microRNA-378 promotes autophagy and inhibits apoptosis in skeletal muscle

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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Leucine modulates contraction- and insulin-stimulated glucose transport and upstream signaling events in rat skeletal muscle

Journal of Applied Physiology ◽

10.1152/japplphysiol.00420.2009 ◽

2010 ◽

Vol 108 (2) ◽

pp. 274-282 ◽

Cited By ~ 30

Author(s):

Nobumasa Iwanaka ◽

Tatsuro Egawa ◽

Nozomi Satoubu ◽

Kouhei Karaike ◽

Xiao Ma ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Glucose Transport ◽

Mammalian Target Of Rapamycin ◽

Α Subunit ◽

Ampk Phosphorylation ◽

Dependent Protein ◽

Opposing Effects ◽

Amp Activated Protein Kinase

Leucine has profound effects on glucose metabolism in muscle; however, the effects of leucine on glucose transport in muscle have not been well documented. We investigated the effects of leucine on contraction- and insulin-stimulated glucose transport in isolated rat epitrochlearis muscle in vitro. In the absence of insulin, tetanic contraction increased 3- O-methyl-d-glucose (3-MG) transport and Thr172 phosphorylation of the catalytic α-subunit of 5′-AMP-activated protein kinase (AMPK), a signaling intermediary leading to insulin-independent glucose transport. Leucine (2 mM, 30 min) significantly enhanced contraction-stimulated 3-MG transport and AMPK phosphorylation, accompanied by increased phosphorylation of p70 S6 kinase (p70S6K) Thr389. The stimulatory effects of leucine on 3-MG transport and AMPK phosphorylation were canceled by STO-609 blockade of Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) or rapamycin blockade of p70S6K. On the other hand, leucine blunted insulin-stimulated 3-MG transport and reduced insulin-stimulated Akt Thr473 phosphorylation. Leucine increased insulin-stimulated p70S6K Thr389 phosphorylation and enhanced the inhibitory phosphorylation of the insulin receptor substrate 1 (IRS1) Ser636/639. Furthermore, the effects of leucine on insulin-stimulated 3-MG transport and IRS phosphorylation were abolished by rapamycin. These results indicate that leucine activates contraction-stimulated glucose transport and inhibits insulin-stimulated glucose transport in skeletal muscle by activating mammalian target of rapamycin (mTOR)/p70S6K signaling. Enhanced increases in contraction-stimulated AMPK Thr172 phosphorylation and insulin-stimulated IRS1 Ser636/639 phosphorylation might be responsible for these opposing effects of leucine, respectively.

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Sestrins at the Interface of ROS Control and Autophagy Regulation in Health and Disease

Oxidative Medicine and Cellular Longevity ◽

10.1155/2019/1283075 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 16

Author(s):

Marco Cordani ◽

Miguel Sánchez-Álvarez ◽

Raffaele Strippoli ◽

Alexandr V. Bazhin ◽

Massimo Donadelli

Keyword(s):

Metabolic Disorders ◽

Mammalian Target Of Rapamycin ◽

Therapeutic Targets ◽

Metabolic Stress ◽

Dependent Protein Kinase ◽

Energy Sensor ◽

Positive Regulators ◽

Dependent Protein ◽

Health And Disease ◽

Broad Interest

Reactive oxygen species (ROS) and autophagy are two highly complex and interrelated components of cell physiopathology, but our understanding of their integration and their contribution to cell homeostasis and disease is still limited. Sestrins (SESNs) belong to a family of highly conserved stress-inducible proteins that orchestrate antioxidant and autophagy-regulating functions protecting cells from various noxious stimuli, including DNA damage, oxidative stress, hypoxia, and metabolic stress. They are also relevant modulators of metabolism as positive regulators of the key energy sensor AMP-dependent protein kinase (AMPK) and inhibitors of mammalian target of rapamycin complex 1 (mTORC1). Since perturbations in these pathways are central to multiple disorders, SESNs might constitute potential novel therapeutic targets of broad interest. In this review, we discuss the current understanding of regulatory and effector networks of SESNs, highlighting their significance as potential biomarkers and therapeutic targets for different diseases, such as aging-related diseases, metabolic disorders, neurodegenerative diseases, and cancer.

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Hydrogel-based bioassay sheets for in vitro evaluation of contraction-dependent metabolic regulation in skeletal muscle cells

Biomaterials Science ◽

10.1039/c3bm60179j ◽

2014 ◽

Vol 2 (2) ◽

pp. 252-256 ◽

Cited By ~ 6

Author(s):

Kuniaki Nagamine ◽

Kohei Okamoto ◽

Shingo Otani ◽

Hirokazu Kaji ◽

Makoto Kanzaki ◽

...

Keyword(s):

Skeletal Muscle ◽

Metabolic Regulation ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

In Vitro Evaluation

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Deadly decisions: the role of genes regulating programmed cell death in human preimplantation embryo development

Reproduction ◽

10.1530/rep.1.00241 ◽

2004 ◽

Vol 128 (3) ◽

pp. 281-291 ◽

Cited By ~ 78

Author(s):

Andrea Jurisicova ◽

Beth M Acton

Keyword(s):

Gene Expression ◽

Cell Death ◽

Cell Fate ◽

Embryo Development ◽

Preimplantation Embryo ◽

Culture Media ◽

Culture Conditions ◽

Early Embryo ◽

Preimplantation Embryo Development

Human preimplantation embryo development is prone to high rates of early embryo wastage, particularly under currentin vitroculture conditions. There are many possible underlying causes for embryo demise, including DNA damage, poor embryo metabolism and the effect of suboptimal culture media, all of which could result in an imbalance in gene expression and the failed execution of basic embryonic decisions. In view of the complex interactions involved in embryo development, a thorough understanding of these parameters is essential to improving embryo quality. An increasing body of evidence indicates that cell fate (i.e. survival/differentiation or death) is determined by the outcome of specific intracellular interactions between pro- and anti-apoptotic proteins, many of which are expressed during oocyte and preimplantation embryo development. The recent availability of mutant mice lacking expression of various genes involved in the regulation of cell survival has enabled rapid progress towards identifying those molecules that are functionally important for normal oocyte and preimplantation embryo development. In this review we will discuss the current understanding of the regulation of cell death gene expression during preimplantation embryo development, with a focus on human embryology and a discussion of animal models where appropriate.

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ARHGEF3 regulates skeletal muscle regeneration and strength through autophagy

10.1101/2020.02.28.970756 ◽

2020 ◽

Author(s):

Jae-Sung You ◽

Nilmani Singh ◽

Adriana Reyes-Ordonez ◽

Nidhi Khanna ◽

Zehua Bao ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Regeneration ◽

Mammalian Target Of Rapamycin ◽

Akt Signaling ◽

Skeletal Muscle Regeneration ◽

Myoblast Differentiation ◽

Independent Manner ◽

And Function ◽

Old Mice

SummarySkeletal muscle regeneration is essential for restoring muscle function upon injury and for the maintenance of muscle health with aging. ARHGEF3, a Rho-specific GEF, negatively regulates myoblast differentiation via mammalian target of rapamycin complex 2 (mTORC2)-Akt signaling in a GEF-independent manner in vitro. Here, we investigated ARHGEF3’s role in skeletal muscle regeneration by creating ARHGEF3 KO mice. These mice exhibited no discernible phenotype under normal conditions. Upon injury, however, ARHGEF3 deficiency enhanced the mass, fiber size and function of regenerating muscles in both young and aged mice. Surprisingly, these effects were not mediated by mTORC2-Akt signaling, but by the GEF activity of ARHGEF3. Furthermore, ARHGEF3 KO promoted muscle regeneration through activation of autophagy, a process that is also critical for maintaining muscle strength. Accordingly, in old mice, ARHGEF3 depletion prevented muscle weakness by restoring autophagy flux. Collectively, our findings identify an unexpected link between ARHGEF3 and autophagy-related muscle pathophysiology.

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cAMP-Dependent Activation of Mammalian Target of Rapamycin (mTOR) in Thyroid Cells. Implication in Mitogenesis and Activation of CDK4

Molecular Endocrinology ◽

10.1210/me.2010-0087 ◽

2010 ◽

Vol 24 (7) ◽

pp. 1453-1468 ◽

Cited By ~ 43

Author(s):

Sara Blancquaert ◽

Lifu Wang ◽

Sabine Paternot ◽

Katia Coulonval ◽

Jacques E. Dumont ◽

...

Keyword(s):

Protein Kinase ◽

Glycogen Synthase ◽

Mammalian Target Of Rapamycin ◽

Cyclin D3 ◽

Target Of Rapamycin ◽

Thyroid Cells ◽

Dependent Protein ◽

Rat Thyroid ◽

Amp Activated Protein Kinase

Abstract How cAMP-dependent protein kinases [protein kinase A (PKA)] transduce the mitogenic stimulus elicited by TSH in thyroid cells to late activation of cyclin D3-cyclin-dependent kinase 4 (CDK4) remains enigmatic. Here we show in PC Cl3 rat thyroid cells that TSH/cAMP, like insulin, activates the mammalian target of rapamycin (mTOR)-raptor complex (mTORC1) leading to phosphorylation of S6K1 and 4E-BP1. mTORC1-dependent S6K1 phosphorylation in response to both insulin and cAMP required amino acids, whereas inhibition of AMP-activated protein kinase and glycogen synthase kinase 3 enhanced insulin but not cAMP effects. Unlike insulin, TSH/cAMP did not activate protein kinase B or induce tuberous sclerosis complex 2 phosphorylation at T1462 and Y1571. However, like insulin, TSH/cAMP produced a stable increase in mTORC1 kinase activity that was associated with augmented 4E-BP1 binding to raptor. This could be caused in part by T246 phosphorylation of PRAS40, which was found as an in vitro substrate of PKA. Both in PC Cl3 cells and primary dog thyrocytes, rapamycin inhibited DNA synthesis and retinoblastoma protein phosphorylation induced by TSH and insulin. Although rapamycin reduced cyclin D3 accumulation, the abundance of cyclin D3-CDK4 complexes was not affected. However, rapamycin inhibited the activity of these complexes by decreasing the TSH and insulin-mediated stimulation of activating T172 phosphorylation of CDK4. We propose that mTORC1 activation by TSH, at least in part through PKA-dependent phosphorylation of PRAS40, crucially contributes to mediate cAMP-dependent mitogenesis by regulating CDK4 T172-phosphorylation.

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Cell fate determined by the activation balance between PKR and SPHK1

Cell Death and Differentiation ◽

10.1038/s41418-020-00608-8 ◽

2020 ◽

Vol 28 (1) ◽

pp. 401-418

Author(s):

Han Qiao ◽

Tianqing Jiang ◽

Peiqiang Mu ◽

Xiaoxuan Chen ◽

Xianhui Wen ◽

...

Keyword(s):

Cell Death ◽

Cell Fate ◽

Cellular Response ◽

Cellular Stress Response ◽

Protein Kinase R ◽

Survival Pathways ◽

Stress Signal ◽

Dependent Protein ◽

Response To Stress ◽

Simultaneous Activation

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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The effect of recombinant caspase 3 on porcine myofibrillar proteins

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200020159 ◽

2007 ◽

Vol 2007 ◽

pp. 112-112

Author(s):

CM. Kemp ◽

T. Parr

Keyword(s):

Skeletal Muscle ◽

Cell Death ◽

Preliminary Data ◽

Shear Force ◽

Caspase 3 ◽

Proteolytic Enzymes ◽

Myofibrillar Proteins ◽

Caspase Activity ◽

Conditioning Period

Meat tenderisation results from the weakening of the myofibrillar structures and has been attributed to endogenous proteolytic enzymes. It has been proposed that tenderization is a mulitenzymatic system and the process of slaughter and exsanguination would engage muscle cells in a form of cell death (Ouali et al., 2006). Caspases are primarily associated with apoptosis and once activated they target and cleave a number of substrates including components of the Z-disk and costameres. Recent studies have shown that caspases are active in skeletal muscle during the postmortem conditioning period and our preliminary data indicates that there is a relationship between caspase activity and shear force (Kemp et al., 2006). The aim of this study was to investigate whether recombinant caspase 3 was capable of porcine degrading myofibrillar proteins in vitro.

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

Bioscience Reports ◽

10.1042/bsr20160479 ◽

2017 ◽

Vol 37 (1) ◽

Cited By ~ 4

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.

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Forskolin attenuates the action of insulin on the Akt–mTOR pathway in human skeletal muscle

Applied Physiology Nutrition and Metabolism ◽

10.1139/h09-096 ◽

2009 ◽

Vol 34 (5) ◽

pp. 916-925 ◽

Cited By ~ 1

Author(s):

Scott R. Richmond ◽

Chad D. Touchberry ◽

Philip M. Gallagher

Keyword(s):

Skeletal Muscle ◽

Intracellular Signaling ◽

Human Skeletal Muscle ◽

Vastus Lateralis ◽

Mammalian Target Of Rapamycin ◽

Mtor Pathway ◽

Akt Phosphorylation ◽

Phosphorylated Akt ◽

Mtor Phosphorylation

Forskolin (FSK) is capable of both stimulating and inhibiting the intracellular signaling pathways of protein synthesis tissues other than skeletal muscle. The purpose of this investigation was to determine if FSK administration affects various elements of the protein kinase B (Akt)–mammalian target of rapamycin (mTOR) pathway in human skeletal muscle. Ten (n = 10) healthy, young (21.6 ± 1.3 years), nonobese (body mass index = 25.5 ± 3.5 kg·m–2), recreationally active males were selected for participation. Following an 8 h fast, 2 muscle biopsies of the vastus lateralis were performed. The samples were sectioned and exposed to 4 in vitro treatment conditions: basal, FSK, insulin (INS), and FSK+INS. The samples were then analyzed for total and phosphorylated levels of Akt, mTOR, S6 kinase (S6K1), and 4E binding protein (4EBP1). Akt phosphorylation was significantly greater in the INS-treated samples compared with the basal and FSK conditions (p = 0.007). Furthermore, the ratio of phosphorylated Akt to total Akt (P/T) was higher in the INS samples compared with the basal and FSK samples (p = 0.001). There were no differences in mTOR phosphorylation among the 4 groups; however, total mTOR was significantly greater in the FSK+INS group (p = 0.006). There were also no differences in phosphorylated or total levels of S6K1 among the 4 groups. However, 4EBP1 phosphorylation was significantly greater in the INS-treated samples compared with the basal (p = 0.003) and FSK (p = 0.004) treatments. There were no differences in the ratio of phosphorylated 4EBP1 to total 4EBP1 (P/T) among the 4 groups. These results indicate that FSK does not activate the Akt–mTOR pathway in human skeletal muscle; however, these results suggest that FSK may inhibit the actions of INS on this pathway.

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