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Thaprawat P, Zhang Z, Rentchler EC, Wang F, Chalasani S, Giuliano CJ, Lourido S, Di Cristina M, Klionsky DJ, Carruthers VB. TgATG9 is required for autophagosome biogenesis and maintenance of chronic infection in Toxoplasma gondii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.08.602581. [PMID: 39026823 PMCID: PMC11257638 DOI: 10.1101/2024.07.08.602581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Toxoplasma gondii is a ubiquitous protozoan parasite that can reside long-term within hosts as intracellular tissue cysts comprised of chronic stage bradyzoites. To perturb chronic infection requires a better understanding of the cellular processes that mediate parasite persistence. Macroautophagy/autophagy is a catabolic and homeostatic pathway that is required for T. gondii chronic infection, although the molecular details of this process remain poorly understood. A key step in autophagy is the initial formation of the phagophore that sequesters cytoplasmic components and matures into a double-membraned autophagosome for delivery of the cargo to a cell's digestive organelle for degradative recycling. While T. gondii appears to have a reduced repertoire of autophagy proteins, it possesses a putative phospholipid scramblase, TgATG9. Through structural modeling and complementation assays, we show herein that TgATG9 can partially rescue bulk autophagy in atg9Δ yeast. We demonstrated the importance of TgATG9 for proper autophagosome dynamics at the subcellular level using three-dimensional live cell lattice light sheet microscopy. Conditional knockdown of TgATG9 in T. gondii after bradyzoite differentiation resulted in markedly reduced parasite viability. Together, our findings provide insights into the molecular dynamics of autophagosome biogenesis within an early-branching eukaryote and pinpoint the indispensable role of autophagy in maintaining T. gondii chronic infection.
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Wu M, Ying J, Lin X, Xu C, Zheng X, Zheng Y, Fang Z, Yan B, Zhang N, Mou Y, Tan F. Toxoplasma gondii autophagy-related protein ATG7 maintains apicoplast inheritance by stabilizing and lipidating ATG8. Biochim Biophys Acta Mol Basis Dis 2024; 1870:166891. [PMID: 37739091 DOI: 10.1016/j.bbadis.2023.166891] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/12/2023] [Accepted: 09/19/2023] [Indexed: 09/24/2023]
Abstract
ATG8/LC3-mediated autophagosome formation is a key rate-limiting step in the process of autophagy. The parasitic protist Toxoplasma gondii possesses a single ATG8 homolog (TgATG8), which can localize to either cytosolic autophagosome involved in delivery of autophagic material in bradyzoites, or the outermost membrane of apicoplast, a nonphotosynthetic plastid-like organelle, responsible for maintaining homeostasis in tachyzoites. However, mechanisms that regulate TgATG8 remain insufficiently understood. Here, a TgATG7 conditional knockdown line that we have generated is severely impaired in parasite's growth and exhibits significant defects in the organelle level, strikingly with a fragmentation of the mitochondrial network and a loss of the apicoplast. Specific TgATG7C1133S point mutant complemented line showed that these defects were associated with its E1-type enzyme activity. Both depletion of TgATG7 and mutation of its catalytic cysteine 1133 hindered TgATG8 lipidation and apicoplast localization. Unexpectedly, we also found that depletion of TgATG7 reduced the unlipidated TgATG8 protein level. Subsequently, we determined that TgATG7 was able to interact with TgATG8 directly via its C-terminal domain and multi-monoubiquitination stimulated proteasome-dependent degradation of TgATG8, while TgATG7 could inhibit the degradation through stabilization of TgATG8. Additionally, we identified a putative TgATG8 interacting fragment of TgATG7, 1281-1290aa. Depletion of the fragment impaired the parasite growth and apicoplast inheritance. To our knowledge, our study is the first to elucidate the role of TgATG7 and the ubiquitin-proteasome system in synergistically regulating the non-lipidated pool of TgATG8, suggesting a potential homeostatic mechanism responsible for balancing autophagic activity in T. gondii.
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Affiliation(s)
- Mimi Wu
- The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou Medical University, Wenzhou, Zhejiang, China; Department of Parasitology, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jiaqi Ying
- School of the Second Clinical Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xuejing Lin
- Department of Parasitology, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Chao Xu
- The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiaozi Zheng
- Teaching Center of Morphological Experiment, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yi Zheng
- Laser Confocal Microscope Lab, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhouxi Fang
- Zhejiang Provincial Key Laboratory for Technology and Application of Model Organisms, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Baolong Yan
- Department of Parasitology, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Nu Zhang
- The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Yani Mou
- Department of Parasitology, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Feng Tan
- The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou Medical University, Wenzhou, Zhejiang, China; Department of Parasitology, School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.
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Mishra A, Varshney A, Mishra S. Regulation of Atg8 membrane deconjugation by cysteine proteases in the malaria parasite Plasmodium berghei. Cell Mol Life Sci 2023; 80:344. [PMID: 37910326 PMCID: PMC11073460 DOI: 10.1007/s00018-023-05004-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 09/22/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023]
Abstract
During macroautophagy, the Atg8 protein is conjugated to phosphatidylethanolamine (PE) in autophagic membranes. In Apicomplexan parasites, two cysteine proteases, Atg4 and ovarian tumor unit (Otu), have been identified to delipidate Atg8 to release this protein from membranes. Here, we investigated the role of cysteine proteases in Atg8 conjugation and deconjugation and found that the Plasmodium parasite consists of both activities. We successfully disrupted the genes individually; however, simultaneously, they were refractory to deletion and essential for parasite survival. Mutants lacking Atg4 and Otu showed normal blood and mosquito stage development. All mice infected with Otu KO sporozoites became patent; however, Atg4 KO sporozoites either failed to establish blood infection or showed delayed patency. Through in vitro and in vivo analysis, we found that Atg4 KO sporozoites invade and normally develop into early liver stages. However, nuclear and organelle differentiation was severely hampered during late stages and failed to mature into hepatic merozoites. We found a higher level of Atg8 in Atg4 KO parasites, and the deconjugation of Atg8 was hampered. We confirmed Otu localization on the apicoplast; however, parasites lacking Otu showed no visible developmental defects. Our data suggest that Atg4 is the primary deconjugating enzyme and that Otu cannot replace its function completely because it cleaves the peptide bond at the N-terminal side of glycine, thereby irreversibly inactivating Atg8 during its recycling. These findings highlight a role for the Atg8 deconjugation pathway in organelle biogenesis and maintenance of the homeostatic cellular balance.
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Affiliation(s)
- Akancha Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Aastha Varshney
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Satish Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
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Devarakonda PM, Sarmiento V, Heaslip AT. F-actin and myosin F control apicoplast elongation dynamics which drive apicoplast-centrosome association in Toxoplasma gondii. mBio 2023; 14:e0164023. [PMID: 37732764 PMCID: PMC10653800 DOI: 10.1128/mbio.01640-23] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 07/26/2023] [Indexed: 09/22/2023] Open
Abstract
IMPORTANCE Toxoplasma gondii and most other parasites in the phylum Apicomplexa contain an apicoplast, a non-photosynthetic plastid organelle required for fatty acid, isoprenoid, iron-sulfur cluster, and heme synthesis. Perturbation of apicoplast function results in parasite death. Thus, parasite survival critically depends on two cellular processes: apicoplast division to ensure every daughter parasite inherits a single apicoplast, and trafficking of nuclear encoded proteins to the apicoplast. Despite the importance of these processes, there are significant knowledge gaps in regards to the molecular mechanisms which control these processes; this is particularly true for trafficking of nuclear-encoded apicoplast proteins. This study provides crucial new insight into the timing of apicoplast protein synthesis and trafficking to the apicoplast. In addition, this study demonstrates how apicoplast-centrosome association, a key step in the apicoplast division cycle, is controlled by the actomyosin cytoskeleton.
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Affiliation(s)
| | - Valeria Sarmiento
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Aoife T. Heaslip
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
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Devarakonda PM, Sarmiento V, Heaslip AT. F-actin and Myosin F control apicoplast elongation dynamics which drive apicoplast-centrosome association in Toxoplasma gondii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.01.521342. [PMID: 36711828 PMCID: PMC9881852 DOI: 10.1101/2023.01.01.521342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Toxoplasma gondii contains an essential plastid organelle called the apicoplast that is necessary for fatty acid, isoprenoid, and heme synthesis. Perturbations affecting apicoplast function or inheritance lead to parasite death. The apicoplast is a single copy organelle and therefore must be divided so that each daughter parasite inherits an apicoplast during cell division. In this study we identify new roles for F-actin and an unconventional myosin motor, TgMyoF, in this process. First, loss of TgMyoF and actin lead to an accumulation of apicoplast vesicles in the cytosol indicating a role for this actomyosin system in apicoplast protein trafficking or morphological integrity of the organelle. Second, live cell imaging reveals that during division the apicoplast is highly dynamic, exhibiting branched, U-shaped and linear morphologies that are dependent on TgMyoF and actin. In parasites where movement was inhibited by the depletion of TgMyoF, the apicoplast fails to associate with the parasite centrosomes. Thus, this study provides crucial new insight into mechanisms controlling apicoplast-centrosome association, a vital step in the apicoplast division cycle, which ensures that each daughter inherits a single apicoplast.
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Wilde ML, Ruparel U, Klemm T, Lee VV, Calleja DJ, Komander D, Tonkin CJ. Characterisation of the OTU domain deubiquitinase complement of Toxoplasma gondii. Life Sci Alliance 2023; 6:e202201710. [PMID: 36958824 PMCID: PMC10038098 DOI: 10.26508/lsa.202201710] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 03/15/2023] [Accepted: 03/15/2023] [Indexed: 03/25/2023] Open
Abstract
The phylum Apicomplexa contains several parasitic species of medical and agricultural importance. The ubiquitination machinery remains, for the most part, uncharacterised in apicomplexan parasites, despite the important roles that it plays in eukaryotic biology. Bioinformatic analysis of the ubiquitination machinery in apicomplexan parasites revealed an expanded ovarian tumour domain-containing (OTU) deubiquitinase (DUB) family in Toxoplasma, potentially reflecting functional importance in apicomplexan parasites. This study presents comprehensive characterisation of Toxoplasma OTU DUBs. AlphaFold-guided structural analysis not only confirmed functional orthologues found across eukaryotes, but also identified apicomplexan-specific enzymes, subsequently enabling discovery of a cryptic OTU DUB in Plasmodium species. Comprehensive biochemical characterisation of 11 Toxoplasma OTU DUBs revealed activity against ubiquitin- and NEDD8-based substrates and revealed ubiquitin linkage preferences for Lys6-, Lys11-, Lys48-, and Lys63-linked chain types. We show that accessory domains in Toxoplasma OTU DUBs impose linkage preferences, and in case of apicomplexan-specific TgOTU9, we discover a cryptic ubiquitin-binding domain that is essential for TgOTU9 activity. Using the auxin-inducible degron (AID) to generate knockdown parasite lines, TgOTUD6B was found to be important for Toxoplasma growth.
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Affiliation(s)
- Mary-Louise Wilde
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Ushma Ruparel
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Theresa Klemm
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - V Vern Lee
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, Parkville, Australia; and Department of Biochemistry and Pharmacology, The University of Melbourne, Melbourne, Australia
| | - Dale J Calleja
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - David Komander
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Christopher J Tonkin
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; and Department of Medical Biology, University of Melbourne, Melbourne, Australia
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Walczak M, Meister TR, Nguyen HM, Zhu Y, Besteiro S, Yeh E. Structure-Function Relationship for a Divergent Atg8 Protein Required for a Nonautophagic Function in Apicomplexan Parasites. mBio 2023; 14:e0364221. [PMID: 36625582 PMCID: PMC9973341 DOI: 10.1128/mbio.03642-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Atg8 family proteins are highly conserved eukaryotic proteins with diverse autophagy and nonautophagic functions in eukaryotes. While the structural features required for conserved autophagy functions of Atg8 are well established, little is known about the molecular changes that facilitated acquisition of divergent, nonautophagic functions of Atg8. The malaria parasite Plasmodium falciparum offers a unique opportunity to study nonautophagic functions of Atg8 family proteins because it encodes a single Atg8 homolog whose only essential function is in the inheritance of an unusual secondary plastid called the apicoplast. Here, we used functional complementation to investigate the structure-function relationship for this divergent Atg8 protein. We showed that the LC3-interacting region (LIR) docking site (LDS), the major interaction interface of the Atg8 protein family, is required for P. falciparum Atg8 (PfAtg8) apicoplast localization and function, likely via Atg8 lipidation. On the other hand, another region previously implicated in canonical Atg8 interactions, the N-terminal helix, is not required for apicoplast-specific PfAtg8 function. Finally, our investigations at the cellular level demonstrate that the unique apicomplexan-specific loop, previously implicated in interaction with membrane conjugation machinery in recombinant protein-based in vitro assays, is not required for membrane conjugation nor for the apicoplast-specific effector function of Atg8 in both P. falciparum and related Apicomplexa member Toxoplasma gondii. These results suggest that the effector function of apicomplexan Atg8 is mediated by structural features distinct from those previously identified for macroautophagy and selective autophagy functions. IMPORTANCE The most extensively studied role of Atg8 proteins is in autophagy. However, it is clear that they have other nonautophagic functions critical to cell function and disease pathogenesis that are so far understudied compared to their canonical role in autophagy. Mammalian cells contain multiple Atg8 paralogs that have diverse, specialized functions. Gaining molecular insight into their nonautophagic functions is difficult because of redundancy between the homologs and their role in both autophagy and nonautophagic pathways. Malaria parasites such as Plasmodium falciparum are a unique system to study a novel, nonautophagic function of Atg8 separate from its role in autophagy: they have only one Atg8 protein whose only essential function is in the inheritance of the apicoplast, a unique secondary plastid organelle. Insights into the molecular basis of PfAtg8's function in apicoplast biogenesis will have important implications for the evolution of diverse nonautophagic functions of the Atg8 protein family.
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Affiliation(s)
- Marta Walczak
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
| | - Thomas R. Meister
- Department of Molecular and Cellular Physiology, Stanford School of Medicine, Stanford, California, USA
| | - Hoa Mai Nguyen
- LPHI UMR5235, University of Montpellier, CNRS, Montpellier, France
| | - Yili Zhu
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
| | | | - Ellen Yeh
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
- Department of Microbiology & Immunology, Stanford School of Medicine, Stanford, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
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Liu B, Yan Y, Wang X, Chen N, Wu J. Locally generated C3 regulates the clearance of Toxoplasma gondii by IFN-γ-primed macrophage through regulation of xenophagy. Front Microbiol 2022; 13:944006. [PMID: 35992649 PMCID: PMC9386420 DOI: 10.3389/fmicb.2022.944006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 07/18/2022] [Indexed: 11/13/2022] Open
Abstract
Exogenous pathogen infection can induce autophagy in cells. Autophagy is essential for cell survival, development, and homeostasis. It not only regulates cell defense and stress, but also has a close relationship with innate and adaptive immunity. Complement is an important part of innate immunity, which could be activated by three approaches, including classic, alternative, and lectin pathways. All the three pathways result in the activation of C3, and generate anaphylatoxin fragments C3a and C5a, and formation of the membrane attack complex. Either C3a or C5a induces the inflammatory cytokines through binding to C3aR or C5aR, respectively. However, it is still unknown whether the complement could regulate the autophagy of intracellular microorganisms or not. In this study, we constructed a Toxoplasma gondii (T. gondii) and macrophages co-culture experimental model using T. gondii expressing enhanced green fluorescence protein (EGFP) fluorescence and C3−/-C57BL/6 J mice for that T. gondii invaded peritoneal macrophages in mice. Western blot, laser confocal microscopy (LCM), and transmission electron microscopy (TEM) were used to observe the changes of autophagy between the macrophages from wild-type (WT) and C3−/− mice. Flow cytometry and LCM were used to investigate the effect of autophagy on the killing ability of macrophages against T. gondii. Here, we found that local C3 could suppress not only the canonical autophagy of macrophage, but also the xenophagy to T. gondii. Interestingly, the inhibition of C3 on host cell autophagy could significantly suppress the clearance of T. gondii by the IFN-γ-primed macrophage. Finally, we investigated the mechanism of the autophagy regulation of C3 that the effect of C3 on the macrophage-specific autophagy against T. gondii depends on mTOR. And, there is C3a but not C5a/C5aR involved in regulating macrophage xenophagy against T. gondii. Collectively, our findings suggest locally generated C3 regulates the clearance of T. gondii by Macrophage through the regulation of the non-canonical IFN-γ-dependent autophagy pathway, and paint a clearer picture in the regulation of autophagy by innate immune components.
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Affiliation(s)
- Bo Liu
- Department of Hematology. The No. 967 Hospital of PLA Joint Logistics Support Force, Dalian, Liaoning, China
| | - Yan Yan
- Translational Medicine Research Center, Medical Innovation Research Division, The Chinese PLA General Hospital, Beijing, China
| | - Xiaoreng Wang
- Laboratory of Radiation Injury Treatment, Medical Innovation Research Division, The Chinese PLA General Hospital, Beijing, China
| | - Nannan Chen
- Department of Hematology. The No. 967 Hospital of PLA Joint Logistics Support Force, Dalian, Liaoning, China
- Nannan Chen,
| | - Jue Wu
- Translational Medicine Research Center, Medical Innovation Research Division, The Chinese PLA General Hospital, Beijing, China
- *Correspondence: Jue Wu,
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