1
|
Dupont N, Claude-Taupin A, Codogno P. A historical perspective of macroautophagy regulation by biochemical and biomechanical stimuli. FEBS Lett 2024; 598:17-31. [PMID: 37777819 DOI: 10.1002/1873-3468.14744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 09/08/2023] [Accepted: 09/11/2023] [Indexed: 10/02/2023]
Abstract
Macroautophagy is a lysosomal degradative pathway for intracellular macromolecules, protein aggregates, and organelles. The formation of the autophagosome, a double membrane-bound structure that sequesters cargoes before their delivery to the lysosome, is regulated by several stimuli in multicellular organisms. Pioneering studies in rat liver showed the importance of amino acids, insulin, and glucagon in controlling macroautophagy. Thereafter, many studies have deciphered the signaling pathways downstream of these biochemical stimuli to control autophagosome formation. Two signaling hubs have emerged: the kinase mTOR, in a complex at the surface of lysosomes which is sensitive to nutrients and hormones; and AMPK, which is sensitive to the cellular energetic status. Besides nutritional, hormonal, and energetic fluctuations, many organs have to respond to mechanical forces (compression, stretching, and shear stress). Recent studies have shown the importance of mechanotransduction in controlling macroautophagy. This regulation engages cell surface sensors, such as the primary cilium, in order to translate mechanical stimuli into biological responses.
Collapse
Affiliation(s)
- Nicolas Dupont
- INSERM UMR-S1151, CNRS UMR-S8253, Institut Necker-Enfants Malades, Université Paris Cité, France
| | - Aurore Claude-Taupin
- INSERM UMR-S1151, CNRS UMR-S8253, Institut Necker-Enfants Malades, Université Paris Cité, France
| | - Patrice Codogno
- INSERM UMR-S1151, CNRS UMR-S8253, Institut Necker-Enfants Malades, Université Paris Cité, France
| |
Collapse
|
2
|
An alcoholic extract of Thuja orientalis L. leaves inhibits autophagy by specifically targeting pro-autophagy PIK3C3/VPS34 complex. Sci Rep 2021; 11:17712. [PMID: 34489486 PMCID: PMC8421415 DOI: 10.1038/s41598-021-97216-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 08/18/2021] [Indexed: 12/13/2022] Open
Abstract
Autophagy is a lysosome-dependent degradation program to maintain cellular homeostasis in response to a variety of stressful conditions, such as long-lived or non-functional subcellular organelles, protein aggregates, nutrient limitation, and virus/bacteria infection. Accordingly, dysregulation of autophagy is closely associated with many human pathophysiological conditions, such as neurodegenerative diseases, aging, and cancer, and autophagy is highlighted as an important therapeutic target for these human diseases. In autophagy process, PIK3C3/VPS34 complex plays important roles in autophagosome biogenesis. Accumulating evidences that inhibition of PIK3C3/VPS34 complex successfully blocks autophagy make the complex as an attractive target for the development of autophagy-specific inhibitors. However, considering that various forms of PIK3C3/VPS34 complex exist and they are involved in many different cellular functions, the targeting of the pro-autophagy PIK3C3/VPS34 complex is required to specifically inhibit autophagy. To identify autophagy inhibitors targeting the pro-autophagy complex, we have performed the screening of a customized natural product library consisting of 35 herbal extracts which are widely used in the oriental medicine as anti-inflammation and/or anti-tumor reagents. We discovered that an alcoholic extract of Thuja orientalis L. leaves inhibits pro-autophagy complex formation by disrupting the interaction between autophagy-specific factor, ATG14L, and the complex core unit Vps34-Beclin 1 in vitro. Also, it inhibits the nutrient starvation induced autophagy and diminished pro-autophagy PIK3C3/VPS34 complex containing either ATG14L or UVRAG in several cell lines. Our results strongly suggest that Thuja orientalis L. leave extract functions as an autophagy-specific inhibitor not decreasing the complex activity nor the protein level, but preventing protein-protein interaction between autophagy-specific factor (ATG14L and UVRAG) and PIK3C3/VPS34 complex core unit, Vps34-Beclin 1, thereby specifically depleting the pro-autophagy complex to inhibit autophagy.
Collapse
|
3
|
Lee JH, Lin SY, Liu JW, Lin SZ, Harn HJ, Chiou TW. n-Butylidenephthalide Modulates Autophagy to Ameliorate Neuropathological Progress of Spinocerebellar Ataxia Type 3 through mTOR Pathway. Int J Mol Sci 2021; 22:6339. [PMID: 34199295 PMCID: PMC8231882 DOI: 10.3390/ijms22126339] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 02/07/2023] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3), a hereditary and lethal neurodegenerative disease, is attributed to the abnormal accumulation of undegradable polyglutamine (polyQ), which is encoded by mutated ataxin-3 gene (ATXN3). The toxic fragments processed from mutant ATXN3 can induce neuronal death, leading to the muscular incoordination of the human body. Some treatment strategies of SCA3 are preferentially focused on depleting the abnormal aggregates, which led to the discovery of small molecule n-butylidenephthalide (n-BP). n-BP-promoted autophagy protected the loss of Purkinje cell in the cerebellum that regulates the network associated with motor functions. We report that the n-BP treatment may be effective in treating SCA3 disease. n-BP treatment led to the depletion of mutant ATXN3 with the expanded polyQ chain and the toxic fragments resulting in increased metabolic activity and alleviated atrophy of SCA3 murine cerebellum. Furthermore, n-BP treated animal and HEK-293GFP-ATXN3-84Q cell models could consistently show the depletion of aggregates through mTOR inhibition. With its unique mechanism, the two autophagic inhibitors Bafilomycin A1 and wortmannin could halt the n-BP-induced elimination of aggregates. Collectively, n-BP shows promising results for the treatment of SCA3.
Collapse
Affiliation(s)
- Jui-Hao Lee
- Everfront Biotech Inc., New Taipei City 22180, Taiwan; (J.-H.L.); (S.-Y.L.); (J.-W.L.)
- Department of Life Science, Graduate Institute of Biotechnology, National Dong-Hwa University, Hualien 97447, Taiwan
| | - Si-Yin Lin
- Everfront Biotech Inc., New Taipei City 22180, Taiwan; (J.-H.L.); (S.-Y.L.); (J.-W.L.)
- Department of Life Science, Graduate Institute of Biotechnology, National Dong-Hwa University, Hualien 97447, Taiwan
| | - Jen-Wei Liu
- Everfront Biotech Inc., New Taipei City 22180, Taiwan; (J.-H.L.); (S.-Y.L.); (J.-W.L.)
- Department of Life Science, Graduate Institute of Biotechnology, National Dong-Hwa University, Hualien 97447, Taiwan
| | - Shinn-Zong Lin
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien 97002, Taiwan;
- Department of Neurosurgery, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Tzu Chi University, Hualien 97002, Taiwan
| | - Horng-Jyh Harn
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien 97002, Taiwan;
- Department of Pathology, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Tzu Chi University, Hualien 97002, Taiwan
| | - Tzyy-Wen Chiou
- Department of Life Science, Graduate Institute of Biotechnology, National Dong-Hwa University, Hualien 97447, Taiwan
| |
Collapse
|
4
|
Thomas DR, Newton P, Lau N, Newton HJ. Interfering with Autophagy: The Opposing Strategies Deployed by Legionella pneumophila and Coxiella burnetii Effector Proteins. Front Cell Infect Microbiol 2020; 10:599762. [PMID: 33251162 PMCID: PMC7676224 DOI: 10.3389/fcimb.2020.599762] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 10/13/2020] [Indexed: 12/14/2022] Open
Abstract
Autophagy is a fundamental and highly conserved eukaryotic process, responsible for maintaining cellular homeostasis and releasing nutrients during times of starvation. An increasingly important function of autophagy is its role in the cell autonomous immune response; a process known as xenophagy. Intracellular pathogens are engulfed by autophagosomes and targeted to lysosomes to eliminate the threat to the host cell. To counteract this, many intracellular bacterial pathogens have developed unique approaches to overcome, evade, or co-opt host autophagy to facilitate a successful infection. The intracellular bacteria Legionella pneumophila and Coxiella burnetii are able to avoid destruction by the cell, causing Legionnaires' disease and Q fever, respectively. Despite being related and employing homologous Dot/Icm type 4 secretion systems (T4SS) to translocate effector proteins into the host cell, these pathogens have developed their own unique intracellular niches. L. pneumophila evades the host endocytic pathway and instead forms an ER-derived vacuole, while C. burnetii requires delivery to mature, acidified endosomes which it remodels into a large, replicative vacuole. Throughout infection, L. pneumophila effectors act at multiple points to inhibit recognition by xenophagy receptors and disrupt host autophagy, ensuring it avoids fusion with destructive lysosomes. In contrast, C. burnetii employs its effector cohort to control autophagy, hypothesized to facilitate the delivery of nutrients and membrane to support the growing vacuole and replicating bacteria. In this review we explore the effector proteins that these two organisms utilize to modulate the host autophagy pathway in order to survive and replicate. By better understanding how these pathogens manipulate this highly conserved pathway, we can not only develop better treatments for these important human diseases, but also better understand and control autophagy in the context of human health and disease.
Collapse
Affiliation(s)
| | | | | | - Hayley J. Newton
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia
| |
Collapse
|
5
|
Hong Z, Pedersen NM, Wang L, Torgersen ML, Stenmark H, Raiborg C. PtdIns3P controls mTORC1 signaling through lysosomal positioning. J Cell Biol 2017; 216:4217-4233. [PMID: 29030394 PMCID: PMC5716264 DOI: 10.1083/jcb.201611073] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 07/04/2017] [Accepted: 08/21/2017] [Indexed: 01/06/2023] Open
Abstract
mTORC1 is activated by lysosome positioning and by amino acid–induced phosphatidylinositol 3-phosphate (PtdIns3P). Hong et al. show that amino acids stimulate recruitment of the PtdIns3P-binding protein FYCO1 to lysosomes and promote contacts between FYCO1 lysosomes and ER that contains the PtdIns3P effector Protrudin, mediating lysosome translocation and facilitating mTORC1 activation. The mechanistic target of rapamycin complex 1 (mTORC1) is a protein kinase complex that localizes to lysosomes to up-regulate anabolic processes and down-regulate autophagy. Although mTORC1 is known to be activated by lysosome positioning and by amino acid–stimulated production of phosphatidylinositol 3-phosphate (PtdIns3P) by the lipid kinase VPS34/PIK3C3, the mechanisms have been elusive. Here we present results that connect these seemingly unrelated pathways for mTORC1 activation. Amino acids stimulate recruitment of the PtdIns3P-binding protein FYCO1 to lysosomes and promote contacts between FYCO1 lysosomes and endoplasmic reticulum that contain the PtdIns3P effector Protrudin. Upon overexpression of Protrudin and FYCO1, mTORC1–positive lysosomes translocate to the cell periphery, thereby facilitating mTORC1 activation. This requires the ability of Protrudin to bind PtdIns3P. Conversely, upon VPS34 inhibition, or depletion of Protrudin or FYCO1, mTORC1-positive lysosomes cluster perinuclearly, accompanied by reduced mTORC1 activity under nutrient-rich conditions. Consequently, the transcription factor EB enters the nucleus, and autophagy is up-regulated. We conclude that PtdIns3P-dependent lysosome translocation to the cell periphery promotes mTORC1 activation.
Collapse
Affiliation(s)
- Zhi Hong
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Nina Marie Pedersen
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Ling Wang
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Maria Lyngaas Torgersen
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Camilla Raiborg
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| |
Collapse
|
6
|
Pittini Á, Casaravilla C, Allen JE, Díaz Á. Pharmacological inhibition of PI3K class III enhances the production of pro- and anti-inflammatory cytokines in dendritic cells stimulated by TLR agonists. Int Immunopharmacol 2016; 36:213-217. [PMID: 27168056 PMCID: PMC4907315 DOI: 10.1016/j.intimp.2016.04.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 04/19/2016] [Indexed: 01/25/2023]
Affiliation(s)
- Álvaro Pittini
- Cátedra de Inmunología, Departamento de Biociencias (Facultad de Química) e Instituto de Química Biológica (Facultad de Ciencias), Universidad de la República, Montevideo, Uruguay
| | - Cecilia Casaravilla
- Cátedra de Inmunología, Departamento de Biociencias (Facultad de Química) e Instituto de Química Biológica (Facultad de Ciencias), Universidad de la República, Montevideo, Uruguay
| | - Judith E Allen
- Institute of Immunology and Infection Research Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Álvaro Díaz
- Cátedra de Inmunología, Departamento de Biociencias (Facultad de Química) e Instituto de Química Biológica (Facultad de Ciencias), Universidad de la República, Montevideo, Uruguay.
| |
Collapse
|
7
|
Marat AL, Haucke V. Phosphatidylinositol 3-phosphates-at the interface between cell signalling and membrane traffic. EMBO J 2016; 35:561-79. [PMID: 26888746 DOI: 10.15252/embj.201593564] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 01/26/2016] [Indexed: 12/31/2022] Open
Abstract
Phosphoinositides (PIs) form a minor class of phospholipids with crucial functions in cell physiology, ranging from cell signalling and motility to a role as signposts of compartmental membrane identity. Phosphatidylinositol 3-phosphates are present at the plasma membrane and within the endolysosomal system, where they serve as key regulators of both cell signalling and of intracellular membrane traffic. Here, we provide an overview of the metabolic pathways that regulate cellular synthesis of PI 3-phosphates at distinct intracellular sites and discuss the mechanisms by which these lipids regulate cell signalling and membrane traffic. Finally, we provide a framework for how PI 3-phosphate metabolism is integrated into the cellular network.
Collapse
Affiliation(s)
- Andrea L Marat
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Volker Haucke
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| |
Collapse
|
8
|
Abstract
Rag small GTPases were identified as the sixth subfamily of Ras-related GTPases. Compelling evidence suggests that Rag heterodimer (RagA/B and RagC/D) plays an important role in amino acid signaling toward mechanistic target of rapamycin complex 1 (mTORC1), which is a central player in the control of cell growth in response to a variety of environmental cues, including growth factors, cellular energy/oxygen status, and amino acids. Upon amino acid stimulation, active Rag heterodimer (RagA/B(GTP)-RagC/D(GDP)) recruits mTORC1 to the lysosomal membrane where Rheb resides. In this review, we provide a current understanding on the amino acid-regulated cell growth control via Rag-mTORC1 with recently identified key players, including Ragulator, v-ATPase, and GATOR complexes. Moreover, the functions of Rag in physiological systems and in autophagy are discussed.
Collapse
|
9
|
Rudge SA, Wakelam MJO. Phosphatidylinositolphosphate phosphatase activities and cancer. J Lipid Res 2015; 57:176-92. [PMID: 26302980 DOI: 10.1194/jlr.r059154] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Indexed: 12/13/2022] Open
Abstract
Signaling through the phosphoinositide 3-kinase pathways mediates the actions of a plethora of hormones, growth factors, cytokines, and neurotransmitters upon their target cells following receptor occupation. Overactivation of these pathways has been implicated in a number of pathologies, in particular a range of malignancies. The tight regulation of signaling pathways necessitates the involvement of both stimulatory and terminating enzymes; inappropriate activation of a pathway can thus result from activation or inhibition of the two signaling arms. The focus of this review is to discuss, in detail, the activities of the identified families of phosphoinositide phosphatase expressed in humans, and how they regulate the levels of phosphoinositides implicated in promoting malignancy.
Collapse
Affiliation(s)
- Simon A Rudge
- Signalling Programme, Babraham Institute, Cambridge CB22 3AT, United Kingdom
| | - Michael J O Wakelam
- Signalling Programme, Babraham Institute, Cambridge CB22 3AT, United Kingdom
| |
Collapse
|
10
|
Kim TM, Baek JH, Kim JH, Oh MS, Kim J. Development of in vitro PIK3C3/VPS34 complex protein assay for autophagy-specific inhibitor screening. Anal Biochem 2015; 480:21-7. [PMID: 25862085 DOI: 10.1016/j.ab.2015.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 04/02/2015] [Accepted: 04/03/2015] [Indexed: 12/13/2022]
Abstract
Autophagy is an important catabolic program to respond to a variety of cellular stresses by forming a double membrane vesicle, autophagosome. Autophagy plays key roles in various cellular functions. Accordingly, dysregulation of autophagy is closely associated with diseases such as diabetes, neurodegenerative diseases, cardiomyopathy, and cancer. In this sense, autophagy is emerging as an important therapeutic target for disease control. Among the autophagy machineries, PIK3C3/VPS34 complex functions as an autophagy-triggering kinase to recruit the subsequent autophagy protein machineries on the phagophore membrane. Accumulating evidence showing that inhibition of PIK3C3/VPS34 complex successfully inhibits autophagy makes the complex an attractive target for developing autophagy inhibitors. However, one concern about PIK3C3/VPS34 complex is that many different PIK3C3/VPS34 complexes have distinct cellular functions. In this study, we have developed an in vitro PIK3C3/VPS34 complex monitoring assay for autophagy inhibitor screening in a high-throughput assay format instead of targeting the catalytic activity of the PIK3C3/VPS34 complex, which shuts down all PIK3C3/VPS34 complexes. We performed in vitro reconstitution of an essential autophagy-promoting PIK3C3/VPS34 complex, Vps34-Beclin1-ATG14L complex, in a microwell plate (96-well format) and successfully monitored the complex formation in many different conditions. This PIK3C3/VPS34 complex protein assay would provide a reliable tool for the screening of autophagy-specific inhibitors.
Collapse
Affiliation(s)
- Tae-Mi Kim
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Jong-Hyuk Baek
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Jeong Hee Kim
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Department of Oral Biochemistry and Molecular Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Myung Sook Oh
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Department of Oriental Pharmaceutical Science, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
| | - Joungmok Kim
- Department of Oral Biochemistry and Molecular Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea.
| |
Collapse
|
11
|
Marcotte GR, West DWD, Baar K. The molecular basis for load-induced skeletal muscle hypertrophy. Calcif Tissue Int 2015; 96:196-210. [PMID: 25359125 PMCID: PMC4809742 DOI: 10.1007/s00223-014-9925-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 10/18/2014] [Indexed: 12/19/2022]
Abstract
In a mature (weight neutral) animal, an increase in muscle mass only occurs when the muscle is loaded sufficiently to cause an increase in myofibrillar protein balance. A tight relationship between muscle hypertrophy, acute increases in protein balance, and the activity of the mechanistic target of rapamycin complex 1 (mTORC1) was demonstrated 15 years ago. Since then, our understanding of the signals that regulate load-induced hypertrophy has evolved considerably. For example, we now know that mechanical load activates mTORC1 in the same way as growth factors, by moving TSC2 (a primary inhibitor of mTORC1) away from its target (the mTORC activator) Rheb. However, the kinase that phosphorylates and moves TSC2 is different in the two processes. Similarly, we have learned that a distinct pathway exists whereby amino acids activate mTORC1 by moving it to Rheb. While mTORC1 remains at the forefront of load-induced hypertrophy, the importance of other pathways that regulate muscle mass are becoming clearer. Myostatin, is best known for its control of developmental muscle size. However, new mechanisms to explain how loading regulates this process are suggesting that it could play an important role in hypertrophic muscle growth as well. Last, new mechanisms are highlighted for how β2 receptor agonists could be involved in load-induced muscle growth and why these agents are being developed as non-exercise-based therapies for muscle atrophy. Overall, the results highlight how studying the mechanism of load-induced skeletal muscle mass is leading the development of pharmaceutical interventions to promote muscle growth in those unwilling or unable to perform resistance exercise.
Collapse
Affiliation(s)
- George R Marcotte
- Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, CA, USA
| | | | | |
Collapse
|
12
|
Regulation of autophagy by amino acids and MTOR-dependent signal transduction. Amino Acids 2014; 47:2037-63. [PMID: 24880909 PMCID: PMC4580722 DOI: 10.1007/s00726-014-1765-4] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Accepted: 05/12/2014] [Indexed: 01/05/2023]
Abstract
Amino acids not only participate in intermediary metabolism but also stimulate insulin-mechanistic target of rapamycin (MTOR)-mediated signal transduction which controls the major metabolic pathways. Among these is the pathway of autophagy which takes care of the degradation of long-lived proteins and of the elimination of damaged or functionally redundant organelles. Proper functioning of this process is essential for cell survival. Dysregulation of autophagy has been implicated in the etiology of several pathologies. The history of the studies on the interrelationship between amino acids, MTOR signaling and autophagy is the subject of this review. The mechanisms responsible for the stimulation of MTOR-mediated signaling, and the inhibition of autophagy, by amino acids have been studied intensively in the past but are still not completely clarified. Recent developments in this field are discussed.
Collapse
|
13
|
Wang L, Lin Y, Bian Y, Liu L, Shao L, Lin L, Qu B, Zhao F, Gao X, Li Q. Leucyl-tRNA synthetase regulates lactation and cell proliferation via mTOR signaling in dairy cow mammary epithelial cells. Int J Mol Sci 2014; 15:5952-69. [PMID: 24722568 PMCID: PMC4013607 DOI: 10.3390/ijms15045952] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 03/28/2014] [Accepted: 03/28/2014] [Indexed: 01/06/2023] Open
Abstract
The role of LeuRS, an aminoacyl-tRNA synthetase, as an intracellular l-leucine sensor for the mTORC1 pathway has been the subject of much research recently. Despite this, the association between LeuRS and lactation in dairy cow mammary epithelial cells (DCMECs) remains unknown. In this study, we found that LeuRS expression in mammary gland tissue was significantly higher during lactation than pregnancy. Moreover, our data demonstrates that LeuRS is localized in the cytoplasm. Treatment with leucine increased DCMECs viability and proliferation, as well as mammalian target of rapamycin (mTOR), p-mTOR, ribosomal protein S6 kinase 1 (S6K1), p-S6K1, β-Casein, sterol regulatory element binding protein 1c (SREBP-1c), glucose transporter 1 (GLUT1), and Cyclin D1 mRNA and protein expression. Secretion of lactose and triglyceride were also increased. siRNA-mediated knockdown of LeuRS led to reduction in all of these processes. Based on these data, LeuRS up-regulates the mTOR pathway to promote proliferation and lactation of DCMECs in response to changes in the intracellular leucine concentration.
Collapse
Affiliation(s)
- Lina Wang
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Ye Lin
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Yanjie Bian
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Lili Liu
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Li Shao
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Lin Lin
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Bo Qu
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Feng Zhao
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Xuejun Gao
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| | - Qingzhang Li
- Key Laboratory of Dairy Science of Ministry of Education, Northeast Agricultural University, Harbin 150030, China.
| |
Collapse
|
14
|
Leprince AS, Magalhaes N, De Vos D, Bordenave M, Crilat E, Clément G, Meyer C, Munnik T, Savouré A. Involvement of Phosphatidylinositol 3-kinase in the regulation of proline catabolism in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2014; 5:772. [PMID: 25628629 PMCID: PMC4290513 DOI: 10.3389/fpls.2014.00772] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 12/15/2014] [Indexed: 05/03/2023]
Abstract
Plant adaptation to abiotic stresses such as drought and salinity involves complex regulatory processes. Deciphering the signaling components that are involved in stress signal transduction and cellular responses is of importance to understand how plants cope with salt stress. Accumulation of osmolytes such as proline is considered to participate in the osmotic adjustment of plant cells to salinity. Proline accumulation results from a tight regulation between its biosynthesis and catabolism. Lipid signal components such as phospholipases C and D have previously been shown to be involved in the regulation of proline metabolism in Arabidopsis thaliana. In this study, we demonstrate that proline metabolism is also regulated by class-III Phosphatidylinositol 3-kinase (PI3K), VPS34, which catalyses the formation of phosphatidylinositol 3-phosphate (PI3P) from phosphatidylinositol. Using pharmacological and biochemical approaches, we show that the PI3K inhibitor, LY294002, affects PI3P levels in vivo and that it triggers a decrease in proline accumulation in response to salt treatment of A. thaliana seedlings. The lower proline accumulation is correlated with a lower transcript level of Pyrroline-5-carboxylate synthetase 1 (P5CS1) biosynthetic enzyme and higher transcript and protein levels of Proline dehydrogenase 1 (ProDH1), a key-enzyme in proline catabolism. We also found that the ProDH1 expression is induced in a pi3k-hemizygous mutant, further demonstrating that PI3K is involved in the regulation of proline catabolism through transcriptional regulation of ProDH1. A broader metabolomic analysis indicates that LY294002 also reduced other metabolites, such as hydrophobic and aromatic amino acids and sugars like raffinose.
Collapse
Affiliation(s)
- Anne-Sophie Leprince
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant SciencesVersailles, France
- *Correspondence: Anne-Sophie Leprince and Arnould Savouré, Sorbonne Universités, UPMC Univ Paris 06, APCE URF5, Case 156, 4 Place Jussieu, F-75252, Paris 05, France e-mail: ;
| | - Nelly Magalhaes
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant SciencesVersailles, France
| | - Delphine De Vos
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant SciencesVersailles, France
| | - Marianne Bordenave
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
| | - Emilie Crilat
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
| | - Gilles Clément
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant SciencesVersailles, France
| | - Christian Meyer
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant SciencesVersailles, France
| | - Teun Munnik
- Section Plant Physiology, Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, Netherlands
| | - Arnould Savouré
- Sorbonne Universités, Universite Pierre et Marie Curie Univ Paris 06, Adaptation de Plantes aux Contraintes Environnementales, URF5Paris, France
- *Correspondence: Anne-Sophie Leprince and Arnould Savouré, Sorbonne Universités, UPMC Univ Paris 06, APCE URF5, Case 156, 4 Place Jussieu, F-75252, Paris 05, France e-mail: ;
| |
Collapse
|
15
|
Rundqvist HC, Lilja MR, Rooyackers O, Odrzywol K, Murray JT, Esbjörnsson M, Jansson E. Nutrient ingestion increased mTOR signaling, but not hVps34 activity in human skeletal muscle after sprint exercise. Physiol Rep 2013; 1:e00076. [PMID: 24303161 PMCID: PMC3841023 DOI: 10.1002/phy2.76] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 08/03/2013] [Accepted: 08/05/2013] [Indexed: 12/11/2022] Open
Abstract
Nutrient provision after sprint exercise enhances mammalian target of rapamycin (mTOR) signaling. One suggested that nutrient sensor is the class III phosphatidylinositol 3-kinase, vacuolar protein sorting 34 (Vps34), not previously studied in human skeletal muscle. It is hypothesized that oral ingestion of essential amino acids (EAA) and carbohydrates (Carb) increases Vps34 activity and mTOR signaling in human skeletal (hVps34) muscle after sprint exercise. Nine subjects were performed 3 × 30-sec all-out sprints with or without ingestion of EAA + Carb or placebo drinks in a randomized order with a month interval. Muscle biopsies were performed at rest and 140 min after last sprint and analyzed for p-mTOR, p-p70S6k, p-eEF2 and for hVps34 activity and hVps34 protein content. Venous blood samples were collected and analyzed for amino acids, glucose, lactate, and insulin. During the sprint exercise session, EAA, glucose, and insulin in blood increased significantly more in EAA + Carb than in placebo. P-mTOR and p-p70S6k were significantly increased above rest in EAA + Carb (P = 0.03, P = 0.007) 140 min after last sprint, but not in placebo. Activity and protein expression of hVps34 were not significantly changed from rest in EAA + Carb 140 min after the last sprint. However, hVps34 activity and protein expression tended to increase in placebo (both P = 0.08). In conclusion, on the contrary to the hypothesis, no increase in activation of hVps34 was found following sprint exercise in EAA + Carb condition. In spite of this, the results support an activation of mTOR during this condition. However, this does not exclude the permissive role of hVps34 in mediating the amino acid-induced activation of mTOR and muscle protein synthesis.
Collapse
Affiliation(s)
- Håkan C Rundqvist
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet Stockholm, Sweden ; Department of Clinical Physiology, Karolinska University Hospital Stockholm, Sweden
| | | | | | | | | | | | | |
Collapse
|
16
|
Musiwaro P, Smith M, Manifava M, Walker SA, Ktistakis NT. Characteristics and requirements of basal autophagy in HEK 293 cells. Autophagy 2013; 9:1407-17. [PMID: 23800949 DOI: 10.4161/auto.25455] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Basal autophagy-here defined as macroautophagic activity during cellular growth in normal medium containing amino acids and serum-appears to be highly active in many cell types and in animal tissues. Here we characterized this pathway in mammalian HEK 293 cells. First, we examined, side by side, three compounds that are widely used to reveal basal autophagy by blocking maturation of autophagosomes: bafilomycin A 1 (BafA1), chloroquine and vinblastine. Only BafA1 appeared to be without complicating side effects. Chloroquine partially inhibited mechanistic target of rapamycin (MTOR) activity, which would induce autophagy induction as well as block autophagosome maturation. Vinblastine caused the distribution of early omegasome components into punctate phagophore assembly sites, and therefore it would also induce autophagy, complicating interpretation. Basal autophagy was significantly sensitive to inhibition by wortmannin, and therefore required formation of phosphatidylinositol 3-phosphate (PtdIns3P), but it was twice as resistant to wortmannin as starvation-induced autophagy. We also determined that basal autophagy was significantly suppressed by MTOR activation brought about by overexpression of RHEB or activated RAGs. Finally we investigated the spatial relationship of nascent autophagosomes to the endoplasmic reticulum (ER) or to mitochondria by live imaging experiments under conditions that reveal basal autophagy (with BafA1 treatment), or upon MTOR inactivation (which would result in autophagy induction). Side-by-side comparison showed that under both basal and induced autophagy, 100% of autophagosomes first appeared in close proximity to ER strands. In parallel measurements, 40% were in close proximity to mitochondria under both conditions. We concluded that in HEK 293 cells, basal autophagy is mechanistically similar to that induced by MTOR inactivation in all aspects examined.
Collapse
|
17
|
Abstract
Phosphoinositide 3-kinases (PI3Ks) control many important aspects of immune cell development, differentiation, and function. Mammals have eight PI3K catalytic subunits that are divided into three classes based on similarities in structure and function. Specific roles for the class I PI3Ks have been broadly investigated and are relatively well understood, as is the function of their corresponding phosphatases. More recently, specific roles for the class II and class III PI3Ks have emerged. Through vertebrate evolution and in parallel with the evolution of adaptive immunity, there has been a dramatic increase not only in the genes for PI3K subunits but also in genes for phosphatases that act on 3-phosphoinositides and in 3-phosphoinositide-binding proteins. Our understanding of the PI3Ks in immunity is guided by fundamental discoveries made in simpler model organisms as well as by appreciating new adaptations of this signaling module in mammals in general and in immune cells in particular.
Collapse
Affiliation(s)
- Klaus Okkenhaug
- Laboratory of Lymphocyte Signaling and Development, The Babraham Institute, Cambridge, CB22 3AT, United Kingdom.
| |
Collapse
|
18
|
Bischoff P, Josset E, Dumont FJ. Novel pharmacological modulators of autophagy and therapeutic prospects. Expert Opin Ther Pat 2012; 22:1053-79. [PMID: 22860892 DOI: 10.1517/13543776.2012.715148] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Autophagy is an intracellular process of self-digestion involving the lysosomal degradation of cytoplasmic organelles and macromolecules. It occurs at low basal levels to perform housekeeping functions and is dramatically augmented upon nutrient depletion or exposure to other stresses, thus maintaining cellular homeostasis and energy balance and providing cytoprotective responses to adverse conditions. Mounting evidence that autophagy malfunction contributes to the pathogenesis of diverse human diseases has stimulated efforts to identify pharmacological agents that modulate autophagy in potentially beneficial ways. Here, we review the progresses accomplished toward this goal in recent years, as reflected by the patent literature. AREAS COVERED Patent applications published from 2008 to mid-2012 that pertain to the pharmacological modulation of autophagy are reviewed and their potential therapeutic utilities are discussed. EXPERT OPINION Of 40 patents related to autophagy, 21 claim novel enhancers or inhibitors of autophagy. One of the most promising applications of these compounds concerns cancer therapy, a few of them being already considered for clinical evaluation. Further work is, however, needed to identify compounds that target unique molecular effectors/regulators of autophagy to selectively modulate its various stages in different tissues and to design therapeutic interventions applicable to a broad variety of dysfunctional autophagy-associated disorders.
Collapse
Affiliation(s)
- Pierre Bischoff
- Université de Strasbourg, Centre Régional de Lutte contre le Cancer Paul Strauss, 3 rue de la Porte de l'Hôpital, Strasbourg, France
| | | | | |
Collapse
|
19
|
Decuypere JP, Parys JB, Bultynck G. Regulation of the autophagic bcl-2/beclin 1 interaction. Cells 2012; 1:284-312. [PMID: 24710477 PMCID: PMC3901098 DOI: 10.3390/cells1030284] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 06/06/2012] [Accepted: 06/15/2012] [Indexed: 12/18/2022] Open
Abstract
Autophagy is an intracellular degradation process responsible for the delivery of cellular material to the lysosomes. One of the key mechanisms for control of autophagy is the modulation of the interaction between the autophagic protein Beclin 1 and the members of the anti-apoptotic Bcl-2 family (e.g., Bcl-2, Bcl-XL and Mcl-1). This binding is regulated by a variety of proteins and compounds that are able to enhance or inhibit the Bcl-2/Beclin 1 interaction in order to repress or activate autophagy, respectively. In this review we will focus on this interaction and discuss its characteristics, relevance and regulation.
Collapse
Affiliation(s)
- Jean-Paul Decuypere
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, O/N-1, bus 802, Herestraat 49, Leuven, BE-3000, Belgium.
| | - Jan B Parys
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, O/N-1, bus 802, Herestraat 49, Leuven, BE-3000, Belgium.
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, O/N-1, bus 802, Herestraat 49, Leuven, BE-3000, Belgium.
| |
Collapse
|