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Proteasome Impairment Induces Recovery of Mitochondrial Membrane Potential and an Alternative Pathway of Mitochondrial Fusion. Mol Cell Biol 2015; 36:347-62. [PMID: 26552703 DOI: 10.1128/mcb.00920-15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/04/2015] [Indexed: 12/18/2022] Open
Abstract
Mitochondria are vital and highly dynamic organelles that continuously fuse and divide to maintain mitochondrial quality. Mitochondrial dysfunction impairs cellular integrity and is known to be associated with various human diseases. However, the mechanism by which the quality of mitochondria is maintained remains largely unexplored. Here we show that impaired proteasome function recovers the growth of yeast cells lacking Fzo1, a pivotal protein for mitochondrial fusion. Decreased proteasome activity increased the mitochondrial oxidoreductase protein Mia40 and the ratio of the short isoform of mitochondrial intermembrane protein Mgm1 (s-Mgm1) to the long isoform (l-Mgm1). The increase in Mia40 restored mitochondrial membrane potential, while the increase in the s-Mgm1/l-Mgm1 ratio promoted mitochondrial fusion in an Fzo1-independent manner. Our findings demonstrate a new pathway for mitochondrial quality control that is induced by proteasome impairment.
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Nolli C, Goffrini P, Lazzaretti M, Zanna C, Vitale R, Lodi T, Baruffini E. Validation of a MGM1/OPA1 chimeric gene for functional analysis in yeast of mutations associated with dominant optic atrophy. Mitochondrion 2015; 25:38-48. [PMID: 26455272 DOI: 10.1016/j.mito.2015.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/24/2015] [Accepted: 10/01/2015] [Indexed: 01/08/2023]
Abstract
Mutations in OPA1 are associated with DOA or DOA plus. Novel mutations in OPA1 are periodically identified, but often the causative effect of the mutation is not demonstrated. A chimeric protein containing the N-terminal region of Mgm1, the yeast orthologue of OPA1, and the C-terminal region of OPA1 was constructed. This chimeric construct can be exploited to evaluate the pathogenicity of most of the missense mutations in OPA1 as well as to determine whether the dominance of the mutation is due to haploinsufficiency or to gain of function.
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Affiliation(s)
- Cecilia Nolli
- Department of Life Sciences, University of Parma, Viale delle Scienze 11/A, 43124 Parma, Italy
| | - Paola Goffrini
- Department of Life Sciences, University of Parma, Viale delle Scienze 11/A, 43124 Parma, Italy
| | - Mirca Lazzaretti
- Department of Life Sciences, University of Parma, Viale delle Scienze 11/A, 43124 Parma, Italy
| | - Claudia Zanna
- Department of Pharmacy and Biotechnology (FABIT), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy; IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Rita Vitale
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari "Aldo Moro", Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Tiziana Lodi
- Department of Life Sciences, University of Parma, Viale delle Scienze 11/A, 43124 Parma, Italy
| | - Enrico Baruffini
- Department of Life Sciences, University of Parma, Viale delle Scienze 11/A, 43124 Parma, Italy.
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53
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Chen W, Xu X, Wang L, Bai G, Xiang W. Low Expression of Mfn2 Is Associated with Mitochondrial Damage and Apoptosis of Ovarian Tissues in the Premature Ovarian Failure Model. PLoS One 2015; 10:e0136421. [PMID: 26327438 PMCID: PMC4556514 DOI: 10.1371/journal.pone.0136421] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 08/03/2015] [Indexed: 11/18/2022] Open
Abstract
Background This study aimed to construct a working model for detecting the mitochondrial damage and expression of Mfn2. It furthermore explored the pathogenesis of premature ovarian failure (POF) induced by cisplatin. Method Forty young female mice were divided randomly into two groups. The first was the treatment group intraperitoneally administered cisplatin (1.5mg/kg). The untreated control group was likewise injected with physiological saline for 10 days. One month later, we observed the ovarian weight and morphological changes, particularly the development of follicles and concentration of sex hormones. Immunohistochemistry and western blotting were used to measure the two groups. We later evaluated ovarian cell apoptosis with TUNEL and analyzed Bcl-2 and Bax levels. We used transmission electron microscopy in order to observe the ultrastructure of ovarian cells. The phosphomolybdic acid colorimetric method was used to measure the ATP content in the ovarian tissue. Finally, the mitochondrial membrane potential of ovarian cells was detected with JC-1 dye. Results The cisplatin resulted in a decline of body weight, reduced ovarian weight significantly, and resulted in disorders of the extrous cycle. The follicles’ number decreased within the tissue’s stromal hyperplasia. Moreover, E2 levels were reduced, and elevated gonadotropin levels were observed. However, Mfn2 was present in the cell’s cytoplasm in both groups. Nevertheless, the Mfn2 levels and the expression of Bcl-2 were significantly decreased (p<0.05), but the expression of Bax and the apoptosis index (AI) was increased. In addition, the ATP levels (35.2 ±5.7μmol/g) of the control group were significantly higher (13.5 ± 3.8 μmol/g). Lastly, an obvious impairment of mitochondrial function and structure was observed. Conclusion The intreperitoneal injection of cisplatin, when administered for 10 days, establishes a POF model. Thus, the above results suggest that lower expression of Mfn2 may be involved in the mechanism of premature ovarian failure by affecting both the mitochondria’s energy metabolism and its apoptosis. This decides the termination of the follicles’ development.
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Affiliation(s)
- Wenqi Chen
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Xiaoyan Xu
- Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Lingjuan Wang
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Ge Bai
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Wenpei Xiang
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
- * E-mail:
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Abstract
Mitochondrial function is key for maintaining cellular health, while mitochondrial failure is associated with various pathologies, including inherited metabolic disorders and age-related diseases. In order to maintain mitochondrial quality, several pathways of mitochondrial quality control have evolved. These systems monitor mitochondrial integrity through antioxidants, DNA repair systems, and chaperones and proteases involved in the mitochondrial unfolded protein response. Additional regulation of mitochondrial function involves dynamic exchange of components through mitochondrial fusion and fission. Sustained stress induces a selective autophagy - termed mitophagy - and ultimately leads to apoptosis. Together, these systems form a network that acts on the molecular, organellar, and cellular level. In this review, we highlight how these systems are regulated in an integrated context- and time-dependent network of mitochondrial quality control that is implicated in healthy aging.
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Affiliation(s)
- Ntsiki M Held
- Laboratory Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, the Netherlands
| | - Riekelt H Houtkooper
- Laboratory Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, the Netherlands
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Rujiviphat J, Wong MK, Won A, Shih YL, Yip CM, McQuibban GA. Mitochondrial Genome Maintenance 1 (Mgm1) Protein Alters Membrane Topology and Promotes Local Membrane Bending. J Mol Biol 2015; 427:2599-609. [PMID: 25784211 DOI: 10.1016/j.jmb.2015.03.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 11/25/2022]
Abstract
Large GTPases of the dynamin superfamily promote membrane fusion and division, processes that are crucial for intracellular trafficking and organellar dynamics. To promote membrane scission, dynamin proteins polymerize, wrap around, and constrict the membrane; however, the mechanism underlying their role in membrane fusion remains unclear. We previously reported that the mitochondrial dynamin-related protein mitochondrial genome maintenance 1 (Mgm1) mediates fusion by first tethering opposing membranes and then undergoing a nucleotide-dependent structural transition. However, it is still unclear how Mgm1 directly affects the membrane to drive fusion of tethered membranes. Here, we show that Mgm1 association with the membrane alters the topography of the membrane, promoting local membrane bending. We also demonstrate that Mgm1 creates membrane ruffles resulting in the formation of tubular structures on both supported lipid bilayers and liposomes. These data suggest that Mgm1 membrane interactions impose a mechanical force on the membrane to overcome the hydrophilic repulsion of the phospholipid head groups and initiate the fusion reaction. The work reported here provides new insights into a possible mechanism of Mgm1-driven mitochondrial membrane fusion and sheds light into how members of the dynamin superfamily function as fusion molecules.
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Affiliation(s)
- Jarungjit Rujiviphat
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Michael K Wong
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
| | - Amy Won
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
| | - Yu-Ling Shih
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Christopher M Yip
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9; Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3E5
| | - G Angus McQuibban
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
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Effect of nicotinamide mononucleotide on brain mitochondrial respiratory deficits in an Alzheimer's disease-relevant murine model. BMC Neurol 2015; 15:19. [PMID: 25884176 PMCID: PMC4358858 DOI: 10.1186/s12883-015-0272-x] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 02/18/2015] [Indexed: 02/05/2023] Open
Abstract
Background Mitochondrial dysfunction is a hallmark of neurodegenerative diseases including Alzheimer’s disease (AD), with morphological and functional abnormalities limiting the electron transport chain and ATP production. A contributing factor of mitochondrial abnormalities is loss of nicotinamide adenine dinucleotide (NAD), an important cofactor in multiple metabolic reactions. Depletion of mitochondrial and consequently cellular NAD(H) levels by activated NAD glycohydrolases then culminates in bioenergetic failure and cell death. De Novo NAD+ synthesis from tryptophan requires a multi-step enzymatic reaction. Thus, an alternative strategy to maintain cellular NAD+ levels is to administer NAD+ precursors facilitating generation via a salvage pathway. We administered nicotinamide mononucleotide (NMN), an NAD+ precursor to APP(swe)/PS1(ΔE9) double transgenic (AD-Tg) mice to assess amelioration of mitochondrial respiratory deficits. In addition to mitochondrial respiratory function, we examined levels of full-length mutant APP, NAD+-dependent substrates (SIRT1 and CD38) in homogenates and fission/fusion proteins (DRP1, OPA1 and MFN2) in mitochondria isolated from brain. To examine changes in mitochondrial morphology, bigenic mice possessing a fluorescent protein targeted to neuronal mitochondria (CaMK2a-mito/eYFP), were administered NMN. Methods Mitochondrial oxygen consumption rates were examined in N2A neuroblastoma cells and non-synaptic brain mitochondria isolated from mice (3 months). Western blotting was utilized to assess APP, SIRT1, CD38, DRP1, OPA1 and MFN2 in brain of transgenic and non-transgenic mice (3–12 months). Mitochondrial morphology was assessed with confocal microscopy. One-way or two-way analysis of variance (ANOVA) and post-hoc Holm-Sidak method were used for statistical analyses of data. Student t-test was used for direct comparison of two groups. Results We now demonstrate that mitochondrial respiratory function was restored in NMN-treated AD-Tg mice. Levels of SIRT1 and CD38 change with age and NMN treatment. Furthermore, we found a shift in dynamics from fission to fusion proteins in the NMN-treated mice. Conclusions This is the first study to directly examine amelioration of NAD+ catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound. This might lead to well-defined physiologic abnormalities that can serve an important role in the validation of promising agents such as NMN that target NAD+ catabolism preserving mitochondrial function.
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57
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Ugarte-Uribe B, García-Sáez AJ. Membranes in motion: mitochondrial dynamics and their role in apoptosis. Biol Chem 2015; 395:297-311. [PMID: 24184992 DOI: 10.1515/hsz-2013-0234] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/31/2013] [Indexed: 11/15/2022]
Abstract
Mitochondrial dynamics is crucial for cell survival, development and homeostasis and impairment of these functions leads to neurologic disorders and metabolic diseases. The key components of mitochondrial dynamics have been identified. Mitofusins and OPA1 mediate mitochondrial fusion, whereas Drp1 is responsible for mitochondrial fission. In addition, an interplay between the proteins of the mitochondrial fission/fusion machinery and the Bcl-2 proteins, essential mediators in apoptosis, has been also described. Here, we review the molecular mechanisms regarding mitochondrial dynamics together with their role in apoptosis.
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58
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Gao AW, Cantó C, Houtkooper RH. Mitochondrial response to nutrient availability and its role in metabolic disease. EMBO Mol Med 2014; 6:580-9. [PMID: 24623376 PMCID: PMC4023882 DOI: 10.1002/emmm.201303782] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Metabolic inflexibility is defined as an impaired capacity to switch between different energy substrates and is a hallmark of insulin resistance and type 2 diabetes mellitus (T2DM). Hence, understanding the mechanisms underlying proper metabolic flexibility is key to prevent the development of metabolic disease and physiological deterioration. An important downstream player in the effects of metabolic flexibility is the mitochondrion. The objective of this review was to describe how mitochondrial metabolism adapts to limited nutrient situations or caloric excess by changes in mitochondrial function or biogenesis, as well as to define the mechanisms propelling these changes. Altogether, this should pinpoint key regulatory points by which metabolic flexibility might be ameliorated in situations of metabolic disease.
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Affiliation(s)
- Arwen W Gao
- Laboratory Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands
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59
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da Silva AF, Mariotti FR, Máximo V, Campello S. Mitochondria dynamism: of shape, transport and cell migration. Cell Mol Life Sci 2014; 71:2313-24. [PMID: 24442478 PMCID: PMC11113703 DOI: 10.1007/s00018-014-1557-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 12/06/2013] [Accepted: 01/02/2014] [Indexed: 10/25/2022]
Abstract
Mitochondria are highly dynamic and functionally versatile organelles that continuously fragment and fuse in response to different physiological needs of the cell. The list of proteins that strictly regulate the morphology of these organelles is constantly growing, adding new players every day and new pieces to the comprehension and elucidation of this complex machinery. The structural complexity of mitochondria is only paralled by their functional versatility. Indeed, changes in mitochondria shape play critical roles in vertebrate development programmed cell death and in various processes of normal cell physiology, such as calcium signaling, reactive oxygen species production, and lifespan. Here, we present the latest findings on the regulation of mitochondrial dynamics and some of their physiological roles, focusing on cell migration. In cells where migration represents a crucial function in their physiology, such as T and tumoral metastatic cells, mitochondria need to be fragmented and recruited to specific subcellular regions to make movement possible. In depth analysis of this role of mitochondrial dynamics should help in identifying potential targeted therapy against cancer or in improving the immune system's efficiency.
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Affiliation(s)
- André Ferreira da Silva
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), 4200 Porto, Portugal
- Department of Pathology and Oncology, Medical Faculty of the University of Porto, 4200 Porto, Portugal
| | - Francesca Romana Mariotti
- Laboratory of Mitochondrial Dynamics in Neuropathology, Department of Experimental Neuroscience, IRCCS Fondazione Santa Lucia, 00143 Rome, Italy
| | - Valdemar Máximo
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), 4200 Porto, Portugal
- Department of Pathology and Oncology, Medical Faculty of the University of Porto, 4200 Porto, Portugal
| | - Silvia Campello
- Laboratory of Mitochondrial Dynamics in Neuropathology, Department of Experimental Neuroscience, IRCCS Fondazione Santa Lucia, 00143 Rome, Italy
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60
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Hoppins S. The regulation of mitochondrial dynamics. Curr Opin Cell Biol 2014; 29:46-52. [PMID: 24747170 DOI: 10.1016/j.ceb.2014.03.005] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 03/18/2014] [Accepted: 03/19/2014] [Indexed: 11/17/2022]
Abstract
The structure of mitochondria is highly dynamic. Mitochondrial shape is cell-type specific and can be modified to meet changing requirements in energy production, calcium homeostasis, lipid biogenesis, fatty acid synthesis and other mitochondrial activities. This is achieved by modulating the dynamic properties of mitochondria including fusion, division, movement and positional tethering. It has become increasingly evident that mitochondrial dynamics also play an intimate role in several cellular signaling pathways and as such, many mechanisms have evolved to modulate mitochondrial structure. These regulatory mechanisms turn out to be important for modulation of mitochondrial-specific processes as well as cell, tissue and organism responses to developmental or environmental cues.
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Affiliation(s)
- Suzanne Hoppins
- Department of Biochemistry, University of Washington, Seattle, WA, United States
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61
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Lennon FE, Salgia R. Mitochondrial dynamics: biology and therapy in lung cancer. Expert Opin Investig Drugs 2014; 23:675-92. [PMID: 24654596 DOI: 10.1517/13543784.2014.899350] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Lung cancer mortality rates remain at unacceptably high levels. Although mitochondrial dysfunction is a characteristic of most tumor types, mitochondrial dynamics are often overlooked. Altered rates of mitochondrial fission and fusion are observed in lung cancer and can influence metabolic function, proliferation and cell survival. AREAS COVERED In this review, the authors outline the mechanisms of mitochondrial fission and fusion. They also identify key regulatory proteins and highlight the roles of fission and fusion in metabolism and other cellular functions (e.g., proliferation, apoptosis) with an emphasis on lung cancer and the interaction with known cancer biomarkers. They also examine the current therapeutic strategies reported as altering mitochondrial dynamics and review emerging mitochondria-targeted therapies. EXPERT OPINION Mitochondrial dynamics are an attractive target for therapeutic intervention in lung cancer. Mitochondrial dysfunction, despite its molecular heterogeneity, is a common abnormality of lung cancer. Targeting mitochondrial dynamics can alter mitochondrial metabolism, and many current therapies already non-specifically affect mitochondrial dynamics. A better understanding of mitochondrial dynamics and their interaction with currently identified cancer 'drivers' such as Kirsten-Rat Sarcoma Viral Oncogene homolog will lead to the development of novel therapeutics.
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Affiliation(s)
- Frances E Lennon
- University of Chicago, Department of Medicine, Section of Hematology/Oncology , 5841 S. Maryland Avenue, MC 2115 Chicago, IL 60637 , USA +1 773 702 4399 ; +1 773 834 1798 ;
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Anand R, Wai T, Baker MJ, Kladt N, Schauss AC, Rugarli E, Langer T. The i-AAA protease YME1L and OMA1 cleave OPA1 to balance mitochondrial fusion and fission. ACTA ACUST UNITED AC 2014; 204:919-29. [PMID: 24616225 PMCID: PMC3998800 DOI: 10.1083/jcb.201308006] [Citation(s) in RCA: 575] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
OPA1 processing by YEM1L and OMA1 is dispensable for mitochondrial fusion and instead drives mitochondrial fragmentation, which is crucial for mitochondrial integrity and quality control. Mitochondrial fusion and structure depend on the dynamin-like GTPase OPA1, whose activity is regulated by proteolytic processing. Constitutive OPA1 cleavage by YME1L and OMA1 at two distinct sites leads to the accumulation of both long and short forms of OPA1 and maintains mitochondrial fusion. Stress-induced OPA1 processing by OMA1 converts OPA1 completely into short isoforms, inhibits fusion, and triggers mitochondrial fragmentation. Here, we have analyzed the function of different OPA1 forms in cells lacking YME1L, OMA1, or both. Unexpectedly, deletion of Oma1 restored mitochondrial tubulation, cristae morphogenesis, and apoptotic resistance in cells lacking YME1L. Long OPA1 forms were sufficient to mediate mitochondrial fusion in these cells. Expression of short OPA1 forms promoted mitochondrial fragmentation, which indicates that they are associated with fission. Consistently, GTPase-inactive, short OPA1 forms partially colocalize with ER–mitochondria contact sites and the mitochondrial fission machinery. Thus, OPA1 processing is dispensable for fusion but coordinates the dynamic behavior of mitochondria and is crucial for mitochondrial integrity and quality control.
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Affiliation(s)
- Ruchika Anand
- Institute for Genetics, Center for Molecular Medicine (CMMC), and 2 Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
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63
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Escobar-Henriques M, Langer T. Dynamic survey of mitochondria by ubiquitin. EMBO Rep 2014; 15:231-43. [PMID: 24569520 PMCID: PMC3989689 DOI: 10.1002/embr.201338225] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 01/16/2014] [Accepted: 01/20/2014] [Indexed: 12/27/2022] Open
Abstract
Ubiquitin is a post-translational modifier with proteolytic and non-proteolytic roles in many biological processes. At mitochondria, it performs regulatory homeostatic functions and contributes to mitochondrial quality control. Ubiquitin is essential for mitochondrial fusion, regulates mitochondria-ER contacts, and participates in maternal mtDNA inheritance. Under stress, mitochondrial dysfunction induces ubiquitin-dependent responses that involve mitochondrial proteome remodeling and culminate in organelle removal by mitophagy. In addition, many ubiquitin-dependent mechanisms have been shown to regulate innate immune responses and xenophagy. Here, we review the emerging roles of ubiquitin at mitochondria.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Institute for Genetics, Centre for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of CologneCologne, Germany
| | - Thomas Langer
- Institute for Genetics, Centre for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of CologneCologne, Germany
- Max-Planck-Institute for the Biology of AgingCologne, Germany
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Abstract
Mitochondrial genes including Mfn2 are at the center of many diseases, underscoring their potential as a therapeutical target. The Chen group now identified 15-oxospiramilactone as a chemical inhibitor of the mammalian deubiquitylase USP30, acting on Mfn1 and Mfn2.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Institute for Genetics, Centre for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Zülpicher Str 47a, 50674 Cologne, Germany
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65
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del Campo A, Parra V, Vásquez-Trincado C, Gutiérrez T, Morales PE, López-Crisosto C, Bravo-Sagua R, Navarro-Marquez MF, Verdejo HE, Contreras-Ferrat A, Troncoso R, Chiong M, Lavandero S. Mitochondrial fragmentation impairs insulin-dependent glucose uptake by modulating Akt activity through mitochondrial Ca2+ uptake. Am J Physiol Endocrinol Metab 2014; 306:E1-E13. [PMID: 24085037 DOI: 10.1152/ajpendo.00146.2013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Insulin is a major regulator of glucose metabolism, stimulating its mitochondrial oxidation in skeletal muscle cells. Mitochondria are dynamic organelles that can undergo structural remodeling in order to cope with these ever-changing metabolic demands. However, the process by which mitochondrial morphology impacts insulin signaling in the skeletal muscle cells remains uncertain. To address this question, we silenced the mitochondrial fusion proteins Mfn2 and Opa1 and assessed insulin-dependent responses in L6 rat skeletal muscle cells. We found that mitochondrial fragmentation attenuates insulin-stimulated Akt phosphorylation, glucose uptake and cell respiratory rate. Importantly, we found that insulin induces a transient rise in mitochondrial Ca(2+) uptake, which was attenuated by silencing Opa1 or Mfn2. Moreover, treatment with Ruthenium red, an inhibitor of mitochondrial Ca(2+) uptake, impairs Akt signaling without affecting mitochondrial dynamics. All together, these results suggest that control of mitochondrial Ca(2+) uptake by mitochondrial morphology is a key event for insulin-induced glucose uptake.
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Affiliation(s)
- Andrea del Campo
- Advanced Center for Chronic Diseases (ACCDiSCEMC, Facultad Ciencias Químicas y Farmacéuticas y Facultad Medicina, Santiago, Chile
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Choi K, Park J, Lee J, Han EC, Choi C. Mutant ubiquitin attenuates interleukin-1β- and tumor necrosis factor-α-induced pro-inflammatory signaling in human astrocytic cells. PLoS One 2013; 8:e67891. [PMID: 23844119 PMCID: PMC3700915 DOI: 10.1371/journal.pone.0067891] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 05/22/2013] [Indexed: 01/18/2023] Open
Abstract
A frameshift mutation of ubiquitin called ubiquitin+1 (UBB+1) was found in the aging and Alzheimer’s disease brains and thought to be associated with neuronal dysfuction and degeneration. Even though ubiquitylation has been known to regulate vital cellular functions mainly through proteasome-dependent degradation of polyubiquitinated substrates, proteolysis-independent roles of ubiquitylation have emerged as key mechanisms in various signaling cascades. In this study, we have investigated the effect of UBB+1 on proinflammatory signaling such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in human astrocytes. Treatment with TNF-α and IL-1β induced expression of CCL2 and CXCL8 by human astrocytic cells; while ectopic expression of UBB+1 significantly abrogated the proinflammatory cytokine-induced expression of chemokines. Ectopic expression of UBB+1 suppressed TNF-α- and IL-1β-induced activation of NF-κB and JNK signaling pathway. Furthermore, we have demonstrated that polyubiquitylation of TRAFs and subsequent phosphorylation of TAK1 were significantly inhibited by stable expression of UBB+1. Collectively, these results suggest that UBB+1 may affect proinflammatory signaling in the central nervous system via inhibitory mechanisms of ubiquitin-dependent signaling in human astrocytes.
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Affiliation(s)
- Kyungsun Choi
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- * E-mail: (KC); (CC)
| | - Junseong Park
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- KI for the BioCentury, KAIST, Daejeon, Korea
| | - Jungsul Lee
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
| | - Eun Chun Han
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Korea
| | - Chulhee Choi
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- KI for the BioCentury, KAIST, Daejeon, Korea
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Korea
- * E-mail: (KC); (CC)
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Wiedemann N, Stiller SB, Pfanner N. Activation and degradation of mitofusins: two pathways regulate mitochondrial fusion by reversible ubiquitylation. Mol Cell 2013; 49:423-5. [PMID: 23395273 DOI: 10.1016/j.molcel.2013.01.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mitofusins are large GTPases essential for mitochondrial fusion. In this issue, Anton et al. (2013) report that two independent pathways of ubiquitylation/deubiquitylation control activation and degradation of mitofusins, revealing a sophisticated mechanism of regulating mitochondrial dynamics.
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Affiliation(s)
- Nils Wiedemann
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
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