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1.
Cell ; 174(6): 1477-1491.e19, 2018 09 06.
Article in English | MEDLINE | ID: mdl-30146158

ABSTRACT

Aging is a major risk factor for both genetic and sporadic neurodegenerative disorders. However, it is unclear how aging interacts with genetic predispositions to promote neurodegeneration. Here, we investigate how partial loss of function of TBK1, a major genetic cause for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) comorbidity, leads to age-dependent neurodegeneration. We show that TBK1 is an endogenous inhibitor of RIPK1 and the embryonic lethality of Tbk1-/- mice is dependent on RIPK1 kinase activity. In aging human brains, another endogenous RIPK1 inhibitor, TAK1, exhibits a marked decrease in expression. We show that in Tbk1+/- mice, the reduced myeloid TAK1 expression promotes all the key hallmarks of ALS/FTD, including neuroinflammation, TDP-43 aggregation, axonal degeneration, neuronal loss, and behavior deficits, which are blocked upon inhibition of RIPK1. Thus, aging facilitates RIPK1 activation by reducing TAK1 expression, which cooperates with genetic risk factors to promote the onset of ALS/FTD.


Subject(s)
Apoptosis , Protein Serine-Threonine Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Adult , Aged , Aging , Animals , Apoptosis/drug effects , Axons/metabolism , Behavior, Animal , Brain/cytology , Brain/metabolism , Cells, Cultured , Humans , I-kappa B Kinase/metabolism , Mice , Mice, Knockout , Microglia/cytology , Microglia/drug effects , Microglia/metabolism , Phosphorylation/drug effects , Protein Serine-Threonine Kinases/deficiency , Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/deficiency , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Spinal Cord/metabolism , Staurosporine/pharmacology , Tumor Necrosis Factor-alpha/pharmacology
2.
Mol Cell ; 84(5): 811-813, 2024 Mar 07.
Article in English | MEDLINE | ID: mdl-38458169

ABSTRACT

Molecular Cell speaks with first author Shouqiao Hou and corresponding author Daichao Xu about the scientific journey toward their paper, "PARP5A and RNF146 phase separation restrains RIPK1-dependent necroptosis" (in this issue of Molecular Cell), the challenges they faced, and interesting remaining questions for the field.

3.
Mol Cell ; 84(5): 938-954.e8, 2024 Mar 07.
Article in English | MEDLINE | ID: mdl-38272024

ABSTRACT

Phase separation is a vital mechanism that mediates the formation of biomolecular condensates and their functions. Necroptosis is a lytic form of programmed cell death mediated by RIPK1, RIPK3, and MLKL downstream of TNFR1 and has been implicated in mediating many human diseases. However, whether necroptosis is regulated by phase separation is not yet known. Here, we show that upon the induction of necroptosis and recruitment by the adaptor protein TAX1BP1, PARP5A and its binding partner RNF146 form liquid-like condensates by multivalent interactions to perform poly ADP-ribosylation (PARylation) and PARylation-dependent ubiquitination (PARdU) of activated RIPK1 in mouse embryonic fibroblasts. We show that PARdU predominantly occurs on the K376 residue of mouse RIPK1, which promotes proteasomal degradation of kinase-activated RIPK1 to restrain necroptosis. Our data demonstrate that PARdU on K376 of mouse RIPK1 provides an alternative cell death checkpoint mediated by phase separation-dependent control of necroptosis by PARP5A and RNF146.


Subject(s)
Necroptosis , Phase Separation , Animals , Mice , Apoptosis/physiology , Cell Death , Fibroblasts/metabolism , Necroptosis/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolism
4.
Annu Rev Genet ; 55: 235-263, 2021 11 23.
Article in English | MEDLINE | ID: mdl-34813352

ABSTRACT

The receptor-interacting protein kinase 1 (RIPK1) is recognized as a master upstream regulator that controls cell survival and inflammatory signaling as well as multiple cell death pathways, including apoptosis and necroptosis. The activation of RIPK1 kinase is extensively modulated by ubiquitination and phosphorylation, which are mediated by multiple factors that also control the activation of the NF-κB pathway. We discuss current findings regarding the genetic modulation of RIPK1 that controls its activation and interaction with downstream mediators, such as caspase-8 and RIPK3, to promote apoptosis and necroptosis. We also address genetic autoinflammatory human conditions that involve abnormal activation of RIPK1. Leveraging these new genetic and mechanistic insights, we postulate how an improved understanding of RIPK1 biology may support the development of therapeutics that target RIPK1 for the treatment of human inflammatory and neurodegenerative diseases.


Subject(s)
Necroptosis , Protein Kinases , Apoptosis/genetics , Humans , Necroptosis/genetics , Protein Kinases/genetics , Protein Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Signal Transduction/genetics
5.
Nature ; 587(7832): 133-138, 2020 11.
Article in English | MEDLINE | ID: mdl-32968279

ABSTRACT

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.


Subject(s)
Apoptosis/drug effects , Homeostasis/drug effects , TNF Receptor-Associated Death Domain Protein/antagonists & inhibitors , TNF Receptor-Associated Death Domain Protein/metabolism , Animals , Autophagy/drug effects , Baculoviral IAP Repeat-Containing 3 Protein/metabolism , Beclin-1/chemistry , Beclin-1/metabolism , Bortezomib/antagonists & inhibitors , Bortezomib/pharmacology , Cell Line , Humans , Huntingtin Protein/metabolism , Inhibitor of Apoptosis Proteins/metabolism , Male , Mice , Models, Molecular , Neurofibrillary Tangles/metabolism , Proteome/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/chemistry , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , TNF Receptor-Associated Death Domain Protein/chemistry , TNF Receptor-Associated Death Domain Protein/deficiency , TNF Receptor-Associated Factor 2/metabolism , Ubiquitination , alpha-Synuclein/metabolism , tau Proteins/metabolism
6.
Genes Dev ; 31(10): 1024-1035, 2017 05 15.
Article in English | MEDLINE | ID: mdl-28619731

ABSTRACT

Aberrant activation of the Wnt signaling pathway plays an important role in human cancer development. Wnt signaling is negatively regulated by Axin, a scaffolding protein that controls a rate-limiting step in the destruction of ß-catenin, the central activator of the Wnt pathway. In Wnt-stimulated cells, Axin is rapidly modified by tankyrase-mediated poly(ADP-ribosyl)ation, which promotes the proteolysis of Axin and consequent stabilization of ß-catenin. Thus, regulation of the levels and activity of tankyrases is mechanistically important in controlling Wnt signaling. Here, we identify ubiquitin-specific protease 25 (USP25) as a positive regulator of Wnt/ß-catenin signaling. We found that USP25 directly interacted with tankyrases to promote their deubiquitination and stabilization. We demonstrated that USP25 deficiency could promote the degradation of tankyrases and consequent stabilization of Axin to antagonize Wnt signaling. We further characterized the interaction between TNKS1 and USP25 by X-ray crystal structure determination. Our results provide important new insights into the molecular mechanism that regulates the turnover of tankyrases and the possibility of targeting the stability of tankyrases by antagonizing their interaction with USP25 to modulate the Wnt/ß-catenin pathway.


Subject(s)
Enzyme Stability/genetics , Tankyrases/metabolism , Ubiquitin Thiolesterase/metabolism , Wnt Signaling Pathway/physiology , Ankyrin Repeat , Axin Protein/metabolism , Cell Line , Crystallography, X-Ray , HCT116 Cells , HEK293 Cells , Humans , Mutation , Protein Binding , Tankyrases/chemistry , Ubiquitin Thiolesterase/chemistry , Ubiquitin Thiolesterase/genetics , Wnt Signaling Pathway/genetics
7.
Genes Dev ; 30(15): 1718-30, 2016 08 01.
Article in English | MEDLINE | ID: mdl-27542828

ABSTRACT

The ubiquitin-proteasome system (UPS) and autophagy are two major intracellular degradative mechanisms that mediate the turnover of complementary repertoires of intracellular proteomes. Simultaneously activating both UPS and autophagy might provide a powerful strategy for the clearance of misfolded proteins. However, it is not clear whether UPS and autophagy can be controlled by a common regulatory mechanism. K48 deubiquitination by USP14 is known to inhibit UPS. Here we show that USP14 regulates autophagy by negatively controlling K63 ubiquitination of Beclin 1. Furthermore, we show that activation of USP14 by Akt-mediated phosphorylation provides a mechanism for Akt to negatively regulate autophagy by promoting K63 deubiquitination. Our study suggests that Akt-regulated USP14 activity modulates both proteasomal degradation and autophagy through controlling K48 and K63 ubiquitination, respectively. Therefore, regulation of USP14 provides a mechanism for Akt to control both proteasomal and autophagic degradation. We propose that inhibition of USP14 may provide a strategy to promote both UPS and autophagy for developing novel therapeutics targeting neurodegenerative diseases.


Subject(s)
Autophagy/physiology , Beclin-1/metabolism , Ubiquitin Thiolesterase/metabolism , Ubiquitination , Class III Phosphatidylinositol 3-Kinases/metabolism , Gene Expression , HEK293 Cells , Humans , Oncogene Protein v-akt/metabolism , Phosphorylation , Ubiquitin Thiolesterase/genetics
8.
Proc Natl Acad Sci U S A ; 117(9): 4959-4970, 2020 03 03.
Article in English | MEDLINE | ID: mdl-32071228

ABSTRACT

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.


Subject(s)
Apoptosis/physiology , Necroptosis/physiology , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Stroke/metabolism , Animals , Brain Injuries/metabolism , Cell Death , Inflammation/pathology , MAP Kinase Kinase Kinases/metabolism , Male , Mice , Mice, Knockout , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Stroke/pathology
9.
Genes Dev ; 29(2): 184-96, 2015 Jan 15.
Article in English | MEDLINE | ID: mdl-25593308

ABSTRACT

Vacuolar protein-sorting 34 (Vps34), the catalytic subunit in the class III PtdIns3 (phosphatidylinositol 3) kinase complexes, mediates the production of PtdIns3P, a key intracellular lipid involved in regulating autophagy and receptor degradation. However, the signal transduction pathways by which extracellular signals regulate Vps34 complexes and the downstream cellular mechanisms are not well understood. Here we show that DNA damage-activated mitotic arrest and CDK activation lead to the phosphorylation of Vps34, which provides a signal to promote its ubiquitination and proteasomal degradation mediated by FBXL20 (an F-box protein) and the associated Skp1 (S-phase kinase-associated protein-1)-Cullin1 complex, leading to inhibition of autophagy and receptor endocytosis. Furthermore, we show that the expression of FBXL20 is regulated by p53-dependent transcription. Our study provides a molecular pathway by which DNA damage regulates Vps34 complexes and its downstream mechanisms, including autophagy and receptor endocytosis, through SCF (Skp1-Cul1-F-box)-mediated ubiquitination and degradation. Since the expression of FBXL20 is regulated by p53-dependent transcription, the control of Vps34 ubiquitination and proteasomal degradation by FBXL20 and the associated SCF complex expression provides a novel checkpoint for p53 to regulate autophagy and receptor degradation in DNA damage response.


Subject(s)
Autophagy/genetics , Cell Cycle Checkpoints/physiology , Class III Phosphatidylinositol 3-Kinases/metabolism , F-Box Proteins/metabolism , Tumor Suppressor Protein p53/metabolism , Cell Line, Tumor , Class III Phosphatidylinositol 3-Kinases/genetics , DNA Damage/physiology , Endocytosis/physiology , HeLa Cells , Humans , Phosphorylation , Proteasome Endopeptidase Complex/metabolism , S-Phase Kinase-Associated Proteins/metabolism , Signal Transduction , Ubiquitination
10.
Nat Struct Mol Biol ; 31(2): 232-245, 2024 Feb.
Article in English | MEDLINE | ID: mdl-38177673

ABSTRACT

Autophagy is a lysosome-dependent degradation pathway essential for cellular homeostasis, which decreases with age. However, it is unclear how aging induces autophagy decline. Here we show the role of protein S-palmitoylation in autophagy. We identify the palmitoyl acyltransferase DHHC5 as a regulator of autophagy by mediating the palmitoylation of beclin 1, which in turn promotes the formation of ATG14L-containing class III phosphatidylinositol-3-kinase complex I and its lipid kinase activity by promoting the hydrophobic interactions between beclin 1 and adapter proteins ATG14L and VPS15. In aging brains of human and nonhuman primate, the levels of DHHC5 exhibit a marked decrease in expression. We show that DHHC5 deficiency in neurons leads to reduced cellular protein homeostasis in two established murine models of Alzheimer's disease, which exaggerates neurodegeneration in an autophagy-dependent manner. These findings identify reduction of DHHC5-mediated beclin 1 S-palmitoylation as an underlying mechanism by which aging induces autophagy decline.


Subject(s)
Acyltransferases , Apoptosis Regulatory Proteins , Autophagy , Beclin-1 , Lipoylation , Animals , Humans , Mice , Acyltransferases/metabolism , Apoptosis Regulatory Proteins/metabolism , Beclin-1/genetics , Beclin-1/metabolism , Membrane Proteins/metabolism , Phosphorylation
11.
Nat Cell Biol ; 26(5): 757-769, 2024 May.
Article in English | MEDLINE | ID: mdl-38538834

ABSTRACT

Gasdermin D (GSDMD) is the executor of pyroptosis, which is important for host defence against pathogen infection. Following activation, caspase-mediated cleavage of GSDMD releases an amino-terminal fragment (GSDMD-NT), which oligomerizes and forms pores in the plasma membrane, leading to cell death and release of proinflammatory cytokines. The spatial and temporal regulation of this process in cells remains unclear. Here we identify GSDMD as a substrate for reversible S-palmitoylation on C192 during pyroptosis. The palmitoyl acyltransferase DHHC7 palmitoylates GSDMD to direct its cleavage by caspases. Subsequently, palmitoylation of GSDMD-NT promotes its translocation to the plasma membrane, where APT2 depalmitoylates GSDMD-NT to unmask the C192 residue and promote GSDMD-NT oligomerization. Perturbation of either palmitoylation or depalmitoylation suppresses pyroptosis, leading to increased survival of mice with lipopolysaccharide-induced lethal septic shock and increased sensitivity to bacterial infection. Our findings reveal a model through which a palmitoylation-depalmitoylation relay spatiotemporally controls GSDMD activation during pyroptosis.


Subject(s)
Acyltransferases , Gasdermins , Lipoylation , Phosphate-Binding Proteins , Pyroptosis , Animals , Humans , Mice , Acetyltransferases , Acyltransferases/metabolism , Acyltransferases/genetics , Caspases/metabolism , Cell Membrane/metabolism , HEK293 Cells , Intracellular Signaling Peptides and Proteins/metabolism , Intracellular Signaling Peptides and Proteins/genetics , Lipopolysaccharides/pharmacology , Mice, Inbred C57BL , Neoplasm Proteins/metabolism , Neoplasm Proteins/genetics , Phosphate-Binding Proteins/metabolism , Phosphate-Binding Proteins/genetics , Pyroptosis/genetics , Shock, Septic/metabolism , Shock, Septic/pathology , Shock, Septic/genetics
12.
Nat Cell Biol ; 26(4): 567-580, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38538837

ABSTRACT

Defects in the prelamin A processing enzyme caused by loss-of-function mutations in the ZMPSTE24 gene are responsible for a spectrum of progeroid disorders characterized by the accumulation of farnesylated prelamin A. Here we report that defective prelamin A processing triggers nuclear RIPK1-dependent signalling that leads to necroptosis and inflammation. We show that accumulated prelamin A recruits RIPK1 to the nucleus to facilitate its activation upon tumour necrosis factor stimulation in ZMPSTE24-deficient cells. Kinase-activated RIPK1 then promotes RIPK3-mediated MLKL activation in the nucleus, leading to nuclear envelope disruption and necroptosis. This signalling relies on prelamin A farnesylation, which anchors prelamin A to nuclear envelope to serve as a nucleation platform for necroptosis. Genetic inactivation of necroptosis ameliorates the progeroid phenotypes in Zmpste24-/- mice. Our findings identify an unconventional nuclear necroptosis pathway resulting from ZMPSTE24 deficiency with pathogenic consequences in progeroid disorder and suggest RIPK1 as a feasible target for prelamin A-associated progeroid disorders.


Subject(s)
Lamin Type A , Necroptosis , Animals , Mice , Lamin Type A/genetics , Lamin Type A/metabolism , Mutation , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Tumor Necrosis Factor-alpha/metabolism
13.
J Clin Invest ; 134(13)2024 May 14.
Article in English | MEDLINE | ID: mdl-38743492

ABSTRACT

Steatotic donor livers are becoming more and more common in liver transplantation. However, the current use of steatotic grafts is less acceptable than normal grafts due to their higher susceptibility to ischemia/reperfusion (I/R) injury. To investigate the mechanism underlying the susceptibility of steatotic liver to I/R injury, we detected cell death markers and inflammation in clinical donor livers and animal models. We found that caspase-8-mediated hepatic apoptosis is activated in steatotic liver I/R injury. However, ablation of caspase-8 only slightly mitigated steatotic liver I/R injury without affecting inflammation. We further demonstrated that RIPK1 kinase induces both caspase-8-mediated apoptosis and cell death-independent inflammation. Inhibition of RIPK1 kinase significantly protects against steatotic liver I/R injury by alleviating both hepatic apoptosis and inflammation. Additionally, we found that RIPK1 activation is induced by Z-DNA binding protein 1 (ZBP1) but not the canonical TNF-α pathway during steatotic liver I/R injury. Deletion of ZBP1 substantially decreases the steatotic liver I/R injury. Mechanistically, ZBP1 is amplified by palmitic acid-activated JNK pathway in steatotic livers. Upon I/R injury, excessive reactive oxygen species trigger ZBP1 activation by inducing its aggregation independent of the Z-nucleic acids sensing action in steatotic livers, leading to the kinase activation of RIPK1 and the subsequent aggravation of liver injury. Thus, ZBP1-mediated RIPK1-driven apoptosis and inflammation exacerbate steatotic liver I/R injury, which could be targeted to protect steatotic donor livers during transplantation.


Subject(s)
Apoptosis , Caspase 8 , Fatty Liver , RNA-Binding Proteins , Receptor-Interacting Protein Serine-Threonine Kinases , Reperfusion Injury , Reperfusion Injury/metabolism , Reperfusion Injury/pathology , Reperfusion Injury/genetics , Animals , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Mice , Humans , Fatty Liver/metabolism , Fatty Liver/pathology , Fatty Liver/genetics , RNA-Binding Proteins/metabolism , RNA-Binding Proteins/genetics , Caspase 8/metabolism , Caspase 8/genetics , Liver/pathology , Liver/metabolism , Mice, Knockout , Inflammation/pathology , Inflammation/metabolism , Inflammation/genetics , Male , Liver Transplantation , Mice, Inbred C57BL
14.
Nat Microbiol ; 9(8): 2144-2159, 2024 Aug.
Article in English | MEDLINE | ID: mdl-38844594

ABSTRACT

Nutritional status and pyroptosis are important for host defence against infections. However, the molecular link that integrates nutrient sensing into pyroptosis during microbial infection is unclear. Here, using metabolic profiling, we found that Yersinia pseudotuberculosis infection results in a significant decrease in intracellular glucose levels in macrophages. This leads to activation of the glucose and energy sensor AMPK, which phosphorylates the essential kinase RIPK1 at S321 during caspase-8-mediated pyroptosis. This phosphorylation inhibits RIPK1 activation and thereby restrains pyroptosis. Boosting the AMPK-RIPK1 cascade by glucose deprivation, AMPK agonists, or RIPK1-S321E knockin suppresses pyroptosis, leading to increased susceptibility to Y. pseudotuberculosis infection in mice. Ablation of AMPK in macrophages or glucose supplementation in mice is protective against infection. Thus, we reveal a molecular link between glucose sensing and pyroptosis, and unveil a mechanism by which Y. pseudotuberculosis reduces glucose levels to impact host AMPK activation and limit host pyroptosis to facilitate infection.


Subject(s)
AMP-Activated Protein Kinases , Glucose , Macrophages , Pyroptosis , Receptor-Interacting Protein Serine-Threonine Kinases , Yersinia pseudotuberculosis , Animals , Mice , AMP-Activated Protein Kinases/metabolism , Glucose/metabolism , Macrophages/metabolism , Macrophages/microbiology , Yersinia pseudotuberculosis/metabolism , Yersinia pseudotuberculosis/pathogenicity , Phosphorylation , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Yersinia pseudotuberculosis Infections/microbiology , Yersinia pseudotuberculosis Infections/metabolism , Mice, Inbred C57BL
15.
Nat Commun ; 14(1): 2715, 2023 05 11.
Article in English | MEDLINE | ID: mdl-37169760

ABSTRACT

Hepatocyte apoptosis plays an essential role in the progression of nonalcoholic steatohepatitis (NASH). However, the molecular mechanisms underlying hepatocyte apoptosis remain unclear. Here, we identify UDP-glucose 6-dehydrogenase (UGDH) as a suppressor of NASH-associated liver damage by inhibiting RIPK1 kinase-dependent hepatocyte apoptosis. UGDH is progressively reduced in proportion to NASH severity. UGDH absence from hepatocytes hastens the development of liver damage in male mice with NASH, which is suppressed by RIPK1 kinase-dead knockin mutation. Mechanistically, UGDH suppresses RIPK1 by converting UDP-glucose to UDP-glucuronate, the latter directly binds to the kinase domain of RIPK1 and inhibits its activation. Recovering UDP-glucuronate levels, even after the onset of NASH, improved liver damage. Our findings reveal a role for UGDH and UDP-glucuronate in NASH pathogenesis and uncover a mechanism by which UDP-glucuronate controls hepatocyte apoptosis by targeting RIPK1 kinase, and suggest UDP-glucuronate metabolism as a feasible target for more specific treatment of NASH-associated liver damage.


Subject(s)
Non-alcoholic Fatty Liver Disease , Animals , Male , Mice , Glucose/metabolism , Glucuronates/metabolism , Hepatocytes/metabolism , Liver/metabolism , Non-alcoholic Fatty Liver Disease/genetics , Non-alcoholic Fatty Liver Disease/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Uridine Diphosphate/metabolism
16.
Signal Transduct Target Ther ; 8(1): 451, 2023 12 13.
Article in English | MEDLINE | ID: mdl-38086800

ABSTRACT

Amyotrophic lateral sclerosis (ALS) is a devastating fatal neurodegenerative disease with no cure. Receptor-interacting protein kinase 1 (RIPK1) has been proposed to mediate pathogenesis of ALS. Primidone has been identified as an old drug that can also inhibit RIPK1 kinase. We conducted a drug-repurposing biomarker study of primidone as a RIPK1 inhibitor using SOD1G93A mice and ALS patients. SOD1G93A mice treated with primidone showed significant delay of symptomatic onset and improved motor performance. One-hundred-sixty-two ALS participants dosed daily with primidone (62.5 mg) completed 24-week follow-up. A significant reduction was showed in serum levels of RIPK1 and IL-8, which were significantly higher in ALS patients than that of healthy controls (P < 0.0001). Serum RIPK1 levels were correlated positively with the severity of bulbar symptoms (P < 0.05). Our study suggests that serum levels of RIPK1 and IL-8 in peripheral can be used as clinical biomarkers for the activation of RIPK1 in central nervous system in human ALS patients. Repurposing primidone may provide a promising therapeutic strategy for ALS. The effect of primidone for the treatment of other inflammatory diseases may also be considered, since the activation of RIPK1 has been implicated in mediating a variety of inflammatory diseases including COVID-19-associated cytokine release syndrome (CRS). (ChiCTR2200060149).


Subject(s)
Amyotrophic Lateral Sclerosis , Neurodegenerative Diseases , Animals , Humans , Mice , Amyotrophic Lateral Sclerosis/drug therapy , Amyotrophic Lateral Sclerosis/genetics , Amyotrophic Lateral Sclerosis/metabolism , Biomarkers , Interleukin-8/genetics , Mice, Transgenic , Motor Neurons/metabolism , Motor Neurons/pathology , Neurodegenerative Diseases/metabolism , Primidone/metabolism , Primidone/pharmacology , Primidone/therapeutic use , Protein Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/pharmacology , Superoxide Dismutase/metabolism , Superoxide Dismutase/pharmacology , Superoxide Dismutase/therapeutic use , Superoxide Dismutase-1/genetics , Superoxide Dismutase-1/metabolism , Superoxide Dismutase-1/pharmacology
17.
Nat Cell Biol ; 25(7): 950-962, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37400498

ABSTRACT

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.


Subject(s)
Necroptosis , Receptors, Tumor Necrosis Factor, Type I , Humans , Receptors, Tumor Necrosis Factor, Type I/genetics , Receptors, Tumor Necrosis Factor, Type I/metabolism , Hydroxylation , Hypoxia , Proline/metabolism , Inflammation , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism
18.
Science ; 380(6652): 1372-1380, 2023 06 30.
Article in English | MEDLINE | ID: mdl-37384704

ABSTRACT

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.


Subject(s)
AMP-Activated Protein Kinases , Energy Metabolism , Necroptosis , Receptor-Interacting Protein Serine-Threonine Kinases , Stress, Physiological , Animals , Mice , AMP-Activated Protein Kinases/genetics , AMP-Activated Protein Kinases/metabolism , Phosphorylation , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Inflammation/metabolism , Ischemia/metabolism
19.
Nat Commun ; 13(1): 7153, 2022 11 22.
Article in English | MEDLINE | ID: mdl-36414671

ABSTRACT

Activation of RIPK1-driven cell death and inflammation play important roles in the progression of nonalcoholic steatohepatitis (NASH). However, the mechanism underlying RIPK1 activation in NASH remains unclear. Here we identified SENP1, a SUMO-specific protease, as a key endogenous inhibitor of RIPK1. SENP1 is progressively reduced in proportion to NASH severity in patients. Hepatocyte-specific SENP1-knockout mice develop spontaneous NASH-related phenotypes in a RIPK1 kinase-dependent manner. We demonstrate that SENP1 deficiency sensitizes cells to RIPK1 kinase-dependent apoptosis by promoting RIPK1 activation following TNFα stimulation. Mechanistically, SENP1 deSUMOylates RIPK1 in TNF-R1 signaling complex (TNF-RSC), keeping RIPK1 in check. Loss of SENP1 leads to SUMOylation of RIPK1, which re-orchestrates TNF-RSC and modulates the ubiquitination patterns and activity of RIPK1. Notably, genetic inhibition of RIPK1 effectively reverses disease progression in hepatocyte-specific SENP1-knockout male mice with high-fat-diet-induced nonalcoholic fatty liver. We propose that deSUMOylation of RIPK1 by SENP1 provides a pathophysiologically relevant cell death-restricting checkpoint that modulates RIPK1 activation in the pathogenesis of nonalcoholic steatohepatitis.


Subject(s)
Non-alcoholic Fatty Liver Disease , Male , Mice , Animals , Non-alcoholic Fatty Liver Disease/metabolism , Apoptosis , Inflammation/pathology , Ubiquitination , Hepatocytes/metabolism , Mice, Knockout , Phosphotransferases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Cysteine Endopeptidases/genetics , Cysteine Endopeptidases/metabolism
20.
Cell Res ; 32(7): 621-637, 2022 07.
Article in English | MEDLINE | ID: mdl-35661830

ABSTRACT

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.


Subject(s)
Amyotrophic Lateral Sclerosis , Amyotrophic Lateral Sclerosis/genetics , Animals , Apoptosis , Chromatin , Chromatin Assembly and Disassembly , Cytokines/metabolism , Inflammation/pathology , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism
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