1
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Rahaman MH, Thygesen SJ, Maxwell MJ, Kim H, Mudai P, Nanson JD, Jia X, Vajjhala PR, Hedger A, Vetter I, Haselhorst T, Robertson AAB, Dymock B, Ve T, Mobli M, Stacey KJ, Kobe B. o-Vanillin binds covalently to MAL/TIRAP Lys-210 but independently inhibits TLR2. J Enzyme Inhib Med Chem 2024; 39:2313055. [PMID: 38416868 PMCID: PMC10903754 DOI: 10.1080/14756366.2024.2313055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 01/28/2024] [Indexed: 03/01/2024] Open
Abstract
Toll-like receptor (TLR) innate immunity signalling protects against pathogens, but excessive or prolonged signalling contributes to a range of inflammatory conditions. Structural information on the TLR cytoplasmic TIR (Toll/interleukin-1 receptor) domains and the downstream adaptor proteins can help us develop inhibitors targeting this pathway. The small molecule o-vanillin has previously been reported as an inhibitor of TLR2 signalling. To study its mechanism of action, we tested its binding to the TIR domain of the TLR adaptor MAL/TIRAP (MALTIR). We show that o-vanillin binds to MALTIR and inhibits its higher-order assembly in vitro. Using NMR approaches, we show that o-vanillin forms a covalent bond with lysine 210 of MAL. We confirm in mouse and human cells that o-vanillin inhibits TLR2 but not TLR4 signalling, independently of MAL, suggesting it may covalently modify TLR2 signalling complexes directly. Reactive aldehyde-containing small molecules such as o-vanillin may target multiple proteins in the cell.
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Affiliation(s)
- Md. Habibur Rahaman
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Sara J. Thygesen
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Michael J. Maxwell
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Hyoyoung Kim
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Prerna Mudai
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Jeffrey D. Nanson
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Xinying Jia
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Parimala R. Vajjhala
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Andrew Hedger
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
- School of Pharmacy, University of Queensland, Brisbane, Australia
| | | | - Avril A. B. Robertson
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Brian Dymock
- Queensland Emory Drug Discovery Initiative, University of Queensland, Brisbane, Australia
| | - Thomas Ve
- Institute for Glycomics, Griffith University, Southport, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Katryn J. Stacey
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
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2
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Pliego Zamora A, Kim J, Vajjhala PR, Thygesen SJ, Watterson D, Modhiran N, Bielefeldt-Ohmann H, Stacey KJ. Kinetics of severe dengue virus infection and development of gut pathology in mice. J Virol 2023; 97:e0125123. [PMID: 37850747 PMCID: PMC10688336 DOI: 10.1128/jvi.01251-23] [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: 08/16/2023] [Accepted: 09/12/2023] [Indexed: 10/19/2023] Open
Abstract
IMPORTANCE Dengue virus, an arbovirus, causes an estimated 100 million symptomatic infections annually and is an increasing threat as the mosquito range expands with climate change. Dengue epidemics are a substantial strain on local economies and health infrastructure, and an understanding of what drives severe disease may enable treatments to help reduce hospitalizations. Factors exacerbating dengue disease are debated, but gut-related symptoms are much more frequent in severe than mild cases. Using mouse models of dengue infection, we have shown that inflammation and damage are earlier and more severe in the gut than in other tissues. Additionally, we observed impairment of the gut mucus layer and propose that breakdown of the barrier function exacerbates inflammation and promotes severe dengue disease. This idea is supported by recent data from human patients showing elevated bacteria-derived molecules in dengue patient serum. Therapies aiming to maintain gut integrity may help to abrogate severe dengue disease.
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Affiliation(s)
- Adriana Pliego Zamora
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Jaehyeon Kim
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Parimala R. Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Sara J. Thygesen
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Daniel Watterson
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Queensland, Australia
| | - Naphak Modhiran
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Helle Bielefeldt-Ohmann
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Queensland, Australia
| | - Katryn J. Stacey
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Queensland, Australia
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3
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Curson JE, Liu L, Luo L, Muusse TW, Lucas RM, Gunther KS, Vajjhala PR, Abrol R, Jones A, Kapetanovic R, Stacey KJ, Stow JL, Sweet MJ. TLR4 phosphorylation at tyrosine 672 activates the ERK/c-FOS signaling module for LPS-induced cytokine responses in macrophages. Eur J Immunol 2023; 53:e2250056. [PMID: 37058370 PMCID: PMC10947571 DOI: 10.1002/eji.202250056] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 06/20/2022] [Revised: 03/20/2023] [Accepted: 04/11/2023] [Indexed: 04/15/2023]
Abstract
TLRs engage numerous adaptor proteins and signaling molecules, enabling a complex series of post-translational modifications (PTMs) to mount inflammatory responses. TLRs themselves are post-translationally modified following ligand-induced activation, with this being required to relay the full spectrum of proinflammatory signaling responses. Here, we reveal indispensable roles for TLR4 Y672 and Y749 phosphorylation in mounting optimal LPS-inducible inflammatory responses in primary mouse macrophages. LPS promotes phosphorylation at both tyrosine residues, with Y749 phosphorylation being required for maintenance of total TLR4 protein levels and Y672 phosphorylation exerting its pro-inflammatory effects more selectively by initiating ERK1/2 and c-FOS phosphorylation. Our data also support a role for the TLR4-interacting membrane proteins SCIMP and the SYK kinase axis in mediating TLR4 Y672 phosphorylation to permit downstream inflammatory responses in murine macrophages. The corresponding residue in human TLR4 (Y674) is also required for optimal LPS signaling responses. Our study, thus, reveals how a single PTM on one of the most widely studied innate immune receptors orchestrates downstream inflammatory responses.
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Affiliation(s)
- James E.B. Curson
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Liping Liu
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Lin Luo
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Timothy W. Muusse
- School of Chemistry and Molecular Biosciences (SCMB) and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Richard M. Lucas
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Kimberley S. Gunther
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Parimala R. Vajjhala
- School of Chemistry and Molecular Biosciences (SCMB) and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Rishika Abrol
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Alun Jones
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Ronan Kapetanovic
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland
| | - Katryn J. Stacey
- School of Chemistry and Molecular Biosciences (SCMB) and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Jennifer L. Stow
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
| | - Matthew J. Sweet
- Institute for Molecular Bioscience (IMB)IMB Centre for Inflammation and Disease Research and Australian Infectious Diseases Research CentreThe University of QueenslandBrisbaneQueenslandAustralia
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Holmes S, Clabbers MTB, Muusse TW, Vajjhala PR, Thygesen SJ, Malde AK, Hunter DJB, Croll TI, Flueckiger L, Nanson JD, Rahaman MH, Aquila A, Hunter MS, Liang M, Yoon CH, Zhao J, Zatsepin NA, Abbey B, Sierecki E, Gambin Y, Stacey KJ, Darmanin C, Kobe B, Xu H, Ve T. MyD88 TIR domain higher-order assembly interactions revealed by serial femtosecond crystallography. Acta Crystallogr A Found Adv 2021. [DOI: 10.1107/s0108767321088498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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5
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Clabbers MTB, Holmes S, Muusse TW, Vajjhala PR, Thygesen SJ, Malde AK, Hunter DJB, Croll TI, Flueckiger L, Nanson JD, Rahaman MH, Aquila A, Hunter MS, Liang M, Yoon CH, Zhao J, Zatsepin NA, Abbey B, Sierecki E, Gambin Y, Stacey KJ, Darmanin C, Kobe B, Xu H, Ve T. MyD88 TIR domain higher-order assembly interactions revealed by microcrystal electron diffraction and serial femtosecond crystallography. Nat Commun 2021; 12:2578. [PMID: 33972532 PMCID: PMC8110528 DOI: 10.1038/s41467-021-22590-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [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: 12/24/2020] [Accepted: 03/18/2021] [Indexed: 02/03/2023] Open
Abstract
MyD88 and MAL are Toll-like receptor (TLR) adaptors that signal to induce pro-inflammatory cytokine production. We previously observed that the TIR domain of MAL (MALTIR) forms filaments in vitro and induces formation of crystalline higher-order assemblies of the MyD88 TIR domain (MyD88TIR). These crystals are too small for conventional X-ray crystallography, but are ideally suited to structure determination by microcrystal electron diffraction (MicroED) and serial femtosecond crystallography (SFX). Here, we present MicroED and SFX structures of the MyD88TIR assembly, which reveal a two-stranded higher-order assembly arrangement of TIR domains analogous to that seen previously for MALTIR. We demonstrate via mutagenesis that the MyD88TIR assembly interfaces are critical for TLR4 signaling in vivo, and we show that MAL promotes unidirectional assembly of MyD88TIR. Collectively, our studies provide structural and mechanistic insight into TLR signal transduction and allow a direct comparison of the MicroED and SFX techniques.
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Affiliation(s)
- Max T B Clabbers
- Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Susannah Holmes
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Timothy W Muusse
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Sara J Thygesen
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Alpeshkumar K Malde
- Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Dominic J B Hunter
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, New South Wales, Australia
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Tristan I Croll
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Leonie Flueckiger
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Jeffrey D Nanson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Md Habibur Rahaman
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Andrew Aquila
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Mark S Hunter
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Mengning Liang
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Chun Hong Yoon
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Jingjing Zhao
- Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden
| | - Nadia A Zatsepin
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Brian Abbey
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Emma Sierecki
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, New South Wales, Australia
| | - Yann Gambin
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, New South Wales, Australia
| | - Katryn J Stacey
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Connie Darmanin
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia.
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.
| | - Hongyi Xu
- Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
| | - Thomas Ve
- Institute for Glycomics, Griffith University, Southport, Queensland, Australia.
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Sagulenko V, Vitak N, Vajjhala PR, Vince JE, Stacey KJ. Caspase-1 Is an Apical Caspase Leading to Caspase-3 Cleavage in the AIM2 Inflammasome Response, Independent of Caspase-8. J Mol Biol 2017; 430:238-247. [PMID: 29100888 DOI: 10.1016/j.jmb.2017.10.028] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 10/06/2017] [Accepted: 10/23/2017] [Indexed: 12/13/2022]
Abstract
Canonical inflammasomes are multiprotein complexes that can activate both caspase-1 and caspase-8. Caspase-1 drives rapid lysis of cells by pyroptosis and maturation of interleukin (IL)-1β and IL-18. In caspase-1-deficient cells, inflammasome formation still leads to caspase-3 activation and slower apoptotic death, dependent on caspase-8 as an apical caspase. A role for caspase-8 directly upstream of caspase-1 has also been suggested, but here we show that caspase-8-deficient macrophages have no defect in AIM2 inflammasome-mediated caspase-1 activation, pyroptosis, and IL-1β cleavage. In investigating the inflammasome-induced apoptotic pathway, we previously demonstrated that activated caspase-8 is essential for caspase-3 cleavage and apoptosis in caspase-1-deficient cells. However, here we found that AIM2 inflammasome-initiated caspase-3 cleavage was maintained in Ripk3-/-Casp8-/- macrophages. Gene knockdown showed that caspase-1 was required for the caspase-3 cleavage. Thus inflammasomes activate a network of caspases that can promote both pyroptotic and apoptotic cell death. In cells where rapid pyroptosis is blocked, delayed inflammasome-dependent cell death could still occur due to both caspase-1- and caspase-8-dependent apoptosis. Initiation of redundant cell death pathways is likely to be a strategy for coping with pathogen interference in death processes.
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Affiliation(s)
- Vitaliya Sagulenko
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Nazarii Vitak
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - James E Vince
- Walter and Eliza Hall Institute for Medical Research, Parkville, Vic 3052, Australia
| | - Katryn J Stacey
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
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7
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Vajjhala PR, Ve T, Bentham A, Stacey KJ, Kobe B. The molecular mechanisms of signaling by cooperative assembly formation in innate immunity pathways. Mol Immunol 2017; 86:23-37. [PMID: 28249680 DOI: 10.1016/j.molimm.2017.02.012] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/16/2017] [Accepted: 02/19/2017] [Indexed: 12/25/2022]
Abstract
The innate immune system is the first line of defense against infection and responses are initiated by pattern recognition receptors (PRRs) that detect pathogen-associated molecular patterns (PAMPs). PRRs also detect endogenous danger-associated molecular patterns (DAMPs) that are released by damaged or dying cells. The major PRRs include the Toll-like receptor (TLR) family members, the nucleotide binding and oligomerization domain, leucine-rich repeat containing (NLR) family, the PYHIN (ALR) family, the RIG-1-like receptors (RLRs), C-type lectin receptors (CLRs) and the oligoadenylate synthase (OAS)-like receptors and the related protein cyclic GMP-AMP synthase (cGAS). The different PRRs activate specific signaling pathways to collectively elicit responses including the induction of cytokine expression, processing of pro-inflammatory cytokines and cell-death responses. These responses control a pathogenic infection, initiate tissue repair and stimulate the adaptive immune system. A central theme of many innate immune signaling pathways is the clustering of activated PRRs followed by sequential recruitment and oligomerization of adaptors and downstream effector enzymes, to form higher-order arrangements that amplify the response and provide a scaffold for proximity-induced activation of the effector enzymes. Underlying the formation of these complexes are co-operative assembly mechanisms, whereby association of preceding components increases the affinity for downstream components. This ensures a rapid immune response to a low-level stimulus. Structural and biochemical studies have given key insights into the assembly of these complexes. Here we review the current understanding of assembly of immune signaling complexes, including inflammasomes initiated by NLR and PYHIN receptors, the myddosomes initiated by TLRs, and the MAVS CARD filament initiated by RIG-1. We highlight the co-operative assembly mechanisms during assembly of each of these complexes.
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Affiliation(s)
- Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Thomas Ve
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia; Institute for Glycomics, Griffith University, Southport, QLD 4222, Australia
| | - Adam Bentham
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia; School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia
| | - Katryn J Stacey
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia.
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8
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Fu TM, Li Y, Lu A, Li Z, Vajjhala PR, Cruz AC, Srivastava DB, DiMaio F, Penczek PA, Siegel RM, Stacey KJ, Egelman EH, Wu H. Cryo-EM Structure of Caspase-8 Tandem DED Filament Reveals Assembly and Regulation Mechanisms of the Death-Inducing Signaling Complex. Mol Cell 2016; 64:236-250. [PMID: 27746017 PMCID: PMC5089849 DOI: 10.1016/j.molcel.2016.09.009] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [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: 06/24/2016] [Revised: 08/10/2016] [Accepted: 09/07/2016] [Indexed: 12/20/2022]
Abstract
Caspase-8 activation can be triggered by death receptor-mediated formation of the death-inducing signaling complex (DISC) and by the inflammasome adaptor ASC. Caspase-8 assembles with FADD at the DISC and with ASC at the inflammasome through its tandem death effector domain (tDED), which is regulated by the tDED-containing cellular inhibitor cFLIP and the viral inhibitor MC159. Here we present the caspase-8 tDED filament structure determined by cryoelectron microscopy. Extensive assembly interfaces not predicted by the previously proposed linear DED chain model were uncovered, and were further confirmed by structure-based mutagenesis in filament formation in vitro and Fas-induced apoptosis and ASC-mediated caspase-8 recruitment in cells. Structurally, the two DEDs in caspase-8 use quasi-equivalent contacts to enable assembly. Using the tDED filament structure as a template, structural analyses reveal the interaction surfaces between FADD and caspase-8 and the distinct mechanisms of regulation by cFLIP and MC159 through comingling and capping, respectively.
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Affiliation(s)
- Tian-Min Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Yang Li
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Alvin Lu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Zongli Li
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Anthony C Cruz
- Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH, Bethesda, MD 20892, USA
| | - Devendra B Srivastava
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Pawel A Penczek
- Department of Biochemistry and Molecular Biology, University of Texas-Houston Medical School, Houston, TX 77030, USA
| | - Richard M Siegel
- Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH, Bethesda, MD 20892, USA
| | - Katryn J Stacey
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia; Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA
| | - Hao Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
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Sester DP, Zamoshnikova A, Thygesen SJ, Vajjhala PR, Cridland SO, Schroder K, Stacey KJ. Assessment of Inflammasome Formation by Flow Cytometry. ACTA ACUST UNITED AC 2016; 114:14.40.1-14.40.29. [DOI: 10.1002/cpim.13] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- David P. Sester
- School of Chemistry and Molecular Biosciences, The University of Queensland Brisbane Australia
| | - Alina Zamoshnikova
- Institute for Molecular Bioscience, The University of Queensland Brisbane Australia
| | - Sara J. Thygesen
- School of Chemistry and Molecular Biosciences, The University of Queensland Brisbane Australia
| | - Parimala R. Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland Brisbane Australia
| | - Simon O. Cridland
- School of Chemistry and Molecular Biosciences, The University of Queensland Brisbane Australia
| | - Kate Schroder
- Institute for Molecular Bioscience, The University of Queensland Brisbane Australia
| | - Katryn J. Stacey
- School of Chemistry and Molecular Biosciences, The University of Queensland Brisbane Australia
- Institute for Molecular Bioscience, The University of Queensland Brisbane Australia
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10
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Vajjhala PR, Lu A, Brown DL, Pang SW, Sagulenko V, Sester DP, Cridland SO, Hill JM, Schroder K, Stow JL, Wu H, Stacey KJ. The Inflammasome Adaptor ASC Induces Procaspase-8 Death Effector Domain Filaments. J Biol Chem 2015; 290:29217-30. [PMID: 26468282 DOI: 10.1074/jbc.m115.687731] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Indexed: 01/19/2023] Open
Abstract
Inflammasomes mediate inflammatory and cell death responses to pathogens and cellular stress signals via activation of procaspases-1 and -8. During inflammasome assembly, activated receptors of the NLR or PYHIN family recruit the adaptor protein ASC and initiate polymerization of its pyrin domain (PYD) into filaments. We show that ASC filaments in turn nucleate procaspase-8 death effector domain (DED) filaments in vitro and in vivo. Interaction between ASC PYD and procaspase-8 tandem DEDs optimally required both DEDs and represents an unusual heterotypic interaction between domains of the death fold superfamily. Analysis of ASC PYD mutants showed that interaction surfaces that mediate procaspase-8 interaction overlap with those required for ASC self-association and interaction with the PYDs of inflammasome initiators. Our data indicate that multiple types of death fold domain filaments form at inflammasomes and that PYD/DED and homotypic PYD interaction modes are similar. Interestingly, we observed condensation of procaspase-8 filaments containing the catalytic domain, suggesting that procaspase-8 interactions within and/or between filaments may be involved in caspase-8 activation. Procaspase-8 filaments may also be relevant to apoptosis induced by death receptors.
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Affiliation(s)
| | - Alvin Lu
- the Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, and the Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Darren L Brown
- the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Siew Wai Pang
- From the School of Chemistry and Molecular Biosciences and
| | | | - David P Sester
- From the School of Chemistry and Molecular Biosciences and
| | | | - Justine M Hill
- From the School of Chemistry and Molecular Biosciences and
| | - Kate Schroder
- the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jennifer L Stow
- the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Hao Wu
- the Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, and the Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Katryn J Stacey
- From the School of Chemistry and Molecular Biosciences and the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia,
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Sester DP, Thygesen SJ, Sagulenko V, Vajjhala PR, Cridland JA, Vitak N, Chen KW, Osborne GW, Schroder K, Stacey KJ. A Novel Flow Cytometric Method To Assess Inflammasome Formation. J I 2014; 194:455-62. [DOI: 10.4049/jimmunol.1401110] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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12
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Vajjhala PR, Kaiser S, Smith SJ, Ong QR, Soh SL, Stacey KJ, Hill JM. Identification of multifaceted binding modes for pyrin and ASC pyrin domains gives insights into pyrin inflammasome assembly. J Biol Chem 2014; 289:23504-19. [PMID: 25006247 DOI: 10.1074/jbc.m114.553305] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Inflammasomes are macromolecular complexes that mediate inflammatory and cell death responses to pathogens and cellular stress signals. Dysregulated inflammasome activation is associated with autoinflammatory syndromes and several common diseases. During inflammasome assembly, oligomerized cytosolic pattern recognition receptors recruit procaspase-1 and procaspase-8 via the adaptor protein ASC. Inflammasome assembly is mediated by pyrin domains (PYDs) and caspase recruitment domains, which are protein interaction domains of the death fold superfamily. However, the molecular details of their interactions are poorly understood. We have studied the interaction between ASC and pyrin PYDs that mediates ASC recruitment to the pyrin inflammasome, which is implicated in the pathogenesis of familial Mediterranean fever. We demonstrate that both the ASC and pyrin PYDs have multifaceted binding modes, involving three sites on pyrin PYD and two sites on ASC PYD. Molecular docking of pyrin-ASC PYD complexes showed that pyrin PYD can simultaneously interact with up to three ASC PYDs. Furthermore, ASC PYD can self-associate and interact with pyrin, consistent with previous reports that pyrin promotes ASC clustering to form a proinflammatory complex. Finally, the effects of familial Mediterranean fever-associated mutations, R42W and A89T, on structural and functional properties of pyrin PYD were investigated. The R42W mutation had a significant effect on structure and increased stability. Although the R42W mutant exhibited reduced interaction with ASC, it also bound less to the pyrin B-box domain responsible for autoinhibition and hence may be constitutively active. Our data give new insights into the binding modes of PYDs and inflammasome architecture.
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Affiliation(s)
| | | | - Sarah J Smith
- From the School of Chemistry and Molecular Biosciences and
| | - Qi-Rui Ong
- From the School of Chemistry and Molecular Biosciences and
| | | | | | - Justine M Hill
- From the School of Chemistry and Molecular Biosciences and Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland 4072, Australia
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13
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Chen KE, Richards AA, Caradoc-Davies TT, Vajjhala PR, Robin G, Lua LHL, Hill JM, Schroder K, Sweet MJ, Kellie S, Kobe B, Martin J. The structure of the caspase recruitment domain of BinCARD reveals that all three cysteines can be oxidized. Acta Crystallogr D Biol Crystallogr 2013; 69:774-84. [PMID: 23633586 DOI: 10.1107/s0907444913001558] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 01/16/2013] [Indexed: 11/10/2022]
Abstract
The caspase recruitment domain (CARD) is present in death-domain superfamily proteins involved in inflammation and apoptosis. BinCARD is named for its ability to interact with Bcl10 and inhibit downstream signalling. Human BinCARD is expressed as two isoforms that encode the same N-terminal CARD region but which differ considerably in their C-termini. Both isoforms are expressed in immune cells, although BinCARD-2 is much more highly expressed. Crystals of the CARD fold common to both had low symmetry (space group P1). Molecular replacement was unsuccessful in this low-symmetry space group and, as the construct contains no methionines, first one and then two residues were engineered to methionine for MAD phasing. The double-methionine variant was produced as a selenomethionine derivative, which was crystallized and the structure was solved using data measured at two wavelengths. The crystal structures of the native and selenomethionine double mutant were refined to high resolution (1.58 and 1.40 Å resolution, respectively), revealing the presence of a cis-peptide bond between Tyr39 and Pro40. Unexpectedly, the native crystal structure revealed that all three cysteines were oxidized. The mitochondrial localization of BinCARD-2 and the susceptibility of its CARD region to redox modification points to the intriguing possibility of a redox-regulatory role.
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Affiliation(s)
- Kai En Chen
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
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14
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Vajjhala PR, Mirams RE, Hill JM. Multiple binding sites on the pyrin domain of ASC protein allow self-association and interaction with NLRP3 protein. J Biol Chem 2012; 287:41732-43. [PMID: 23066025 DOI: 10.1074/jbc.m112.381228] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A key process underlying an innate immune response to pathogens or cellular stress is activation of members of the NOD-like receptor family, such as NLRP3, to assemble caspase-1-activating inflammasome complexes. Activated caspase-1 processes proinflammatory cytokines into active forms that mediate inflammation. Activation of the NLRP3 inflammasome is also associated with common diseases including cardiovascular disease, diabetes, chronic kidney disease, and Alzheimer disease. However, the molecular details of NLRP3 inflammasome assembly are not established. The adaptor protein ASC plays a key role in inflammasome assembly. It is composed of an N-terminal pyrin domain (PYD) and a C-terminal caspase recruitment domain, which are protein interaction domains of the death fold superfamily. ASC interacts with NLRP3 via a homotypic PYD interaction and recruits procaspase-1 via a homotypic caspase recruitment domain interaction. Here we demonstrate that ASC PYD contains two distinct binding sites important for self-association and interaction with NLRP3 and the modulatory protein POP1. Modeling of the homodimeric ASC PYD complex formed via an asymmetric interaction using both sites resembles a type I interaction found in other death fold domain complexes. This interaction mode also permits assembly of ASC PYDs into filaments. Furthermore, a type I binding mode is likely conserved in interactions with NLRP3 and POP1, because residues critical for interaction of ASC PYD are conserved in these PYDs. We also demonstrate that ASC PYD can simultaneously self-associate and interact with NLRP3, rationalizing the model whereby ASC self-association upon recruitment to NLRP3 promotes clustering and activation of procaspase-1.
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Affiliation(s)
- Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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15
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Vajjhala PR, Nguyen CH, Landsberg MJ, Kistler C, Gan AL, King GF, Hankamer B, Munn AL. The Vps4 C-terminal helix is a critical determinant for assembly and ATPase activity and has elements conserved in other members of the meiotic clade of AAA ATPases. FEBS J 2008; 275:1427-1449. [PMID: 18266866 DOI: 10.1111/j.1742-4658.2008.06300.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Sorting of membrane proteins into intralumenal endosomal vesicles, multivesicular body (MVB) sorting, is critical for receptor down regulation, antigen presentation and enveloped virus budding. Vps4 is an AAA ATPase that functions in MVB sorting. Although AAA ATPases are oligomeric, mechanisms that govern Vps4 oligomerization and activity remain elusive. Vps4 has an N-terminal microtubule interacting and trafficking domain required for endosome recruitment, an AAA domain containing the ATPase catalytic site and a beta domain, and a C-terminal alpha helix positioned close to the catalytic site in the 3D structure. Previous attempts to identify the role of the C-terminal helix have been unsuccessful. Here, we show that the C-terminal helix is important for Vps4 assembly and ATPase activity in vitro and function in vivo, but not endosome recruitment or interactions with Vta1 or ESCRT-III. Unlike the beta domain, which is also important for Vps4 assembly, the C-terminal helix is not required in vivo for Vps4 homotypic interaction or dominant-negative effects of Vps4-E233Q, carrying a mutation in the ATP hydrolysis site. Vta1 promotes assembly of hybrid complexes comprising Vps4-E233Q and Vps4 lacking an intact C-terminal helix in vitro. Formation of catalytically active hybrid complexes demonstrates an intersubunit catalytic mechanism for Vps4. One end of the C-terminal helix lies in close proximity to the second region of homology (SRH), which is important for assembly and intersubunit catalysis in AAA ATPases. We propose that Vps4 SRH function requires an intact C-terminal helix. Co-evolution of a distinct Vps4 SRH and C-terminal helix in meiotic clade AAA ATPases supports this possibility.
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Affiliation(s)
- Parimala R Vajjhala
- Institute for Molecular Bioscience, The University of Queensland, Australia., ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, Australia
| | - Chau H Nguyen
- Institute for Molecular Bioscience, The University of Queensland, Australia., ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, Australia
| | | | - Carol Kistler
- Institute for Molecular Bioscience, The University of Queensland, Australia., ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, Australia
| | - Ai-Lin Gan
- Institute for Molecular Bioscience, The University of Queensland, Australia., ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, Australia
| | - Ben Hankamer
- Institute for Molecular Bioscience, The University of Queensland, Australia
| | - Alan L Munn
- Institute for Molecular Bioscience, The University of Queensland, Australia., ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, Australia., School of Biomedical Sciences, The University of Queensland, Australia., School of Medical Science, Griffith University, Australia
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16
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Abstract
Vrp1p (verprolin, End5p) is the yeast ortholog of human Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP). Vrp1p localizes to the cortical actin cytoskeleton, is necessary for its polarization to sites of growth and is also essential for endocytosis. At elevated temperature, Vrp1p becomes essential for growth. A C-terminal Vrp1p fragment (C-Vrp1p) retains the ability to localize to the cortical actin cytoskeleton and function in actin-cytoskeleton polarization, endocytosis and growth. Here, we demonstrate that two submodules in C-Vrp1p are required for actin-cytoskeleton polarization: a novel C-terminal actin-binding submodule (CABS) that contains a novel G-actin-binding domain, which we call a verprolin homology 2 C-terminal (VH2-C) domain; and a second submodule comprising the Las17p-binding domain (LBD) that binds Las17p (yeast WASP). The LBD localizes C-Vrp1p to membranes and the cortical actin cytoskeleton. Intriguingly, the LBD is sufficient to restore endocytosis and growth at elevated temperature to Vrp1p-deficient cells. The CABS also restores these functions, but only if modified by a lipid anchor to provide membrane association. Our findings highlight the role of Las17p binding for Vrp1p membrane association, suggest general membrane association may be more important than specific targeting to the cortical actin cytoskeleton for Vrp1p function in endocytosis and cell growth, and suggest that Vrp1p binding to individual effectors may alter their physiological activity.
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Affiliation(s)
- Thirumaran Thanabalu
- Institute of Molecular and Cell Biology, A*STAR Biomedical Science Institutes, Singapore
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17
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Abstract
During endocytic transport, specific integral membrane proteins are sorted into intraluminal vesicles that bud from the limiting membrane of the endosome. This process, known as multivesicular body (MVB) sorting, is important for several important biological processes. Moreover, components of the MVB sorting machinery are implicated in virus budding. During MVB sorting, a cargo protein recruits components of the MVB sorting machinery from cytoplasmic pools and these sequentially assemble on the endosome. Disassembly of these proteins and recycling into the cytoplasm is critical for MVB sorting. Vacuolar protein sorting 4 (Vps4) is an AAA (ATPase associated with a variety of cellular activities) ATPase which has been proposed to play a critical role in disassembly of the MVB sorting machinery. However, the mechanism by which it disassembles the complex is not clear. Vps4 contains an N-terminal microtubule interacting and trafficking (MIT) domain, which has previously been shown to be required for recruitment to endosomes, and a single AAA ATPase domain, the activity of which is required for Vps4 function. In this study we have systematically characterized the interaction of Vps4 with other components of the MVB sorting machinery. We demonstrate that Vps4 interacts directly with Vps2 and Bro1. We also show that a subset of Vps4 interactions is regulated by ATP hydrolysis, and one interaction is regulated by ATP binding. Finally, we show that most proteins interact with the Vps4 MIT domain. Our studies indicate that the MIT domain has a dual role in substrate binding and recruitment to endosomes and indicate that Vps4 disassembles the MVB sorting machinery by direct effects on multiple proteins.
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Affiliation(s)
- Parimala R Vajjhala
- Institute for Molecular Bioscience and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, St Lucia, QLD, Australia
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18
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R Vajjhala P, L Munn A. Host factors in virus budding ? Insights from yeast. Microbiol Aust 2007. [DOI: 10.1071/ma07059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The budding yeast, Saccharomyces cerevisiae, is an excellentmodel organism for the study of eukaryotic cellular processes such as endocytosis 1. Like other eukaryotic cells, yeast take up extracellular material by invagination of the plasma membraneto form a vesicle. The internalised material is transported to a membrane-bound compartment, the early endosome. As the early endosome matures, internal vesicles form within the lumen giving it the appearance of a multivesicular body (vesicles enclosed by a membrane). The machinery required for endosome maturation is highly conserved between yeast and mammalian cells. In mammalian cells this machinery is also required for the budding of enveloped viruses. Here we discuss how studies of endosome maturation in S. cerevisiae have given valuable insights into the mechanism by which clinically important enveloped viruses, including human immunodeficiency virus (HIV) and hepatitis B virus, are released from mammalian cells.
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19
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Abstract
Endocytic and biosynthetic trafficking pathways to the lysosome/vacuole converge at the prevacuolar endosomal compartment. During transport through this compartment, integral membrane proteins that are destined for delivery to the lysosome/vacuole lumen undergo multivesicular body (MVB) sorting into internal vesicles formed by invagination of the endosomal limiting membrane. Vps4 is an AAA family ATPase which plays a key role in MVB sorting and facilitates transport through endosomes. It possesses an N-terminal microtubule interacting and trafficking domain required for recruitment to endosomes and an AAA domain with an ATPase catalytic site. The recently solved 3D structure revealed a beta domain, which protrudes from the AAA domain, and a final C-terminal alpha-helix. However, the in vivo roles of these domains are not known. In this study, we have identified motifs in these domains that are highly conserved between yeast and human Vps4. We have mutated these motifs and studied the effect on yeast Vps4p function in vivo and in vitro. We show that the beta domain of the budding yeast Vps4p is not required for recruitment to endosomes, but is essential for all Vps4p endocytic functions in vivo. We also show that the beta domain is required for Vps4p homotypic interaction and for full ATPase activity. In addition, it is required for interaction with Vta1p, which works in concert with Vps4p in vivo. Our studies suggest that assembly of a Vps4p oligomeric complex with full ATPase activity that interacts with Vta1p is essential for normal endosome function.
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Affiliation(s)
- Parimala R Vajjhala
- Institute for Molecular Bioscience and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, St Lucia, Queensland, Australia
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20
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Abstract
The Wilms' tumour suppressor gene (WT1) encodes a zinc finger-containing nuclear protein essential for kidney and urogenital development. Initially considered a transcription factor, there is mounting evidence that WT1 has a role in post-transcriptional processing. Using the interspecies heterokaryon assay, we have demonstrated that WT1 can undergo nucleocytoplasmic shuttling. We have also mapped the region responsible for nuclear export to residues 182-324. Our data add further complexity to the role of WT1 in transcriptional and post-transcriptional regulation.
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Affiliation(s)
- P R Vajjhala
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Qld 4072, Australia.
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