[The technique and application of individualized tympanic membrane flap in the repair of tympanic membrane under endoscopy ear surgery].

Objective:To investigate the technique of personalized flap making under otoscopy and its clinical application. Methods:The clinical data of patients who underwent 301 Military Hospital myringoplasty in the Department of otoendoscopic surgery, Department of Otorhinolaryngology, head and neck surgery, Department of Otorhinolaryngology, from October 2022 to 2023 August were analyzed retrospectively, all enrolled patients were performed independently by the same skilled otoendoscopic surgeon. The patients' general condition, medical history, tympanic membrane perforation scope, perforation size, need for tympanic cavity exploration, thickness of skin flap, tympanic cavity lesion scope, skin flap making method and postoperative rehabilitation were collected. Results:Many factors such as the location of tympanic membrane perforation, the thickness of the skin flap, the degree of curvature or stricture of the ear canal and the extent of the lesion in the tympanic cavity should be considered in the manufacture of the individualized tympanic membrane skin flap, the way of skin flap making does not affect the long-term postoperative rehabilitation, but it can effectively avoid unnecessary ear canal skin flap injury and improve the operation efficiency. Conclusion:Scientific flap fabrication is important for improving surgical efficiency and enhancing surgical confidence.

[The application of endoscope and microscope in the stapes surgeries].

Objective:To compare the application of endoscope and microscope in all kinds of stapes surgeries. Methods:Fifty-nine stapes surgeries have been collected from April 2020 to May 2023 in Senior Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Chinese PLA Medical School. Hearing level, hospital stay post-operation, times of hospital visit post-operation, etc. have been compared between the endoscopic group and microscopic group. Patients who were failed to place the stapes prosthesis because of the poor exposure of the oval window have been analyzed. Results:Otosclerosis was the most common diagnosis in both groups. There was 1（1/23） middle ear malformation in the endoscopic group and 5（5/36） middle ear malformations in the microscopic group. There were 2 Van Der Hover syndromes and 4 Treacher Collins syndromes in the microscopic group. In the endoscopic group ABG of 10 ears（43.5%） ≤ 10 dB, and ABG of 21 ears（91.3%） ≤20 dB.In the microscopic group ABG of 13 ears（41.9%） ≤ 10 dB, and ABG of 28 ears（90.3%） ≤ 20 dB. There was no statistic difference between 2 groups. Times of hospital visit post-operation in the endoscopic group was less than in the microscopic group（P<0.01）. There was no facial palsy, tympanic perforation or profound sensorineural hearing loss in both groups. Conclusion:Endoscope is more suitable for patients who are evaluated with no severe stapes malformation, or less manipulation of drilling the bone. It could also reduce the hospital visit post-operation. Patients with narrow ear canal or severe middle ear malformation are recommended to perform the surgery with microscope, because it provides the chance of manipulation with 2-hands of surgeons.

Erratum: CD151 promotes Colorectal Cancer progression by a crosstalk involving CEACAM6, LGR5 and Wnt signaling via TGFß1: Erratum.

[This corrects the article DOI: 10.7150/ijbs.53657.].

Prolonged hypoxia alleviates prolyl hydroxylation-mediated suppression of RIPK1 to promote necroptosis and inflammation.

The prolyl hydroxylation of hypoxia-inducible factor 1α (HIF-1α) mediated by the EGLN-pVHL pathway represents a classic signalling mechanism that mediates cellular adaptation under hypoxia. Here we identify RIPK1, a known regulator of cell death mediated by tumour necrosis factor receptor 1 (TNFR1), as a target of EGLN1-pVHL. Prolyl hydroxylation of RIPK1 mediated by EGLN1 promotes the binding of RIPK1 with pVHL to suppress its activation under normoxic conditions. Prolonged hypoxia promotes the activation of RIPK1 kinase by modulating its proline hydroxylation, independent of the TNFα-TNFR1 pathway. As such, inhibiting proline hydroxylation of RIPK1 promotes RIPK1 activation to trigger cell death and inflammation. Hepatocyte-specific Vhl deficiency promoted RIPK1-dependent apoptosis to mediate liver pathology. Our findings illustrate a key role of the EGLN-pVHL pathway in suppressing RIPK1 activation under normoxic conditions to promote cell survival and a model by which hypoxia promotes RIPK1 activation through modulating its proline hydroxylation to mediate cell death and inflammation in human diseases, independent of TNFR1.

Metabolic orchestration of cell death by AMPK-mediated phosphorylation of RIPK1.

Adenosine monophosphate-activated protein kinase (AMPK) activity is stimulated to promote metabolic adaptation upon energy stress. However, sustained metabolic stress may cause cell death. The mechanisms by which AMPK dictates cell death are not fully understood. We report that metabolic stress promoted receptor-interacting protein kinase 1 (RIPK1) activation mediated by TRAIL receptors, whereas AMPK inhibited RIPK1 by phosphorylation at Ser415 to suppress energy stress-induced cell death. Inhibiting pS415-RIPK1 by Ampk deficiency or RIPK1 S415A mutation promoted RIPK1 activation. Furthermore, genetic inactivation of RIPK1 protected against ischemic injury in myeloid Ampkα1-deficient mice. Our studies reveal that AMPK phosphorylation of RIPK1 represents a crucial metabolic checkpoint, which dictates cell fate response to metabolic stress, and highlight a previously unappreciated role for the AMPK-RIPK1 axis in integrating metabolism, cell death, and inflammation.

Graph-Collaborated Auto-Encoder Hashing for Multiview Binary Clustering.

Unsupervised hashing methods have attracted widespread attention with the explosive growth of large-scale data, which can greatly reduce storage and computation by learning compact binary codes. Existing unsupervised hashing methods attempt to exploit the valuable information from samples, which fails to take the local geometric structure of unlabeled samples into consideration. Moreover, hashing based on auto-encoders aims to minimize the reconstruction loss between the input data and binary codes, which ignores the potential consistency and complementarity of multiple sources data. To address the above issues, we propose a hashing algorithm based on auto-encoders for multiview binary clustering, which dynamically learns affinity graphs with low-rank constraints and adopts collaboratively learning between auto-encoders and affinity graphs to learn a unified binary code, called graph-collaborated auto-encoder (GCAE) hashing for multiview binary clustering. Specifically, we propose a multiview affinity graphs' learning model with low-rank constraint, which can mine the underlying geometric information from multiview data. Then, we design an encoder-decoder paradigm to collaborate the multiple affinity graphs, which can learn a unified binary code effectively. Notably, we impose the decorrelation and code balance constraints on binary codes to reduce the quantization errors. Finally, we use an alternating iterative optimization scheme to obtain the multiview clustering results. Extensive experimental results on five public datasets are provided to reveal the effectiveness of the algorithm and its superior performance over other state-of-the-art alternatives.

A Unified Framework Based on Graph Consensus Term for Multiview Learning.

In recent years, multiview learning technologies have attracted a surge of interest in the machine learning domain. However, when facing complex and diverse applications, most multiview learning methods mainly focus on specific fields rather than provide a scalable and robust proposal for different tasks. Moreover, most conventional methods used in these tasks are based on single view, which cannot be readily extended into the multiview scenario. Therefore, how to provide an efficient and scalable multiview framework is very necessary yet full of challenges. Inspired by the fact that most of the existing single view algorithms are graph-based ones to learn the complex structures within given data, this article aims at leveraging most existing graph embedding works into one formula via introducing the graph consensus term and proposes a unified and scalable multiview learning framework, termed graph consensus multiview framework (GCMF). GCMF attempts to make full advantage of graph-based works and rich information in the multiview data at the same time. On one hand, the proposed method explores the graph structure in each view independently to preserve the diversity property of graph embedding methods; on the other hand, learned graphs can be flexibly chosen to construct the graph consensus term, which can more stably explore the correlations among multiple views. To this end, GCMF can simultaneously take the diversity and complementary information among different views into consideration. To further facilitate related research, we provide an implementation of the multiview extension for locality linear embedding (LLE), named GCMF-LLE, which can be efficiently solved by applying the alternating optimization strategy. Empirical validations conducted on six benchmark datasets can show the effectiveness of our proposed method.

Nuclear RIPK1 promotes chromatin remodeling to mediate inflammatory response.

RIPK1 is a master regulator of multiple cell death pathways, including apoptosis and necroptosis, and inflammation. Importantly, activation of RIPK1 has also been shown to promote the transcriptional induction of proinflammatory cytokines in cells undergoing necroptosis, in animal models of amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD), and in human ALS and AD. Rare human genetic carriers of non-cleavable RIPK1 variants (D324V and D324H) exhibit distinct symptoms of recurrent fevers and increased transcription of proinflammatory cytokines. Multiple RIPK1 inhibitors have been advanced into human clinical trials as new therapeutics for human inflammatory and neurodegenerative diseases, such as ALS and AD. However, it is unclear whether and how RIPK1 kinase activity directly mediates inflammation independent of cell death as the nuclear function of RIPK1 has not yet been explored. Here we show that nuclear RIPK1 is physically associated with the BAF complex. Upon RIPK1 activation, the RIPK1/BAF complex is recruited by specific transcription factors to active enhancers and promoters marked by H3K4me1 and H3K27ac. Activated nuclear RIPK1 mediates the phosphorylation of SMARCC2, a key component of the BAF complex, to promote chromatin remodeling and the transcription of specific proinflammatory genes. Increased nuclear RIPK1 activation and RIPK1/BAF-mediated chromatin-remodeling activity were found in cells expressing non-cleavable RIPK1, and increased enrichment of activated RIPK1 on active enhancers and promoters was found in an animal model and human pathological samples of ALS. Our results suggest that RIPK1 kinase serves as a transcriptional coregulator in nucleus that can transmit extracellular stimuli to the BAF complex to modulate chromatin accessibility and directly regulate the transcription of specific genes involved in mediating inflammatory responses.

NEK1-mediated retromer trafficking promotes blood-brain barrier integrity by regulating glucose metabolism and RIPK1 activation.

Loss-of-function mutations in NEK1 gene, which encodes a serine/threonine kinase, are involved in human developmental disorders and ALS. Here we show that NEK1 regulates retromer-mediated endosomal trafficking by phosphorylating VPS26B. NEK1 deficiency disrupts endosomal trafficking of plasma membrane proteins and cerebral proteome homeostasis to promote mitochondrial and lysosomal dysfunction and aggregation of α-synuclein. The metabolic and proteomic defects of NEK1 deficiency disrupts the integrity of blood-brain barrier (BBB) by promoting lysosomal degradation of A20, a key modulator of RIPK1, thus sensitizing cerebrovascular endothelial cells to RIPK1-dependent apoptosis and necroptosis. Genetic inactivation of RIPK1 or metabolic rescue with ketogenic diet can prevent postnatal lethality and BBB damage in NEK1 deficient mice. Inhibition of RIPK1 reduces neuroinflammation and aggregation of α-synuclein in the brains of NEK1 deficient mice. Our study identifies a molecular mechanism by which retromer trafficking and metabolism regulates cerebrovascular integrity, cerebral proteome homeostasis and RIPK1-mediated neuroinflammation.

The Mechanism of Xiaoyao San in the Treatment of Ovarian Cancer by Network Pharmacology and the Effect of Stigmasterol on the PI3K/Akt Pathway.

PURPOSE: This study was aimed at exploring the regulatory mechanism of Xiaoyao San (XYS) and its main compound, Stigmasterol, in the biological network and signaling pathway of ovarian cancer (OC) through network pharmacology-based analyses and experimental validation. METHODS: The active compounds and targets of XYS were studied by the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The GeneCards and OMIM databases were used to screen common targets of XYS in the treatment of OC. Combined with the STRING database and Cytoscape 3.6.0, the core compounds and targets of XYS were obtained. GO and KEGG pathway enrichment analyses of core target genes were carried out by using the Metascape and DAVID databases. Molecular docking has been achieved by using the AutoDock Vina program to discuss the interaction of the core targets and compounds of XYS in the treatment of OC. The effect of Stigmasterol on proliferation and migration were assessed by CCK8 and wound healing assay. Western blot and qRT-PCR were used to analyze the protein and mRNA expressions of PI3K, Akt, and PTEN after treatment of Stigmasterol. RESULTS: A total of 113 common targets of XYS for the treatment of OC were obtained from 975 targets related to OC and 239 targets of XYS's effect. The main compounds of XYS include Quercetin, Naringenin, Isorhamnetin, and Stigmasterol, which mainly regulate the targets such as TP53, Akt1, and MYC and PI3K/Akt, p53, and cell cycle signal pathways. At the same time, molecular docking showed that Stigmasterol and Akt1 had good docking conformation. Stigmasterol inhibited OC cell proliferation and migration in vitro and reduced the protein and mRNA expressions of the PI3K/Akt signaling pathway. CONCLUSION: Stigmasterol as the one of the main compounds of XYS suppresses OC cell activities through the PI3K-Akt signaling pathway.

CD151 promotes Colorectal Cancer progression by a crosstalk involving CEACAM6, LGR5 and Wnt signaling via TGFß1.

CD151 impacts various signaling pathways in different cancers, and promotes colorectal cancer (CRC) cell malignancy by yet undefined mechanisms. This study aimed to comprehensively assess CD151's function in CRC. CD151 levels were significantly higher in CRC tissues and cells compared with controls in the tissue microarray. Cell viability, migration and invasion were suppressed by CD151 downregulation in CRC cells. Consistently, mouse xenografts were inhibited by CD151 silencing. RNA-seq revealed that multiple genes were significantly altered by CD151 knockdown in cultured CRC cells and xenografts. Particularly, transforming growth factor ß1 (TGFß1), carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) and leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) alongside CD151 were downregulated both in vitro and in vivo. Co-immunoprecipitation and mass spectrometry results were validated by qRT-PCR and immunoblot. Moreover, pull-down assay and immunofluorescence confirmed the associations of TGFß1, CEACAM6 and LGR5 with CD151. This study demonstrated CEACAM6, LGR5 and Wnt pathway suppression by CD151 silencing might occur through TGFß1 regulation, offering a comprehensive view of CD151's roles in colorectal carcinogenesis. Our findings provide an insight into the CD151-involved signaling network in CRC oncogenesis, which could be utilized to design novel targeted therapies against CD151-based signaling in treatment for CRC.

RIPK1 Promotes Energy Sensing by the mTORC1 Pathway.

The mechanisms of cellular energy sensing and AMPK-mediated mTORC1 inhibition are not fully delineated. Here, we discover that RIPK1 promotes mTORC1 inhibition during energetic stress. RIPK1 is involved in mediating the interaction between AMPK and TSC2 and facilitate TSC2 phosphorylation at Ser1387. RIPK1 loss results in a high basal mTORC1 activity that drives defective lysosomes in cells and mice, leading to accumulation of RIPK3 and CASP8 and sensitization to cell death. RIPK1-deficient cells are unable to cope with energetic stress and are vulnerable to low glucose levels and metformin. Inhibition of mTORC1 rescues the lysosomal defects and vulnerability to energetic stress and prolongs the survival of RIPK1-deficient neonatal mice. Thus, RIPK1 plays an important role in the cellular response to low energy levels and mediates AMPK-mTORC1 signaling. These findings shed light on the regulation of mTORC1 during energetic stress and unveil a point of crosstalk between pro-survival and pro-death pathways.

Reduction of mNAT1/hNAT2 Contributes to Cerebral Endothelial Necroptosis and Aß Accumulation in Alzheimer's Disease.

The contribution and mechanism of cerebrovascular pathology in Alzheimer's disease (AD) pathogenesis are still unclear. Here, we show that venular and capillary cerebral endothelial cells (ECs) are selectively vulnerable to necroptosis in AD. We identify reduced cerebromicrovascular expression of murine N-acetyltransferase 1 (mNat1) in two AD mouse models and hNat2, the human ortholog of mNat1 and a genetic risk factor for type-2 diabetes and insulin resistance, in human AD. mNat1 deficiency in Nat1-/- mice and two AD mouse models promotes blood-brain barrier (BBB) damage and endothelial necroptosis. Decreased mNat1 expression induces lysosomal degradation of A20, an important regulator of necroptosis, and LRP1ß, a key component of LRP1 complex that exports Aß in cerebral ECs. Selective restoration of cerebral EC expression of mNAT1 delivered by adeno-associated virus (AAV) rescues cerebromicrovascular levels of A20 and LRP1ß, inhibits endothelial necroptosis and activation, ameliorates mitochondrial fragmentation, reduces Aß deposits, and improves cognitive function in the AD mouse model.

Modulating TRADD to restore cellular homeostasis and inhibit apoptosis.

Cell death in human diseases is often a consequence of disrupted cellular homeostasis. If cell death is prevented without restoring cellular homeostasis, it may lead to a persistent dysfunctional and pathological state. Although mechanisms of cell death have been thoroughly investigated1-3, it remains unclear how homeostasis can be restored after inhibition of cell death. Here we identify TRADD4-6, an adaptor protein, as a direct regulator of both cellular homeostasis and apoptosis. TRADD modulates cellular homeostasis by inhibiting K63-linked ubiquitination of beclin 1 mediated by TRAF2, cIAP1 and cIAP2, thereby reducing autophagy. TRADD deficiency inhibits RIPK1-dependent extrinsic apoptosis and proteasomal stress-induced intrinsic apoptosis. We also show that the small molecules ICCB-19 and Apt-1 bind to a pocket on the N-terminal TRAF2-binding domain of TRADD (TRADD-N), which interacts with the C-terminal domain (TRADD-C) and TRAF2 to modulate the ubiquitination of RIPK1 and beclin 1. Inhibition of TRADD by ICCB-19 or Apt-1 blocks apoptosis and restores cellular homeostasis by activating autophagy in cells with accumulated mutant tau, α-synuclein, or huntingtin. Treatment with Apt-1 restored proteostasis and inhibited cell death in a mouse model of proteinopathy induced by mutant tau(P301S). We conclude that pharmacological targeting of TRADD may represent a promising strategy for inhibiting cell death and restoring homeostasis to treat human diseases.

6,12-Diphenyl-3, 9-diazatetraasterane-1, 5, 7, 11-tetracarboxylate Inhibits Proliferation, Migration and Promotes Apoptosis in Ovarian Cancer Cells.

6,12-Diphenyl-3,9-diazatetraasterane-1, 5, 7, 11-tetracarboxylate (DDTC) has been synthesized by the photodimerization of 4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate. The potential of theercvantitumor activity and mechanism were investigated in vitro using MTT assay in human lung cancer cell line A549, ovarian cancer cell lines SKOV3 and A2780, breast cancer cell line MCF-7, gastric cancer cell line BGC-823, colon cancer cell line HT29, prostate cancer cell line DU145, and liver cancer cell line SMMC7721. The results show that DDTC can inhibit the growth of ovarian cancer SKOV3 and A2780 cells. The best IC50 value is approximately 5.29 ± 0.38 and 4.29 ± 0.39 µM, respectively. DDTC induced the cell cycle arrest in the G2 phase by flow cytometric analysis. The migration and invasion of ovarian cancer SKOV3 and A2780 cells were inhibited by DDTC. DDTC could increase the expression protein level of E-cadherin in A2780 cells and ascend the expression protein and mRNA levels of E-cadherin in SKOV3 cells. DDTC could also decrease the protein and mRNA expression of EMT (epithelial-to-mesenchymal transition) markers of N-cadherin and Vimentin. mRNA and protein expression level of checkpoint kinase 1 (Chk1) were significantly increased and expressions of cyclin-dependent kinase (CDK1) and cell division cycle 25a (Cdc25a) were decreased in the SKOV3 and A2780 cell lines. Moreover, DDTC induced apoptosis by the cleavage and activation of caspase 3 and caspase 9.

[Efficacy of semicircular canal occlusion in the treatment of fifteen pateints with Meniere's disease].

Objective:To investigate the long-term efficacy of semicircular canal occlusion in the treatment of refractory Meniere's disease. Method:Fifteen patients with Meniere's disease who underwent semicircular canal occlusion were reviewed. The preoperative and postoperative frequency of vertigo ,quality of life, hearing and tinnitus level were compared. All patients were followed for more than 24 months. Result:Postoperatively, vertigo was controlled effectively in all 15 cases, and the control rate was 100%, of which 11 cases were completely controlled（Grade A） and 4 cases were basically controlled（Grade B）. The improvement rate of quality of life was 100%. The hearing worse in 4 cases（26.7%） and stabilized in 11 cases（73.3%）. The tinnitus was relieved in 7 cases（46.7%）, unchanged in 7 cases（46.7%） and aggravated in 1 case（6.7%）. Conclusion:Semicircular canal occlusion can effectively control the vertigo symptoms of refractory Meniere's disease and improve the quality of life. The long-term efficacy of semicircular canal occlusion is definite, but there is a risk of hearing loss.

The Epigenetic Modification of Epigallocatechin Gallate (EGCG) on Cancer.

Among the major components of green tea, epigallocatechin-3-gallate (EGCG) is the most effective for its anti-cancer characteristics. The bulk of studies provide the mechanisms of suppressive function of EGCG are involved in alteration of cancer cell cycle, development, and apoptosis through activation/inhibition of several signal pathways. Another mechanism that explains the multiple effects exerted by EGCG in cancer is the epigenetic change by DNA methylation or methyltransferases, histone acetylation or deacetylases, and no coding RNAs (micoRNAs). Furthermore, decontrolled expression of miRNA transcription has been tested to be directly regulated by oncogenic and tumor-suppressor transcription factors. Recently, several proteins have been identified as miRNA direct interactors by EGCG. However, the mechanisms explaining the action of miRNA being modulated by EGCG have not been completely understood yet. This review summarizes the state of epigenetic change being modulated by EGCG in a variety of cancers and oncogenic and tumor-suppressor transcription factors.

Sequential activation of necroptosis and apoptosis cooperates to mediate vascular and neural pathology in stroke.

Apoptosis and necroptosis are two regulated cell death mechanisms; however, the interaction between these cell death pathways in vivo is unclear. Here we used cerebral ischemia/reperfusion as a model to investigate the interaction between apoptosis and necroptosis. We show that the activation of RIPK1 sequentially promotes necroptosis followed by apoptosis in a temporally specific manner. Cerebral ischemia/reperfusion insult rapidly activates necroptosis to promote cerebral hemorrhage and neuroinflammation. Ripk3 deficiency reduces cerebral hemorrhage and delays the onset of neural damage mediated by inflammation. Reduced cerebral perfusion resulting from arterial occlusion promotes the degradation of TAK1, a suppressor of RIPK1, and the transition from necroptosis to apoptosis. Conditional knockout of TAK1 in microglial/infiltrated macrophages and neuronal lineages sensitizes to ischemic infarction by promoting apoptosis. Taken together, our results demonstrate the critical role of necroptosis in mediating neurovascular damage and hypoperfusion-induced TAK1 loss, which subsequently promotes apoptosis and cerebral pathology in stroke and neurodegeneration.

Regulation of a distinct activated RIPK1 intermediate bridging complex I and complex II in TNFα-mediated apoptosis.

Stimulation of cells with TNFα can promote distinct cell death pathways, including RIPK1-independent apoptosis, necroptosis, and RIPK1-dependent apoptosis (RDA)-the latter of which we still know little about. Here we show that RDA involves the rapid formation of a distinct detergent-insoluble, highly ubiquitinated, and activated RIPK1 pool, termed "iuRIPK1." iuRIPK1 forms after RIPK1 activation in TNF-receptor-associated complex I, and before cytosolic complex II formation and caspase activation. To identify regulators of iuRIPK1 formation and RIPK1 activation in RDA, we conducted a targeted siRNA screen of 1,288 genes. We found that NEK1, whose loss-of-function mutations have been identified in 3% of ALS patients, binds to activated RIPK1 and restricts RDA by negatively regulating formation of iuRIPK1, while LRRK2, a kinase implicated in Parkinson's disease, promotes RIPK1 activation and association with complex I in RDA. Further, the E3 ligases APC11 and c-Cbl promote RDA, and c-Cbl is recruited to complex I in RDA, where it promotes prodeath K63-ubiquitination of RIPK1 to lead to iuRIPK1 formation. Finally, we show that two different modes of necroptosis induction by TNFα exist which are differentially regulated by iuRIPK1 formation. Overall, this work reveals a distinct mechanism of RIPK1 activation that mediates the signaling mechanism of RDA as well as a type of necroptosis.

Death-domain dimerization-mediated activation of RIPK1 controls necroptosis and RIPK1-dependent apoptosis.

RIPK1 is a critical mediator of cell death and inflammation downstream of TNFR1 upon stimulation by TNFα, a potent proinflammatory cytokine involved in a multitude of human inflammatory and degenerative diseases. RIPK1 contains an N-terminal kinase domain, an intermediate domain, and a C-terminal death domain (DD). The kinase activity of RIPK1 promotes cell death and inflammation. Here, we investigated the involvement of RIPK1-DD in the regulation of RIPK1 kinase activity. We show that a charge-conserved mutation of a lysine located on the surface of DD (K599R in human RIPK1 or K584R in murine RIPK1) blocks RIPK1 activation in necroptosis and RIPK1-dependent apoptosis and the formation of complex II. Ripk1K584R/K584R knockin mutant cells are resistant to RIPK1 kinase-dependent apoptosis and necroptosis. The resistance of K584R cells, however, can be overcome by forced dimerization of RIPK1. Finally, we show that the K584R RIPK1 knockin mutation protects mice against TNFα-induced systematic inflammatory response syndrome. Our study demonstrates the role of RIPK1-DD in mediating RIPK1 dimerization and activation of its kinase activity during necroptosis and RIPK1-dependent apoptosis.