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Immunity Feb 2016Some forms of regulated cell death, such as apoptosis, are precipitated by the activation of cysteine proteases of the caspase family, including caspase 8, 9, and 3.... (Review)
Review
Some forms of regulated cell death, such as apoptosis, are precipitated by the activation of cysteine proteases of the caspase family, including caspase 8, 9, and 3. Other caspases, such as caspase 1 and 4, are well known for their pro-inflammatory functions but regulate cell death in a limited number of pathophysiological settings. Accumulating evidence suggests that the most conserved function of mammalian caspases is not to control cell death sensu stricto, but to regulate inflammatory and immune reactions to dying cells and infectious challenges. Here, we review the molecular and cellular mechanisms though which mammalian caspases connect cell-death signaling to the maintenance of organismal homeostasis.
Topics: Animals; Caspases; Cell Death; Homeostasis; Humans; Signal Transduction
PubMed: 26885855
DOI: 10.1016/j.immuni.2016.01.020 -
Apoptosis : An International Journal on... Oct 2020Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a...
Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a pro-apoptotic function of acetylcholinesterase (AChE), particularly in the formation of the apoptosome and the degradation of nuclear DNA. While three AChE splice variants are present in mammals, invertebrates typically express two ache genes that code for a synaptically located protein and a protein with non-synaptic functions respectively. In order to investigate a potential contribution of AChE to apoptosis in insects, we selected the migratory locust Locusta migratoria. We established primary neuronal cultures of locust brains and characterized apoptosis progression in vitro. Dying neurons displayed typical characteristics of apoptosis, including caspase-activation, nuclear condensation and DNA fragmentation visualized by TUNEL staining. Addition of the AChE inhibitors neostigmine and territrem B reduced apoptotic cell death under normal culture conditions. Moreover, both inhibitors completely suppressed hypoxia-induced neuronal cell death. Exposure of live animals to severe hypoxia moderately increased the expression of ace-1 in locust brains in vivo. Our results indicate a previously unreported role of AChE in insect apoptosis that parallels the pro-apoptotic role in mammalian cells. This similarity adds to the list of apoptotic mechanisms shared by mammals and insects, supporting the hypothesized existence of an ancient, complex apoptosis regulatory network present in common ancestors of vertebrates and insects.
Topics: Acetylcholinesterase; Animals; Apoptosis; Brain; Cell Death; Cell Nucleus; DNA Fragmentation; Grasshoppers; Hypoxia; Insecta; Neurons; Peptidyl-Dipeptidase A
PubMed: 32761307
DOI: 10.1007/s10495-020-01630-4 -
PLoS Pathogens Dec 2023Staphylococcus aureus is a dangerous pathogen that evolved refined immuno-evasive strategies to antagonize host immune responses. This involves the biogenesis of...
Staphylococcus aureus is a dangerous pathogen that evolved refined immuno-evasive strategies to antagonize host immune responses. This involves the biogenesis of death-effector deoxyribonucleosides, which kill infectious foci-penetrating macrophages. However, the exact mechanisms whereby staphylococcal death-effector deoxyribonucleosides and coupled imbalances of intracellular deoxyribonucleotide species provoke immune cell death remain elusive. Here, we report that S. aureus systematically promotes an overload of deoxyribonucleotides to trigger mitochondrial rupture in macrophages, a fatal event that induces assembly of the caspase-9-processing apoptosome and subsequent activation of the intrinsic pathway of apoptosis. Remarkably, genetic disruption of this cascade not only helps macrophages coping with death-effector deoxyribonucleoside-mediated cytotoxicity but also enhances their infiltration into abscesses thereby ameliorating pathogen control and infectious disease outcomes in laboratory animals. Combined with the discovery of protective alleles in human CASP9, these data highlight the role of mitochondria-centered apoptosis during S. aureus infection and suggest that gene polymorphisms may shape human susceptibility toward a predominant pathogen.
Topics: Animals; Humans; Staphylococcus aureus; Nucleotides; Phagocytes; Cell Death; Apoptosis; Mitochondria; Deoxyribonucleosides
PubMed: 38157331
DOI: 10.1371/journal.ppat.1011892 -
ACS Omega Sep 2021The molecular mechanism of apoptosome activation through conformational changes of Apaf-1 auto-inhibited form remains largely enigmatic. The crystal structure of Apaf-1...
The molecular mechanism of apoptosome activation through conformational changes of Apaf-1 auto-inhibited form remains largely enigmatic. The crystal structure of Apaf-1 suggests that some ionic bonds, including the bond between K192 and D616, are critical for the preservation of the inactive "closed" form of Apaf-1. Here, a split luciferase complementation assay was used to monitor the effect of disrupting this ionic bond on apoptosome activation and caspase-3 activity in cells. The K192E mutation, predicted to disrupt the ionic interaction with D616, increased apoptosome formation and caspase activity, suggesting that this mutation favors the "open"/active form of Apaf-1. However, mutation of D616 to alanine or lysine had different effects. While both mutants favored apoptosome formation such as K192E, D616K cannot activate caspases and D616A activates caspases poorly, and not as well as wild-type Apaf-1. Thus, our data show that the ionic bond between K192 and D616 is critical for maintaining the closed form of Apaf-1 and that disrupting the interaction enhances apoptosome formation. However, our data also reveal that after apoptosome formation, D616 and K192 play a previously unsuspected role in caspase activation. The molecular explanation for this observation is yet to be elucidated.
PubMed: 34514227
DOI: 10.1021/acsomega.1c02274 -
Trends in Plant Science Jan 2020Both animals and plants express intracellular innate immunity receptors known as NLR (NOD-like receptors or nucleotide-binding domain and leucine-rich repeat receptors,... (Review)
Review
Both animals and plants express intracellular innate immunity receptors known as NLR (NOD-like receptors or nucleotide-binding domain and leucine-rich repeat receptors, respectively). For various mammalian systems, the specific formation of macromolecular structures, such as inflammasomes by activated NLR receptors, has been extensively reported. However, for plant organisms, the formation of such structures was an open scientific question for many years. This year, the first plant 'resistosome' structure was reported, revealing significant structural similarities to mammalian apoptosome and inflammasome structures. In this review, we summarize the key components comprising the mammalian apoptosome/inflammasome structures and the newly discovered plant resistosome, highlighting their commonalities and differences.
Topics: Animals; Carrier Proteins; Immunity, Innate; Inflammasomes; NLR Proteins; Plants
PubMed: 31677931
DOI: 10.1016/j.tplants.2019.09.008 -
Cell Death & Disease Feb 2021Execution of the intrinsic apoptotic pathway is controlled by the BCL-2 proteins at the level of the mitochondrial outer membrane (MOM). This family of proteins consists... (Review)
Review
Execution of the intrinsic apoptotic pathway is controlled by the BCL-2 proteins at the level of the mitochondrial outer membrane (MOM). This family of proteins consists of prosurvival (e.g., BCL-2, MCL-1) and proapoptotic (e.g., BIM, BAD, HRK) members, the functional balance of which dictates the activation of BAX and BAK. Once activated, BAX/BAK form pores in the MOM, resulting in cytochrome c release from the mitochondrial intermembrane space, leading to apoptosome formation, caspase activation, and cleavage of intracellular targets. This pathway is induced by cellular stress including DNA damage, cytokine and growth factor withdrawal, and chemotherapy/drug treatment. A well-documented defense of leukemia cells is to shift the balance of the BCL-2 family in favor of the prosurvival proteins to protect against such intra- and extracellular stimuli. Small molecule inhibitors targeting the prosurvival proteins, named 'BH3 mimetics', have come to the fore in recent years to treat hematological malignancies, both as single agents and in combination with standard-of-care therapies. The most significant example of these is the BCL-2-specific inhibitor venetoclax, given in combination with standard-of-care therapies with great success in AML in clinical trials. As the number and variety of available BH3 mimetics increases, and investigations into applying these novel inhibitors to treat myeloid leukemias continue apace the need to evaluate where we currently stand in this rapidly expanding field is clear.
Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Bridged Bicyclo Compounds, Heterocyclic; Drug Design; Humans; Leukemia, Myeloid; Molecular Mimicry; Molecular Targeted Therapy; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Sulfonamides
PubMed: 33637708
DOI: 10.1038/s41419-021-03500-6 -
Mitochondrion Sep 2022Mitochondria are double-membrane organelles that provide the majority of a cell's energy. Furthermore, mitochondria are involved in various cellular biological... (Review)
Review
Mitochondria are double-membrane organelles that provide the majority of a cell's energy. Furthermore, mitochondria are involved in various cellular biological activities, including calcium signalling, reactive oxygen species production, apoptosis, cell development, and the cell cycle. Mitochondrial dysfunction is seen in various neurological conditions involving acute and chronic neural injury, including neurodegenerative diseases, hypoxia-induced brain injury, and ischemia. This review made a significant contribution to the explanation of the idea that mitochondria would both be critical targets of ischemia-induced processes, including intracellular calcium elevation and reactive oxygen species and essential sites for determining cell viability loss. As a result, it's not unexpected that attempts to prevent I/R damage have focused on mitochondria. Drugs such as vatiquinone, vitexin, dexprmipexole, baicalin, nobiletin, via promoting mitochondrial activities, can be used in future studies for protecting the brain from ischemia injury. This review summarizes mitochondrial pathways, i.e., Bad, Drp-1, JNK/caspase-3, MAPK-ERK, p53, Wnt/β-Catenin, that contribute to disease progression. We have précised the potential regulatory role of miRNA-mitochondrial dynamics in cerebral ischemic-reperfusion injury and associated molecular mechanisms; also provide insight into the potential therapies for cerebral injury-induced injuries.
Topics: Apoptosis; Brain Injuries; Calcium; Caspase 3; Humans; Ischemia; MicroRNAs; Mitochondrial Dynamics; Reactive Oxygen Species; Reperfusion Injury; Tumor Suppressor Protein p53; beta Catenin
PubMed: 35940452
DOI: 10.1016/j.mito.2022.08.001 -
Frontiers in Cell and Developmental... 2021Programmed cell death (PCD) in animals mainly refers to lytic and non-lytic forms. Disruption and integrity of the plasma membrane are considered as hallmarks of lytic... (Review)
Review
Programmed cell death (PCD) in animals mainly refers to lytic and non-lytic forms. Disruption and integrity of the plasma membrane are considered as hallmarks of lytic and apoptotic cell death, respectively. These lytic cell death programs can prevent the hosts from microbial pathogens. The key to our understanding of these cases is pattern recognition receptors, such as TLRs in animals and LRR-RLKs in plants, and nod-like receptors (NLRs). Herein, we emphatically discuss the biochemical and structural studies that have clarified the anti-apoptotic and pro-apoptotic functions of Bcl-2 family proteins during intrinsic apoptosis and how caspase-8 among apoptosis, necroptosis, and pyroptosis sets the switchable threshold and integrates innate immune signaling, and that have compared the similarity and distinctness of the apoptosome, necroptosome, and inflammasome. We recapitulate that the necroptotic MLKL pore, pyroptotic gasdermin pore, HR-inducing resistosome, and mitochondrial Bcl-2 family all can form ion channels, which all directly boost membrane disruption. Comparing the conservation and unique aspects of PCD including ferrroptosis among bacteria, animals, and plants, the commonly shared immune domains including TIR-like, gasdermin-like, caspase-like, and MLKL/CC-like domains act as arsenal modules to restructure the diverse architecture to commit PCD suicide upon stresses/stimuli for host community.
PubMed: 35223864
DOI: 10.3389/fcell.2021.790117 -
Molecular Biology of the Cell May 2023The actin cytoskeleton is a ubiquitous participant in cellular functions that maintain viability, but how it controls programmed cell death is not well understood. Here...
The actin cytoskeleton is a ubiquitous participant in cellular functions that maintain viability, but how it controls programmed cell death is not well understood. Here we show that in response to DNA damage, human cells form a juxtanuclear F-actin-rich territory that coordinates the organized progression of apoptosome assembly to caspase activation. This cytoskeletal compartment is created by the actin nucleation factors JMY, WHAMM, and the Arp2/3 complex, and it excludes proteins that inhibit JMY and WHAMM activity. Within the territory, mitochondria undergo outer membrane permeabilization and JMY localization overlaps with punctate structures containing the core apoptosome components cytochrome and Apaf-1. The F-actin-rich area also encompasses initiator caspase-9 and clusters of a cleaved form of executioner caspase-3 but restricts accessibility of the caspase inhibitor XIAP. The clustering and potency of caspase-3 activation are positively regulated by the amount of actin polymerized by JMY and WHAMM. These results indicate that JMY-mediated actin reorganization functions in apoptotic signaling by coupling the biogenesis of apoptosomes to the localized processing of caspases.
Topics: Humans; Actins; Caspase 3; Apoptosomes; Apoptosis; Caspases; Actin Cytoskeleton; DNA Damage; Membrane Proteins; Microtubule-Associated Proteins
PubMed: 36920061
DOI: 10.1091/mbc.E22-04-0119 -
Cold Spring Harbor Protocols Dec 2015This protocol describes an in vitro model for studying the mechanisms of caspase activation and native apoptosome complex assembly in cell-free extracts. Active caspases...
This protocol describes an in vitro model for studying the mechanisms of caspase activation and native apoptosome complex assembly in cell-free extracts. Active caspases in dATP-activated lysates are detected by fluorimetry using a tetrapeptide substrate (DEVD) tagged with a fluorophore (AFC), which, when released, produces a real-time readout for caspase-3 and -7 (DEVDase) activity. Gel filtration is used to isolate the apoptosome complex from the activated lysates, and assembly of Apaf-1 and caspase-9 from their monomeric forms into the multiprotein apoptosome can be confirmed via western blot. Apoptosome complex activity can be shown by incubation with exogenous procaspase-3 and -7 followed by fluorimetric bioassay (to confirm functionality of the processed effector caspases) and/or western blotting (for detection of cleaved caspase-3 and -7). A method for preparation of free procaspases for the bioassay is also described.
Topics: Animals; Apoptosomes; Blotting, Western; Caspases; Cell Line; Cell-Free System; Chromatography, Gel; Fluorometry; Humans; Rats
PubMed: 26631121
DOI: 10.1101/pdb.prot087080