RESUMEN
Drug-tolerant persister cells (persisters) evade apoptosis upon targeted and conventional cancer therapies and represent a major non-genetic barrier to effective cancer treatment. Here, we show that cells that survive treatment with pro-apoptotic BH3 mimetics display a persister phenotype that includes colonization and metastasis in vivo and increased sensitivity toward ferroptosis by GPX4 inhibition. We found that sublethal mitochondrial outer membrane permeabilization (MOMP) and holocytochrome c release are key requirements for the generation of the persister phenotype. The generation of persisters is independent of apoptosome formation and caspase activation, but instead, cytosolic cytochrome c induces the activation of heme-regulated inhibitor (HRI) kinase and engagement of the integrated stress response (ISR) with the consequent synthesis of ATF4, all of which are required for the persister phenotype. Our results reveal that sublethal cytochrome c release couples sublethal MOMP to caspase-independent initiation of an ATF4-dependent, drug-tolerant persister phenotype.
Asunto(s)
Citocromos c , Neoplasias/tratamiento farmacológico , Animales , Apoptosis , Proteínas Portadoras , Caspasas/metabolismo , Citocromos c/metabolismo , Resistencia a Antineoplásicos , Humanos , Ratones , Mitocondrias/metabolismoRESUMEN
Through their many and varied metabolic functions, mitochondria power life. Paradoxically, mitochondria also have a central role in apoptotic cell death. Upon induction of mitochondrial apoptosis, mitochondrial outer membrane permeabilization (MOMP) usually commits a cell to die. Apoptotic signalling downstream of MOMP involves cytochrome c release from mitochondria and subsequent caspase activation. As such, targeting MOMP in order to manipulate cell death holds tremendous therapeutic potential across different diseases, including neurodegenerative diseases, autoimmune disorders and cancer. In this Review, we discuss new insights into how mitochondria regulate apoptotic cell death. Surprisingly, recent data demonstrate that besides eliciting caspase activation, MOMP engages various pro-inflammatory signalling functions. As we highlight, together with new findings demonstrating cell survival following MOMP, this pro-inflammatory role suggests that mitochondria-derived signalling downstream of pro-apoptotic cues may also have non-lethal functions. Finally, we discuss the importance and roles of mitochondria in other forms of regulated cell death, including necroptosis, ferroptosis and pyroptosis. Collectively, these new findings offer exciting, unexplored opportunities to target mitochondrial regulation of cell death for clinical benefit.
Asunto(s)
Apoptosis/fisiología , Mitocondrias/metabolismo , Mitocondrias/fisiología , Animales , Caspasas/metabolismo , Citocromos c/metabolismo , Humanos , Membranas Mitocondriales/metabolismo , Membranas Mitocondriales/fisiología , Transducción de SeñalRESUMEN
Receptor-interacting protein kinase-3 (RIPK3) is an activator of necroptotic cell death, but recent work has implicated additional roles for RIPK3 in inflammatory signaling independent of cell death. However, while necroptosis has been shown to contribute to antiviral immunity, death-independent roles for RIPK3 in host defense have not been demonstrated. Using a mouse model of West Nile virus (WNV) encephalitis, we show that RIPK3 restricts WNV pathogenesis independently of cell death. Ripk3-/- mice exhibited enhanced mortality compared to wild-type (WT) controls, while mice lacking the necroptotic effector MLKL, or both MLKL and caspase-8, were unaffected. The enhanced susceptibility of Ripk3-/- mice arose from suppressed neuronal chemokine expression and decreased central nervous system (CNS) recruitment of T lymphocytes and inflammatory myeloid cells, while peripheral immunity remained intact. These data identify pleiotropic functions for RIPK3 in the restriction of viral pathogenesis and implicate RIPK3 as a key coordinator of immune responses within the CNS.
Asunto(s)
Proteína Serina-Treonina Quinasas de Interacción con Receptores/metabolismo , Fiebre del Nilo Occidental/inmunología , Virus del Nilo Occidental/fisiología , Animales , Sistema Nervioso Central/metabolismo , Quimiocinas/inmunología , Leucocitos/inmunología , Macrófagos/inmunología , Ratones , Ratones Endogámicos C57BL , Necrosis , Neuronas/metabolismoRESUMEN
Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP)1. Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated2. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence. During apoptosis, widespread mitochondrial outer membrane permeabilization (MOMP) commits a cell to die3. Here we find that MOMP occurring in a subset of mitochondria is a feature of cellular senescence. This process, called minority MOMP (miMOMP), requires BAX and BAK macropores enabling the release of mitochondrial DNA (mtDNA) into the cytosol. Cytosolic mtDNA in turn activates the cGAS-STING pathway, a major regulator of the SASP. We find that inhibition of MOMP in vivo decreases inflammatory markers and improves healthspan in aged mice. Our results reveal that apoptosis and senescence are regulated by similar mitochondria-dependent mechanisms and that sublethal mitochondrial apoptotic stress is a major driver of the SASP. We provide proof-of-concept that inhibition of miMOMP-induced inflammation may be a therapeutic route to improve healthspan.
Asunto(s)
Apoptosis , Senescencia Celular , Citosol , ADN Mitocondrial , Mitocondrias , Animales , Ratones , Citosol/metabolismo , ADN Mitocondrial/metabolismo , Mitocondrias/genética , Mitocondrias/metabolismo , Necrosis por Permeabilidad de la Transmembrana Mitocondrial , Prueba de Estudio Conceptual , Inflamación/metabolismo , Fenotipo , Longevidad , Envejecimiento SaludableRESUMEN
Sensing nutrient availability is essential for appropriate cellular growth, and mTORC1 is a major regulator of this process. Mechanisms causing mTORC1 activation are, however, complex and diverse. We report here an additional important step in the activation of mTORC1, which regulates the efflux of amino acids from lysosomes into the cytoplasm. This process requires DRAM-1, which binds the membrane carrier protein SCAMP3 and the amino acid transporters SLC1A5 and LAT1, directing them to lysosomes and permitting efficient mTORC1 activation. Consequently, we show that loss of DRAM-1 also impacts pathways regulated by mTORC1, including insulin signaling, glycemic balance, and adipocyte differentiation. Interestingly, although DRAM-1 can promote autophagy, this effect on mTORC1 is autophagy independent, and autophagy only becomes important for mTORC1 activation when DRAM-1 is deleted. These findings provide important insights into mTORC1 activation and highlight the importance of DRAM-1 in growth control, metabolic homeostasis, and differentiation.
Asunto(s)
Aminoácidos/metabolismo , Proteína 7 Relacionada con la Autofagia/metabolismo , Metabolismo Energético , Lisosomas/enzimología , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Proteínas de la Membrana/metabolismo , Células 3T3-L1 , Adipocitos/enzimología , Adipogénesis , Sistema de Transporte de Aminoácidos ASC/genética , Sistema de Transporte de Aminoácidos ASC/metabolismo , Sistema de Transporte de Aminoácidos y+L/genética , Sistema de Transporte de Aminoácidos y+L/metabolismo , Animales , Proteína 7 Relacionada con la Autofagia/genética , Glucemia/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Activación Enzimática , Células HEK293 , Células HeLa , Humanos , Insulina/sangre , Transportador de Aminoácidos Neutros Grandes 1/genética , Transportador de Aminoácidos Neutros Grandes 1/metabolismo , Masculino , Diana Mecanicista del Complejo 1 de la Rapamicina/genética , Proteínas de la Membrana/deficiencia , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Antígenos de Histocompatibilidad Menor/genética , Antígenos de Histocompatibilidad Menor/metabolismo , Transporte de ProteínasRESUMEN
The anti-apoptotic BCL-2 protein family regulates cancer cell survival, thus it represents an important therapeutic target. Indeed, a drug class, called BH3-mimetics, have been developed to directly target BCL2 proteins and promote cancer cell death. Conventional wisdom suggests that the primary anti-cancer effect of BCL-2 inhibition is through induction of cancer cell death. However, a recent study by Zhao and colleagues describes that BCL-2 inhibition also enhances the function of classical dendritic cells, unleashing their role in immunosurveillance, promoting T cell immunity and tumour regression. Thus, inhibiting anti-apoptotic BCL-2 function may have a multi-pronged anti-tumour action.
Asunto(s)
Antineoplásicos , Neoplasias , Humanos , Apoptosis , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Neoplasias/tratamiento farmacológico , Neoplasias/metabolismo , Antineoplásicos/farmacología , Antineoplásicos/uso terapéutico , Proteínas Reguladoras de la Apoptosis/farmacología , Proteínas Reguladoras de la Apoptosis/uso terapéutico , Línea Celular TumoralRESUMEN
Cytosolic DNA is recognized by the innate immune system as a potential threat. During apoptotic cell death, mitochondrial DNA (mtDNA) release activates the DNA sensor cyclic GMP-AMP synthase (cGAS) to promote a pro-inflammatory type I interferon response. Inflammation following mtDNA release during apoptotic cell death can be exploited to engage anti-tumor immunity and represents a potential avenue for cancer therapy. Additionally, various studies have described leakage of mtDNA, independent of cell death, with different underlying cues such as pathogenic infections, changes in mtDNA packaging, mtDNA stress or reduced mitochondrial clearance. The interferon response in these scenarios can be beneficial but also potentially disadvantageous, as suggested by a variety of disease phenotypes. In this review, we discuss mechanisms underlying mtDNA release governed by cell death pathways and summarize release mechanisms independent of cell death. We further highlight the similarities and differences in mtDNA release pathways, outlining gaps in our knowledge and questions for further research. Together, a deeper understanding of how and when mtDNA is released may enable the development of drugs to specifically target or inhibit mtDNA release in different disease settings.
Asunto(s)
ADN Mitocondrial , Mitocondrias , Humanos , ADN Mitocondrial/metabolismo , Mitocondrias/metabolismo , Inflamación/metabolismo , Apoptosis , Interferones/metabolismoRESUMEN
During apoptosis, the mitochondrial outer membrane is permeabilized, leading to the release of cytochrome c that activates downstream caspases. Mitochondrial outer membrane permeabilization (MOMP) has historically been thought to occur synchronously and completely throughout a cell, leading to rapid caspase activation and apoptosis. Using a new imaging approach, we demonstrate that MOMP is not an all-or-nothing event. Rather, we find that a minority of mitochondria can undergo MOMP in a stress-regulated manner, a phenomenon we term "minority MOMP." Crucially, minority MOMP leads to limited caspase activation, which is insufficient to trigger cell death. Instead, this caspase activity leads to DNA damage that, in turn, promotes genomic instability, cellular transformation, and tumorigenesis. Our data demonstrate that, in contrast to its well-established tumor suppressor function, apoptosis also has oncogenic potential that is regulated by the extent of MOMP. These findings have important implications for oncogenesis following either physiological or therapeutic engagement of apoptosis.
Asunto(s)
Apoptosis/fisiología , Daño del ADN , Inestabilidad Genómica , Membranas Mitocondriales/fisiología , Animales , Apoptosis/efectos de los fármacos , Compuestos de Bifenilo/farmacología , Western Blotting , Caspasas/metabolismo , Línea Celular Tumoral , Inhibidor p19 de las Quinasas Dependientes de la Ciclina/deficiencia , Inhibidor p19 de las Quinasas Dependientes de la Ciclina/genética , Relación Dosis-Respuesta a Droga , Embrión de Mamíferos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Células HCT116 , Células HeLa , Histonas/metabolismo , Humanos , Células MCF-7 , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Confocal , Nitrofenoles/farmacología , Permeabilidad , Piperazinas/farmacología , Proteínas Proto-Oncogénicas c-bcl-2/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Estaurosporina/farmacología , Sulfonamidas/farmacología , Factores de TiempoRESUMEN
The use of bacteria as an alternative cancer therapy has been reinvestigated in recent years. SL7207: an auxotrophic Salmonella enterica serovar Typhimurium aroA mutant with immune-stimulatory potential has proven a promising strain for this purpose. Here, we show that systemic administration of SL7207 induces melanoma tumor growth arrest in vivo, with greater survival of the SL7207-treated group compared to control PBS-treated mice. Administration of SL7207 is accompanied by a change in the immune phenotype of the tumor-infiltrating cells toward pro-inflammatory, with expression of the TH 1 cytokines IFN-γ, TNF-α, and IL-12 significantly increased. Interestingly, Ly6C+ MHCII+ monocytes were recruited to the tumors following SL7207 treatment and were pro-inflammatory. Accordingly, the abrogation of these infiltrating monocytes using clodronate liposomes prevented SL7207-induced tumor growth inhibition. These data demonstrate a previously unappreciated role for infiltrating inflammatory monocytes underlying bacterial-mediated tumor growth inhibition. This information highlights a possible novel role for monocytes in controlling tumor growth, contributing to our understanding of the immune responses required for successful immunotherapy of cancer.
Asunto(s)
Inmunoterapia , Melanoma Experimental , Monocitos/inmunología , Salmonella typhimurium/inmunología , Células TH1/inmunología , Animales , Citocinas/inmunología , Femenino , Melanoma Experimental/inmunología , Melanoma Experimental/terapia , Ratones , Salmonella typhimurium/genéticaRESUMEN
Mitochondrial outer membrane permeabilization (MOMP) is often required for activation of the caspase proteases that cause apoptotic cell death. Various intermembrane space (IMS) proteins, such as cytochrome c, promote caspase activation following their mitochondrial release. As a consequence, mitochondrial outer membrane integrity is highly controlled, primarily through interactions between pro- and anti-apoptotic members of the B cell lymphoma 2 (BCL-2) protein family. Following MOMP by pro-apoptotic BCL-2-associated X protein (BAX) or BCL-2 antagonist or killer (BAK), additional regulatory mechanisms govern the mitochondrial release of IMS proteins and caspase activity. MOMP typically leads to cell death irrespective of caspase activity by causing a progressive decline in mitochondrial function, although cells can survive this under certain circumstances, which may have pathophysiological consequences.
Asunto(s)
Mitocondrias/metabolismo , Membranas Mitocondriales/metabolismo , Animales , Caspasas/metabolismo , Muerte Celular , Humanos , Proteína X Asociada a bcl-2/farmacocinéticaRESUMEN
Mitochondria are organelles central to myriad cellular processes. To maintain mitochondrial health, various processes co-operate at both the molecular and organelle level. At the molecular level, mitochondria can sense imbalances in their homeostasis and adapt to these by signaling to the nucleus. This mito-nuclear communication leads to the expression of nuclear stress response genes. Upon external stimuli, mitochondria can also alter their morphology accordingly, by inducing fission or fusion. In an extreme situation, mitochondria are degraded by mitophagy. Adequate function and regulation of these mitochondrial quality control pathways are crucial for cellular homeostasis. As we discuss, alterations in these processes have been linked to several pathologies including neurodegenerative diseases and cancer.
Asunto(s)
Mitocondrias/metabolismo , Dinámicas Mitocondriales , Mitofagia , Animales , Humanos , Mitocondrias/patología , Neoplasias/metabolismo , Neoplasias/patología , Enfermedades Neurodegenerativas/metabolismo , Enfermedades Neurodegenerativas/patología , Proteínas Quinasas/metabolismo , Transducción de Señal , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro-inflammatory and pro-oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phenotypes while preserving ATP production via enhanced glycolysis. Global transcriptomic analysis by RNA sequencing revealed that a vast number of senescent-associated changes are dependent on mitochondria, particularly the pro-inflammatory phenotype. Mechanistically, we show that the ATM, Akt and mTORC1 phosphorylation cascade integrates signals from the DNA damage response (DDR) towards PGC-1ß-dependent mitochondrial biogenesis, contributing to aROS-mediated activation of the DDR and cell cycle arrest. Finally, we demonstrate that the reduction in mitochondrial content in vivo, by either mTORC1 inhibition or PGC-1ß deletion, prevents senescence in the ageing mouse liver. Our results suggest that mitochondria are a candidate target for interventions to reduce the deleterious impact of senescence in ageing tissues.
Asunto(s)
Envejecimiento/fisiología , Mitocondrias/fisiología , Animales , Línea Celular , Humanos , Ratones , Modelos Biológicos , FenotipoRESUMEN
The Bcl-2 proteins Bax and Bak can permeabilize the outer mitochondrial membrane and commit cells to apoptosis. Pro-survival Bcl-2 proteins control Bax by constant retrotranslocation into the cytosol of healthy cells. The stabilization of cytosolic Bax raises the question whether the functionally redundant but largely mitochondrial Bak shares this level of regulation. Here we report that Bak is retrotranslocated from the mitochondria by pro-survival Bcl-2 proteins. Bak is present in the cytosol of human cells and tissues, but low shuttling rates cause predominant mitochondrial Bak localization. Interchanging the membrane anchors of Bax and Bak reverses their subcellular localization compared to the wild-type proteins. Strikingly, the reduction of Bax shuttling to the level of Bak retrotranslocation results in full Bax toxicity even in absence of apoptosis induction. Thus, fast Bax retrotranslocation is required to protect cells from commitment to programmed death.
Asunto(s)
Apoptosis/fisiología , Citosol/metabolismo , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Proteína Destructora del Antagonista Homólogo bcl-2/metabolismo , Proteína X Asociada a bcl-2/metabolismo , Línea Celular , Humanos , Mitocondrias/genética , Proteínas Mitocondriales/genética , Transporte de Proteínas/fisiología , Proteína Destructora del Antagonista Homólogo bcl-2/genética , Proteína X Asociada a bcl-2/genéticaRESUMEN
Necroptosis is a form of programmed cell death defined by activation of the kinase receptor interacting protein kinase 3 and its downstream effector, the pseudokinase mixed lineage kinase domain-like (MLKL). Activated MLKL translocates to the cell membrane and disrupts it, leading to loss of cellular ion homeostasis. In this study, we use a system in which this event can be specifically triggered by a small-molecule ligand to show that MLKL activation is sufficient to induce the processing and release of bioactive IL-1ß. MLKL activation triggers potassium efflux and assembly of the NLRP3 inflammasome, which is required for the processing and activity of IL-1ß released during necroptosis. Notably, MLKL activation also causes cell membrane disruption, which allows efficient release of IL-1ß independently of the recently described pyroptotic effector gasdermin-D. Taken together, our findings indicate that MLKL is an endogenous activator of the NLRP3 inflammasome, and that MLKL activation provides a mechanism for concurrent processing and release of IL-1ß independently of gasdermin-D.
Asunto(s)
Apoptosis , Inflamasomas/metabolismo , Interleucina-1beta/metabolismo , Monocitos/fisiología , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Necrosis , Proteínas Quinasas/metabolismo , Línea Celular , Membrana Celular/metabolismo , Homeostasis , Humanos , Péptidos y Proteínas de Señalización Intracelular , Proteínas de Neoplasias/metabolismo , Proteínas de Unión a Fosfato , Potasio/metabolismo , Transducción de Señal , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
During apoptosis, the BCL-2 protein family controls mitochondrial outer membrane permeabilization (MOMP), but the dynamics of this regulation remain controversial. We employed chimeric proteins composed of exogenous BH3 domains inserted into a tBID backbone that can activate the proapoptotic effectors BAX and BAK to permeabilize membranes without being universally sequestered by all antiapoptotic BCL-2 proteins. We thus identified two "modes" whereby prosurvival BCL-2 proteins can block MOMP, by sequestering direct-activator BH3-only proteins ("MODE 1") or by binding active BAX and BAK ("MODE 2"). Notably, we found that MODE 1 sequestration is less efficient and more easily derepressed to promote MOMP than MODE 2. Further, MODE 2 sequestration prevents mitochondrial fusion. We provide a unified model of BCL-2 family function that helps to explain otherwise paradoxical observations relating to MOMP, apoptosis, and mitochondrial dynamics.
Asunto(s)
Apoptosis , Regulación de la Expresión Génica , Mitocondrias Hepáticas/metabolismo , Membranas Mitocondriales/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Transducción de Señal , Secuencia de Aminoácidos , Animales , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteína Proapoptótica que Interacciona Mediante Dominios BH3/genética , Proteína Proapoptótica que Interacciona Mediante Dominios BH3/metabolismo , Citocromos c/análisis , Células HeLa , Humanos , Mamíferos , Ratones , Ratones Noqueados , Anotación de Secuencia Molecular , Permeabilidad , Unión Proteica , Proteínas Recombinantes de Fusión/genética , Alineación de Secuencia , Transfección , Proteína Destructora del Antagonista Homólogo bcl-2/genética , Proteína Destructora del Antagonista Homólogo bcl-2/metabolismo , Proteína X Asociada a bcl-2/genética , Proteína X Asociada a bcl-2/metabolismo , Proteína bcl-X/genética , Proteína bcl-X/metabolismoRESUMEN
Caspase-2 is an initiator caspase activated in response to heat shock and other stressors that induce apoptosis. Activation of caspase-2 requires induced proximity resulting after recruitment to caspase-2 activation complexes such as the PIDDosome. We have adapted bimolecular fluorescence complementation (BiFC) to measure caspase-2 induced proximity in real time in single cells. Nonfluorescent fragments of the fluorescent protein Venus that can associate to reform the fluorescent complex were fused to caspase-2, allowing visualization and kinetic measurements of caspase-2 induced proximity after heat shock and other stresses. This revealed that the caspase-2 activation platform occurred in the cytosol and not in the nucleus in response to heat shock, DNA damage, cytoskeletal disruption, and other treatments. Activation, as measured by this approach, in response to heat shock was RAIDD dependent and upstream of mitochondrial outer-membrane permeabilization. Furthermore, we identify Hsp90alpha as a key negative regulator of heat shock-induced caspase-2 activation.
Asunto(s)
Apoptosis , Caspasa 2/metabolismo , Citoplasma/enzimología , Estrés Fisiológico , Animales , Apoptosis/efectos de los fármacos , Factor Apoptótico 1 Activador de Proteasas/metabolismo , Proteínas Bacterianas/genética , Técnicas Biosensibles , Proteína Adaptadora de Señalización CRADD/metabolismo , Caspasa 2/genética , Daño del ADN , Proteínas de Unión al ADN/metabolismo , Activación Enzimática , Proteína de Dominio de Muerte Asociada a Fas/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Células HeLa , Factores de Transcripción del Choque Térmico , Calor , Humanos , Cinética , Proteínas Luminiscentes/genética , Ratones , Ratones Noqueados , Microscopía Confocal , Mitocondrias/metabolismo , Mitocondrias/patología , Mutagénesis Sitio-Dirigida , Multimerización de Proteína , Interferencia de ARN , Proteínas Recombinantes de Fusión/metabolismo , Transducción de Señal , Factores de Transcripción/metabolismo , Transfección , Moduladores de Tubulina/farmacologíaRESUMEN
Regulated, programmed cell death is crucial for all multicellular organisms. Cell death is essential in many processes, including tissue sculpting during embryogenesis, development of the immune system and destruction of damaged cells. The best-studied form of programmed cell death is apoptosis, a process that requires activation of caspase proteases. Recently it has been appreciated that various non-apoptotic forms of cell death also exist, such as necroptosis and pyroptosis. These non-apoptotic cell death modalities can be either triggered independently of apoptosis or are engaged should apoptosis fail to execute. In this Commentary, we discuss several regulated non-apoptotic forms of cell death including necroptosis, autophagic cell death, pyroptosis and caspase-independent cell death. We outline what we know about their mechanism, potential roles in vivo and define outstanding questions. Finally, we review data arguing that the means by which a cell dies actually matters, focusing our discussion on inflammatory aspects of cell death.
Asunto(s)
Muerte Celular/fisiología , Animales , Apoptosis/fisiología , Autofagia/fisiología , HumanosRESUMEN
Since entering our cells in an endosymbiotic event one billion years ago, mitochondria have shaped roles for themselves in metabolism, inflammation, calcium storage, migration, and cell death. Given this critical role in cellular homeostasis it is essential that they function correctly. Equally critical is the ability of a cell to remove damaged or superfluous mitochondria to avoid potential deleterious effects. In this review we will discuss the various mechanisms of mitochondrial clearance, with a particular focus on Parkin/PINK1-mediated mitophagy, discuss the impact of altered mitophagy in ageing and disease, and finally consider potential therapeutic benefits of targeting mitophagy.
Asunto(s)
Autofagia , Mitocondrias , Animales , Enfermedad , Humanos , Mitocondrias/metabolismo , Mitocondrias/patología , Proteínas Quinasas/metabolismo , Transducción de Señal , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Macroautophagy (hereafter termed autophagy) is a cellular membrane-trafficking process that functions to deliver cytoplasmic constituents to lysosomes for degradation. Autophagy operates at basal levels to turn over damaged and misfolded proteins and it is the only process for the turnover of organelles. The process is therefore critically important for the preservation of cellular integrity and viability. Autophagy is also highly adaptable and the rate and cargoes of autophagy can be altered to bring about desired cellular responses to intracellular and environmental cues, disease states and a spectrum of pharmaceutical drugs. As a result, there is much interest in understanding the dynamics of autophagy in a variety of situations. To date, the majority of assays to monitor autophagy either measure changes in a parameter of the process at a set point in time or use markers/tracers to monitor flow of membrane-bound proteins from one point in the process to another. As such, these assays do not measure changes in endogenous cargo degradation which is the ultimate end-point of the autophagy process. We describe here an assay to measure autophagic cargo degradation by engineering cells to degrade mitochondria en masse. We show that this 'enhanced-mitophagy' assay can be used to measure differences in the rate of autophagy between different cells or in response to agents which are known to promote or inhibit autophagic flux. We consider therefore that this assay will prove to be a valuable resource for investigations in which autophagy is considered important and is believed to be modulated.