1801
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Takeda K, Naguro I, Nishitoh H, Matsuzawa A, Ichijo H. Apoptosis signaling kinases: from stress response to health outcomes. Antioxid Redox Signal 2011; 15:719-61. [PMID: 20969480 DOI: 10.1089/ars.2010.3392] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Apoptosis is a highly regulated process essential for the development and homeostasis of multicellular organisms. Whereas caspases, a large family of intracellular cysteine proteases, play central roles in the execution of apoptosis, other proapoptotic and antiapoptotic regulators such as the members of the Bcl-2 family are also critically involved in the regulation of apoptosis. A large body of evidence has revealed that a number of protein kinases are among such regulators and regulate cellular sensitivity to various proapoptotic signals at multiple steps in apoptosis. However, recent progress in the analysis of these apoptosis signaling kinases demonstrates that they generally act as crucial regulators of diverse cellular responses to a wide variety of stressors, beyond their roles in apoptosis regulation. In this review, we have cataloged apoptosis signaling kinases involved in cellular stress responses on the basis of their ability to induce apoptosis and discuss their roles in stress responses with particular emphasis on health outcomes upon their dysregulation.
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Affiliation(s)
- Kohsuke Takeda
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, Strategic Approach to Drug Discovery and Development in Pharmaceutical Sciences, Global Center of Excellence Program and Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, The University of Tokyo, Tokyo, Japan.
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1802
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FADD prevents RIP3-mediated epithelial cell necrosis and chronic intestinal inflammation. Nature 2011; 477:330-4. [PMID: 21804564 DOI: 10.1038/nature10273] [Citation(s) in RCA: 568] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 06/06/2011] [Indexed: 12/23/2022]
Abstract
Intestinal immune homeostasis depends on a tightly regulated cross talk between commensal bacteria, mucosal immune cells and intestinal epithelial cells (IECs). Epithelial barrier disruption is considered to be a potential cause of inflammatory bowel disease; however, the mechanisms regulating intestinal epithelial integrity are poorly understood. Here we show that mice with IEC-specific knockout of FADD (FADD(IEC-KO)), an adaptor protein required for death-receptor-induced apoptosis, spontaneously developed epithelial cell necrosis, loss of Paneth cells, enteritis and severe erosive colitis. Genetic deficiency in RIP3, a critical regulator of programmed necrosis, prevented the development of spontaneous pathology in both the small intestine and colon of FADD(IEC-KO) mice, demonstrating that intestinal inflammation is triggered by RIP3-dependent death of FADD-deficient IECs. Epithelial-specific inhibition of CYLD, a deubiquitinase that regulates cellular necrosis, prevented colitis development in FADD(IEC-KO) but not in NEMO(IEC-KO) mice, showing that different mechanisms mediated death of colonic epithelial cells in these two models. In FADD(IEC-KO) mice, TNF deficiency ameliorated colon inflammation, whereas MYD88 deficiency and also elimination of the microbiota prevented colon inflammation, indicating that bacteria-mediated Toll-like-receptor signalling drives colitis by inducing the expression of TNF and other cytokines. However, neither CYLD, TNF or MYD88 deficiency nor elimination of the microbiota could prevent Paneth cell loss and enteritis in FADD(IEC-KO) mice, showing that different mechanisms drive RIP3-dependent necrosis of FADD-deficient IECs in the small and large bowel. Therefore, by inhibiting RIP3-mediated IEC necrosis, FADD preserves epithelial barrier integrity and antibacterial defence, maintains homeostasis and prevents chronic intestinal inflammation. Collectively, these results show that mechanisms preventing RIP3-mediated epithelial cell death are critical for the maintenance of intestinal homeostasis and indicate that programmed necrosis of IECs might be implicated in the pathogenesis of inflammatory bowel disease, in which Paneth cell and barrier defects are thought to contribute to intestinal inflammation.
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1803
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Dunai Z, Bauer PI, Mihalik R. Necroptosis: biochemical, physiological and pathological aspects. Pathol Oncol Res 2011; 17:791-800. [PMID: 21773880 DOI: 10.1007/s12253-011-9433-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 06/24/2011] [Indexed: 11/27/2022]
Abstract
Programmed cell death is a key component of tissue homeostasis, normal development and wide variety of diseases. Conventional view refers to programmed cell death form as caspase-mediated apoptosis while necrosis is considered as an accidental and unwanted cell demise, carried out in a non-regulated manner and caused by extreme conditions. However, accumulating evidences indicate that necrotic cell death can also be a regulated process. The term necroptosis has been introduced to describe a cell death receptor-induced, caspase-independent, highly regulated type of programmed cell death process with morphological resemblance of necrosis. Necroptosis recently has been found to contribute to a wide range of pathologic cell death forms including ischemic brain injury, neurodegenerative diseases and viral infection, therefore a better understanding of the necroptotic signaling machinery has clinical relevance.
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Affiliation(s)
- Zsuzsanna Dunai
- Department of Pathogenetics, National Institute of Oncology, Ráth György street 7-9, Budapest H-1122, Hungary.
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1804
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Abstract
NF-κB transcription factors are critical regulators of immunity, stress responses, apoptosis and differentiation. A variety of stimuli coalesce on NF-κB activation, which can in turn mediate varied transcriptional programs. Consequently, NF-κB-dependent transcription is not only tightly controlled by positive and negative regulatory mechanisms but also closely coordinated with other signaling pathways. This intricate crosstalk is crucial to shaping the diverse biological functions of NF-κB into cell type- and context-specific responses.
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1805
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Requirement of FADD, NEMO, and BAX/BAK for aberrant mitochondrial function in tumor necrosis factor alpha-induced necrosis. Mol Cell Biol 2011; 31:3745-58. [PMID: 21746883 DOI: 10.1128/mcb.05303-11] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Necroptosis represents a form of alternative programmed cell death that is dependent on the kinase RIP1. RIP1-dependent necroptotic death manifests as increased reactive oxygen species (ROS) production in mitochondria and is accompanied by loss of ATP biogenesis and eventual dissipation of mitochondrial membrane potential. Here, we show that tumor necrosis factor alpha (TNF-α)-induced necroptosis requires the adaptor proteins FADD and NEMO. FADD was found to mediate formation of the TNF-α-induced pronecrotic RIP1-RIP3 kinase complex, whereas the IκB Kinase (IKK) subunit NEMO appears to function downstream of RIP1-RIP3. Interestingly, loss of RelA potentiated TNF-α-dependent necroptosis, indicating that NEMO regulates necroptosis independently of NF-κB. Using both pharmacologic and genetic approaches, we demonstrate that the overexpression of antioxidants alleviates ROS elevation and necroptosis. Finally, elimination of BAX and BAK or overexpression of Bcl-x(L) protects cells from necroptosis at a later step. These findings provide evidence that mitochondria play an amplifying role in inflammation-induced necroptosis.
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1806
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Tenev T, Bianchi K, Darding M, Broemer M, Langlais C, Wallberg F, Zachariou A, Lopez J, MacFarlane M, Cain K, Meier P. The Ripoptosome, a signaling platform that assembles in response to genotoxic stress and loss of IAPs. Mol Cell 2011; 43:432-48. [PMID: 21737329 DOI: 10.1016/j.molcel.2011.06.006] [Citation(s) in RCA: 729] [Impact Index Per Article: 56.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 05/16/2011] [Accepted: 06/08/2011] [Indexed: 10/18/2022]
Abstract
A better understanding of the mechanisms through which anticancer drugs exert their effects is essential to improve combination therapies. While studying how genotoxic stress kills cancer cells, we discovered a large ∼2MDa cell death-inducing platform, referred to as "Ripoptosome." It contains the core components RIP1, FADD, and caspase-8, and assembles in response to genotoxic stress-induced depletion of XIAP, cIAP1 and cIAP2. Importantly, it forms independently of TNF, CD95L/FASL, TRAIL, death-receptors, and mitochondrial pathways. It also forms upon Smac-mimetic (SM) treatment without involvement of autocrine TNF. Ripoptosome assembly requires RIP1's kinase activity and can stimulate caspase-8-mediated apoptosis as well as caspase-independent necrosis. It is negatively regulated by FLIP, cIAP1, cIAP2, and XIAP. Mechanistically, IAPs target components of this complex for ubiquitylation and inactivation. Moreover, we find that etoposide-stimulated Ripoptosome formation converts proinflammatory cytokines into prodeath signals. Together, our observations shed new light on fundamental mechanisms by which chemotherapeutics may kill cancer cells.
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Affiliation(s)
- Tencho Tenev
- The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
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1807
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Feoktistova M, Geserick P, Kellert B, Dimitrova DP, Langlais C, Hupe M, Cain K, MacFarlane M, Häcker G, Leverkus M. cIAPs block Ripoptosome formation, a RIP1/caspase-8 containing intracellular cell death complex differentially regulated by cFLIP isoforms. Mol Cell 2011; 43:449-63. [PMID: 21737330 PMCID: PMC3163271 DOI: 10.1016/j.molcel.2011.06.011] [Citation(s) in RCA: 774] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 03/20/2011] [Accepted: 06/17/2011] [Indexed: 11/25/2022]
Abstract
The intracellular regulation of cell death pathways by cIAPs has been enigmatic. Here we show that loss of cIAPs promotes the spontaneous formation of an intracellular platform that activates either apoptosis or necroptosis. This 2 MDa intracellular complex that we designate “Ripoptosome” is necessary but not sufficient for cell death. It contains RIP1, FADD, caspase-8, caspase-10, and caspase inhibitor cFLIP isoforms. cFLIPL prevents Ripoptosome formation, whereas, intriguingly, cFLIPS promotes Ripoptosome assembly. When cIAPs are absent, caspase activity is the “rheostat” that is controlled by cFLIP isoforms in the Ripoptosome and decides if cell death occurs by RIP3-dependent necroptosis or caspase-dependent apoptosis. RIP1 is the core component of the complex. As exemplified by our studies for TLR3 activation, our data argue that the Ripoptosome critically influences the outcome of membrane-bound receptor triggering. The differential quality of cell death mediated by the Ripoptosome may cause important pathophysiological consequences during inflammatory responses.
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Affiliation(s)
- Maria Feoktistova
- Department of Dermatology, Venereology, and Allergology, Medical Faculty Mannheim, University Heidelberg, Heidelberg, Germany
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1808
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Discrimination between primary necrosis and apoptosis by necrostatin-1 in Annexin V-positive/propidium iodide-negative cells. Biochem Biophys Res Commun 2011; 411:569-73. [PMID: 21763280 DOI: 10.1016/j.bbrc.2011.06.186] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 06/30/2011] [Indexed: 11/24/2022]
Abstract
Apoptotic cell death eventually results in secondary necrotic cell death, whereas caspase-independent primary necrotic cell death has been reported and its mechanism involving RIP1 and RIP3 has been recently elucidated. Dual staining with fluorescent Annexin V and propidium iodide (PI) has been used to discriminate apoptotic and necrotic cell death, in which Annexin V-positive/PI-negative staining is regarded as apoptosis and PI-positive staining as necrosis. Here we demonstrate that primary necrotic cells unexpectedly show Annexin V-positive/PI-negative staining before they become PI-positive, and that primary necrotic and apoptotic Annexin V-positive/PI-negative cells can be discriminated by necrostatin-1, an inhibitor of primary necrosis by inhibition of RIP1.
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1809
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van Raam BJ, Salvesen GS. Proliferative versus apoptotic functions of caspase-8 Hetero or homo: the caspase-8 dimer controls cell fate. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:113-22. [PMID: 21704196 DOI: 10.1016/j.bbapap.2011.06.005] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Revised: 06/06/2011] [Accepted: 06/08/2011] [Indexed: 12/12/2022]
Abstract
Caspase-8, the initiator of extrinsically-triggered apoptosis, also has important functions in cellular activation and differentiation downstream of a variety of cell surface receptors. It has become increasingly clear that the heterodimer of caspase-8 with the long isoform of cellular FLIP (FLIP(L)) fulfills these pro-survival functions of caspase-8. FLIP(L), a catalytically defective caspase-8 paralog, can interact with caspase-8 to activate its catalytic function. The caspase-8/FLIP(L) heterodimer has a restricted substrate repertoire and does not induce apoptosis. In essence, caspase-8 heterodimerized with FLIP(L) prevents the receptor interacting kinases RIPK1 and -3 from executing the form of cell death known as necroptosis. This review discusses the latest insights in caspase-8 homo- versus heterodimerization and the implication this has for cellular death or survival. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.
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Affiliation(s)
- Bram J van Raam
- Program of Apoptosis and Cell Death Research, Sanford-Burnham Institute, La Jolla, CA 92037, USA.
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1810
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Abstract
It is well known that apoptosis is an actively mediated cell suicide process. In contrast, necrosis, a morphologically distinct form of cell death, has traditionally been regarded as passive and unregulated. Over the past decade, however, experiments in Caenorhabditis elegans and mammalian cells have revealed that a significant proportion of necrotic death is, in fact, actively mediated by the doomed cell. Although a comprehensive understanding of necrosis is still lacking, some key molecular events have come into focus. Cardiac myocyte apoptosis and necrosis are prominent features of the major cardiac syndromes. Accordingly, the recognition of necrosis as a regulated process mandates a reexamination of cell death in the heart. This review discusses pathways that mediate programmed necrosis, how they intersect with apoptotic pathways, roles of necrosis in heart disease, and new therapeutic opportunities that the regulated nature of necrosis presents.
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Affiliation(s)
- Gloria Kung
- Wilf Family Cardiovascular Research Institute, Departments of Medicine and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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1811
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Germain RN, Meier-Schellersheim M, Nita-Lazar A, Fraser IDC. Systems biology in immunology: a computational modeling perspective. Annu Rev Immunol 2011; 29:527-85. [PMID: 21219182 DOI: 10.1146/annurev-immunol-030409-101317] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Systems biology is an emerging discipline that combines high-content, multiplexed measurements with informatic and computational modeling methods to better understand biological function at various scales. Here we present a detailed review of the methods used to create computational models and to conduct simulations of immune function. We provide descriptions of the key data-gathering techniques employed to generate the quantitative and qualitative data required for such modeling and simulation and summarize the progress to date in applying these tools and techniques to questions of immunological interest, including infectious disease. We include comments on what insights modeling can provide that complement information obtained from the more familiar experimental discovery methods used by most investigators and the reasons why quantitative methods are needed to eventually produce a better understanding of immune system operation in health and disease.
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Affiliation(s)
- Ronald N Germain
- Program in Systems Immunology and Infectious Disease Modeling, National Institute of Allergy and Infectious Disease, Laboratory of Immunology, National Institutes of Health, Bethesda, Maryland 20892, USA.
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1812
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Ascorbate promotes carbon tetrachloride-induced hepatic injury in senescence marker protein 30-deficient mice by enhancing inflammation. J Nutr Biochem 2011; 22:535-42. [DOI: 10.1016/j.jnutbio.2010.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 04/07/2010] [Accepted: 04/12/2010] [Indexed: 01/24/2023]
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1813
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Biton S, Ashkenazi A. NEMO and RIP1 control cell fate in response to extensive DNA damage via TNF-α feedforward signaling. Cell 2011; 145:92-103. [PMID: 21458669 DOI: 10.1016/j.cell.2011.02.023] [Citation(s) in RCA: 307] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 01/21/2011] [Accepted: 02/04/2011] [Indexed: 11/30/2022]
Abstract
Upon DNA damage, ataxia telangiectasia mutated (ATM) kinase triggers multiple events to promote cell survival and facilitate repair. If damage is excessive, ATM stimulates cytokine secretion to alert neighboring cells and apoptosis to eliminate the afflicted cell. ATM augments cell survival by activating nuclear factor (NF)-κB; however, how ATM induces cytokine production and apoptosis remains elusive. Here we uncover a p53-independent mechanism that transmits ATM-driven cytokine and caspase signals upon strong genotoxic damage. Extensive DNA lesions stimulated two sequential NF-κB activation phases, requiring ATM and NEMO/IKK-γ: The first phase induced TNF-α-TNFR1 feedforward signaling, promoting the second phase and driving RIP1 phosphorylation. In turn, RIP1 kinase triggered JNK3/MAPK10-dependent interleukin-8 secretion and FADD-mediated proapoptotic caspase-8 activation. Thus, in the context of excessive DNA damage, ATM employs NEMO and RIP1 kinase through autocrine TNF-α signaling to switch on cytokine production and caspase activation. These results shed light on cell-fate regulation by ATM.
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Affiliation(s)
- Sharon Biton
- Department of Molecular Oncology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
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1814
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NF-kappaB protects cells from gamma interferon-induced RIP1-dependent necroptosis. Mol Cell Biol 2011; 31:2934-46. [PMID: 21576359 DOI: 10.1128/mcb.05445-11] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Interferons (IFNs) are cytokines with well-described immunomodulatory and antiviral properties, but less is known about the mechanisms by which they promote cell survival or cell death. Here, we show that IFN-γ induces RIP1 kinase-dependent necroptosis in mammalian cells deficient in NF-κB signaling. Induction of necroptosis by IFN-γ was found to depend on Jak1 and partially on STAT1. We also demonstrate that IFN-γ activates IκB kinase β (IKKβ)-dependent NF-κB to regulate a transcriptional program that protects cells from necroptosis. IFN-γ induced progressive accumulation of reactive oxygen species (ROS) and eventual loss of mitochondrial membrane potential in cells lacking the NF-κB subunit RelA. Whole-genome microarray analyses identified sod2, encoding the antioxidant enzyme manganese superoxide dismutase (MnSOD), as a RelA target and potential antinecroptotic gene. Overexpression of MnSOD inhibited IFN-γ-mediated ROS accumulation and partially rescued RelA-deficient cells from necroptosis, while RNA interference (RNAi)-mediated silencing of sod2 expression increased susceptibility to IFN-γ-induced cell death. Together, these studies demonstrate that NF-κB protects cells from IFN-γ-mediated necroptosis by transcriptionally activating a survival response that quenches ROS to preserve mitochondrial integrity.
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1815
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Galluzzi L, Vitale I, Vacchelli E, Kroemer G. Cell death signaling and anticancer therapy. Front Oncol 2011; 1:5. [PMID: 22655227 PMCID: PMC3356092 DOI: 10.3389/fonc.2011.00005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 04/21/2011] [Indexed: 12/22/2022] Open
Abstract
For a long time, it was commonly believed that efficient anticancer regimens would either trigger the apoptotic demise of tumor cells or induce a permanent arrest in the G1 phase of the cell cycle, i.e., senescence. The recent discovery that necrosis can occur in a regulated fashion and the increasingly more precise characterization of the underlying molecular mechanisms have raised great interest, as non-apoptotic pathways might be instrumental to circumvent the resistance of cancer cells to conventional, pro-apoptotic therapeutic regimens. Moreover, it has been shown that some anticancer regimens engage lethal signaling cascades that can ignite multiple oncosuppressive mechanisms, including apoptosis, necrosis, and senescence. Among these signaling pathways is mitotic catastrophe, whose role as a bona fide cell death mechanism has recently been reconsidered. Thus, anticancer regimens get ever more sophisticated, and often distinct strategies are combined to maximize efficacy and minimize side effects. In this review, we will discuss the importance of apoptosis, necrosis, and mitotic catastrophe in the response of tumor cells to the most common clinically employed and experimental anticancer agents.
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1816
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Apoptosis is an innate defense function of macrophages against Mycobacterium tuberculosis. Mucosal Immunol 2011; 4:279-87. [PMID: 21307848 PMCID: PMC3155700 DOI: 10.1038/mi.2011.3] [Citation(s) in RCA: 306] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Two different forms of death are commonly observed when Mycobacterium tuberculosis (Mtb)-infected macrophages die: (i) necrosis, a death modality defined by cell lysis and (ii) apoptosis, a form of death that maintains an intact plasma membrane. Necrosis is a mechanism used by bacteria to exit the macrophage, evade host defenses, and spread. In contrast, apoptosis of infected macrophages is associated with diminished pathogen viability. Apoptosis occurs when tumor necrosis factor activates the extrinsic death domain pathway, leading to caspase-8 activation. In addition, mitochondrial outer membrane permeabilization leading to activation of the intrinsic apoptotic pathway is required. Both pathways lead to caspase-3 activation, which results in apoptosis. We have recently demonstrated that during mycobacterial infection, cell death is regulated by the eicosanoids, prostaglandin E(2) (proapoptotic) and lipoxin (LX)A(4) (pronecrotic). Although PGE(2) protects against necrosis, virulent Mtb induces LXA(4) and inhibits PGE(2) production. Under such conditions, mitochondrial inner membrane damage leads to macrophage necrosis. Thus, virulent Mtb subverts eicosanoid regulation of cell death to foil innate defense mechanisms of the macrophage.
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1817
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Ikner A, Ashkenazi A. TWEAK induces apoptosis through a death-signaling complex comprising receptor-interacting protein 1 (RIP1), Fas-associated death domain (FADD), and caspase-8. J Biol Chem 2011; 286:21546-54. [PMID: 21525013 DOI: 10.1074/jbc.m110.203745] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The tumor necrosis factor (TNF) superfamily member TNF-like weak inducer of apoptosis (TNFSF12, CD255) (TWEAK) can stimulate apoptosis in certain cancer cells. Previous studies suggest that TWEAK activates cell death indirectly, by inducing TNFα-mediated autocrine signals. However, the underlying death-signaling mechanism has not been directly defined. Consistent with earlier work, TWEAK assembled a proximal signaling complex containing its cognate receptor FN14, the adaptor TRAF2, and cellular inhibitor of apoptosis protein 1 (cIAP1). Neither the death domain adaptor Fas-associated death domain nor the apoptosis-initiating protease caspase-8 associated with this primary complex. Rather, TWEAK induced TNFα secretion and TNF receptor 1-dependent assembly of a death-signaling complex containing receptor-interacting protein 1 (RIP1), FADD, and caspase-8. Knockdown of RIP1 by siRNA prevented TWEAK-induced association of FADD with caspase-8 but not formation of the FN14-TRAF2-cIAP1 complex and inhibited apoptosis activation. Depletion of the RIP1 E3 ubiquitin ligase cIAP1 enhanced assembly of the RIP1-FADD-caspase-8 complex and augmented cell death. Conversely, knockdown of the RIP1 deubiquitinase CYLD inhibited these functions. Depletion of FADD, caspase-8, BID, or BAX and BAK but not RIP3 attenuated TWEAK-induced cell death. Pharmacologic inhibition of the NF-κB pathway or siRNA knockdown of RelA attenuated TWEAK induction of TNFα and association of RIP1 with FADD and caspase-8. These results suggest that TWEAK triggers apoptosis by promoting assembly of a RIP1-FADD-caspse-8 complex via autocrine TNFα-TNFR1 signaling. The proapoptotic activity of TWEAK is modulated by cIAP1 and CYLD and engages both the extrinsic and intrinsic signaling pathways.
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Affiliation(s)
- Aminah Ikner
- Department of Molecular Oncology, Genentech, South San Francisco, California 94080, USA
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1818
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Ono K, Wang X, Kim SO, Armstrong LC, Bornstein P, Han J. Metaxin deficiency alters mitochondrial membrane permeability and leads to resistance to TNF-induced cell killing. Protein Cell 2011; 1:161-73. [PMID: 21088703 DOI: 10.1007/s13238-010-0017-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Metaxin, a mitochondrial outer membrane protein, is critical for TNF-induced cell death in L929 cells. Its deficiency, caused by retroviral insertion-mediated mutagenesis, renders L929 cells resistance to TNF killing. In this study, we further characterized metaxin deficiency-caused TNF resistance in parallel with Bcl-X(L) overexpression-mediated death resistance. We did not find obvious change in mitochondria membrane potential in metaxin-deficient (Met(mut)) and Bcl-X(L)-overexpressing cells, but we did find an increase in the release rate of the mitochondrial membrane potential probe rhodamine 123 (Rh123) that was preloaded into mitochondria. In addition, overexpression of a function-interfering mutant of metaxin (MetaΔTM/C) or Bcl-X(L) in MCF-7.3.28 cells also resulted in an acquired resistance to TNF killing and a faster rate of Rh123 release, indicating a close correlation between TNF resistance and higher rates of the dye release from the mitochondria. The release of Rh123 can be controlled by the mitochondrial membrane permeability transition (PT) pore, as targeting an inner membrane component of the PT pore by cyclosporin A (CsA) inhibited Rh123 release. However, metaxin deficiency and Bcl-X(L) overexpression apparently affect Rh123 release from a site(s) different from that of CsA, as CsA can overcome their effect. Though both metaxin and Bcl-X(L) appear to function on the outer mitochondrial membrane, they do not interact with each other. They may use different mechanisms to increase the permeability of Rh123, since previous studies have suggested that metaxin may influence certain outer membrane porins while Bcl-X(L) may form pores on the outer membrane. The alteration of the mitochondrial outer membrane properties by metaxin deficiency and Bcl-X(L) overexpression, as indicated by a quicker Rh123 release, may be helpful in maintaining mitochondrial integrity.
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Affiliation(s)
- Koh Ono
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
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1819
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Gentle IE, Wong WWL, Evans JM, Bankovacki A, Cook WD, Khan NR, Nachbur U, Rickard J, Anderton H, Moulin M, Lluis JM, Moujalled DM, Silke J, Vaux DL. In TNF-stimulated cells, RIPK1 promotes cell survival by stabilizing TRAF2 and cIAP1, which limits induction of non-canonical NF-kappaB and activation of caspase-8. J Biol Chem 2011; 286:13282-91. [PMID: 21339290 PMCID: PMC3075675 DOI: 10.1074/jbc.m110.216226] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 01/26/2011] [Indexed: 11/06/2022] Open
Abstract
RIPK1 is involved in signaling from TNF and TLR family receptors. After receptor ligation, RIPK1 not only modulates activation of both canonical and NIK-dependent NF-κB, but also regulates caspase-8 activation and cell death. Although overexpression of RIPK1 can cause caspase-8-dependent cell death, when RIPK1(-/-) cells are exposed to TNF and low doses of cycloheximide, they die more readily than wild-type cells, indicating RIPK1 has pro-survival as well as pro-apoptotic activities. To determine how RIPK1 promotes cell survival, we compared wild-type and RIPK1(-/-) cells treated with TNF. Although TRAF2 levels remained constant in TNF-treated wild-type cells, TNF stimulation of RIPK1(-/-) cells caused TRAF2 and cIAP1 to be rapidly degraded by the proteasome, which led to an increase in NIK levels. This resulted in processing of p100 NF-κB2 to p52, a decrease in levels of cFLIP(L), and activation of caspase-8, culminating in cell death. Therefore, the pro-survival effect of RIPK1 is mediated by stabilization of TRAF2 and cIAP1.
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Affiliation(s)
- Ian E. Gentle
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - W. Wei-Lynn Wong
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Joseph M. Evans
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Alexandra Bankovacki
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Wendy D. Cook
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Nufail R. Khan
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Ulrich Nachbur
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - James Rickard
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Holly Anderton
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Maryline Moulin
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Josep Maria Lluis
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - Donia M. Moujalled
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - John Silke
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
| | - David L. Vaux
- From the Department of Biochemistry and La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia
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1820
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Helicobacter pylori VacA induces programmed necrosis in gastric epithelial cells. Infect Immun 2011; 79:2535-43. [PMID: 21482684 DOI: 10.1128/iai.01370-10] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to the development of peptic ulcer disease and gastric cancer. The secreted pore-forming toxin VacA is one of the major virulence factors of H. pylori. In the current study, we show that AZ-521 human gastric epithelial cells are highly susceptible to VacA-induced cell death. Wild-type VacA causes death of these cells, whereas mutant VacA proteins defective in membrane channel formation do not. Incubation of AZ-521 cells with wild-type VacA results in cell swelling, poly(ADP-ribose) polymerase (PARP) activation, decreased intracellular ATP concentration, and lactate dehydrogenase (LDH) release. VacA-induced death of these cells is a caspase-independent process that results in cellular release of histone-binding protein high mobility group box 1 (HMGB1), a proinflammatory protein. These features are consistent with the occurrence of cell death through a programmed necrosis pathway and suggest that VacA can be included among the growing number of bacterial pore-forming toxins that induce cell death through programmed necrosis. We propose that VacA augments H. pylori-induced mucosal inflammation in the human stomach by causing programmed necrosis of gastric epithelial cells and subsequent release of proinflammatory proteins and may thereby contribute to the pathogenesis of gastric cancer and peptic ulceration.
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1821
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Coll NS, Epple P, Dangl JL. Programmed cell death in the plant immune system. Cell Death Differ 2011; 18:1247-56. [PMID: 21475301 DOI: 10.1038/cdd.2011.37] [Citation(s) in RCA: 565] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cell death has a central role in innate immune responses in both plants and animals. Besides sharing striking convergences and similarities in the overall evolutionary organization of their innate immune systems, both plants and animals can respond to infection and pathogen recognition with programmed cell death. The fact that plant and animal pathogens have evolved strategies to subvert specific cell death modalities emphasizes the essential role of cell death during immune responses. The hypersensitive response (HR) cell death in plants displays morphological features, molecular architectures and mechanisms reminiscent of different inflammatory cell death types in animals (pyroptosis and necroptosis). In this review, we describe the molecular pathways leading to cell death during innate immune responses. Additionally, we present recently discovered caspase and caspase-like networks regulating cell death that have revealed fascinating analogies between cell death control across both kingdoms.
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Affiliation(s)
- N S Coll
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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1822
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Yu M, Levine SJ. Toll-like receptor, RIG-I-like receptors and the NLRP3 inflammasome: key modulators of innate immune responses to double-stranded RNA viruses. Cytokine Growth Factor Rev 2011; 22:63-72. [PMID: 21466970 PMCID: PMC3109132 DOI: 10.1016/j.cytogfr.2011.02.001] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Double-stranded RNA (dsRNA), the genetic material for many RNA viruses, induces robust host immune responses via pattern recognition receptors, which include Toll-like receptor 3 (TLR3), retinoic acid-inducible gene-I-like receptors (RLRs) and the multi-protein NLRP3 inflammasome complex. The engagement of dsRNA receptors or inflammasome activation by viral dsRNA initiates complex intracellular signaling cascades that play essential roles in inflammation and innate immune responses, as well as the resultant development of adaptive immunity. This review focuses on signaling pathways mediated by TLR3, RLRs and the NLRP3 inflammasome, as well as the potential use of agonists and antagonists that target these pathways to treat disease.
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Affiliation(s)
- Man Yu
- Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
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1823
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Galluzzi L, Vitale I, Kroemer G. Past, present, and future of molecular and cellular oncology. Front Oncol 2011; 1:1. [PMID: 22655224 PMCID: PMC3356131 DOI: 10.3389/fonc.2011.00001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 03/11/2011] [Indexed: 12/18/2022] Open
Abstract
In the last 20 years, the field of cellular and molecular oncology has been born and has moved its first steps, with an increasingly rapid pace. Hundreds of oncogenic and oncosuppressive signaling cascades have been characterized, facilitating the development of an ever more refined and variegated arsenal of diagnostic and therapeutic weapons. Furthermore, several cancer-specific features and processes have been identified that constitute promising therapeutic targets. For instance, it has been demonstrated that microRNAs can play a critical role in oncogenesis and tumor suppression. Moreover, it turned out that tumor cells frequently exhibit an extensive metabolic rewiring, can behave in a stem cell-like fashion (and hence sustain tumor growth), often constitutively activate stress response pathways that allow them to survive, can react to therapy by engaging in non-apoptotic cell death programs, and sometimes die while eliciting a tumor-specific immune response. In this Perspective article, we discuss the main issues generated by these discoveries that will be in the limelight of molecular and cellular oncology research for the next, hopefully few years.
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1824
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Oberst A, Dillon CP, Weinlich R, McCormick LL, Fitzgerald P, Pop C, Hakem R, Salvesen GS, Green DR. Catalytic activity of the caspase-8-FLIP(L) complex inhibits RIPK3-dependent necrosis. Nature 2011; 471:363-7. [PMID: 21368763 PMCID: PMC3077893 DOI: 10.1038/nature09852] [Citation(s) in RCA: 1073] [Impact Index Per Article: 82.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 01/21/2011] [Indexed: 11/09/2022]
Abstract
Caspase-8 has two opposing biological functions--it promotes cell death by triggering the extrinsic pathway of apoptosis, but also has a survival activity, as it is required for embryonic development, T-lymphocyte activation, and resistance to necrosis induced by tumour necrosis factor-α (TNF-α) and related family ligands. Here we show that development of caspase-8-deficient mice is completely rescued by ablation of receptor interacting protein kinase-3 (RIPK3). Adult animals lacking both caspase-8 and RIPK3 display a progressive lymphoaccumulative disease resembling that seen with defects in CD95 or CD95-ligand (also known as FAS and FASLG, respectively), and resist the lethal effects of CD95 ligation in vivo. We have found that caspase-8 prevents RIPK3-dependent necrosis without inducing apoptosis by functioning in a proteolytically active complex with FLICE-like inhibitory protein long (FLIP(L), also known as CFLAR), and this complex is required for the protective function.
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Affiliation(s)
- Andrew Oberst
- Dept. of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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1825
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1826
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Ch'en IL, Tsau JS, Molkentin JD, Komatsu M, Hedrick SM. Mechanisms of necroptosis in T cells. ACTA ACUST UNITED AC 2011; 208:633-41. [PMID: 21402742 PMCID: PMC3135356 DOI: 10.1084/jem.20110251] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In caspase 8-deficient mouse T cells, necroptosis occurs via a Ripk3- and Ripk1-dependent pathway independent of autophagy and programmed necrosis. Cell populations are regulated in size by at least two forms of apoptosis. More recently, necroptosis, a parallel, nonapoptotic pathway of cell death, has been described, and this pathway is invoked in the absence of caspase 8. In caspase 8–deficient T cells, necroptosis occurs as the result of antigen receptor–mediated activation. Here, through a genetic analysis, we show that necroptosis in caspase 8–deficient T cells is related neither to the programmed necrosis as defined by the requirement for mitochondrial cyclophilin D nor to autophagy as defined by the requirement for autophagy-related protein 7. Rather, survival of caspase 8–defective T cells can be completely rescued by loss of receptor-interacting serine-threonine kinase (Ripk) 3. Additionally, complementation of a T cell–specific caspase 8 deficiency with a loss of Ripk3 gives rise to lymphoproliferative disease reminiscent of lpr or gld mice. In conjunction with previous work, we conclude that necroptosis in antigen-stimulated caspase 8–deficient T cells is the result of a novel Ripk1- and Ripk3-mediated pathway of cell death.
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Affiliation(s)
- Irene L Ch'en
- Division of Biological Sciences, Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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1827
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Hernandez JB, Newton RH, Walsh CM. Life and death in the thymus--cell death signaling during T cell development. Curr Opin Cell Biol 2011; 22:865-71. [PMID: 20810263 DOI: 10.1016/j.ceb.2010.08.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 07/31/2010] [Accepted: 08/05/2010] [Indexed: 12/27/2022]
Abstract
The thymus is an organ vital to proper T cell development, and the regulation of cell survival and death contributes significantly to its efficient function. Vital to many of the developmental processes that occur in the thymus, control over cell survival and death is orchestrated by several signaling processes. In this review, we focus on the regulation of death in early thymocytes known as CD4/CD8 double negative cells, including the roles of interleukin-7 and Bcl-2 family members in this developmental stage. We next consider the survival and death of later thymocytes that express both CD4 and CD8, the 'double-positive' thymocytes. These findings are discussed within the context of recent studies demonstrating the existence of caspase-independent cell death pathways.
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Affiliation(s)
- Jeniffer B Hernandez
- The Institute for Immunology and the Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA
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1828
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Zhang H, Zhou X, McQuade T, Li J, Chan FKM, Zhang J. Functional complementation between FADD and RIP1 in embryos and lymphocytes. Nature 2011; 471:373-6. [PMID: 21368761 PMCID: PMC3072026 DOI: 10.1038/nature09878] [Citation(s) in RCA: 436] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 01/27/2011] [Indexed: 11/30/2022]
Abstract
FADD is a common adaptor shared by several death-receptors (DRs) for signaling apoptosis through recruitment and activation of caspase 81-3. DRs are essential for immune homeostasis, but dispensable during embryogenesis. Surprisingly, FADD−/− mice die in utero4-5 and conditional deletion of FADD leads to impaired lymphocyte proliferation6-7. How FADD regulates embryogenesis and lymphocyte responses has been a long standing enigma. FADD could directly bind to RIP1, a serine/threonine kinase which mediates both necrosis and NF-κB activation. Here we show that FADD−/− embryos contain elevated levels of RIP1 and exhibit massive necrosis. To investigate potential in vivo functional interaction between RIP1 and FADD, null alleles of RIP1 were crossed into FADD−/− mice. Strikingly, RIP1 deficiency allowed normal embryogenesis of FADD−/− mice. Conversely, the developmental defect of RIP1−/− lymphocytes was partially corrected by FADD deletion. Furthermore, RIP1 deficiency fully restored normal proliferation in FADD−/− T cells but not in FADD−/− B cells. FADD−/−RIP1−/− double knockout (DKO) T cells are resistant to death induced by Fas or TNFα and display reduced NF-κB activity. Therefore, our data demonstrate an unexpected cell type-specific interplay between FADD and RIP1, which is critical for the regulation of apoptosis and necrosis during embryogenesis and lymphocyte function.
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Affiliation(s)
- Haibing Zhang
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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1829
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Kaiser WJ, Upton JW, Long AB, Livingston-Rosanoff D, Daley-Bauer LP, Hakem R, Caspary T, Mocarski ES. RIP3 mediates the embryonic lethality of caspase-8-deficient mice. Nature 2011; 471:368-72. [PMID: 21368762 PMCID: PMC3060292 DOI: 10.1038/nature09857] [Citation(s) in RCA: 907] [Impact Index Per Article: 69.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 01/24/2011] [Indexed: 11/12/2022]
Abstract
Apoptosis and necroptosis are complementary pathways controlled by common signaling adaptors, kinases and proteases; among these, caspase-8 (Casp8) is critical for death receptor (DR)-induced apoptosis. This caspase has also been implicated in nonapoptotic pathways that regulate Fas-associated via death domain (FADD)-dependent signaling and other less defined biological processes as diverse as innate immune signaling and myeloid or lymphoid differentiation patterns 1. Casp8 suppresses RIP3/RIP1 kinase complex-dependent 2–4 necroptosis 5 that follows DR-activation as well as a RIP3-dependent, RIP1-independent necrotic pathway that has emerged as a host defense mechanism against murine cytomegalovirus (MCMV) 6. Disruption of Casp8 expression leads to embryonic lethality in mice between E10.5 and E11.5 7. Thus, Casp8 may naturally hold alternative RIP3-dependent death pathways in check in addition to its role promoting apoptosis. We find that RIP3 is responsible for the midgestational death of Casp8-deficient embryos. Remarkably, Casp8−/−Rip3−/− double mutant mice are viable and mature into fertile adults with a full immune complement of myeloid and lymphoid cell types. These mice appear immunocompetent but develop lymphadenopathy by four months of age marked by accumulation of abnormal T cells in the periphery, a phenotype reminiscent of mice with Fas-deficiency (lpr/lpr). Casp8 contributes to homeostatic control in the adult immune system; however, RIP3 and Casp8 are together completely dispensable for mammalian development.
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Affiliation(s)
- William J Kaiser
- Department of Microbiology and Immunology, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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1830
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Abstract
Cell death induction by tumor necrosis factor has been an intensively studied area for the last two decades. Although it may appear that the skeleton should have been picked clean by now, new secrets about tumor necrosis factor death signaling are still being uncovered. In particular, the recent evidence that ubiquitination of the death kinase receptor-interacting protein 1 regulates its participation in apoptotic and necrotic cell death is opening up unexplored avenues in the catacombs of tumor necrosis factor death signaling. In this minireview, we focus on two major cell-death checkpoints that determine whether receptor-interacting protein 1 functions as a pro-survival or pro-death molecule.
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1831
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Knox PG, Davies CC, Ioannou M, Eliopoulos AG. The death domain kinase RIP1 links the immunoregulatory CD40 receptor to apoptotic signaling in carcinomas. ACTA ACUST UNITED AC 2011; 192:391-9. [PMID: 21282461 PMCID: PMC3101101 DOI: 10.1083/jcb.201003087] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
RIP1 is a component of a TRAF2 complex, required for caspase-8 activation and tumor cell killing in response to ligand binding of CD40. CD40, a tumor necrosis factor (TNF) receptor family member, is widely recognized for its prominent role in the antitumor immune response. The immunostimulatory effects of CD40 ligation on malignant cells can be switched to apoptosis upon disruption of survival signals transduced by the binding of the adaptor protein TRAF6 to CD40. Apoptosis induction requires a TRAF2-interacting CD40 motif but is initiated within a cytosolic death-inducing signaling complex after mobilization of receptor-bound TRAF2 to the cytoplasm. We demonstrate that receptor-interacting protein 1 (RIP1) is an integral component of this complex and is required for CD40 ligand-induced caspase-8 activation and tumor cell killing. Degradation of the RIP1 K63 ubiquitin ligases cIAP1/2 amplifies the CD40-mediated cytotoxic effect, whereas inhibition of CYLD, a RIP1 K63 deubiquitinating enzyme, reduces it. This two-step mechanism of apoptosis induction expands our appreciation of commonalities in apoptosis regulatory pathways across the TNF receptor superfamily and provides a telling example of how TNF family receptors usurp alternative programs to fulfill distinct cellular functions.
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Affiliation(s)
- Pauline G Knox
- Molecular and Cellular Biology Laboratory, Division of Basic Sciences, University of Crete Medical School, 71003 Heraklion, Greece
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1832
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Brereton CF, Blander JM. The unexpected link between infection-induced apoptosis and a TH17 immune response. J Leukoc Biol 2011; 89:565-76. [PMID: 21248151 DOI: 10.1189/jlb.0710421] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Microbial pathogens can initiate MOMP in host cells and as such, initiate the mitochondrial pathway of apoptosis. Innate immune recognition of cells dying in this way by infection-induced apoptosis would involve recognition of ligands derived from the apoptotic host cell simultaneously with those derived from the infecting pathogen. The resultant signal transduction pathways engaged direct DCs to concomitantly synthesize TGF-β and IL-6, two cytokines that subsequently favor the differentiation of naïve CD4 T cells into T(h)17 cells. Citrobacter rodentium is one rodent pathogen that targets mitochondria and induces apoptosis, and blockade of apoptosis during enteric Citrobacter infection impairs the characteristic T(h)17 response in the intestinal LP. Here, we review these original findings. We discuss microbial infections other than Citrobacter that have been shown to induce T(h)17 responses, and we examine what is known about the ability of those pathogens to induce apoptosis. We also consider types of cell death other than apoptosis that can be triggered by microbial infection, and we highlight how little we know about the impact of various forms of cell death on the ensuing adaptive immune response.
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Affiliation(s)
- Corinna F Brereton
- Mount Sinai School of Medicine, Immunology Institute, Department of Medicine, 1425 Madison Ave., 12-20D, New York, NY 10029, USA
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1833
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Distinct roles for the NF-kappa B RelA subunit during antiviral innate immune responses. J Virol 2011; 85:2599-610. [PMID: 21209118 DOI: 10.1128/jvi.02213-10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Production of type I interferons (IFNs; prominently, IFN-α/β) following virus infection is a pivotal antiviral innate immune response in higher vertebrates. The synthesis of IFN-β proceeds via the virus-induced assembly of the transcription factors IRF-3/7, ATF-2/c-Jun, and NF-κB on the ifnβ promoter. Surprisingly, recent data indicate that the NF-κB subunit RelA is not essential for virus-stimulated ifnβ expression. Here, we show that RelA instead sustains autocrine IFN-β signaling prior to infection. In the absence of RelA, virus infection results in significantly delayed ifnβ induction and consequently defective secondary antiviral gene expression. While RelA is not required for ifnβ expression after infection, it is nonetheless essential for fully one-fourth of double-stranded RNA (dsRNA)-activated genes, including several mediators of inflammation and immune cell recruitment. Further, RelA directly regulates a small subset of interferon-stimulated genes (ISGs). Finally, RelA also protects cells from dsRNA-triggered RIP1-dependent programmed necrosis. Taken together, our findings suggest distinct roles for RelA in antiviral innate immunity: RelA maintains autocrine IFN-β signaling in uninfected cells, facilitates inflammatory and adaptive immune responses following infection, and promotes infected-cell survival during this process.
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1834
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Multiple death pathways in TNF-treated fibroblasts: RIP3- and RIP1-dependent and independent routes. Cell Res 2011; 21:368-71. [PMID: 21200403 DOI: 10.1038/cr.2011.3] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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1835
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Ofengeim D, Miyawaki T, Suzanne zukin R. Molecular and Cellular Mechanisms of Ischemia-Induced Neuronal Death. Stroke 2011. [DOI: 10.1016/b978-1-4160-5478-8.10006-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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1836
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Workshop Summary: Novel Aspects of the Functions of the TRAFs and cIAPs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 691:53-61. [DOI: 10.1007/978-1-4419-6612-4_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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1837
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Northington FJ, Chavez-Valdez R, Graham EM, Razdan S, Gauda EB, Martin LJ. Necrostatin decreases oxidative damage, inflammation, and injury after neonatal HI. J Cereb Blood Flow Metab 2011; 31:178-89. [PMID: 20571523 PMCID: PMC3049482 DOI: 10.1038/jcbfm.2010.72] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Necrostatin-1 inhibits receptor-interacting protein (RIP)-1 kinase and programmed necrosis and is neuroprotective in adult rodent models. Owing to the prominence of necrosis and continuum cell death in neonatal hypoxia-ischemia (HI), we tested whether necrostatin was neuroprotective in the developing brain. Postnatal day (P)7 mice were exposed to HI and injected intracerebroventricularly with 0.1 μL of 80 μmol necrostatin, Nec-1, 5-(1H-Indol-3-ylmethyl)-(2-thio-3-methyl) hydantoin, or vehicle. Necrostatin significantly decreased injury in the forebrain and thalamus at P11 and P28. There was specific neuroprotection in necrostatin-treated males. Necrostatin treatment decreased necrotic cell death and increased apoptotic cell death. Hypoxia-ischemia enforced RIP1-RIP3 complex formation and inhibited RIP3-FADD (Fas-associated protein with death domain) interaction, and these effects were blocked by necrostatin. Necrostatin also decreased HI-induced oxidative damage to proteins and attenuated markers of inflammation coincidental with decreased nuclear factor-κB and caspase 1 activation, and FLIP ((Fas-associated death-domain-like IL-1β-converting enzyme)-inhibitory protein) gene and protein expression. In this model of severe neonatal brain injury, we find that cellular necrosis can be managed therapeutically by a single dose of necrostatin, administered after HI, possibly by interrupting RIP1-RIP3-driven oxidative injury and inflammation. The effects of necrostatin treatment after HI reflect the importance of necrosis in the delayed phases of neonatal brain injury and represent a new direction for therapy of neonatal HI.
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Affiliation(s)
- Frances J Northington
- Neonatal Research Laboratory, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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1838
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Mughal W, Kirshenbaum LA. Cell death signalling mechanisms in heart failure. Exp Clin Cardiol 2011; 16:102-8. [PMID: 22131851 PMCID: PMC3206101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 09/02/2011] [Indexed: 05/31/2023]
Abstract
Cardiac disease is a global epidemic that is on the rise, despite the recent advances in cardiovascular research. Once the myocardium is injured, it has a limited capacity to activate reparative mechanisms to restore proper cardiac function, leading to the development of systemic heart failure. Autophagy, under certain conditions, may result in cell death, further emphasizing the controversial issues regarding the autophagic process as an adaptive or maladaptive biological response. Although significant progress in understanding the signalling mechanisms of cell death in myocytes has been made, the role of apoptotic cell death and programmed necrosis during heart failure is not completely understood. Insight to how myocytes determine whether to activate apoptotic or programmed necrosis signalling machinery remains under current investigation because it is a major problem for both scientists and clinicians in treating heart failure patients. Herein, the different modes of cell death implicated in heart failure are highlighted, as well as the role of B-cell lymphoma-2 family members and how mitochondria act as central organelles in directing such cell death mechanisms.
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Affiliation(s)
- Wajihah Mughal
- The Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba
| | - Lorrie A Kirshenbaum
- The Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba
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1839
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Galluzzi L, Vanden Berghe T, Vanlangenakker N, Buettner S, Eisenberg T, Vandenabeele P, Madeo F, Kroemer G. Programmed necrosis from molecules to health and disease. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 289:1-35. [PMID: 21749897 DOI: 10.1016/b978-0-12-386039-2.00001-8] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
During the past decade, cell death researchers have witnessed a gradual but deep conceptual revolution: it has been unequivocally shown that necrosis, which for long had been considered as a purely accidental cell death mode, can also be induced by finely regulated signal transduction pathways. In particular, when caspases are inhibited by pharmacological or genetic means, the ligation of death receptors such as the tumor necrosis factor receptor 1 (TNFR1) can lead to the assembly of a supramolecular complex containing the receptor-interacting protein kinases 1 and 3 (RIP1 and RIP3) that delivers a pronecrotic signal. Such complex has recently been dubbed necrosome and mediates the execution of a specific instance of regulated necrosis, necroptosis. Soon, it turned out that programmed necrosis occurs in nonmammalian model organisms and that it is implicated in human diseases including ischemia and viral infection. In this review, we first describe the historical evolution of the concept of programmed necrosis and the molecular mechanisms that underlie necroptosis initiation and execution. We then provide evidence suggesting that necroptosis represents an ancient and evolutionarily conserved cell death modality that may be targeted for drug development.
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1840
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A RNA interference screen identifies RIP3 as an essential inducer of TNF-induced programmed necrosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 691:589-93. [PMID: 21153365 DOI: 10.1007/978-1-4419-6612-4_62] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Recent evidence indicates that TNF-like death cytokines can induce apoptotic and non-apoptotic forms of cell death. We have coined the term “programmed necrosis” to describe caspase-independent cell death induced by TNF-like cytokines. Besides an obligate requirement for the protein serine/threonine kinase RIP1 and the production of reactive oxygen species (ROS), relatively little is know about the molecular mechanisms that control TNF-induced programmed necrosis. In order to further illuminate the molecular pathway that governs programmed necrosis, we performed a targeted RNA interference (RNAi) screen. Our screen identified RIP3, a RIP1 family member, as a specific mediator for programmed necrosis, but not apoptosis. Biochemical analyses show that assembly of the pro-necrotic RIP1-RIP3 complex critically regulates induction of programmed necrosis. The physiological relevance of RIP3-dependent programmed necrosis is demonstrated by the failure of RIP3-deficient mice to control vaccinia virus infections.
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1841
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Young JA, Sermwittayawong D, Kim HJ, Nandu S, An N, Erdjument-Bromage H, Tempst P, Coscoy L, Winoto A. Fas-associated death domain (FADD) and the E3 ubiquitin-protein ligase TRIM21 interact to negatively regulate virus-induced interferon production. J Biol Chem 2010; 286:6521-31. [PMID: 21183682 DOI: 10.1074/jbc.m110.172288] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The production of cytokines such as type I interferon (IFN) is an essential component of innate immunity. Insufficient amounts of cytokines lead to host sensitivity to infection, whereas abundant cytokine production can lead to inflammation. A tight regulation of cytokine production is, thus, essential for homeostasis of the immune system. IFN-α production during RNA virus infection is mediated by the master transcription factor IRF7, which is activated upon ubiquitination by TRAF6 and phosphorylation by IKKε and TBK1 kinases. We found that Fas-associated death domain (FADD), first described as an apoptotic protein, is involved in regulating IFN-α production through a novel interaction with TRIM21. TRIM21 is a member of a large family of proteins that can impart ubiquitin modification onto its cellular targets. The interaction between FADD and TRIM21 enhances TRIM21 ubiquitin ligase activity, and together they cooperatively repress IFN-α activation in Sendai virus-infected cells. FADD and TRIM21 can directly ubiquitinate IRF7, affect its phosphorylation status, and interfere with the ubiquitin ligase activity of TRAF6. Conversely, a reduction of FADD and TRIM21 levels leads to higher IFN-α induction, IRF7 phosphorylation, and lower titers of RNA virus of infected cells. We conclude that FADD and TRIM21 together negatively regulate the late IFN-α pathway in response to viral infection.
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Affiliation(s)
- Jennifer A Young
- Cancer Research Laboratory and Department of Molecular and Cellular Biology, University of California, Berkeley, California 94720, USA
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1842
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Bedford L, Lowe J, Dick LR, Mayer RJ, Brownell JE. Ubiquitin-like protein conjugation and the ubiquitin-proteasome system as drug targets. Nat Rev Drug Discov 2010; 10:29-46. [PMID: 21151032 PMCID: PMC7097807 DOI: 10.1038/nrd3321] [Citation(s) in RCA: 434] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ubiquitin is a highly conserved 76 amino-acid protein that covalently attaches to protein substrates targeted for degradation by the 26S proteasome. The coordinated effort of a series of enzymes, including an activating enzyme (E1), a conjugating enzyme (E2) and a ligase (E3), uses ATP to ultimately form an isopeptide bond between ubiquitin and a substrate. Another class of enzymes called deubiquitylating enzymes (DUBs) deconstruct these linkages and also have an essential role in ubiquitin function. In addition, ubiquitin-like proteins (UBLs), including NEDD8, SUMO and ISG15, share a characteristic three-dimensional fold with ubiquitin but have their own dedicated enzyme cascades and distinct (although sometimes overlapping) biological functions. The ubiquitin–proteasome system (UPS) and UBL conjugation pathways have important roles in various human diseases, including numerous types of cancer, cardiovascular disease, viral diseases and neurodegenerative disorders. The proteasome inhibitor bortezomib (Velcade; Millennium Pharmaceuticals) is the first clinically validated drug to target the UPS and is approved for the treatment of multiple myeloma. This suggests that other diseases may conceivably be targeted by modulating components of the UPS and UBL conjugation pathways using small-molecule inhibitors. A significant hurdle to identifying drug-like inhibitors of enzyme targets within the UPS and UBL conjugation pathways is the limited understanding of the molecular mechanisms and biological consequences of UBL conjugation. Here, we provide an overview of the enzyme classes in the UPS and UBL pathways that are potential therapeutic targets, and highlight considerations that are important for drug discovery. We also discuss the progress in the development of small-molecule inhibitors, and review developments in understanding of the role of the components of the UPS and the UBL pathways in disease and their potential for therapeutic intervention.
The ubiquitin–proteasome system (UPS) and ubiquitin-like protein (UBL) conjugation pathways are integral to cellular protein homeostasis, and their functional importance in various diseases, including cancer, cardiovascular disease and neurodegenerative disorders, is now beginning to emerge. Brownell and colleagues review developments in understanding of the role of the components of the UPS and the UBL pathways in disease and their potential for therapeutic intervention. The ubiquitin–proteasome system (UPS) and ubiquitin-like protein (UBL) conjugation pathways are integral to cellular protein homeostasis. The growing recognition of the fundamental importance of these pathways to normal cell function and in disease has prompted an in-depth search for small-molecule inhibitors that selectively block the function of these pathways. However, our limited understanding of the molecular mechanisms and biological consequences of UBL conjugation is a significant hurdle to identifying drug-like inhibitors of enzyme targets within these pathways. Here, we highlight recent advances in understanding the role of some of these enzymes and how these new insights may be the key to developing novel therapeutics for diseases including immuno-inflammatory disorders, cancer, infectious diseases, cardiovascular disease and neurodegenerative disorders.
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Affiliation(s)
- Lynn Bedford
- School of Biomedical Sciences, University of Nottingham, Nottingham, UK.
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1843
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Abstract
Apoptosis can be thought of as a signalling cascade that results in the death of the cell. Properly executed apoptosis is critically important for both development and homoeostasis of most animals. Accordingly, defects in apoptosis can contribute to the development of autoimmune disorders, neurological diseases and cancer. Broadly speaking, there are two main pathways by which a cell can engage apoptosis: the extrinsic apoptotic pathway and the intrinsic apoptotic pathway. At the centre of the intrinsic apoptotic signalling pathway lies the mitochondrion, which, in addition to its role as the bioenergetic centre of the cell, is also the cell's reservoir of pro-death factors which reside in the mitochondrial IMS (intermembrane space). During intrinsic apoptosis, pores are formed in the OMM (outer mitochondrial membrane) of the mitochondria in a process termed MOMP (mitochondrial outer membrane permeabilization). This allows for the release of IMS proteins; once released during MOMP, some IMS proteins, notably cytochrome c and Smac/DIABLO (Second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI), promote caspase activation and subsequent cleavage of structural and regulatory proteins in the cytoplasm and the nucleus, leading to the demise of the cell. MOMP is achieved through the co-ordinated actions of pro-apoptotic members and inhibited by anti-apoptotic members of the Bcl-2 family of proteins. Other aspects of mitochondrial physiology, such as mitochondrial bioenergetics and dynamics, are also involved in processes of cell death that proceed through the mitochondria. Proper regulation of these mitochondrial functions is vitally important for the life and death of the cell and for the organism as a whole.
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1844
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XU Y, ZHAO XH. RIP3: a Possible Trigger of Apoptosis or Necrosis*. PROG BIOCHEM BIOPHYS 2010. [DOI: 10.3724/sp.j.1206.2010.00177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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1845
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Abstract
A canonical regulatory pathway involving the members of the Bcl-2 and caspase families has been established to regulate developmental apoptosis in nematodes and flies. However, mutant mice that have major deficiencies in this apoptosis pathway show only relatively minor developmental defects. Recent revelations indicate that multiple mechanisms are involved in regulating cell death during mammalian development, tissue homeostasis, and pathological cell loss. Here, we critically evaluate the evidence demonstrating the existence of alternative cell death mechanisms, including apoptosis of lower organisms in the absence of canonical apoptosis mediators, autophagic cell death, necroptosis, elimination by shedding, keratinocyte death by cornification, and cell-cell cannibalism by entosis. The physiological relevance of alternative cell death mechanisms as primary and backup mechanisms is discussed.
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Affiliation(s)
- Junying Yuan
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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1846
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Lopez J, Meier P. To fight or die - inhibitor of apoptosis proteins at the crossroad of innate immunity and death. Curr Opin Cell Biol 2010; 22:872-81. [PMID: 20888210 DOI: 10.1016/j.ceb.2010.08.025] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 08/30/2010] [Accepted: 08/30/2010] [Indexed: 11/26/2022]
Abstract
The processes of dying are as tightly regulated as those of growth and proliferation, and together they establish a finely tuned balance that ensures proper organ size and function. Failure in the regulation of these responses lies at the heart of many human diseases. Certain members of the inhibitor of apoptosis (IAP) protein family function as important gatekeepers of cell death and survival. While IAPs can regulate cell death by controlling caspases, they also modulate other signalling processes that impact on cell viability. Probably the most important contribution of IAPs to cell survival and tumorigenesis resides in the ability of a number of IAPs to act as ubiquitin-E3 ligases regulating NF-κB signalling. Here, we discuss the latest insights into the ubiquitin-related roles of IAPs and how this contributes to the survival of cells and the organism.
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Affiliation(s)
- Juanita Lopez
- The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, Mary-Jean Mitchell Green Building, Chester Beatty Laboratories, Fulham Road, London SW3 6JB, UK
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1847
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Baines CP. Role of the mitochondrion in programmed necrosis. Front Physiol 2010; 1:156. [PMID: 21423395 PMCID: PMC3059973 DOI: 10.3389/fphys.2010.00156] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Accepted: 11/16/2010] [Indexed: 12/26/2022] Open
Abstract
In contrast to the “programmed” nature of apoptosis and autophagy, necrotic cell death has always been believed to be a random, uncontrolled process that leads to the “accidental” death of the cell. This dogma, however, is being challenged and the concept of necrosis also being “programmed” is gaining ground. In particular, mitochondria appear to play a pivotal role in the mediation of programmed necrosis. The purpose of this review, therefore, is to appraise the current concepts regarding the signaling mechanisms of programmed necrosis, with specific attention to the contribution of mitochondria to this process.
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Affiliation(s)
- Christopher P Baines
- Department of Biomedical Sciences, and Department of Medical Pharmacology and Physiology, Dalton Cardiovascular Research Center, University of Missouri-Columbia Columbia, MO, USA.
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1848
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Systems biology approaches to dissect mammalian innate immunity. Curr Opin Immunol 2010; 23:71-7. [PMID: 21111589 DOI: 10.1016/j.coi.2010.10.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 10/29/2010] [Indexed: 01/09/2023]
Abstract
Advances in experimental tools have allowed for the systematic identification of components and biological processes as well as quantification of their activities over time. Together with computational analysis, these measurement and perturbation technologies have given rise to the field of systems biology, which seeks to discover, analyze and model the interactions of physical components in a biological system. Although in its infancy, recent application of this approach has resulted in novel insights into the machinery that regulates and modifies innate immune cell functions. Here, we summarize contributions that have been made through the unbiased interrogation of the mammalian innate immune system, emphasizing the importance of integrating orthogonal datasets into models. To enable application of approaches more broadly, however, a concerted effort across the immunology community to develop reagent and tool platforms will be required.
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1849
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Receptor interacting protein kinases mediate retinal detachment-induced photoreceptor necrosis and compensate for inhibition of apoptosis. Proc Natl Acad Sci U S A 2010; 107:21695-700. [PMID: 21098270 DOI: 10.1073/pnas.1009179107] [Citation(s) in RCA: 239] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apoptosis has been shown to be a significant form of cell loss in many diseases. Detachment of photoreceptors from the retinal pigment epithelium, as seen in various retinal disorders, causes photoreceptor loss and subsequent vision decline. Although caspase-dependent apoptotic pathways are activated after retinal detachment, caspase inhibition by the pan-caspase inhibitor Z-VAD fails to prevent photoreceptor death; thus, we investigated other pathways leading to cell loss. Here, we show that receptor interacting protein (RIP) kinase-mediated necrosis is a significant mode of photoreceptor cell loss in an experimental model of retinal detachment and when caspases are inhibited, RIP-mediated necrosis becomes the predominant form of death. RIP3 expression, a key activator of RIP1 kinase, increased more than 10-fold after retinal detachment. Morphological assessment of detached retinas treated with Z-VAD showed decreased apoptosis but significantly increased necrotic photoreceptor death. RIP1 kinase inhibitor necrostatin-1 or Rip3 deficiency substantially prevented those necrotic changes and reduced oxidative stress and mitochondrial release of apoptosis-inducing factor. Thus, RIP kinase-mediated programmed necrosis is a redundant mechanism of photoreceptor death in addition to apoptosis, and simultaneous inhibition of RIP kinases and caspases is essential for effective neuroprotection and may be a novel therapeutic strategy for treatment of retinal disorders.
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1850
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Jiang YG, Peng Y, Koussougbo KS. Necroptosis: a novel therapeutic target for glioblastoma. Med Hypotheses 2010; 76:350-2. [PMID: 21075544 DOI: 10.1016/j.mehy.2010.10.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/19/2010] [Accepted: 10/22/2010] [Indexed: 01/29/2023]
Abstract
Glioblastoma or glioblastoma multiforme (GBM) is the most encountered and malignant form of brain tumors in clinical practice. In spite of optimal and early treatment, the life expectancy of patients with GBM remains poor. It is believed that dysfunction of apoptosis underlies GBM tumorigenesis, proliferation and resistance to chemotherapy and radiotherapy. Although GBM is defective in apoptotic process, pathologic and radiologic observations almost always reveal obvious necrosis foci within GBM. Necrosis seems to be related with GBM proliferation, angiogenesis and invasion. However, tumor cell necrosis induced by various therapies has a potential therapeutic value. Just recently, necrotic cell death is considered as a regulated and controlled process, like apoptosis, termed necroptosis or programmed necrosis. Induction of apoptosis has not made any significant achievements in the treatment of GBM mainly because the tumor cells are apoptosis-resistant. We may achieve a better result by modulating the necroptosis of GBM thus circumvent the apoptosis resistance. Albeit specific molecular pathways involved in GBM necroptosis is not clear and much more studies are needed to confirm the effects of therapy-induced necroptosis on GBM, it provides us with a new direction in the treatment of GBM.
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Affiliation(s)
- Yu-Gang Jiang
- Department of Neurosurgery, Second Xiangya Hospital of Central South University, Changsha, Hunan Province 410011, China.
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