Cell fate determined by the activation balance between PKR and SPHK1

AbstractDouble-stranded RNA (dsRNA)-dependent protein kinase R (PKR) activation via autophosphorylation is the central cellular response to stress that promotes cell death or apoptosis. However, the key factors and mechanisms behind the simultaneous activation of pro-survival signaling pathways remain unknown. We have discovered a novel regulatory mechanism for the maintenance of cellular homeostasis that relies on the phosphorylation interplay between sphingosine kinase 1 (SPHK1) and PKR during exogenous stress. We identified SPHK1 as a previously unrecognized PKR substrate. Phosphorylated SPHK1, a central kinase, mediates the activation of PKR-induced pro-survival pathways by the S1P/S1PR1/MAPKs/IKKα signal axis, and antagonizes PKR-mediated endoplasmic reticulum (ER) stress signal transduction under stress conditions. Otherwise, phosphorylated SPHK1 also acts as the negative feedback factor, preferentially binding to the latent form of PKR at the C-terminal kinase motif, inhibiting the homodimerization of PKR, suppressing PKR autophosphorylation, and reducing the signaling strength for cell death and apoptosis. Our results suggest that the balance of the activation levels between PKR and SPHK1, a probable hallmark of homeostasis maintenance, determines cell fate during cellular stress response.

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microRNA-378 promotes autophagy and inhibits apoptosis in skeletal muscle

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1803377115 ◽

2018 ◽

Vol 115 (46) ◽

pp. E10849-E10858 ◽

Cited By ~ 25

Author(s):

Yan Li ◽

Jingjing Jiang ◽

Wei Liu ◽

Hui Wang ◽

Lei Zhao ◽

...

Keyword(s):

Skeletal Muscle ◽

Cell Death ◽

Cell Fate ◽

Metabolic Regulation ◽

Mammalian Target Of Rapamycin ◽

Metabolic Stress ◽

Muscle Weight ◽

Dependent Protein ◽

Metabolic Checkpoints

The metabolic regulation of cell death is sophisticated. A growing body of evidence suggests the existence of multiple metabolic checkpoints that dictate cell fate in response to metabolic fluctuations. However, whether microRNAs (miRNAs) are able to respond to metabolic stress, reset the threshold of cell death, and attempt to reestablish homeostasis is largely unknown. Here, we show that miR-378/378* KO mice cannot maintain normal muscle weight and have poor running performance, which is accompanied by impaired autophagy, accumulation of abnormal mitochondria, and excessive apoptosis in skeletal muscle, whereas miR-378 overexpression is able to enhance autophagy and repress apoptosis in skeletal muscle of mice. Our in vitro data show that metabolic stress-responsive miR-378 promotes autophagy and inhibits apoptosis in a cell-autonomous manner. Mechanistically, miR-378 promotes autophagy initiation through the mammalian target of rapamycin (mTOR)/unc-51-like autophagy activating kinase 1 (ULK1) pathway and sustains autophagy via Forkhead box class O (FoxO)-mediated transcriptional reinforcement by targeting phosphoinositide-dependent protein kinase 1 (PDK1). Meanwhile, miR-378 suppresses intrinsic apoptosis initiation directly through targeting an initiator caspase—Caspase 9. Thus, we propose that miR-378 is a critical component of metabolic checkpoints, which integrates metabolic information into an adaptive response to reduce the propensity of myocytes to undergo apoptosis by enhancing the autophagic process and blocking apoptotic initiation. Lastly, our data suggest that inflammation-induced down-regulation of miR-378 might contribute to the pathogenesis of muscle dystrophy.

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Importance of the bioenergetic reserve capacity in response to cardiomyocyte stress induced by 4-hydroxynonenal

Biochemical Journal ◽

10.1042/bj20090934 ◽

2009 ◽

Vol 424 (1) ◽

pp. 99-107 ◽

Cited By ~ 197

Author(s):

Bradford G. Hill ◽

Brian P. Dranka ◽

Luyun Zou ◽

John C. Chatham ◽

Victor M. Darley-Usmar

Keyword(s):

Cell Death ◽

Cellular Response ◽

Protein Modification ◽

Ventricular Myocytes ◽

Critical Role ◽

Reserve Capacity ◽

Energy Demands ◽

Lipid Species ◽

Cellular Context ◽

Response To Stress

Mitochondria play a critical role in mediating the cellular response to oxidants formed during acute and chronic cardiac dysfunction. It is widely assumed that, as cells are subjected to stress, mitochondria are capable of drawing upon a ‘reserve capacity’ which is available to serve the increased energy demands for maintenance of organ function, cellular repair or detoxification of reactive species. This hypothesis further implies that impairment or depletion of this putative reserve capacity ultimately leads to excessive protein damage and cell death. However, it has been difficult to fully evaluate this hypothesis since much of our information about the response of the mitochondrion to oxidative stress derives from studies on mitochondria isolated from their cellular context. Therefore the goal of the present study was to determine whether ‘bioenergetic reserve capacity’ does indeed exist in the intact myocyte and whether it is utilized in response to stress induced by the pathologically relevant reactive lipid species HNE (4-hydroxynonenal). We found that intact rat neonatal ventricular myocytes exhibit a substantial bioenergetic reserve capacity under basal conditions; however, on exposure to pathologically relevant concentrations of HNE, oxygen consumption was increased until this reserve capacity was depleted. Exhaustion of the reserve capacity by HNE treatment resulted in inhibition of respiration concomitant with protein modification and cell death. These data suggest that oxidized lipids could contribute to myocyte injury by decreasing the bioenergetic reserve capacity. Furthermore, these studies demonstrate the utility of measuring the bioenergetic reserve capacity for assessing or predicting the response of cells to stress.

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53BP1 Mediates ATR-Chk1 Signaling and Protects Replication Forks under Conditions of Replication Stress

Molecular and Cellular Biology ◽

10.1128/mcb.00472-17 ◽

2018 ◽

Vol 38 (8) ◽

Cited By ~ 25

Author(s):

Joonyoung Her ◽

Chandni Ray ◽

Jake Altshuler ◽

Haiyan Zheng ◽

Samuel F. Bunting

Keyword(s):

Cell Death ◽

Cellular Response ◽

Ex Vivo ◽

Replication Stress ◽

Strand Break ◽

Replication Forks ◽

P53 Signaling ◽

Dna Double Strand Break ◽

Short Term Exposure ◽

Stress Signal

ABSTRACTComplete replication of the genome is an essential prerequisite for normal cell division, but a variety of factors can block the replisome, triggering replication stress and potentially causing mutation or cell death. The cellular response to replication stress involves recruitment of proteins to stabilize the replication fork and transmit a stress signal to pause the cell cycle and allow fork restart. We find that the ubiquitously expressed DNA damage response factor 53BP1 is required for the normal response to replication stress. Using primary,ex vivoB cells, we showed that a population of 53BP1−/−cells in early S phase is hypersensitive to short-term exposure to three different agents that induce replication stress. 53BP1 localizes to a subset of replication forks following induced replication stress, and an absence of 53BP1 leads to defective ATR-Chk1-p53 signaling and caspase 3-mediated cell death. Nascent replicated DNA additionally undergoes degradation in 53BP1−/−cells. These results show that 53BP1 plays an important role in protecting replication forks during the cellular response to replication stress, in addition to the previously characterized role of 53BP1 in DNA double-strand break repair.

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Yeast chronological lifespan and proteotoxic stress: is autophagy good or bad?

Biochemical Society Transactions ◽

10.1042/bst0391466 ◽

2011 ◽

Vol 39 (5) ◽

pp. 1466-1470 ◽

Cited By ~ 14

Author(s):

Belém Sampaio-Marques ◽

Carolina Felgueiras ◽

Alexandra Silva ◽

Fernando Rodrigues ◽

Paula Ludovico

Keyword(s):

Cell Death ◽

Cellular Response ◽

Molecular Mechanisms ◽

Nutrient Sensing ◽

Signalling Pathways ◽

Aging Effects ◽

Tor Pathway ◽

Chronological Lifespan ◽

Proteotoxic Stress ◽

Response To Stress

Autophagy, a highly conserved proteolytic mechanism of quality control, is essential for the maintenance of metabolic and cellular homoeostasis and for an efficient cellular response to stress. Autophagy declines with aging and is believed to contribute to different aspects of the aging phenotype. The nutrient-sensing pathways PKA (protein kinase A), Sch9 and TOR (target of rapamycin), involved in the regulation of yeast lifespan, also converge on a common targeted process: autophagy. The molecular mechanisms underlying the regulation of autophagy and aging by these signalling pathways in yeast, with special attention to the TOR pathway, are discussed in the present paper. The question of whether or not autophagy could contribute to yeast cell death occurring during CLS (chronological lifespan) is discussed in the light of our findings obtained after autophagy activation promoted by proteotoxic stress. Autophagy progressively increases in cells expressing the aggregation-prone protein α-synuclein and seems to participate in the early cell death and shortening of CLS under these conditions, highlighting that autophagic activity should be maintained below physiological levels to exert its promising anti-aging effects.

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Nuclear iASPP determines cell fate by selectively inhibiting either p53 or NF-κB

Cell Death Discovery ◽

10.1038/s41420-021-00582-1 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Wenjie Ge ◽

Yudong Wang ◽

Shanliang Zheng ◽

Dong Zhao ◽

Xingwen Wang ◽

...

Keyword(s):

Cell Fate ◽

Cellular Response ◽

Dependent Manner ◽

Inhibitory Effects ◽

Functional Interaction ◽

Signaling Systems ◽

Optimal Outcomes ◽

A Cell ◽

Response To Stress ◽

Biological Outcomes

Abstractp53 and NF-κBp65 are essential transcription factors (TFs) in the cellular response to stress. Two signaling systems can often be entwined together and generally produce opposing biological outcomes in a cell context-dependent manner. Inhibitor of apoptosis-stimulating protein of p53 (iASPP) has the potential to inhibit both p53 and NF-κBp65, yet how such activities of iASPP are integrated with cancer remains unknown. Here, we utilized different cell models with diverse p53/NF-κBp65 activities. An iASPP(295–828) mutant, which is exclusively located in the nucleus and has been shown to be essential for its inhibitory effects on p53/NF-κBp65, was used to investigate the functional interaction between iASPP and the two TFs. The results showed that iASPP inhibits apoptosis under conditions when p53 is activated, while it can also elicit a proapoptotic effect when NF-κBp65 alone is activated. Furthermore, we demonstrated that iASPP inhibited the transcriptional activity of p53/NF-κBp65, but with a preference toward p53, thereby producing an antiapoptotic outcome when both TFs were simultaneously activated. This may be due to stronger binding between p53 and iASPP than NF-κBp65 and iASPP. Overall, these findings provide important insights into how the activities of p53 and NF-κBp65 are modulated by iASPP. Despite being a well-known oncogene, iASPP may have a proapoptotic role, which will guide the development of iASPP-targeted therapies to reach optimal outcomes in the future.

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Multiplexed biochemical imaging reveals caspase activation patterns underlying single cell fate

10.1101/427237 ◽

2018 ◽

Author(s):

Maximilian W. Fries ◽

Kalina T. Haas ◽

Suzan Ber ◽

John Saganty ◽

Emma K. Richardson ◽

...

Keyword(s):

Cell Death ◽

Single Cell ◽

Cell Fate ◽

Genetic Heterogeneity ◽

Cellular Response ◽

Single Cells ◽

Caspase Activation ◽

Cell Fate Decisions ◽

Network Activation ◽

Biochemical Imaging

The biochemical activities underlying cell-fate decisions vary profoundly even in genetically identical cells. But such non-genetic heterogeneity remains refractory to current imaging methods, because their capacity to monitor multiple biochemical activities in single living cells over time remains limited1. Here, we deploy a family of newly designed GFP-like sensors (NyxBits) with fast photon-counting electronics and bespoke analytics (NyxSense) in multiplexed biochemical imaging, to define a network determining the fate of single cells exposed to the DNA-damaging drug cisplatin. By simultaneously imaging a tri-nodal network comprising the cell-death proteases Caspase-2, -3 and -92, we reveal unrecognized single-cell heterogeneities in the dynamics and amplitude of caspase activation that signify survival versus cell death via necrosis or apoptosis. Non-genetic heterogeneity in the pattern of caspase activation recapitulates traits of therapy resistance previously ascribed solely to genetic causes3,4. Chemical inhibitors that alter these patterns can modulate in a predictable manner the phenotypic landscape of the cellular response to cisplatin. Thus, multiplexed biochemical imaging reveals cellular populations and biochemical states, invisible to other methods, underlying therapeutic responses to an anticancer drug. Our work develops widely applicable tools to monitor the dynamic activation of biochemical networks at single-cell resolution. It highlights the necessity to resolve patterns of network activation in single cells, rather than the average state of individual nodes, to define, and potentially control, mechanisms underlying cellular decisions in health and disease.

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The RNase Rny1p cleaves tRNAs and promotes cell death during oxidative stress in Saccharomyces cerevisiae

The Journal of Cell Biology ◽

10.1083/jcb.200811119 ◽

2009 ◽

Vol 185 (1) ◽

pp. 43-50 ◽

Cited By ~ 183

Author(s):

Debrah M. Thompson ◽

Roy Parker

Keyword(s):

Oxidative Stress ◽

Cell Death ◽

Cell Survival ◽

Cellular Response ◽

Cellular Damage ◽

Transfer Rnas ◽

Endonucleolytic Cleavage ◽

Response To Stress ◽

Rnase T2

The cellular response to stress conditions involves a decision between survival or cell death when damage is severe. A conserved stress response in eukaryotes involves endonucleolytic cleavage of transfer RNAs (tRNAs). The mechanism and significance of such tRNA cleavage is unknown. We show that in yeast, tRNAs are cleaved by the RNase T2 family member Rny1p, which is released from the vacuole into the cytosol during oxidative stress. Rny1p modulates yeast cell survival during oxidative stress independently of its catalytic ability. This suggests that upon release to the cytosol, Rny1p promotes cell death by direct interactions with downstream components. Thus, detection of Rny1p, and possibly its orthologues, in the cytosol may be a conserved mechanism for assessing cellular damage and determining cell survival, analogous to the role of cytochrome c as a marker for mitochondrial damage.

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Target Misfolded Protein Clearance Pathway for Cancer Therapy

Proceedings ◽

10.3390/proceedings2019040045 ◽

2020 ◽

Vol 40 (1) ◽

pp. 45

Author(s):

Apar Pataer

Keyword(s):

Cell Death ◽

Cancer Therapy ◽

Cancer Cells ◽

Prion Proteins ◽

Misfolded Protein ◽

Breast Cancer Patients ◽

Protein Kinase R ◽

Protein Clearance ◽

Dependent Protein

The role of RNA-dependent protein kinase R (PKR) and its association with misfolded protein expression in cancer cells are unclear. Herein we report that PKR regulates misfolded protein clearance by preventing it release through exosomes and promoting lysosomal degradation of misfolded prion proteins in cancer cells. We demonstrated that PKR contributes to the lysosome function and regulates misfolded prion protein clearance. We hypothesized that PKR-associated lysosome function is critical for cancer but not normal cell survival, representing an effective approach for highly targeted cancer therapy. In screening a compound library, we identified two PKR-associated compound 1 did not affect normal cells but selectively induced cell death in cancer cells depending on their PKR expression status. Pac 1 significantly inhibited the growth of human lung and breast xenograft tumors in mice with no toxicity. Pac 1 binds to PI4K2A and disrupts the PKR/PI4K2A associated lysosome complex, contributing to destabilization of cancer cell lysosomes and triggering cell death. We observed that PKR and PI4K2A play significant prognostic roles in breast cancer patients. These results demonstrate that targeting of a PI4K2A/PKR lysosome complex may be an effective approach for cancer therapy.

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Therapeutic targeting of the PI4K2A/PKR lysosome network is critical for misfolded protein clearance and survival in cancer cells

Oncogene ◽

10.1038/s41388-019-1010-4 ◽

2019 ◽

Vol 39 (4) ◽

pp. 801-813 ◽

Cited By ~ 2

Author(s):

Apar Pataer ◽

Bulent Ozpolat ◽

RuPing Shao ◽

Neil R. Cashman ◽

Steven S. Plotkin ◽

...

Keyword(s):

Cell Death ◽

Cancer Therapy ◽

Cancer Cells ◽

Prion Proteins ◽

Misfolded Protein ◽

Breast Cancer Patients ◽

Protein Kinase R ◽

Protein Clearance ◽

Dependent Protein

Abstract The role of RNA-dependent protein kinase R (PKR) and its association with misfolded protein expression in cancer cells are unclear. Herein we report that PKR regulates misfolded protein clearance by preventing it release through exosomes and promoting lysosomal degradation of misfolded prion proteins in cancer cells. We demonstrated that PKR contributes to the lysosome function and regulates misfolded prion protein clearance. We hypothesized that PKR-associated lysosome function is critical for cancer but not normal cell survival, representing an effective approach for highly targeted cancer therapy. In screening a compound library, we identified two PKR-associated compounds 1 and 2 (Pac 1 and 2) did not affect normal cells but selectively induced cell death in cancer cells depending on their PKR expression status. Pac 1 significantly inhibited the growth of human lung and breast xenograft tumors in mice with no toxicity. Pac 1 binds to PI4K2A and disrupts the PKR/PI4K2A-associated lysosome complex, contributing to destabilization of cancer cell lysosomes and triggering cell death. We observed that PKR and PI4K2A play significant prognostic roles in breast cancer patients. These results demonstrate that targeting of a PI4K2A/PKR lysosome complex may be an effective approach for cancer therapy.

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Telomeres and Aging

Physiological Reviews ◽

10.1152/physrev.00026.2007 ◽

2008 ◽

Vol 88 (2) ◽

pp. 557-579 ◽

Cited By ~ 626

Author(s):

Geraldine Aubert ◽

Peter M. Lansdorp

Keyword(s):

Telomere Length ◽

Cell Fate ◽

Cellular Response ◽

Genome Instability ◽

Somatic Cells ◽

Growth Stimulation ◽

Dyskeratosis Congenita ◽

Telomere Attrition ◽

Response To Stress

Telomeres play a central role in cell fate and aging by adjusting the cellular response to stress and growth stimulation on the basis of previous cell divisions and DNA damage. At least a few hundred nucleotides of telomere repeats must “cap” each chromosome end to avoid activation of DNA repair pathways. Repair of critically short or “uncapped” telomeres by telomerase or recombination is limited in most somatic cells and apoptosis or cellular senescence is triggered when too many “uncapped” telomeres accumulate. The chance of the latter increases as the average telomere length decreases. The average telomere length is set and maintained in cells of the germline which typically express high levels of telomerase. In somatic cells, telomere length is very heterogeneous but typically declines with age, posing a barrier to tumor growth but also contributing to loss of cells with age. Loss of (stem) cells via telomere attrition provides strong selection for abnormal and malignant cells, a process facilitated by the genome instability and aneuploidy triggered by dysfunctional telomeres. The crucial role of telomeres in cell turnover and aging is highlighted by patients with 50% of normal telomerase levels resulting from a mutation in one of the telomerase genes. Short telomeres in such patients are implicated in a variety of disorders including dyskeratosis congenita, aplastic anemia, pulmonary fibrosis, and cancer. Here the role of telomeres and telomerase in human aging and aging-associated diseases is reviewed.

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