Active cell death, in its many forms, is a fundamental biological process. Studies over the past several decades have explored the functions and consequences of cellular demise and elucidated several ...of the key cell death pathways. Here, I pose five questions, or riddles, that might provide a guide to the next decade of cell death research. Focusing mainly on four types of active cell death (apoptosis, necroptosis, pyroptosis, and ferroptosis) mainly in mammals, this Perspective explores the possible research directions that might answer these riddles, or at least prompt new ones.
Active cell death, in its many forms, is a fundamental biological process, and its study over the past several decades has provided key insights into the molecular processes, functions, and consequences responsible. Here, I pose five questions, or riddles, that might provide a guide to the next decade of cell death research. Focusing mainly on four types of active cell death (apoptosis, necroptosis, pyroptosis, and ferroptosis) mainly in mammals, this Perspective explores the possible research directions that might answer these riddles, or at least prompt new ones.
Summary
Roles for cell death in development, homeostasis, and the control of infections and cancer have long been recognized. Although excessive cell damage results in passive necrosis, cells can be ...triggered to engage molecular programs that result in cell death. Such triggers include cellular stress, oncogenic signals that engage tumor suppressor mechanisms, pathogen insults, and immune mechanisms. The best‐known forms of programmed cell death are apoptosis and a recently recognized regulated necrosis termed necroptosis. Of the two best understood pathways of apoptosis, the extrinsic and intrinsic (mitochondrial) pathways, the former is induced by the ligation of death receptors, a subset of the TNF receptor (TNFR) superfamily. Ligation of these death receptors can also induce necroptosis. The extrinsic apoptosis and necroptosis pathways regulate each other and their balance determines whether cells live. Integral in the regulation and initiation of death receptor‐mediated activation of programmed cell death is the aspartate‐specific cysteine protease (caspase)‐8. This review describes the role of caspase‐8 in the initiation of extrinsic apoptosis execution and the mechanism by which caspase‐8 inhibits necroptosis. The importance of caspase‐8 in the development and homeostasis and the way that dysfunctional caspase‐8 may contribute to the development of malignancies in mice and humans are also explored.
The health of metazoan organisms requires an effective response to organellar and cellular damage either by repair of such damage and/or by elimination of the damaged parts of the cells or the ...damaged cell in its entirety. Here, we consider the progress that has been made in the last few decades in determining the fates of damaged organelles and damaged cells through discrete, but genetically overlapping, pathways involving the selective autophagy and cell death machinery. We further discuss the ways in which the autophagy machinery may impact the clearance and consequences of dying cells for host physiology. Failure in the proper removal of damaged organelles and/or damaged cells by selective autophagy and cell death processes is likely to contribute to developmental abnormalities, cancer, aging, inflammation, and other diseases.
Metabolic control of cell death Green, Douglas R.; Galluzzi, Lorenzo; Kroemer, Guido
Science (American Association for the Advancement of Science),
09/2014, Volume:
345, Issue:
6203
Journal Article
Peer reviewed
Open access
Beyond their contribution to basic metabolism, the major cellular organelles, in particular mitochondria, can determine whether cells respond to stress in an adaptive or suicidal manner. Thus, ...mitochondria can continuously adapt their shape to changing bioenergetic demands as they are subjected to quality control by autophagy, or they can undergo a lethal permeabilization process that initiates apoptosis. Along similar lines, multiple proteins involved in metabolic circuitries, including oxidative phosphorylation and transport of metabolites across membranes, may participate in the regulated or catastrophic dismantling of organelles. Many factors that were initially characterized as cell death regulators are now known to physically or functionally interact with metabolic enzymes. Thus, several metabolic cues regulate the propensity of cells to activate self-destructive programs, in part by acting on nutrient sensors. This suggests the existence of “metabolic checkpoints” that dictate cell fate in response to metabolic fluctuations. Here, we discuss recent insights into the intersection between metabolism and cell death regulation that have major implications for the comprehension and manipulation of unwarranted cell loss.
Classically, canonical autophagy has been considered a survival mechanism initiated in response to nutrient insufficiency. We now understand that autophagy functions in multiple scenarios where it is ...necessary to maintain homeostasis. Recent evidence has established that a variety of non-canonical functions for autophagy proteins are mechanistically and functionally distinct from autophagy. LC3-associated phagocytosis (LAP) is one such novel function for autophagy proteins and is a contributor to immune regulation and inflammatory responses across various cell and tissue types. Characterized by the conjugation of LC3 family proteins to phagosome membranes, LAP uses a portion of the canonical autophagy machinery, following ligation of surface receptors that recognize a variety of cargos including pathogens, dying cells, soluble ligands and protein aggregates. However, instead of affecting canonical autophagy, manipulation of the LAP pathway
alters immune activation and inflammatory responses. In this Cell Science at a Glance article and the accompanying poster, we detail the divergence of this distinctive mechanism from that of canonical autophagy by comparing and contrasting shared and unique components of each pathway.
The c-Myc HLH-bZIP protein has been implicated in physiological or pathological growth, proliferation, apoptosis, metabolism, and differentiation at the cellular, tissue, or organismal levels via ...regulation of numerous target genes. No principle yet unifies Myc action due partly to an incomplete inventory and functional accounting of Myc’s targets. To observe Myc target expression and function in a system where Myc is temporally and physiologically regulated, the transcriptomes and the genome-wide distributions of Myc, RNA polymerase II, and chromatin modifications were compared during lymphocyte activation and in ES cells as well. A remarkably simple rule emerged from this quantitative analysis: Myc is not an on-off specifier of gene activity, but is a nonlinear amplifier of expression, acting universally at active genes, except for immediate early genes that are strongly induced before Myc. This rule of Myc action explains the vast majority of Myc biology observed in literature.
Receptor Interacting Protein Kinase-1 (RIPK1), a key player in inflammation and cell death, assumes opposite functions depending on the cellular context and its posttranslational modifications. ...Genetic evidence supported by biochemical and cellular biology approaches sheds light on the circumstances in which RIPK1 promotes or inhibits these processes.
Receptor Interacting Protein Kinase-1 (RIPK1), a key player in inflammation and cell death, assumes opposite functions depending on the cellular context and its posttranslational modifications. Genetic evidence supported by biochemical and cellular biology approaches sheds light on the circumstances in which RIPK1 promotes or inhibits these processes.
The clearance of dead cells by efferocytosis Boada-Romero, Emilio; Martinez, Jennifer; Heckmann, Bradlee L ...
Nature reviews. Molecular cell biology,
07/2020, Volume:
21, Issue:
7
Journal Article
Peer reviewed
Open access
Multiple modes of cell death have been identified, each with a unique function and each induced in a setting-dependent manner. As billions of cells die during mammalian embryogenesis and daily in ...adult organisms, clearing dead cells and associated cellular debris is important in physiology. In this Review, we present an overview of the phagocytosis of dead and dying cells, a process known as efferocytosis. Efferocytosis is performed by macrophages and to a lesser extent by other 'professional' phagocytes (such as monocytes and dendritic cells) and 'non-professional' phagocytes, such as epithelial cells. Recent discoveries have shed light on this process and how it functions to maintain tissue homeostasis, tissue repair and organismal health. Here, we outline the mechanisms of efferocytosis, from the recognition of dying cells through to phagocytic engulfment and homeostatic resolution, and highlight the pathophysiological consequences that can arise when this process is abrogated.
Alterations of mitochondrial functions are linked to multiple degenerative or acute diseases. As mitochondria age in our cells, they become progressively inefficient and potentially toxic, and acute ...damage can trigger the permeabilization of mitochondrial membranes to initiate apoptosis or necrosis. Moreover, mitochondria have an important role in pro-inflammatory signaling. Autophagic turnover of cellular constituents, be it general or specific for mitochondria (mitophagy), eliminates dysfunctional or damaged mitochondria, thus counteracting degeneration, dampening inflammation, and preventing unwarranted cell loss. Decreased expression of genes that regulate autophagy or mitophagy can cause degenerative diseases in which deficient quality control results in inflammation and the death of cell populations. Thus, a combination of mitochondrial dysfunction and insufficient autophagy may contribute to multiple aging-associated pathologies.
Clustered regularly interspaced palindromic repeats (CRISPR)-associated (Cas9) technology has proven a formidable addition to our armory of approaches for genomic editing. Derived from pathways in ...archaea and bacteria that mediate the resistance to exogenous genomic material, the CRISPR-Cas9 system utilizes a short single guide RNA (sgRNA) to direct the endonuclease Cas9 to virtually anywhere in the genome. Upon targeting, Cas9 generates DNA double-strand breaks (DSBs) and facilitates the repair or insertion of mutations, insertion of recombinase recognition sites, or large DNA elements. Here, we discuss the practical advantages of the CRISPR-Cas9 system over conventional and other nuclease-based targeting technologies and provide suggestions for the use of this technology to address immunological questions.
CRISPR-Cas9 is a targetable nuclease technology that allows genomic manipulation in many species. Green and colleagues discuss the practical advantages of the CRISPR-Cas9 system over conventional and other nuclease-based targeting technologies and provide suggestions for the use of this technology to address immunological questions.
PDF
