Publications by authors named "Maria Markaki"

31 Publications

Autophagy mechanisms and roles: recent advances and implications.

FEBS J 2020 12 22;287(23):5024-5026. Epub 2020 Oct 22.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece.

Autophagy is the main catabolic process by which cells recycle cytoplasmic components and superfluous or damaged organelles to preserve metabolic homeostasis under normal conditions and promote survival under stress. As a tightly regulated and dynamic process, autophagy has critical roles in development and cell differentiation, immune function, organismal health and lifespan. Accumulating findings suggest that defective or dysregulated autophagy accelerates ageing and increases susceptibility to diseases, such as neurodegenerative disorders and cancer, among others. This virtual issue of the FEBS Journal on Autophagy includes a collection of articles that present recent advances on the regulation of autophagy and provide a view of its complex roles in physiological and pathological contexts.
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http://dx.doi.org/10.1111/febs.15573DOI Listing
December 2020

Editorial: Mitophagy in physiology and pathology.

Mech Ageing Dev 2020 09 20;190:111291. Epub 2020 Jun 20.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, 70013, Crete, Greece; Department of Basic Sciences, School of Medicine, University of Crete, Heraklion, 70013, Crete, Greece. Electronic address:

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http://dx.doi.org/10.1016/j.mad.2020.111291DOI Listing
September 2020

Mitochondrial turnover and homeostasis in ageing and neurodegeneration.

FEBS Lett 2020 08 1;594(15):2370-2379. Epub 2020 Jun 1.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.

Ageing is driven by the inexorable and stochastic accumulation of damage in biomolecules vital for proper cellular function. Although this process is fundamentally haphazard and uncontrollable, genetic and extrinsic factors influence senescent decline and ageing. Numerous gene mutations and treatments have been shown to extend the lifespan of organisms ranging from the unicellular Saccharomyces cerevisiae to primates. Most such interventions ultimately interface with cellular stress response mechanisms, suggesting that longevity is intimately related to the ability of the organism to counter both intrinsic stress and extrinsic stress. Mitochondria, the main energy hub of the cell, are highly dynamic organelles, playing essential roles in cell physiology. Mitochondrial function impinges on several signalling pathways modulating cellular metabolism, survival and healthspan. Maintenance of mitochondrial function and energy homeostasis requires both generation of new healthy mitochondria and elimination of the dysfunctional ones. Here, we survey the mechanisms regulating mitochondrial number in cells, with particular emphasis on neurons. We, further, discuss recent findings implicating perturbation of mitochondrial homeostasis in cellular senescence and organismal ageing as well as in age-associated neurodegenerative diseases.
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http://dx.doi.org/10.1002/1873-3468.13802DOI Listing
August 2020

Caenorhabditis elegans as a model system for human diseases.

Curr Opin Biotechnol 2020 06 14;63:118-125. Epub 2020 Jan 14.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion 70013, Crete, Greece; Department of Basic Sciences, School of Medicine, University of Crete, Heraklion 70013, Crete, Greece. Electronic address:

The nematode Caenorhabditis elegans offers unique advantages that enable a comprehensive delineation of the cellular and molecular mechanisms underlying devastating human pathologies such as stroke, ischemia and age-associated neurodegenerative disorders. Genetic models of human diseases that closely simulate several disease-related phenotypes have been established in the worm. These models allow the implementation of multidisciplinary approaches, in addition to large-scale genetic and pharmacological screenings, designed to elucidate the molecular mechanisms mediating pathogenesis and to identify targets and drugs for emergent therapeutic interventions. Such strategies have already provided valuable insights, highly relevant to human health and quality of life. This article considers the potential of C. elegans as a versatile platform for systematic dissection of the molecular basis of human disease, focusing on neurodegenerative disorders.
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http://dx.doi.org/10.1016/j.copbio.2019.12.011DOI Listing
June 2020

'Reduced' HUNT model outperforms NLST and NELSON study criteria in predicting lung cancer in the Danish screening trial.

BMJ Open Respir Res 2019 11;6(1):e000512. Epub 2019 Nov 11.

Department of Respiratory Medicine, Gentofte University Hospital, Hellerup, Denmark.

Hypothesis: We hypothesise that the validated HUNT Lung Cancer Risk Model would perform better than the NLST (USA) and the NELSON (Dutch-Belgian) criteria in the Danish Lung Cancer Screening Trial (DLCST).

Methods: The DLCST measured only five out of the seven variables included in validated HUNT Lung Cancer Model. Therefore a 'Reduced' model was retrained in the Norwegian HUNT2-cohort using the same statistical methodology as in the original HUNT model but based only on age, pack years, smoking intensity, quit time and body mass index (BMI), adjusted for sex. The model was applied on the DLCST-cohort and contrasted against the NLST and NELSON criteria.

Results: Among the 4051 smokers in the DLCST with 10 years follow-up, median age was 57.6, BMI 24.75, pack years 33.8, cigarettes per day 20 and most were current smokers. For the same number of individuals selected for screening, the performance of the 'Reduced' HUNT was increased in all metrics compared with both the NLST and the NELSON criteria. In addition, to achieve the same sensitivity, one would need to screen fewer people by the 'Reduced' HUNT model versus using either the NLST or the NELSON criteria (709 vs 918, p=1.02e-11 and 1317 vs 1668, p=2.2e-16, respectively).

Conclusions: The 'Reduced' HUNT model is superior in predicting lung cancer to both the NLST and NELSON criteria in a cost-effective way. This study supports the use of the HUNT Lung Cancer Model for selection based on risk ranking rather than age, pack year and quit time cut-off values. When we know how to rank personal risk, it will be up to the medical community and lawmakers to decide which risk threshold will be set for screening.
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http://dx.doi.org/10.1136/bmjresp-2019-000512DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6890385PMC
July 2020

3,4-Dimethoxychalcone induces autophagy through activation of the transcription factors TFE3 and TFEB.

EMBO Mol Med 2019 11 14;11(11):e10469. Epub 2019 Oct 14.

Gustave Roussy Cancer Campus, Villejuif, France.

Caloric restriction mimetics (CRMs) are natural or synthetic compounds that mimic the health-promoting and longevity-extending effects of caloric restriction. CRMs provoke the deacetylation of cellular proteins coupled to an increase in autophagic flux in the absence of toxicity. Here, we report the identification of a novel candidate CRM, namely 3,4-dimethoxychalcone (3,4-DC), among a library of polyphenols. When added to several different human cell lines, 3,4-DC induced the deacetylation of cytoplasmic proteins and stimulated autophagic flux. At difference with other well-characterized CRMs, 3,4-DC, however, required transcription factor EB (TFEB)- and E3 (TFE3)-dependent gene transcription and mRNA translation to trigger autophagy. 3,4-DC stimulated the translocation of TFEB and TFE3 into nuclei both in vitro and in vivo, in hepatocytes and cardiomyocytes. 3,4-DC induced autophagy in vitro and in mouse organs, mediated autophagy-dependent cardioprotective effects, and improved the efficacy of anticancer chemotherapy in vivo. Altogether, our results suggest that 3,4-DC is a novel CRM with a previously unrecognized mode of action.
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http://dx.doi.org/10.15252/emmm.201910469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835206PMC
November 2019

Emerging Roles of Lipophagy in Health and Disease.

Front Cell Dev Biol 2019 10;7:185. Epub 2019 Sep 10.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion, Greece.

The term lipophagy is used to describe the autophagic degradation of lipid droplets, the main lipid storage organelles of eukaryotic cells. Ever since its discovery in 2009, lipophagy has emerged as a significant component of lipid metabolism with important implications for organismal health. This review aims to provide a brief summary of our current knowledge on the mechanisms that are responsible for regulating lipophagy and the impact the process has under physiological and pathological conditions.
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http://dx.doi.org/10.3389/fcell.2019.00185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746960PMC
September 2019

Maintenance of Proteostasis by P Body-Mediated Regulation of eIF4E Availability during Aging in Caenorhabditis elegans.

Cell Rep 2018 10;25(1):199-211.e6

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion 71110, Greece; Department of Basic Sciences, School of Medicine, University of Crete, Heraklion 71110, Greece. Electronic address:

Aging is accompanied by a pervasive collapse of proteostasis, while reducing general protein synthesis promotes longevity across taxa. Here, we show that the eIF4E isoform IFE-2 is increasingly sequestered in mRNA processing (P) bodies during aging and upon stress in Caenorhabditis elegans. Loss of the enhancer of mRNA decapping EDC-3 causes further entrapment of IFE-2 in P bodies and lowers protein synthesis rates in somatic tissues. Animals lacking EDC-3 are long lived and stress resistant, congruent with IFE-2-deficient mutants. Notably, neuron-specific expression of EDC-3 is sufficient to reverse lifespan extension, while sequestration of IFE-2 in neuronal P bodies counteracts age-related neuronal decline. The effects of mRNA decapping deficiency on stress resistance and longevity are orchestrated by a multimodal stress response involving the transcription factor SKN-1, which mediates lifespan extension upon reduced protein synthesis. Our findings elucidate a mechanism of proteostasis control during aging through P body-mediated regulation of protein synthesis in the soma.
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http://dx.doi.org/10.1016/j.celrep.2018.09.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180348PMC
October 2018

Novel Insights Into the Anti-aging Role of Mitophagy.

Int Rev Cell Mol Biol 2018 20;340:169-208. Epub 2018 Jun 20.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas; Department of Basic Sciences, Medical School, University of Crete, Heraklion, Greece.

Aging is a complex biological process affecting almost all living organisms. Although its detrimental effects on animals' physiology have been extensively documented, several aspects of the biology of aging are insufficiently understood. Mitochondria, the central energy producers of the cell, play vital roles in a wide range of cellular processes, including regulation of bioenergetics, calcium signaling, metabolic responses, and cell death, among others. Thus, proper mitochondrial function is a prerequisite for the maintenance of cellular and organismal homeostasis. Several mitochondrial quality control mechanisms have evolved to allow adaptation to different metabolic conditions, thereby preserving cellular homeostasis and survival. A tight coordination between mitochondrial biogenesis and mitochondrial selective autophagy, known as mitophagy, is a common characteristic of healthy biological systems. The balanced interplay between these two opposing cellular processes dictates stress resistance, healthspan, and lifespan extension. Mitochondrial biogenesis and mitophagy efficiency decline with age, leading to progressive accumulation of damaged and/or unwanted mitochondria, deterioration of cellular function, and ultimately death. Several regulatory factors that contribute to energy homeostasis have been implicated in the development and progression of many pathological conditions, such as neurodegenerative, metabolic, and cardiovascular disorders, among others. Therefore, mitophagy modulation may serve as a novel potential therapeutic approach to tackle age-associated pathologies. Here, we review the molecular signaling pathways that regulate and coordinate mitophagy with mitochondrial biogenesis, highlighting critical factors that hold promise for the development of pharmacological interventions toward enhancing human health and quality of life throughout aging.
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http://dx.doi.org/10.1016/bs.ircmb.2018.05.005DOI Listing
April 2019

A Validated Clinical Risk Prediction Model for Lung Cancer in Smokers of All Ages and Exposure Types: A HUNT Study.

EBioMedicine 2018 May 30;31:36-46. Epub 2018 Mar 30.

Norwegian University of Science and Technology, Department of Clinical Research and Molecular Medicine, Prinsesse Kristinsgt. 1, Trondheim, NO 7491, Norway; Levanger Hospital, Nord-Trøndelag Hospital Trust, Cancer Clinic, Kirkegata 2, Levanger, NO 7600, Norway; Clinical Cancer Research Center, Department of Clinical Medicine, Hobrovej 18-22, Aalborg, DK 9000, Denmark. Electronic address:

Lung cancer causes >1·6 million deaths annually, with early diagnosis being paramount to effective treatment. Here we present a validated risk assessment model for lung cancer screening. The prospective HUNT2 population study in Norway examined 65,237 people aged >20years in 1995-97. After a median of 15·2years, 583 lung cancer cases had been diagnosed; 552 (94·7%) ever-smokers and 31 (5·3%) never-smokers. We performed multivariable analyses of 36 candidate risk predictors, using multiple imputation of missing data and backwards feature selection with Cox regression. The resulting model was validated in an independent Norwegian prospective dataset of 45,341 ever-smokers, in which 675 lung cancers had been diagnosed after a median follow-up of 11·6years. Our final HUNT Lung Cancer Model included age, pack-years, smoking intensity, years since smoking cessation, body mass index, daily cough, and hours of daily indoors exposure to smoke. External validation showed a 0·879 concordance index (95% CI [0·866-0·891]) with an area under the curve of 0·87 (95% CI [0·85-0·89]) within 6years. Only 22% of ever-smokers would need screening to identify 81·85% of all lung cancers within 6years. Our model of seven variables is simple, accurate, and useful for screening selection.
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http://dx.doi.org/10.1016/j.ebiom.2018.03.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6013755PMC
May 2018

Aspirin Recapitulates Features of Caloric Restriction.

Cell Rep 2018 02;22(9):2395-2407

Gustave Roussy Cancer Campus, Villejuif, France; INSERM, U1138, Paris, France; Equipe 11 labellisée par la Ligue Nationale contre le Cancer, Centre de Recherche des Cordeliers, Paris, France; Université Paris Descartes/Paris V, Sorbonne Paris Cité, Paris, France; Metabolomics and Cell Biology Platforms, Gustave Roussy Cancer Campus, Villejuif, France; Université Pierre et Marie Curie, Paris, France; Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France; Karolinska Institute, Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, Sweden. Electronic address:

The age-associated deterioration in cellular and organismal functions associates with dysregulation of nutrient-sensing pathways and disabled autophagy. The reactivation of autophagic flux may prevent or ameliorate age-related metabolic dysfunctions. Non-toxic compounds endowed with the capacity to reduce the overall levels of protein acetylation and to induce autophagy have been categorized as caloric restriction mimetics (CRMs). Here, we show that aspirin or its active metabolite salicylate induce autophagy by virtue of their capacity to inhibit the acetyltransferase activity of EP300. While salicylate readily stimulates autophagic flux in control cells, it fails to further increase autophagy levels in EP300-deficient cells, as well as in cells in which endogenous EP300 has been replaced by salicylate-resistant EP300 mutants. Accordingly, the pro-autophagic activity of aspirin and salicylate on the nematode Caenorhabditis elegans is lost when the expression of the EP300 ortholog cpb-1 is reduced. Altogether, these findings identify aspirin as an evolutionary conserved CRM.
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http://dx.doi.org/10.1016/j.celrep.2018.02.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5848858PMC
February 2018

MatureP: prediction of secreted proteins with exclusive information from their mature regions.

Sci Rep 2017 06 12;7(1):3263. Epub 2017 Jun 12.

Institute of Molecular Biology and Biotechnology-FORTH and Department of Biology-University of Crete, PO Box 1385, Heraklion, Crete, Greece.

More than a third of the cellular proteome is non-cytoplasmic. Most secretory proteins use the Sec system for export and are targeted to membranes using signal peptides and mature domains. To specifically analyze bacterial mature domain features, we developed MatureP, a classifier that predicts secretory sequences through features exclusively computed from their mature domains. MatureP was trained using Just Add Data Bio, an automated machine learning tool. Mature domains are predicted efficiently with ~92% success, as measured by the Area Under the Receiver Operating Characteristic Curve (AUC). Predictions were validated using experimental datasets of mutated secretory proteins. The features selected by MatureP reveal prominent differences in amino acid content between secreted and cytoplasmic proteins. Amino-terminal mature domain sequences have enhanced disorder, more hydroxyl and polar residues and less hydrophobics. Cytoplasmic proteins have prominent amino-terminal hydrophobic stretches and charged regions downstream. Presumably, secretory mature domains comprise a distinct protein class. They balance properties that promote the necessary flexibility required for the maintenance of non-folded states during targeting and secretion with the ability of post-secretion folding. These findings provide novel insight in protein trafficking, sorting and folding mechanisms and may benefit protein secretion biotechnology.
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http://dx.doi.org/10.1038/s41598-017-03557-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5468347PMC
June 2017

Mitophagy and age-related pathologies: Development of new therapeutics by targeting mitochondrial turnover.

Pharmacol Ther 2017 Oct 29;178:157-174. Epub 2017 Apr 29.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Greece; Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, 70013, Crete, Greece. Electronic address:

Mitochondria are highly dynamic and semi-autonomous organelles, essential for many fundamental cellular processes, including energy production, metabolite synthesis, ion homeostasis, lipid metabolism and initiation of apoptotic cell death. Proper mitochondrial physiology is a prerequisite for health and survival. Generation of new and removal of damaged or unwanted mitochondria are tightly controlled processes that need to be accurately coordinated for the maintenance of mitochondrial and cellular homeostasis. Mitophagy is a conserved, mitochondria-specific autophagic clearance process. An intricate regulatory network balances mitophagy with mitochondrial biogenesis. Proper coordination of these opposing processes is important for stress resistance and longevity. Age-dependent decline of mitophagy both inhibits removal of dysfunctional or superfluous mitochondria and impairs mitochondrial biogenesis resulting in progressive mitochondrial accretion and consequently, deterioration of cell function. Nodal regulatory factors that contribute to mitochondrial homeostasis have been implicated in the pathogenesis of several age-associated pathologies, such as neurodegenerative and cardiovascular disorders and cancer, among others. Thus, mitophagy is emerging as a potential target for therapeutic interventions against diseases associated with ageing. In this review, we survey the molecular mechanisms that govern and interface mitophagy with mitochondrial biogenesis, focusing on key elements that hold promise for the development of pharmacological approaches towards enhancing healthspan and quality of life in the elderly.
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http://dx.doi.org/10.1016/j.pharmthera.2017.04.005DOI Listing
October 2017

Mitochondria, autophagy and age-associated neurodegenerative diseases: New insights into a complex interplay.

Biochim Biophys Acta 2015 Nov 24;1847(11):1412-23. Epub 2015 Apr 24.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece; Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion 70013, Crete, Greece. Electronic address:

Mitochondria represent the major bioenergetic hub coordinating cellular and organismal homeostasis. The underlying causes of many pathologies tormenting humans converge on impaired mitochondrial maintenance. Mitochondria-specific autophagy (mitophagy), a cellular catabolic process targeting mitochondria, holds a prominent role in mitochondrial quality control. In addition to core autophagic machinery components, mitophagy exploits a variety of molecules that identify damaged or superfluous mitochondria and mediate their elimination. Signaling pathways integrating environmental and genetic stimuli interact with key mitophagy effectors to activate cellular stress response mechanisms, ultimately modulating health and lifespan. Here, we review the signaling cascades and molecular mechanisms that govern the process of mitophagy and discuss their involvement in ageing and neurodegeneration. This article is part of a Special Issue entitled: Mitochondrial Dysfunction in Aging.
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http://dx.doi.org/10.1016/j.bbabio.2015.04.010DOI Listing
November 2015

Caenorhabditis elegans as a model for cancer research.

Mol Cell Oncol 2015 Apr-Jun;2(2):e975027. Epub 2014 Dec 1.

Institute of Molecular Biology and Biotechnology; Foundation for Research and Technology-Hellas; Department of Basic Sciences; Faculty of Medicine; University of Crete Heraklion; Crete, Greece.

The term cancer describes a group of multifaceted diseases characterized by an intricate pathophysiology. Despite significant advances in the fight against cancer, it remains a key public health concern and burden on societies worldwide. Elucidation of key molecular and cellular mechanisms of oncogenic diseases will facilitate the development of better intervention strategies to counter or prevent tumor development. In vivo and in vitro models have long been used to delineate distinct biological processes involved in cancer such as apoptosis, proliferation, angiogenesis, invasion, metastasis, genome instability, and metabolism. In this review, we introduce Caenorhabditis elegans as an emerging animal model for systematic dissection of the molecular basis of tumorigenesis, focusing on the well-established processes of apoptosis and autophagy. Additionally, we propose that C. elegans can be used to advance our understanding of cancer progression, such as deregulation of energy metabolism, stem cell reprogramming, and host-microflora interactions.
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http://dx.doi.org/10.4161/23723556.2014.975027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4905018PMC
June 2016

Unsaturated fatty acids induce non-canonical autophagy.

EMBO J 2015 Apr 13;34(8):1025-41. Epub 2015 Jan 13.

Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France INSERM, U1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France Cell Biology & Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France

To obtain mechanistic insights into the cross talk between lipolysis and autophagy, two key metabolic responses to starvation, we screened the autophagy-inducing potential of a panel of fatty acids in human cancer cells. Both saturated and unsaturated fatty acids such as palmitate and oleate, respectively, triggered autophagy, but the underlying molecular mechanisms differed. Oleate, but not palmitate, stimulated an autophagic response that required an intact Golgi apparatus. Conversely, autophagy triggered by palmitate, but not oleate, required AMPK, PKR and JNK1 and involved the activation of the BECN1/PIK3C3 lipid kinase complex. Accordingly, the downregulation of BECN1 and PIK3C3 abolished palmitate-induced, but not oleate-induced, autophagy in human cancer cells. Moreover, Becn1(+/-) mice as well as yeast cells and nematodes lacking the ortholog of human BECN1 mounted an autophagic response to oleate, but not palmitate. Thus, unsaturated fatty acids induce a non-canonical, phylogenetically conserved, autophagic response that in mammalian cells relies on the Golgi apparatus.
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http://dx.doi.org/10.15252/embj.201489363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4406650PMC
April 2015

Spermidine protects against α-synuclein neurotoxicity.

Cell Cycle 2014 ;13(24):3903-8

a Institute of Molecular Biosciences ; University of Graz ; Graz , Austria.

As our society ages, neurodegenerative disorders like Parkinson`s disease (PD) are increasing in pandemic proportions. While mechanistic understanding of PD is advancing, a treatment with well tolerable drugs is still elusive. Here, we show that administration of the naturally occurring polyamine spermidine, which declines continuously during aging in various species, alleviates a series of PD-related degenerative processes in the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans, two established model systems for PD pathology. In the fruit fly, simple feeding with spermidine inhibited loss of climbing activity and early organismal death upon heterologous expression of human α-synuclein, which is thought to be the principal toxic trigger of PD. In this line, administration of spermidine rescued α-synuclein-induced loss of dopaminergic neurons, a hallmark of PD, in nematodes. Alleviation of PD-related neurodegeneration by spermidine was accompanied by induction of autophagy, suggesting that this cytoprotective process may be responsible for the beneficial effects of spermidine administration.
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http://dx.doi.org/10.4161/15384101.2014.973309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614020PMC
September 2015

Endonuclease G mediates α-synuclein cytotoxicity during Parkinson's disease.

EMBO J 2013 Nov 15;32(23):3041-54. Epub 2013 Oct 15.

1] Institute of Molecular Biosciences, University of Graz, Graz, Austria [2] Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.

Malfunctioning of the protein α-synuclein is critically involved in the demise of dopaminergic neurons relevant to Parkinson's disease. Nonetheless, the precise mechanisms explaining this pathogenic neuronal cell death remain elusive. Endonuclease G (EndoG) is a mitochondrially localized nuclease that triggers DNA degradation and cell death upon translocation from mitochondria to the nucleus. Here, we show that EndoG displays cytotoxic nuclear localization in dopaminergic neurons of human Parkinson-diseased patients, while EndoG depletion largely reduces α-synuclein-induced cell death in human neuroblastoma cells. Xenogenic expression of human α-synuclein in yeast cells triggers mitochondria-nuclear translocation of EndoG and EndoG-mediated DNA degradation through a mechanism that requires a functional kynurenine pathway and the permeability transition pore. In nematodes and flies, EndoG is essential for the α-synuclein-driven degeneration of dopaminergic neurons. Moreover, the locomotion and survival of α-synuclein-expressing flies is compromised, but reinstalled by parallel depletion of EndoG. In sum, we unravel a phylogenetically conserved pathway that involves EndoG as a critical downstream executor of α-synuclein cytotoxicity.
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http://dx.doi.org/10.1038/emboj.2013.228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3844953PMC
November 2013

Imidacloprid does not induce Cyp genes involved in insecticide resistance of a mutant Drosophila melanogaster line.

Food Chem Toxicol 2013 Oct 7;60:355-9. Epub 2013 Aug 7.

Institute for Biological Research, University of Belgrade, 142 Despot Stefan Blvd., 11060 Belgrade, Serbia; Medical School, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece. Electronic address:

Certain xenobiotics have the capacity to induce the expression of genes involved in various biological phenomena, including insecticide resistance. The induction potential of different chemicals, among them different insecticides, has been documented for a number of insect species. In this study, we have analyzed the induction potential of Imidacloprid, a widely used member of the neonicotinoid insecticide family. Genes Cyp6g1 and Cyp6a2, known to be involved in the resistance of mutant Drosophila melanogaster line MiT[W⁻]3R2 to Imidacloprid and DDT were included in the analyzed sample. We find that Imidacloprid does not induce expression of the analyzed genes.
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http://dx.doi.org/10.1016/j.fct.2013.07.080DOI Listing
October 2013

The nucleotide-binding proteins Nubp1 and Nubp2 are negative regulators of ciliogenesis.

Cell Mol Life Sci 2014 Feb 27;71(3):517-38. Epub 2013 Jun 27.

Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus.

Nucleotide-binding proteins Nubp1 and Nubp2 are MRP/MinD-type P-loop NTPases with sequence similarity to bacterial division site-determining proteins and are conserved, essential proteins throughout the Eukaryotes. They have been implicated, together with their interacting minus-end directed motor protein KIFC5A, in the regulation of centriole duplication in mammalian cells. Here we show that Nubp1 and Nubp2 are integral components of centrioles throughout the cell cycle, recruited independently of KIFC5A. We further demonstrate their localization at the basal body of the primary cilium in quiescent vertebrate cells or invertebrate sensory cilia, as well as in the motile cilia of mouse cells and in the flagella of Chlamydomonas. RNAi-mediated silencing of nubp-1 in C. elegans causes the formation of morphologically aberrant and additional cilia in sensory neurons. Correspondingly, downregulation of Nubp1 or Nubp2 in mouse quiescent NIH 3T3 cells markedly increases the number of ciliated cells, while knockdown of KIFC5A dramatically reduces ciliogenesis. Simultaneous double silencing of Nubp1 + KIFC5A restores the percentage of ciliated cells to control levels. We document the normal ciliary recruitment, during these silencing regimes, of basal body proteins critical for ciliogenesis, namely CP110, CEP290, cenexin, Chibby, AurA, Rab8, and BBS7. Interestingly, we uncover novel interactions of Nubp1 with several members of the CCT/TRiC molecular chaperone complex, which we find enriched at the basal body and recruited independently of the Nubps or KIFC5A. Our combined results for Nubp1, Nubp2, and KIFC5A and their striking effects on cilium formation suggest a central regulatory role for these proteins, likely involving CCT/TRiC chaperone activity, in ciliogenesis.
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http://dx.doi.org/10.1007/s00018-013-1401-6DOI Listing
February 2014

Crosstalk between apoptosis, necrosis and autophagy.

Biochim Biophys Acta 2013 Dec 13;1833(12):3448-3459. Epub 2013 Jun 13.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion 71110, Crete, Greece. Electronic address:

Apoptosis and necrosis are the two major modes of cell death, the molecular mechanisms of which have been extensively studied. Although initially thought to constitute mutually exclusive cellular states, recent findings reveal cellular contexts that require a balanced interplay between these two modes of cellular demise. Several death initiator and effector molecules, signaling pathways and subcellular sites have been identified as key mediators in both processes, either by constituting common modules or alternatively by functioning as a switch allowing cells to decide which route to take, depending on the specific situation. Importantly, autophagy, which is a predominantly cytoprotective process, has been linked to both types of cell death, serving either a pro-survival or pro-death function. Here we review the recent literature that highlights the intricate interplay between apoptosis, necrosis and autophagy, focusing on the relevance and impact of this crosstalk in normal development and in pathology. This article is part of a Special Section entitled: Cell Death Pathways.
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http://dx.doi.org/10.1016/j.bbamcr.2013.06.001DOI Listing
December 2013

Metabolic control by target of rapamycin and autophagy during ageing - a mini-review.

Gerontology 2013 9;59(4):340-8. Epub 2013 Apr 9.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion, Greece.

The conserved target of rapamycin (TOR) pathway integrates signals from nutrient and energy availability, growth factors and stress to regulate cell growth and proliferation, development and metabolism. Growing evidence suggests that TOR signalling controls the rate at which cells and tissues age, thereby contributing to whole-organism ageing. Although significant progress has been made in the last decades towards understanding fundamental aspects of the ageing process, the precise mechanisms underlying the age-related effects of TOR are still not fully understood. TOR interfaces with several cellular processes, such as DNA transcription, mRNA translation, protein turnover and autophagy, among others. Interestingly, TOR regulates various aspects of metabolism including mitochondrial function and lipid metabolism. Inhibition of TOR activity stimulates autophagy, a conserved lysosomal catabolic pathway that controls the degradation and turnover of macromolecules and organelles. Autophagy also has an important role in maintaining metabolic homeostasis at both the cellular and whole-organism level. Ageing in diverse organisms ranging from yeast to mammals appears to be associated with insufficient autophagy. Here, we summarize recent developments that outline how TOR and autophagy modulate the ageing process, with special emphasis on their role in the regulation of metabolism. A better understanding of the complex interplay between TOR, autophagy and ageing will pave the way for the development of novel therapeutic strategies to treat age-related pathologies.
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http://dx.doi.org/10.1159/000348599DOI Listing
February 2014

Guidelines for the use and interpretation of assays for monitoring autophagy.

Autophagy 2012 Apr;8(4):445-544

Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA.

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404883PMC
http://dx.doi.org/10.4161/auto.19496DOI Listing
April 2012

Autophagy and ageing: insights from invertebrate model organisms.

Ageing Res Rev 2013 Jan 24;12(1):413-28. Epub 2012 May 24.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Crete, Greece.

Ageing in diverse species ranging from yeast to humans is associated with the gradual, lifelong accumulation of molecular and cellular damage. Autophagy, a conserved lysosomal, self-destructive process involved in protein and organelle degradation, plays an essential role in both cellular and whole-animal homeostasis. Accumulating evidence now indicates that autophagic degradation declines with age and this gradual reduction of autophagy might have a causative role in the functional deterioration of biological systems during ageing. Indeed, loss of autophagy gene function significantly influences longevity. Moreover, genetic or pharmacological manipulations that extend lifespan in model organisms often activate autophagy. Interestingly, conserved signalling pathways and environmental factors that regulate ageing, such as the insulin/IGF-1 signalling pathway and oxidative stress response pathways converge on autophagy. In this article, we survey recent findings in invertebrates that contribute to advance our understanding of the molecular links between autophagy and the regulation of ageing. In addition, we consider related mechanisms in other organisms and discuss their similarities and idiosyncratic features in a comparative manner.
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http://dx.doi.org/10.1016/j.arr.2012.05.001DOI Listing
January 2013

The role of autophagy in genetic pathways influencing ageing.

Biogerontology 2011 Oct 24;12(5):377-86. Epub 2011 Feb 24.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, N. Plastira 100, Vassilika Vouton, P.O. Box 1385, 70013, Heraklion, Crete, Greece.

Autophagy is a conserved cellular degradation pathway for the breakdown of cytosolic macromolecules and organelles. Constitutive autophagy has a housekeeping role and is essential for survival, development and metabolic regulation. Autophagy is also responsive to stress and can degrade damaged proteins and organelles, oxidized lipids and intracellular pathogens. Defects in the autophagic degradation system are linked to disease pathogenesis and ageing. Different signalling pathways converge on autophagy to regulate lifespan in diverse organisms. We discuss recent findings that provide insight into the cross-talk between this critical regulator of metabolic homeostasis and molecular mechanisms that promote longevity.
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http://dx.doi.org/10.1007/s10522-011-9324-9DOI Listing
October 2011

Modeling human diseases in Caenorhabditis elegans.

Biotechnol J 2010 Dec 29;5(12):1261-76. Epub 2010 Nov 29.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, N. Plastira 100, Vassilika Vouton, Heraklion, Crete, Greece.

Genes linked to human diseases often function in evolutionarily conserved pathways, which can be readily dissected in simple model organisms. Because of its short lifespan and well-known biology, coupled with a completely sequenced genome that shares extensive homology with that of mammals, Caenorhabditis elegans is one of the most versatile and powerful model organisms. Research in C. elegans has been instrumental for the elucidation of molecular pathways implicated in many human diseases. In this review, we introduce C. elegans as a model organism for biomedical research and we survey recent relevant findings that shed light on the basic molecular determinants of human disease pathophysiology. The nematode holds promise of providing clear leads towards the identification of potential targets for the development of new therapeutic interventions against human diseases.
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http://dx.doi.org/10.1002/biot.201000183DOI Listing
December 2010

On combining information from modulation spectra and mel-frequency cepstral coefficients for automatic detection of pathological voices.

Logoped Phoniatr Vocol 2011 Jul 12;36(2):60-9. Epub 2010 Nov 12.

Universidad Politécnica de Madrid, Circuits & Systems Engineering, EUIT de Telecomunicación, Universidad Politécnica de Madrid, Ctra. Valencia, km 7, Madrid 28031, Spain.

This work presents a novel approach for the automatic detection of pathological voices based on fusing the information extracted by means of mel-frequency cepstral coefficients (MFCC) and features derived from the modulation spectra (MS). The system proposed uses a two-stepped classification scheme. First, the MFCC and MS features were used to feed two different and independent classifiers; and then the outputs of each classifier were used in a second classification stage. In order to establish the best configuration which provides the highest accuracy in the detection, the fusion of information was carried out employing different classifier combination strategies. The experiments were carried out using two different databases: the one developed by The Massachusetts Eye and Ear Infirmary Voice Laboratory, and a database recorded by the Universidad Politécnica de Madrid. The results show that the combination of MFCC and MS features employing the proposed approach yields an improvement in the detection accuracy, demonstrating that both methods of parameterization are complementary.
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http://dx.doi.org/10.3109/14015439.2010.528788DOI Listing
July 2011

The life span-prolonging effect of sirtuin-1 is mediated by autophagy.

Autophagy 2010 Jan 2;6(1):186-8. Epub 2010 Jan 2.

INSERM, U848, Villejuif, France.

The life span of various model organisms can be extended by caloric restriction as well as by autophagy-inducing pharmacological agents. Life span-prolonging effects have also been observed in yeast cells, nematodes and flies upon the overexpression of the deacetylase Sirtuin-1. Intrigued by these observations and by the established link between caloric restriction and Sirtuin-1 activation, we decided to investigate the putative implication of Sirtuin-1 in the response of human cancer cells and Caenorhabditis elegans to multiple triggers of autophagy. Our data indicate that the activation of Sirtuin-1 (by the pharmacological agent resveratrol and/or genetic means) per se ignites autophagy, and that Sirtuin-1 is required for the autophagic response to nutrient deprivation, in both human and nematode cells, but not for autophagy triggered by downstream signals such as the inhibition of mTOR or p53. Since the life spanextending effects of Sirtuin-1 activators are lost in autophagy-deficient C. elegans, our results suggest that caloric restriction and resveratrol extend longevity, at least in experimental settings, by activating autophagy.
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http://dx.doi.org/10.4161/auto.6.1.10817DOI Listing
January 2010

Using modulation spectra for voice pathology detection and classification.

Annu Int Conf IEEE Eng Med Biol Soc 2009 ;2009:2514-7

Department of Computer Science, University of Crete, 71409 Crete, Greece.

In this paper, we consider the use of Modulation Spectra for voice pathology detection and classification. To reduce the high-dimensionality space generated by Modulation spectra we suggest the use of Higher Order Singular Value Decomposition (SVD) and we propose a feature selection algorithm based on the Mutual Information between subjective voice quality and computed features. Using SVM with a radial basis function (RBF) kernel as classifier, we conducted experiments on a database of sustained vowel recordings from healthy and pathological voices. For voice pathology detection, the suggested approach achieved a detection rate of 94.1% and an Area Under the Curve (AUC) score of 97.8%. For voice pathology classification, an average detection rate and AUC of 88.6% and 94.8%, respectively, was achieved in classifying polyp against keratosis leukoplakia, adductor spasmodic dysphonia and vocal nodules.
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http://dx.doi.org/10.1109/IEMBS.2009.5334850DOI Listing
March 2010

Stable expression of human growth hormone over 50 generations in transgenic insect larvae.

Transgenic Res 2007 Feb 11;16(1):99-107. Epub 2006 Nov 11.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, PO Box 1385, Heraklion, 71110, Greece.

Developments in insect transgenesis using transposons combined with available mass rearing technology for insects such as the Medfly, Ceratitis capitata, provide opportunity for the production of protein for industrial, agricultural and healthcare purposes on a very large scale. In this study, we report the germ-line transformation and expression of a cDNA encoding human growth hormone (hGH) in transgenic Drosophila using the Minos transposon. Production and secretion of a bioactive hGH into the haemolymph of transgenic larvae was demonstrated by immunoblot analysis, ELISA and a proliferation bioassay. Stable expression of hGH was observed over 50 generations. The results indicate that mass reared transgenic diptera with a rapid period of larval growth could provide cost effective production systems for the manufacture of therapeutic and other high value proteins.
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http://dx.doi.org/10.1007/s11248-006-9032-4DOI Listing
February 2007
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