The Experts below are selected from a list of 3735 Experts worldwide ranked by ideXlab platform
Junying Yuan - One of the best experts on this subject based on the ideXlab platform.
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necroptosis and RIPK1 mediated neuroinflammation in cns diseases
Nature Reviews Neuroscience, 2019Co-Authors: Junying Yuan, Palak Amin, Dimitry OfengeimAbstract:Apoptosis is crucial for the normal development of the nervous system, whereas neurons in the adult CNS are relatively resistant to this form of cell death. However, under pathological conditions, upregulation of death receptor family ligands, such as tumour necrosis factor (TNF), can sensitize cells in the CNS to apoptosis and a form of regulated necrotic cell death known as necroptosis that is mediated by receptor-interacting protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain-like protein (MLKL). Necroptosis promotes further cell death and neuroinflammation in the pathogenesis of several neurodegenerative diseases, including multiple sclerosis, amyotrophic lateral sclerosis, Parkinson disease and Alzheimer disease. In this Review, we outline the evidence implicating necroptosis in these neurological diseases and suggest that targeting RIPK1 might help to inhibit multiple cell death pathways and ameliorate neuroinflammation. Necroptosis is a form of cell death mediated by receptor-interacting protein kinase 1 (RIPK1), and is observed in several CNS disorders. Here, Yuan, Amin and Ofengeim give an overview of necroptosis in the CNS and explain its relationship with inflammation in CNS disorders.
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Necroptosis and RIPK1-mediated neuroinflammation in CNS diseases.
Nature Reviews Neuroscience, 2018Co-Authors: Junying Yuan, Palak Amin, Dimitry OfengeimAbstract:Apoptosis is crucial for the normal development of the nervous system, whereas neurons in the adult CNS are relatively resistant to this form of cell death. However, under pathological conditions, upregulation of death receptor family ligands, such as tumour necrosis factor (TNF), can sensitize cells in the CNS to apoptosis and a form of regulated necrotic cell death known as necroptosis that is mediated by receptor-interacting protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain-like protein (MLKL). Necroptosis promotes further cell death and neuroinflammation in the pathogenesis of several neurodegenerative diseases, including multiple sclerosis, amyotrophic lateral sclerosis, Parkinson disease and Alzheimer disease. In this Review, we outline the evidence implicating necroptosis in these neurological diseases and suggest that targeting RIPK1 might help to inhibit multiple cell death pathways and ameliorate neuroinflammation.
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abin 1 regulates RIPK1 activation by linking met1 ubiquitylation with lys63 deubiquitylation in tnf rsc
Nature Cell Biology, 2018Co-Authors: Slawomir A Dziedzic, Derek W. Abbott, Junying Yuan, Ayaz Najafov, Adnan K Mookhtiar, Palak Amin, Zhenyi Su, Vica Jean BarrettAbstract:Ubiquitylation of the TNFR1 signalling complex (TNF-RSC) controls the activation of RIPK1, a kinase critically involved in mediating multiple TNFα-activated deleterious events. However, the molecular mechanism that coordinates different types of ubiquitylation modification to regulate the activation of RIPK1 kinase remains unclear. Here, we show that ABIN-1/NAF-1, a ubiquitin-binding protein, is recruited rapidly into TNF-RSC in a manner dependent on the Met1-ubiquitylating complex LUBAC to regulate the recruitment of A20 to control Lys63 deubiquitylation of RIPK1. ABIN-1 deficiency reduces the recruitment of A20 and licenses cells to die through necroptosis by promoting Lys63 ubiquitylation and activation of RIPK1 with TNFα stimulation under conditions that would otherwise exclusively activate apoptosis in wild-type cells. Inhibition of RIPK1 kinase and RIPK3 deficiency block the embryonic lethality of Abin-1 –/– mice. We propose that ABIN-1 provides a critical link between Met1 ubiquitylation mediated by the LUBAC complex and Lys63 deubiquitylation by phospho-A20 to modulate the activation of RIPK1.
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peli1 functions as a dual modulator of necroptosis and apoptosis by regulating ubiquitination of RIPK1 and mrna levels of c flip
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Junying Yuan, Ying Li, Huibing Wang, Huyan Meng, Xingyan Li, Kangyun Dong, Adnan K MookhtiarAbstract:Apoptosis and necroptosis are two distinct cell death mechanisms that may be activated in cells on stimulation by TNFα. It is still unclear, however, how apoptosis and necroptosis may be differentially regulated. Here we screened for E3 ubiquitin ligases that could mediate necroptosis. We found that deficiency of Pellino 1 (PELI1), an E3 ubiquitin ligase, blocked necroptosis. We show that PELI1 mediates K63 ubiquitination on K115 of RIPK1 in a kinase-dependent manner during necroptosis. Ubiquitination of RIPK1 by PELI1 promotes the formation of necrosome and execution of necroptosis. Although PELI1 is not directly involved in mediating the activation of RIPK1, it is indispensable for promoting the binding of activated RIPK1 with its downstream mediator RIPK3 to promote the activation of RIPK3 and MLKL. Inhibition of RIPK1 kinase activity blocks PELI1-mediated ubiquitination of RIPK1 in necroptosis. However, we show that PELI1 deficiency sensitizes cells to both RIPK1-dependent and RIPK1-independent apoptosis as a result of down-regulated expression of c-FLIP, an inhibitor of caspase-8. Finally, we show that Peli1 −/− mice are sensitized to TNFα-induced apoptosis. Thus, PELI1 is a key modulator of RIPK1 that differentially controls the activation of necroptosis and apoptosis.
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regulation of RIPK1 activation by tak1 mediated phosphorylation dictates apoptosis and necroptosis
Nature Communications, 2017Co-Authors: Jiefei Geng, Ayaz Najafov, Adnan K Mookhtiar, Palak Amin, Amanda Tomie Ouchida, Heng Zhao, Daichao Xu, Bing Shan, Shizuo Akira, Junying YuanAbstract:Stimulation of TNFR1 by TNFα can promote three distinct alternative mechanisms of cell death: necroptosis, RIPK1-independent and -dependent apoptosis. How cells decide which way to die is unclear. Here, we report that TNFα-induced phosphorylation of RIPK1 in the intermediate domain by TAK1 plays a key role in regulating this critical decision. Using phospho-Ser321 as a marker, we show that the transient phosphorylation of RIPK1 intermediate domain induced by TNFα leads to RIPK1-independent apoptosis when NF-κB activation is inhibited by cycloheximide. On the other hand, blocking Ser321 phosphorylation promotes RIPK1 activation and its interaction with FADD to mediate RIPK1-dependent apoptosis (RDA). Finally, sustained phosphorylation of RIPK1 intermediate domain at multiple sites by TAK1 promotes its interaction with RIPK3 and necroptosis. Thus, absent, transient and sustained levels of TAK1-mediated RIPK1 phosphorylation may represent distinct states in TNF-RSC to dictate the activation of three alternative cell death mechanisms, RDA, RIPK1-independent apoptosis and necroptosis. TNFα can promote three distinct mechanisms of cell death: necroptosis, RIPK1-independent and dependent apoptosis. Here the authors show that TNFα-induced phosphorylation of RIPK1 in the intermediate domain by TAK1 plays a key role in regulating this decision.
Peter Vandenabeele - One of the best experts on this subject based on the ideXlab platform.
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Intermediate Domain of Receptor-interacting Protein Kinase 1 (RIPK1) Determines Switch between Necroptosis and RIPK1
2020Co-Authors: Linde Duprez, Yves Dondelinger, Mathieu J M Bertrand, Tom Vanden Berghe, Nele Festjens, Peter VandenabeeleAbstract:We developed a cellular model to identify RIPK1 targets during RIPK1-dependent apoptosis.Receptor-interacting protein kinase 1 (RIPK1) is an impor-tant component of the tumor necrosis factor receptor 1(TNFR1) signaling pathway. Depending on the cell type andconditions, RIPK1 mediates MAPK and NF- B activation aswell as cell death. Using a mutant form of RIPK1 (RIPK1 ID)lacking the intermediate domain (ID), we confirm the require-ment of this domain for activation of these signaling events.Moreover, expression of RIPK1 ID resulted in enhancedrecruitment of caspase-8 to the TNFR1 complex II componentFas-associated death domain (FADD), which allowed a shiftfromTNF-inducednecroptosistoapoptosisinL929cells.Addi-tion of the RIPK1 kinase inhibitor necrostatin-1 stronglyreducedrecruitmentofRIPK1andcaspase-8toFADDandsub-sequentapoptosis,indicatingaroleforRIPK1kinaseactivityinapoptotic complex formation. Our study shows that RIPK1 hasananti-apoptoticfunctionresidinginitsIDanddemonstratesacellularsystemasanelegantgeneticmodelforRIPK1kinase-de-pendentapoptosisthat,incontrasttotheSmacmimeticmodel,doesnotrelyondepletionofcellularinhibitorofapoptosispro-tein 1 and 2 (cIAP1/2).
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inhibitors targeting RIPK1 ripk3 old and new drugs
Trends in Pharmacological Sciences, 2020Co-Authors: Sofie Martens, Sam Hofmans, Wim Declercq, Koen Augustyns, Peter VandenabeeleAbstract:The scaffolding function of receptor-interacting protein kinase 1 (RIPK1) regulates prosurvival signaling and inflammatory gene expression, while its kinase activity mediates both apoptosis and necroptosis; the latter involving RIPK3 kinase activity. The mutual transition between the scaffold and kinase functions of RIPK1 is regulated by (de)ubiquitylation and (de)phosphorylation. RIPK1-mediated cell death leads to disruption of epithelial barriers and/or release of damage-associated molecular patterns (DAMPs), cytokines, and chemokines, propagating inflammatory and degenerative diseases. Many drug development programs have pursued targeting RIPK1, and to a lesser extent RIPK3 kinase activity. In this review, we classify existing and novel small-molecule drugs based on their pharmacodynamic (PD) type I, II, and III binding mode. Finally, we discuss their applicability and therapeutic potential in inflammatory and degenerative experimental disease models.
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Inhibitors Targeting RIPK1/RIPK3: Old and New Drugs
Trends in Pharmacological Sciences, 2020Co-Authors: Sofie Martens, Sam Hofmans, Wim Declercq, Koen Augustyns, Peter VandenabeeleAbstract:The scaffolding function of receptor-interacting protein kinase 1 (RIPK1) regulates prosurvival signaling and inflammatory gene expression, while its kinase activity mediates both apoptosis and necroptosis; the latter involving RIPK3 kinase activity. The mutual transition between the scaffold and kinase functions of RIPK1 is regulated by (de)ubiquitylation and (de)phosphorylation. RIPK1-mediated cell death leads to disruption of epithelial barriers and/or release of damage-associated molecular patterns (DAMPs), cytokines, and chemokines, propagating inflammatory and degenerative diseases. Many drug development programs have pursued targeting RIPK1, and to a lesser extent RIPK3 kinase activity. In this review, we classify existing and novel small-molecule drugs based on their pharmacodynamic (PD) type I, II, and III binding mode. Finally, we discuss their applicability and therapeutic potential in inflammatory and degenerative experimental disease models.
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RIPK1 dependent cell death a novel target of the aurora kinase inhibitor tozasertib vx 680
Cell Death and Disease, 2018Co-Authors: Sofie Martens, Nozomi Takahashi, Vera Goossens, Sam Hofmans, Koen Augustyns, Lars Devisscher, Polien Claeys, Marnik Vuylsteke, Peter VandenabeeleAbstract:The Aurora kinase family (Aurora A, B and C) are crucial regulators of several mitotic events, including cytokinesis. Increased expression of these kinases is associated with tumorigenesis and several compounds targeting Aurora kinase are under evaluation in clinical trials (a.o. AT9283, AZD1152, Danusertib, MLN8054). Here, we demonstrate that the pan-Aurora kinase inhibitor Tozasertib (VX-680 and MK-0457) not only causes cytokinesis defects through Aurora kinase inhibition, but is also a potent inhibitor of necroptosis, a cell death process regulated and executed by the RIPK1, RIPK3 and MLKL signalling axis. Tozasertib’s potency to inhibit RIPK1-dependent necroptosis and to block cytokinesis in cells is in the same concentration range, with an IC50 of 1.06 µM and 0.554 µM, respectively. A structure activity relationship (SAR) analysis of 67 Tozasertib analogues, modified at 4 different positions, allowed the identification of analogues that showed increased specificity for either cytokinesis inhibition or for necroptosis inhibition, reflecting more specific inhibition of Aurora kinase or RIPK1, respectively. These results also suggested that RIPK1 and Aurora kinases are functionally non-interacting targets of Tozasertib and its analogues. Indeed, more specific Aurora kinase inhibitors did not show any effect in necroptosis and Necrostatin-1s treatment did not result in cytokinesis defects, demonstrating that both cellular processes are not interrelated. Finally, Tozasertib inhibited recombinant human RIPK1, human Aurora A and human Aurora B kinase activity, but not RIPK3. The potency ranking of the newly derived Tozasertib analogues and their specificity profile, as observed in cellular assays, coincide with ADP-Glo recombinant kinase activity assays. Overall, we show that Tozasertib not only targets Aurora kinases but also RIPK1 independently, and that we could generate analogues with increased selectivity to RIPK1 or Aurora kinases, respectively.
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regulation of RIPK1 s cell death function by phosphorylation
Cell Cycle, 2016Co-Authors: Yves Dondelinger, Peter Vandenabeele, Mathieu J M BertrandAbstract:RIPK1 is a key molecule determining cellular fate downstream of several innate immune receptors. It is a serine/threonine kinase consisting of an N-terminal kinase domain linked by a largely unstructured intermediate domain to a C-terminal death domain (Fig. 1). In the TNF signaling pathway, RIPK1 paradoxically promotes cell survival as well as cell death.1,2 These opposite cellular functions are mediated by 2 distinct faces of RIPK1. Upon binding of TNF to TNFR1, RIPK1 is recruited to the receptor complex I where it acts as a scaffold protein promoting cell survival, in part, by activating the canonical NF-κB pathway. Specific conditions can however activate RIPK1, and its kinase activity then regulates assembly of 2 possible cytosolic death-inducing complexes, namely complex IIb (RIPK1-FADD-Caspase-8) and the necrosome (RIPK1-RIPK3-MLKL). These complexes respectively drive TNF-mediated apoptosis or necroptosis, a regulated form of necrosis. The precise molecular mechanism(s) controlling RIPK1 activation is (are) currently unknown. Similarly, how RIPK1 kinase activity contributes to both cell death processes still remains unclear. Despite this lack of understanding, it is evident that RIPK1 can play a dual role downstream of TNFR1 and that its kinase activity needs tight repression to avoid unnecessary damage to the organism.
Le G Moignemuller - One of the best experts on this subject based on the ideXlab platform.
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trail induces necroptosis involving RIPK1 ripk3 dependent parp 1 activation
Cell Death & Differentiation, 2012Co-Authors: S Jouanlanhouet, Muhammad Imran Arshad, Claire Piquetpellorce, Corinne Martinchouly, Le G MoignemullerAbstract:Although TRAIL (tumor necrosis factor (TNF)-related apoptosis inducing ligand) is a well-known apoptosis inducer, we have previously demonstrated that acidic extracellular pH (pHe) switches TRAIL-induced apoptosis to regulated necrosis (or necroptosis) in human HT29 colon and HepG2 liver cancer cells. Here, we investigated the role of RIPK1 (receptor interacting protein kinase 1), RIPK3 and PARP-1 (poly (ADP-ribose) polymerase-1) in TRAIL-induced necroptosis in vitro and in concanavalin A (Con A)-induced murine hepatitis. Pretreatment of HT29 or HepG2 with pharmacological inhibitors of RIPK1 or PARP-1 (Nec-1 or PJ-34, respectively), or transient transfection with siRNAs against RIPK1 or RIPK3, inhibited both TRAIL-induced necroptosis and PARP-1-dependent intracellular ATP depletion demonstrating that RIPK1 and RIPK3 were involved upstream of PARP-1 activation and ATP depletion. In the mouse model of Con A-induced hepatitis, where death of mouse hepatocytes is dependent on TRAIL and NKT (Natural Killer T) cells, PARP-1 activity was positively correlated with liver injury and hepatitis was prevented both by Nec-1 or PJ-34. These data provide new insights into TRAIL-induced necroptosis with PARP-1 being active effector downstream of RIPK1/RIPK3 initiators and suggest that pharmacological inhibitors of RIPKs and PARP-1 could be new treatment options for immune-mediated hepatitis.
Manolis Pasparakis - One of the best experts on this subject based on the ideXlab platform.
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RIPK1 and death receptor signaling drive biliary damage and early liver tumorigenesis in mice with chronic hepatobiliary injury
Cell Death & Differentiation, 2019Co-Authors: Santosh Krishnasubramanian, Marietta Armaka, George Kollias, Manolis Pasparakis, Stephan Singer, Jesus M Banales, Kerstin Holzer, Peter Schirmacher, Henning Walczak, Vangelis KondylisAbstract:Hepatocyte apoptosis is intrinsically linked to chronic liver disease and hepatocarcinogenesis. Conversely, necroptosis of hepatocytes and other liver cell types and its relevance for liver disease is debated. Using liver parenchymal cell (LPC)-specific TGF-beta-activated kinase 1 (TAK1)-deficient (TAK1LPC-KO) mice, which exhibit spontaneous hepatocellular and biliary damage, hepatitis, and early hepatocarcinogenesis, we have investigated the contribution of apoptosis and necroptosis in hepatocyte and cholangiocyte death and their impact on liver disease progression. Here, we provide in vivo evidence showing that TAK1-deficient cholangiocytes undergo spontaneous necroptosis induced primarily by TNFR1 and dependent on RIPK1 kinase activity, RIPK3, and NEMO. In contrast, TAK1-deficient hepatocytes die by FADD-dependent apoptosis, which is not significantly inhibited by LPC-specific RIPK1 deficiency, inhibition of RIPK1 kinase activity, RIPK3 deficiency or combined LPC-specific deletion of TNFR1, TRAILR, and Fas. Accordingly, normal mouse cholangiocytes can undergo necroptosis, while primary hepatocytes are resistant to it and die exclusively by apoptosis upon treatment with cell death-inducing stimuli in vitro, likely due to the differential expression of RIPK3. Interestingly, the genetic modifications that conferred protection from biliary damage also prevented the spontaneous lethality that was often observed in TAK1LPC-KO mice. In the presence of chronic hepatocyte apoptosis, preventing biliary damage delayed but did not avert hepatocarcinogenesis. On the contrary, inhibition of hepatocyte apoptosis fully prevented liver tumorigenesis even in mice with extensive biliary damage. Altogether, our results suggest that using RIPK1 kinase activity inhibitors could be therapeutically useful for cholestatic liver disease patients.
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the p55tnfr ikk2 ripk3 axis orchestrates arthritis by regulating death and inflammatory pathways in synovial fibroblasts
Nature Communications, 2018Co-Authors: Marietta Armaka, Caroline Ospelt, Manolis Pasparakis, George KolliasAbstract:NFκB activation and regulated cell death are important in tissue homeostasis, inflammation and pathogenesis. Here we show the role of the p55TNFR–IKK2l–Ripk3 axis in the regulation of synovial fibroblast homeostasis and pathogenesis in TNF-mediated mouse models of arthritis. Mesenchymal-specific p55TNFR triggering is indispensable for arthritis in acute and chronic TNF-dependent models. IKK2 in joint mesenchymal cells is necessary for the development of cartilage destruction and bone erosion; however, in its absence synovitis still develops. IKK2 deletion affects arthritic and antiapoptotic gene expression leading to hypersensitization of synovial fibroblasts to TNF/RIPK1-mediated death via district mechanisms, depending on acute or chronic TNF signals. Moreover, Ripk3 is dispensable for TNF-mediated arthritis, yet it is required for synovitis in mice with mesenchymal-specific IKK2 deletion. These results demonstrate that p55TNFR–IKK2–Ripk3 signalling orchestrates arthritogenic and death responses in synovial fibroblasts, suggesting that therapeutic manipulation of this pathway in arthritis may require combinatorial blockade of both IKK2 and Ripk3 signals. TNF is a major therapeutic target for rheumatoid arthritis (RA) and synovial fibroblasts are central to the pathogenesis of RA. Here the authors dissect TNF-induced death and activation signalling in RA synovial fibroblasts and TNF-driven arthritis and indicate that a successful therapeutic strategy might be to target both IKK2 and RIPK3 at the same time.
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dendritic cell RIPK1 maintains immune homeostasis by preventing inflammation and autoimmunity
Journal of Immunology, 2018Co-Authors: Joanne A Odonnell, Manolis Pasparakis, Justine E Roderick, Nicole Hermance, Matija Zelic, Jesse Lehman, Dalia Martinezmarin, Ciara Doran, Stephen Lyle, Katherine A FitzgeraldAbstract:Necroptosis is a form of cell death associated with inflammation; however, the biological consequences of chronic necroptosis are unknown. Necroptosis is mediated by RIPK1, RIPK3, and MLKL kinases but in hematopoietic cells RIPK1 has anti-inflammatory roles and functions to prevent necroptosis. Here we interrogate the consequences of chronic necroptosis on immune homeostasis by deleting RIPK1 in mouse dendritic cells. We demonstrate that deregulated necroptosis results in systemic inflammation, tissue fibrosis, and autoimmunity. We show that inflammation and autoimmunity are prevented upon expression of kinase inactive RIPK1 or deletion of RIPK3 or MLKL. We provide evidence that the inflammation is not driven by microbial ligands, but depends on the release of danger-associated molecular patterns and MyD88-dependent signaling. Importantly, although the inflammation is independent of type I IFN and the nucleic acid sensing TLRs, blocking these pathways rescues the autoimmunity. These mouse genetic studies reveal that chronic necroptosis may underlie human fibrotic and autoimmune disorders.
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the interplay of ikk nf κb and RIPK1 signaling in the regulation of cell death tissue homeostasis and inflammation
Immunological Reviews, 2017Co-Authors: Vangelis Kondylis, Katerina Vlantis, Snehlata Kumari, Manolis PasparakisAbstract:Summary Regulated cell death pathways have important functions in host defense and tissue homeostasis. Studies in genetic mouse models provided evidence that cell death could cause inflammation in different tissues. Inhibition of RIPK3-MLKL-dependent necroptosis by FADD and caspase-8 was identified as a key mechanism preventing inflammation in epithelial barriers. Moreover, the interplay between IKK/NF-κB and RIPK1 signaling was recognized as a critical determinant of tissue homeostasis and inflammation. NEMO was shown to regulate RIPK1 kinase activity-mediated apoptosis by NF-κB-dependent and –independent functions, which are critical for averting chronic tissue injury and inflammation in the intestine and the liver. In addition, RIPK1 was shown to exhibit kinase activity-independent functions that are essential for preventing cell death, maintaining tissue architecture and inhibiting inflammation. In the intestine, RIPK1 acts as a scaffold to prevent epithelial cell apoptosis and preserve tissue integrity. In the skin, RIPK1 functions via its RHIM to counteract ZBP1/DAI-dependent activation of RIPK3-MLKL-dependent necroptosis and inflammation. Collectively, these studies provided evidence that the regulation of cell death signaling plays an important role in the maintenance of tissue homeostasis, and suggested that cell death could be causally involved in the pathogenesis of inflammatory diseases.
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RIPK1 counteracts zbp1 mediated necroptosis to inhibit inflammation
Nature, 2016Co-Authors: Snehlata Kumari, Apostolos Polykratis, Laurens Wachsmuth, Manolis PasparakisAbstract:The enzyme RIPK1 functions through its RHIM domain to prevent ZBP1-mediated activation of RIPK3–MLKL-dependent necroptosis, thus preventing perinatal lethality and skin inflammation in adult mice. Manolis Pasparakis and colleagues report that receptor-interacting protein kinase 1 (RIPK1) functions via its RIP homotypic interaction motif (RHIM) to prevent skin inflammation in mice by inhibiting activation of RIPK3–MLKL-dependent necroptosis mediated by Z-DNA binding protein 1 (ZBP1; also known as DAI). The finding that ZBP1 is a critical mediator of inflammation beyond its previously known role in antiviral defence suggests that ZBP1 might be involved in the pathogenesis of necroptosis-associated inflammatory diseases. Receptor-interacting protein kinase 1 (RIPK1) regulates cell death and inflammation through kinase-dependent and -independent functions1,2,3,4,5,6,7. RIPK1 kinase activity induces caspase-8-dependent apoptosis and RIPK3 and mixed lineage kinase like (MLKL)-dependent necroptosis8,9,10,11,12,13. In addition, RIPK1 inhibits apoptosis and necroptosis through kinase-independent functions, which are important for late embryonic development and the prevention of inflammation in epithelial barriers14,15,16,17,18. The mechanism by which RIPK1 counteracts RIPK3–MLKL-mediated necroptosis has remained unknown. Here we show that RIPK1 prevents skin inflammation by inhibiting activation of RIPK3–MLKL-dependent necroptosis mediated by Z-DNA binding protein 1 (ZBP1, also known as DAI or DLM1). ZBP1 deficiency inhibited keratinocyte necroptosis and skin inflammation in mice with epidermis-specific RIPK1 knockout. Moreover, mutation of the conserved RIP homotypic interaction motif (RHIM) of endogenous mouse RIPK1 (RIPK1mRHIM) caused perinatal lethality that was prevented by RIPK3, MLKL or ZBP1 deficiency. Furthermore, mice expressing only RIPK1mRHIM in keratinocytes developed skin inflammation that was abrogated by MLKL or ZBP1 deficiency. Mechanistically, ZBP1 interacted strongly with phosphorylated RIPK3 in cells expressing RIPK1mRHIM, suggesting that the RIPK1 RHIM prevents ZBP1 from binding and activating RIPK3. Collectively, these results show that RIPK1 prevents perinatal death as well as skin inflammation in adult mice by inhibiting ZBP1-induced necroptosis. Furthermore, these findings identify ZBP1 as a critical mediator of inflammation beyond its previously known role in antiviral defence and suggest that ZBP1 might be implicated in the pathogenesis of necroptosis-associated inflammatory diseases.
Najoua Lalaoui - One of the best experts on this subject based on the ideXlab platform.
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mutations that prevent caspase cleavage of RIPK1 cause autoinflammatory disease
Nature, 2020Co-Authors: Najoua Lalaoui, Kate E Lawlor, Diep Chau, Steven E Boyden, Geryl Wood, Deborah L Stone, M Stoffels, Tobias KratinaAbstract:RIPK1 is a key regulator of innate immune signalling pathways. To ensure an optimal inflammatory response, RIPK1 is regulated post-translationally by well-characterized ubiquitylation and phosphorylation events, as well as by caspase-8-mediated cleavage1–7. The physiological relevance of this cleavage event remains unclear, although it is thought to inhibit activation of RIPK3 and necroptosis8. Here we show that the heterozygous missense mutations D324N, D324H and D324Y prevent caspase cleavage of RIPK1 in humans and result in an early-onset periodic fever syndrome and severe intermittent lymphadenopathy—a condition we term ‘cleavage-resistant RIPK1-induced autoinflammatory syndrome’. To define the mechanism for this disease, we generated a cleavage-resistant RIPK1D325A mutant mouse strain. Whereas RIPK1−/− mice died postnatally from systemic inflammation, RIPK1D325A/D325A mice died during embryogenesis. Embryonic lethality was completely prevented by the combined loss of Casp8 and Ripk3, but not by loss of Ripk3 or Mlkl alone. Loss of RIPK1 kinase activity also prevented RIPK1D325A/D325A embryonic lethality, although the mice died before weaning from multi-organ inflammation in a RIPK3-dependent manner. Consistently, RIPK1D325A/D325A and RIPK1D325A/+ cells were hypersensitive to RIPK3-dependent TNF-induced apoptosis and necroptosis. Heterozygous RIPK1D325A/+ mice were viable and grossly normal, but were hyper-responsive to inflammatory stimuli in vivo. Our results demonstrate the importance of caspase-mediated RIPK1 cleavage during embryonic development and show that caspase cleavage of RIPK1 not only inhibits necroptosis but also maintains inflammatory homeostasis throughout life. Heterozygous mutateons in the caspase-8 cleavage site of RIPK1 cause a range of autoinflammatory symptoms in humans, and caspase-8 cleavage of RIPK1 in a mouse model limits TNF-induced cell death and inflammation.
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mk2 phosphorylates RIPK1 to prevent tnf induced cell death
Molecular Cell, 2017Co-Authors: Isabel Jaco, Najoua Lalaoui, Tencho Tenev, Alessandro Annibaldi, Rebecca Wilson, Lucie Laurien, Kunzah Jamal, Sidonie Wicky John, Gianmaria LiccardiAbstract:TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.
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combination of iap antagonist and ifnγ activates novel caspase 10 and RIPK1 dependent cell death pathways
Cell Death & Differentiation, 2017Co-Authors: James A Rickard, Najoua Lalaoui, Maria C Tanzer, Nufail Khan, Nima Etemadi, Sukhdeep Kaur SpallAbstract:Peptido-mimetic inhibitor of apoptosis protein (IAP) antagonists (Smac mimetics (SMs)) can kill tumour cells by depleting endogenous IAPs and thereby inducing tumour necrosis factor (TNF) production. We found that interferon-γ (IFNγ) synergises with SMs to kill cancer cells independently of TNF− and other cell death receptor signalling pathways. Surprisingly, CRISPR/Cas9 HT29 cells doubly deficient for caspase-8 and the necroptotic pathway mediators RIPK3 or MLKL were still sensitive to IFNγ/SM-induced killing. Triple CRISPR/Cas9-knockout HT29 cells lacking caspase-10 in addition to caspase-8 and RIPK3 or MLKL were resistant to IFNγ/SM killing. Caspase-8 and RIPK1 deficiency was, however, sufficient to protect cells from IFNγ/SM-induced cell death, implying a role for RIPK1 in the activation of caspase-10. These data show that RIPK1 and caspase-10 mediate cell death in HT29 cells when caspase-8-mediated apoptosis and necroptosis are blocked and help to clarify how SMs operate as chemotherapeutic agents.
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RIPK1 regulates ripk3 mlkl driven systemic inflammation and emergency hematopoiesis
Cell, 2014Co-Authors: Joseph M Evans, James A Rickard, Joanne A Odonnell, Najoua Lalaoui, Tewhiti Rogers, James E VinceAbstract:Summary Upon ligand binding, RIPK1 is recruited to tumor necrosis factor receptor superfamily (TNFRSF) and Toll-like receptor (TLR) complexes promoting prosurvival and inflammatory signaling. RIPK1 also directly regulates caspase-8-mediated apoptosis or, if caspase-8 activity is blocked, RIPK3-MLKL-dependent necroptosis. We show that C57BL/6 RIPK1 −/− mice die at birth of systemic inflammation that was not transferable by the hematopoietic compartment. However, RIPK1 −/− progenitors failed to engraft lethally irradiated hosts properly. Blocking TNF reversed this defect in emergency hematopoiesis but, surprisingly, Tnfr1 deficiency did not prevent inflammation in RIPK1 −/− neonates. Deletion of Ripk3 or Mlkl , but not Casp 8, prevented extracellular release of the necroptotic DAMP, IL-33, and reduced Myd88 -dependent inflammation. Reduced inflammation in the RIPK1 −/− Ripk3 −/− , RIPK1 −/− Mlkl −/− , and RIPK1 −/− Myd88 −/− mice prevented neonatal lethality, but only RIPK1 −/− Ripk3 −/− Casp8 −/− mice survived past weaning. These results reveal a key function for RIPK1 in inhibiting necroptosis and, thereby, a role in limiting, not only promoting, inflammation.
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ciaps and xiap regulate myelopoiesis through cytokine production in an RIPK1 and ripk3 dependent manner
Blood, 2014Co-Authors: Najoua Lalaoui, James E Vince, Kate E Lawlor, Weilynn W Wong, Diep ChauAbstract:Loss of inhibitor of apoptosis proteins (IAPs), particularly cIAP1, can promote production of tumor necrosis factor (TNF) and sensitize cancer cell lines to TNF-induced necroptosis by promoting formation of a death-inducing signaling complex containing receptor-interacting serine/threonine-protein kinase (RIPK) 1 and 3. To define the role of IAPs in myelopoiesis, we generated a mouse with cIAP1, cIAP2, and XIAP deleted in the myeloid lineage. Loss of cIAPs and XIAP in the myeloid lineage caused overproduction of many proinflammatory cytokines, resulting in granulocytosis and severe sterile inflammation. In vitro differentiation of macrophages from bone marrow in the absence of cIAPs and XIAP led to detectable levels of TNF and resulted in reduced numbers of mature macrophages. The cytokine production and consequent cell death caused by IAP depletion was attenuated by loss or inhibition of TNF or TNF receptor 1. The loss of RIPK1 or RIPK3, but not the RIPK3 substrate mixed lineage kinase domain-like protein, attenuated TNF secretion and thereby prevented apoptotic cell death and not necrosis. Our results demonstrate that cIAPs and XIAP together restrain RIPK1- and RIPK3-dependent cytokine production in myeloid cells to critically regulate myeloid homeostasis.
