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Ferrel A, Romano J, Panas MW, Coppens I, Boothroyd JC. Host MOSPD2 enrichment at the parasitophorous vacuole membrane varies between Toxoplasma strains and involves complex interactions. mSphere 2023; 8:e0067022. [PMID: 37341482 PMCID: PMC10449529 DOI: 10.1128/msphere.00670-22] [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: 12/22/2022] [Accepted: 04/25/2023] [Indexed: 06/22/2023] Open
Abstract
Toxoplasma gondii is an obligate, intracellular parasite. Infection of a cell produces a unique niche for the parasite named the parasitophorous vacuole (PV) initially composed of host plasma membrane invaginated during invasion. The PV and its membrane (parasitophorous vacuole membrane [PVM]) are subsequently decorated with a variety of parasite proteins allowing the parasite to optimally grow in addition to manipulate host processes. Recently, we reported a proximity-labeling screen at the PVM-host interface and identified host endoplasmic reticulum (ER)-resident motile sperm domain-containing protein 2 (MOSPD2) as being enriched at this location. Here we extend these findings in several important respects. First, we show that the extent and pattern of host MOSPD2 association with the PVM differ dramatically in cells infected with different strains of Toxoplasma. Second, in cells infected with Type I RH strain, the MOSPD2 staining is mutually exclusive with regions of the PVM that associate with mitochondria. Third, immunoprecipitation and liquid chromatography tandem mass spectrometry (LC-MS/MS) with epitope-tagged MOSPD2-expressing host cells reveal strong enrichment of several PVM-localized parasite proteins, although none appear to play an essential role in MOSPD2 association. Fourth, most MOSPD2 associating with the PVM is newly translated after infection of the cell and requires the major functional domains of MOSPD2, identified as the CRAL/TRIO domain and tail anchor, although these domains were not sufficient for PVM association. Lastly, ablation of MOSPD2 results in, at most, a modest impact on Toxoplasma growth in vitro. Collectively, these studies provide new insight into the molecular interactions involving MOSPD2 at the dynamic interface between the PVM and the host cytosol. IMPORTANCE Toxoplasma gondii is an intracellular pathogen that lives within a membranous vacuole inside of its host cell. This vacuole is decorated by a variety of parasite proteins that allow it to defend against host attack, acquire nutrients, and interact with the host cell. Recent work identified and validated host proteins enriched at this host-pathogen interface. Here, we follow up on one candidate named MOSPD2 shown to be enriched at the vacuolar membrane and describe it as having a dynamic interaction at this location depending on a variety of factors. Some of these include the presence of host mitochondria, intrinsic domains of the host protein, and whether translation is active. Importantly, we show that MOSPD2 enrichment at the vacuole membrane differs between strains indicating active involvement of the parasite with this phenotype. Altogether, these results shed light on the mechanism and role of protein associations in the host-pathogen interaction.
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Affiliation(s)
- Abel Ferrel
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Julia Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Michael W. Panas
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - John C. Boothroyd
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
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Panas MW, Boothroyd JC. Seizing control: How dense granule effector proteins enable Toxoplasma to take charge. Mol Microbiol 2021; 115:466-477. [PMID: 33400323 PMCID: PMC8344355 DOI: 10.1111/mmi.14679] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [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: 11/16/2020] [Revised: 01/02/2021] [Accepted: 01/03/2021] [Indexed: 12/24/2022]
Abstract
Control of the host cell is crucial to the Apicomplexan parasite, Toxoplasma gondii, while it grows intracellularly. To achieve this goal, these single-celled eukaryotes export a series of effector proteins from organelles known as "dense granules" that interfere with normal cellular processes and responses to invasion. While some effectors are found attached to the outer surface of the parasitophorous vacuole (PV) in which Toxoplasma tachyzoites reside, others are found in the host cell's cytoplasm and yet others make their way into the host nucleus, where they alter host transcription. Among the processes that are severely altered are innate immune responses, host cell cycle, and association with host organelles. The ways in which these crucial processes are altered through the coordinated action of a large collection of effectors is as elegant as it is complex, and is the central focus of the following review; we also discuss the recent advances in our understanding of how dense granule effector proteins are trafficked out of the PV.
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Affiliation(s)
- Michael W. Panas
- Dept. Microbiology and Immunology, Stanford University School of Medicine, Stanford CA 94305
| | - John C. Boothroyd
- Dept. Microbiology and Immunology, Stanford University School of Medicine, Stanford CA 94305
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3
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Abstract
Manipulation of the host cell is a crucial part of life for many intracellular organisms. We have recently come to appreciate the extent to which the intracellular pathogen Toxoplasma gondii reprograms its host cell, and this is illustrated by the marked upregulation of the central regulator c-Myc, an oncogene that coordinates myriad cellular functions. In an effort to identify an effector protein capable of regulating c-Myc, our laboratory constructed a screen for mutant parasites unable to accomplish this upregulation. Interestingly, this screen identified numerous components of a complex located in/on the parasitophorous vacuole membrane necessary to translocate Toxoplasma proteins out into the host cytosol, but it never identified a specific effector protein. Thus, how the parasite upregulates c-Myc has largely been a mystery. Previously, the Toxoplasma dense granule protein GRA16 has been described to bind to one isoform of PP2A-B, a regulatory subunit that coordinates the activity of the catalytic protein phosphatase PP2A. As other PP2A subunits have been reported to target PP2A protein phosphatase activity to c-Myc, subsequently leading to c-Myc destabilization, we examined whether GRA16 has an impact on host c-Myc accumulation. Expression of Toxoplasma's GRA16 protein in Neospora caninum, a close relative of Toxoplasma that does not naturally upregulate host c-Myc, conferred the ability on Neospora to do this now. Further support was obtained by deleting the GRA16 gene from Toxoplasma and observing a severely diminished ability of Toxoplasma tachyzoites to upregulate host c-Myc. Thus, GRA16 is an effector protein central to Toxoplasma's ability to upregulate host c-Myc.IMPORTANCE The proto-oncogene c-Myc plays a crucial role in the growth and division of many animal cells. Previous studies have identified an active upregulation of c-Myc by Toxoplasma tachyzoites, suggesting the existence of one or more exported "effector" proteins. The identity of such an effector, however, has not previously been known. Here, we show that a previously known secreted protein, GRA16, plays a crucial role in c-Myc upregulation. This finding will enable further dissection of the precise mechanism and role of c-Myc upregulation in Toxoplasma-infected cells.
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Affiliation(s)
- Michael W Panas
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
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Cygan AM, Theisen TC, Mendoza AG, Marino ND, Panas MW, Boothroyd JC. Coimmunoprecipitation with MYR1 Identifies Three Additional Proteins within the Toxoplasma gondii Parasitophorous Vacuole Required for Translocation of Dense Granule Effectors into Host Cells. mSphere 2020; 5:e00858-19. [PMID: 32075880 PMCID: PMC7031616 DOI: 10.1128/msphere.00858-19] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [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: 11/25/2019] [Accepted: 01/24/2020] [Indexed: 11/20/2022] Open
Abstract
Toxoplasma gondii is a ubiquitous, intracellular protozoan that extensively modifies infected host cells through secreted effector proteins. Many such effectors must be translocated across the parasitophorous vacuole (PV), in which the parasites replicate, ultimately ending up in the host cytosol or nucleus. This translocation has previously been shown to be dependent on five parasite proteins: MYR1, MYR2, MYR3, ROP17, and ASP5. We report here the identification of several MYR1-interacting and novel PV-localized proteins via affinity purification of MYR1, including TGGT1_211460 (dubbed MYR4), TGGT1_204340 (dubbed GRA54), and TGGT1_270320 (PPM3C). Further, we show that three of the MYR1-interacting proteins, GRA44, GRA45, and MYR4, are essential for the translocation of the Toxoplasma effector protein GRA16 and for the upregulation of human c-Myc and cyclin E1 in infected cells. GRA44 and GRA45 contain ASP5 processing motifs, but like MYR1, processing at these sites appears to be nonessential for their role in protein translocation. These results expand our understanding of the mechanism of effector translocation in Toxoplasma and indicate that the process is highly complex and dependent on at least eight discrete proteins.IMPORTANCEToxoplasma is an extremely successful intracellular parasite and important human pathogen. Upon infection of a new cell, Toxoplasma establishes a replicative vacuole and translocates parasite effectors across this vacuole to function from the host cytosol and nucleus. These effectors play a key role in parasite virulence. The work reported here newly identifies three parasite proteins that are necessary for protein translocation into the host cell. These results significantly increase our knowledge of the molecular players involved in protein translocation in Toxoplasma-infected cells and provide additional potential drug targets.
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Affiliation(s)
- Alicja M Cygan
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Terence C Theisen
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Alma G Mendoza
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Nicole D Marino
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Michael W Panas
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
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Panas MW, Ferrel A, Naor A, Tenborg E, Lorenzi HA, Boothroyd JC. Translocation of Dense Granule Effectors across the Parasitophorous Vacuole Membrane in Toxoplasma-Infected Cells Requires the Activity of ROP17, a Rhoptry Protein Kinase. mSphere 2019; 4:e00276-19. [PMID: 31366709 PMCID: PMC6669336 DOI: 10.1128/msphere.00276-19] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [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: 04/17/2019] [Accepted: 07/02/2019] [Indexed: 11/20/2022] Open
Abstract
Toxoplasma gondii tachyzoites co-opt host cell functions through introduction of a large set of rhoptry- and dense granule-derived effector proteins. These effectors reach the host cytosol through different means: direct injection for rhoptry effectors and translocation across the parasitophorous vacuolar membrane (PVM) for dense granule (GRA) effectors. The machinery that translocates these GRA effectors has recently been partially elucidated, revealing three components, MYR1, MYR2, and MYR3. To determine whether other proteins might be involved, we returned to a library of mutants defective in GRA translocation and selected one with a partial defect, suggesting it might be in a gene encoding a new component of the machinery. Surprisingly, whole-genome sequencing revealed a missense mutation in a gene encoding a known rhoptry protein, a serine/threonine protein kinase known as ROP17. ROP17 resides on the host cytosol side of the PVM in infected cells and has previously been known for its activity in phosphorylating and thereby inactivating host immunity-related GTPases. Here, we show that null or catalytically dead mutants of ROP17 are defective in GRA translocation across the PVM but that translocation can be rescued "in trans" by ROP17 delivered by other tachyzoites infecting the same host cell. This strongly argues that ROP17's role in regulating GRA translocation is carried out on the host cytosolic side of the PVM, not within the parasites or lumen of the parasitophorous vacuole. This represents an entirely new way in which the different secretory compartments of Toxoplasma tachyzoites collaborate to modulate the host-parasite interaction.IMPORTANCE When Toxoplasma infects a cell, it establishes a protective parasitophorous vacuole surrounding it. While this vacuole provides protection, it also serves as a barrier to the export of parasite effector proteins that impact and take control of the host cell. Our discovery here that the parasite rhoptry protein ROP17 is necessary for export of these effector proteins provides a distinct, novel function for ROP17 apart from its known role in protecting the vacuole. This will enable future research into ways in which we can prevent the export of effector proteins, thereby preventing Toxoplasma from productively infecting its animal and human hosts.
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Affiliation(s)
- Michael W Panas
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Abel Ferrel
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Adit Naor
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Elizabeth Tenborg
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
- University of California at Davis, School of Veterinary Medicine, Davis, California, USA
| | - Hernan A Lorenzi
- Department of Infectious Diseases, J. Craig Venter Institute, Rockville, Maryland, USA
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
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Panas MW, Naor A, Cygan AM, Boothroyd JC. Toxoplasma Controls Host Cyclin E Expression through the Use of a Novel MYR1-Dependent Effector Protein, HCE1. mBio 2019; 10:e00674-19. [PMID: 31040242 PMCID: PMC6495377 DOI: 10.1128/mbio.00674-19] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [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: 03/15/2019] [Accepted: 03/25/2019] [Indexed: 01/27/2023] Open
Abstract
Toxoplasma gondii is an obligate intracellular parasite that establishes a favorable environment in the host cells in which it replicates. We have previously reported that it uses MYR-dependent translocation of dense granule proteins to elicit a key set of host responses related to the cell cycle, specifically, E2F transcription factor targets, including cyclin E. We report here the identification of a novel Toxoplasma effector protein that is exported from the parasitophorous vacuole in a MYR1-dependent manner and localizes to the host's nucleus. Parasites lacking this inducer of host cyclin E (HCE1) are unable to modulate E2F transcription factor target genes and exhibit a substantial growth defect. Immunoprecipitation of HCE1 from infected host cells showed that HCE1 efficiently binds elements of the cyclin E regulatory complex, namely, DP1 and its partners E2F3 and E2F4. Expression of HCE1 in Neospora caninum, or in uninfected human foreskin fibroblasts (HFFs), showed localization of the expressed protein to the host nuclei and strong cyclin E upregulation. Thus, HCE1 is a novel effector protein that is necessary and sufficient to impact the E2F axis of transcription, resulting in co-opting of host functions to the advantage of ToxoplasmaIMPORTANCE Like most Apicomplexan parasites, Toxoplasma gondii has the remarkable ability to invade and establish a replicative niche within another eukaryotic cell, in this case, any of a large number of cell types in almost any warm-blooded animals. Part of the process of establishing this niche is the export of effector proteins to co-opt host cell functions in favor of the parasite. Here we identify a novel effector protein, HCE1, that the parasites export into the nucleus of human cells, where it modulates the expression of multiple genes, including the gene encoding cyclin E, one of the most crucial proteins involved in controlling when and whether a human cell divides. We show that HCE1 works through binding to specific transcription factors, namely, E2F3, E2F4, and DP1, that normally carefully regulate these all-important pathways. This represents a new way in which these consummately efficient infectious agents co-opt the human cells that they so efficiently grow within.
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Affiliation(s)
- Michael W Panas
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Adit Naor
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Alicja M Cygan
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
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Naor A, Panas MW, Marino N, Coffey MJ, Tonkin CJ, Boothroyd JC. MYR1-Dependent Effectors Are the Major Drivers of a Host Cell's Early Response to Toxoplasma, Including Counteracting MYR1-Independent Effects. mBio 2018; 9:e02401-17. [PMID: 29615509 PMCID: PMC5885026 DOI: 10.1128/mbio.02401-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [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: 01/03/2018] [Accepted: 03/07/2018] [Indexed: 01/08/2023] Open
Abstract
The obligate intracellular parasite Toxoplasma gondii controls its host cell from within the parasitophorous vacuole (PV) by using a number of diverse effector proteins, a subset of which require the aspartyl protease 5 enzyme (ASP5) and/or the recently discovered MYR1 protein to cross the PV membrane. To examine the impact these effectors have in the context of the entirety of the host response to Toxoplasma, we used RNA-Seq to analyze the transcriptome expression profiles of human foreskin fibroblasts infected with wild-type RH (RH-WT), RHΔmyr1, and RHΔasp5 tachyzoites. Interestingly, the majority of the differentially regulated genes responding to Toxoplasma infection are MYR1 dependent. A subset of MYR1 responses were ASP5 independent, and MYR1 function did not require ASP5 cleavage, suggesting the export of some effectors requires only MYR1. Gene set enrichment analysis of MYR1-dependent host responses suggests an upregulation of E2F transcription factors and the cell cycle and a downregulation related to interferon signaling, among numerous others. Most surprisingly, "hidden" responses arising in RHΔmyr1- but not RH-WT-infected host cells indicate counterbalancing actions of MYR1-dependent and -independent activities. The host genes and gene sets revealed here to be MYR1 dependent provide new insight into the parasite's ability to co-opt host cell functions.IMPORTANCEToxoplasma gondii is unique in its ability to successfully invade and replicate in a broad range of host species and cells within those hosts. The complex interplay of effector proteins exported by Toxoplasma is key to its success in co-opting the host cell to create a favorable replicative niche. Here we show that a majority of the transcriptomic effects in tachyzoite-infected cells depend on the activity of a novel translocation system involving MYR1 and that the effectors delivered by this system are part of an intricate interplay of activators and suppressors. Removal of all MYR1-dependent effectors reveals previously unknown activities that are masked or hidden by the action of these proteins.
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Affiliation(s)
- Adit Naor
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Michael W Panas
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Nicole Marino
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Michael J Coffey
- Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Melbourne, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Christopher J Tonkin
- Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Melbourne, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
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8
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Marino ND, Panas MW, Franco M, Theisen TC, Naor A, Rastogi S, Buchholz KR, Lorenzi HA, Boothroyd JC. Identification of a novel protein complex essential for effector translocation across the parasitophorous vacuole membrane of Toxoplasma gondii. PLoS Pathog 2018; 14:e1006828. [PMID: 29357375 PMCID: PMC5794187 DOI: 10.1371/journal.ppat.1006828] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [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: 08/01/2017] [Revised: 02/01/2018] [Accepted: 12/18/2017] [Indexed: 01/08/2023] Open
Abstract
Toxoplasma gondii is an obligate intracellular parasite that can infect virtually all nucleated cells in warm-blooded animals. The ability of Toxoplasma tachyzoites to infect and successfully manipulate its host is dependent on its ability to transport "GRA" proteins that originate in unique secretory organelles called dense granules into the host cell in which they reside. GRAs have diverse roles in Toxoplasma's intracellular lifecycle, including co-opting crucial host cell functions and proteins, such as the cell cycle, c-Myc and p38 MAP kinase. Some of these GRA proteins, such as GRA16 and GRA24, are secreted into the parasitophorous vacuole (PV) within which Toxoplasma replicates and are transported across the PV membrane (PVM) into the host cell, but the translocation process and its machinery are not well understood. We previously showed that TgMYR1, which is cleaved by TgASP5 into two fragments, localizes to the PVM and is essential for GRA transport into the host cell. To identify additional proteins necessary for effector transport, we screened Toxoplasma mutants defective in c-Myc up-regulation for their ability to export GRA16 and GRA24 to the host cell nucleus. Here we report that novel proteins MYR2 and MYR3 play a crucial role in translocation of a subset of GRAs into the host cell. MYR2 and MYR3 are secreted into the PV space and co-localize with PV membranes and MYR1. Consistent with their predicted transmembrane domains, all three proteins are membrane-associated, and MYR3, but not MYR2, stably associates with MYR1, whose N- and C-terminal fragments are disulfide-linked. We further show that fusing intrinsically disordered effectors to a structured DHFR domain blocks the transport of other effectors, consistent with a translocon-based model of effector transport. Overall, these results reveal a novel complex at the PVM that is essential for effector translocation into the host cell.
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Affiliation(s)
- Nicole D. Marino
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Michael W. Panas
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Magdalena Franco
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Terence C. Theisen
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Adit Naor
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Suchita Rastogi
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Kerry R. Buchholz
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Hernan A. Lorenzi
- Department of Infectious Diseases, J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - John C. Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
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9
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Coffey MJ, Sleebs BE, Uboldi AD, Garnham A, Franco M, Marino ND, Panas MW, Ferguson DJ, Enciso M, O'Neill MT, Lopaticki S, Stewart RJ, Dewson G, Smyth GK, Smith BJ, Masters SL, Boothroyd JC, Boddey JA, Tonkin CJ. An aspartyl protease defines a novel pathway for export of Toxoplasma proteins into the host cell. eLife 2015; 4. [PMID: 26576949 PMCID: PMC4764566 DOI: 10.7554/elife.10809] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/18/2015] [Indexed: 02/03/2023] Open
Abstract
Infection by Toxoplasma gondii leads to massive changes to the host cell. Here, we identify a novel host cell effector export pathway that requires the Golgi-resident aspartyl protease 5 (ASP5). We demonstrate that ASP5 cleaves a highly constrained amino acid motif that has similarity to the PEXEL-motif of Plasmodium parasites. We show that ASP5 matures substrates at both the N- and C-terminal ends of proteins and also controls trafficking of effectors without this motif. Furthermore, ASP5 controls establishment of the nanotubular network and is required for the efficient recruitment of host mitochondria to the vacuole. Assessment of host gene expression reveals that the ASP5-dependent pathway influences thousands of the transcriptional changes that Toxoplasma imparts on its host cell. All these changes result in attenuation of virulence of Δasp5 tachyzoites in vivo. This work characterizes the first identified machinery required for export of Toxoplasma effectors into the infected host cell. DOI:http://dx.doi.org/10.7554/eLife.10809.001 Toxoplasma gondii is a parasite that is thought to infect over two billion people worldwide. Often these infections cause no noticeable symptoms, but can cause serious illness in people with weakened immune systems. Toxoplasma parasites must enter human cells in order to survive. To dramatically increase their chances of survival, the parasites then deliver specialized proteins into the host cell that disarm the host’s immune defenses. Understanding how these specialized proteins are transported from inside the parasite into the host cell, and how this process can be blocked, may lead to new treatments for these and related parasitic infections. By genetically modifying Toxoplasma parasites to lack a parasite enzyme, Coffey et al. have now discovered that this molecule is required for correctly transporting parasite proteins. This enzyme is called aspartyl protease 5 (ASP5) and is found in the parasite in a structure called the Golgi apparatus, which acts as a main hub for protein transport. ASP5 cuts proteins at a ‘barcode’ that is found in many different types of proteins, priming them for transport out of the parasite and for export into the host cell in some cases. Coffey et al. show that in parasites that lack ASP5, these proteins are no longer cleaved and are not transported correctly, blocking the activities that parasites normally perform to ensure their survival. Therefore, ASP5 plays an important role in transporting a wide range of proteins associated with disease, including transporting certain proteins directly into the host cell. Future studies that compare parasites that lack ASP5 to normal parasites will aim to identify new proteins used by the parasites to defeat the host’s immune defenses. DOI:http://dx.doi.org/10.7554/eLife.10809.002
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Affiliation(s)
- Michael J Coffey
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Brad E Sleebs
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Alessandro D Uboldi
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Alexandra Garnham
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Magdalena Franco
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Nicole D Marino
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Michael W Panas
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - David Jp Ferguson
- Nuffield Department of Clinical Laboratory Science, Oxford University, John Radcliffe Hospital, Oxford, United Kingdom
| | - Marta Enciso
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Matthew T O'Neill
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Sash Lopaticki
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Rebecca J Stewart
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Grant Dewson
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Gordon K Smyth
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - Brian J Smith
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Seth L Masters
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - John C Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Justin A Boddey
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Christopher J Tonkin
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, The University of Melbourne, Melbourne, Australia
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Venkataswamy MM, Ng TW, Kharkwal SS, Carreño LJ, Johnson AJ, Kunnath-Velayudhan S, Liu Z, Bittman R, Jervis PJ, Cox LR, Besra GS, Wen X, Yuan W, Tsuji M, Li X, Ho DD, Chan J, Lee S, Frothingham R, Haynes BF, Panas MW, Gillard GO, Sixsmith JD, Korioth-Schmitz B, Schmitz JE, Larsen MH, Jacobs WR, Porcelli SA. Improving Mycobacterium bovis bacillus Calmette-Guèrin as a vaccine delivery vector for viral antigens by incorporation of glycolipid activators of NKT cells. PLoS One 2014; 9:e108383. [PMID: 25255287 PMCID: PMC4177913 DOI: 10.1371/journal.pone.0108383] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [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: 05/27/2014] [Accepted: 08/20/2014] [Indexed: 01/13/2023] Open
Abstract
Recombinant Mycobacterium bovis bacillus Calmette-Guèrin (rBCG) has been explored as a vector for vaccines against HIV because of its ability to induce long lasting humoral and cell mediated immune responses. To maximize the potential for rBCG vaccines to induce effective immunity against HIV, various strategies are being employed to improve its ability to prime CD8+ T cells, which play an important role in the control of HIV infections. In this study we adopted a previously described approach of incorporating glycolipids that activate CD1d-restricted natural killer T (NKT) cells to enhance priming of CD8+ T cells by rBCG strains expressing an SIV Gag antigen (rBCG-SIV gag). We found that the incorporation of the synthetic NKT activating glycolipid α-galactosylceramide (α-GC) into rBCG-SIV gag significantly enhanced CD8+ T cell responses against an immunodominant Gag epitope, compared to responses primed by unmodified rBCG-SIV gag. The abilities of structural analogues of α-GC to enhance CD8+ T cell responses to rBCG were compared in both wild type and partially humanized mice that express human CD1d molecules in place of mouse CD1d. These studies identified an α-GC analogue known as 7DW8-5, which has previously been used successfully as an adjuvant in non-human primates, as a promising compound for enhancing immunogenicity of antigens delivered by rBCG.vectors. Our findings support the incorporation of synthetic glycolipid activators of NKT cells as a novel approach to enhance the immunogenicity of rBCG-vectored antigens for induction of CD8+ T cell responses. The glycolipid adjuvant 7DW8-5 may be a promising candidate for advancing to non-human primate and human clinical studies for the development of HIV vaccines based on rBCG vectors.
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Affiliation(s)
- Manjunatha M. Venkataswamy
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- National Institute of Mental Health and Neuroscience, Bangalore, Karnataka, India
| | - Tony W. Ng
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Shalu S. Kharkwal
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Leandro J. Carreño
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Millennium Institute on Immunology and Immunotherapy, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Alison J. Johnson
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Shajo Kunnath-Velayudhan
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Zheng Liu
- Department of Chemistry and Biochemistry, Queens College of City University of New York, Flushing, New York, United States of America
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College of City University of New York, Flushing, New York, United States of America
| | - Peter J. Jervis
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Liam R. Cox
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Gurdyal S. Besra
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Xiangshu Wen
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Weiming Yuan
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Moriya Tsuji
- Aaron Diamond AIDS Research Center, Rockefeller University, New York, New York, United States of America
| | - Xiangming Li
- Aaron Diamond AIDS Research Center, Rockefeller University, New York, New York, United States of America
| | - David D. Ho
- Aaron Diamond AIDS Research Center, Rockefeller University, New York, New York, United States of America
| | - John Chan
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Sunhee Lee
- Duke University Medical Center, Durham, North Carolina, United States of America
| | - Richard Frothingham
- Duke University Medical Center, Durham, North Carolina, United States of America
| | - Barton F. Haynes
- Duke University Medical Center, Durham, North Carolina, United States of America
| | - Michael W. Panas
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Geoffrey O. Gillard
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jaimie D. Sixsmith
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Birgit Korioth-Schmitz
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joern E. Schmitz
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michelle H. Larsen
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - William R. Jacobs
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Steven A. Porcelli
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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11
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Gillard GO, Bivas-Benita M, Hovav AH, Grandpre LE, Panas MW, Seaman MS, Haynes BF, Letvin NL. Thy1+ NK [corrected] cells from vaccinia virus-primed mice confer protection against vaccinia virus challenge in the absence of adaptive lymphocytes. PLoS Pathog 2011; 7:e1002141. [PMID: 21829360 PMCID: PMC3150274 DOI: 10.1371/journal.ppat.1002141] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 05/09/2011] [Indexed: 11/29/2022] Open
Abstract
While immunological memory has long been considered the province of T- and B- lymphocytes, it has recently been reported that innate cell populations are capable of mediating memory responses. We now show that an innate memory immune response is generated in mice following infection with vaccinia virus, a poxvirus for which no cognate germline-encoded receptor has been identified. This immune response results in viral clearance in the absence of classical adaptive T and B lymphocyte populations, and is mediated by a Thy1+ subset of natural killer (NK) cells. We demonstrate that immune protection against infection from a lethal dose of virus can be adoptively transferred with memory hepatic Thy1+ NK cells that were primed with live virus. Our results also indicate that, like classical immunological memory, stronger innate memory responses form in response to priming with live virus than a highly attenuated vector. These results demonstrate that a defined innate memory cell population alone can provide host protection against a lethal systemic infection through viral clearance. Immunological memory is a hallmark of adaptive immunity and provides the basis for our ability to become ‘immune’ to pathogens to which we have previously been exposed, and provides the basis for vaccination. For decades, the paradigm held that only the classical adaptive lymphocytes were capable of forming and maintaining protective immunological memory. Recently, several papers have shown the capacity of an innate cell population, a subset of natural killer (NK) cells, to exhibit certain aspects of immunological memory. Here we show that innate memory forms in response to infection with vaccinia virus and resides in a discrete subset of NK cells. We further demonstrate that this innate memory provides significant host protection against a subsequent systemic infection with a lethal dose of vaccinia virus, in some cases resulting in the complete clearance of detectable virus. We also demonstrate that priming with live, replicating virus stimulates innate memory more robustly than a highly attenuated vector. These findings shed new light on this emergent area of immunology, and hold significant implications for harnessing innate memory as part of creating novel vaccination strategies.
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Affiliation(s)
- Geoffrey O. Gillard
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Maytal Bivas-Benita
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Avi-Hai Hovav
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
- Institute of Dental Sciences, Hebrew University-Hadassah School of Dental Medicine, Jerusalem, Israel
| | - Lauren E. Grandpre
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael W. Panas
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael S. Seaman
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Barton F. Haynes
- Duke University School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Norman L. Letvin
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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12
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Barker BR, Gladstone MN, Gillard GO, Panas MW, Letvin NL. Critical role for IL-21 in both primary and memory anti-viral CD8+ T-cell responses. Eur J Immunol 2010; 40:3085-96. [PMID: 21061439 DOI: 10.1002/eji.200939939] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 07/14/2010] [Accepted: 08/20/2010] [Indexed: 11/08/2022]
Abstract
While it is well established that CD8(+) T cells generated in the absence of CD4(+) T cells mediate defective recall responses, the mechanism by which CD4(+) T cells confer help in the generation of CD8(+) T-cell responses remains poorly understood. To determine whether CD4(+) T-cell-derived IL-21 is an important regulator of CD8(+) T-cell responses in help-dependent and -independent viral infections, we examined these responses in the IL-21Rα(-/-) mouse model. We show that IL-21 has a role in primary CD8(+) T-cell responses and in recall CD8(+) T-cell responses in help-dependent viral infections. This effect is due to a direct action of IL-21 in enhancing the proliferation of virus-specific CD8(+) T cells and reducing their TRAIL expression. These findings indicate that IL-21 is an important mediator of CD4(+) T-cell help to CD8(+) T cells.
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Affiliation(s)
- Brianne R Barker
- Division of Viral Pathogenesis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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13
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Hovav AH, Panas MW, Rahman S, Sircar P, Gillard G, Cayabyab MJ, Letvin NL. Duration of antigen expression in vivo following DNA immunization modifies the magnitude, contraction, and secondary responses of CD8+ T lymphocytes. J Immunol 2007; 179:6725-33. [PMID: 17982062 DOI: 10.4049/jimmunol.179.10.6725] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The duration of Ag expression in vivo has been reported to have a minimal impact on both the magnitude and kinetics of contraction of a pathogen-induced CD8(+) T cell response. In this study, we controlled the duration of Ag expression by excising the ear pinnae following intradermal ear pinnae DNA immunization. This resulted in decreased magnitude, accelerated contraction and differentiation, and surprisingly greater secondary CD8(+) T cell responses. Furthermore, we found delayed and prolonged Ag presentation in the immunized mice; however, this presentation was considerably decreased when the depot Ag was eliminated. These findings suggest that the magnitude and the contraction phase of the CD8(+) T cell response following intradermal DNA immunization is regulated by the duration rather than the initial exposure to Ag.
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Affiliation(s)
- Avi-Hai Hovav
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
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14
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Hovav AH, Panas MW, Osuna CE, Cayabyab MJ, Autissier P, Letvin NL. The impact of a boosting immunogen on the differentiation of secondary memory CD8+ T cells. J Virol 2007; 81:12793-802. [PMID: 17881444 PMCID: PMC2169130 DOI: 10.1128/jvi.01519-07] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [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: 12/26/2022] Open
Abstract
While recent studies have demonstrated that secondary CD8+ T cells develop into effector-memory cells, the impact of particular vaccine regimens on the elicitation of these cells remains poorly defined. In the present study we evaluated the effect of three different immunogens--recombinant vaccinia, recombinant adenovirus, and plasmid DNA--on the generation of memory cellular immune responses. We found that vectors that induce the rapid movement of CD8+ T cells into the memory compartment during a primary immune response also drive a rapid differentiation of these cells into effector-memory CD8+ T cells following a secondary immunization. In contrast, the functional profiles of both CD8+ and CD4+ T cells, assessed by measuring antigen-stimulated gamma interferon and interleukin-2 production, were not predominantly shaped by the boosting immunogen. We also demonstrated that the in vivo expression of antigen by recombinant vectors was brief following boosting immunization, suggesting that antigen persistence has a minimal impact on the differentiation of secondary CD8+ T cells. When used in heterologous or in homologous prime-boost combinations, these three vectors generated antigen-specific CD8+ T cells with different phenotypic profiles. Expression of the memory-associated molecule CD27 on effector CD8+ T cells decreased following heterologous but not homologous boosting, resulting in a phenotypic profile similar to that seen on primary CD8+ T cells. These data therefore suggest that the phenotype of secondary CD8+ T cells is determined predominantly by the boosting immunogen whereas the cytokine profile of these cells is shaped by both the priming and boosting immunogens.
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Affiliation(s)
- Avi-Hai Hovav
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02115, USA
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15
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Hovav AH, Cayabyab MJ, Panas MW, Santra S, Greenland J, Geiben R, Haynes BF, Jacobs WR, Letvin NL. Rapid memory CD8+ T-lymphocyte induction through priming with recombinant Mycobacterium smegmatis. J Virol 2006; 81:74-83. [PMID: 17050608 PMCID: PMC1797252 DOI: 10.1128/jvi.01269-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [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: 01/26/2023] Open
Abstract
The most promising vaccine strategies for the induction of cytotoxic-T-lymphocyte responses have been heterologous prime/boost regimens employing a plasmid DNA prime and a live recombinant-vector boost. The priming immunogen in these regimens must elicit antigen-specific memory CD8+ T lymphocytes that will expand following the boosting immunization. Because plasmid DNA immunogens are expensive and their immunogenicity has proven disappointing in human clinical trials, we have been exploring novel priming immunogens that might be used in heterologous immunization regimens. Here we show that priming with a prototype recombinant Mycobacterium smegmatis strain expressing human immunodeficiency virus type 1 (HIV-1) gp120-elicited CD4+ T lymphocytes with a functional profile of helper cells as well as a CD8+ T-lymphocyte population. These CD8+ T lymphocytes rapidly differentiated to memory cells, defined on the basis of their cytokine profile and expression of CD62L and CD27. Moreover, these recombinant-mycobacterium-induced T lymphocytes rapidly expanded following boosting with a recombinant adenovirus expressing HIV-1 Env to gp120-specific CD8+ T lymphocytes. This work demonstrates a remarkable skewing of recombinant-mycobacterium-induced T lymphocytes to durable antigen-specific memory CD8+ T cells and suggests that such immunogens might be used as priming vectors in prime/boost vaccination regimens for the induction of cellular immune responses.
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Affiliation(s)
- Avi-Hai Hovav
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02115, USA
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