with OsCERK1 and is activated when its C-terminal S549 is phosphorylated by the cytoplasmic domain of OsCERK1 in response to chitin. Activated OsRacGEF1 is required for chitin-driven immune responses and resistance to rice blast fungus infection. Further, a protein complex including OsCERK1 and OsRacGEF1 is transported from the endoplasmic reticulum to the PM. Collectively, our results suggest that OsCEBiP, OsCERK1, OsRacGEF1, and OsRac1 function as key components of a "defensome" critically engaged early during chitin-induced immunity.
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Affiliation(s)
- Akira Akamatsu
- Laboratory of Plant Molecular Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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13
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Dumoux M, Clare DK, Saibil HR, Hayward RD. Chlamydiae assemble a pathogen synapse to hijack the host endoplasmic reticulum. Traffic 2012; 13:1612-27. [PMID: 22901061 PMCID: PMC3533787 DOI: 10.1111/tra.12002] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 08/15/2012] [Accepted: 08/17/2012] [Indexed: 12/22/2022]
Abstract
Chlamydiae are obligate intracellular bacterial pathogens that replicate within a specialized membrane-bound compartment, termed an 'inclusion'. The inclusion membrane is a critical host-pathogen interface, yet the extent of its interaction with cellular organelles and the origin of this membrane remain poorly defined. Here we show that the host endoplasmic reticulum (ER) is specifically recruited to the inclusion, and that key rough ER (rER) proteins are enriched on and translocated into the inclusion. rER recruitment is a Chlamydia-orchestrated process that occurs independently of host trafficking. Generation of infectious progeny requires an intact ER, since ER vacuolation early during infection stalls inclusion development, whereas disruption post ER recruitment bursts the inclusion. Electron tomography and immunolabelling of Chlamydia-infected cells reveal 'pathogen synapses' at which ordered arrays of chlamydial type III secretion complexes connect to the inclusion membrane only at rER contact sites. Our data show a supramolecular assembly involved in pathogen hijack of a key host organelle.
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Affiliation(s)
- Maud Dumoux
- Institute of Structural and Molecular Biology, Birkbeck & University College LondonMalet Street, London, WC1E 7HX, UK
| | - Daniel K Clare
- Department of Crystallography, Institute of Structural and Molecular BiologyBirkbeck, Malet Street, London, WC1E 7HX, UK
| | - Helen R Saibil
- Department of Crystallography, Institute of Structural and Molecular BiologyBirkbeck, Malet Street, London, WC1E 7HX, UK
| | - Richard D Hayward
- Institute of Structural and Molecular Biology, Birkbeck & University College LondonMalet Street, London, WC1E 7HX, UK
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14
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Qiang X, Zechmann B, Reitz MU, Kogel KH, Schäfer P. The mutualistic fungus Piriformospora indica colonizes Arabidopsis roots by inducing an endoplasmic reticulum stress-triggered caspase-dependent cell death. Plant Cell 2012; 24:794-809. [PMID: 22337916 PMCID: PMC3315247 DOI: 10.1105/tpc.111.093260] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 01/16/2012] [Accepted: 01/24/2012] [Indexed: 05/19/2023]
Abstract
In Arabidopsis thaliana roots, the mutualistic fungus Piriformospora indica initially colonizes living cells, which die as the colonization proceeds. We aimed to clarify the molecular basis of this colonization-associated cell death. Our cytological analyses revealed endoplasmic reticulum (ER) swelling and vacuolar collapse in invaded cells, indicative of ER stress and cell death during root colonization. Consistent with this, P. indica-colonized plants were hypersensitive to the ER stress inducer tunicamycin. By clear contrast, ER stress sensors bZIP60 and bZIP28 as well as canonical markers for the ER stress response pathway, termed the unfolded protein response (UPR), were suppressed at the same time. Arabidopsis mutants compromised in caspase 1-like activity, mediated by cell death-regulating vacuolar processing enzymes (VPEs), showed reduced colonization and decreased cell death incidence. We propose a previously unreported microbial invasion strategy during which P. indica induces ER stress but inhibits the adaptive UPR. This disturbance results in a VPE/caspase 1-like-mediated cell death, which is required for the establishment of the symbiosis. Our results suggest the presence of an at least partially conserved ER stress-induced caspase-dependent cell death pathway in plants as has been reported for metazoans.
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Affiliation(s)
- Xiaoyu Qiang
- Research Centre for Biosystems, Land Use, and Nutrition, Justus Liebig University, 35392 Giessen, Germany
| | - Bernd Zechmann
- Institute of Plant Sciences, University of Graz, 8010 Graz, Austria
| | - Marco U. Reitz
- Research Centre for Biosystems, Land Use, and Nutrition, Justus Liebig University, 35392 Giessen, Germany
| | - Karl-Heinz Kogel
- Research Centre for Biosystems, Land Use, and Nutrition, Justus Liebig University, 35392 Giessen, Germany
| | - Patrick Schäfer
- Research Centre for Biosystems, Land Use, and Nutrition, Justus Liebig University, 35392 Giessen, Germany
- Address correspondence to
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Lim YJ, Choi JA, Choi HH, Cho SN, Kim HJ, Jo EK, Park JK, Song CH. Endoplasmic reticulum stress pathway-mediated apoptosis in macrophages contributes to the survival of Mycobacterium tuberculosis. PLoS One 2011; 6:e28531. [PMID: 22194844 PMCID: PMC3237454 DOI: 10.1371/journal.pone.0028531] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 11/09/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Apoptosis is thought to play a role in host defenses against intracellular pathogens, including Mycobacterium tuberculosis (Mtb), by preventing the release of intracellular components and the spread of mycobacterial infection. This study aims to investigate the role of endoplasmic reticulum (ER) stress mediated apoptosis in mycobacteria infected macrophages. METHODOLOGY/PRINCIPAL FINDINGS Here, we demonstrate that ER stress-induced apoptosis is associated with Mtb H37Rv-induced cell death of Raw264.7 murine macrophages. We have shown that Mtb H37Rv induced apoptosis are involved in activation of caspase-12, which resides on the cytoplasmic district of the ER. Mtb infection increase levels of other ER stress indicators in a time-dependent manner. Phosphorylation of eIF2α was decreased gradually after Mtb H37Rv infection signifying that Mtb H37Rv infection may affect eIF2α phosphorylation in an attempt to survive within macrophages. Interestingly, the survival of mycobacteria in macrophages was enhanced by silencing CHOP expression. In contrast, survival rate of mycobacteria was reduced by phosphorylation of the eIF2α. Futhermore, the levels of ROS, NO or CHOP expression were significantly increased by live Mtb H37Rv compared to heat-killed Mtb H37Rv indicating that live Mtb H37Rv could induce ER stress response. CONCLUSION/SIGNIFICANCE These findings indicate that eIF2α/CHOP pathway may influence intracellular survival of Mtb H37Rv in macrophages and only live Mtb H37Rv can induce ER stress response. The data support the ER stress pathway plays an important role in the pathogenesis and persistence of mycobacteria.
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Affiliation(s)
- Yun-Ji Lim
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Ji-Ae Choi
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Hong-Hee Choi
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
- Infection Signaling Network Research Center, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Soo-Na Cho
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Hwa-Jung Kim
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
- Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Eun-Kyeong Jo
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
- Infection Signaling Network Research Center, College of Medicine, Chungnam National University, Daejeon, South Korea
- Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Jeong-Kyu Park
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
- Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - Chang-Hwa Song
- Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea
- Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon, South Korea
- * E-mail:
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16
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Derré I, Swiss R, Agaisse H. The lipid transfer protein CERT interacts with the Chlamydia inclusion protein IncD and participates to ER-Chlamydia inclusion membrane contact sites. PLoS Pathog 2011; 7:e1002092. [PMID: 21731489 PMCID: PMC3121800 DOI: 10.1371/journal.ppat.1002092] [Citation(s) in RCA: 206] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 04/04/2011] [Indexed: 12/21/2022] Open
Abstract
Bacterial pathogens that reside in membrane bound compartment manipulate the host cell machinery to establish and maintain their intracellular niche. The hijacking of inter-organelle vesicular trafficking through the targeting of small GTPases or SNARE proteins has been well established. Here, we show that intracellular pathogens also establish direct membrane contact sites with organelles and exploit non-vesicular transport machinery. We identified the ER-to-Golgi ceramide transfer protein CERT as a host cell factor specifically recruited to the inclusion, a membrane-bound compartment harboring the obligate intracellular pathogen Chlamydia trachomatis. We further showed that CERT recruitment to the inclusion correlated with the recruitment of VAPA/B-positive tubules in close proximity of the inclusion membrane, suggesting that ER-Inclusion membrane contact sites are formed upon C. trachomatis infection. Moreover, we identified the C. trachomatis effector protein IncD as a specific binding partner for CERT. Finally we showed that depletion of either CERT or the VAP proteins impaired bacterial development. We propose that the presence of IncD, CERT, VAPA/B, and potentially additional host and/or bacterial factors, at points of contact between the ER and the inclusion membrane provides a specialized metabolic and/or signaling microenvironment favorable to bacterial development.
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Affiliation(s)
- Isabelle Derré
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America.
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Choi CH, DeGuzman JV, Lamont RJ, Yilmaz Ö. Genetic transformation of an obligate anaerobe, P. gingivalis for FMN-green fluorescent protein expression in studying host-microbe interaction. PLoS One 2011; 6:e18499. [PMID: 21525983 PMCID: PMC3078116 DOI: 10.1371/journal.pone.0018499] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 03/01/2011] [Indexed: 11/26/2022] Open
Abstract
The recent introduction of “oxygen-independent” flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) is of major interest to both eukaryotic and prokaryotic microbial biologists. Accordingly, we demonstrate for the first time that an obligate anaerobe, the successful opportunistic pathogen of the oral cavity, Porphyromonas gingivalis, can be genetically engineered for expression of the non-toxic green FbFP. The resulting transformants are functional for studying dynamic bacterial processes in living host cells. The visualization of the transformed P. gingivalis (PgFbFP) revealed strong fluorescence that reached a maximum emission at 495 nm as determined by fluorescence microscopy and spectrofluorometry. Human primary gingival epithelial cells (GECs) were infected with PgFbFP and the bacterial invasion of host cells was analyzed by a quantitative fluorescence microscopy and antibiotic protection assays. The results showed similar levels of intracellular bacteria for both wild type and PgFbFP strains. In conjunction with organelle specific fluorescent dyes, utilization of the transformed strain provided direct and accurate determination of the live/metabolically active P. gingivalis' trafficking in the GECs over time. Furthermore, the GECs were co-infected with PgFbFP and the ATP-dependent Clp serine protease-deficient mutant (ClpP-) to study the differential fates of the two strains within the same host cells. Quantitative co-localization analyses displayed the intracellular PgFbFP significantly associated with the endoplasmic reticulum network, whereas the majority of ClpP- organisms trafficked into the lysosomes. Hence, we have developed a novel and reliable method to characterize live host cell-microbe interactions and demonstrated the adaptability of FMN-green fluorescent protein for studying persistent host infections induced by obligate anaerobic organisms.
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Affiliation(s)
- Chul Hee Choi
- Department of Periodontology, University of Florida, Gainesville, Florida, United States of America
| | - Jefferson V. DeGuzman
- Department of Periodontology, University of Florida, Gainesville, Florida, United States of America
| | - Richard J. Lamont
- Center for Oral Health and Systemic Disease, University of Louisville, Louisville, Kentucky, United States of America
| | - Özlem Yilmaz
- Department of Periodontology, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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Abstract
Waddlia chondrophila is an obligate intracellular bacterium considered as a potential agent of abortion in both humans and bovines. This member of the order Chlamydiales multiplies rapidly within human macrophages and induces lysis of the infected cells. To understand how this Chlamydia-like micro-organism invades and proliferates within host cells, we investigated its trafficking within monocyte-derived human macrophages. Vacuoles containing W. chondrophila acquired the early endosomal marker EEA1 during the first 30 min following uptake. However, the live W. chondrophila-containing vacuoles never co-localized with late endosome and lysosome markers. Instead of interacting with the endosomal pathway, W. chondrophila immediately co-localized with mitochondria and, shortly after, with endoplasmic reticulum- (ER-) resident proteins such as calnexin and protein disulfide isomerase. The acquisition of mitochondria and ER markers corresponds to the beginning of bacterial replication. It is noteworthy that mitochondrion recruitment to W. chondrophila inclusions is prevented only by simultaneous treatment with the microtubule and actin cytoskeleton-disrupting agents nocodazole and cytochalasin D. In addition, brefeldin A inhibits the replication of W. chondrophila, supporting a role for COPI-dependent trafficking in the biogenesis of the bacterial replicating vacuole. W. chondrophila probably survives within human macrophages by evading the endocytic pathway and by associating with mitochondria and the ER. The intracellular trafficking of W. chondrophila in human macrophages represents a novel route that differs strongly from that used by other members of the order Chlamydiales.
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Affiliation(s)
- Antony Croxatto
- Center for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland
| | - Gilbert Greub
- Center for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland
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19
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Fugier E, Salcedo SP, de Chastellier C, Pophillat M, Muller A, Arce-Gorvel V, Fourquet P, Gorvel JP. The glyceraldehyde-3-phosphate dehydrogenase and the small GTPase Rab 2 are crucial for Brucella replication. PLoS Pathog 2009; 5:e1000487. [PMID: 19557163 PMCID: PMC2695806 DOI: 10.1371/journal.ppat.1000487] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 05/27/2009] [Indexed: 12/21/2022] Open
Abstract
The intracellular pathogen Brucella abortus survives and replicates inside host cells within an endoplasmic reticulum (ER)-derived replicative organelle named the “Brucella-containing vacuole” (BCV). Here, we developed a subcellular fractionation method to isolate BCVs and characterize for the first time the protein composition of its replicative niche. After identification of BCV membrane proteins by 2 dimensional (2D) gel electrophoresis and mass spectrometry, we focused on two eukaryotic proteins: the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the small GTPase Rab 2 recruited to the vacuolar membrane of Brucella. These proteins were previously described to localize on vesicular and tubular clusters (VTC) and to regulate the VTC membrane traffic between the endoplasmic reticulum (ER) and the Golgi. Inhibition of either GAPDH or Rab 2 expression by small interfering RNA strongly inhibited B. abortus replication. Consistent with this result, inhibition of other partners of GAPDH and Rab 2, such as COPI and PKC ι, reduced B. abortus replication. Furthermore, blockage of Rab 2 GTPase in a GDP-locked form also inhibited B. abortus replication. Bacteria did not fuse with the ER and instead remained in lysosomal-associated membrane vacuoles. These results reveal an essential role for GAPDH and the small GTPase Rab 2 in B. abortus virulence within host cells. A key determinant for intracellular pathogenic bacteria to ensure their virulence within host cells is their ability to bypass the endocytic pathway and to reach a safe replication niche. Brucella bacteria reach the endoplasmic reticulum (ER) to create their replicating niche called the Brucella-containing vacuole (BCV). The ER is a suitable strategic place for pathogenic Brucella. Bacteria can be hidden from host cell defences to persist within the host, and can take advantage of the membrane reservoir delivered by the ER to replicate. Interactions between BCV and the ER lead to the presence of ER proteins on the BCV membrane. Currently, no other proteins (eukaryotic or prokaryotic) have yet been associated with the BCV membrane. Here we show that non-ER related proteins are also present on the BCV membrane, in particular, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the small GTPase Rab 2 known to be located on secretory vesicles that traffic between the ER and the Golgi apparatus. GAPDH and the small GTPase Rab 2 are involved in Brucella replication at late post-infection. Similarly, integrity of secretory vesicle trafficking is also necessary for Brucella replication. Here, we show that recruitment of the two eukaryotic proteins GAPDH and Rab 2 on BCV membranes is necessary for the establishment of the replicative niche by sustaining interactions between the ER and secretory membrane vesicles.
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Affiliation(s)
- Emilie Fugier
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Suzana P. Salcedo
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Chantal de Chastellier
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Matthieu Pophillat
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Alexandre Muller
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Vilma Arce-Gorvel
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Patrick Fourquet
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
| | - Jean-Pierre Gorvel
- Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), UMR6546, Marseille, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U631, Marseille, France
- Centre National de la Recherche Scientifique (CNRS), UMR6102, Marseille, France
- * E-mail:
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Richie DL, Hartl L, Aimanianda V, Winters MS, Fuller KK, Miley MD, White S, McCarthy JW, Latgé JP, Feldmesser M, Rhodes JC, Askew DS. A role for the unfolded protein response (UPR) in virulence and antifungal susceptibility in Aspergillus fumigatus. PLoS Pathog 2009; 5:e1000258. [PMID: 19132084 PMCID: PMC2606855 DOI: 10.1371/journal.ppat.1000258] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 12/08/2008] [Indexed: 01/12/2023] Open
Abstract
Filamentous fungi rely heavily on the secretory pathway, both for the delivery of cell wall components to the hyphal tip and the production and secretion of extracellular hydrolytic enzymes needed to support growth on polymeric substrates. Increased demand on the secretory system exerts stress on the endoplasmic reticulum (ER), which is countered by the activation of a coordinated stress response pathway termed the unfolded protein response (UPR). To determine the contribution of the UPR to the growth and virulence of the filamentous fungal pathogen Aspergillus fumigatus, we disrupted the hacA gene, encoding the major transcriptional regulator of the UPR. The ΔhacA mutant was unable to activate the UPR in response to ER stress and was hypersensitive to agents that disrupt ER homeostasis or the cell wall. Failure to induce the UPR did not affect radial growth on rich medium at 37°C, but cell wall integrity was disrupted at 45°C, resulting in a dramatic loss in viability. The ΔhacA mutant displayed a reduced capacity for protease secretion and was growth-impaired when challenged to assimilate nutrients from complex substrates. In addition, the ΔhacA mutant exhibited increased susceptibility to current antifungal agents that disrupt the membrane or cell wall and had attenuated virulence in multiple mouse models of invasive aspergillosis. These results demonstrate the importance of ER homeostasis to the growth and virulence of A. fumigatus and suggest that targeting the UPR, either alone or in combination with other antifungal drugs, would be an effective antifungal strategy. The pathogenic mold Aspergillus fumigatus is the leading cause of airborne fungal infections in immunocompromised patients. The fungus normally resides in compost, an environment that challenges the organism to obtain nutrients by degrading complex organic polymers. This is accomplished by secreted enzymes, some of which may also contribute to nutrient acquisition during infection. Extracellular enzymes are folded in the endoplasmic reticulum (ER) prior to secretion. If the folding capacity of the ER is overwhelmed by increased secretory demand, the resulting ER stress triggers an adaptive response termed the unfolded protein response (UPR). In this study, we uncover a previously unknown function for the master transcriptional regulator of the UPR, HacA, in fungal virulence. In the absence of HacA, A. fumigatus was unable to secrete high levels of proteins and had reduced virulence in mice. In addition, loss of HacA caused a cell wall defect and increased susceptibility to two major classes of antifungal drugs used for the treatment of aspergillosis. These findings demonstrate that A. fumigatus relies on HacA for growth in the host environment and suggest that therapeutic targeting of the UPR could have merit against A. fumigatus, as well as other eukaryotic pathogens with highly developed secretory systems.
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Affiliation(s)
- Daryl L. Richie
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Lukas Hartl
- Unité des Aspergillus, Institut Pasteur, Paris, France
| | | | - Michael S. Winters
- Division of Infectious Diseases, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Kevin K. Fuller
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Michael D. Miley
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Stephanie White
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Jason W. McCarthy
- Division of Infectious Diseases, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | | | - Marta Feldmesser
- Division of Infectious Diseases, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Obstetrics & Gynecology and Women’s Health, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Judith C. Rhodes
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- * E-mail:
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Snijder EJ, van der Meer Y, Zevenhoven-Dobbe J, Onderwater JJM, van der Meulen J, Koerten HK, Mommaas AM. Ultrastructure and origin of membrane vesicles associated with the severe acute respiratory syndrome coronavirus replication complex. J Virol 2006; 80:5927-40. [PMID: 16731931 PMCID: PMC1472606 DOI: 10.1128/jvi.02501-05] [Citation(s) in RCA: 391] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Accepted: 04/03/2006] [Indexed: 12/14/2022] Open
Abstract
The RNA replication complexes of mammalian positive-stranded RNA viruses are generally associated with (modified) intracellular membranes, a feature thought to be important for creating an environment suitable for viral RNA synthesis, recruitment of host components, and possibly evasion of host defense mechanisms. Here, using a panel of replicase-specific antisera, we have analyzed the earlier stages of severe acute respiratory syndrome coronavirus (SARS-CoV) infection in Vero E6 cells, in particular focusing on the subcellular localization of the replicase and the ultrastructure of the associated membranes. Confocal immunofluorescence microscopy demonstrated the colocalization, throughout infection, of replicase cleavage products containing different key enzymes for SARS-CoV replication. Electron microscopy revealed the early formation and accumulation of typical double-membrane vesicles, which probably carry the viral replication complex. The vesicles appear to be fragile, and their preservation was significantly improved by using cryofixation protocols and freeze substitution methods. In immunoelectron microscopy, the virus-induced vesicles could be labeled with replicase-specific antibodies. Opposite to what was described for mouse hepatitis virus, we did not observe the late relocalization of specific replicase subunits to the presumed site of virus assembly, which was labeled using an antiserum against the viral membrane protein. This conclusion was further supported using organelle-specific marker proteins and electron microscopy. Similar morphological studies and labeling experiments argued against the previously proposed involvement of the autophagic pathway as the source for the vesicles with which the replicase is associated and instead suggested the endoplasmic reticulum to be the most likely donor of the membranes that carry the SARS-CoV replication complex.
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Affiliation(s)
- Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, 2300 RC Leiden, The Netherlands.
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Abstract
Legionella pneumophila is an intracellular pathogen that replicates in a unique vacuole that avoids endocytic maturation. Previous studies have shown host vesicles attached to the L. pneumophila-containing vacuole (LCV) minutes after uptake. Here we examine the origin and content of these vesicles by electron microscopy (EM). Our data demonstrate that the attached vesicles are derived from endoplasmic reticulum (ER) based the presence of the resident ER proteins glucose-6-phosphatase, protein disulphide isomerase (PDI) and proteins having the ER-retention signal lysine-aspartic acid-glutamic acid-leucine (KDEL). After tethering occurred, ER markers inside of attached vesicles were delivered into the lumen of the LCV, indicating ER fusion. Treatment of cells with brefeldin A did not interfere with the attachment of ER vesicles with the LCV, suggesting that tethering of these vesicles does not require activities mediated by ADP-ribosylation factor (ARF). ER vesicles were not tethered to the LCV in cells producing the Sar1H79G protein, indicating that vesicles produced by the Sar1/CopII system are necessary for vesicle attachment. From these data we conclude that formation of the organelle that supports L. pneumophila replication is a two-stage process that involves remodelling of the LCV by early secretory vesicles produced by the Sar1/CopII system, followed by attachment and fusion of ER.
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Affiliation(s)
- Camenzind G Robinson
- Department of Cell Biology, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
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23
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Abstract
The endoplasmic reticulum (ER) is a crucial intracellular organelle that is involved in the biosynthesis of cellular molecules, including proteins, carbohydrates and lipids. These become constituents of the ER or are transported to the Golgi, plasma membrane, endosomes and lysosomes. The ER is involved in the transport of both MHC class I and class II complexes to the cell surface. It is the site of peptide loading onto MHC class I molecules, and it is important for regulation of the secretion of soluble immune mediators. Perturbation in ER–Golgi biogenesis affects antigen presentation and immune effector functions, so it is not surprising that the ER is a target for some pathogens. Several pathogens have developed strategies to modulate phagosome maturation and therefore avoid phagosome–lysosome fusion and the subsequent degradation of the pathogen: for example, by generating an ER-derived vacuole. In some cases, this has the added benefit of disrupting ER function. Toxoplasma gondii, Brucella spp. and Legionella pneumophila depend on ER-derived niches for growth, but the precise effects of these pathogen–ER interactions on the immune response are still unclear. Several viruses target the ER and interfere with antigen presentation by MHC class I molecules: for example, hepatitis C virus and human cytomegalovirus. Despite this, the ER contributes to host defence against microorganisms, through its role in autophagy, as well as through the ER stress response and the interferon-induced ER-resident proteins (such as viperin and the p47 GTPases).
Different pathogens have evolved distinct strategies to promote their survival in host cells. This Review describes the contribution of the endoplasmic reticulum to host defence and the mechanisms by which pathogens interacting with the endoplasmic reticulum subvert the host immune response. A key determinant for the survival of intracellular pathogens is their ability to subvert the cellular processes of the host to establish a compartment that allows replication. Although most microorganisms internalized by host cells are efficiently cleared following fusion with lysosomes, many pathogens have evolved mechanisms to escape this degradation. In this Review, we provide insight into the molecular processes that are targeted by pathogens that interact with the endoplasmic reticulum and thereby subvert the immune response, ensure their survival intracellularly and cause disease. We also discuss how the endoplasmic reticulum 'strikes back' and controls microbial growth.
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Affiliation(s)
- Craig R. Roy
- Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, 065362 Connecticut USA
| | - Suzana P. Salcedo
- Centre dImmunologie INSERM-CNRS de Marseille-Luminy, Case 906, Marseille, 13288 Cedex 9 France
| | - Jean-Pierre E. Gorvel
- Centre dImmunologie INSERM-CNRS de Marseille-Luminy, Case 906, Marseille, 13288 Cedex 9 France
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24
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Abstract
Bacteria of the genus Brucella are intracellular pathogens capable of survival and replication within macrophages of mammalian hosts. Recent advances have shed light on virulence factors and host functions involved at various stages of the Brucella intracellular life cycle. This review focuses on how this pathogen uses multiple strategies to circumvent macrophage defense mechanisms and generate an organelle permissive for replication.
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Affiliation(s)
- Jean Celli
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton MT 59840, USA.
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25
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Abstract
Subcellular events of Erysiphe cichoracearum infections of epidermal cells were visualized in living tissues of Arabidopsis plants carrying various green fluorescent protein (GFP)-tagged organelles via laser scanning confocal microscopy. Early in the infection sequence, cytoplasm and organelles moved towards penetration sites and accumulated near penetration pegs. Peroxisomes appeared to accumulate preferentially relative to the cytoplasm at penetration sites. Another early event, which preceded haustorium formation, was the aggregation of some GFP-tagged plasma membrane marker proteins into rings around penetration sites, which extended across cell-wall boundaries into neighboring cells. This feature localized to sites where papillae were deposited. The extrahaustorial membrane (EHM) encases the fungal feeding structure, the haustorium, separating it from the host cytoplasm. Eight plasma membrane markers were excluded from the EHM and remained in a collar-like formation around the haustorial neck. These observations support the suggestions that the EHM is a unique, specialized membrane and is different from the plasma membrane. Our results suggested two possibilities for the origin of the EHM: invagination of the plasma membrane coupled with membrane differentiation; or de novo synthesis of the EHM by targeted vesicle trafficking.
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Affiliation(s)
- Serry Koh
- Carnegie Institution, Department of Plant Biology, 260 Panama St, Stanford, CA 93405, USA
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Li Z, Solomon JM, Isberg RR. Dictyostelium discoideum strains lacking the RtoA protein are defective for maturation of the Legionella pneumophila replication vacuole. Cell Microbiol 2005; 7:431-42. [PMID: 15679845 DOI: 10.1111/j.1462-5822.2004.00472.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To identify host proteins involved in Legionella pneumophila intracellular replication, the soil amoeba Dictyostelium discoideum was analysed. The absence of the amoebal RtoA protein is demonstrated here to depress L. pneumophila intracellular growth. Uptake of L. pneumophila into a D. discoideum rtoA(-) strain was marginally defective, but this effect was not sufficient to account for the defective intracellular growth of L. pneumophila. The rtoA mutant was also more resistant to high-multiplicity killing by the bacterium. A targeting assay testing the colocalization of L. pneumophila-containing vacuole with an endoplasmic reticulum/pre-Golgi intermediate compartment marker protein, GFP-HDEL, was used to analyse these defects. In parental D. discoideum, the L. pneumophila vacuole showed recruitment of GFP-HDEL within 40 min after introduction of bacteria to the amoebae. By 6 h after infection it was clear that the rtoA mutant acquired and retained the GFP-HDEL less efficiently than the parental strain, and that the mutant was defective for promoting the physical expansion of the membranous compartment surrounding the bacteria. Depressed intracellular growth of L. pneumophila in a D. discoideum rtoA(-) mutant therefore appeared to result from a lowered efficiency of vesicle trafficking events that are essential for the modification and expansion of the L. pneumophila-containing compartment.
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Affiliation(s)
- Zhiru Li
- Howard Hughes Medical Institute, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
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27
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Derré I, Isberg RR. LidA, a translocated substrate of the Legionella pneumophila type IV secretion system, interferes with the early secretory pathway. Infect Immun 2005; 73:4370-80. [PMID: 15972532 PMCID: PMC1168608 DOI: 10.1128/iai.73.7.4370-4380.2005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Legionella pneumophila uses a type IV secretion system to deliver effector molecules into the host cell and establish its replication vacuole. In this study, we investigated the role of LidA, a translocated substrate associated with the surface of the L. pneumophila-containing vacuole. LidA is secreted into the host cell throughout the replication cycle of the bacteria and associates with compartments of the early secretory pathway. When overexpressed in mammalian cells or yeast, LidA interferes with the early secretory pathway, probably via a domain predicted to be rich in coiled-coil structure. Finally, during intracellular replication, the replication vacuoles are in close contact with the endoplasmic reticulum-Golgi intermediate compartment and the Golgi apparatus, suggesting a positive correlation between intracellular growth and association of the vacuole with compartments of the early secretory pathway. We propose that LidA is involved in the recruitment of early secretory vesicles to the L. pneumophila-containing vacuole and that the vacuole associates with the secretory pathway to facilitate this process.
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Affiliation(s)
- Isabelle Derré
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, Massachusetts 02111, USA
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28
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Abstract
After ingestion by macrophages, Legionella pneumophila enter spacious vacuoles that are quickly enveloped by endoplasmic reticulum (ER), then slowly transferred to lysosomes. Here we demonstrate that the macrophage autophagy machinery recognizes the pathogen phagosome as cargo for lysosome delivery. The autophagy conjugation enzyme Atg7 immediately translocated to phagosomes harbouring virulent Legionella. Subsequently, Atg8, a second autophagy enzyme, and monodansyl-cadaverine (MDC), a dye that accumulates in acidic autophagosomes, decorated the pathogen vacuoles. The autophagy machinery responded to 10-30 kDa species released into culture supernatants by Type IV secretion-competent Legionella, as judged by the macrophages' processing of Atg8 and formation of vacuoles that sequentially acquired Atg7, Atg8 and MDC. When compared with autophagosomes stimulated by rapamycin, Legionella vacuoles acquired Atg7, Atg8 and MDC more slowly, and Atg8 processing was also delayed. Moreover, compared with autophagosomes of Legionella-permissive naip5 mutant A/J macrophages, those of resistant C57BL/6 J macrophages matured quickly, preventing efficient Legionella replication. Accordingly, we discuss a model in which macrophages elevate autophagy as a barrier to infection, a decision influenced by regulatory interactions between Naip proteins and caspases.
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Affiliation(s)
| | - Michele S. Swanson
- Department of Microbiology and Immunology, University of Michigan Medical School, 6734 Medical Science Building II, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0620, USA
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29
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Bellaire BH, Roop RM, Cardelli JA. Opsonized virulent Brucella abortus replicates within nonacidic, endoplasmic reticulum-negative, LAMP-1-positive phagosomes in human monocytes. Infect Immun 2005; 73:3702-13. [PMID: 15908400 PMCID: PMC1111828 DOI: 10.1128/iai.73.6.3702-3713.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Revised: 11/16/2004] [Accepted: 02/15/2005] [Indexed: 11/20/2022] Open
Abstract
Cells in the Brucella spp. are intracellular pathogens that survive and replicate within host monocytes. Brucella maintains persistent infections in animals despite the production of high levels of anti-Brucella-specific antibodies. To determine the effect of antibody opsonization on the ability of Brucella to establish itself within monocytes, the intracellular trafficking of virulent Brucella abortus 2308 and attenuated hfq and bacA mutants was followed in the human monocytic cell line THP-1. Early trafficking events of B. abortus 2308-containing phagosomes (BCP) were indistinguishable from those seen for control particles (heat-killed B. abortus 2308, live Escherichia coli HB101, or latex beads). All phagosomes transiently communicated the early-endosomal compartment and rapidly matured into LAMP-1(+), cathepsin D(+), and acidic phagosomes. By 2 h postinfection, however, the number of cathepsin D(+) BCP was significantly lower for live B. abortus 2308-infected cells than for either Brucella mutant strains or control particles. B. abortus 2308 persisted within these cathepsin D(-), LAMP-1(+), and acidic vesicles; however, at the onset of intracellular replication, the numbers of acidic B. abortus 2308 BCP decreased while remaining cathepsin D(-) and LAMP-1(+). In contrast to B. abortus 2308, the isogenic hfq and bacA mutants remained in acidic, LAMP-1(+) phagosomes and failed to initiate intracellular replication. Notably, markers specific for the host endoplasmic reticulum were absent from the BCPs throughout the course of the infection. Thus, opsonized B. abortus in human monocytes survives within phagosomes that remain in the endosomal pathway and replication of virulent B. abortus 2308 within these vesicles corresponds with an increase in intraphagosomal pH.
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Affiliation(s)
- Bryan H Bellaire
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA.
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Arellano-Reynoso B, Lapaque N, Salcedo S, Briones G, Ciocchini AE, Ugalde R, Moreno E, Moriyón I, Gorvel JP. Cyclic beta-1,2-glucan is a Brucella virulence factor required for intracellular survival. Nat Immunol 2005; 6:618-25. [PMID: 15880113 DOI: 10.1038/ni1202] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Accepted: 03/28/2005] [Indexed: 11/08/2022]
Abstract
Pathogenic brucella bacteria have developed strategies to persist for prolonged periods of time in host cells, avoiding innate immune responses. Here we show that the cyclic beta-1,2-glucans (CbetaG) synthesized by brucella is important for circumventing host cell defenses. CbetaG acted in lipid rafts found on host cell membranes. CbetaG-deficient mutants failed to prevent phagosome-lysosome fusion and could not replicate. However, when treated with purified CbetaG or synthetic methyl-beta-cyclodextrin, the mutants were able to control vacuole maturation by avoiding lysosome fusion, and this allowed intracellular brucella to survive and reach the endoplasmic reticulum. Fusion between the endoplasmic reticulum and the brucella-containing vacuole depended on the brucella virulence type IV secretion system but not on CbetaG. Brucella CbetaG is thus a virulence factor that interacts with lipid rafts and contributes to pathogen survival.
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Affiliation(s)
- Beatriz Arellano-Reynoso
- Centre d'Immunologie, Institut National de la Santé et de la Recherche Médicale-Centre National de la Recherche Scientifique de Marseille-Luminy, Case 906, 13288 Marseille CEDEX 9, France
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31
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Abstract
The natural hosts of the bacterial pathogen Legionella pneumophila are amoebae and protozoa. In these hosts, as in human macrophages, the pathogen enters the cell through phagocytosis, then rapidly modifies the phagosome to create a compartment that supports its replication. We have examined L. pneumophila entry and behaviour during early stages of the infection of Dictyostelium discoideum amoebae. Bacteria were labelled with a red fluorescent marker, and selected proteins and organelles in the host were labelled with GFP, allowing the dynamics and interactions of L. pneumophila -containing phagosomes to be tracked in living cells. These studies demonstrated that entry of L. pneumophila is an actin-mediated process, that the actin-binding protein coronin surrounds the nascent phagosome but dissociates immediately after internalization, that ER membrane is not incorporated into a phagosome during uptake, that the newly internalized phagosome is rapidly transported about the cell on microtubules, that association of ER markers with the phagosome occurs in two steps that correlate with distinct changes in phagosome movement, and that the vacuolar H(+)-ATPase does not associate with mature replication vacuoles. These studies have clarified certain aspects of the infection process and provided new insights into the dynamic interactions between the pathogen and its host.
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Affiliation(s)
- Hao Lu
- Program in Molecular, Cell, and Developmental Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73121, USA
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Neumeister B, Faigle M, Spitznagel D, Mainka A, Ograbek A, Wieland H, Mannowetz N, Rammensee HG. Legionella pneumophila down-regulates MHC class I expression of human monocytic host cells and thereby inhibits T cell activation. Cell Mol Life Sci 2005; 62:578-88. [PMID: 15747062 DOI: 10.1007/s00018-005-4518-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Legionella (L.) pneumophila, the causative agent of Legionnaires' disease, is an intracellular pathogen of alveolar macrophages that resides in a compartment displaying features of endoplasmatic reticulum (ER). In this study, we show that intracellular multiplication of L. pneumophila results in a remarkable decrease in MHC class I expression by the infected monocytes. During intracellular multiplication, L. pneumophila absorbs ER-resident chaperons such as calnexin and BiP, molecules that are required for the correct formation of the MHC class I complex. Due to reduced MHC class I expression, stimulation of allogeneic blood mononuclear cells was severely inhibited by infected host cells but cytotoxicity of autologous natural killer cells against Legionella-infected monocytes was not enhanced. Thus, reduced expression of MHC class I in infected monocytes may resemble a new immune escape mechanism induced by L. pneumophila.
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Affiliation(s)
- B Neumeister
- Abteilung Transfusionsmedizin, AG Infektionsbiologie, Universitätsklinikum Tübingen, 72076, Tübingen, Germany.
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Voronin DA, Dudkina NV, Kiseleva EV. A new form of symbiotic bacteria Wolbachia found in the endoplasmic reticulum of early embryos of Drosophila melanogaster. Dokl Biol Sci 2005; 396:227-9. [PMID: 15354833 DOI: 10.1023/b:dobs.0000033284.76770.c1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- D A Voronin
- Institute of Cytology and Genetics, Siberian Division, Russian Academy of Sciences, pr: Akademika Lavrent'eva 10, Novosibirsk, 630090 Russia
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34
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Abstract
Legionella pneumophila vacuole biogenesis was analyzed by using a cell-free system. We show that calnexin, Sec22b, and Rab1 are recruited to the vacuole very shortly after bacterial uptake, and we have identified Rab1 as a potential host factor involved in the endoplasmic reticulum recruitment process.
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Affiliation(s)
- Isabelle Derré
- Department of Molecular Biology and Microbiology, Howard Hughes Medical Institute, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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35
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Arellano-Reynoso B, Díaz-Aparicio E, Leal-Hernández M, Hernández L, Gorvel JP. Intracellular trafficking study of a RB51 B. abortus vaccinal strain isolated from cow milk. Vet Microbiol 2004; 98:307-12. [PMID: 15036539 DOI: 10.1016/j.vetmic.2003.10.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2003] [Revised: 10/07/2003] [Accepted: 10/29/2003] [Indexed: 10/26/2022]
Abstract
Brucella is responsible for one of the major worldwide zoonoses. Over the last century, several vaccines have been used against brucellosis. Among these, the rough vaccine Brucella abortus RB51 was introduced with the idea that it would not interfere with the diagnosis of brucellosis. Recently, RB51 has been isolated from milk and vaginal exudates from vaccinated cows, thus raising the possibility of extensive bacterial replication in these animals. We hypothesized that shedding of RB51 might be related to a change in its intracellular cell cycle. Therefore, we have compared the intracellular trafficking in CHO cells of the virulent B. abortus 2308 and two RB51 strains, the vaccinal strain and the one isolated from cow milk. Both RB51 strains were transiently observed in phagosomes characterized by the presence of the early endosomal marker EEA1 and then were found in cathepsin D-enriched lysosomal compartments, in which they eventually underwent degradation at later post-infection times. In contrast, the virulent 2308 strain replicated within the endoplasmic reticulum. These results suggest that a change in intracellular trafficking cannot account for Brucella shedding in adult vaccinated cows.
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Otto GP, Wu MY, Clarke M, Lu H, Anderson OR, Hilbi H, Shuman HA, Kessin RH. Macroautophagy is dispensable for intracellular replication of Legionella pneumophila in Dictyostelium discoideum. Mol Microbiol 2004; 51:63-72. [PMID: 14651611 DOI: 10.1046/j.1365-2958.2003.03826.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The Gram-negative bacterium Legionella pneumophila is a facultative intracellular pathogen of free-living amoebae and mammalian phagocytes. L. pneumophila is engulfed in phagosomes that initially avoid fusion with lysosomes. The phagosome associates with endoplasmic reticulum (ER) and mitochondria and eventually resembles ER. The morphological similarity of the replication vacuole to autophagosomes, and enhanced bacterial replication in response to macroautophagy-inducing starvation, led to the hypothesis that L. pneumophila infection requires macroautophagy. As L. pneumophila replicates in Dictyostelium discoideum, and macroautophagy genes have been identified and mutated in D. discoideum, we have taken a genetic and cell biological approach to evaluate the relationship between host macroautophagy and intracellular replication of L. pneumophila. Mutation of the apg1, apg5, apg6, apg7 and apg8 genes produced typical macroautophagy defects, including reduced bulk protein degradation and cell viability during starvation. We show that L. pneumophila replicates normally in D. discoideum macroautophagy mutants and produces replication vacuoles that are morphologically indistinguishable from those in wild-type D. discoideum. Furthermore, a green fluorescent protein (GFP)-tagged marker of autophagosomes, Apg8, does not systematically co-localize with DsRed-labelled L. pneumophila. We conclude that macroautophagy is dispensable for L. pneumophila intracellular replication in D. discoideum.
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Affiliation(s)
- Grant P Otto
- Department of Anatomy and Cell Biology, Columbia University, 630 West 168th St., New York, NY 10032, USA
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Abstract
Brucella is an intracellular pathogen that survives and multiplies inside host macrophages to cause brucellosis. The underlying mechanisms of intracellular survival, including the bacterial and the host determinants remain relatively unknown. Recent advances have helped to decipher how Brucella controls the biogenesis of its intramacrophagic replicative organelle. Brucella initially avoids or escapes the endocytic pathway to ensure its intracellular survival, which is then further secured via the biogenesis of an endoplasmic reticulum-derived replicative organelle. A major virulence factor, the VirB type IV secretion system, is required for sustained interactions and fusion with the host endoplasmic reticulum.
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Affiliation(s)
- Jean Celli
- Centre d'Immunologie INSERM-CNRS-Université de la Méditerranée de Marseille-Luminy, Parc scientifique et technologique de Luminy, case 906, 13288 Marseille cedex 09, France
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38
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Kagan JC, Roy CR. Legionella phagosomes intercept vesicular traffic from endoplasmic reticulum exit sites. Nat Cell Biol 2002; 4:945-54. [PMID: 12447391 DOI: 10.1038/ncb883] [Citation(s) in RCA: 371] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2002] [Revised: 08/29/2002] [Accepted: 10/24/2002] [Indexed: 11/09/2022]
Abstract
It is unknown how Legionella pneumophila cells escape the degradative lysosomal pathway after phagocytosis by macrophages and replicate in an organelle derived from the endoplasmic reticulum. Here we show that, after internalization, L. pneumophila-containing phagosomes recruit early secretory vesicles. Once L. pneumophila phagosomes have intercepted early secretory vesicles they begin to acquire proteins residing in transitional and rough endoplasmic reticulum. The functions of Sar1 and ADP-ribosylation factor-1 are important for biogenesis of the L. pneumophila replicative organelle. These data indicate that L. pneumophila intercepts vesicular traffic from endoplasmic-reticulum exit sites to create an organelle that permits intracellular replication and prevents destruction by the host cell.
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Affiliation(s)
- Jonathan C Kagan
- Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06536-0812, USA
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39
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Abstract
The endoplasmic reticulum (ER) has unique properties that are exploited by microbial pathogens. Exotoxins secreted by bacteria take advantage of the host transport pathways that deliver proteins from the Golgi to the ER. Transport to the ER is necessary for the unfolding and translocation of these toxins into the cytosol where their host targets reside. Intracellular pathogens subvert host vesicle transport to create ER-like vacuoles that support their intracellular replication. Investigations on how bacterial pathogens can use the ER during host infection are providing important details on transport pathways involving this specialized organelle.
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Affiliation(s)
- Craig R Roy
- Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06511, USA.
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40
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Lencer WI. Microbes and microbial Toxins: paradigms for microbial-mucosal toxins. V. Cholera: invasion of the intestinal epithelial barrier by a stably folded protein toxin. Am J Physiol Gastrointest Liver Physiol 2001; 280:G781-6. [PMID: 11292584 DOI: 10.1152/ajpgi.2001.280.5.g781] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholera toxin (CT) produced by Vibrio cholerae is the virulence factor responsible for the massive secretory diarrhea seen in Asiatic cholera. To cause disease, CT enters the intestinal epithelial cell as a stably folded protein by co-opting a lipid-based membrane receptor, ganglioside G(M1). G(M1) sorts the toxin into lipid rafts and a retrograde trafficking pathway to the endoplasmic reticulum, where the toxin unfolds and transfers its enzymatic subunit to the cytosol, probably by dislocation through the translocon sec61p. The molecular determinants that drive entry of CT into this pathway are encoded entirely within the structure of the protein toxin itself.
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Affiliation(s)
- W I Lencer
- Combined Program in Pediatric Gastroenterology and Nutrition, GI Cell Biology, Enders 1220, Children's Hospital, 300 Longwood Ave., Boston, MA 02115, USA.
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41
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Gerhardt H, Walz MJ, Faigle M, Northoff H, Wolburg H, Neumeister B. Localization of Legionella bacteria within ribosome-studded phagosomes is not restricted to Legionella pneumophila. FEMS Microbiol Lett 2000; 192:145-52. [PMID: 11040443 DOI: 10.1111/j.1574-6968.2000.tb09373.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In this report, we investigate the intracellular fate of selected members of the genus Legionella within the monocytic cell line Mono Mac 6 cells. By means of electron microscopy and immunocytochemistry, we could show that Legionella pneumophila as well as Legionella longbeachae are able to induce ribosome-studded phagosomes which associate with the rough endoplasmic reticulum (RER), whereas Legionella micdadei remains to be located within smooth phagosomes but also shows signs of RER association. In addition, we could demonstrate a remarkable correlation between the phagosome type and the morphological phenotype of intracellular bacteria: within ribosome-studded phagosomes, bacteria generally lacked the outer coat of low electron density whereas bacteria within the smooth phagosomes still possessed this outer coat. The virulence factors responsible for inhibition of phagosome maturation and their distribution within the genus Legionella as well as the biological significance of the morphological difference of bacteria within smooth and ER-associated phagosomes remain to be investigated.
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Affiliation(s)
- H Gerhardt
- Pathologisches Institut der Universität Tübingen, Tübingen, Germany
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42
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Rajan S, Cacalano G, Bryan R, Ratner AJ, Sontich CU, van Heerckeren A, Davis P, Prince A. Pseudomonas aeruginosa induction of apoptosis in respiratory epithelial cells: analysis of the effects of cystic fibrosis transmembrane conductance regulator dysfunction and bacterial virulence factors. Am J Respir Cell Mol Biol 2000; 23:304-12. [PMID: 10970820 DOI: 10.1165/ajrcmb.23.3.4098] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Airway epithelial cells can respond to infection by activating several signaling pathways. We examined the induction of apoptosis in response to Pseudomonas aeruginosa PAO1 in normal cells and several cystic fibrosis (CF) and corrected cell lines. Epithelial cells in monolayers with tight junctions, confirmed by apical ZO-1 staining demonstrated by confocal microscopy, were entirely resistant to PAO1-induced apoptosis. In contrast, cell lines such as 9HTEo(-) cells that do not form tight junctions were susceptible, with 50% of the population apoptotic after 6 h of exposure to PAO1. CF transmembrane conductance regulator (CFTR) dysfunction caused by different mechanisms (trafficking mutations, overexpression of the regulatory domain or antisense constructs) did not alter rates of apoptosis, nor were differences apparent in terminal deoxyribonucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling detection of apoptotic airway cells from PAO1 infected cftr -/- or control mice. Bacterial expression of specific adhesins, complete lipopolysaccharide, and a functional type III secretion system were all necessary to evoke apoptosis even in susceptible epithelial cells. Unlike other mucosal surfaces, the airway epithelium is highly resistant to apoptosis, and this response is activated only when the appropriate epithelial conditions are present as well as fully virulent P. aeruginosa capable of coordinately expressing both adhesins and cytotoxins.
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Affiliation(s)
- S Rajan
- Department of Pediatric Infectious Diseases, College of Physicians & Surgeons, Columbia University, New York, New York, USA
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43
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Abstract
Brucella abortus is a facultative intracellular parasite that promotes its own internalization in nonphagocytic cells. The bacterium initially interacts with compartments of the early endocytic cascade, then rapidly segregates from this intracellular pathway and associates with the autophagocytic cascade. During the late stages of infection, Brucella proliferates within the endoplasmic reticulum of host cells.
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Affiliation(s)
- J Pizarro-Cerdá
- Département de bactériologie, Institut Pasteur, Paris, France
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44
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Pizarro-Cerdá J, Méresse S, Parton RG, van der Goot G, Sola-Landa A, Lopez-Goñi I, Moreno E, Gorvel JP. Brucella abortus transits through the autophagic pathway and replicates in the endoplasmic reticulum of nonprofessional phagocytes. Infect Immun 1998; 66:5711-24. [PMID: 9826346 PMCID: PMC108722 DOI: 10.1128/iai.66.12.5711-5724.1998] [Citation(s) in RCA: 334] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/1998] [Accepted: 09/01/1998] [Indexed: 11/20/2022] Open
Abstract
Brucella abortus is an intracellular pathogen that replicates within a membrane-bounded compartment. In this study, we have examined the intracellular pathway of the virulent B. abortus strain 2308 (S2308) and the attenuated strain 19 (S19) in HeLa cells. At 10 min after inoculation, both bacterial strains are transiently detected in phagosomes characterized by the presence of early endosomal markers such as the early endosomal antigen 1. At approximately 1 h postinoculation, bacteria are located within a compartment positive for the lysosome-associated membrane proteins (LAMPs) and the endoplasmic reticulum (ER) marker sec61beta but negative for the mannose 6-phosphate receptors and cathepsin D. Interestingly, this compartment is also positive for the autophagosomal marker monodansylcadaverin, suggesting that S2308 and S19 are located in autophagic vacuoles. At 24 h after inoculation, attenuated S19 is degraded in lysosomes, while virulent S2308 multiplies within a LAMP- and cathepsin D-negative but sec61beta- and protein disulfide isomerase-positive compartment. Furthermore, treatment of infected cells with the pore-forming toxin aerolysin from Aeromonas hydrophila causes vacuolation of the bacterial replication compartment. These results are compatible with the hypothesis that pathogenic B. abortus exploits the autophagic machinery of HeLa cells to establish an intracellular niche favorable for its replication within the ER.
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Affiliation(s)
- J Pizarro-Cerdá
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, Marseille, France
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45
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Abstract
L. pneumophila is a model organism for investigating the mechanisms by which intracellular pathogens acquire the metabolites needed for replication while evading the microbicidal mechanisms of the macrophage. We determined that intracellular L. pneumophila replicate in close association with the endoplasmic reticulum and suggest that L. pneumophila exploits the macrophage autophagy pathway to establish this specialized vacuole. To identify the bacterial factors required at this step as well as the factors important for other stages of the intracellular pathway, we isolated a collection of bacterial mutants that are defective for growth in macrophages. The ability of the mutant strains to evade fusion with the lysosomes and to establish replication vacuoles was examined by fluorescence microscopic localization of markers for the late endosomes (lgp 120), lysosomes (Texas Red-ovalbumin), endoplasmic reticulum (BiP), and L. pneumophila. By this approach, we identified mutants with distinct intracellular fates; one type does not evade the endocytic pathway, another forms replication vacuoles less efficiently than does wild-type, and a third type forms replication vacuoles but replicates poorly. These mutants are likely to facilitate identification and characterization of the bacterial factors required by L. pneumophila to establish a protected niche for intracellular replication.
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Affiliation(s)
- M S Swanson
- Department of Molecular Biology and Microbiology, Tufts University-School of Medicine, Boston, Massachusetts 02111, USA
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46
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Abstract
After uptake by macrophages, Legionella pneumiophila evades phagosome-lysosome fusion and replicates in a compartment associated with the endoplasmic reticulum. A collection of bacterial mutants defective for growth in macrophages were isolated, and the intracellular fate of each mutant strain was analyzed by fluorescence microscopy. To measure intracellular replication, bacteria inside macrophages were stained with the DNA dye 4',6-diamidino-2-phenylindole (DAPI). Evasion of the endocytic pathway was quantified by immunofluorescence localization of lp120 [correction of IgpI20] (LAMP-1), a membrane protein of late endosomes and lysosomes, or by measuring colocalization of bacteria with a fluorescent tracer, Texas red-ovalbumin, preloaded into lysosomes. Replication vacuoles were quantified by immunofluorescence localization of BiP, an endoplasmic reticulum protein. By these approaches, four phenotypic groups of mutants were classified. One class formed replication vacuoles less efficiently than the wild type did; another formed replication vacuoles, but replication was abortive; in another class, most phagosomes containing bacteria acquired markers of the endocytic pathway but a minority formed replication vacuoles and the bacteria replicated; finally, a fourth class, the one most defective for intracellular growth, occupied vacuoles that acquired markers of the endocytic pathway.
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Affiliation(s)
- M S Swanson
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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47
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Abstract
Legionella pneumophila replicates within a membrane-bounded compartment that is studded with ribosomes. In this study we investigated whether these ribosomes originate from the cytoplasmic pool or are associated with host endoplasmic reticulum (ER). Immunofluorescence and electron microscopic localization studies of ER proteins in macrophages infected with L. pneumophila indicated that the bacteria reside in a compartment surrounded by ER. An L. pneumophila mutant that grows slowly in macrophages was slow to associate with host ER, providing genetic evidence in support of the hypothesis that this specialized vacuole is required for intracellular bacterial growth. Ultrastructural studies, in which the ER luminal protein BiP was labeled by immunoperoxidase cytochemistry, revealed that L. pneumophila replication vacuoles resemble nascent autophagosomes. Furthermore, short-term amino acid starvation of macrophages, which stimulated host autophagosomes. Furthermore, short-term amino acid starvation of macrophages, which stimulated host autophagy, increased association of the bacteria with the ER and enhanced bacterial growth. These results are compatible with the hypothesis that L. pneumophila exploits the autophagy machinery of macrophages to establish an intracellular niche favorable for replication.
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Affiliation(s)
- M S Swanson
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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48
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Svensson L, Dormitzer PR, von Bonsdorff CH, Maunula L, Greenberg HB. Intracellular manipulation of disulfide bond formation in rotavirus proteins during assembly. J Virol 1994; 68:5204-15. [PMID: 8035518 PMCID: PMC236464 DOI: 10.1128/jvi.68.8.5204-5215.1994] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Rotavirus undergoes a unique mode of assembly in the rough endoplasmic reticulum (RER) of infected cells. Luminal RER proteins undergo significant cotranslational and posttranslational modifications, including disulfide bond formation. Addition of a reducing agent (dithiothreitol [DTT]) to rotavirus-infected cells did not significantly inhibit translation or disrupt established disulfide bonds in rotavirus proteins but prevented the formation of new disulfide bonds and infectious viral progeny. In DTT-treated, rotavirus-infected cells, all vp4, vp6, and ns28 epitopes but no vp7 epitopes were detected by immunohistochemical staining with a panel of monoclonal antibodies. When oxidizing conditions were reestablished in DTT-treated cells, intramolecular disulfide bonds in vp7 were rapidly and correctly established with the restoration of antigenicity, although prolonged DTT treatment led to the accumulation of permanently misfolded vp7. Electron microscopy revealed that cytosolic assembly of single-shelled particles and budding into the ER was not affected by DTT treatment but that outer capsid assembly was blocked, leading to the accumulation of single-shelled and enveloped intermediate subviral particles in the RER lumen.
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Affiliation(s)
- L Svensson
- Division of Gastroenterology, Stanford University Medical Center, California 94305
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49
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Abstract
The biosynthesis and biochemical properties of the putative nucleocapsid protein of hepatitis C virus (HCV) were investigated. RNA transcripts for cell-free translation were prepared from truncated form of the cDNA construct encoding the structural proteins of HCV. Processing of the translation products was dependent on microsomal membranes and signal recognition particle, suggesting that release of the 21-kDa core protein from the polyprotein precursor is mediated solely by the signal peptidase of the endoplasmic reticulum (ER) and is achieved by the removal of a putative signal sequence of approximately 18 residues located at its C terminus. The core protein was found to bind membranes in vitro and in transfected cells, as shown by centrifugation analysis of in vitro translation products and transfected-cell lysates. Immunofluorescence of transfected cells showed that the core protein colocalized with the E2 glycoprotein as well as with a cellular ER membrane marker. The nucleocapsid protein expressed by in vitro translation in rabbit reticulocyte lysates cosedimented with the large ribosomal subunit in sucrose gradients. The ribosome binding domain was mapped to the N-terminal region of the core protein. Moreover, the same region was shown to bind RNA in vitro, suggesting that cosedimentation of core protein with ribosomes may be mediated by the RNA binding of the nucleocapsid protein of HCV. These studies indicate that the HCV core protein is a cytoplasmic protein associated with the ER membranes and possesses RNA binding activity.
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Affiliation(s)
- E Santolini
- Instituto di Ricerche di Biologia Molecolare, P. Angeletti Pomezia, Rome, Italy
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50
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Connelly MA, Grady RC, Mushinski JF, Marcu KB. PANG, a gene encoding a neuronal glycoprotein, is ectopically activated by intracisternal A-type particle long terminal repeats in murine plasmacytomas. Proc Natl Acad Sci U S A 1994; 91:1337-41. [PMID: 8108413 PMCID: PMC43153 DOI: 10.1073/pnas.91.4.1337] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Plasmacytomagenesis provides a murine model to decipher progressive genetic events culminating in a B-cell neoplasia. Activation of the c-myc protooncogene by chromosomal translocation is considered an initiating event. Intracisternal A-type particles (IAPs) are defective retroviral-like structures present in the endoplasmic reticulum of plasmacytomas (PCTs). IAP proviral insertions have been documented to engender negative or positive effects on the expression of nearby cellular genes. We have isolated a gene, PANG (plasmacytoma-associated neuronal glycoprotein), that is ectopically transcribed in a number of PCTs due to IAP long terminal repeat (LTR) activation. A full-length PANG cDNA was isolated from an MPC-11 plasma cell tumor cDNA library and encodes a polypeptide of about 113 kDa with six immunoglobulin C2-like and four type III fibronectin-like domains. PANG bears a striking resemblance to axonal glycoproteins TAG-1 and F11 known to function in neuronal outgrowth. An extensive survey revealed a predominant 3.6-kb PANG transcript in 60% (30 of 50) of PCTs as well as unique smaller and larger species. All other normal and transformed lymphoid and nonlymphoid cell lines and normal tissues were negative for PANG expression except for the brain, wherein unique 4.0- and 6.1-kb transcripts were detected. Reverse transcriptase PCR analysis revealed IAP LTR fusion to PANG mRNAs in five PCTs and in a neuroblastoma line. The 5' end of a mouse brain PANG cDNA was identical to the MPC-11 PANG transcript except for the precise replacement of its 5' LTR sequence.
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Affiliation(s)
- M A Connelly
- Department of Pathology, State University of New York, Stony Brook 11794-5215
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