Publications by authors named "Luca Scorrano"

155 Publications

Autophagy in major human diseases.

EMBO J 2021 Oct 30;40(19):e108863. Epub 2021 Aug 30.

Signalling Programme, Babraham Institute, Cambridge, UK.

Autophagy is a core molecular pathway for the preservation of cellular and organismal homeostasis. Pharmacological and genetic interventions impairing autophagy responses promote or aggravate disease in a plethora of experimental models. Consistently, mutations in autophagy-related processes cause severe human pathologies. Here, we review and discuss preclinical data linking autophagy dysfunction to the pathogenesis of major human disorders including cancer as well as cardiovascular, neurodegenerative, metabolic, pulmonary, renal, infectious, musculoskeletal, and ocular disorders.
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http://dx.doi.org/10.15252/embj.2021108863DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8488577PMC
October 2021

Revisiting the evidence for physical distancing, face masks, and eye protection.

Lancet 2021 08;398(10301):660-661

Department of Experimental Oncology, European Institute of Oncology, IRCCS, 20139 Milano, Italy. Electronic address:

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http://dx.doi.org/10.1016/S0140-6736(21)01736-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8376237PMC
August 2021

Sustained intracellular calcium rise mediates neuronal mitophagy in models of autosomal dominant optic atrophy.

Cell Death Differ 2021 Aug 13. Epub 2021 Aug 13.

Veneto Institute of Molecular Medicine, Padova, Italy.

Mitochondrial dysfunction and mitophagy are often hallmarks of neurodegenerative diseases such as autosomal dominant optic atrophy (ADOA) caused by mutations in the key mitochondrial dynamics protein optic atrophy 1 (Opa1). However, the second messengers linking mitochondrial dysfunction to initiation of mitophagy remain poorly characterized. Here, we show in mammalian and nematode neurons that Opa1 mutations trigger Ca-dependent mitophagy. Deletion or expression of mutated Opa1 in mouse retinal ganglion cells and Caenorhabditis elegans motor neurons lead to mitochondrial dysfunction, increased cytosolic Ca levels, and decreased axonal mitochondrial density. Chelation of Ca restores mitochondrial density in neuronal processes, neuronal function, and viability. Mechanistically, sustained Ca levels activate calcineurin and AMPK, placed in the same genetic pathway regulating axonal mitochondrial density. Our data reveal that mitophagy in ADOA depends on Ca-calcineurin-AMPK signaling cascade.
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http://dx.doi.org/10.1038/s41418-021-00847-3DOI Listing
August 2021

A cross-sectional and prospective cohort study of the role of schools in the SARS-CoV-2 second wave in Italy.

Lancet Reg Health Eur 2021 Jun 26;5:100092. Epub 2021 Mar 26.

Department of Biology, University of Padua, Via U. Bassi 58B, 35131 Padova, Italy.

Background: During COVID-19 pandemic, school closure has been mandated in analogy to its effect against influenza, but it is unclear whether schools are early COVID-19 amplifiers.

Methods: We performed a cross-sectional and prospective cohort study in Italy during the second COVID-19 wave (from September 30, 2020 until at least February 28, 2021). We used databases from the Italian Ministry of Education, the Veneto region systems of SARS-CoV-2 cases notification and of schools' secondary cases tracing to compare SARS-CoV-2 incidence in students/school staff and general population and incidence across age groups. Number of tests, secondary infections by type of index case and ratio cases/ tests per school were estimated using an adjusted multivariable generalized linear regression model. Regional reproduction numbers R were estimated from Italian Civil Protection daily incidence data with a method of posterior distribution using a Markov Chain Monte Carlo algorithm.

Findings: SARS-CoV-2 incidence among students was lower than in the general population. Secondary infections at school were <1%, and clusters of ≥2 secondary cases occurred in 5-7% of the analysed schools. Incidence among teachers was comparable to the population of similar age ( = 0.23). Secondary infections among teachers were rare, occurring more frequently when the index case was a teacher than a student (37% vs. 10%,  = 0.007). Before and around the date of school opening in Veneto, SARS-CoV-2 incidence grew maximally in 20-29- and 45-49-years old individuals, not among students. The lag between school opening dates in Italian regions and the increase in the regional COVID-19 R was not uniform. Finally, school closures in two regions where they were implemented before other measures did not affect R decrease.

Interpretation: This analysis does not support a role for school opening as a driver of the second COVID-19 wave in Italy, a large European country with high SARS-CoV-2 incidence.

Funding: Fondazione MITE.
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http://dx.doi.org/10.1016/j.lanepe.2021.100092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7995620PMC
June 2021

Dietary spermidine improves cognitive function.

Cell Rep 2021 Apr;35(2):108985

Department of Internal Medicine I, Gastroenterology, Hepatology, Endocrinology and Metabolism, Medical University of Innsbruck, 6020 Innsbruck, Austria.

Decreased cognitive performance is a hallmark of brain aging, but the underlying mechanisms and potential therapeutic avenues remain poorly understood. Recent studies have revealed health-protective and lifespan-extending effects of dietary spermidine, a natural autophagy-promoting polyamine. Here, we show that dietary spermidine passes the blood-brain barrier in mice and increases hippocampal eIF5A hypusination and mitochondrial function. Spermidine feeding in aged mice affects behavior in homecage environment tasks, improves spatial learning, and increases hippocampal respiratory competence. In a Drosophila aging model, spermidine boosts mitochondrial respiratory capacity, an effect that requires the autophagy regulator Atg7 and the mitophagy mediators Parkin and Pink1. Neuron-specific Pink1 knockdown abolishes spermidine-induced improvement of olfactory associative learning. This suggests that the maintenance of mitochondrial and autophagic function is essential for enhanced cognition by spermidine feeding. Finally, we show large-scale prospective data linking higher dietary spermidine intake with a reduced risk for cognitive impairment in humans.
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http://dx.doi.org/10.1016/j.celrep.2021.108985DOI Listing
April 2021

Opa1 relies on cristae preservation and ATP synthase to curtail reactive oxygen species accumulation in mitochondria.

Redox Biol 2021 05 19;41:101944. Epub 2021 Mar 19.

Veneto Institute of Molecular Medicine, Padova, Italy; Department of Biology, University of Padova, Padova, Italy. Electronic address:

Reactive oxygen species (ROS) are a common product of active mitochondrial respiration carried in mitochondrial cristae, but whether cristae shape influences ROS levels is unclear. Here we report that the mitochondrial fusion and cristae shape protein Opa1 requires mitochondrial ATP synthase oligomers to reduce ROS accumulation. In cells fueled with galactose to force ATP production by mitochondria, cristae are enlarged, ATP synthase oligomers destabilized, and ROS accumulate. Opa1 prevents both cristae remodeling and ROS generation, without impinging on levels of mitochondrial antioxidant defense enzymes that are unaffected by Opa1 overexpression. Genetic and pharmacologic experiments indicate that Opa1 requires ATP synthase oligomerization and activity to reduce ROS levels upon a blockage of the electron transport chain. Our results indicate that the converging effect of Opa1 and mitochondrial ATP synthase on mitochondrial ultrastructure regulate ROS abundance to sustain cell viability.
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http://dx.doi.org/10.1016/j.redox.2021.101944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8039725PMC
May 2021

Mitochondria-rough-ER contacts in the liver regulate systemic lipid homeostasis.

Cell Rep 2021 03;34(11):108873

Mitochondria Biology Laboratory, Brain Research Center, Quebec, QC, Canada; Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, QC, Canada. Electronic address:

Contacts between organelles create microdomains that play major roles in regulating key intracellular activities and signaling pathways, but whether they also regulate systemic functions remains unknown. Here, we report the ultrastructural organization and dynamics of the inter-organellar contact established by sheets of curved rough endoplasmic reticulum closely wrapped around the mitochondria (wrappER). To elucidate the in vivo function of this contact, mouse liver fractions enriched in wrappER-associated mitochondria are analyzed by transcriptomics, proteomics, and lipidomics. The biochemical signature of the wrappER points to a role in the biogenesis of very-low-density lipoproteins (VLDL). Altering wrappER-mitochondria contacts curtails VLDL secretion and increases hepatic fatty acids, lipid droplets, and neutral lipid content. Conversely, acute liver-specific ablation of Mttp, the most upstream regulator of VLDL biogenesis, recapitulates this hepatic dyslipidemia phenotype and promotes remodeling of the wrappER-mitochondria contact. The discovery that liver wrappER-mitochondria contacts participate in VLDL biology suggests an involvement of inter-organelle contacts in systemic lipid homeostasis.
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http://dx.doi.org/10.1016/j.celrep.2021.108873DOI Listing
March 2021

Deletion of the mitochondria-shaping protein Opa1 during early thymocyte maturation impacts mature memory T cell metabolism.

Cell Death Differ 2021 Jul 1;28(7):2194-2206. Epub 2021 Mar 1.

Veneto Institute of Molecular Medicine, Padua, Italy.

Optic atrophy 1 (OPA1), a mitochondria-shaping protein controlling cristae biogenesis and respiration, is required for memory T cell function, but whether it affects intrathymic T cell development is unknown. Here we show that OPA1 is necessary for thymocyte maturation at the double negative (DN)3 stage when rearrangement of the T cell receptor β (Tcrβ) locus occurs. By profiling mitochondrial function at different stages of thymocyte maturation, we find that DN3 cells rely on oxidative phosphorylation. Consistently, Opa1 deletion during early T cell development impairs respiration of DN3 cells and reduces their number. Opa1-deficient DN3 cells indeed display stronger TCR signaling and are more prone to cell death. The surviving Opa1 thymocytes that reach the periphery as mature T cells display an effector memory phenotype even in the absence of antigenic stimulation but are unable to generate metabolically fit long-term memory T cells. Thus, mitochondrial defects early during T cell development affect mature T cell function.
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http://dx.doi.org/10.1038/s41418-021-00747-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8257785PMC
July 2021

OPA1, a new mitochondrial target in cancer therapy.

Aging (Albany NY) 2020 11 13;12(21):20931-20933. Epub 2020 Nov 13.

Department of Biology, University of Padova, Padova, Italy.

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http://dx.doi.org/10.18632/aging.104207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695375PMC
November 2020

Inhibition of autophagy curtails visual loss in a model of autosomal dominant optic atrophy.

Nat Commun 2020 08 12;11(1):4029. Epub 2020 Aug 12.

Veneto Institute of Molecular Medicine, Via Orus 2, Padova, Italy.

In autosomal dominant optic atrophy (ADOA), caused by mutations in the mitochondrial cristae biogenesis and fusion protein optic atrophy 1 (Opa1), retinal ganglion cell (RGC) dysfunction and visual loss occur by unknown mechanisms. Here, we show a role for autophagy in ADOA pathogenesis. In RGCs expressing mutated Opa1, active 5' AMP-activated protein kinase (AMPK) and its autophagy effector ULK1 accumulate at axonal hillocks. This AMPK activation triggers localized hillock autophagosome accumulation and mitophagy, ultimately resulting in reduced axonal mitochondrial content that is restored by genetic inhibition of AMPK and autophagy. In C. elegans, deletion of AMPK or of key autophagy and mitophagy genes normalizes the axonal mitochondrial content that is reduced upon mitochondrial dysfunction. In conditional, RGC specific Opa1-deficient mice, depletion of the essential autophagy gene Atg7 normalizes the excess autophagy and corrects the visual defects caused by Opa1 ablation. Thus, our data identify AMPK and autophagy as targetable components of ADOA pathogenesis.
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http://dx.doi.org/10.1038/s41467-020-17821-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423926PMC
August 2020

P73 C-terminus is dispensable for multiciliogenesis.

Cell Cycle 2020 07 25;19(14):1833-1845. Epub 2020 Jun 25.

Medical Research Council, Toxicology Unit, Department of Pathology, Cambridge University , Cambridge, UK.

The p53 family transcriptional factor p73 plays a pivotal role in development. Ablation of p73 results in severe neurodevelopmental defects, chronic infections, inflammation and infertility. In addition to this, Trp73 mice display severe alteration in the ciliated epithelial lining and the full-length -terminal isoform TAp73 has been implicated in the control of multiciliogenesis transcriptional program. With our recently generated Trp73 mouse model, we interrogate the physiological role of p73 C-terminal isoforms . Trp73 mice lack exon 13 in Trp73 gene, producing an ectopic switch from the C-terminal isoforms p73α to p73β. Trp73 mice show a pattern of expression of TAp73 comparable to the wild-type littermates, indicating that the to switch does not significantly alter the expression of the gene in this cell type. Moreover, Trp73 do not display any significant alteration in the airway ciliated epithelium, suggesting that in this context p73β can fully substitute the function of the longer isoform p73α. Similarly, Trp73 ciliated epithelium of the brain ependyma also does appear defective. In this district however expression of TAp73 is not detectable, indicating that expression of the gene might be compensated by alternative mechanisms. Overall our work indicates that C-terminus p73 is dispensable for the multiciliogenesis program and suggests a possible tissue-specific effect of p73 alternative splicing.
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http://dx.doi.org/10.1080/15384101.2020.1783055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7469635PMC
July 2020

Opa1 Overexpression Protects from Early-Onset Mpv17-Related Mouse Kidney Disease.

Mol Ther 2020 08 12;28(8):1918-1930. Epub 2020 Jun 12.

Department of Biomedical Sciences, University of Padova, via Ugo Bassi 58/B, 35131 Padova, Italy. Electronic address:

Moderate overexpression of Opa1, the master regulator of mitochondrial cristae morphology, significantly improved mitochondrial damage induced by drugs, surgical denervation, or oxidative phosphorylation (OXPHOS) defects due to specific impairment of a single mitochondrial respiratory chain complex. Here, we investigated the effectiveness of this approach in the Mpv17 mouse, characterized by profound, multisystem mitochondrial DNA (mtDNA) depletion. After the crossing with Opa1 mice, we found a surprising anticipation of the severe, progressive focal segmental glomerulosclerosis, previously described in Mpv17 animals as a late-onset clinical feature (after 12-18 months of life). In contrast, Mpv17 animals from this new "mixed" strain died at 8-9 weeks after birth because of severe kidney failure However, Mpv17::Opa1 mice lived much longer than Mpv17 littermates and developed the kidney dysfunction much later. mtDNA content and OXPHOS activities were significantly higher in Mpv17::Opa1 than in Mpv17 kidneys and similar to those for wild-type (WT) littermates. Mitochondrial network and cristae ultrastructure were largely preserved in Mpv17::Opa1 versus Mpv17 kidney and isolated podocytes. Mechanistically, the protective effect of Opa1 overexpression in this model was mediated by a block in apoptosis due to the stabilization of the mitochondrial cristae. These results demonstrate that strategies aiming at increasing Opa1 expression or activity can be effective against mtDNA depletion syndromes.
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http://dx.doi.org/10.1016/j.ymthe.2020.06.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7403474PMC
August 2020

Developmental and Tumor Angiogenesis Requires the Mitochondria-Shaping Protein Opa1.

Cell Metab 2020 05 20;31(5):987-1003.e8. Epub 2020 Apr 20.

Department of Biology, University of Padova, Via U. Bassi 58B, 35121 Padova, Italy; Veneto Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy. Electronic address:

While endothelial cell (EC) function is influenced by mitochondrial metabolism, the role of mitochondrial dynamics in angiogenesis, the formation of new blood vessels from existing vasculature, is unknown. Here we show that the inner mitochondrial membrane mitochondrial fusion protein optic atrophy 1 (OPA1) is required for angiogenesis. In response to angiogenic stimuli, OPA1 levels rapidly increase to limit nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) signaling, ultimately allowing angiogenic genes expression and angiogenesis. Endothelial Opa1 is indeed required in an NFκB-dependent pathway essential for developmental and tumor angiogenesis, impacting tumor growth and metastatization. A first-in-class small molecule-specific OPA1 inhibitor confirms that EC Opa1 can be pharmacologically targeted to curtail tumor growth. Our data identify Opa1 as a crucial component of physiological and tumor angiogenesis.
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http://dx.doi.org/10.1016/j.cmet.2020.04.007DOI Listing
May 2020

The cell biology of mitochondrial membrane dynamics.

Nat Rev Mol Cell Biol 2020 04 18;21(4):204-224. Epub 2020 Feb 18.

Department of Biology, University of Padua, Padua, Italy.

Owing to their ability to efficiently generate ATP required to sustain normal cell function, mitochondria are often considered the 'powerhouses of the cell'. However, our understanding of the role of mitochondria in cell biology recently expanded when we recognized that they are key platforms for a plethora of cell signalling cascades. This functional versatility is tightly coupled to constant reshaping of the cellular mitochondrial network in a series of processes, collectively referred to as mitochondrial membrane dynamics and involving organelle fusion and fission (division) as well as ultrastructural remodelling of the membrane. Accordingly, mitochondrial dynamics influence and often orchestrate not only metabolism but also complex cell signalling events, such as those involved in regulating cell pluripotency, division, differentiation, senescence and death. Reciprocally, mitochondrial membrane dynamics are extensively regulated by post-translational modifications of its machinery and by the formation of membrane contact sites between mitochondria and other organelles, both of which have the capacity to integrate inputs from various pathways. Here, we discuss mitochondrial membrane dynamics and their regulation and describe how bioenergetics and cellular signalling are linked to these dynamic changes of mitochondrial morphology.
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http://dx.doi.org/10.1038/s41580-020-0210-7DOI Listing
April 2020

MCUB Hearts Mitochondria in Sickness, Less in Health.

Circulation 2019 11 18;140(21):1734-1736. Epub 2019 Nov 18.

Department of Biology, University of Padua, Italy (L.S.).

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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.043440DOI Listing
November 2019

Impaired Mitochondrial ATP Production Downregulates Wnt Signaling via ER Stress Induction.

Cell Rep 2019 08;28(8):1949-1960.e6

Department of Biology, University of Padova, Padova, Italy. Electronic address:

Wnt signaling affects fundamental development pathways and, if aberrantly activated, promotes the development of cancers. Wnt signaling is modulated by different factors, but whether the mitochondrial energetic state affects Wnt signaling is unknown. Here, we show that sublethal concentrations of different compounds that decrease mitochondrial ATP production specifically downregulate Wnt/β-catenin signaling in vitro in colon cancer cells and in vivo in zebrafish reporter lines. Accordingly, fibroblasts from a GRACILE syndrome patient and a generated zebrafish model lead to reduced Wnt signaling. We identify a mitochondria-Wnt signaling axis whereby a decrease in mitochondrial ATP reduces calcium uptake into the endoplasmic reticulum (ER), leading to endoplasmic reticulum stress and to impaired Wnt signaling. In turn, the recovery of the ATP level or the inhibition of endoplasmic reticulum stress restores Wnt activity. These findings reveal a mechanism that links mitochondrial energetic metabolism to the control of the Wnt pathway that may be beneficial against several pathologies.
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http://dx.doi.org/10.1016/j.celrep.2019.07.050DOI Listing
August 2019

Inhibition of the Fission Machinery Mitigates OPA1 Impairment in Adult Skeletal Muscles.

Cells 2019 06 15;8(6). Epub 2019 Jun 15.

Veneto Institute of Molecular Medicine, via Orus 2, 35129 Padua, Italy.

The maintenance of muscle mass and its ability to function relies on a bioenergetic efficient mitochondrial network. This network is highly impacted by fusion and fission events. We have recently shown that the acute deletion of the fusion protein Opa1 induces muscle atrophy, systemic inflammatory response, precocious epithelial senescence, and premature death that are caused by muscle-dependent secretion of FGF21. However, both fusion and fission machinery are suppressed in aging sarcopenia, cancer cachexia, and chemotherapy-induced muscle wasting. We generated inducible muscle-specific Opa1 and Drp1 double-knockout mice to address the physiological relevance of the concomitant impairment of fusion and fission machinery in skeletal muscle. Here we show that acute ablation of Opa1 and Drp1 in adult muscle causes the accumulation of abnormal and dysfunctional mitochondria, as well as the inhibition of autophagy and mitophagy pathways. This ultimately results in ER stress, muscle loss, and the reduction of force generation. However, the simultaneous inhibition of the fission protein Drp1 when Opa1 is absent alleviates FGF21 induction, oxidative stress, denervation, and inflammation rescuing the lethal phenotype of Opa1 knockout mice, despite the presence of any muscle weakness. Thus, the simultaneous inhibition of fusion and fission processes mitigates the detrimental effects of unbalanced mitochondrial fusion and prevents the secretion of pro-senescence factors.
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http://dx.doi.org/10.3390/cells8060597DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627087PMC
June 2019

DRP1-mediated mitochondrial shape controls calcium homeostasis and muscle mass.

Nat Commun 2019 06 12;10(1):2576. Epub 2019 Jun 12.

Venetian Institute of Molecular Medicine, via Orus 2, 35129, Padova, Italy.

Mitochondrial quality control is essential in highly structured cells such as neurons and muscles. In skeletal muscle the mitochondrial fission proteins are reduced in different physiopathological conditions including ageing sarcopenia, cancer cachexia and chemotherapy-induced muscle wasting. However, whether mitochondrial fission is essential for muscle homeostasis is still unclear. Here we show that muscle-specific loss of the pro-fission dynamin related protein (DRP) 1 induces muscle wasting and weakness. Constitutive Drp1 ablation in muscles reduces growth and causes animal death while inducible deletion results in atrophy and degeneration. Drp1 deficient mitochondria are morphologically bigger and functionally abnormal. The dysfunctional mitochondria signals to the nucleus to induce the ubiquitin-proteasome system and an Unfolded Protein Response while the change of mitochondrial volume results in an increase of mitochondrial Ca uptake and myofiber death. Our findings reveal that morphology of mitochondrial network is critical for several biological processes that control nuclear programs and Ca handling.
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http://dx.doi.org/10.1038/s41467-019-10226-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6561930PMC
June 2019

Too close not to encyst: Polycystic kidney disease and interorganellar contact sites.

Sci Signal 2019 05 28;12(583). Epub 2019 May 28.

Department of Biology, University of Padua, 35121 Padua, Italy.

Mitofusin 2 (MFN2) tethers mitochondria to the endoplasmic reticulum (ER). In the 7 May 2019 issue of , Kuo report that polycystin 2 (PC2), encoded by a gene mutated in type 2 autosomal dominant polycystic kidney disease (ADPKD), contributes to cystogenesis by affecting MFN2, thus extending the role of mitochondria-ER contact sites to a common genetic disorder.
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http://dx.doi.org/10.1126/scisignal.aaw6996DOI Listing
May 2019

PARP Inhibitor PJ34 Protects Mitochondria and Induces DNA-Damage Mediated Apoptosis in Combination With Cisplatin or Temozolomide in B16F10 Melanoma Cells.

Front Physiol 2019 7;10:538. Epub 2019 May 7.

Department of Biochemistry and Medical Chemistry, Medical School, University of Pécs, Pécs, Hungary.

PARP-1 inhibition has recently been employed in both mono- and combination therapies in various malignancies including melanoma with both promising and contradicting results reported. Although deeper understanding of the underlying molecular mechanisms may help improving clinical modalities, the complex cellular effects of PARP inhibitors make disentangling of the mechanisms involved in combination therapies difficult. Here, we used two cytostatic agents used in melanoma therapies in combination with PARP inhibition to have an insight into cellular events using the B16F10 melanoma model. We found that, when used in combination with cisplatin or temozolomide, pharmacologic blockade of PARP-1 by PJ34 augmented the DNA-damaging and cytotoxic effects of both alkylating compounds. Interestingly, however, this synergism unfolds relatively slowly and is preceded by molecular events that are traditionally believed to support cell survival including the stabilization of mitochondrial membrane potential and morphology. Our data indicate that the PARP inhibitor PJ34 has, apparently, opposing effects on the mitochondrial structure and cell survival. While, initially, it stimulates mitochondrial fusion and hyperpolarization, hallmarks of mitochondrial protection, it enhances the cytotoxic effects of alkylating agents at later stages. These findings may contribute to the optimization of PARP inhibitor-based antineoplastic modalities.
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http://dx.doi.org/10.3389/fphys.2019.00538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6514236PMC
May 2019

Functional wiring of proteostatic and mitostatic modules ensures transient organismal survival during imbalanced mitochondrial dynamics.

Redox Biol 2019 06 17;24:101219. Epub 2019 May 17.

Department of Cell Biology and Biophysics, Faculty of Biology, National & Kapodistrian University of Athens, 15784, Greece. Electronic address:

Being an assembly of protein machines, cells depend on adequate supply of energetic molecules for retaining their homeodynamics. Consequently, mitochondria functionality is ensured by quality control systems and mitochondrial dynamics (fusion/fission). Similarly, proteome stability is maintained by the machineries of the proteostasis network. We report here that reduced mitochondrial fusion rates in Drosophila caused developmental lethality or if induced in the adult accelerated aging. Imbalanced mitochondrial dynamics were tolerable for various periods in young flies, where they caused oxidative stress and proteome instability that mobilized Nrf2 and foxo to upregulate cytoprotective antioxidant/proteostatic modules. Consistently, proteasome inhibition or Nrf2, foxo knock down in young flies exaggerated perturbed mitochondrial dynamics toxicity. Neither Nrf2 overexpression (with concomitant proteasome activation) nor Atg8a upregulation suppressed the deregulated mitochondrial dynamics toxicity, which was mildly mitigated by antioxidants. Thus, despite extensive functional wiring of mitostatic and antioxidant/proteostatic modules, sustained loss-of mitostasis exhausts adaptation responses triggering premature aging.
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http://dx.doi.org/10.1016/j.redox.2019.101219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6536731PMC
June 2019

Proteasome dysfunction induces excessive proteome instability and loss of mitostasis that can be mitigated by enhancing mitochondrial fusion or autophagy.

Autophagy 2019 10 19;15(10):1757-1773. Epub 2019 Apr 19.

Department of Cell Biology and Biophysics, Faculty of Biology, National and Kapodistrian University of Athens , Athens , Greece.

The ubiquitin-proteasome pathway (UPP) is central to proteostasis network (PN) functionality and proteome quality control. Yet, the functional implication of the UPP in tissue homeodynamics at the whole organism level and its potential cross-talk with other proteostatic or mitostatic modules are not well understood. We show here that knock down (KD) of proteasome subunits in flies, induced, for most subunits, developmental lethality. Ubiquitous or tissue specific proteasome dysfunction triggered systemic proteome instability and activation of PN modules, including macroautophagy/autophagy, molecular chaperones and the antioxidant cncC (the fly ortholog of NFE2L2/Nrf2) pathway. Also, proteasome KD increased genomic instability, altered metabolic pathways and severely disrupted mitochondrial functionality, triggering a cncC-dependent upregulation of mitostatic genes and enhanced rates of mitophagy. Whereas, overexpression of key regulators of antioxidant responses (e.g., cncC or foxo) could not suppress the deleterious effects of proteasome dysfunction; these were alleviated in both larvae and adult flies by modulating mitochondrial dynamics towards increased fusion or by enhancing autophagy. Our findings reveal the extensive functional wiring of genomic, proteostatic and mitostatic modules in higher metazoans. Also, they support the notion that age-related increase of proteotoxic stress due to decreased UPP activity deregulates all aspects of cellular functionality being thus a driving force for most age-related diseases. ALP: autophagy-lysosome pathway; ARE: antioxidant response element; Atg8a: autophagy-related 8a; ATPsynβ: ATP synthase, β subunit; C-L: caspase-like proteasomal activity; cncC: cap-n-collar isoform-C; CT-L: chymotrypsin-like proteasomal activity; Drp1: dynamin related protein 1; ER: endoplasmic reticulum; foxo: forkhead box, sub-group O; GLU: glucose; GFP: green fluorescent protein; GLY: glycogen; Hsf: heat shock factor; Hsp: Heat shock protein; Keap1: kelch-like ECH-associated protein 1; Marf: mitochondrial assembly regulatory factor; NFE2L2/Nrf2: nuclear factor, erythroid 2 like 2; Opa1: optic atrophy 1; PN: proteostasis network; RNAi: RNA interference; ROS: reactive oxygen species; ref(2)P: refractory to sigma P; SQSTM1: sequestosome 1; SdhA: succinate dehydrogenase, subunit A; T-L: trypsin-like proteasomal activity; TREH: trehalose; UAS: upstream activation sequence; Ub: ubiquitin; UPR: unfolded protein response; UPP: ubiquitin-proteasome pathway.
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http://dx.doi.org/10.1080/15548627.2019.1596477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6735541PMC
October 2019

Inhibition of the deubiquitinase USP8 corrects a Drosophila PINK1 model of mitochondria dysfunction.

Life Sci Alliance 2019 04 15;2(2). Epub 2019 Apr 15.

Fondazione Ospedale San Camillo, IRCCS, Venezia, Italy

Aberrant mitochondrial dynamics disrupts mitochondrial function and contributes to disease conditions. A targeted RNA interference screen for deubiquitinating enzymes (DUBs) affecting protein levels of multifunctional mitochondrial fusion protein Mitofusin (MFN) identified USP8 prominently influencing MFN levels. Genetic and pharmacological inhibition of USP8 normalized the elevated MFN protein levels observed in PINK1 and Parkin-deficient models. This correlated with improved mitochondrial function, locomotor performance and life span, and prevented dopaminergic neurons loss in PINK1 KO flies. We identified a novel target antagonizing pathologically elevated MFN levels, mitochondrial dysfunction, and dopaminergic neuron loss of a model of mitochondrial dysfunction.
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http://dx.doi.org/10.26508/lsa.201900392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467245PMC
April 2019

Transcriptomic Analysis of Single Isolated Myofibers Identifies miR-27a-3p and miR-142-3p as Regulators of Metabolism in Skeletal Muscle.

Cell Rep 2019 03;26(13):3784-3797.e8

Department of Biology, University of Padova, Via Ugo Bassi 58/b, 35131 Padova, Italy; CRIBI Biotechnology Centre, University of Padova, Via Ugo Bassi 58/b, 35131 Padova, Italy; CIR-Myo Myology Center, University of Padova, Via Ugo Bassi 58/b, 35131 Padova, Italy. Electronic address:

Skeletal muscle is composed of different myofiber types that preferentially use glucose or lipids for ATP production. How fuel preference is regulated in these post-mitotic cells is largely unknown, making this issue a key question in the fields of muscle and whole-body metabolism. Here, we show that microRNAs (miRNAs) play a role in defining myofiber metabolic profiles. mRNA and miRNA signatures of all myofiber types obtained at the single-cell level unveiled fiber-specific regulatory networks and identified two master miRNAs that coordinately control myofiber fuel preference and mitochondrial morphology. Our work provides a complete and integrated mouse myofiber type-specific catalog of gene and miRNA expression and establishes miR-27a-3p and miR-142-3p as regulators of lipid use in skeletal muscle.
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http://dx.doi.org/10.1016/j.celrep.2019.02.105DOI Listing
March 2019

Coming together to define membrane contact sites.

Nat Commun 2019 03 20;10(1):1287. Epub 2019 Mar 20.

Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel.

Close proximities between organelles have been described for decades. However, only recently a specific field dealing with organelle communication at membrane contact sites has gained wide acceptance, attracting scientists from multiple areas of cell biology. The diversity of approaches warrants a unified vocabulary for the field. Such definitions would facilitate laying the foundations of this field, streamlining communication and resolving semantic controversies. This opinion, written by a panel of experts in the field, aims to provide this burgeoning area with guidelines for the experimental definition and analysis of contact sites. It also includes suggestions on how to operationally and tractably measure and analyze them with the hope of ultimately facilitating knowledge production and dissemination within and outside the field of contact-site research.
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http://dx.doi.org/10.1038/s41467-019-09253-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6427007PMC
March 2019

Finding a new balance to cure Charcot-Marie-Tooth 2A.

J Clin Invest 2019 03 18;129(4):1533-1535. Epub 2019 Mar 18.

Venetian Institute of Molecular Medicine, Padova, Italy.

Motoneurons are particularly sensitive to mutations in mitofusin-2 (MFN2) that cause the neurological disorder Charcot-Marie-Tooth disease type 2A (CMT2A). MFN2 is a mitochondrial outer membrane protein that, together with its homologue MFN1, fuses mitochondria in most tissues. In this issue of the JCI, Zhou and colleagues show that increasing MFN1 expression in neurons can curtail neurological defects in a CMT2A mouse model. These results show that the ratio of MFN1 to MFN2 can explain the tissue specificity of CMT2A and indicate that augmentation of MFN1 in the nervous system has potential as a possible therapeutic strategy for CMT2A.
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http://dx.doi.org/10.1172/JCI127820DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6436877PMC
March 2019

Single cell analysis reveals the involvement of the long non-coding RNA Pvt1 in the modulation of muscle atrophy and mitochondrial network.

Nucleic Acids Res 2019 02;47(4):1653-1670

Department of Biology, University of Padova, 35131 Padova, Italy.

Long non-coding RNAs (lncRNAs) are emerging as important players in the regulation of several aspects of cellular biology. For a better comprehension of their function, it is fundamental to determine their tissue or cell specificity and to identify their subcellular localization. In fact, the activity of lncRNAs may vary according to cell and tissue specificity and subcellular compartmentalization. Myofibers are the smallest complete contractile system of skeletal muscle influencing its contraction velocity and metabolism. How lncRNAs are expressed in different myofibers, participate in metabolism regulation and muscle atrophy or how they are compartmentalized within a single myofiber is still unknown. We compiled a comprehensive catalog of lncRNAs expressed in skeletal muscle, associating the fiber-type specificity and subcellular location to each of them, and demonstrating that many lncRNAs can be involved in the biological processes de-regulated during muscle atrophy. We demonstrated that the lncRNA Pvt1, activated early during muscle atrophy, impacts mitochondrial respiration and morphology and affects mito/autophagy, apoptosis and myofiber size in vivo. This work corroborates the importance of lncRNAs in the regulation of metabolism and neuromuscular pathologies and offers a valuable resource to study the metabolism in single cells characterized by pronounced plasticity.
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http://dx.doi.org/10.1093/nar/gkz007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6393313PMC
February 2019

Hyperactivation of Nrf2 increases stress tolerance at the cost of aging acceleration due to metabolic deregulation.

Aging Cell 2019 02 10;18(1):e12845. Epub 2018 Dec 10.

Department of Cell Biology and Biophysics, Faculty of Biology, National & Kapodistrian University of Athens, Athens, Greece.

Metazoans viability depends on their ability to regulate metabolic processes and also to respond to harmful challenges by mounting anti-stress responses; these adaptations were fundamental forces during evolution. Central to anti-stress responses are a number of short-lived transcription factors that by functioning as stress sensors mobilize genomic responses aiming to eliminate stressors. We show here that increased expression of nuclear factor erythroid 2-related factor (Nrf2) in Drosophila activated cytoprotective modules and enhanced stress tolerance. However, while mild Nrf2 activation extended lifespan, high Nrf2 expression levels resulted in developmental lethality or, after inducible activation in adult flies, in altered mitochondrial bioenergetics, the appearance of Diabetes Type 1 hallmarks and aging acceleration. Genetic or dietary suppression of Insulin/IGF-like signaling (IIS) titrated Nrf2 activity to lower levels, largely normalized metabolic pathways signaling, and extended flies' lifespan. Thus, prolonged stress signaling by otherwise cytoprotective short-lived stress sensors perturbs IIS resulting in re-allocation of resources from growth and longevity to somatic preservation and stress tolerance. These findings provide a reasonable explanation of why most (if not all) cytoprotective stress sensors are short-lived proteins, and it also explains the build-in negative feedback loops (shown here for Nrf2); the low basal levels of these proteins, and why their suppressors were favored by evolution.
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http://dx.doi.org/10.1111/acel.12845DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6351879PMC
February 2019

Proenkephalin Derived Peptides Are Involved in the Modulation of Mitochondrial Respiratory Control During Epileptogenesis.

Front Mol Neurosci 2018 25;11:351. Epub 2018 Sep 25.

Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria.

Epilepsies are a group of common neurological diseases exerting a strong burden on patients and society, often lacking clear etiology and effective therapeutical strategies. Early intervention during the development of epilepsy (epileptogenesis) is of great medical interest, though hampered by poorly characterized epileptogenetic processes. Using the intrahippocampal kainic acid mouse model of temporal lobe epilepsy, we investigated the functional role of the endogenous opioid enkephalin during epileptogenesis. We addressed three sequential questions: (1) How does enkephalin affect seizure threshold and how is it regulated during epileptogenesis? (2) Does enkephalin influence detrimental effects during epileptogenesis? (3) How is enkephalin linked to mitochondrial function during epileptogenesis?. In contrast to other neuropeptides, the expression of enkephalin is not regulated in a seizure dependent manner. The pattern of regulation, and enkephalin's proconvulsive effects suggested it as a potential driving force in epileptogenesis. Surprisingly, enkephalin deficiency aggravated progressive granule cell dispersion in kainic acid induced epileptogenesis. Based on reported beneficial effects of enkephalin on mitochondrial function in hypoxic/ischemic states, we hypothesized that enkephalin may be involved in the adaptation of mitochondrial respiration during epileptogenesis. Using high-resolution respirometry, we observed dynamic improvement of hippocampal mitochondrial respiration after kainic acid-injections in wild-type, but not in enkephalin-deficient mice. Thus, wild-type mice displayed higher efficiency in the use of mitochondrial capacity as compared to enkephalin-deficient mice. Our data demonstrate a Janus-headed role of enkephalin in epileptogenesis. In naive mice, enkephalin facilitates seizures, but in subsequent stages it contributes to neuronal survival through improved mitochondrial respiration.
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http://dx.doi.org/10.3389/fnmol.2018.00351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167428PMC
September 2018
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