Non-canonical autophosphorylation of RIPK1 drives timely pyroptosis to control Yersinia infection.

Caspase-8-dependent pyroptosis has been shown to mediate host protection from Yersinia infection. For this mode of cell death, the kinase activity of receptor-interacting protein kinase 1 (RIPK1) is required, but the autophosphorylation sites required to drive caspase-8 activation have not been determined. Here, we show that non-canonical autophosphorylation of RIPK1 at threonine 169 (T169) is necessary for caspase-8-mediated pyroptosis.

Apoptotic cell death in disease-Current understanding of the NCCD 2023.

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions.

The regulation of necroptosis and perspectives for the development of new drugs preventing ischemic/reperfusion of cardiac injury.

In the last 10 years, mortality from acute myocardial infarction (AMI) has not significantly decreased. This situation is associated with the absence in clinical practice of highly effective drugs capable of preventing the occurrence of reperfusion injury of the heart. Necroptosis inhibitors may become prototypes for the creation of highly effective drugs that increase cardiac tolerance to ischemic/reperfusion (I/R) and reduce the mortality rate in patients with AMI.

ZBP1 promotes inflammatory responses downstream of TLR3/TLR4 via timely delivery of RIPK1 to TRIF.

ZBP1 is widely recognized as a mediator of cell death for its role in initiating necroptotic, apoptotic, and pyroptotic cell death pathways in response to diverse pathogenic infection. Herein, we characterize an unanticipated role for ZBP1 in promoting inflammatory responses to bacterial lipopolysaccharide (LPS) or double-stranded RNA (dsRNA). In response to both stimuli, ZBP1 promotes the timely delivery of RIPK1 to the Toll-like receptor (TLR)3/4 adaptor TRIF and M1-ubiquitination of RIPK1, which sustains activation of inflammatory signaling cascades downstream of RIPK1.

Genetic inhibition of RIPK3 ameliorates functional outcome in controlled cortical impact independent of necroptosis.

Traumatic brain injury (TBI) is a leading cause of death and disability with no specific effective therapy, in part because disease driving mechanisms remain to be elucidated. Receptor interacting protein kinases (RIPKs) are serine/threonine kinases that assemble multi-molecular complexes that induce apoptosis, necroptosis, inflammasome and nuclear factor kappa B activation. Prior studies using pharmacological inhibitors implicated necroptosis in the pathogenesis of TBI and stroke, but these studies cannot be used to conclusively demonstrate a role for necroptosis because of the possibility of off target effects.

Immunoprecipitation Strategies to Isolate RIPK1/RIPK3 Complexes in Mouse Macrophages.

A large protein complex, containing RIPK1, RIPK3, and caspase-8 and known as Complex II, has emerged as one of the key mediators of cell death downstream from a range of innate immune triggers. This regulatory mechanism plays a prominent role in macrophages, where Complex II has been linked to apoptosis, pyroptosis, and necroptosis as well as the enhancement of inflammatory gene expression. Although core components of this complex are fairly well understood, more subtle proteomic changes that determine the direction of a response once the complex is assembled remain much less clear.

RIPK1 activation mediates neuroinflammation and disease progression in multiple sclerosis.

Receptor interacting protein kinase 1 (RIPK1) mediates cell death and inflammatory signaling and is increased in multiple sclerosis (MS) brain samples. Here, we investigate the role of glial RIPK1 kinase activity in mediating MS pathogenesis. We demonstrate RIPK1 levels correlate with MS disease progression.

Design of pyrido[2,3-d]pyrimidin-7-one inhibitors of receptor interacting protein kinase-2 (RIPK2) and nucleotide-binding oligomerization domain (NOD) cell signaling.

Receptor interacting protein kinase-2 (RIPK2) is an enzyme involved in the transduction of pro-inflammatory nucleotide-binding oligomerization domain (NOD) cell signaling, a pathway implicated in numerous chronic inflammatory conditions. Herein, a pyrido[2,3-d]pyrimidin-7-one based class of RIPK2 kinase and NOD2 cell signaling inhibitors is described. For example, 33 (e.

ZBP1 promotes LPS-induced cell death and IL-1β release via RHIM-mediated interactions with RIPK1.

Inflammation and cell death are closely linked arms of the host immune response to infection, which when carefully balanced ensure host survival. One example of this balance is the tightly regulated transition from TNFR1-associated pro-inflammatory complex I to pro-death complex II. By contrast, here we show that a TRIF-dependent complex containing FADD, RIPK1 and caspase-8 (that we have termed the TRIFosome) mediates cell death in response to Yersinia pseudotuberculosis and LPS.

Cell-specific activation of RIPK1 and MLKL after intracerebral hemorrhage in mice.

Receptor-interacting protein kinase-1 (RIPK1) is a master regulator of cell death and inflammation, and mediates programmed necrosis (necroptosis) via mixed-lineage kinase like (MLKL) protein. Prior studies in experimental intracerebral hemorrhage (ICH) implicated RIPK1 in the pathogenesis of neuronal death and cognitive outcome, but the relevant cell types involved and potential role of necroptosis remain unexplored. In mice subjected to autologous blood ICH, early RIPK1 activation was observed in neurons, endothelium and pericytes, but not in astrocytes.

RIPK protein kinase family: Atypical lives of typical kinases.

Receptor Interacting Protein Kinases (RIPKs) are a family of Ser/Thr/Tyr kinases whose functions, regulation and pathophysiologic roles have remained an enigma for a long time. In recent years, these proteins garnered significant interest due to their roles in regulating a variety of host defense functions including control of inflammatory gene expression, different forms of cell death, and cutaneous and intestinal barrier functions. In addition, there is accumulating evidence that while these kinases seemingly follow typical kinase blueprints, their functioning in cells can take forms that are atypical for protein kinases.

Constitutive Interferon Attenuates RIPK1/3-Mediated Cytokine Translation.

Receptor-interacting protein kinase 1 (RIPK1) and 3 (RIPK3) are well known for their capacity to drive necroptosis via mixed-lineage kinase-like domain (MLKL). Recently, RIPK1/3 kinase activity has been shown to drive inflammation via activation of MAPK signaling. However, the regulatory mechanisms underlying this kinase-dependent cytokine production remain poorly understood.

Targeting RIPK1 for the treatment of human diseases.

RIPK1 kinase has emerged as a promising therapeutic target for the treatment of a wide range of human neurodegenerative, autoimmune, and inflammatory diseases. This was supported by extensive studies which demonstrated that RIPK1 is a key mediator of apoptotic and necrotic cell death as well as inflammatory pathways. Furthermore, human genetic evidence has linked the dysregulation of RIPK1 to the pathogenesis of ALS as well as other inflammatory and neurodegenerative diseases.

Chemical Library Screens to Identify Pharmacological Modulators of Necroptosis.

Necroptosis is mediated by the formation of the detergent-insoluble necrosome complex between Ser/Thr kinases RIPK1 and RIPK3, which mediates RIPK3-dependent phosphorylation and activation of the critical necroptosis effector MLKL. Small molecule screens have been instrumental in the development of new chemical probes for this pathway. In this chapter, we describe several cellular assays that are readily amendable for the identification of new modulators of necroptosis as well as secondary assays to facilitate initial characterization of the mode of activity of small molecule hits.

Small molecule inhibitors reveal an indispensable scaffolding role of RIPK2 in NOD2 signaling.

RIPK2 mediates inflammatory signaling by the bacteria-sensing receptors NOD1 and NOD2. Kinase inhibitors targeting RIPK2 are a proposed strategy to ameliorate NOD-mediated pathologies. Here, we reveal that RIPK2 kinase activity is dispensable for NOD2 inflammatory signaling and show that RIPK2 inhibitors function instead by antagonizing XIAP-binding and XIAP-mediated ubiquitination of RIPK2.

Correction to: Phenytoin inhibits necroptosis.

The name of the one of the authors was misspelt. The author's surname is Rodriguez, not Rodriquez as originally published. This has been corrected in both the PDF and HTML versions of the Article.

Caspase-Dependent Suppression of Type I Interferon Signaling Promotes Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication.

An important component of lytic infection by Kaposi's sarcoma-associated herpesvirus (KSHV) is the ability of the virus to evade the innate immune response, specifically type I interferon (IFN) responses that are triggered by recognition of viral nucleic acids. Inhibition of type I IFN responses by the virus promotes viral replication. Here, we report that KSHV uses a caspase-dependent mechanism to block type I IFN, in particular IFN-β, responses during lytic infection.

Phenytoin inhibits necroptosis.

Receptor-interacting protein kinases 1 and 3 (RIPK1/3) have best been described for their role in mediating a regulated form of necrosis, referred to as necroptosis. During this process, RIPK3 phosphorylates mixed lineage kinase domain-like (MLKL) to cause plasma membrane rupture. RIPK3-deficient mice have recently been demonstrated to be protected in a series of disease models, but direct evidence for activation of necroptosis in vivo is still limited.

Activation loop targeting strategy for design of receptor-interacting protein kinase 2 (RIPK2) inhibitors.

Development of selective kinase inhibitors remains a challenge due to considerable amino acid sequence similarity among family members particularly in the ATP binding site. Targeting the activation loop might offer improved inhibitor selectivity since this region of kinases is less conserved. However, the strategy presents difficulties due to activation loop flexibility.

Targeting energy metabolism of cancer cells: Combined administration of NCL-240 and 2-DG.

Cancer cells increase their metabolism to produce the energy and biomolecules necessary for growth and proliferation. Thus, energy metabolism pathways may serve as targets for anti-cancer therapy. NCL-240 is a second generation anti-cancer drug belonging to the PITenins class of PI3K-Akt inhibitors.

Genetic Inhibition of Receptor Interacting Protein Kinase-1 Reduces Cell Death and Improves Functional Outcome After Intracerebral Hemorrhage in Mice.

Background And Purpose: Recent studies using cultured cells and rodent intracerebral hemorrhage (ICH) models have implicated RIPK1 (receptor interacting protein kinase-1) as a driver of programmed necrosis and secondary injury based on use of chemical inhibitors. However, these inhibitors have off-target effects and cannot be used alone to prove a role for RIPK1. The aim of the current study was to examine the effect of genetic inhibition of the kinase domain of RIPK1 in a mouse ICH model.