Life and death in peripheral T cells
TL;DR: The concepts of activation-induced cell death (AICD) and activated cell-autonomous death (ACAD) in the regulation of life and death in T cells are discussed.
Abstract: During the course of an immune response, antigen-reactive T cells clonally expand and then are removed by apoptosis to maintain immune homeostasis. Life and death of T cells is determined by multiple factors, such as T-cell receptor triggering, co-stimulation or cytokine signalling, and by molecules, such as caspase-8 (FLICE)-like inhibitory protein (FLIP) and haematopoietic progenitor kinase 1 (HPK1), which regulate the nuclear factor-kappaB (NF-kappaB) pathway. Here, we discuss the concepts of activation-induced cell death (AICD) and activated cell-autonomous death (ACAD) in the regulation of life and death in T cells.
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TL;DR: It is shown that basophils were activated and recruited to the draining lymph nodes specifically in response to TH2–inducing allergen challenge, and it is demonstrated that the basophil was the accessory cell type required for TH2 induction in Response to protease allergens.
Abstract: Both metazoan parasites and simple protein allergens induce T helper type 2 (TH2) immune responses, but the mechanisms by which the innate immune system senses these stimuli are unknown. In addition, the cellular source of cytokines that control TH2 differentiation in vivo has not been defined. Here we showed that basophils were activated and recruited to the draining lymph nodes specifically in response to TH2-inducing allergen challenge. Furthermore, we demonstrate that the basophil was the accessory cell type required for TH2 induction in response to protease allergens. Finally, we show that basophils were directly activated by protease allergens and produced TH2-inducing cytokines, including interleukin 4 and thymic stromal lymphopoietin, which are involved in TH2 differentiation in vivo.
922 citations
TL;DR: This review is aimed to summarize the research results obtained since the last 20 years and to highlight the recently discovered molecular mechanisms of Scutellaria baicalensis.
747 citations
TL;DR: A quantitative analysis of cysteine-reactive small-molecule fragments screened against thousands of proteins in human proteomes and cells provides a greatly expanded portrait of the ligandable proteome and furnishes compounds that can illuminate protein functions in native biological systems.
Abstract: Small molecules are powerful tools for investigating protein function and can serve as leads for new therapeutics. Most human proteins, however, lack small-molecule ligands, and entire protein classes are considered 'undruggable'. Fragment-based ligand discovery can identify small-molecule probes for proteins that have proven difficult to target using high-throughput screening of complex compound libraries. Although reversibly binding ligands are commonly pursued, covalent fragments provide an alternative route to small-molecule probes, including those that can access regions of proteins that are difficult to target through binding affinity alone. Here we report a quantitative analysis of cysteine-reactive small-molecule fragments screened against thousands of proteins in human proteomes and cells. Covalent ligands were identified for >700 cysteines found in both druggable proteins and proteins deficient in chemical probes, including transcription factors, adaptor/scaffolding proteins, and uncharacterized proteins. Among the atypical ligand-protein interactions discovered were compounds that react preferentially with pro- (inactive) caspases. We used these ligands to distinguish extrinsic apoptosis pathways in human cell lines versus primary human T cells, showing that the former is largely mediated by caspase-8 while the latter depends on both caspase-8 and -10. Fragment-based covalent ligand discovery provides a greatly expanded portrait of the ligandable proteome and furnishes compounds that can illuminate protein functions in native biological systems.
564 citations
TL;DR: Together with other DR signal transducers, FADD and TRADD participate in functional complexes assembled by certain non-DR immune cell receptors, such as pattern-recognition receptors, which may provide important nodes of coordination in immune signaling networks.
Abstract: Death receptors (DRs) are members of the tumor necrosis factor receptor superfamily that possess a cytoplasmic death domain (DD). DRs regulate important operational and homeostatic aspects of the immune system. They transmit signals through apical protein complexes, which are nucleated by the DD adaptors FADD and TRADD, to control cellular outcomes that range from apoptosis to gene activation. FADD and TRADD also nucleate several distal signaling complexes, which mediate cross-talk between distinct DR signaling pathways. Moreover, together with other DR signal transducers, FADD and TRADD participate in functional complexes assembled by certain non-DR immune cell receptors, such as pattern-recognition receptors. Thus, DR signal transducers may provide important nodes of coordination in immune signaling networks.
518 citations
TL;DR: A critical role is demonstrated for NF-κB signaling in the actions of IL-1β and stress, which is identified as a critical mediator of the antineurogenic and behavioral actions of stress and suggests previously undescribed therapeutical targets for depression.
Abstract: Proinflammatory cytokines, such as IL-1β, have been implicated in the cellular and behavioral effects of stress and in mood disorders, although the downstream signaling pathways underlying these effects have not been determined. In the present study, we demonstrate a critical role for NF-κB signaling in the actions of IL-1β and stress. Stress inhibition of neurogenesis in the adult hippocampus, which has been implicated in the prodepressive effects of stress, is blocked by administration of an inhibitor of NF-κB. Further analysis reveals that stress activates NF-κB signaling and decreases proliferation of neural stem-like cells but not early neural progenitor cells in the adult hippocampus. We also find that depressive-like behaviors caused by exposure to chronic stress are mediated by NF-κB signaling. Together, these data identify NF-κB signaling as a critical mediator of the antineurogenic and behavioral actions of stress and suggest previously undescribed therapeutical targets for depression.
517 citations
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TL;DR: This work has shown that understanding caspase regulation is intimately linked to the ability to rationally manipulate apoptosis for therapeutic gain.
Abstract: Apoptosis, an evolutionarily conserved form of cell suicide, requires specialized machinery. The central component of this machinery is a proteolytic system involving a family of proteases called caspases. These enzymes participate in a cascade that is triggered in response to proapoptotic signals and culminates in cleavage of a set of proteins, resulting in disassembly of the cell. Understanding caspase regulation is intimately linked to the ability to rationally manipulate apoptosis for therapeutic gain.
6,924 citations
"Life and death in peripheral T cell..." refers background in this paper
...All caspases are produced by cells as catalytically inactive zymogens and undergo proteolytic processing during activatio...
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TL;DR: Apoptosis is a cell suicide mechanism that enables metazoans to control cell number in tissues and to eliminate individual cells that threaten the animal's survival.
Abstract: Apoptosis is a cell suicide mechanism that enables metazoans to control cell number in tissues and to eliminate individual cells that threaten the animal's survival. Certain cells have unique sensors, termed death receptors, on their surface. Death receptors detect the presence of extracellular death signals and, in response, they rapidly ignite the cell's intrinsic apoptosis machinery.
5,968 citations
"Life and death in peripheral T cell..." refers background in this paper
...The cell-death receptors, defined by the presence of a DD, include several members of the TNF receptor (TNFR) superfamily: TNFR1, CD95 (also known as FAS or APO-1), TRAIL receptor-1 (TRAILR1), TRAILR2, death receptor 3 (DR3) and DR...
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TL;DR: In this article, the authors found that doubly deficient cells are resistant to multiple apoptotic stimuli that act through disruption of mitochondrial function: staurosporine, ultraviolet radiation, growth factor deprivation, etoposide, and the endoplasmic reticulum stress stimuli thapsigargin and tunicamycin.
Abstract: Multiple death signals influence mitochondria during apoptosis, yet the critical initiating event for mitochondrial dysfunction in vivo has been unclear. tBID, the caspase-activated form of a "BH3-domain-only" BCL-2 family member, triggers the homooligomerization of "multidomain" conserved proapoptotic family members BAK or BAX, resulting in the release of cytochrome c from mitochondria. We find that cells lacking both Bax and Bak, but not cells lacking only one of these components, are completely resistant to tBID-induced cytochrome c release and apoptosis. Moreover, doubly deficient cells are resistant to multiple apoptotic stimuli that act through disruption of mitochondrial function: staurosporine, ultraviolet radiation, growth factor deprivation, etoposide, and the endoplasmic reticulum stress stimuli thapsigargin and tunicamycin. Thus, activation of a "multidomain" proapoptotic member, BAX or BAK, appears to be an essential gateway to mitochondrial dysfunction required for cell death in response to diverse stimuli.
3,942 citations
"Life and death in peripheral T cell..." refers background in this paper
...In this context, it was shown that T cells from BCL-2-transgenic mice, as well as T cells from mice deficient in both BAX and BAK are not protected from CD95-mediated apoptosi...
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TL;DR: An overview of established NF-kappaB signaling pathways is provided with focus on the current state of research into the mechanisms that regulate IKK activation and NF- kappaB transcriptional activity.
Abstract: The transcription factor NF-kappaB has been the focus of intense investigation for nearly two decades. Over this period, considerable progress has been made in determining the function and regulation of NF-kappaB, although there are nuances in this important signaling pathway that still remain to be understood. The challenge now is to reconcile the regulatory complexity in this pathway with the complexity of responses in which NF-kappaB family members play important roles. In this review, we provide an overview of established NF-kappaB signaling pathways with focus on the current state of research into the mechanisms that regulate IKK activation and NF-kappaB transcriptional activity.
3,829 citations
"Life and death in peripheral T cell..." refers background in this paper
...The NF-κB family of transcription factors regulates the expression of genes crucial for innate and adaptive immune responses, cell growth and apoptosi...
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TL;DR: In this paper, a review of recent progress as well as unanswered questions regarding the regulation and function of NF-kappaB and IKK is presented, focusing on recent progress and unanswered questions.
3,342 citations