51
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Kojima R, Kajiura S, Sesaki H, Endo T, Tamura Y. Identification of multi-copy suppressors for endoplasmic reticulum-mitochondria tethering proteins in Saccharomyces cerevisiae. FEBS Lett 2016; 590:3061-70. [PMID: 27531107 DOI: 10.1002/1873-3468.12358] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 07/16/2016] [Accepted: 08/09/2016] [Indexed: 11/08/2022]
Abstract
In yeast, the endoplasmic reticulum (ER)-mitochondria encounter structure (ERMES) tethers the ER to mitochondria, but its primary function remains unclear. To gain insight into ERMES functions, we screened multi-copy suppressors of the growth-defective phenotype of mmm1∆ cells, which lack a core component of ERMES, and identified MCP1, MGA2, SPT23, and YGR250C (termed RIE1). Spt23 and Mga2 are homologous transcription factors known to activate transcription of the OLE1 gene, which encodes the fatty acid ∆9 desaturase. We found that Ole1 partially relieves the growth defects of ERMES-lacking cells, thus uncovering a relationship between fatty acid metabolism and ERMES functions.
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Affiliation(s)
- Rieko Kojima
- Department of Chemistry, Graduate School of Science, Nagoya University, Japan.,Department of Material and Biological Science, Faculty of Science, Yamagata University, Japan
| | - Shu Kajiura
- Department of Chemistry, Graduate School of Science, Nagoya University, Japan
| | - Hiromi Sesaki
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Toshiya Endo
- Department of Chemistry, Graduate School of Science, Nagoya University, Japan. .,Faculty of Life Sciences, Kyoto Sangyo University, Japan. .,JST/CREST, Kyoto Sangyo University, Japan.
| | - Yasushi Tamura
- Department of Material and Biological Science, Faculty of Science, Yamagata University, Japan. .,Research Center for Materials Science, Nagoya University, Japan.
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52
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Ellenrieder L, Mårtensson CU, Becker T. Biogenesis of mitochondrial outer membrane proteins, problems and diseases. Biol Chem 2016; 396:1199-213. [PMID: 25980382 DOI: 10.1515/hsz-2015-0170] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 05/08/2015] [Indexed: 12/25/2022]
Abstract
Proteins of the mitochondrial outer membrane are synthesized as precursors on cytosolic ribosomes and sorted via internal targeting sequences to mitochondria. Two different types of integral outer membrane proteins exist: proteins with a transmembrane β-barrel and proteins embedded by a single or multiple α-helices. The import pathways of these two types of membrane proteins differ fundamentally. Precursors of β-barrel proteins are first imported across the outer membrane via the translocase of the outer membrane (TOM complex). The TOM complex is coupled to the sorting and assembly machinery (SAM complex), which catalyzes folding and membrane insertion of these precursors. The mitochondrial import machinery (MIM complex) promotes import of proteins with multiple α-helical membrane spans. Depending on the topology precursors of proteins with a single α-helical membrane anchor are imported via several distinct routes. We summarize current models and open questions of biogenesis of mitochondrial outer membrane proteins and discuss the impact of malfunctions of protein sorting on the development of diseases.
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53
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Smethurst DGJ, Cooper KF. ER fatalities-The role of ER-mitochondrial contact sites in yeast life and death decisions. Mech Ageing Dev 2016; 161:225-233. [PMID: 27507669 DOI: 10.1016/j.mad.2016.07.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/22/2016] [Accepted: 07/19/2016] [Indexed: 12/22/2022]
Abstract
Following extracellular stress signals, all eukaryotic cells choose whether to elicit a pro-survival or pro-death response. The decision over which path to take is governed by the severity and duration of the damage. In response to mild stress, pro-survival programs are initiated (unfolded protein response, autophagy, mitophagy) whereas severe or chronic stress forces the cell to abandon these adaptive programs and shift towards regulated cell death to remove irreversibly damaged cells. Both pro-survival and pro-death programs involve regulated communication between the endoplasmic reticulum (ER) and mitochondria. In yeast, recent data suggest this inter-organelle contact is facilitated by the endoplasmic reticulum mitochondria encounter structure (ERMES). These membrane contacts are not only important for the exchange of cellular signals, but also play a role in mitochondrial tethering during mitophagy, mitochondrial fission and mitochondrial inheritance. This review focuses on recent findings in yeast that shed light on how ER-mitochondrial communication mediates critical cell fate decisions.
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Affiliation(s)
- Daniel G J Smethurst
- Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Stratford, NJ, 08055 USA
| | - Katrina F Cooper
- Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Stratford, NJ, 08055 USA.
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54
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Bustos-Morán E, Blas-Rus N, Martín-Cófreces NB, Sánchez-Madrid F. Orchestrating Lymphocyte Polarity in Cognate Immune Cell-Cell Interactions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 327:195-261. [PMID: 27692176 DOI: 10.1016/bs.ircmb.2016.06.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The immune synapse (IS) is a specialized structure established between different immune cells that fulfills several functions, including a role as a communication bridge. This intimate contact between a T cell and an antigen-presenting cell promotes the proliferation and differentiation of lymphocytes involved in the contact. T-cell activation requires the specific triggering of the T-cell receptor (TCR), which promotes the activation of different signaling pathways inducing the polarization of the T cell. During this process, different adhesion and signaling receptors reorganize at specialized membrane domains, concomitantly to the polarization of the tubulin and actin cytoskeletons, forming stable polarization platforms. The centrosome also moves toward the IS, driving the movement of different organelles, such as the biosynthetic, secretory, degrading machinery, and mitochondria, to sustain T-cell activation. A proper orchestration of all these events is essential for T-cell effector functions and the accomplishment of a complete immune response.
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Affiliation(s)
- Eugenio Bustos-Morán
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain
| | - Noelia Blas-Rus
- Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
| | - Noa Beatriz Martín-Cófreces
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain.,Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
| | - Francisco Sánchez-Madrid
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain.,Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
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55
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Dimmer KS, Rapaport D. Mitochondrial contact sites as platforms for phospholipid exchange. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:69-80. [PMID: 27477677 DOI: 10.1016/j.bbalip.2016.07.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/21/2016] [Accepted: 07/22/2016] [Indexed: 12/15/2022]
Abstract
Mitochondria are unique organelles that contain their own - although strongly reduced - genome, and are surrounded by two membranes. While most cellular phospholipid biosynthesis takes place in the ER, mitochondria harbor the whole spectrum of glycerophospholipids common to biological membranes. Mitochondria also contribute to overall phospholipid biosynthesis in cells by producing phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. Considering these features, it is not surprising that mitochondria maintain highly active exchange of phospholipids with other cellular compartments. In this contribution we describe the transport of phospholipids between mitochondria and other organelles, and discuss recent developments in our understanding of the molecular functions of the protein complexes that mediate these processes. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.
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Affiliation(s)
- Kai Stefan Dimmer
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
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56
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Mechanism of impaired microtubule-dependent peroxisome trafficking and oxidative stress in SPAST-mutated cells from patients with Hereditary Spastic Paraplegia. Sci Rep 2016; 6:27004. [PMID: 27229699 PMCID: PMC4882512 DOI: 10.1038/srep27004] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/12/2016] [Indexed: 12/23/2022] Open
Abstract
Hereditary spastic paraplegia (HSP) is an inherited neurological condition that leads to progressive spasticity and gait abnormalities. Adult-onset HSP is most commonly caused by mutations in SPAST, which encodes spastin a microtubule severing protein. In olfactory stem cell lines derived from patients carrying different SPAST mutations, we investigated microtubule-dependent peroxisome movement with time-lapse imaging and automated image analysis. The average speed of peroxisomes in patient-cells was slower, with fewer fast moving peroxisomes than in cells from healthy controls. This was not because of impairment of peroxisome-microtubule interactions because the time-dependent saltatory dynamics of movement of individual peroxisomes was unaffected in patient-cells. Our observations indicate that average peroxisome speeds are less in patient-cells because of the lower probability of individual peroxisome interactions with the reduced numbers of stable microtubules: peroxisome speeds in patient cells are restored by epothilone D, a tubulin-binding drug that increases the number of stable microtubules to control levels. Patient-cells were under increased oxidative stress and were more sensitive than control-cells to hydrogen peroxide, which is primarily metabolised by peroxisomal catalase. Epothilone D also ameliorated patient-cell sensitivity to hydrogen-peroxide. Our findings suggest a mechanism for neurodegeneration whereby SPAST mutations indirectly lead to impaired peroxisome transport and oxidative stress.
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57
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Sinzel M, Tan T, Wendling P, Kalbacher H, Özbalci C, Chelius X, Westermann B, Brügger B, Rapaport D, Dimmer KS. Mcp3 is a novel mitochondrial outer membrane protein that follows a unique IMP-dependent biogenesis pathway. EMBO Rep 2016; 17:965-81. [PMID: 27226123 DOI: 10.15252/embr.201541273] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 04/26/2016] [Indexed: 11/09/2022] Open
Abstract
Mitochondria are separated from the remainder of the eukaryotic cell by the mitochondrial outer membrane (MOM). The MOM plays an important role in different transport processes like lipid trafficking and protein import. In yeast, the ER-mitochondria encounter structure (ERMES) has a central, but poorly defined role in both activities. To understand the functions of the ERMES, we searched for suppressors of the deficiency of one of its components, Mdm10, and identified a novel mitochondrial protein that we named Mdm10 complementing protein 3 (Mcp3). Mcp3 partially rescues a variety of ERMES-related phenotypes. We further demonstrate that Mcp3 is an integral protein of the MOM that follows a unique import pathway. It is recognized initially by the import receptor Tom70 and then crosses the MOM via the translocase of the outer membrane. Mcp3 is next relayed to the TIM23 translocase at the inner membrane, gets processed by the inner membrane peptidase (IMP) and finally integrates into the MOM. Hence, Mcp3 follows a novel biogenesis route where a MOM protein is processed by a peptidase of the inner membrane.
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Affiliation(s)
- Monika Sinzel
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Tao Tan
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Philipp Wendling
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Hubert Kalbacher
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Cagakan Özbalci
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Xenia Chelius
- Cell Biology, University of Bayreuth, Bayreuth, Germany
| | | | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Kai Stefan Dimmer
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
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58
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Wu W, Lin C, Wu K, Jiang L, Wang X, Li W, Zhuang H, Zhang X, Chen H, Li S, Yang Y, Lu Y, Wang J, Zhu R, Zhang L, Sui S, Tan N, Zhao B, Zhang J, Li L, Feng D. FUNDC1 regulates mitochondrial dynamics at the ER-mitochondrial contact site under hypoxic conditions. EMBO J 2016; 35:1368-84. [PMID: 27145933 DOI: 10.15252/embj.201593102] [Citation(s) in RCA: 242] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 03/31/2016] [Indexed: 01/15/2023] Open
Abstract
In hypoxic cells, dysfunctional mitochondria are selectively removed by a specialized autophagic process called mitophagy. The ER-mitochondrial contact site (MAM) is essential for fission of mitochondria prior to engulfment, and the outer mitochondrial membrane protein FUNDC1 interacts with LC3 to recruit autophagosomes, but the mechanisms integrating these processes are poorly understood. Here, we describe a new pathway mediating mitochondrial fission and subsequent mitophagy under hypoxic conditions. FUNDC1 accumulates at the MAM by associating with the ER membrane protein calnexin. As mitophagy proceeds, FUNDC1/calnexin association attenuates and the exposed cytosolic loop of FUNDC1 interacts with DRP1 instead. DRP1 is thereby recruited to the MAM, and mitochondrial fission then occurs. Knockdown of FUNDC1, DRP1, or calnexin prevents fission and mitophagy under hypoxic conditions. Thus, FUNDC1 integrates mitochondrial fission and mitophagy at the interface of the MAM by working in concert with DRP1 and calnexin under hypoxic conditions in mammalian cells.
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Affiliation(s)
- Wenxian Wu
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Chunxia Lin
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Keng Wu
- Department of Cardiovasology, The Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Lei Jiang
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China Guangdong General Hospital, Guangdong Academy of Medical Sciences, Southern Medical University, Guangzhou, China
| | - Xiaojing Wang
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China College of Life Science and Technology, Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, China
| | - Wen Li
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Haixia Zhuang
- Department of Anesthesiology, Guangdong Medical University, Zhanjiang, China
| | - Xingliang Zhang
- Department of Pediatrics, Guangdong Medical University, Zhanjiang, China
| | - Hao Chen
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Shupeng Li
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Yue Yang
- Department of Anesthesiology, Guangdong Medical University, Zhanjiang, China
| | - Yue Lu
- Department of Anesthesiology, Guangdong Medical University, Zhanjiang, China
| | - Jingjing Wang
- Department of Anesthesiology, Guangdong Medical University, Zhanjiang, China
| | - Runzhi Zhu
- Laboratory of Hepatobiliary Surgery, Zhanjiang Key Laboratory of Hepatobiliary Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Liangqing Zhang
- Department of Anesthesiology, Guangdong Medical University, Zhanjiang, China
| | - Senfang Sui
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ning Tan
- Guangdong General Hospital, Guangdong Academy of Medical Sciences, Southern Medical University, Guangzhou, China
| | - Bin Zhao
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Jingjing Zhang
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China
| | - Longxuan Li
- Department of Neurology, Gongli Hospital, Pudong New Area, Shanghai, China
| | - Du Feng
- Guangdong Key Laboratory of Age-related Cardiac-cerebral Vascular Disease, Department of Neurology, Institute of Neurology, The Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, China Department of Developmental Biology, Harvard School of Dental Medicine, Harvard Medical School, Boston, MA, USA
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59
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Beach A, Richard VR, Bourque S, Boukh-Viner T, Kyryakov P, Gomez-Perez A, Arlia-Ciommo A, Feldman R, Leonov A, Piano A, Svistkova V, Titorenko VI. Lithocholic bile acid accumulated in yeast mitochondria orchestrates a development of an anti-aging cellular pattern by causing age-related changes in cellular proteome. Cell Cycle 2016; 14:1643-56. [PMID: 25839782 DOI: 10.1080/15384101.2015.1026493] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have previously revealed that exogenously added lithocholic bile acid (LCA) extends the chronological lifespan of the yeast Saccharomyces cerevisiae, accumulates in mitochondria and alters mitochondrial membrane lipidome. Here, we use quantitative mass spectrometry to show that LCA alters the age-related dynamics of changes in levels of many mitochondrial proteins, as well as numerous proteins in cellular locations outside of mitochondria. These proteins belong to 2 regulons, each modulated by a different mitochondrial dysfunction; we call them a partial mitochondrial dysfunction regulon and an oxidative stress regulon. We found that proteins constituting these regulons (1) can be divided into several "clusters", each of which denotes a distinct type of partial mitochondrial dysfunction that elicits a different signaling pathway mediated by a discrete set of transcription factors; (2) exhibit 3 different patterns of the age-related dynamics of changes in their cellular levels; and (3) are encoded by genes whose expression is regulated by the transcription factors Rtg1p/Rtg2p/Rtg3p, Sfp1p, Aft1p, Yap1p, Msn2p/Msn4p, Skn7p and Hog1p, each of which is essential for longevity extension by LCA. Our findings suggest that LCA-driven changes in mitochondrial lipidome alter mitochondrial proteome and functionality, thereby enabling mitochondria to operate as signaling organelles that orchestrate an establishment of an anti-aging transcriptional program for many longevity-defining nuclear genes. Based on these findings, we propose a model for how such LCA-driven changes early and late in life of chronologically aging yeast cause a stepwise development of an anti-aging cellular pattern and its maintenance throughout lifespan.
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Key Words
- D, diauxic growth phase
- DMSO, dimethyl sulfoxide
- ER, endoplasmic reticulum
- ETC, electron transport chain
- ISC, iron-sulfur clusters
- LCA, lithocholic acid
- MAM, mitochondria-associated membrane
- OS, oxidative stress
- PD, post-diauxic growth phase
- PMD, partial mitochondrial dysfunction
- ROS, reactive oxygen species
- ST, stationary growth phase
- TCA, tricarboxylic acid
- WT, wild type
- anti-aging compounds
- cell metabolism
- cellular aging
- lithocholic bile acid
- longevity
- mitochondria
- mitochondrial proteome
- mitochondrial signaling
- signal transduction
- yeast
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Affiliation(s)
- Adam Beach
- a Department of Biology; Concordia University ; Montreal , QC , Canada
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60
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Cross Talk of Proteostasis and Mitostasis in Cellular Homeodynamics, Ageing, and Disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:4587691. [PMID: 26977249 PMCID: PMC4763003 DOI: 10.1155/2016/4587691] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 12/24/2015] [Accepted: 12/31/2015] [Indexed: 12/26/2022]
Abstract
Mitochondria are highly dynamic organelles that provide essential metabolic functions and represent the major bioenergetic hub of eukaryotic cell. Therefore, maintenance of mitochondria activity is necessary for the proper cellular function and survival. To this end, several mechanisms that act at different levels and time points have been developed to ensure mitochondria quality control. An interconnected highly integrated system of mitochondrial and cytosolic chaperones and proteases along with the fission/fusion machinery represents the surveillance scaffold of mitostasis. Moreover, nonreversible mitochondrial damage targets the organelle to a specific autophagic removal, namely, mitophagy. Beyond the organelle dynamics, the constant interaction with the ubiquitin-proteasome-system (UPS) has become an emerging aspect of healthy mitochondria. Dysfunction of mitochondria and UPS increases with age and correlates with many age-related diseases including cancer and neurodegeneration. In this review, we discuss the functional cross talk of proteostasis and mitostasis in cellular homeodynamics and the impairment of mitochondrial quality control during ageing, cancer, and neurodegeneration.
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61
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The TULIP superfamily of eukaryotic lipid-binding proteins as a mediator of lipid sensing and transport. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:913-923. [PMID: 26825693 DOI: 10.1016/j.bbalip.2016.01.016] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 01/16/2016] [Accepted: 01/25/2016] [Indexed: 01/28/2023]
Abstract
The tubular lipid-binding (TULIP) superfamily has emerged in recent years as a major mediator of lipid sensing and transport in eukaryotes. It currently encompasses three protein families, SMP-like, BPI-like, and Takeout-like, which share a common fold. This fold consists of a long helix wrapped in a highly curved anti-parallel β-sheet, enclosing a central, lipophilic cavity. The SMP-like proteins, which include subunits of the ERMES complex and the extended synaptotagmins (E-Syts), appear to be mainly located at membrane contacts sites (MCSs) between organelles, mediating inter-organelle lipid exchange. The BPI-like proteins, which include the bactericidal/permeability-increasing protein (BPI), the LPS (lipopolysaccharide)-binding protein (LBP), the cholesteryl ester transfer protein (CETP), and the phospholipid transfer protein (PLTP), are either involved in innate immunity against bacteria through their ability to sense lipopolysaccharides, as is the case for BPI and LBP, or in lipid exchange between lipoprotein particles, as is the case for CETP and PLTP. The Takeout-like proteins, which are comprised of insect juvenile hormone-binding proteins and arthropod allergens, transport, where known, lipid hormones to target tissues during insect development. In all cases, the activity of these proteins is underpinned by their ability to bind large, hydrophobic ligands in their central cavity and segregate them away from the aqueous environment. Furthermore, where they are involved in lipid exchange, recent structural studies have highlighted their ability to establish lipophilic, tubular channels, either between organelles in the case of SMP domains or between lipoprotein particles in the case of CETP. Here, we review the current knowledge on the structure, versatile functions, and evolution of the TULIP superfamily. We propose a deep evolutionary split in this superfamily, predating the Last Eukaryotic Common Ancestor, between the SMP-like proteins, which act on lipids endogenous to the cell, and the BPI-like proteins (including the Takeout-like proteins of arthropods), which act on exogenous lipids. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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62
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Klecker T, Wemmer M, Haag M, Weig A, Böckler S, Langer T, Nunnari J, Westermann B. Interaction of MDM33 with mitochondrial inner membrane homeostasis pathways in yeast. Sci Rep 2015; 5:18344. [PMID: 26669658 PMCID: PMC4680886 DOI: 10.1038/srep18344] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 11/16/2015] [Indexed: 12/31/2022] Open
Abstract
Membrane homeostasis affects mitochondrial dynamics, morphology, and function. Here we report genetic and proteomic data that reveal multiple interactions of Mdm33, a protein essential for normal mitochondrial structure, with components of phospholipid metabolism and mitochondrial inner membrane homeostasis. We screened for suppressors of MDM33 overexpression-induced growth arrest and isolated binding partners by immunoprecipitation of cross-linked cell extracts. These approaches revealed genetic and proteomic interactions of Mdm33 with prohibitins, Phb1 and Phb2, which are key components of mitochondrial inner membrane homeostasis. Lipid profiling by mass spectrometry of mitochondria isolated from Mdm33-overexpressing cells revealed that high levels of Mdm33 affect the levels of phosphatidylethanolamine and cardiolipin, the two key inner membrane phospholipids. Furthermore, we show that cells lacking Mdm33 show strongly decreased mitochondrial fission activity indicating that Mdm33 is critical for mitochondrial membrane dynamics. Our data suggest that MDM33 functionally interacts with components important for inner membrane homeostasis and thereby supports mitochondrial division.
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Affiliation(s)
- Till Klecker
- Universität Bayreuth, Zellbiologie, 95440 Bayreuth, Germany
| | - Megan Wemmer
- University of California Davis, Department of Molecular and Cellular Biology, Davis, CA 95616, USA
| | - Mathias Haag
- Universität zu Köln, Institut für Genetik, 50931 Köln, Germany
| | - Alfons Weig
- Universität Bayreuth, DNA Analytik, 95440 Bayreuth, Germany
| | - Stefan Böckler
- Universität Bayreuth, Zellbiologie, 95440 Bayreuth, Germany
| | - Thomas Langer
- Universität zu Köln, Institut für Genetik, 50931 Köln, Germany
| | - Jodi Nunnari
- University of California Davis, Department of Molecular and Cellular Biology, Davis, CA 95616, USA
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63
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Kentala H, Weber-Boyvat M, Olkkonen VM. OSBP-Related Protein Family: Mediators of Lipid Transport and Signaling at Membrane Contact Sites. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 321:299-340. [PMID: 26811291 DOI: 10.1016/bs.ircmb.2015.09.006] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Oxysterol-binding protein (OSBP) and its related protein homologs, ORPs, constitute a conserved family of lipid-binding/transfer proteins (LTPs) expressed ubiquitously in eukaryotes. The ligand-binding domain of ORPs accommodates cholesterol and oxysterols, but also glycerophospholipids, particularly phosphatidylinositol-4-phosphate (PI4P). ORPs have been implicated as intracellular lipid sensors or transporters. Most ORPs carry targeting determinants for the endoplasmic reticulum (ER) and non-ER organelle membrane. ORPs are located and function at membrane contact sites (MCSs), at which ER is closely apposed with other organelle limiting membranes. Such sites have roles in lipid transport and metabolism, control of Ca(2+) fluxes, and signaling events. ORPs are postulated either to transport lipids over MCSs to maintain the distinct lipid compositions of organelle membranes, or to control the activity of enzymes/protein complexes with functions in signaling and lipid metabolism. ORPs may transfer PI4P and another lipid class bidirectionally. Transport of PI4P followed by its hydrolysis would in this model provide the energy for transfer of the other lipid against its concentration gradient. Control of organelle lipid compositions by OSBP/ORPs is important for the life cycles of several pathogenic viruses. Targeting ORPs with small-molecular antagonists is proposed as a new strategy to combat viral infections. Several ORPs are reported to modulate vesicle transport along the secretory or endocytic pathways. Moreover, antagonists of certain ORPs inhibit cancer cell proliferation. Thus, ORPs are LTPs, which mediate interorganelle lipid transport and coordinate lipid signals with a variety of cellular regimes.
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Affiliation(s)
- Henriikka Kentala
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Helsinki, Finland
| | - Marion Weber-Boyvat
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Helsinki, Finland
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64
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Olkkonen VM. OSBP-Related Protein Family in Lipid Transport Over Membrane Contact Sites. Lipid Insights 2015; 8:1-9. [PMID: 26715851 PMCID: PMC4685180 DOI: 10.4137/lpi.s31726] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/03/2015] [Accepted: 09/06/2015] [Indexed: 12/12/2022] Open
Abstract
Increasing evidence suggests that oxysterol-binding protein-related proteins (ORPs) localize at membrane contact sites, which are high-capacity platforms for inter-organelle exchange of small molecules and information. ORPs can simultaneously associate with the two apposed membranes and transfer lipids across the interbilayer gap. Oxysterol-binding protein moves cholesterol from the endoplasmic reticulum to trans-Golgi, driven by the retrograde transport of phosphatidylinositol-4-phosphate (PI4P). Analogously, yeast Osh6p mediates the transport of phosphatidylserine from the endoplasmic reticulum to the plasma membrane in exchange for PI4P, and ORP5 and -8 are suggested to execute similar functions in mammalian cells. ORPs may share the capacity to bind PI4P within their ligand-binding domain, prompting the hypothesis that bidirectional transport of a phosphoinositide and another lipid may be a common theme among the protein family. This model, however, needs more experimental support and does not exclude a function of ORPs in lipid signaling.
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Affiliation(s)
- Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Helsinki, Finland. ; Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
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65
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van Bergeijk P, Hoogenraad CC, Kapitein LC. Right Time, Right Place: Probing the Functions of Organelle Positioning. Trends Cell Biol 2015; 26:121-134. [PMID: 26541125 DOI: 10.1016/j.tcb.2015.10.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/30/2015] [Accepted: 10/01/2015] [Indexed: 10/22/2022]
Abstract
The proper spatial arrangement of organelles underlies many cellular processes including signaling, polarization, and growth. Despite the importance of local positioning, the precise connection between subcellular localization and organelle function is often not fully understood. To address this, recent studies have developed and employed different strategies to directly manipulate organelle distributions, such as the use of (light-sensitive) heterodimerization to control the interaction between selected organelles and specific motor proteins, adaptor molecules, or anchoring factors. We review here the importance of subcellular localization as well as tools to control local organelle positioning. Because these approaches allow spatiotemporal control of organelle distribution, they will be invaluable tools to unravel local functioning and the mechanisms that control positioning.
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Affiliation(s)
- Petra van Bergeijk
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Lukas C Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
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66
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Knoblach B, Rachubinski RA. Motors, anchors, and connectors: orchestrators of organelle inheritance. Annu Rev Cell Dev Biol 2015; 31:55-81. [PMID: 26443192 DOI: 10.1146/annurev-cellbio-100814-125553] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Organelle inheritance is a process whereby organelles are actively distributed between dividing cells at cytokinesis. Much valuable insight into the molecular mechanisms of organelle inheritance has come from the analysis of asymmetrically dividing cells, which transport a portion of their organelles to the bud while retaining another portion in the mother cell. Common principles apply to the inheritance of all organelles, although individual organelles use specific factors for their partitioning. Inheritance factors can be classified as motors, which are required for organelle transport; anchors, which immobilize organelles at distinct cell structures; or connectors, which mediate the attachment of organelles to motors and anchors. Here, we provide an overview of recent advances in the field of organelle inheritance and highlight how motor, anchor, and connector molecules choreograph the segregation of a multicopy organelle, the peroxisome. We also discuss the role of organelle population control in the generation of cellular diversity.
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Affiliation(s)
- Barbara Knoblach
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada;
| | - Richard A Rachubinski
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada;
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67
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Abstract
Mitochondria are the powerhouse of cells as they produce the bulk of ATP which is consumed by the cell. They form a highly interconnected network that is governed by fission and fusion processes. In addition, mitochondria and the endoplasmic reticulum (ER) are found in close proximity to each other and it is thought that they maintain contact sites to exchange molecules. The regulation and the function of these contact sites need to be further explored. The small GTPase Arf1 (ADP-ribosylation factor 1), which is best known for its essential role in the generation of coatomer protein I (COPI)-coated vesicles at the Golgi complex appears to be also essential for the dynamics and maintenance of mitochondrial function, presumably at ER-mitochondrial contact sites.
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68
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Wang WX, Springer JE. Role of mitochondria in regulating microRNA activity and its relevance to the central nervous system. Neural Regen Res 2015; 10:1026-8. [PMID: 26330811 PMCID: PMC4541219 DOI: 10.4103/1673-5374.160061] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2015] [Indexed: 12/19/2022] Open
Affiliation(s)
- Wang-Xia Wang
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Joe E Springer
- Physical Medicine and Rehabilitation, Spinal Cord and Brain Injury Research Center, Anatomy and Neurobiology, University of Kentucky, Lexington, KY, USA
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69
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Aufschnaiter A, Büttner S. Peroxisomal fission controls yeast life span. Cell Cycle 2015; 14:2389-90. [PMID: 26103158 PMCID: PMC5038852 DOI: 10.1080/15384101.2015.1063303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 05/06/2015] [Indexed: 10/23/2022] Open
Affiliation(s)
- Andreas Aufschnaiter
- Institute of Molecular Biosciences; NAWI Graz; University of Graz; Graz, Austria
| | - Sabrina Büttner
- Institute of Molecular Biosciences; NAWI Graz; University of Graz; Graz, Austria
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70
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Westermann B. The mitochondria–plasma membrane contact site. Curr Opin Cell Biol 2015; 35:1-6. [DOI: 10.1016/j.ceb.2015.03.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 02/24/2015] [Accepted: 03/05/2015] [Indexed: 12/20/2022]
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71
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Picard M. Mitochondrial synapses: intracellular communication and signal integration. Trends Neurosci 2015; 38:468-74. [PMID: 26187720 DOI: 10.1016/j.tins.2015.06.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 12/17/2022]
Abstract
Communication is a central theme in biology. Consequently, specialized structures have evolved to permit rapid communication among cells, tissues, organs, and physiological systems, thus enhancing the overall function and adaptation of the organism. A prime example is the neuronal synapse. In the brain, synaptic communication establishes neuronal networks with the capacity to integrate, process, and store information, giving rise to complex output signals capable of orchestrating functions across the organism. At the intracellular level, discoveries now reveal the existence of 'mitochondrial synapses' establishing mitochondrial networks, with defined chromatin-modifying mitochondrial output signals capable of orchestrating gene expression across the genome. These discoveries raise the possibility that in addition to their role as powerhouses and neuromodulators, mitochondria behave as intracellular signal-processing networks.
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Affiliation(s)
- Martin Picard
- Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia and the University of Pennsylvania, PA 19104, USA.
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72
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Kentala H, Pfisterer SG, Olkkonen VM, Weber-Boyvat M. Sterol liganding of OSBP-related proteins (ORPs) regulates the subcellular distribution of ORP-VAPA complexes and their impacts on organelle structure. Steroids 2015; 99:248-58. [PMID: 25681634 DOI: 10.1016/j.steroids.2015.01.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/21/2015] [Accepted: 01/22/2015] [Indexed: 01/20/2023]
Abstract
Oxysterol-binding protein (OSBP) and its homologues (ORPs) are lipid-binding/transfer proteins with affinity for oxysterols, cholesterol and glycerophospholipids. In addition to a ligand-binding domain, a majority of the ORPs carry a pleckstrin homology domain that targets organelle membranes via phosphoinositides, and a motif targeting the endoplasmic reticulum (ER) via VAMP-associated proteins (VAPs). We employed here Bimolecular Fluorescence Complementation (BiFC) to systematically assess the effects of sterol manipulation of HuH7 cells on complexes of established sterol-binding ORPs with their ER receptor, VAMP-associated protein A (VAPA). Depletion of cellular cholesterol with lipoprotein-deficient medium and Mevastatin caused concentration of OSBP-VAPA complexes and Golgi complex markers at a juxtanuclear position, an effect reversed by low-density lipoprotein treatment. A similar redistribution of OSBP-VAPA but not of sterol-binding deficient mutant OSBP(ΔELSK)-VAPA, occurred upon treatment with the high-affinity ligand, 25-hydroxycholesterol (25OHC), which reduced total and free cholesterol. ORP2-VAPA complexes, which localize in untreated cells at blob-like ER structures with associated lipid droplets, were redistributed upon treatment with the ORP2 ligand 22(R)OHC to a diffuse cytoplasmic/ER pattern and the plasma membrane. Analogously, distribution of ORP4L-VAPA complexes between the plasma membrane and vimentin intermediate filament associated compartments was modified by statin or 25OHC treatment. The treatments resulted in loss of vimentin co-localization, and sterol-binding deficient ORP4L(ΔELSR)-VAPA localized predominantly to the plasma membrane. In conclusion, treatment with statin or oxysterol ligands modify the subcellular targeting of ORP-VAPA complexes, consistent with the notion that this machinery controls lipid homeostasis and signaling at organelle interfaces.
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Affiliation(s)
- Henriikka Kentala
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland
| | - Simon G Pfisterer
- Institute of Biomedicine, Anatomy, FI-00014 University of Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland; Institute of Biomedicine, Anatomy, FI-00014 University of Helsinki, Finland
| | - Marion Weber-Boyvat
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland.
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73
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Zhang ZY, Fan ZK, Cao Y, Jia ZQ, Li G, Zhi XD, Yu DS, Lv G. Acetyl-L-carnitineameliorates mitochondrial damage and apoptosis following spinal cord injury in rats. Neurosci Lett 2015; 604:18-23. [PMID: 26079325 DOI: 10.1016/j.neulet.2015.06.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 05/28/2015] [Accepted: 06/09/2015] [Indexed: 10/23/2022]
Abstract
Acetyl-l-carnitine (ALC) facilitates the entry and exit of fatty acids from mitochondria and plays an essential role in energy metabolism. Although ALC is known to exert neuroprotective effects in multiple neurological diseases, its effects on spinal cord injury (SCI)-induced mitochondrial impairments and apoptosis remain unclear. In this study, we aimed to evaluate the putative effects of ALC on mitochondrial dysfunction and apoptosis induced by SCI in a rodent model. Our results indicate that SCI elicits dynamic alternations in the expression of mitochondria-related proteins. Transmission electron microscopy analysis showed that ALC administration abrogated key ultrastructural abnormalities in mitochondria at 24h after SCI by maintaining mitochondrial length, reducing the number of damaged mitochondria, and reversing mitochondrial score (P<0.05 compared with SCI group). In addition, ALC administration maintained the mitochondrial membrane potential and mitochondrial Na(+)-K(+)-ATPase activity following SCI (P<0.05 compared with SCI group). ALC administration reversed the downregulation of mitofusin 1 (Mfn1), Mfn2, Bcl-2, and the upregulation of dynamin-related protein 1 (Drp1), mitochondrial fission 1 (Fis1), Bcl-2-associated X protein (Bax) and cytosol cytochrome c (cyto-CytC) induced by SCI (P<0.05 compared with SCI group). Finally ALC administration greatly reduced the percentage of apoptotic cells compared with the SCI group (P<0.01). In conclusion, our findings demonstrated that ALC ameliorated SCI-induced mitochondrial structural alternations, mitochondrial dysfunction, and apoptosis.
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Affiliation(s)
- Zhen-yu Zhang
- Department of Orthopaedics, The First Affiliated Hospital, China Medical University, Shenyang 110001, Liaoning Province, China
| | - Zhong-kai Fan
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - Yang Cao
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - Zhi-qiang Jia
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - Gang Li
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - Xiao-dong Zhi
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - De-shui Yu
- Department of Orthopaedics, The First Affiliated Hospital, Liaoning Medical University, Jinzhou 121000, Liaoning Province, China
| | - Gang Lv
- Department of Orthopaedics, The First Affiliated Hospital, China Medical University, Shenyang 110001, Liaoning Province, China.
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74
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Weber-Boyvat M, Kentala H, Peränen J, Olkkonen VM. Ligand-dependent localization and function of ORP-VAP complexes at membrane contact sites. Cell Mol Life Sci 2015; 72:1967-87. [PMID: 25420878 PMCID: PMC11114005 DOI: 10.1007/s00018-014-1786-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 10/17/2014] [Accepted: 11/17/2014] [Indexed: 01/08/2023]
Abstract
Oxysterol-binding protein/OSBP-related proteins (ORPs) constitute a conserved family of sterol/phospholipid-binding proteins with lipid transporter or sensor functions. We investigated the spatial occurrence and regulation of the interactions of human OSBP/ORPs or the S. cerevisiae orthologs, the Osh (OSBP homolog) proteins, with their endoplasmic reticulum (ER) anchors, the VAMP-associated proteins (VAPs), by employing bimolecular fluorescence complementation and pull-down set-ups. The ORP-VAP interactions localize frequently at distinct subcellular sites, shown in several cases to represent membrane contact sites (MCSs). Using established ORP ligand-binding domain mutants and pull-down assays with recombinant proteins, we show that ORP liganding regulates the ORP-VAP association, alters the subcellular targeting of ORP-VAP complexes, or modifies organelle morphology. There is distinct protein specificity in the effects of the mutants on subcellular targeting of ORP-VAP complexes. We provide evidence that complexes of human ORP2 and VAPs at ER-lipid droplet interfaces regulate the hydrolysis of triglycerides and lipid droplet turnover. The data suggest evolutionarily conserved, complex ligand-dependent functions of ORP-VAP complexes at MCSs, with implications for cellular lipid homeostasis and signaling.
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Affiliation(s)
- Marion Weber-Boyvat
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Henriikka Kentala
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Johan Peränen
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Vesa M. Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, Tukholmankatu 8, 00290 Helsinki, Finland
- Institute of Biomedicine, Anatomy, University of Helsinki, 00014 Helsinki, Finland
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75
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Giorgi C, Missiroli S, Patergnani S, Duszynski J, Wieckowski MR, Pinton P. Mitochondria-associated membranes: composition, molecular mechanisms, and physiopathological implications. Antioxid Redox Signal 2015; 22:995-1019. [PMID: 25557408 DOI: 10.1089/ars.2014.6223] [Citation(s) in RCA: 229] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SIGNIFICANCE In all cells, the endoplasmic reticulum (ER) and mitochondria are physically connected to form junctions termed mitochondria-associated membranes (MAMs). This subcellular compartment is under intense investigation because it represents a "hot spot" for the intracellular signaling of important pathways, including the synthesis of cholesterol and phospholipids, calcium homeostasis, and reactive oxygen species (ROS) generation and activity. RECENT ADVANCES The advanced methods currently used to study this fascinating intracellular microdomain in detail have enabled the identification of the molecular composition of MAMs and their involvement within different physiopathological contexts. CRITICAL ISSUES Here, we review the knowledge regarding (i) MAMs composition in terms of protein composition, (ii) the relationship between MAMs and ROS, (iii) the involvement of MAMs in cell death programs with particular emphasis within the tumor context, (iv) the emerging role of MAMs during inflammation, and (v) the key role of MAMs alterations in selected neurological disorders. FUTURE DIRECTIONS Whether alterations in MAMs represent a response to the disease pathogenesis or directly contribute to the disease has not yet been unequivocally established. In any case, the signaling at the MAMs represents a promising pharmacological target for several important human diseases.
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Affiliation(s)
- Carlotta Giorgi
- 1 Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), Department of Morphology, Surgery and Experimental Medicine, University of Ferrara , Ferrara, Italy
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76
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Mitofusin 2 ablation increases endoplasmic reticulum-mitochondria coupling. Proc Natl Acad Sci U S A 2015; 112:E2174-81. [PMID: 25870285 DOI: 10.1073/pnas.1504880112] [Citation(s) in RCA: 416] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The organization and mutual interactions between endoplasmic reticulum (ER) and mitochondria modulate key aspects of cell pathophysiology. Several proteins have been suggested to be involved in keeping ER and mitochondria at a correct distance. Among them, in mammalian cells, mitofusin 2 (Mfn2), located on both the outer mitochondrial membrane and the ER surface, has been proposed to be a physical tether between the two organelles, forming homotypic interactions and heterocomplexes with its homolog Mfn1. Recently, this widely accepted model has been challenged using quantitative EM analysis. Using a multiplicity of morphological, biochemical, functional, and genetic approaches, we demonstrate that Mfn2 ablation increases the structural and functional ER-mitochondria coupling. In particular, we show that in different cell types Mfn2 ablation or silencing increases the close contacts between the two organelles and strengthens the efficacy of inositol trisphosphate (IP3)-induced Ca(2+) transfer from the ER to mitochondria, sensitizing cells to a mitochondrial Ca(2+) overload-dependent death. We also show that the previously reported discrepancy between electron and fluorescence microscopy data on ER-mitochondria proximity in Mfn2-ablated cells is only apparent. By using a different type of morphological analysis of fluorescent images that takes into account (and corrects for) the gross modifications in mitochondrial shape resulting from Mfn2 ablation, we demonstrate that an increased proximity between the organelles is also observed by confocal microscopy when Mfn2 levels are reduced. Based on these results, we propose a new model for ER-mitochondria juxtaposition in which Mfn2 works as a tethering antagonist preventing an excessive, potentially toxic, proximity between the two organelles.
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77
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Mechanisms by which different functional states of mitochondria define yeast longevity. Int J Mol Sci 2015; 16:5528-54. [PMID: 25768339 PMCID: PMC4394491 DOI: 10.3390/ijms16035528] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/05/2015] [Accepted: 03/05/2015] [Indexed: 12/17/2022] Open
Abstract
Mitochondrial functionality is vital to organismal physiology. A body of evidence supports the notion that an age-related progressive decline in mitochondrial function is a hallmark of cellular and organismal aging in evolutionarily distant eukaryotes. Studies of the baker’s yeast Saccharomyces cerevisiae, a unicellular eukaryote, have led to discoveries of genes, signaling pathways and chemical compounds that modulate longevity-defining cellular processes in eukaryotic organisms across phyla. These studies have provided deep insights into mechanistic links that exist between different traits of mitochondrial functionality and cellular aging. The molecular mechanisms underlying the essential role of mitochondria as signaling organelles in yeast aging have begun to emerge. In this review, we discuss recent progress in understanding mechanisms by which different functional states of mitochondria define yeast longevity, outline the most important unanswered questions and suggest directions for future research.
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78
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Mattiazzi Ušaj M, Brložnik M, Kaferle P, Žitnik M, Wolinski H, Leitner F, Kohlwein SD, Zupan B, Petrovič U. Genome-Wide Localization Study of Yeast Pex11 Identifies Peroxisome-Mitochondria Interactions through the ERMES Complex. J Mol Biol 2015; 427:2072-87. [PMID: 25769804 PMCID: PMC4429955 DOI: 10.1016/j.jmb.2015.03.004] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/01/2015] [Accepted: 03/04/2015] [Indexed: 11/29/2022]
Abstract
Pex11 is a peroxin that regulates the number of peroxisomes in eukaryotic cells. Recently, it was found that a mutation in one of the three mammalian paralogs, PEX11β, results in a neurological disorder. The molecular function of Pex11, however, is not known. Saccharomyces cerevisiae Pex11 has been shown to recruit to peroxisomes the mitochondrial fission machinery, thus enabling proliferation of peroxisomes. This process is essential for efficient fatty acid β-oxidation. In this study, we used high-content microscopy on a genome-wide scale to determine the subcellular localization pattern of yeast Pex11 in all non-essential gene deletion mutants, as well as in temperature-sensitive essential gene mutants. Pex11 localization and morphology of peroxisomes was profoundly affected by mutations in 104 different genes that were functionally classified. A group of genes encompassing MDM10, MDM12 and MDM34 that encode the mitochondrial and cytosolic components of the ERMES complex was analyzed in greater detail. Deletion of these genes caused a specifically altered Pex11 localization pattern, whereas deletion of MMM1, the gene encoding the fourth, endoplasmic-reticulum-associated component of the complex, did not result in an altered Pex11 localization or peroxisome morphology phenotype. Moreover, we found that Pex11 and Mdm34 physically interact and that Pex11 plays a role in establishing the contact sites between peroxisomes and mitochondria through the ERMES complex. Based on these results, we propose that the mitochondrial/cytosolic components of the ERMES complex establish a direct interaction between mitochondria and peroxisomes through Pex11. Molecular function of Pex11, a protein with roles in metabolism and disease, is unknown. Genome-wide screening determined subcellular localization of Pex11-GFP in yeast. Mutants defective in components of the ERMES complex show altered Pex11 localization. Pex11 physically interacts with the ERMES complex component Mdm34. ERMES complex and Pex11 mediate interaction between mitochondria and peroxisomes.
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Affiliation(s)
- M Mattiazzi Ušaj
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - M Brložnik
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - P Kaferle
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - M Žitnik
- Faculty of Computer and Information Science, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - H Wolinski
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - F Leitner
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - S D Kohlwein
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - B Zupan
- Faculty of Computer and Information Science, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - U Petrovič
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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79
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Trans-mitochondrial coordination of cristae at regulated membrane junctions. Nat Commun 2015; 6:6259. [PMID: 25687472 PMCID: PMC4332397 DOI: 10.1038/ncomms7259] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/09/2015] [Indexed: 01/22/2023] Open
Abstract
Reminiscent of bacterial quorum sensing, mammalian mitochondria participate in inter-organelle communication. However, physical structures that enhance or enable interactions between mitochondria have not been defined. Here we report that adjacent mitochondria exhibit coordination of inner mitochondrial membrane cristae at inter-mitochondrial junctions (IMJs). These electron-dense structures are conserved across species, resistant to genetic disruption of cristae organization, dynamically modulated by mitochondrial bioenergetics, independent of known inter-mitochondrial tethering proteins mitofusins and rapidly induced by the stable rapprochement of organelles via inducible synthetic linker technology. At the associated junctions, the cristae of adjacent mitochondria form parallel arrays perpendicular to the IMJ, consistent with a role in electrochemical coupling. These IMJs and associated cristae arrays may provide the structural basis to enhance the propagation of intracellular bioenergetic and apoptotic waves through mitochondrial networks within cells. Mammalian mitochondria are capable of inter-organelle communication, but connections between mitochondria have not been defined. Here, Picard et al. report the presence of inter-mitochondrial junctions, electron-dense regions with coordinated inner membrane cristae that do not depend on mitofusins for their formation.
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80
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Verner Z, Basu S, Benz C, Dixit S, Dobáková E, Faktorová D, Hashimi H, Horáková E, Huang Z, Paris Z, Peña-Diaz P, Ridlon L, Týč J, Wildridge D, Zíková A, Lukeš J. Malleable mitochondrion of Trypanosoma brucei. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:73-151. [PMID: 25708462 DOI: 10.1016/bs.ircmb.2014.11.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The importance of mitochondria for a typical aerobic eukaryotic cell is undeniable, as the list of necessary mitochondrial processes is steadily growing. Here, we summarize the current knowledge of mitochondrial biology of an early-branching parasitic protist, Trypanosoma brucei, a causative agent of serious human and cattle diseases. We present a comprehensive survey of its mitochondrial pathways including kinetoplast DNA replication and maintenance, gene expression, protein and metabolite import, major metabolic pathways, Fe-S cluster synthesis, ion homeostasis, organellar dynamics, and other processes. As we describe in this chapter, the single mitochondrion of T. brucei is everything but simple and as such rivals mitochondria of multicellular organisms.
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Affiliation(s)
- Zdeněk Verner
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Present address: Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia; Present address: Faculty of Sciences, Charles University, Prague, Czech Republic
| | - Somsuvro Basu
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Present address: Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Germany
| | - Corinna Benz
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Sameer Dixit
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Dobáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Present address: Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Hassan Hashimi
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Horáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Zhenqiu Huang
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Zdeněk Paris
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Priscila Peña-Diaz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Lucie Ridlon
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Present address: Salk Institute, La Jolla, San Diego, USA
| | - Jiří Týč
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - David Wildridge
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Alena Zíková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
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81
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Rutter J, Hughes AL. Power(2): the power of yeast genetics applied to the powerhouse of the cell. Trends Endocrinol Metab 2015; 26:59-68. [PMID: 25591985 PMCID: PMC4315768 DOI: 10.1016/j.tem.2014.12.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 12/09/2014] [Accepted: 12/09/2014] [Indexed: 11/18/2022]
Abstract
The budding yeast Saccharomyces cerevisiae has served as a remarkable model organism for numerous seminal discoveries in biology. This paradigm extends to the mitochondria, a central hub for cellular metabolism, where studies in yeast have helped to reinvigorate the field and launch an exciting new era in mitochondrial biology. Here we discuss a few recent examples in which yeast research has laid a foundation for our understanding of evolutionarily conserved mitochondrial processes and functions, from key factors and pathways involved in the assembly of oxidative phosphorylation (OXPHOS) complexes to metabolite transport, lipid metabolism, and interorganelle communication. We also highlight new areas of yeast mitochondrial biology that are likely to aid in our understanding of the mitochondrial etiology of disease in the future.
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Affiliation(s)
- Jared Rutter
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
| | - Adam L Hughes
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
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82
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Knoblach B, Rachubinski RA. Sharing the cell's bounty - organelle inheritance in yeast. J Cell Sci 2015; 128:621-30. [PMID: 25616900 DOI: 10.1242/jcs.151423] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Eukaryotic cells replicate and partition their organelles between the mother cell and the daughter cell at cytokinesis. Polarized cells, notably the budding yeast Saccharomyces cerevisiae, are well suited for the study of organelle inheritance, as they facilitate an experimental dissection of organelle transport and retention processes. Much progress has been made in defining the molecular players involved in organelle partitioning in yeast. Each organelle uses a distinct set of factors - motor, anchor and adaptor proteins - that ensures its inheritance by future generations of cells. We propose that all organelles, regardless of origin or copy number, are partitioned by the same fundamental mechanism involving division and segregation. Thus, the mother cell keeps, and the daughter cell receives, their fair and equitable share of organelles. This mechanism of partitioning moreover facilitates the segregation of organelle fragments that are not functionally equivalent. In this Commentary, we describe how this principle of organelle population control affects peroxisomes and other organelles, and outline its implications for yeast life span and rejuvenation.
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Affiliation(s)
- Barbara Knoblach
- Department of Cell Biology, University of Alberta, Edmonton, AL T6G 2H7, Canada
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83
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Membrane trafficking in the yeast Saccharomyces cerevisiae model. Int J Mol Sci 2015; 16:1509-25. [PMID: 25584613 PMCID: PMC4307317 DOI: 10.3390/ijms16011509] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 12/19/2014] [Indexed: 11/29/2022] Open
Abstract
The yeast Saccharomyces cerevisiae is one of the best characterized eukaryotic models. The secretory pathway was the first trafficking pathway clearly understood mainly thanks to the work done in the laboratory of Randy Schekman in the 1980s. They have isolated yeast sec mutants unable to secrete an extracellular enzyme and these SEC genes were identified as encoding key effectors of the secretory machinery. For this work, the 2013 Nobel Prize in Physiology and Medicine has been awarded to Randy Schekman; the prize is shared with James Rothman and Thomas Südhof. Here, we present the different trafficking pathways of yeast S. cerevisiae. At the Golgi apparatus newly synthesized proteins are sorted between those transported to the plasma membrane (PM), or the external medium, via the exocytosis or secretory pathway (SEC), and those targeted to the vacuole either through endosomes (vacuolar protein sorting or VPS pathway) or directly (alkaline phosphatase or ALP pathway). Plasma membrane proteins can be internalized by endocytosis (END) and transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi (recycling or RCY pathway). Studies in yeast S. cerevisiae allowed the identification of most of the known effectors, protein complexes, and trafficking pathways in eukaryotic cells, and most of them are conserved among eukaryotes.
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84
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Affiliation(s)
- Christian Schulz
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
- Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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85
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Tang BL. Synthetic mitochondria as therapeutics against systemic aging: a hypothesis. Cell Biol Int 2014; 39:131-5. [DOI: 10.1002/cbin.10362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Accepted: 07/26/2014] [Indexed: 12/31/2022]
Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry; Yong Loo Lin School of Medicine; National University Health System; Singapore
- NUS Graduate School for Integrative Sciences and Engineering; National University of Singapore; Medical Drive 117597 Singapore
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86
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Ackema KB, Hench J, Böckler S, Wang SC, Sauder U, Mergentaler H, Westermann B, Bard F, Frank S, Spang A. The small GTPase Arf1 modulates mitochondrial morphology and function. EMBO J 2014; 33:2659-75. [PMID: 25190516 DOI: 10.15252/embj.201489039] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The small GTPase Arf1 plays critical roles in membrane traffic by initiating the recruitment of coat proteins and by modulating the activity of lipid-modifying enzymes. Here, we report an unexpected but evolutionarily conserved role for Arf1 and the ArfGEF GBF1 at mitochondria. Loss of function of ARF-1 or GBF-1 impaired mitochondrial morphology and activity in Caenorhabditis elegans. Similarly, mitochondrial defects were observed in mammalian and yeast cells. In Saccharomyces cerevisiae, aberrant clusters of the mitofusin Fzo1 accumulated in arf1-11 mutants and were resolved by overexpression of Cdc48, an AAA-ATPase involved in ER and mitochondria-associated degradation processes. Yeast Arf1 co-fractionated with ER and mitochondrial membranes and interacted genetically with the contact site component Gem1. Furthermore, similar mitochondrial abnormalities resulted from knockdown of either GBF-1 or contact site components in worms, suggesting that the role of Arf1 in mitochondrial functioning is linked to ER-mitochondrial contacts. Thus, Arf1 is involved in mitochondrial homeostasis and dynamics, independent of its role in vesicular traffic.
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Affiliation(s)
- Karin B Ackema
- Growth and Development, Biozentrum University of Basel, Basel, Switzerland
| | - Jürgen Hench
- Division of Neuropathology, Institute of Pathology, University Hospital Basel, Basel, Switzerland
| | | | - Shyi Chyi Wang
- Institute for Molecular and Cell Biology, Singapore City, Singapore
| | - Ursula Sauder
- Microscopy Center, Biozentrum University of Basel, Basel, Switzerland
| | - Heidi Mergentaler
- Growth and Development, Biozentrum University of Basel, Basel, Switzerland
| | | | - Frédéric Bard
- Institute for Molecular and Cell Biology, Singapore City, Singapore
| | - Stephan Frank
- Division of Neuropathology, Institute of Pathology, University Hospital Basel, Basel, Switzerland
| | - Anne Spang
- Growth and Development, Biozentrum University of Basel, Basel, Switzerland
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