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Johnson L, Sarosiek KA. Role of intrinsic apoptosis in environmental exposure health outcomes. Trends Mol Med 2024; 30:56-73. [PMID: 38057226 DOI: 10.1016/j.molmed.2023.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/31/2023] [Accepted: 11/06/2023] [Indexed: 12/08/2023]
Abstract
Environmental exposures are linked to diseases of high public health concern, including cancer, neurodegenerative disorders, and autoimmunity. These diseases are caused by excessive or insufficient cell death, prompting investigation of mechanistic links between environmental toxicants and dysregulation of cell death pathways, including apoptosis. This review describes how legacy and emerging environmental exposures target the intrinsic apoptosis pathway to potentially drive pathogenesis. Recent discoveries reveal that dynamic regulation of apoptosis may heighten the vulnerability of healthy tissues to exposures in children, and that apoptotic signaling can guide immune responses, tissue repair, and tumorigenesis. Understanding how environmental toxicants dysregulate apoptosis will uncover opportunities to deploy apoptosis-modulating agents for the treatment or prevention of exposure-linked diseases.
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Affiliation(s)
- Lissah Johnson
- John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Molecular and Integrative Physiological Sciences Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Laboratory for Systems Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Kristopher A Sarosiek
- John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Molecular and Integrative Physiological Sciences Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Laboratory for Systems Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Department of Medical Oncology, Dana-Farber Cancer Institute/Harvard Cancer Center, Boston, MA, USA.
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Czabotar PE, Garcia-Saez AJ. Mechanisms of BCL-2 family proteins in mitochondrial apoptosis. Nat Rev Mol Cell Biol 2023; 24:732-748. [PMID: 37438560 DOI: 10.1038/s41580-023-00629-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2023] [Indexed: 07/14/2023]
Abstract
The proteins of the BCL-2 family are key regulators of mitochondrial apoptosis, acting as either promoters or inhibitors of cell death. The functional interplay and balance between the opposing BCL-2 family members control permeabilization of the outer mitochondrial membrane, leading to the release of activators of the caspase cascade into the cytosol and ultimately resulting in cell death. Despite considerable research, our knowledge about the mechanisms of the BCL-2 family of proteins remains insufficient, which complicates cell fate predictions and does not allow us to fully exploit these proteins as targets for drug discovery. Detailed understanding of the formation and molecular architecture of the apoptotic pore in the outer mitochondrial membrane remains a holy grail in the field, but new studies allow us to begin constructing a structural model of its arrangement. Recent literature has also revealed unexpected activities for several BCL-2 family members that challenge established concepts of how they regulate mitochondrial permeabilization. In this Review, we revisit the most important advances in the field and integrate them into a new structure-function-based classification of the BCL-2 family members that intends to provide a comprehensive model for BCL-2 action in apoptosis. We close this Review by discussing the potential of drugging the BCL-2 family in diseases characterized by aberrant apoptosis.
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Affiliation(s)
- Peter E Czabotar
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia.
- Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia.
| | - Ana J Garcia-Saez
- Membrane Biophysics, Institute of Genetics, CECAD, University of Cologne, Cologne, Germany.
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Flores-Romero H, Dadsena S, García-Sáez AJ. Mitochondrial pores at the crossroad between cell death and inflammatory signaling. Mol Cell 2023; 83:843-856. [PMID: 36931255 DOI: 10.1016/j.molcel.2023.02.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 02/13/2023] [Accepted: 02/16/2023] [Indexed: 03/18/2023]
Abstract
Mitochondria are cellular organelles with a major role in many cellular processes, including not only energy production, metabolism, and calcium homeostasis but also regulated cell death and innate immunity. Their proteobacterial origin makes them a rich source of potent immune agonists, normally hidden within the mitochondrial membrane barriers. Alteration of mitochondrial permeability through mitochondrial pores thus provides efficient mechanisms not only to communicate mitochondrial stress to the cell but also as a key event in the integration of cellular responses. In this regard, eukaryotic cells have developed diverse signaling networks that sense and respond to the release of mitochondrial components into the cytosol and play a key role in controlling cell death and inflammatory pathways. Modulating pore formation at mitochondria through direct or indirect mechanisms may thus open new opportunities for therapy. In this review, we discuss the current understanding of the structure and molecular mechanisms of mitochondrial pores and how they function at the interface between cell death and inflammatory signaling to regulate cellular outcomes.
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Affiliation(s)
- Hector Flores-Romero
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne, Germany
| | - Shashank Dadsena
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne, Germany
| | - Ana J García-Sáez
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne, Germany.
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Aguilar F, Yu S, Grant RA, Swanson S, Ghose D, Su BG, Sarosiek KA, Keating AE. Peptides from human BNIP5 and PXT1 and non-native binders of pro-apoptotic BAK can directly activate or inhibit BAK-mediated membrane permeabilization. Structure 2023; 31:265-281.e7. [PMID: 36706751 PMCID: PMC9992319 DOI: 10.1016/j.str.2023.01.001] [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: 08/30/2022] [Revised: 11/24/2022] [Accepted: 01/02/2023] [Indexed: 01/27/2023]
Abstract
Apoptosis is important for development and tissue homeostasis, and its dysregulation can lead to diseases, including cancer. As an apoptotic effector, BAK undergoes conformational changes that promote mitochondrial outer membrane disruption, leading to cell death. This is termed "activation" and can be induced by peptides from the human proteins BID, BIM, and PUMA. To identify additional peptides that can regulate BAK, we used computational protein design, yeast surface display screening, and structure-based energy scoring to identify 10 diverse new binders. We discovered peptides from the human proteins BNIP5 and PXT1 and three non-native peptides that activate BAK in liposome assays and induce cytochrome c release from mitochondria. Crystal structures and binding studies reveal a high degree of similarity among peptide activators and inhibitors, ruling out a simple function-determining property. Our results shed light on the vast peptide sequence space that can regulate BAK function and will guide the design of BAK-modulating tools and therapeutics.
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Affiliation(s)
- Fiona Aguilar
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Stacey Yu
- Laboratory of Systems Pharmacology, Harvard Program in Therapeutic Science, Department of Systems Biology, Harvard Medical School, Boston, MA, USA; Program in Molecular and Integrative Physiological Sciences Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA; John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Robert A Grant
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Sebastian Swanson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Dia Ghose
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Bonnie G Su
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kristopher A Sarosiek
- Laboratory of Systems Pharmacology, Harvard Program in Therapeutic Science, Department of Systems Biology, Harvard Medical School, Boston, MA, USA; Program in Molecular and Integrative Physiological Sciences Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA; John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Amy E Keating
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA; Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
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Moldoveanu T. Apoptotic mitochondrial poration by a growing list of pore-forming BCL-2 family proteins. Bioessays 2023; 45:e2200221. [PMID: 36650950 PMCID: PMC9975053 DOI: 10.1002/bies.202200221] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/31/2022] [Accepted: 01/02/2023] [Indexed: 01/19/2023]
Abstract
The pore-forming BCL-2 family proteins are effectors of mitochondrial poration in apoptosis initiation. Two atypical effectors-BOK and truncated BID (tBID)-join the canonical effectors BAK and BAX. Gene knockout revealed developmental phenotypes in the absence the effectors, supporting their roles in vivo. During apoptosis effectors are activated and change shape from dormant monomers to dynamic oligomers that associate with and permeabilize mitochondria. BID is activated by proteolysis, BOK accumulates on inhibition of its degradation by the E3 ligase gp78, while BAK and BAX undergo direct activation by BH3-only initiators, autoactivation, and crossactivation. Except tBID, effector oligomers on the mitochondria appear as arcs and rings in super-resolution microscopy images. The BH3-in-groove dimers of BAK and BAX, the tBID monomers, and uncharacterized BOK species are the putative building blocks of apoptotic pores. Effectors interact with lipids and bilayers but the mechanism of membrane poration remains elusive. I discuss effector-mediated mitochondrial poration.
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Affiliation(s)
- Tudor Moldoveanu
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences,Correspondence:
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