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Kwak JH, Lee YK, Jun MH, Roh M, Seo H, Lee J, Lee K, Lee JA. Autophagy activity contributes to the impairment of social recognition in Epac2 -/- mice. Mol Brain 2021; 14:100. [PMID: 34183057 PMCID: PMC8240198 DOI: 10.1186/s13041-021-00814-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 06/16/2021] [Indexed: 11/10/2022] Open
Abstract
Autophagy is a lysosomal degradation pathway that regulates cellular homeostasis. It is constitutively active in neurons and controls the essential steps of neuronal development, leading to its dysfunction in neurodevelopmental disorders. Although mTOR-associated impaired autophagy has previously been reported in neurodevelopmental disorders, there is lack of information about the dysregulation of mTOR-independent autophagy in neurodevelopmental disorders. In this study, we investigated whether the loss of Epac2, involved in the mTOR-independent pathway, affects autophagy activity and whether the activity of autophagy is associated with social-behavioral phenotypes in mice with Epac2 deficiencies. We observed an accumulation of autophagosomes and a significant increase in autophagic flux in Epac2-deficient neurons, which had no effect on mTOR activity. Next, we examined whether an increase in autophagic activity contributed to the social behavior exhibited in Epac2-/- mice. The social recognition deficit observed in Epac2-/- mice recovered in double transgenic Epac2-/-: Atg5+/- mice. Our study suggests that excessive autophagy due to Epac2 deficiencies may contribute to social recognition defects through an mTOR-independent pathway.
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Affiliation(s)
- Ji-Hye Kwak
- Behavioral Neural Circuitry and Physiology Laboratory, Department of Anatomy, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, 41944, South Korea
| | - You-Kyung Lee
- Department of Biological Sciences and Biotechnology, College of Life Sciences and Nanotechnology, Hannam University, Daejeon, South Korea
| | - Mi-Hee Jun
- Department of Biological Sciences and Biotechnology, College of Life Sciences and Nanotechnology, Hannam University, Daejeon, South Korea
| | - Mootaek Roh
- Behavioral Neural Circuitry and Physiology Laboratory, Department of Anatomy, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, 41944, South Korea
| | - Hyunhyo Seo
- Behavioral Neural Circuitry and Physiology Laboratory, Department of Anatomy, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, 41944, South Korea
| | - Juhyun Lee
- Behavioral Neural Circuitry and Physiology Laboratory, Department of Anatomy, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, 41944, South Korea
| | - Kyungmin Lee
- Behavioral Neural Circuitry and Physiology Laboratory, Department of Anatomy, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, 41944, South Korea.
| | - Jin-A Lee
- Department of Biological Sciences and Biotechnology, College of Life Sciences and Nanotechnology, Hannam University, Daejeon, South Korea.
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2
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Hu YD, Tang CL, Jiang JZ, Lv HY, Wu YB, Qin XD, Shi S, Zhao B, Zhu XN, Xia ZY. Neuroprotective Effects of Dexmedetomidine Preconditioning on Oxygen-glucose Deprivation-reoxygenation Injury in PC12 Cells via Regulation of Ca 2+-STIM1/Orai1 Signaling. Curr Med Sci 2020; 40:699-707. [PMID: 32862381 DOI: 10.1007/s11596-020-2201-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 06/30/2020] [Indexed: 12/26/2022]
Abstract
Dexmedetomidine (DEX), a potent and highly selective agonist for α2-adrenergic receptors (α2AR), exerts neuroprotective effects by reducing apoptosis through decreased neuronal Ca2+ influx. However, the exact action mechanism of DEX and its effects on oxygen-glucose deprivation-reoxygenation (OGD/R) injury in vitro are unknown. We demonstrate that DEX pretreatment reduced OGD/R injury in PC12 cells, as evidenced by decreased oxidative stress, autophagy, and neuronal apoptosis. Specifically, DEX pretreatment decreased the expression levels of stromal interaction molecule 1 (STIM1) and calcium release-activated calcium channel protein 1 (Orai1), and reduced the concentration of intracellular calcium pools. In addition, variations in cytosolic calcium concentration altered apoptosis rate of PC12 cells after exposure to hypoxic conditions, which were modulated through STIM1/Orai1 signaling. Moreover, DEX pretreatment decreased the expression levels of Beclin-1 and microtubule-associated protein 1A/1B-light chain 3 (LC3), hallmark markers of autophagy, and the formation of autophagosomes. In conclusion, these results suggested that DEX exerts neuroprotective effects against oxidative stress, autophagy, and neuronal apoptosis after OGD/R injury via modulation of Ca2+-STIM1/Orai1 signaling. Our results offer insights into the molecular mechanisms of DEX in protecting against neuronal ischemia-reperfusion injury.
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Affiliation(s)
- Yi-da Hu
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Chao-Liang Tang
- Department of Anesthesiology, the First Affiliated Hospital of University of Science and Technology of China, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China
| | - Jia-Zhen Jiang
- Department of Emergency, Huashan Hospital North, Fudan University, Shanghai, 201907, China
| | - Hai-Yan Lv
- Department of Neurology, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai, 201620, China
| | - Yuan-Bo Wu
- Department of Neurology, the First Affiliated Hospital of University of Science and Technology of China, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China
| | - Xiu-de Qin
- Department of Neurology, Shenzhen Traditional Chinese Medicine Hospital, the Fourth Clinical Medical College of Guangzhou University of Chinese Medicine, Shenzhen, 518033, China
| | - Si Shi
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Bo Zhao
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Xiao-Nan Zhu
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Zhong-Yuan Xia
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, China.
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3
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Kim H, Williams D, Qiu Y, Song Z, Yang Z, Kimler V, Goldberg A, Zhang R, Yang Z, Chen X, Wang L, Fang D, Lin JD, Zhang K. Regulation of hepatic autophagy by stress-sensing transcription factor CREBH. FASEB J 2019; 33:7896-7914. [PMID: 30912978 DOI: 10.1096/fj.201802528r] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophagy, a lysosomal degradative pathway in response to nutrient limitation, plays an important regulatory role in lipid homeostasis upon energy demands. Here, we demonstrated that the endoplasmic reticulum-tethered, stress-sensing transcription factor cAMP-responsive element-binding protein, hepatic-specific (CREBH) functions as a major transcriptional regulator of hepatic autophagy and lysosomal biogenesis in response to nutritional or circadian signals. CREBH deficiency led to decreased hepatic autophagic activities and increased hepatic lipid accumulation upon starvation. Under unfed or during energy-demanding phases of the circadian cycle, CREBH is activated to drive expression of the genes encoding the key enzymes or regulators in autophagosome formation or autophagic process, including microtubule-associated protein 1B-light chain 3, autophagy-related protein (ATG)7, ATG2b, and autophagosome formation Unc-51 like kinase 1, and the genes encoding functions in lysosomal biogenesis and homeostasis. Upon nutrient starvation, CREBH regulates and interacts with peroxisome proliferator-activated receptor α (PPARα) and PPARγ coactivator 1α to synergistically drive expression of the key autophagy genes and transcription factor EB, a master regulator of lysosomal biogenesis. Furthermore, CREBH regulates rhythmic expression of the key autophagy genes in the liver in a circadian-dependent manner. In summary, we identified CREBH as a key transcriptional regulator of hepatic autophagy and lysosomal biogenesis for the purpose of maintaining hepatic lipid homeostasis under nutritional stress or circadian oscillation.-Kim, H., Williams, D., Qiu, Y., Song, Z., Yang, Z., Kimler, V., Goldberg, A., Zhang, R., Yang, Z., Chen, X., Wang, L., Fang, D., Lin, J. D., Zhang, K. Regulation of hepatic autophagy by stress-sensing transcription factor CREBH.
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Affiliation(s)
- Hyunbae Kim
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Dreana Williams
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Yining Qiu
- Department of Pediatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhenfeng Song
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Zhao Yang
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Victoria Kimler
- Eye Research Institute, Oakland University, Rochester, Michigan, USA
| | - Andrew Goldberg
- Eye Research Institute, Oakland University, Rochester, Michigan, USA
| | - Ren Zhang
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Zengquan Yang
- Karmanos Cancer Institute, Wayne State University, Detroit, Michigan, USA
| | - Xuequn Chen
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Li Wang
- Department of Physiology and Neurobiology-Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, USA.,Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA.,Department of Internal Medicine, Liver Center, Yale University, New Haven, Connecticut, USA
| | - Deyu Fang
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Jiandie D Lin
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Kezhong Zhang
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA.,Department of Biochemistry, Microbiology, and Immunology, Wayne State University School of Medicine, Wayne State University, Detroit, Michigan, USA.,Karmanos Cancer Institute, Wayne State University, Detroit, Michigan, USA
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4
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Chu KY, O'Reilly L, Mellet N, Meikle PJ, Bartley C, Biden TJ. Oleate disrupts cAMP signaling, contributing to potent stimulation of pancreatic β-cell autophagy. J Biol Chem 2018; 294:1218-1229. [PMID: 30518550 DOI: 10.1074/jbc.ra118.004833] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 11/19/2018] [Indexed: 12/12/2022] Open
Abstract
Autophagy is critical for maintaining cellular function via clearance of excess nutrients and damaged organelles. In pancreatic β-cells, it helps counter the endoplasmic reticulum (ER) stress that impairs insulin secretory capacity during Type 2 diabetes. Chronic exposure of β-cells to saturated fatty acids (FAs) such as palmitate stimulates ER stress and modulates autophagy, but the effects of unsaturated FAs such as oleate, which are also elevated during obesity, are less well understood. We therefore treated MIN6 cells and mouse islets for 8-48 h with either palmitate or oleate, and then monitored autophagic flux, signaling pathways, lysosomal biology, and phospholipid profiles. Compared with palmitate, oleate more effectively stimulated both autophagic flux and clearance of autophagosomes. The flux stimulation occurred independently of ER stress, nutrient-sensing (mTOR) and signaling pathways (protein kinases A, C, and D). Instead the mechanism involved the exchange factor directly activated by cAMP 2 (EPAC2). Oleate reduced cellular cAMP, and its effects on autophagic flux were reproduced or inhibited, respectively, by Epac2 knockdown or activation. Oleate also increased lysosomal acidity and increased phospholipid saturation, consistent with improved autophagosomal fusion with lysosomes. We conclude that a potent stimulation of autophagy might help explain the known benefits of unsaturated FAs in countering the toxicity of saturated FAs in β-cells during obesity and lipid loading.
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Affiliation(s)
- Kwan Yi Chu
- Division of Diabetes and Metabolism, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010; St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, NSW 2052
| | - Liam O'Reilly
- Division of Diabetes and Metabolism, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010
| | - Natalie Mellet
- Baker IDI Heart and Diabetes Institute, Prahran, Victoria 3004, Australia
| | - Peter J Meikle
- Baker IDI Heart and Diabetes Institute, Prahran, Victoria 3004, Australia
| | - Clarissa Bartley
- Division of Diabetes and Metabolism, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010
| | - Trevor J Biden
- Division of Diabetes and Metabolism, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010; St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, NSW 2052.
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5
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Velentzas PD, Zhang L, Das G, Chang TK, Nelson C, Kobertz WR, Baehrecke EH. The Proton-Coupled Monocarboxylate Transporter Hermes Is Necessary for Autophagy during Cell Death. Dev Cell 2018; 47:281-293.e4. [PMID: 30318245 DOI: 10.1016/j.devcel.2018.09.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 07/25/2018] [Accepted: 09/14/2018] [Indexed: 02/06/2023]
Abstract
Nutrient availability influences the production and degradation of materials that are required for cell growth and survival. Autophagy is a nutrient-regulated process that is used to degrade cytoplasmic materials and has been associated with human diseases. Solute transporters influence nutrient availability and sensing, yet we know little about how transporters influence autophagy. Here, we screen for solute transporters that are required for autophagy-dependent cell death and identify CG11665/hermes. We show that hermes is required for both autophagy during steroid-triggered salivary gland cell death and TNF-induced non-apoptotic eye cell death. hermes encodes a proton-coupled monocarboxylate transporter that preferentially transports pyruvate over lactate. mTOR signaling is elevated in hermes mutant cells, and decreased mTOR function suppresses the hermes salivary gland cell death phenotype. Hermes is most similar to human SLC16A11, a protein that was recently implicated in type 2 diabetes, thus providing a link between pyruvate, mTOR, autophagy, and possibly metabolic disorders.
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Affiliation(s)
- Panagiotis D Velentzas
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Lejie Zhang
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Gautam Das
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Tsun-Kai Chang
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Cancer Immunology, Genentech Inc, South San Francisco, CA 94080, USA
| | - Charles Nelson
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - William R Kobertz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Eric H Baehrecke
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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6
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Sinha RA, Singh BK, Yen PM. Reciprocal Crosstalk Between Autophagic and Endocrine Signaling in Metabolic Homeostasis. Endocr Rev 2017; 38:69-102. [PMID: 27901588 DOI: 10.1210/er.2016-1103] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 11/28/2016] [Indexed: 12/19/2022]
Abstract
Autophagy is a cellular quality control and energy-providing process that is under strict control by intra- and extracellular stimuli. Recently, there has been an exponential increase in autophagy research and its implications for mammalian physiology. Autophagy deregulation is now being implicated in many human diseases, and its modulation has shown promising results in several preclinical studies. However, despite the initial discovery of autophagy as a hormone-regulated process by De Duve in the early 1960s, endocrine regulation of autophagy still remains poorly understood. In this review, we provide a critical summary of our present understanding of the basic mechanism of autophagy, its regulation by endocrine hormones, and its contribution to endocrine and metabolic homeostasis under physiological and pathological settings. Understanding the cross-regulation of hormones and autophagy on endocrine cell signaling and function will provide new insight into mammalian physiology as well as promote the development of new therapeutic strategies involving modulation of autophagy in endocrine and metabolic disorders.
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Affiliation(s)
- Rohit A Sinha
- Program of Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School Singapore, Singapore 169016
| | - Brijesh K Singh
- Program of Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School Singapore, Singapore 169016
| | - Paul M Yen
- Program of Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School Singapore, Singapore 169016
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7
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Protein Kinase A Activation Promotes Cancer Cell Resistance to Glucose Starvation and Anoikis. PLoS Genet 2016; 12:e1005931. [PMID: 26978032 PMCID: PMC4792400 DOI: 10.1371/journal.pgen.1005931] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 02/22/2016] [Indexed: 12/13/2022] Open
Abstract
Cancer cells often rely on glycolysis to obtain energy and support anabolic growth. Several studies showed that glycolytic cells are susceptible to cell death when subjected to low glucose availability or to lack of glucose. However, some cancer cells, including glycolytic ones, can efficiently acquire higher tolerance to glucose depletion, leading to their survival and aggressiveness. Although increased resistance to glucose starvation has been shown to be a consequence of signaling pathways and compensatory metabolic routes activation, the full repertoire of the underlying molecular alterations remain elusive. Using omics and computational analyses, we found that cyclic adenosine monophosphate-Protein Kinase A (cAMP-PKA) axis activation is fundamental for cancer cell resistance to glucose starvation and anoikis. Notably, here we show that such a PKA-dependent survival is mediated by parallel activation of autophagy and glutamine utilization that in concert concur to attenuate the endoplasmic reticulum (ER) stress and to sustain cell anabolism. Indeed, the inhibition of PKA-mediated autophagy or glutamine metabolism increased the level of cell death, suggesting that the induction of autophagy and metabolic rewiring by PKA is important for cancer cellular survival under glucose starvation. Importantly, both processes actively participate to cancer cell survival mediated by suspension-activated PKA as well. In addition we identify also a PKA/Src mechanism capable to protect cancer cells from anoikis. Our results reveal for the first time the role of the versatile PKA in cancer cells survival under chronic glucose starvation and anoikis and may be a novel potential target for cancer treatment. Tumor heterogeneity exists in many human cancers, and it has been shown that it can play a role in tumor progression. Indeed, cell diversity may be critically important when tumors experience selective pressures, like nutrient deprivation, hypoxia, chemotherapy. PKA, through incompletely understood mechanisms, controls several cellular processes like cell growth, cell differentiation, cell metabolism, cell migration and, as more recently observed, also cancer progression. In this work, we show that activation of PKA induces the ability of a cancer cell sub-population to survive under strong stress conditions namely nutrient deprivation and cell detachment. Indeed, PKA activation in these cells results in autophagy induction, and at the same time, in activation of glutamine metabolism and Src kinase. Importantly, blocking directly the PKA pathway, as well as the autophagy, the glutamine metabolism or the Src pathway by inhibitory drugs, almost completely prevents cell growth of this sub-population of resistant cancer cells. These results suggest that drugs, targeting especially PKA pathway as well as downstream processes like autophagy, glutamine metabolism and Src signaling, may specifically inhibit cancer cells ability to survive under selective pressure favoring cancer resistance.
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8
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Seglen PO, Luhr M, Mills IG, Sætre F, Szalai P, Engedal N. Macroautophagic cargo sequestration assays. Methods 2015; 75:25-36. [DOI: 10.1016/j.ymeth.2014.12.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/17/2014] [Accepted: 12/31/2014] [Indexed: 11/27/2022] Open
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9
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Regulation of autophagy by amino acid availability in S. cerevisiae and mammalian cells. Amino Acids 2014; 47:2165-75. [PMID: 24973972 DOI: 10.1007/s00726-014-1787-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 06/12/2014] [Indexed: 10/25/2022]
Abstract
Autophagy is a catabolic membrane-trafficking process that occurs in all eukaryotic organisms analyzed to date. The study of autophagy has exploded over the last decade or so, branching into numerous aspects of cellular and organismal physiology. From basic functions in starvation and quality control, autophagy has expanded into innate immunity, aging, neurological diseases, redox regulation, and ciliogenesis, to name a few roles. In the present review, I would like to narrow the discussion to the more classical roles of autophagy in supporting viability under nutrient limitation. My aim is to provide a semblance of a historical overview, together with a concise, and perhaps subjective, mechanistic and functional analysis of the central questions in the autophagy field.
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10
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Schroeder S, Zimmermann A, Carmona-Gutierrez D, Eisenberg T, Ruckenstuhl C, Andryushkova A, Pendl T, Harger A, Madeo F. Metabolites in aging and autophagy. MICROBIAL CELL 2014; 1:110-114. [PMID: 28357231 PMCID: PMC5349198 DOI: 10.15698/mic2014.04.142] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Sabrina Schroeder
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Andreas Zimmermann
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Didac Carmona-Gutierrez
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Christoph Ruckenstuhl
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Aleksandra Andryushkova
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Tobias Pendl
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - Alexandra Harger
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria. ; Division of Endocrinology and Metabolism, Dept. of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
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Abstract
Autophagy is used by the cell to degrade various substrates; this is achieved either through the canonical, non-selective autophagy pathway or through selective autophagy. Both pathways proceed via distinct key steps and use specific molecular mechanisms. The canonical autophagy pathway has been studied in detail in mammalian cells and in model organisms, such as yeast. The molecular mechanisms underlying non-canonical autophagy, in addition to alternative pathways that are independent of some of the key autophagy machinery, are beginning to become clear. Besides degradation of cellular proteins, autophagy proteins are also involved in many other functions, some of which are important during bacterial infections. Autophagy functions as an antibacterial mechanism. The induction and recognition mechanisms for several bacterial species have been elucidated. Bacteria can escape killing by autophagy and some can even use autophagy to promote infection of host cells, through the interaction between bacterial effector proteins and autophagy components. The knowledge about bacteria–autophagy interactions will inform the design of new drugs and treatments against bacterial infections.
Autophagy not only degrades components of host cells but can also target intracellular bacteria and thus contribute to host defences. Here, Huang and Brumell discuss the canonical and selective pathways of antibacterial autophagy, as well as the ways in which bacteria can escape from them and sometimes even use them to promote infection. Autophagy is a cellular process that targets proteins, lipids and organelles to lysosomes for degradation, but it has also been shown to combat infection with various pathogenic bacteria. In turn, bacteria have developed diverse strategies to avoid autophagy by interfering with autophagy signalling or the autophagy machinery and, in some cases, they even exploit autophagy for their growth. In this Review, we discuss canonical and non-canonical autophagy pathways and our current knowledge of antibacterial autophagy, with a focus on the interplay between bacterial factors and autophagy components.
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12
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Inoue H, Hase K, Segawa A, Takita T. H89 (N-[2-p-bromocinnamylamino-ethyl]-5-isoquinolinesulphonamide) induces autophagy independently of protein kinase A inhibition. Eur J Pharmacol 2013; 714:170-7. [PMID: 23810683 DOI: 10.1016/j.ejphar.2013.06.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 06/19/2013] [Indexed: 01/02/2023]
Abstract
Autophagy is a degradation pathway for cytoplasmic proteins and organelles in eukaryotes. Although the mechanisms of autophagy regulation are not completely understood, the target of rapamycin (TOR) signaling pathway plays a major role in controlling the induction of autophagy. Cyclic adenosine monophosphate (cAMP)/cAMP-dependent protein kinase A (PKA) has also been shown to regulate autophagy in yeast and mammalian cells. In an effort to elucidate the role of the cAMP/PKA pathway in autophagy, we used the PKA inhibitor N-[2-p-bromocinnamylamino-ethyl]-5-isoquinolinesulphonamide (H89) to treat mammalian cells. Our data demonstrated that H89 induced autophagy at 10 μM, which is a commonly used concentration for PKA inhibition, but PKA inhibition was not involved in the induction of autophagy. The effects of cAMP on autophagy seemed to be dependent on the cell type and the culture conditions. In addition, we investigated which protein kinase was involved in H89-induced autophagy because several kinases other than PKA have been shown to be inhibited by 10 μM of H89. There was no protein kinase largely responsible for autophagy induction, although the inhibition of Akt, which is a downstream effector protein kinase of phosphatidylinositol-3-kinase, appeared to be partially associated. Furthermore, H89-induced autophagy was independent of TOR. H89 is a widely used PKA inhibitor, but PKA-independent effects have been reported. Therefore, it is suggested that autophagy induction is a nonspecific effect of H89, and H89-induced autophagy is independent of the cAMP-PKA and the TOR pathways.
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Affiliation(s)
- Hiroko Inoue
- Department of Electrical, Engineering and Bioscience, Center for Advanced Biomedical Sciences, Waseda University, TWIns, 2-2, Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
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13
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Insel PA, Zhang L, Murray F, Yokouchi H, Zambon AC. Cyclic AMP is both a pro-apoptotic and anti-apoptotic second messenger. Acta Physiol (Oxf) 2012; 204:277-87. [PMID: 21385327 DOI: 10.1111/j.1748-1716.2011.02273.x] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The second messenger cyclic AMP (cAMP) can either stimulate or inhibit programmed cell death (apoptosis). Here, we review examples of cell types that show pro-apoptotic or anti-apoptotic responses to increases in cAMP. We also show that cells can have both such responses, although predominantly having one or the other. Protein kinase A (PKA)-promoted changes in phosphorylation and gene expression can mediate pro-apoptotic responses, such as in murine S49 lymphoma cells, based on evidence that mutants lacking PKA fail to undergo cAMP-promoted, mitochondria-dependent apoptosis. Mechanisms for the anti-apoptotic response to cAMP likely involve Epac (Exchange protein activated by cAMP), a cAMP-regulated effector that is a guanine nucleotide exchange factor (GEF) for the low molecular weight G-protein, Rap1. Therapeutic approaches that activate PKA-mediated pro-apoptosis or block Epac-mediated anti-apoptotisis may provide a means to enhance cell killing, such as in certain cancers. In contrast, efforts to block PKA or stimulate Epac have the potential to be useful in diseases settings (such as heart failure) associated with cAMP-promoted apoptosis.
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Affiliation(s)
- P A Insel
- Department of Pharmacology, University of California, San Diego, La Jolla, 92093-0636, USA.
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14
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Bhattacharya A, Biswas A, Das PK. Identification of a protein kinase A regulatory subunit from Leishmania having importance in metacyclogenesis through induction of autophagy. Mol Microbiol 2012; 83:548-64. [PMID: 22168343 DOI: 10.1111/j.1365-2958.2011.07950.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
cAMP-mediated responses act as modulators of environmental sensing and cellular differentiation of many kinetoplastidae parasites including Leishmania. Although cAMP synthesizing (adenylate cyclase) and degrading (phosphodiesterase) enzymes have been cloned and characterized from Leishmania, no cAMP-binding effector molecule has yet been identified from this parasite. In this study, a regulatory subunit of cAMP-dependent protein kinase (Ldpkar1), homologous to mammalian class I cAMP-dependent protein kinase regulatory subunit, has been identified from L. donovani. Further characterization suggested possible interaction of LdPKAR1 with PKA catalytic subunits and inhibition of PKA activity. This PKA regulatory subunit is expressed in all life cycle stages and its expression attained maximum level in stationary phase promastigotes, which are biochemically similar to the infective metacyclic promastigotes. Starvation condition, the trigger for metacyclogenesis in the parasite, elevates LdPKAR1 expression and under starvation condition promastigotes overexpressing Ldpkar1 attained metacyclic features earlier than normal cells. Furthermore, Ldpkar1 overexpression accelerates autophagy, a starvation-induced cytological event necessary for metacyclogenesis and amastigote formation. Conditional silencing of Ldpkar1 delays the induction of autophagy in the parasite. The study, for the first time, reports the identification of a functional cAMP-binding effector molecule from Leishmania that may modulate important cytological events affecting metacyclogenesis.
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Cherra SJ, Kulich SM, Uechi G, Balasubramani M, Mountzouris J, Day BW, Chu CT. Regulation of the autophagy protein LC3 by phosphorylation. ACTA ACUST UNITED AC 2010; 190:533-9. [PMID: 20713600 PMCID: PMC2928022 DOI: 10.1083/jcb.201002108] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Macroautophagy is a major catabolic pathway that impacts cell survival, differentiation, tumorigenesis, and neurodegeneration. Although bulk degradation sustains carbon sources during starvation, autophagy contributes to shrinkage of differentiated neuronal processes. Identification of autophagy-related genes has spurred rapid advances in understanding the recruitment of microtubule-associated protein 1 light chain 3 (LC3) in autophagy induction, although braking mechanisms remain less understood. Using mass spectrometry, we identified a direct protein kinase A (PKA) phosphorylation site on LC3 that regulates its participation in autophagy. Both metabolic (rapamycin) and pathological (MPP(+)) inducers of autophagy caused dephosphorylation of endogenous LC3. The pseudophosphorylated LC3 mutant showed reduced recruitment to autophagosomes, whereas the nonphosphorylatable mutant exhibited enhanced puncta formation. Finally, autophagy-dependent neurite shortening induced by expression of a Parkinson disease-associated G2019S mutation in leucine-rich repeat kinase 2 was inhibited by dibutyryl-cyclic adenosine monophosphate, cytoplasmic expression of the PKA catalytic subunit, or the LC3 phosphorylation mimic. These data demonstrate a role for phosphorylation in regulating LC3 activity.
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Affiliation(s)
- Salvatore J Cherra
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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16
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Novel targets for Huntington's disease in an mTOR-independent autophagy pathway. Nat Chem Biol 2008; 4:295-305. [PMID: 18391949 DOI: 10.1038/nchembio.79] [Citation(s) in RCA: 622] [Impact Index Per Article: 38.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 02/07/2008] [Indexed: 01/23/2023]
Abstract
Autophagy is a major clearance route for intracellular aggregate-prone proteins causing diseases such as Huntington's disease. Autophagy induction with the mTOR inhibitor rapamycin accelerates clearance of these toxic substrates. As rapamycin has nontrivial side effects, we screened FDA-approved drugs to identify new autophagy-inducing pathways. We found that L-type Ca2+ channel antagonists, the K+ATP channel opener minoxidil, and the G(i) signaling activator clonidine induce autophagy. These drugs revealed a cyclical mTOR-independent pathway regulating autophagy, in which cAMP regulates IP3 levels, influencing calpain activity, which completes the cycle by cleaving and activating G(s)alpha, which regulates cAMP levels. This pathway has numerous potential points where autophagy can be induced, and we provide proof of principle for therapeutic relevance in Huntington's disease using mammalian cell, fly and zebrafish models. Our data also suggest that insults that elevate intracytosolic Ca2+ (like excitotoxicity) inhibit autophagy, thus retarding clearance of aggregate-prone proteins.
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Wojtal KA, Hoekstra D, van Ijzendoorn SCD. cAMP-dependent protein kinase A and the dynamics of epithelial cell surface domains: moving membranes to keep in shape. Bioessays 2008; 30:146-55. [PMID: 18200529 DOI: 10.1002/bies.20705] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) and cAMP-dependent protein kinase A (PKA) are evolutionary conserved molecules with a well-established position in the complex network of signal transduction pathways. cAMP/PKA-mediated signaling pathways are implicated in many biological processes that cooperate in organ development including the motility, survival, proliferation and differentiation of epithelial cells. Cell surface polarity, here defined as the anisotropic organisation of cellular membranes, is a critical parameter for most of these processes. Changes in the activity of cAMP/PKA elicit a variety of effects on intracellular membrane dynamics, including membrane sorting and trafficking. One of the most intriguing aspects of cAMP/PKA signaling is its evolutionary conserved abundance on the one hand and its precise spatial-temporal actions on the other. Here, we review recent developments with regard to the role of cAMP/PKA in the regulation of intracellular membrane trafficking in relation to the dynamics of epithelial surface domains.
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Affiliation(s)
- Kacper A Wojtal
- Division of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
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18
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Abstract
H89 is marketed as a selective and potent inhibitor of protein kinase A (PKA). Since its discovery, it has been used extensively for evaluation of the role of PKA in the heart, osteoblasts, hepatocytes, smooth muscle cells, neuronal tissue, epithelial cells, etc. Despite the frequent use of H89, its mode of specific inhibition of PKA is still not completely understood. It has also been shown that H89 inhibits at least 8 other kinases, while having a relatively large number of PKA-independent effects which may seriously compromise interpretation of data. Thus, while recognizing its kinase inhibiting properties, it is advised that H89 should not be used as the single source of evidence of PKA involvement. H-89 should be used in conjunction with other PKA inhibitors, such as Rp-cAMPS or PKA analogs.
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Affiliation(s)
- A Lochner
- Dept. Biomedical Sciences, Faculty of Health Sciences, University of Stellenbosch, Tygerberg, South Africa
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Shenoy AR, Visweswariah SS. New messages from old messengers: cAMP and mycobacteria. Trends Microbiol 2006; 14:543-50. [PMID: 17055275 DOI: 10.1016/j.tim.2006.10.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 09/07/2006] [Accepted: 10/10/2006] [Indexed: 12/18/2022]
Abstract
Cyclic nucleotides are ancient second messengers, and the enzymes that synthesize cAMP and cGMP [cyclic nucleotide monophosphates (cNMPs)] are encoded in the genomes of several bacteria. We focus here on recent biochemical and structural information on the proteins that make and break cyclic nucleotides in mycobacteria, namely the nucleotide cyclases and phosphodiesterases, respectively. The presence of these enzymes along with putative cNMP-binding proteins suggests an intricate regulation of cAMP metabolism and utilization by these organisms. It is anticipated that future research will be directed towards identifying cellular processes that are regulated by cAMP in mycobacteria and deciphering the cross-talk between mycobacterial pathogens and their eukaryotic host.
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Affiliation(s)
- Avinash R Shenoy
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
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Kotoulas OB, Kalamidas SA, Kondomerkos DJ. Glycogen autophagy in glucose homeostasis. Pathol Res Pract 2006; 202:631-8. [PMID: 16781826 DOI: 10.1016/j.prp.2006.04.001] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
Glycogen autophagy, the sequestration and degradation of cell glycogen in the autophagic vacuoles, is a selective, hormonally controlled and highly regulated process, representing a mechanism of glucose homeostasis under conditions of demand for the production of this sugar. In the newborn animals, this process is induced by glucagon secreted during the postnatal hypoglycemia and inhibited by insulin and parenteral glucose, which abolishes glucagon secretion. Hormonal action is mediated by the cAMP/protein kinase A (induction) and phosphoinositides/mTOR (inhibition) pathways that converge on common targets, such as the protein phosphatase 2A to regulate autophgosomal glycogen-hydrolyzing acid glucosidase and glycogen autophagy. Intralysosomal phosphate exchange reactions, which are affected by changes in the calcium levels and acid mannose 6- and acid glucose 6-phosphatase activities, can modify the intralysosomal composition in phosphorylated and nonphosphorylated glucose and promote the exit of free glucose through the lysosomal membrane. Glycogen autophagy-derived nonphosphorylated glucose assists the hyaloplasmic glycogen degradation-derived glucose 6-phosphate to combat postnatal hypoglycemia and participates in other metabolic pathways to secure the fine tuning of glucose homeostasis during the neonatal period.
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Affiliation(s)
- O B Kotoulas
- Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, Ioannina, Greece.
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21
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Samari H, Møller M, Holden L, Asmyhr T, Seglen P. Stimulation of hepatocytic AMP-activated protein kinase by okadaic acid and other autophagy-suppressive toxins. Biochem J 2005; 386:237-44. [PMID: 15461583 PMCID: PMC1134787 DOI: 10.1042/bj20040609] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Autophagic activity in isolated rat hepatocytes is strongly suppressed by OA (okadaic acid) and other PP (protein phosphatase)-inhibitory toxins as well as by AICAR (5-aminoimidazole-4-carboxamide riboside), a direct activator of AMPK (AMP-activated protein kinase). To investigate whether AMPK is a mediator of the effects of the toxin, a phosphospecific antibody directed against the activation of phosphorylation of the AMPK alpha (catalytic)-subunit at Thr172 was used to assess the activation status of this enzyme. AICAR as well as all the toxins tested (OA, microcystin-LR, calyculin A, cantharidin and tautomycin) induced strong, dose-dependent AMPKalpha phosphorylation, correlating with AMPK activity in situ (in intact hepatocytes) as measured by the AMPK-dependent phosphorylation of acetyl-CoA carboxylase at Ser79. All treatments induced the appearance of multiple, phosphatase-sensitive, low-mobility forms of the AMPK alpha-subunit, consistent with phosphorylation at several sites other than Thr172. The flavonoid naringin, an effective antagonist of OA-induced autophagy suppression, inhibited the AMPK phosphorylation and mobility shifting induced by AICAR, OA or microcystin, but not the changes induced by calyculin A or cantharidin. AMPK may thus be activated both by a naringin-sensitive and a naringin-resistant mechanism, probably involving the PPs PP2A and PP1 respectively. Neither the Thr172-phosphorylating protein kinase LKB1 nor the Thr172-dephosphorylating PP, PP2C, were mobility-shifted after treatment with toxins or AICAR, whereas a slight mobility shifting of the regulatory AMPK beta-subunit was indicated. Immunoblotting with a phosphospecific antibody against pSer108 at the beta-subunit revealed a naringin-sensitive phosphorylation induced by OA, microcystin and AICAR and a naringin-resistant phosphorylation induced by calyculin A and cantharidin, suggesting that beta-subunit phosphorylation could play a role in AMPK activation. Naringin antagonized the autophagy-suppressive effects of AICAR and OA, but not the autophagy suppression caused by cantharidin, consistent with AMPK-mediated inhibition of autophagy by toxins as well as by AICAR.
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Affiliation(s)
- Hamid R. Samari
- Proteomics and Mammalian Cell Biology Section, Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
| | - Michael T. N. Møller
- Proteomics and Mammalian Cell Biology Section, Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
| | - Lise Holden
- Proteomics and Mammalian Cell Biology Section, Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
| | - Tonje Asmyhr
- Proteomics and Mammalian Cell Biology Section, Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
| | - Per O. Seglen
- Proteomics and Mammalian Cell Biology Section, Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
- To whom correspondence should be addressed (email )
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Canu N, Tufi R, Serafino AL, Amadoro G, Ciotti MT, Calissano P. Role of the autophagic-lysosomal system on low potassium-induced apoptosis in cultured cerebellar granule cells. J Neurochem 2005; 92:1228-42. [PMID: 15715672 DOI: 10.1111/j.1471-4159.2004.02956.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Apoptotic and autophagic cell death have been implicated, on the basis of morphological and biochemical criteria, in neuronal loss occurring in neurodegenerative diseases and it has been shown that they may overlap. We have studied the relationship between apoptosis and autophagic cell death in cerebellar granule cells (CGCs) undergoing apoptosis following serum and potassium deprivation. We found that apoptosis is accompanied by an early and marked proliferation of autophagosomal-lysosomal compartments as detected by electron microscopy and immunofluorescence analysis. Autophagy is blocked by hrIGF-1 and forskolin, two well-known inhibitors of CGC apoptosis, as well as by adenovirus-mediated overexpression of Bcl-2. 3-Methyladenine (3-MA) an inhibitor of autophagy, not only arrests this event but it also blocks apoptosis. The neuroprotective effect of 3-MA is accompanied by block of cytochrome c (cyt c) release in the cytosol and by inhibition of caspase-3 activation which, in turn, appears to be mediated by cathepsin B, as CA074-Me, a selective inhibitor of this enzyme, fully blocks the processing of pro-caspase-3. Immunofluorescence analysis demonstrated that cathepsin B, normally confined inside the lysosomal-endosomal compartment, is released during apoptosis into the cytosol where this enzyme may act as an execution protease. Collectively, these observations indicate that autophagy precedes and is causally connected with the subsequent onset of programmed death.
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Affiliation(s)
- Nadia Canu
- Dipartimento di Neuroscienze, Facoltà di Medicina e Chirurgia, Università di Tor Vergata, Roma, Italia.
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Kalamidas SA, Kondomerkos DJ, Kotoulas OB, Hann AC. Electron microscopic and biochemical study of the effects of rapamycin on glycogen autophagy in the newborn rat liver. Microsc Res Tech 2004; 63:215-9. [PMID: 14988919 DOI: 10.1002/jemt.20032] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The effects of rapamycin on glycogen autophagy in the newborn rat liver were studied using biochemical determinations, electron microscopy, and morphometric analysis. Rapamycin increased the fractional volume of hepatocytic autophagic vacuoles, the liver lysosomal glycogen-hydrolyzing activity of acid glucosidase, the degradation of glycogen inside the autophagic vacuoles, and decreased the activity of acid mannose 6-phosphatase. These findings suggest that rapamycin, a known inhibitor of the mammalian target of rapamycin (mTOR) signaling, induces glycogen autophagy in the newborn rat hepatocytes. mTOR may participate in the regulation of this process.
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Affiliation(s)
- S A Kalamidas
- Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, Ioannina, Greece.
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24
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 order by 1-- trpx] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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25
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26
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27
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 6346=6346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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28
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29
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and (select 4137 from (select(sleep(5)))vhil)] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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31
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 waitfor delay '0:0:5'-- cijg] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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33
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34
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 7792=3000-- onwj] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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35
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 waitfor delay '0:0:5'] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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36
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 order by 1-- uxyn] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 8039=(select 8039 from pg_sleep(5))-- yprg] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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40
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 3687=2098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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44
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 6346=6346-- zrnx] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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45
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Levine B, Klionsky DJ. Development by Self-Digestion. Dev Cell 2004. [DOI: 10.1016/s1534-5807(04)00099-1 and 8039=(select 8039 from pg_sleep(5))] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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46
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Abstract
Autophagy is the major cellular pathway for the degradation of long-lived proteins and cytoplasmic organelles. It involves the rearrangement of subcellular membranes to sequester cargo for delivery to the lysosome where the sequestered material is degraded and recycled. For many decades, it has been known that autophagy occurs in a wide range of eukaryotic organisms and in multiple different cell types during starvation, cellular and tissue remodeling, and cell death. However, until recently, the functions of autophagy in normal development were largely unknown. The identification of a set of evolutionarily conserved genes that are essential for autophagy has opened up new frontiers for deciphering the role of autophagy in diverse biological processes. In this review, we summarize our current knowledge about the molecular machinery of autophagy and the role of the autophagic machinery in eukaryotic development.
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Affiliation(s)
- Beth Levine
- Department of Medicine, Columbia University, New York, NY 10032, USA.
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47
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Kondomerkos DJ, Kalamidas SA, Kotoulas OB. An electron microscopic and biochemical study of the effects of glucagon on glycogen autophagy in the liver and heart of newborn rats. Microsc Res Tech 2004; 63:87-93. [PMID: 14722905 DOI: 10.1002/jemt.20000] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The effects of glucagon on the ultrastructural appearance and acid glucosidase activities in the liver and heart of newborn rats were studied. Liver or heart glycogen-hydrolyzing activity of acid glucosidase increased 3 hours after birth and gradually decreased from 3 to 9 hours. Maltose-hydrolyzing activity of acid glucosidase also rose 3 hours after birth, maintained a plateau between 3 and 6 hours, and fell at 9 hours. The administration of glucagon increased autophagic activity in the hepatocytes at the age of 6 hours. Glycogen inside the autophagic vacuoles was decreased, apparently due to the increased glycogen degradation. Glycogen-hydrolyzing activity was elevated in both the liver and the heart. Maltose-hydrolyzing activity was elevated in the liver, but not in the heart. The results of this study suggest that the glycogen-hydrolyzing and maltose-hydrolyzing activities of acid glucosidase are due to different enzymes. Glucagon's effect on the glycogen-hydrolyzing acid glucosidase activity and autophagosomal morphology is similar in both the liver and the heart.
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Affiliation(s)
- D J Kondomerkos
- Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, 45110 Ioannina, Greece.
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48
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Abstract
Glycogen autophagy, which includes the sequestration and degradation of cell glycogen in the autophagic vacuoles, is a selective process under conditions of demand for the massive hepatic production of glucose, as in the postnatal period. It represents a link between autophagy and glycogen metabolism. The formation of autophagic vacuoles in the hepatocytes of newborn animals is spatially and biochemically related to the degradation of cell glycogen. Many molecular elements and signaling pathways including the cyclic AMP/cyclic AMP-dependent protein kinase and the phosphoinositides/TOR pathways are implicated in the control of this process. These two pathways may converge on the same target to regulate glycogen autophagy.
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Affiliation(s)
- Othon B Kotoulas
- Department of Anatomy, Histology and Embryology, Medical School, University of Ioannina, Ioannina 451 10, Greece.
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49
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Møller MTN, Samari HR, Fengsrud M, Strømhaug PE, øStvold AC, Seglen PO. Okadaic acid-induced, naringin-sensitive phosphorylation of glycine N-methyltransferase in isolated rat hepatocytes. Biochem J 2003; 373:505-13. [PMID: 12697024 PMCID: PMC1223502 DOI: 10.1042/bj20030502] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2003] [Revised: 04/15/2003] [Accepted: 04/16/2003] [Indexed: 11/17/2022]
Abstract
Glycine N-methyltransferase (GNMT) is an abundant cytosolic enzyme that catalyses the methylation of glycine into sarcosine, coupled with conversion of the methyl donor, S -adenosylmethionine (AdoMet), into S -adenosylhomocysteine (AdoHcy). GNMT is believed to play a role in monitoring the AdoMet/AdoHcy ratio, and hence the cellular methylation capacity, but regulation of the enzyme itself is not well understood. In the present study, treatment of isolated rat hepatocytes with the protein phosphatase inhibitor okadaic acid, was found to induce an overphosphorylation of GNMT, as shown by proteomic analysis. The analysis comprised two-dimensional gel electrophoretic separation of (32)P-labelled phosphoproteins and identification of individual protein spots by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry. The identity of GNMT was verified by N-terminal Edman sequencing of tryptic peptides. Chromatographic separation of proteolytic peptides and (32)P-labelled amino acids suggested that GNMT was phosphorylated within a limited region, and only at serine residues. GNMT phosphorylation could be suppressed by naringin, an okadaic acid-antagonistic flavonoid. To assess the possible functional role of GNMT phosphorylation, the effect of okadaic acid on hepatocytic AdoMet and AdoHcy levels was examined, using HPLC separation for metabolite analysis. Surprisingly, okadaic acid was found to have no effect on the basal levels of AdoMet or AdoHcy. An accelerated AdoMet-AdoHcy flux, induced by the addition of methionine (1 mM), was likewise unaffected by okadaic acid. 5-Aminoimidazole-4-carboxamide riboside, an activator of the hepatocytic AMP-activated protein kinase, similarly induced GNMT phosphorylation without affecting AdoMet and AdoHcy levels. Activation of cAMP-dependent protein kinase by dibutyryl-cAMP, reported to cause GNMT phosphorylation under cell-free conditions, also had little effect on hepatocytic AdoMet and AdoHcy levels. Phosphorylation of GNMT would thus seem to play no role in regulation of the intracellular AdoMet/AdoHcy ratio, but could be involved in other GNMT functions, such as the binding of folates or aromatic hydrocarbons.
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Affiliation(s)
- Michael T N Møller
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway
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50
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Ogier-Denis E, Codogno P. Autophagy: a barrier or an adaptive response to cancer. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1603:113-28. [PMID: 12618311 DOI: 10.1016/s0304-419x(03)00004-0] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Macroautophagy or autophagy is a degradative pathway terminating in the lysosomal compartment after the formation of a cytoplasmic vacuole that engulfs macromolecules and organelles. The recent discovery of the molecular controls of autophagy that are common to eukaryotic cells from yeast to human suggests that the role of autophagy in cell functioning is far beyond its nonselective degradative capacity. The involvement of proteins with properties of tumor suppressor and oncogenic properties at different steps of the pathway implies that autophagy must be considered in tumor progression. Autophagy as a stress response mechanism protects cancer cells from low nutrient supply or therapeutic insults. Autophagy is also involved in the elimination of cancer cells by triggering a non-apoptotic cell death program, suggesting a negative role in tumor development. These two aspects of autophagy will be discussed in this review.
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Affiliation(s)
- Eric Ogier-Denis
- INSERM U504 Glycobiologie et Signalisation cellulaire, Institut André Lwoff, 16 avenue Paul-Vaillant-Couturier, 94807 Villejuif Cedex, France
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