scholarly journals Bioenergetic and autophagic control by Sirt3 in response to nutrient deprivation in mouse embryonic fibroblasts

2013 ◽  
Vol 454 (2) ◽  
pp. 249-257 ◽  
Author(s):  
Qiuli Liang ◽  
Gloria A. Benavides ◽  
Athanassios Vassilopoulos ◽  
David Gius ◽  
Victor Darley-Usmar ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Mitochondrial Respiration ◽  
Energy Demand ◽  
Mammalian Target Of Rapamycin ◽  
Protective Role ◽  
Nutrient Deprivation ◽  
Autophagy Flux ◽  
Jnk Pathway ◽  
Mouse Muscle

Sirt3 (sirtuin 3) is an NAD-dependent deacetylase localized to mitochondria. Sirt3 expression is increased in mouse muscle and liver by starvation, which could protect against the starvation-dependent increase in oxidative stress and protein damage. Damaged proteins and organelles depend on autophagy for removal and this is critical for cell survival, but the role of Sirt3 is unclear. To examine this, we used Sirt3-KO (knockout) mouse embryonic fibroblast cells, and found that, under basal conditions, Sirt3-KO cells exhibited increased autophagy flux compared with WT (wild-type) cells. In response to nutrient deprivation, both WT and KO cells exhibited increased basal and ATP-linked mitochondrial respiration, indicating an increased energy demand. Both cells exhibited lower levels of phosphorylated mTOR (mammalian target of rapamycin) and higher autophagy flux, with KO cells exhibiting lower maximal mitochondrial respiration and reserve capacity, and higher levels of autophagy than WT cells. KO cells exhibit higher phospho-JNK (c-Jun N-terminal kinase) and phospho-c-Jun than WT cells under starvation conditions. However, inhibition of JNK activity in Sirt3-KO cells did not affect LC3-I (light chain 3-I) and LC3-II levels, indicating that Sirt3-regulated autophagy is independent of the JNK pathway. Caspase 3 activation and cell death are significantly higher in Sirt3-KO cells compared with WT cells in response to nutrient deprivation. Inhibition of autophagy by chloroquine exacerbated cell death in both WT and Sirt3-KO cells, and by 3-methyadenine exacerbated cell death in Sirt3-KO cells. These data suggest that nutrient deprivation-induced autophagy plays a protective role in cell survival, and Sirt3 decreases the requirement for enhanced autophagy and improves cellular bioenergetics.

scholarly journals Autophagy: Friend or Foe in Breast Cancer Development, Progression, and Treatment

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Damian E. Berardi ◽  
Paola B. Campodónico ◽  
Maria Ines Díaz Bessone ◽  
Alejandro J. Urtreger ◽  
Laura B. Todaro
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Anticancer Agents ◽  
Cancer Development ◽  
Nutrient Deprivation ◽  
Clinical Settings ◽  
Degradative Pathway ◽  
Autophagy Induction ◽  
Autophagy Inhibition ◽  
Catabolic Process

Autophagy is a catabolic process responsible for the degradation and recycling of long-lived proteins and organelles by lysosomes. This degradative pathway sustains cell survival during nutrient deprivation, but in some circumstances, autophagy leads to cell death. Thereby, autophagy can serve as tumor suppressor, as the reduction in autophagic capacity causes malignant transformation and spontaneous tumors. On the other hand, this process also functions as a protective cell-survival mechanism against environmental stress causing resistance to antineoplastic therapies. Although autophagy inhibition, combined with anticancer agents, could be therapeutically beneficial in some cases, autophagy induction by itself could lead to cell death in some apoptosis-resistant cancers, indicating that autophagy induction may also be used as a therapy. This paper summarizes the most important findings described in the literature about autophagy and also discusses the importance of this process in clinical settings.

scholarly journals mTOR complex 1 signalling regulates the balance between lipid synthesis and oxidation in hypoxia lymphocytes

2017 ◽  
Vol 37 (1) ◽  
Author(s):  
Geng Yin ◽  
Yan Liang ◽  
Ying Wang ◽  
Yuan Yang ◽  
Min Yang ◽  
...  
Keyword(s):  
Cell Death ◽  
Mammalian Cells ◽  
Energy Demand ◽  
Metabolic Regulation ◽  
Mammalian Target Of Rapamycin ◽  
Lipid Synthesis ◽  
Vital Role ◽  
And Shifts ◽  
Mtor Complex 1 ◽  
Insight Into

Mammalian cells adapt to different environmental conditions and alter cellular metabolic pathways to meet the energy demand for survival. Thus, the metabolic regulation of cells under special conditions, such as hypoxia, should be precisely regulated. During the metabolic regulation, mammalian target of rapamycin (mTOR) plays a vital role in the sensing of extracellular stimulations and regulating intracellular adaptations. Here, we report that mTOR complex 1 (mTORC1) signalling is a central regulator of lipid homoeostasis in lymphocytes. In hypoxia, mTORC1 activity is reduced and shifts lipid synthesis to lipid oxidation. Moreover, knockdown tuberous sclerosis complex 1 (TSC1) constitutively activates mTORC1 activity and impairs the hypoxia-induced metabolic shift. Therefore, TSC1 knockdown enhances hypoxia-induced cell death. Re-inactivation of mTORC1 activity via rapamycin may resist hypoxia-induced cell death in TSC1 knockdown lymphocytes. Our findings provide a deep insight into mTORC1 in the metabolic balance of lipid synthesis and oxidation, and imply that mTORC1 activity should be precisely regulated for the lipid homoeostasis in lymphocytes.

scholarly journals Protective Role of Autophagy in Palmitate-Induced INS-1 β-Cell Death

Endocrinology ◽  
2008 ◽  
Vol 150 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Sung-E Choi ◽  
Sung-Mi Lee ◽  
Youn-Jung Lee ◽  
Ling-Ji Li ◽  
Soo-Jin Lee ◽  
...  
Keyword(s):  
Cell Death ◽  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Mammalian Target Of Rapamycin ◽  
Protective Role ◽  
Target Of Rapamycin ◽  
Β Cells ◽  
Β Cell ◽  
Green Fluorescent

Autophagy, a vacuolar degradative pathway, constitutes a stress adaptation that avoids cell death or elicits the alternative cell-death pathway. This study was undertaken to determine whether autophagy is activated in palmitate (PA)-treated β-cells and, if activated, what the role of autophagy is in the PA-induced β-cell death. The enhanced formation of autophagosomes and autolysosomes was observed by exposure of INS-1 β-cells to 400 μm PA in the presence of 25 mm glucose for 12 h. The formation of green fluorescent protein-LC3-labeled structures (green fluorescent protein-LC3 dots), with the conversion from LC3-I to LC3-II, was also distinct in the PA-treated cells. The phospho-mammalian target of rapamycin level, a typical signal pathway that inhibits activation of autophagy, was gradually decreased by PA treatment. Blockage of the mammalian target of rapamycin signaling pathway by treatment with rapamycin augmented the formation of autophagosomes but reduced PA-induced INS-1 cell death. In contrast, reduction of autophagosome formation by knocking down the ATG5, inhibition of fusion between autophagosome and lysosome by treatment with bafilomycin A1, or inhibition of proteolytic degradation by treatment with E64d/pepstatin A, significantly augmented PA-induced INS-1 cell death. These findings showed that the autophagy system could be activated in PA-treated INS-1 β-cells, and suggested that the induction of autophagy might play an adaptive and protective role in PA-induced cell death. Autophagy is activated in palmitate-treated insulinoma-1 beta cells, and the induction of autophagy plays a protective role in palmitate-induced beta cell death.

Programmed cell death and the control of cell survival

1994 ◽  
Vol 345 (1313) ◽  
pp. 265-268 ◽  
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Cell Survival ◽  
Mammalian Cell ◽  
Mitochondrial Respiration ◽  
Mammalian Cells ◽  
Normal Cell ◽  
Mammalian Development ◽  
Extracellular Signals

We draw the following tentative conclusions from our studies on programmed cell death (PCD): (i) the amount of normal cell death in mammalian development is still underestimated; (ii) most mammalian cells constitutively express the proteins required to undergo PCD ; (iii) the death programme operates by default when a mammalian cell is deprived of signals from other cells; (iv) many normal cell deaths may occur because cells fail to obtain the extracellular signals they need to suppress the death programme; and (v) neither the nucleus nor mitochondrial respiration is required for PCD (or Bcl-2 protection from PCD), raising the possibility that the death programme, like mitosis, is orchestrated by a cytosolic regulator that acts on multiple organelles in parallel.

scholarly journals Protective role of the deSUMOylating enzyme SENP3 in myocardial ischaemia-reperfusion injury

2019 ◽  
Author(s):  
Nadiia Rawlings ◽  
Laura Lee ◽  
Yasuko Nakamura ◽  
Kevin A. Wilkinson ◽  
Jeremy M Henley
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Protective Role ◽  
H9c2 Cell ◽  
Post Translational Modification ◽  
Ischaemia Reperfusion Injury ◽  
Ischaemia Reperfusion ◽  
Molecular Events ◽  
Promote Cell Survival ◽  
Whole Heart

AbstractInterruption of blood supply to the heart is a leading cause of death and disability. However, the molecular events that occur during heart ischaemia, and how these changes prime consequent cell death upon reperfusion, are poorly understood. Protein SUMOylation is a post-translational modification that has been strongly implicated in the protection of cells against a variety of stressors, including ischaemia-reperfusion. In particular, the SUMO2/3-specific protease SENP3 has emerged as an important determinant of cell survival after ischaemic infarct. Here, we used the Langendorff perfusion model to examine changes in the levels and localisation of SUMOylated target proteins and SENP3 in whole heart. We observed a 50% loss of SENP3 from the cytosolic fraction of hearts after preconditioning, a 90% loss after ischaemia and an 80% loss after ischaemia-reperfusion. To examine these effects further, we performed ischaemia and ischaemia-reperfusion experiments in the cardiomyocyte H9C2 cell line. Similar to whole hearts, ischaemia induced a decrease in cytosolic SENP3. Furthermore, shRNA-mediated knockdown of SENP3 led to an increase in the rate of cell death upon reperfusion. Together, our results indicate that cardiac ischaemia dramatically alter levels of SENP3 and suggest that this may a mechanism to promote cell survival after ischaemia-reperfusion in heart.

Combined inhibition of autophagy with mTOR inhibitor to enhance cell death in renal cell carcinoma.

2017 ◽  
Vol 35 (6_suppl) ◽  
pp. 450-450 ◽  
Author(s):  
Hua Chen ◽  
Kyle Potts ◽  
Allan Murray ◽  
Mary Hitt ◽  
Ron Moore
Keyword(s):  
Renal Cell Carcinoma ◽  
Cell Death ◽  
Cell Survival ◽  
Cell Carcinoma ◽  
Renal Cell ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Inhibitors ◽  
Pathological Process ◽  
Autophagic Flux ◽  
Independent Manner

450 Background: mTOR (mammalian target of rapamycin) and autophagy are increasingly recognized as being a central cellular and pathological process for numerous human diseases, including renal cell carcinoma (RCC). Depending on the cellular context, autophagy may promote cancer cell survival or cell death. However, little is known about the mechanisms of regulating mTOR activity and autophagic function in RCC. We hypothesize that autophagy promotes cell survival via mTOR mediated-phosphatidylinositol 3-kinase (PI3K)/AKT pathway and is regulated by the von Hippel-Lindau (VHL) tumor suppressor. Methods: RCC cells were stably lentiviral transduced with expression of VHL or mCherry-EGFP tandemfluorescent-tagged LC3B for studying autophagic flux. Cell viability was evaluated by cytotoxic XTT and clonogenic assays and flow cytometry. The efficacy of PI3K/AKT/mTOR pathway inhibition by RAD001, PI-103, MK2206, AZD8055, and/or lysosomotropic inhibitors were evaluated by immunoblots and immunofluorescence for autophagy process of autophagosome and lysosome. Results: We show that mTOR is hyperactive in VHL-deficient cells compared to cells with wild-type VHL or VHL-expressing cells. AZD8055-induced toxicity occurs in a VHL-independent manner via cell cycle arrest and clonogenic senescent cell death, but results in significantly increased expression of autophagic marker LC3-II and the formation of autophagic vacuoles. Pharmacologic inhibition or siRNA silencing of autophagy pathway components promotes AZD8055-induced cell death in VHL-deficient cells. Interestingly, defective autophagy marked by the presence of sustained p62 expression in VHL-deficient cells appears to contribute to cell survival via mTOR signaling, which in turn influences autophagosome-lysosome fusion, and thus controls autophagic flux by acting at the termination stage of the process. Conclusions: These results support mTOR and autophagy pathways as potential targets of anticancer drugs and reveal VHL in control of the autophagic program in RCC. Further, this work suggests that combined inhibition of autophagy along with mTOR inhibitors could be a novel therapeutic strategy for the treatment of RCC.

scholarly journals MK-2206, an AKT Inhibitor, Promotes Caspase-Independent Cell Death and Inhibits Leiomyoma Growth

Endocrinology ◽  
2013 ◽  
Vol 154 (11) ◽  
pp. 4046-4057 ◽  
Author(s):  
Elizabeth C. Sefton ◽  
Wenan Qiang ◽  
Vanida Serna ◽  
Takeshi Kurita ◽  
Jian-Jun Wei ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Viability ◽  
Cell Survival ◽  
Mammalian Target Of Rapamycin ◽  
The United States ◽  
Target Of Rapamycin ◽  
Benign Tumors ◽  
Molecular Evidence ◽  
Akt Inhibitor ◽  
Phase Ii Trials

Uterine leiomyomas (ULs), benign tumors of the myometrium, are the number one indication for hysterectomies in the United States due to a lack of an effective alternative therapy. ULs show activation of the pro-survival AKT pathway compared with normal myometrium; however, substantial data directly linking AKT to UL cell survival are lacking. We hypothesized that AKT promotes UL cell survival and that it is a viable target for inhibiting UL growth. We used the investigational AKT inhibitor MK-2206, currently in phase II trials, on cultured primary human UL and myometrial cells, immortalized leiomyoma cells, and in leiomyoma grafts grown under the kidney capsule in mice. MK-2206 inhibited AKT and PRAS40 phosphorylation but did not regulate serum- and glucocorticoid-induced kinase and ERK1/2, demonstrating its specificity for AKT. MK-2206 reduced UL cell viability and decreased UL tumor volumes. UL cells exhibited disruption of mitochondrial structures and underwent cell death that was independent of caspases. Additionally, mammalian target of rapamycin and p70S6K phosphorylation were reduced, indicating that mammalian target of rapamycin complex 1 signaling was compromised by AKT inhibition in UL cells. MK-2206 also induced autophagy in UL cells. Pretreatment of primary UL cells with 3-methyladenine enhanced MK-2206-mediated UL cell death, whereas knockdown of ATG5 and/or ATG7 did not significantly influence UL cell viability in the presence of MK-2206. Our data provide molecular evidence for the involvement of AKT in UL cell survival and suggest that AKT inhibition by MK-2206 may be a viable option to consider for the treatment of ULs.

Abstract P287: Therapeutic Hypothermia Cardioprotection During Cardiac Arrest Alters Reperfusion-Associated mTORC1 and AMPK Signaling

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Willard W Sharp ◽  
David Beiser ◽  
Zuo-Hui Shao ◽  
Mei Han ◽  
Chang-Qing Li ◽  
...  
Keyword(s):  
Cell Death ◽  
Cardiac Arrest ◽  
Cell Survival ◽  
Therapeutic Hypothermia ◽  
Ischemia Reperfusion ◽  
Mammalian Target Of Rapamycin ◽  
Energy Utilization ◽  
Mtor Inhibition ◽  
Ampk Signaling ◽  
Downstream Target

Introduction: Therapeutic hypothermia (TH) is highly cardioprotective in cellular and animal models of ischemia/reperfusion (I/R) and cardiac arrest and is dependent upon Akt. The mammalian target of rapamycin complex 1 (mTORC1) is a downstream target of Akt and an important regulator of cellular energy utilization and survival but its relationship to TH is not clear. We hypothesized that TH attenuates mTORC1 activation while simultaneously activating the cell survival kinases AMP activated protein kinase (AMPK) and Stat3. We further hypothesized that inhibitors of mTORC1 or activators of AMPK would replicate and/or enhance TH cardioprotection. Methods: Cardiomyocytes isolated from 1-2-day old C57BL6/J mice, were exposed to simulated I (90 min)/R (3 h). For TH, cells were cooled from 37C to 32C during ischemia and the first hour of reperfusion. Heart samples were also obtained from C57BL/6 mice that underwent an 8-min cardiac arrest. Following 6 min, the mice were randomized to normothermia (NT, 37C) or TH (30C) extended during CPR and for 1 h after resuscitation. Protein lysates were collected at serial time points for Western blot analyses. Results: Cardiomyocyte death during ischemia was minimal, but accelerated during reperfusion (4% vs. 46%,p<.05 n=5). TH attenuated this cell death (24% p<.05 n=5) and attenuated reperfusion-induced mTOR activation seen within 30 min as measured by differential phosphorylation of the mTOR targets 70S6K and eEF2. Compared to NT, TH-treated cardiomyocytes and hearts demonstrated increased p-AMPK after resuscitation, consistent with mTOR inhibition. Stat3 also showed enhanced phosphorylation on tyrosine 705. The mTOR inhibitor rapamycin (100nM) given during I/R similar to TH affected 70S6K and eEF2 and significantly reduced cell death (28% vs. 42%, p<.05 n=5). The AMPK activator metformin (100uM) also significantly reduced cell death (22%, p<.05 n=4). Conclusion: TH cardioprotection is associated with altered signaling events suggesting mTORC1 inhibition and activation of the cell survival kinases AMPK and Stat3. Pharmacologic strategies that mimic these TH effects are available and could be useful as TH adjuncts or mimetics that improve survival after cardiac arrest.

scholarly journals Transporter-Mediated Mitochondrial GSH Depletion Leading to Mitochondrial Dysfunction and Rescue with αB Crystallin Peptide in RPE Cells

Antioxidants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 411
Author(s):  
Parameswaran G Sreekumar ◽  
Mo Wang ◽  
Christine Spee ◽  
Srinivas R. Sadda ◽  
Ram Kannan
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Mitochondrial Function ◽  
Mitochondrial Respiration ◽  
Barrier Function ◽  
Mitochondrial Bioenergetics ◽  
Rpe Cells ◽  
Atp Production ◽  
Αb Crystallin ◽  
Mitochondrial Glutathione

Mitochondrial glutathione (mGSH) is critical for cell survival. We recently reported the localization of OGC (SLC25A11) and DIC (SLC25A10) in hRPE. Herein, we investigated the suppression of OGC and DIC and the effect of αB crystallin chaperone peptide co-treatment on RPE cell death and mitochondrial function. Non-polarized and polarized human RPE were co-treated for 24 h with phenyl succinic acid (PS, 5 mM) or butyl malonic acid (BM, 5 mM) with or without αB cry peptide (75 µg/mL). mGSH levels, mitochondrial bioenergetics, and ETC proteins were analyzed. The effect of mGSH depletion on cell death and barrier function was determined in polarized RPE co-treated with PS, OGC siRNA or BM and αB cry peptide. Inhibition of OGC and DIC resulted in a significant decrease in mGSH and increased apoptosis. mGSH depletion significantly decreased mitochondrial respiration, ATP production, and altered ETC protein expression. αB cry peptide restored mGSH, attenuated apoptosis, upregulated ETC proteins, and improved mitochondrial bioenergetics and biogenesis. mGSH transporters exhibited differential polarized localization: DIC (apical) and OGC (apical and basal). Inhibition of mGSH transport compromised barrier function which was partially restored by αB cry peptide. Our findings suggest mGSH augmentation by its transporters may be a valuable approach in AMD therapy.

Neuroglobin and Estrogen Receptors: A New Pathway of Cell Survival and Cell Death Balance

2015 ◽  
Vol 14 (2) ◽  
pp. 91-99 ◽  
Author(s):  
Maria T. Nuzzo ◽  
Marco Fiocchetti ◽  
Paolo Ascenzi ◽  
Maria Marino
Keyword(s):  
Cell Death ◽  
Estrogen Receptors ◽  
Cell Survival
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