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Mnich K, Koryga I, Pakos-Zebrucka K, Thomas M, Logue SE, Eriksson LA, Gorman AM, Samali A. The stressosome, a caspase-8-activating signalling complex assembled in response to cell stress in an ATG5-mediated manner. J Cell Mol Med 2021; 25:8809-8820. [PMID: 34363313 PMCID: PMC8435408 DOI: 10.1111/jcmm.16840] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 11/29/2022] Open
Abstract
Stress-induced apoptosis is mediated primarily through the intrinsic pathway that involves caspase-9. We previously reported that in caspase-9-deficient cells, a protein complex containing ATG5 and Fas-associated death domain (FADD) facilitated caspase-8 activation and cell death in response to endoplasmic reticulum (ER) stress. Here, we investigated whether this complex could be activated by other forms of cell stress. We show that diverse stress stimuli, including etoposide, brefeldin A and paclitaxel, as well as heat stress and gamma-irradiation, caused formation of a complex containing ATG5-ATG12, FADD and caspase-8 leading to activation of downstream caspases in caspase-9-deficient cells. We termed this complex the 'stressosome'. However, in these cells, only ER stress and heat shock led to stressosome-dependent cell death. Using in silico molecular modelling, we propose the structure of the stressosome complex, with FADD acting as an adaptor protein, interacting with pro-caspase-8 through their respective death effector domains (DEDs) and interacting with ATG5-ATG12 through its death domain (DD). This suggests that the complex could be regulated by cellular FADD-like interleukin-1β-converting enzyme-inhibitory protein (cFLIPL ), which was confirmed experimentally. This study provides strong evidence for an alternative mechanism of caspase-8 activation involving the stressosome complex.
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Affiliation(s)
- Katarzyna Mnich
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,CÚRAM SFI Research Centre for Medical Devices, NUI Galway, Galway, Ireland
| | - Izabela Koryga
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,CÚRAM SFI Research Centre for Medical Devices, NUI Galway, Galway, Ireland
| | - Karolina Pakos-Zebrucka
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,CÚRAM SFI Research Centre for Medical Devices, NUI Galway, Galway, Ireland
| | - Melissa Thomas
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Susan E Logue
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB, Canada.,Research Institute in Oncology and Hematology, Cancer Care Manitoba, Winnipeg, MB, Canada
| | - Leif A Eriksson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Adrienne M Gorman
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,CÚRAM SFI Research Centre for Medical Devices, NUI Galway, Galway, Ireland
| | - Afshin Samali
- Apoptosis Research Centre, NUI Galway, Galway, Ireland.,School of Natural Sciences, NUI Galway, Galway, Ireland.,CÚRAM SFI Research Centre for Medical Devices, NUI Galway, Galway, Ireland
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Lystad AH, Simonsen A. Mechanisms and Pathophysiological Roles of the ATG8 Conjugation Machinery. Cells 2019; 8:E973. [PMID: 31450711 PMCID: PMC6769624 DOI: 10.3390/cells8090973] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 08/19/2019] [Accepted: 08/20/2019] [Indexed: 12/18/2022] Open
Abstract
Since their initial discovery around two decades ago, the yeast autophagy-related (Atg)8 protein and its mammalian homologues of the light chain 3 (LC3) and γ-aminobutyric acid receptor associated proteins (GABARAP) families have been key for the tremendous expansion of our knowledge about autophagy, a process in which cytoplasmic material become targeted for lysosomal degradation. These proteins are ubiquitin-like proteins that become directly conjugated to a lipid in the autophagy membrane upon induction of autophagy, thus providing a marker of the pathway, allowing studies of autophagosome biogenesis and maturation. Moreover, the ATG8 proteins function to recruit components of the core autophagy machinery as well as cargo for selective degradation. Importantly, comprehensive structural and biochemical in vitro studies of the machinery required for ATG8 protein lipidation, as well as their genetic manipulation in various model organisms, have provided novel insight into the molecular mechanisms and pathophysiological roles of the mATG8 proteins. Recently, it has become evident that the ATG8 proteins and their conjugation machinery are also involved in intracellular pathways and processes not related to autophagy. This review focuses on the molecular functions of ATG8 proteins and their conjugation machinery in autophagy and other pathways, as well as their links to disease.
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Affiliation(s)
- Alf Håkon Lystad
- Department of Molecular Medicine, Institute of Basic Medical Sciences and Centre for Cancer Cell Reprogramming, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, 1112 Blindern, 0317 Oslo, Norway.
| | - Anne Simonsen
- Department of Molecular Medicine, Institute of Basic Medical Sciences and Centre for Cancer Cell Reprogramming, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, 1112 Blindern, 0317 Oslo, Norway.
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