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Kornelius Zeth, Ulrich Zachariae
Mitochondria are evolutionarily related to Gram-negative bacteria and both comprise two membrane systems with strongly differing protein composition. The major protein in the outer membrane of mitochondria is the voltage-dependent anion channel (VDAC), which mediates signal transmission across the outer membrane but also the exchange of metabolites, most importantly ADP and ATP. More than 30 years after its discovery three identical high-resolution structures were determined in 2008. These structures show a 19-stranded anti-parallel beta-barrel with an N-terminal helix located inside...
2018: Frontiers in Physiology
Guoxiang Jin, Chuan Xu, Xian Zhang, Jie Long, Abdol Hossein Rezaeian, Chunfang Liu, Mark E Furth, Steven Kridel, Boris Pasche, Xiu-Wu Bian, Hui-Kuan Lin
Although deletion of certain autophagy-related genes has been associated with defects in hematopoiesis, it remains unclear whether hyperactivated mitophagy affects the maintenance and differentiation of hematopoietic stem cells (HSCs) and committed progenitor cells. Here we report that targeted deletion of the gene encoding the AAA+-ATPase Atad3a hyperactivated mitophagy in mouse hematopoietic cells. Affected mice showed reduced survival, severely decreased bone-marrow cellularity, erythroid anemia and B cell lymphopenia...
January 2018: Nature Immunology
Ayano Mise, Yuta Yoshino, Kiyohiro Yamazaki, Yuki Ozaki, Tomoko Sao, Taku Yoshida, Takaaki Mori, Yoko Mori, Shinichiro Ochi, Jun-Ichi Iga, Shu-Ichi Ueno
BACKGROUND: TOMM40 is located on chromosome 19, is in linkage disequilibrium with apolipoprotein E (APOE), andis reported in several genome-wide association studies to be associated with Alzheimer's disease (AD). OBJECTIVE: Assess APOE and TOM40 and mitochondrial genes as blood biomarkers for AD. METHODS: We examined TOMM40, PTEN-induced putative kinase 1 (PINK1), Parkin RBR E3 ubiquitin protein ligase (PARK2), and APOE mRNA expression in relation to the methylation rates of CpG sites in the upstream region of TOMM40exon 1 in peripheral leukocytes and TOMM40523 polyT genotypes in 60 AD and age- and sex-matched control subjects...
2017: Journal of Alzheimer's Disease: JAD
Vivien Krüger, Thomas Becker, Lars Becker, Malayko Montilla-Martinez, Lars Ellenrieder, F-Nora Vögtle, Helmut E Meyer, Michael T Ryan, Nils Wiedemann, Bettina Warscheid, Nikolaus Pfanner, Richard Wagner, Chris Meisinger
The mitochondrial outer membrane is essential for communication between mitochondria and the rest of the cell and facilitates the transport of metabolites, ions, and proteins. All mitochondrial outer membrane channels known to date are β-barrel membrane proteins, including the abundant voltage-dependent anion channel and the cation-preferring protein-conducting channels Tom40, Sam50, and Mdm10. We analyzed outer membrane fractions of yeast mitochondria and identified four new channel activities: two anion-preferring channels and two cation-preferring channels...
November 6, 2017: Journal of Cell Biology
Thomas Bausewein, Deryck J Mills, Julian D Langer, Beate Nitschke, Stephan Nussberger, Werner Kühlbrandt
The TOM complex is the main entry gate for protein precursors from the cytosol into mitochondria. We have determined the structure of the TOM core complex by cryoelectron microscopy (cryo-EM). The complex is a 148 kDa symmetrical dimer of ten membrane protein subunits that create a shallow funnel on the cytoplasmic membrane surface. In the core of the dimer, the β-barrels of the Tom40 pore form two identical preprotein conduits. Each Tom40 pore is surrounded by the transmembrane segments of the α-helical subunits Tom5, Tom6, and Tom7...
August 10, 2017: Cell
Kahli Zeitlow, Lefko Charlambous, Isaac Ng, Sonal Gagrani, Mirta Mihovilovic, Shuhong Luo, Daniel L Rock, Ann Saunders, Allen D Roses, W Kirby Gottschalk
A variable-length poly-T variant in intron 6 of the TOMM40 gene, rs10524523, is associated with risk and age-of-onset of sporadic (late-onset) Alzheimer's disease. In Caucasians, the three predominant alleles at this locus are Short (S), Long (L) or Very long (VL). On an APOE ε3/3 background, the S/VL and VL/VL genotypes are more protective than S/S. The '523 poly-T has regulatory properties, in that the VL poly-T results in higher expression than the S poly-T in luciferase expression systems. The aim of the current work was to identify effects on cellular bioenergetics of increased TOM40 protein expression...
November 2017: Biochimica et Biophysica Acta
Byung Geun Ha, Sung Suk Jung, Yun Hee Shon
Proton beam therapy has recently been used to improve local control of tumor growth and reduce side-effects by decreasing the global dose to normal tissue. However, the regulatory mechanisms underlying the physiological role of proton beam radiation are not well understood, and many studies are still being conducted regarding these mechanisms. To determine the effects of proton beams on mitochondrial biogenesis, we investigated: mitochondrial DNA (mtDNA) mass; the gene expression of mitochondrial transcription factors, functional regulators, and dynamic-related regulators; and the phosphorylation of the signaling molecules that participate in mitochondrial biogenesis...
July 5, 2017: International Journal of Oncology
Maya Ando, Fabienne C Fiesel, Roman Hudec, Thomas R Caulfield, Kotaro Ogaki, Paulina Górka-Skoczylas, Dariusz Koziorowski, Andrzej Friedman, Li Chen, Valina L Dawson, Ted M Dawson, Guojun Bu, Owen A Ross, Zbigniew K Wszolek, Wolfdieter Springer
BACKGROUND: Mutations in PINK1 and PARKIN are the most common causes of recessive early-onset Parkinson's disease (EOPD). Together, the mitochondrial ubiquitin (Ub) kinase PINK1 and the cytosolic E3 Ub ligase PARKIN direct a complex regulated, sequential mitochondrial quality control. Thereby, damaged mitochondria are identified and targeted to degradation in order to prevent their accumulation and eventually cell death. Homozygous or compound heterozygous loss of either gene function disrupts this protective pathway, though at different steps and by distinct mechanisms...
April 24, 2017: Molecular Neurodegeneration
Julia Bruggisser, Sandro Käser, Jan Mani, André Schneider
The mitochondrial outer membrane (OM) contains single and multiple membrane-spanning proteins that need to contain signals that ensure correct targeting and insertion into the OM. The biogenesis of such proteins has so far essentially only been studied in yeast and related organisms. Here we show that POMP10, an OM protein of the early diverging protozoan Trypanosoma brucei , is signal-anchored. Transgenic cells expressing variants of POMP10 fused to GFP demonstrate that the N-terminal membrane-spanning domain flanked by a few positively charged or neutral residues is both necessary and sufficient for mitochondrial targeting...
February 24, 2017: Journal of Biological Chemistry
Jan Mani, Samuel Rout, Silvia Desy, André Schneider
The β-barrel protein Tom40 and the α-helically anchored membrane protein Tom22 are the only universally conserved subunits of the protein translocase of the mitochondrial outer membrane (TOM). Tom22 has an N-terminal cytosolic and a C-terminal intermembrane space domain. It occurs in two variants: one typified by the yeast protein which has a cytosolic domain containing a cluster of acidic residues, and a shorter variant typified by the plant protein that lacks this domain. Yeast-type Tom22 functions as a secondary protein import receptor and is also required for the stability of the TOM complex...
January 17, 2017: Scientific Reports
Nargis Parvin, Chris Carrie, Isabelle Pabst, Antonia Läßer, Debabrata Laha, Melanie V Paul, Peter Geigenberger, Ralf Heermann, Kirsten Jung, Ute C Vothknecht, Fatima Chigri
The translocon on the outer membrane of mitochondria (TOM) facilitates the import of nuclear-encoded proteins. The principal machinery of mitochondrial protein transport seems conserved in eukaryotes; however, divergence in the composition and structure of TOM components has been observed between mammals, yeast, and plants. TOM9, the plant homolog of yeast Tom22, is significantly smaller due to a truncation in the cytosolic receptor domain, and its precise function is not understood. Here we provide evidence showing that TOM9...
April 3, 2017: Molecular Plant
Samuel Rout, Jon Paulin Zumthor, Elisabeth M Schraner, Carmen Faso, Adrian B Hehl
Protozoan parasites of the genus Giardia are highly prevalent globally, and infect a wide range of vertebrate hosts including humans, with proliferation and pathology restricted to the small intestine. This narrow ecological specialization entailed extensive structural and functional adaptations during host-parasite co-evolution. An example is the streamlined mitosomal proteome with iron-sulphur protein maturation as the only biochemical pathway clearly associated with this organelle. Here, we applied techniques in microscopy and protein biochemistry to investigate the mitosomal membrane proteome in association to mitosome homeostasis...
December 2016: PLoS Pathogens
Lu Li, Szymon Kubiszewski-Jakubiak, Jordan Radomiljac, Yan Wang, Simon R Law, Olivier Keech, Reena Narsai, Oliver Berkowitz, Owen Duncan, Monika W Murcha, James Whelan
In plant cells, mitochondria are major providers of energy and building blocks for growth and development as well as abiotic and biotic stress responses. They are encircled by two lipid membranes containing proteins that control mitochondrial function through the import of macromolecules and metabolites. Characterization of a novel β-barrel protein, OUTER MEMBRANE PROTEIN 47 (OM47), unique to the green lineage and related to the voltage-dependent anion channel (VDAC) protein family, showed that OM47 can complement a VDAC mutant in yeast...
November 2016: Journal of Experimental Botany
Pasquale Picone, Silvia Vilasi, Fabio Librizzi, Marco Contardi, Domenico Nuzzo, Luca Caruana, Sara Baldassano, Antonella Amato, Flavia Mulè, Pier Luigi San Biagio, Daniela Giacomazza, Marta Di Carlo
The onset of Alzheimer disease (AD) is influenced by several risk factors comprising diabetes. Within this context, antidiabetic drugs, including metformin, are investigated for their effect on AD. We report that in the C57B6/J mice, metformin is delivered to the brain where activates AMP-activated kinase (AMPK), its molecular target. This drug affects the levels of β-secretase (BACE1) and β-amyloid precursor protein (APP), promoting processing and aggregation of β-amyloid (Aβ), mainly in the cortex region...
August 2016: Aging
John O Ogunbileje, Craig Porter, David N Herndon, Tony Chao, Doaa R Abdelrahman, Anastasia Papadimitriou, Maria Chondronikola, Teresa A Zimmers, Paul T Reidy, Blake B Rasmussen, Labros S Sidossis
Burn trauma results in prolonged hypermetabolism and skeletal muscle wasting. How hypermetabolism contributes to muscle wasting in burn patients remains unknown. We hypothesized that oxidative stress, cytosolic protein degradation, and mitochondrial stress as a result of hypermetabolism contribute to muscle cachexia postburn. Patients (n = 14) with burns covering >30% of their total body surface area were studied. Controls (n = 13) were young healthy adults. We found that burn patients were profoundly hypermetabolic at both the skeletal muscle and systemic levels, indicating increased oxygen consumption by mitochondria...
August 1, 2016: American Journal of Physiology. Endocrinology and Metabolism
Andrea Magrì, Maria Carmela Di Rosa, Marianna Flora Tomasello, Francesca Guarino, Simona Reina, Angela Messina, Vito De Pinto
Cu/Zn Superoxide Dismutase (SOD1), the most important antioxidant defense against ROS in eukaryotic cells, localizes in cytosol and intermembrane space of mitochondria (IMS). Several evidences show a SOD1 intersection with both fermentative and respiratory metabolism. The Voltage Dependent Anion Channel (VDAC) is the main pore-forming protein in the mitochondrial outer membrane (MOM), and is considered the gatekeeper of mitochondrial metabolism. Saccharomyces cerevisiae lacking VDAC1 (Δpor1) is a very convenient model system, since it shows an impaired growth rate on non-fermentable carbon source...
June 2016: Biochimica et Biophysica Acta
Morgane Michaud, Valérie Gros, Marianne Tardif, Sabine Brugière, Myriam Ferro, William A Prinz, Alexandre Toulmay, Jaideep Mathur, Michael Wozny, Denis Falconet, Eric Maréchal, Maryse A Block, Juliette Jouhet
The mitochondrion is an organelle originating from an endosymbiotic event and playing a role in several fundamental processes such as energy production, metabolite syntheses, and programmed cell death. This organelle is delineated by two membranes whose synthesis requires an extensive exchange of phospholipids with other cellular organelles such as endoplasmic reticulum (ER) and vacuolar membranes in yeast. These transfers of phospholipids are thought to occur by a non-vesicular pathway at contact sites between two closely apposed membranes...
March 7, 2016: Current Biology: CB
Jan Mani, Chris Meisinger, André Schneider
Mitochondria are essential for eukaryotic life and more than 95% of their proteins are imported as precursors from the cytosol. The targeting signals for this posttranslational import are conserved in all eukaryotes. However, this conservation does not hold true for the protein translocase of the mitochondrial outer membrane that serves as entry gate for essentially all precursor proteins. Only two of its subunits, Tom40 and Tom22, are conserved and thus likely were present in the last eukaryotic common ancestor...
February 2016: Molecular Biology and Evolution
Sriram Garg, Jan Stölting, Verena Zimorski, Petr Rada, Jan Tachezy, William F Martin, Sven B Gould
The origin of protein import was a key step in the endosymbiotic acquisition of mitochondria. Though the main translocon of the mitochondrial outer membrane, TOM40, is ubiquitous among organelles of mitochondrial ancestry, the transit peptides, or N-terminal targeting sequences (NTSs), recognised by the TOM complex, are not. To better understand the nature of evolutionary conservation in mitochondrial protein import, we investigated the targeting behavior of Trichomonas vaginalis hydrogenosomal proteins in Saccharomyces cerevisiae and vice versa...
September 2015: Genome Biology and Evolution
Adam J Kuszak, Daniel Jacobs, Philip A Gurnev, Takuya Shiota, John M Louis, Trevor Lithgow, Sergey M Bezrukov, Tatiana K Rostovtseva, Susan K Buchanan
Nearly all mitochondrial proteins are coded by the nuclear genome and must be transported into mitochondria by the translocase of the outer membrane complex. Tom40 is the central subunit of the translocase complex and forms a pore in the mitochondrial outer membrane. To date, the mechanism it utilizes for protein transport remains unclear. Tom40 is predicted to comprise a membrane-spanning β-barrel domain with conserved α-helical domains at both the N and C termini. To investigate Tom40 function, including the role of the N- and C-terminal domains, recombinant forms of the Tom40 protein from the yeast Candida glabrata, and truncated constructs lacking the N- and/or C-terminal domains, were functionally characterized in planar lipid membranes...
October 23, 2015: Journal of Biological Chemistry
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