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Advanced Science (Weinheim,... Oct 2022Chemotherapeutics remain the first choice for advanced gastric cancers (GCs). However, drug resistance and unavoidable severe toxicity lead to chemotherapy failure and...
Chemotherapeutics remain the first choice for advanced gastric cancers (GCs). However, drug resistance and unavoidable severe toxicity lead to chemotherapy failure and poor prognosis. Long noncoding RNAs (lncRNAs) play critical roles in tumor progression in many cancers, including GC. Here, through RNA screening, an apoptotic protease-activating factor 1 (APAF1)-binding lncRNA (ABL) that is significantly elevated in cancerous GC tissues and an independent prognostic factor for GC patients is identified. Moreover, ABL overexpression inhibits GC cell apoptosis and promotes GC cell survival and multidrug resistance in GC xenograft and organoid models. Mechanistically, ABL directly binds to the RNA-binding protein IGF2BP1 via its KH1/2 domain, and then IGF2BP1 further recognizes the METTL3-mediated m6A modification on ABL, which maintains ABL stability. In addition, ABL can bind to the WD1/WD2 domain of APAF1, which competitively prevent cytochrome c from interacting with APAF1, blocking apoptosome assembly and caspase-9/3 activation; these events lead to resistance to cell death in GC cells. Intriguingly, targeting ABL using encapsulated liposomal siRNA can significantly enhance the sensitivity of GC cells to chemotherapy. Collectively, the results suggest that ABL can be a potential prognostic biomarker and therapeutic target in GC.
Topics: Apoptosis; Apoptosomes; Apoptotic Protease-Activating Factor 1; Biomarkers; Caspase 9; Cytochromes c; Drug Resistance, Multiple; Humans; Methyltransferases; RNA, Long Noncoding; RNA, Small Interfering; Stomach Neoplasms
PubMed: 35975461
DOI: 10.1002/advs.202201889 -
Structure (London, England : 1993) Apr 2013Apaf-1-like molecules assemble into a ring-like platform known as the apoptosome. This cell death platform then activates procaspases in the intrinsic cell death... (Review)
Review
Apaf-1-like molecules assemble into a ring-like platform known as the apoptosome. This cell death platform then activates procaspases in the intrinsic cell death pathway. In this review, crystal structures of Apaf-1 monomers and CED-4 dimers have been combined with apoptosome structures to provide insights into the assembly of cell death platforms in humans, nematodes, and flies. In humans, the caspase recognition domains (CARDs) of procaspase-9 and Apaf-1 interact with each other to form a CARD-CARD disk, which interacts with the platform to create an asymmetric proteolysis machine. The disk tethers multiple pc-9 catalytic domains to the platform to raise their local concentration, and this leads to zymogen activation. These findings have now set the stage for further studies of this critical activation process on the apoptosome.
Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Apoptosomes; Apoptotic Protease-Activating Factor 1; Caenorhabditis elegans; Calcium-Binding Proteins; Caspase 9; Dimerization; Drosophila; Enzyme Activation; Humans; Models, Molecular; Protein Conformation; Species Specificity
PubMed: 23561633
DOI: 10.1016/j.str.2013.02.024 -
Cell Death and Differentiation Jul 2018The apoptosome is a platform that activates apical procaspases in response to intrinsic cell death signals. Biochemical and structural studies in the past two decades... (Review)
Review
The apoptosome is a platform that activates apical procaspases in response to intrinsic cell death signals. Biochemical and structural studies in the past two decades have extended our understanding of apoptosome composition and structure, while illuminating the requirements for initiator procaspase activation. A number of studies have now provided high-resolution structures for apoptosomes from C. elegans (CED-4), D. melanogaster (Dark), and H. sapiens (Apaf-1), which define critical protein interfaces, including intra and interdomain interactions. This work also reveals interactions of apoptosomes with their respective initiator caspases, CED-3, Dronc and procaspase-9. Structures of the human apoptosome have defined the requirements for cytochrome c binding, which triggers the conversion of inactive Apaf-1 molecules to an extended, assembly competent state. While recent data have provided a detailed understanding of apoptosome formation and procaspase activation, they also highlight important evolutionary differences with functional implications for caspase activation. Comparison of the CARD/CARD disks and apoptosomes formed by CED-4, Dark and Apaf-1. Cartoons of the active states of the CARD-CARD disks, illustrating the two CED-4 CARD tetrameric ring layers (CED4a and CED4b; top row) and the binding of 8 Dronc CARDs and between 3-4 pc-9 CARDs, to the Dark and Apaf-1 CARD disk respectively (middle and lower rows). Ribbon diagrams of the active CED-4, Dark and Apaf-1 apoptosomes are shown (right column).
Topics: Animals; Apoptosomes; Apoptotic Protease-Activating Factor 1; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Caspase 9; Drosophila Proteins; Drosophila melanogaster; Humans
PubMed: 29765111
DOI: 10.1038/s41418-017-0025-z -
Apoptosis : An International Journal on... Nov 2004Apoptosis is a cell suicide mechanism that enables organisms to control cell number and eliminate cells that threaten survival. The apoptotic cascade can be triggered... (Review)
Review
Apoptosis is a cell suicide mechanism that enables organisms to control cell number and eliminate cells that threaten survival. The apoptotic cascade can be triggered through two major pathways. Extracellular signals such as members of the tumor necrosis factor (TNF) family can activate the receptor-mediated extrinsic pathway. Alternatively, stress signals such as DNA damage, hypoxia, and loss of survival signals may trigger the mitochondrial intrinsic pathway. In the latter, mitochondrial damage results in cytochrome c release and formation of the apoptosome, a multimeric protein complex containing Apaf-1, cytochrome c , and caspase-9. Once bound to the apoptosome, caspase-9 is activated, and subsequently triggers a cascade of effector caspase activation and proteolysis, leading to apoptotic cell death. Recent efforts have led to the identification of multiple factors that modulate apoptosome formation and function. Alterations in the expression and/or function of these factors may contribute to the pathogenesis of cancer and resistance of tumor cells to chemotherapy or radiation. In this review we discuss how disruption of normal apoptosome formation and function may lead or contribute to tumor development and progression.
Topics: Animals; Apoptosis; Apoptotic Protease-Activating Factor 1; Caspases; Cytochrome c Group; Enzyme Activation; Humans; Mitochondria; Models, Biological; Neoplasms; Proteins; Tumor Necrosis Factors
PubMed: 15505412
DOI: 10.1023/B:APPT.0000045786.98031.1d -
Cell Death and Differentiation Jan 2007Apoptosome refers to the adaptor protein complex that mediates the activation of an initiator caspase at the onset of apoptosis. In mammalian cells, caspase-9,... (Review)
Review
Apoptosome refers to the adaptor protein complex that mediates the activation of an initiator caspase at the onset of apoptosis. In mammalian cells, caspase-9, caspase-8, and caspase-2 rely on the apoptotic protease-activating factor 1 (Apaf-1)-apoptosome, death-inducing signaling complex (DISC), and PIDDosome, respectively, for activation. In Drosophila, activation of the caspase-9 homolog Dronc requires assembly of an apoptosome comprised of Dark/Hac-1/Dapaf-1. In Caenorhabditis elegans, activation of the caspase CED-3 is facilitated by the CED-4-apoptosome. Recent biochemical and structural investigation revealed significant insights into the assembly and function of the various apoptosomes. Nonetheless, conclusive mechanisms by which the initiator caspases are activated by the apoptosomes remain elusive. Several models have been proposed to explain the activation process. The induced proximity model summarizes the general process of initiator caspase activation. The proximity-driven dimerization model describes how initiator caspases respond to induced proximity and offers an explanation for their activation. Regardless of how initiator caspases are activated, enhanced activity must be correlated with altered active site conformation. The induced conformation model posits that the activated conformation for the active site of a given initiator caspase is attained through direct interaction with the apoptosome or through homo-oligomerization facilitated by the apoptosome.
Topics: Animals; Apoptosomes; Caspases, Initiator; Dimerization; Enzyme Activation; Humans; Models, Molecular; Protein Conformation
PubMed: 16977332
DOI: 10.1038/sj.cdd.4402028 -
Methods in Enzymology 2008Apoptosome refers to the multimeric protein complex that mediates activation of an initiator caspase at the onset of apoptosis. This chapter describes the assembly of...
Apoptosome refers to the multimeric protein complex that mediates activation of an initiator caspase at the onset of apoptosis. This chapter describes the assembly of three related apoptosomes from mammals, fruit flies, and worms. The assembly of the mammalian apoptosome, which is responsible for the activation of caspase-9, involves Apaf-1 and requires cytochrome c and ATP/dATP binding. Assembly of the apoptosome in Drosophila melanogaster, which activates caspase-9 homologue Dronc, involves the Apaf-1 homologue known as Dark/Hac-1/Dapaf-1. In Caenorhabditis elegans, assembly of the CED-4 apoptosome requires EGL-1-mediated dissociation of CED-9 (a Bcl-2 homologue) from the CED-4-CED-9 complex and subsequent oligomerization of CED-4. Recent biochemical and structural investigation revealed insights into the assembly and function of the various apoptosomes.
Topics: Adenosine Triphosphate; Animals; Apoptosomes; Apoptotic Protease-Activating Factor 1; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Calcium-Binding Proteins; Caspase 9; Cytochromes c; Deoxyadenine Nucleotides; Drosophila Proteins; Drosophila melanogaster; Models, Biological; Protein Binding; Proto-Oncogene Proteins c-bcl-2
PubMed: 18662568
DOI: 10.1016/S0076-6879(08)01407-9 -
Developmental Cell Mar 2002A paper in the February issue of Molecular Cell describes the structure of the apoptosome, a multicomponent death machine, deciphered by cryoelectron microscopy. This... (Review)
Review
A paper in the February issue of Molecular Cell describes the structure of the apoptosome, a multicomponent death machine, deciphered by cryoelectron microscopy. This structure explains the assembly of the machine, the tentative location of the subcomponents, and proposes a mechanism for initiating the death signal.
Topics: Animals; Apoptosis; Caspases
PubMed: 11879630
DOI: 10.1016/s1534-5807(02)00137-5 -
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 -
Clinical Cancer Research : An Official... Jan 2009Apoptosis is a programmed mechanism of cell death that ensures normal development and tissue homeostasis in metazoans. Avoidance of apoptosis is an important contributor... (Review)
Review
Apoptosis is a programmed mechanism of cell death that ensures normal development and tissue homeostasis in metazoans. Avoidance of apoptosis is an important contributor to the survival of tumor cells, and the ability to specifically trigger tumor cell apoptosis is a major goal in cancer treatment. In vertebrates, numerous stress signals engage the intrinsic apoptosis pathway to induce the release of cytochrome c from mitochondria. Cytochrome c binds to apoptosis protease activating factor-1, triggering formation of the apoptosome, a multisubunit protein complex that serves as a platform for caspase activation. In this review we summarize the mechanisms of apoptosome assembly and activation, and our current understanding of the regulation of these processes. We detail the evidence that loss-of-function of the apoptosome pathway may contribute to the development of specific cancers. Finally we discuss recent results showing enhanced sensitivity of some tumor cells to cytochrome c-induced apoptosis, suggesting that agents able to directly or indirectly trigger apoptosome-catalyzed caspase activation in tumor cells could provide new approaches to cancer treatment.
Topics: Adenosine Diphosphate; Animals; Apoptosis; Apoptosomes; Apoptotic Protease-Activating Factor 1; Caspases; Cell-Free System; Cytochromes c; Cytosol; Enzyme Activation; Humans; Mitochondria; Models, Biological; Neoplasms
PubMed: 19147745
DOI: 10.1158/1078-0432.CCR-08-1172 -
Structure (London, England : 1993) Mar 2002Characterization of the apoptosome by cryo-EM reveals a wheel-shaped heptameric assembly involving Apaf-1 and cytochrome c. This structure provides a framework for... (Review)
Review
Characterization of the apoptosome by cryo-EM reveals a wheel-shaped heptameric assembly involving Apaf-1 and cytochrome c. This structure provides a framework for understanding the activation mechanisms of caspase-9, an important initiator caspase in apoptosis.
Topics: Apoptosis; Apoptotic Protease-Activating Factor 1; Caspase 9; Caspases; Cryoelectron Microscopy; Cytochrome c Group; Dimerization; Enzyme Activation; Models, Molecular; Protein Structure, Tertiary; Proteins
PubMed: 12005427
DOI: 10.1016/s0969-2126(02)00732-3