Abstract P446: Sestrin2 Suppresses Age-related Hypertrophy by Inhibiting mTORC1 Signaling Pathway

Hypertension ◽  
2017 ◽  
Vol 70 (suppl_1) ◽  
Author(s):  
Nanhu Quan ◽  
Courtney Cates ◽  
Thomas Rousselle ◽  
Ji Li
Keyword(s):  
Ex Vivo ◽  
Energy State ◽  
Critical Role ◽  
Pressure Overload ◽  
Acid Oxidation ◽  
Protein Levels ◽  
Age Related ◽  
Mtorc1 Signaling ◽  
Mtorc1 Pathway ◽  
Mtorc1 Activation

Introduction: The mechanistic target of rapamycin complex 1 (mTORC1) plays a critical role in the regulation of cell growth and energy state. A novel stress-inducible protein, Sestrin2 was recognized as a sensor for mTORC1 pathway. Hypothesis: The cardiac mTORC1 activation modulated by Sestrin2 is impaired in aging that sensitizes heart to hypertrophy. Methods: C57BL/6J young WT (4-6 months) and aged WT mice (24-26 months), and young Sestrin2 knockout mice (4-6 months) were subjected to transverse aortic constriction (TAC) for pressure overload. The ex vivo working heart perfusion was used for measuring substrate metabolism. Results: The protein levels of cardiac Sestrin2 were decreased with aging. There are no phenotypic differences in young WT, aged WT and Sesn2 KO mice under normal physiology, while aged WT and Sesn2 KO versus young WT mice exhibit bigger hearts after 4 weeks of TAC surgery. The echocardiography showed an impaired cardiac function of aged WT and Sesn2 KO hearts by pressure overload. The pressure overload-induced phosphorylation of mTOR and mTORC1 downstream effectors 4E-BP1 and p70S6K were augmented in aged WT and Sesn2 KO versus young WT hearts. The swollen mitochondria with severely disrupted cristae and higher levels of redox markers pShc 66 and 4-hydroxynonenal were observed in aged WT and Sesn2 KO versus young WT hearts by pressure overload. The rate of glucose oxidation and fatty acid oxidation were impaired in the aged WT and Sesn2 KO versus young WT hearts by pressure overload. Intriguingly, pressure overload induced an interaction between Sestrin2 and GATOR2, a complex of unknown function that positively regulates mTORC1. Moreover, the binding affinity between Sestrin2 and GATOR2 is impaired in the aged WT hearts (p<0.05 vs. young WT). Furthermore, Adeno-associated virus 9 (AAV9)-Sestrin2 were delivered into the aged WT and Sesn2 KO hearts via a coronary delivery approach that rescued the protein levels of Sestrin2, attenuated mTORC1 activation and increased the tolerance of both aged WT and Sesn2 KO hearts to pressure overload. Conclusions: Cardiac Sestrin2 is a sensor for mTORC1 pathway in response to pressure overload. Sestrin2 deficiency in aging could be a reason for an increased sensitivity to hypertrophy in the elderly.

scholarly journals Increased Mitochondrial Calcium Uptake and Concomitant Hyperactivity by Presenilin Loss Promotes mTORC1 Signaling to Drive Neurodegeneration

2020 ◽  
Author(s):  
Kerry C. Ryan ◽  
Zahra Ashkavand ◽  
Shaarika Sarasija ◽  
Jocelyn T. Laboy ◽  
Rohan Samarakoon ◽  
...  
Keyword(s):  
Calcium Uptake ◽  
Critical Role ◽  
Mitochondrial Activity ◽  
Mitochondrial Morphology ◽  
Mitochondrial Calcium ◽  
Autophagic Flux ◽  
Age Related ◽  
Mtorc1 Signaling ◽  
Mtorc1 Pathway ◽  
Mitochondrial Calcium Uptake

Abstract BackgroundMetabolic dysfunction and protein aggregation are common characteristics that occur in age-related neurodegenerative disease, such as Alzheimer’s disease (AD). However, the mechanisms underlying these abnormalities remain poorly understood. Mutations in the presenilin genes are the primary cause of early onset familial AD, but despite their identification over 20 years ago, their role in the disease remains unclear. MethodsThe model system Caenorhabditis elegans was utilized to study the in vivo function of the highly conserved presenilin ortholog SEL-12 in the nervous system. Cell biological and biochemical assays were employed to monitor changes to proteostasis and autophagic flux in sel-12 mutants. Immunoblotting was used to assess alterations to the activity of the mTORC1 pathway, a central inhibitor of autophagy. Genetic and pharmaceutical strategies to reduce mTORC1 activity, and fluorescent reporters and biosensors were expressed in the mechanosensory neurons to measure mTORC1’s influence on proteotoxicity, neuronal health and mitochondrial morphology. Additionally, behavioral response to touch was employed to determine the role mTORC1 activity has in neuronal function in sel-12 mutants. RNA interference by standard feeding methods was used to assess the contribution of autophagy to mTORC1-mediated sel-12 defects. ResultsLoss of SEL-12 results in the hyperactivation of the mTORC1 pathway and mTORC1-dependent reduction in autophagy. This hyperactivation is caused by elevated mitochondrial calcium signaling and concomitant mitochondrial hyperactivity. Reducing mTORC1 activity improves proteostasis defects and neurodegenerative phenotypes associated with loss of SEL-12 function. Consistent with high mTORC1 activity, we find that SEL-12 loss reduces autophagy, and this reduction is prevented by limiting mitochondrial calcium uptake or mitochondrial respiration. Moreover, the improvements in proteostasis and neuronal defects in sel-12 mutants due to mTORC1 inhibition require the induction of autophagy.ConclusionSEL-12 has a critical role in mediating mitochondrial calcium homeostasis and activity. In the absence of presenilin function mitochondrial calcium uptake and mitochondrial activity is increased. This mitochondrial hyperactivity stimulates mTORC1 signaling, which inhibits autophagy and promotes proteostasis decline and neuronal dysfunction in sel-12 mutants. These data suggest that the mTORC1 pathway is a potential therapeutic target for treating AD.

scholarly journals Prostaglandin E2 activates the mTORC1 pathway through an EP4/cAMP/PKA- and EP1/Ca2+-mediated mechanism in the human pancreatic carcinoma cell line PANC-1

2015 ◽  
Vol 309 (10) ◽  
pp. C639-C649 ◽  
Author(s):  
Hui-Hua Chang ◽  
Steven H. Young ◽  
James Sinnett-Smith ◽  
Caroline Ei Ne Chou ◽  
Aune Moro ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Pancreatic Cancer ◽  
Prostaglandin E2 ◽  
Human Pancreatic Cancer ◽  
Pancreatic Carcinoma Cell Line ◽  
Pancreatic Cancer Cells ◽  
Mtorc1 Signaling ◽  
Mtorc1 Pathway ◽  
Pka Pathway ◽  
Mtorc1 Activation

Obesity, a known risk factor for pancreatic cancer, is associated with inflammation and insulin resistance. Proinflammatory prostaglandin E2 (PGE2) and elevated insulin-like growth factor type 1 (IGF-1), related to insulin resistance, are shown to play critical roles in pancreatic cancer progression. We aimed to explore a potential cross talk between PGE2 signaling and the IGF-1/Akt/mammalian target of rapamycin complex 1 (mTORC1) pathway in pancreatic cancer, which may be a key to unraveling the obesity-cancer link. In PANC-1 human pancreatic cancer cells, we showed that PGE2 stimulated mTORC1 activity independently of Akt, as evaluated by downstream signaling events. Subsequently, using pharmacological and genetic approaches, we demonstrated that PGE2-induced mTORC1 activation is mediated by the EP4/cAMP/PKA pathway, as well as an EP1/Ca2+-dependent pathway. The cooperative roles of the two pathways were supported by the maximal inhibition achieved with the combined pharmacological blockade, and the coexistence of highly expressed EP1 (mediating the Ca2+ response) and EP2 or EP4 (mediating the cAMP/PKA pathway) in PANC-1 cells and in the prostate cancer line PC-3, which also robustly exhibited PGE2-induced mTORC1 activation, as identified from a screen in various cancer cell lines. Importantly, we showed a reinforcing interaction between PGE2 and IGF-1 on mTORC1 signaling, with an increase in IL-23 production as a cellular outcome. Our data reveal a previously unrecognized mechanism of PGE2-stimulated mTORC1 activation mediated by EP4/cAMP/PKA and EP1/Ca2+ signaling, which may be of great importance in elucidating the promoting effects of obesity in pancreatic cancer. Ultimately, a precise understanding of these molecular links may provide novel targets for efficacious interventions devoid of adverse effects.

MTORC1-Regulated Metabolism Controlled by TSC2 Limits Cardiac Reperfusion Injury

2021 ◽  
Author(s):  
Christian U Oeing ◽  
Seungho Jun ◽  
Sumita Mishra ◽  
Brittany Dunkerly-Eyring ◽  
Anna Chen ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Ex Vivo ◽  
Heart Function ◽  
Acid Oxidation ◽  
Chain Acyl ◽  
Myocardial Substrate ◽  
Gain Loss ◽  
Whole Heart ◽  
Mtorc1 Activation

Rationale: The mechanistic target of rapamycin complex-1 (mTORC1) controls metabolism and protein homeostasis, and is activated following ischemic reperfusion (IR) injury and by ischemic preconditioning (IPC). However, studies vary as to whether this activation is beneficial or detrimental, and its influence on metabolism after IR is little studied. A limitation of prior investigations is their use of broad gain/loss of mTORC1 function, mostly applied prior to ischemic stress. This can be circumvented by regulating one serine (S1365) on tuberous sclerosis complex (TSC2) to achieve bi-directional mTORC1 modulation but only with TCS2-regulated co-stimulation. Objective: We tested the hypothesis that reduced TSC2 S1365 phosphorylation protects the myocardium against IR and IPC by amplifying mTORC1 activity to favor glycolytic metabolism. Methods and Results: Mice with either S1365A (TSC2 SA ; phospho-null) or S1365E (TSC2 SE ; phosphomimetic) knock-in mutations were studied ex vivo and in vivo. In response to IR, hearts from TSC2 SA mice had amplified mTORC1 activation and improved heart function compared to WT and TSC2 SE hearts. The magnitude of protection matched IPC. IPC requited less S1365 phosphorylation, as TSC2 SE hearts gained no benefit and failed to activate mTORC1 with IPC. IR metabolism was altered in TSC2 SA , with increased mitochondrial oxygen consumption rate and glycolytic capacity (stressed/maximal extracellular acidification) after myocyte hypoxia-reperfusion. In whole heart, lactate increased and long-chain acyl-carnitine levels declined during ischemia. The relative IR protection in TSC2 SA was lost by lowering glucose in the perfusate by 36%. Adding fatty acid (palmitate) compensated for reduced glucose in WT and TSC2 SE but not TSC2 SA which had the worst post-IR function under these conditions. Conclusions: TSC2-S1365 phosphorylation status regulates myocardial substrate utilization, and its decline activates mTORC1 biasing metabolism away from fatty acid oxidation to glycolysis to confer protection against IR. This pathway is also engaged and reduced TSC2 S1365 phosphorylation required for effective IPC.

scholarly journals Aging Influences the Metabolic and Inflammatory Phenotype in an Experimental Mouse Model of Acute Lung Injury

2020 ◽  
Author(s):  
Kevin W Gibbs ◽  
Chia-Chi Chuang Key ◽  
Lanazha Belfield ◽  
Jennifer Krall ◽  
Lina Purcell ◽  
...  
Keyword(s):  
Acute Lung Injury ◽  
Fatty Acid ◽  
Lung Injury ◽  
Whole Body ◽  
Acid Oxidation ◽  
Aged Mice ◽  
Protein Levels ◽  
Adult Mice ◽  
Age Related ◽  
Before And After

Abstract Increased age is a risk factor for poor outcomes from respiratory failure and acute respiratory distress syndrome (ARDS). In this study, we sought to define age-related differences in lung inflammation, muscle injury, and metabolism after intratracheal lipopolysaccharide (IT-LPS) acute lung injury (ALI) in adult (6 months) and aged (18–20 months) male C57BL/6 mice. We also investigated age-related changes in muscle fatty acid oxidation (FAO) and the consequences of systemic FAO inhibition with the drug etomoxir. Aged mice had a distinct lung injury course characterized by prolonged alveolar neutrophilia and lack of response to therapeutic exercise. To assess the metabolic consequences of ALI, aged and adult mice underwent whole body metabolic phenotyping before and after IT-LPS. Aged mice had prolonged anorexia and decreased respiratory exchange ratio, indicating increased reliance on FAO. Etomoxir increased mortality in aged but not adult ALI mice, confirming the importance of FAO on survival from acute severe stress and suggesting that adult mice have increased resilience to FAO inhibition. Skeletal muscles from aged ALI mice had increased transcription of key fatty acid metabolizing enzymes, CPT-1b, LCAD, MCAD, FATP1 and UCP3. Additionally, aged mice had increased protein levels of CPT-1b at baseline and after lung injury. Surprisingly, CPT-1b in isolated skeletal muscle mitochondria had decreased activity in aged mice compared to adults. The distinct phenotype of aged ALI mice has similar characteristics to the adverse age-related outcomes of ARDS. This model may be useful to examine and augment immunologic and metabolic abnormalities unique to the critically ill aged population.

scholarly journals IL-2– and IL-15–induced activation of the rapamycin-sensitive mTORC1 pathway in malignant CD4+ T lymphocytes

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 2181-2189 ◽  
Author(s):  
Michal Marzec ◽  
Xiaobin Liu ◽  
Monika Kasprzycka ◽  
Agnieszka Witkiewicz ◽  
Puthiyaveettil N. Raghunath ◽  
...  
Keyword(s):  
T Cell ◽  
Cell Lines ◽  
Cell Transformation ◽  
Single Agent ◽  
Large Cell ◽  
Dependent Manner ◽  
T Cell Lymphomas ◽  
Mtorc1 Signaling ◽  
Mtorc1 Pathway ◽  
Mtorc1 Activation

We examined functional status, activation mechanisms, and biologic role of the mTORC1 signaling pathway in malignant CD4+ T cells derived from the cutaneous T-cell lymphoma (CTCL). Whereas the spontaneously growing CTCL-derived cell lines displayed persistent activation of the TORC1 as well as the PI3K/Akt and MEK/ERK pathways, the IL-2–dependent cell lines activated the pathways in response to IL-2 and IL-15 but not IL-21. Activation of mTORC1 and MEK/ERK was nutrient dependent. The mTORC1, PI3K/Akt, and MEK/ERK pathways could also be activated by IL-2 in the primary leukemic, mitogen-preactivated CTCL cells. mTORC1 activation was also detected in the CTCL tissues in the lymphoma stage–dependent manner with the highest percentage of positive cells present in the cases with a large cell transformation. Rapamycin inhibited mTORC1 signaling and suppressed CTCL cell proliferation but showed little effect on their apoptotic rate when used as a single agent. Activation of the mTORC1, PI3K/Akt, and MEK/ERK pathways was strictly dependent on the Jak3 and Jak1 kinases. Finally, mTORC1 activation was transduced preferentially through the PI3K/Akt pathway. These findings document the selective γc-signaling cytokine-mediated activation of the mTORC1 pathway in the CTCL cells and suggest that the pathway represents a therapeutic target in CTCL and, possibly, other T-cell lymphomas.

scholarly journals METABOLIC FLEXIBILITY IN CLASSICAL MONOCYTES IS NOT AFFECTED BY AGE

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S105-S105
Author(s):  
Johnathan Yarbro ◽  
Brandt Pence
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Immune Cell ◽  
Ex Vivo ◽  
Inflammatory Cells ◽  
Acid Oxidation ◽  
Low Grade ◽  
Glucose Starvation ◽  
Cell Functions ◽  
Age Related

Abstract Inflammaging is the chronic low-grade inflammation that occurs with age that contributes to the pathology of age-related diseases. Monocytes are innate immune cells that become dysregulated with age and which can contribute to inflammaging. Metabolism plays a key role in determining immune cell functions, with anti-inflammatory cells primarily relying on fatty acid oxidation and pro-inflammatory cells primarily relying on glycolysis. It was recently shown that lipopolysaccharide (LPS)-stimulated monocytes can compensate for a lack of glucose by utilizing fatty acid oxidation. Given that mitochondrial function decreases with age, we hypothesized that monocytes taken from aged individuals would have an impaired ability to upregulate oxidative metabolism and would have impaired effector functions. Aging did not impair LPS-induced oxygen consumption rate during glucose starvation as measured on a Seahorse XFp system. Additionally, aged monocytes maintained inflammatory gene expression responses and phagocytic capacity during LPS stimulation in the absence of glucose. In conclusion, aged monocytes maintain effector and metabolic functions during glucose starvation, at least in an ex vivo context.

scholarly journals Gαq activation modulates autophagy by promoting mTORC1 signaling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sofía Cabezudo ◽  
Maria Sanz-Flores ◽  
Alvaro Caballero ◽  
Inmaculada Tasset ◽  
Elena Rebollo ◽  
...  
Keyword(s):  
Nutrient Status ◽  
Autophagy Induction ◽  
Pathway Activation ◽  
Mtorc1 Signaling ◽  
Different Types ◽  
Mtorc1 Pathway ◽  
Mtorc1 Activation ◽  
G Protein Coupled ◽  
Activation Status

AbstractThe mTORC1 node plays a major role in autophagy modulation. We report a role of the ubiquitous Gαq subunit, a known transducer of plasma membrane G protein-coupled receptors signaling, as a core modulator of mTORC1 and autophagy. Cells lacking Gαq/11 display higher basal autophagy, enhanced autophagy induction upon different types of nutrient stress along with a decreased mTORC1 activation status. They are also unable to reactivate mTORC1 and thus inactivate ongoing autophagy upon nutrient recovery. Conversely, stimulation of Gαq/11 promotes sustained mTORC1 pathway activation and reversion of autophagy promoted by serum or amino acids removal. Gαq is present in autophagic compartments and lysosomes and is part of the mTORC1 multi-molecular complex, contributing to its assembly and activation via its nutrient status-sensitive interaction with p62, which displays features of a Gαq effector. Gαq emerges as a central regulator of the autophagy machinery required to maintain cellular homeostasis upon nutrient fluctuations.

β2-Agonist administration increases sarcoplasmic reticulum Ca2+-ATPase activity in aged rat skeletal muscle

2005 ◽  
Vol 288 (3) ◽  
pp. E526-E533 ◽  
Author(s):  
Jonathan D. Schertzer ◽  
David R. Plant ◽  
James G. Ryall ◽  
Felice Beitzel ◽  
Nicole Stupka ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Time Course ◽  
Fiber Type ◽  
Critical Role ◽  
Maximal Activity ◽  
Contractile Properties ◽  
Kinetic Properties ◽  
Protein Levels ◽  
Age Related

Aging is associated with a slowing of skeletal muscle contractile properties, including a decreased rate of relaxation. In rats, the age-related decrease in the maximal rate of relaxation is reversed after 4-wk administration with the β2-adrenoceptor agonist (β2-agonist) fenoterol. Given the critical role of the sarcoplasmic reticulum (SR) in regulating intracellular Ca2+ transients and ultimately the time course of muscle contraction and relaxation, we tested the hypothesis that the mechanisms of action of fenoterol are mediated by alterations in SR proteins. Sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) kinetic properties were assessed in muscle homogenates and enriched SR membranes isolated from the red (RG) and white (WG) portions of the gastrocnemius muscle in adult (16 mo) and aged (28 mo) F344 rats that had been administered fenoterol for 4 wk (1.4 mg/kg/day ip, in saline) or vehicle only. Aging was associated with a 29% decrease in the maximal activity ( Vmax) of SERCA in the RG but not in the WG muscles. Fenoterol treatment increased the Vmax of SERCA and SERCA1 protein levels in RG and WG. In the RG, fenoterol administration reversed an age-related selective nitration of the SERCA2a isoform. Our findings demonstrate that the mechanisms underlying age-related changes in contractile properties are fiber type dependent, whereas the effects of fenoterol administration are independent of age and fiber type.

scholarly journals mTORC1 signaling suppresses Wnt/β-catenin signaling through DVL-dependent regulation of Wnt receptor FZD level

2018 ◽  
Vol 115 (44) ◽  
pp. E10362-E10369 ◽  
Author(s):  
Hao Zeng ◽  
Bo Lu ◽  
Raffaella Zamponi ◽  
Zinger Yang ◽  
Kristie Wetzel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Ex Vivo ◽  
Tissue Homeostasis ◽  
Dependent Manner ◽  
Cell Functions ◽  
A Genome ◽  
Mtorc1 Signaling ◽  
Mtorc1 Activation

Wnt/β-catenin signaling plays pivotal roles in cell proliferation and tissue homeostasis by maintaining somatic stem cell functions. The mammalian target of rapamycin (mTOR) signaling functions as an integrative rheostat that orchestrates various cellular and metabolic activities that shape tissue homeostasis. Whether these two fundamental signaling pathways couple to exert physiological functions still remains mysterious. Using a genome-wide CRISPR-Cas9 screening, we discover that mTOR complex 1 (mTORC1) signaling suppresses canonical Wnt/β-catenin signaling. Deficiency in tuberous sclerosis complex 1/2 (TSC1/2), core negative regulators of mTORC1 activity, represses Wnt/β-catenin target gene expression, which can be rescued by RAD001. Mechanistically, mTORC1 signaling regulates the cell surface level of Wnt receptor Frizzled (FZD) in a Dishevelled (DVL)-dependent manner by influencing the association of DVL and clathrin AP-2 adaptor. Sustained mTORC1 activation impairs Wnt/β-catenin signaling and causes loss of stemness in intestinal organoids ex vivo and primitive intestinal progenitors in vivo. Wnt/β-catenin–dependent liver metabolic zonation gene expression program is also down-regulated by mTORC1 activation. Our study provides a paradigm that mTORC1 signaling cell autonomously regulates Wnt/β-catenin pathway to influence stem cell maintenance.

scholarly journals mTORC1-Activated Monocytes Increase Tregs and Inhibit the Immune Response to Bacterial Infections

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Lijun Fang ◽  
Huaijun Tu ◽  
Wei Guo ◽  
Shixuan Wang ◽  
Ting Xue ◽  
...  
Keyword(s):  
Immune Response ◽  
Bacterial Infections ◽  
Immune Cell ◽  
Critical Role ◽  
Innate Immune ◽  
E Coli ◽  
Upstream Regulator ◽  
Mtorc1 Signaling ◽  
Activated Monocytes ◽  
Mtorc1 Activation

The TSC1/2 heterodimer, a key upstream regulator of the mTOR, can inhibit the activation of mTOR, which plays a critical role in immune responses after bacterial infections. Monocytes are an innate immune cell type that have been shown to be involved in bacteremia. However, how the mTOR pathway is involved in the regulation of monocytes is largely unknown. In our study, TSC1 KO mice and WT mice were infected withE. coli. When compared to WT mice, we found higher mortality, greater numbers of bacteria, decreased expression of coactivators in monocytes, increased numbers of Tregs, and decreased numbers of effector T cells in TSC1 KO mice. Monocytes obtained from TSC1 KO mice produced more ROS, IL-6, IL-10, and TGF-βand less IL-1, IFN-γ, and TNF-α. Taken together, our results suggest that the inhibited immune functioning in TSC1 KO mice is influenced by mTORC1 activation in monocytes. The reduced expression of coactivators resulted in inhibited effector T cell proliferation. mTORC1-activated monocytes are harmful during bacterial infections. Therefore, inhibiting mTORC1 signaling through rapamycin administration could rescue the harmful aspects of an overactive immune response, and this knowledge provides a new direction for clinical therapy.

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