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Proceedings of the National Academy of... Dec 2023Mitochondrial apoptotic signaling cascades lead to the formation of the apoptosome, a 1.1-MDa heptameric protein scaffold that recruits and activates the caspase-9...
Mitochondrial apoptotic signaling cascades lead to the formation of the apoptosome, a 1.1-MDa heptameric protein scaffold that recruits and activates the caspase-9 protease. Once activated, caspase-9 cleaves and activates downstream effector caspases, triggering the onset of cell death through caspase-mediated proteolysis of cellular proteins. Failure to activate caspase-9 enables the evasion of programmed cell death, which occurs in various forms of cancer. Despite the critical apoptotic function of caspase-9, the structural mechanism by which it is activated on the apoptosome has remained elusive. Here, we used a combination of methyl-transverse relaxation-optimized NMR spectroscopy, protein engineering, and biochemical assays to study the activation of caspase-9 bound to the apoptosome. In the absence of peptide substrate, we observed that both caspase-9 and its isolated protease domain (PD) only very weakly dimerize with dissociation constants in the millimolar range. Methyl-NMR spectra of isotope-labeled caspase-9, within the 1.3-MDa native apoptosome complex or an engineered 480-kDa apoptosome mimic, reveal that the caspase-9 PD remains monomeric after recruitment to the scaffold. Binding to the apoptosome, therefore, organizes caspase-9 PDs so that they can rapidly and extensively dimerize only when substrate is present, providing an important layer in the regulation of caspase-9 activation. Our work highlights the unique role of NMR spectroscopy to structurally characterize protein domains that are flexibly tethered to large scaffolds, even in cases where the molecular targets are in excess of 1 MDa, as in the present example.
Topics: Caspase 9; Apoptosomes; Caspases; Apoptosis; Magnetic Resonance Spectroscopy; Caspase 3
PubMed: 38085782
DOI: 10.1073/pnas.2310944120 -
Oncotarget Apr 2017As the most intensively studied initiator caspase, caspase-9 is a key player in the intrinsic or mitochondrial pathway which is involved in various stimuli, including... (Review)
Review
As the most intensively studied initiator caspase, caspase-9 is a key player in the intrinsic or mitochondrial pathway which is involved in various stimuli, including chemotherapies, stress agents and radiation. Caspase-9 is activated on the apoptosome complex to remain catalytic status and is thought of involving homo-dimerization monomeric zymogens. Failing to activate caspase-9 has profound physiological and pathophysiological outcomes, leading to degenerative and developmental disorders even cancer. To govern the apoptotic commitment process appropriately, plenty of proteins and small molecules involved in regulating caspase-9. Therefore, this review is to summarize recent pertinent literature on the comprehensive description of the molecular events implicated in caspase-9 activation and inhibition, as well as the clinical trials in progress to give deep insight into caspase-9 for suppressing cancer. We hope that our concerns will be helpful for further clinical studies addressing the roles of caspase-9 and its regulators demanded to identify more effective solutions to overcome intrinsic apoptosis-related diseases especially cancer.
Topics: Animals; Apoptosis; Caspase 9; Humans; Phosphorylation; Signal Transduction
PubMed: 28177918
DOI: 10.18632/oncotarget.15098 -
Molecular Aspects of Medicine Dec 2022Regulated cell death is defined as genetically encoded pathways that lead towards the demise of cells. In mammals, cell demise can be either inflammatory or... (Review)
Review
Regulated cell death is defined as genetically encoded pathways that lead towards the demise of cells. In mammals, cell demise can be either inflammatory or non-inflammatory, depending on whether the mechanism of death results in cell rupture or not. Inflammatory cell death can lead towards acute and chronic disease. Therefore, it becomes important to distinguish the mechanisms that result in these different inflammatory cell death outcomes. Apoptosis is a non-inflammatory form of cell death where cells resist rupture. In contrast, pyroptosis and necroptosis are inflammatory forms of cell death principally because of release of pro-inflammatory mediators from cells undergoing lysis. This review focusses on the mechanisms of these different cell death outcomes with specific emphasis on the caspase family of proteolytic enzymes.
Topics: Animals; Humans; Caspases; Inflammasomes; Pyroptosis; Necroptosis; Inflammation; Apoptosis; Mammals
PubMed: 35248371
DOI: 10.1016/j.mam.2022.101085 -
Trends in Microbiology Dec 2021The programmed cell death pathways of pyroptosis and apoptosis protect mammals from infections. The activation of host cell death signaling depends on cell surface and... (Review)
Review
The programmed cell death pathways of pyroptosis and apoptosis protect mammals from infections. The activation of host cell death signaling depends on cell surface and cytosolic receptors that bind bacterial molecules or sense their activity. The formation of cytosolic protein complexes, such as the inflammasome and apoptosome, activates caspases, pore-forming proteins, and inflammatory cytokines. These pathways respond to bacteria and their released membrane vesicles. Outer membrane vesicles (OMVs) that emerge from the outer membrane of Gram-negative bacteria deliver a range of bacterial molecules, including lipids, proteins, polysaccharides and nucleic acids to host cells. Recent findings describe how OMV-associated molecules activate pyroptosis, apoptosis, and other inflammatory pathways. We discuss here how OMV-associated molecules are sensed by the immune system and how this contributes to infections and inflammatory diseases.
Topics: Animals; Apoptosis; Bacterial Outer Membrane; Bacterial Outer Membrane Proteins; Cell Membrane; Extracellular Vesicles; Gram-Negative Bacteria; Inflammasomes; Mammals
PubMed: 34001418
DOI: 10.1016/j.tim.2021.04.003 -
Journal of Personalized Medicine Aug 2022To adapt to the tumor environment or to escape chemotherapy, cancer cells rapidly reprogram their metabolism. The hallmark biochemical phenotype of cancer cells is the... (Review)
Review
To adapt to the tumor environment or to escape chemotherapy, cancer cells rapidly reprogram their metabolism. The hallmark biochemical phenotype of cancer cells is the shift in metabolic reprogramming towards aerobic glycolysis. It was thought that this metabolic shift to glycolysis alone was sufficient for cancer cells to meet their heightened energy and metabolic demands for proliferation and survival. Recent studies, however, show that cancer cells rely on glutamine, lipid, and mitochondrial metabolism for energy. Oncogenes and scavenging pathways control many of these metabolic changes, and several metabolic and tumorigenic pathways are post-transcriptionally regulated by microRNA (miRNAs). Genes that are directly or indirectly responsible for energy production in cells are either negatively or positively regulated by miRNAs. Therefore, some miRNAs play an oncogenic role by regulating the metabolic shift that occurs in cancer cells. Additionally, miRNAs can regulate mitochondrial calcium stores and energy metabolism, thus promoting cancer cell survival, cell growth, and metastasis. In the electron transport chain (ETC), miRNAs enhance the activity of apoptosis-inducing factor (AIF) and cytochrome c, and these apoptosome proteins are directed towards the ETC rather than to the apoptotic pathway. This review will highlight how miRNAs regulate the enzymes, signaling pathways, and transcription factors of cancer cell metabolism and mitochondrial calcium import/export pathways. The review will also focus on the metabolic reprogramming of cancer cells to promote survival, proliferation, growth, and metastasis with an emphasis on the therapeutic potential of miRNAs for cancer treatment.
PubMed: 36013278
DOI: 10.3390/jpm12081329 -
Proceedings of the National Academy of... Feb 2024The onset of apoptosis is characterized by a cascade of caspase activation, where initiator caspases are activated by a multimeric adaptor complex known as the...
The onset of apoptosis is characterized by a cascade of caspase activation, where initiator caspases are activated by a multimeric adaptor complex known as the apoptosome. In , the initiator caspase Dronc undergoes autocatalytic activation in the presence of the Dark apoptosome. Despite rigorous investigations, the activation mechanism for Dronc remains elusive. Here, we report the cryo-EM structures of an auto-inhibited Dark monomer and a single-layered, multimeric Dark/Dronc complex. Our biochemical analysis suggests that the auto-inhibited Dark oligomerizes upon binding to Dronc, which is sufficient for the activation of both Dark and Dronc. In contrast, the previously observed double-ring Dark apoptosome may represent a non-functional or "off-pathway" conformation. These findings expand our understanding on the molecular mechanism of apoptosis in .
Topics: Animals; Apoptosomes; Caspases; Drosophila; Drosophila melanogaster; Drosophila Proteins
PubMed: 38381783
DOI: 10.1073/pnas.2312784121 -
Current Opinion in Structural Biology Dec 2014Members of the NOD-like receptor (NLR) family mediate the innate immune response to a wide range of pathogens, tissue damage and other cellular stresses. They achieve... (Review)
Review
Members of the NOD-like receptor (NLR) family mediate the innate immune response to a wide range of pathogens, tissue damage and other cellular stresses. They achieve modulation of these signals by forming oligomeric signaling platforms, which in analogy to the apoptosome are predicted to adopt a defined oligomeric architecture and will here be referred to as NLR oligomers. Once formed, oligomers of the NLR proteins NLRP3 or NLRC4 'recruit' the adaptor protein ASC and the effector caspase-1, whereby NLRC4 can also directly interact with caspase-1. This results in large multi-protein assemblies, termed inflammasomes. Ultimately, the formation of these inflammasomes leads to the activation of caspase-1, which then processes the cytokines IL-1β and IL-18 triggering the immune response. Here we review new insights into NLR structure and implications on NLR oligomer formation as well as the nature of multi-protein inflammasomes. Of note, so dubbed 'canonical inflammasomes' can also be triggered by the NLR NLRP1b and the non-NLR protein AIM2, however the most detailed mechanistic information at hand pertains to NLRC4 while NLRP3 represents the quintessential inflammasome trigger. Thus these two NLRs are mainly used as examples in this article.
Topics: Apoptosomes; Apoptotic Protease-Activating Factor 1; CARD Signaling Adaptor Proteins; Calcium-Binding Proteins; Carrier Proteins; Caspase 10; Cytoskeletal Proteins; DNA-Binding Proteins; Gene Expression Regulation; Humans; Immunity, Innate; Inflammasomes; Interleukin-18; Interleukin-1beta; NLR Family, Pyrin Domain-Containing 3 Protein; Protein Conformation; Pyrin; Signal Transduction
PubMed: 25201319
DOI: 10.1016/j.sbi.2014.08.011 -
Biochemical Society Transactions Jun 2021Molecular chaperones are essential components of the protein quality control system and maintenance of homeostasis. Heat Shock Protein 70 (HSP70), a highly... (Review)
Review
Molecular chaperones are essential components of the protein quality control system and maintenance of homeostasis. Heat Shock Protein 70 (HSP70), a highly evolutionarily conserved family of chaperones is a key regulator of protein folding, oligomerisation and prevents the aggregation of misfolded proteins. HSP70 chaperone function depends on the so-called 'HSP70-cycle', where HSP70 interacts with and is released from substrates via ATP hydrolysis and the assistance of HSP70 co-factors/co-chaperones, which also provide substrate specificity. The identification of regulatory modules for HSP70 allows the elucidation of HSP70 specificity and target selectivity. Here, we discuss how the HSP70 cycle is functionally linked with the cycle of the Ubiquitin-like molecule NEDD8. Using as an example the DNA damage response, we present a model where HSP70 acts as a sensor of the NEDD8 cycle. The NEDD8 cycle acts as a regulatory module of HSP70 activity, where conversion of poly-NEDD8 chains into mono-NEDD8 upon DNA damage activates HSP70, facilitating the formation of the apoptosome and apoptosis execution.
Topics: Adenosine Triphosphate; Animals; DNA; DNA Damage; DNA Repair; HSP70 Heat-Shock Proteins; Humans; Hydrolysis; Molecular Chaperones; NEDD8 Protein
PubMed: 34156462
DOI: 10.1042/BST20200381 -
Cellular and Molecular Life Sciences :... Feb 2015Programmed cell death plays a central role in the regulation of homeostasis and development of multicellular organisms. Deregulation of programmed cell death is... (Review)
Review
Programmed cell death plays a central role in the regulation of homeostasis and development of multicellular organisms. Deregulation of programmed cell death is connected to a number of disorders, including cancer and autoimmune diseases. Initiation of cell death occurs in the multiprotein complexes or high molecular weight platforms. Composition, structure, and molecular interactions within these platforms influence the cellular decision toward life or death and, therefore, define the induction of a particular cell death program. Here, we discuss in detail the key cell-death complexes-including DISC, complex II, and TNFRI complex I/II, and the necrosome, RIPoptosome, apoptosome, and PIDDosome-that control apoptosis or necroptosis pathways as well as their regulation. The possibility of their pharmacological targeting leading to the development of new strategies of interference with cell death programs via control of the high molecular weight platforms will be discussed.
Topics: Apoptosomes; Caspase 2; Cell Death; Death Domain Receptor Signaling Adaptor Proteins; Models, Biological; Multiprotein Complexes; Necrosis; Signal Transduction
PubMed: 25323133
DOI: 10.1007/s00018-014-1757-2 -
Journal of Molecular Endocrinology Aug 2016Enhanced inflammation and reduced apoptosis sustain the growth of endometriotic lesions. Alterations in the expression of estrogen receptor-alpha (ERα) and estrogen... (Review)
Review
Enhanced inflammation and reduced apoptosis sustain the growth of endometriotic lesions. Alterations in the expression of estrogen receptor-alpha (ERα) and estrogen receptor-beta (ERβ) accompany the conversion of resident endometrial cells within the normal uterine environment to ectopic lesions located in extrauterine sites. Recent studies highlighted in this focused review linked ERβ to dysregulation of apoptotic and inflammatory networks involving novel interacting partners in endometriosis. The elucidation of these nongenomic actions of ERβ using human cells and mouse models is an important step in understanding key regulatory pathways that are disrupted leading to disease establishment and progression.
Topics: Animals; Apoptosis; Endometriosis; Endometrium; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Gene Expression Regulation; Humans; Inflammasomes; Inflammation; Models, Biological; Protein Binding; Signal Transduction
PubMed: 27272520
DOI: 10.1530/JME-16-0080