51
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Gewaid H, Mesalam AA, Ibrahim AA, Abdel Shafy DN, Abdel Shafy RN, Emara N, Hamdy SM, Gewaid M, Bahgat MM. Establishment of a platform for molecular and immunological characterization of the RNA-dependent-RNA-polymerase NS5B of an Egyptian HCV isolate. J Med Virol 2017; 90:545-558. [PMID: 29064582 DOI: 10.1002/jmv.24977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Accepted: 10/16/2017] [Indexed: 11/09/2022]
Abstract
The present work aimed at establishing a platform to enable frequent characterization of the HCV RNA-dependent-RNA-polymerase from Egyptian clinical isolates. Subjecting amplified HCV-NS5B coding gene from Egyptian patient's serum to sequencing, multiple alignment, and phylogenetic analysis confirmed its subtype 4a origin. Nucleotide sequence analysis revealed presence of an additional start codon at the beginning of the NS5B gene. Peptide sequence alignment demonstrated presence of unique amino acid residues in our 4a-NS5B sequence distinct from the JFH-1-NS5B sequence as well as unique amino acids compared to other genotypes. The distinct molecular structure of the herein characterized 4a-NS5B from the 2a-JFH-1-NS5B was further demonstrated both in the built 3D models and the Ramachandran plots corresponding to each structure. Both the unique amino acid residues and 3D structure of the 4a-NS5B may influence both genotype 4a replication rate and response to therapy in comparison to other genotypes. Many resistance mutations to polymerase inhibitors were found both in ours and other genotypes' sequences. The presence of the required amino acid motifs for the RNA dependent RNA polymerase activity encouraged to clone the NS5B570-encoding sequence downstream CMV promotor in a mammalian expression vector. Such construct was used for both prokaryotic expression in bacteria and for DNA immunization. Successful mammalian expression and induction of specific immune response were demonstrated by ELISA and Western blotting. The potential of both the raised antibodies and the expressed NS5B to differentiate between HCV-infected and control human sera were demonstrated which reflect their diagnostic value.
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Affiliation(s)
- Hossam Gewaid
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Therapeutic Chemistry Department, the National Research Center, Cairo, Egypt
| | - Ahmed A Mesalam
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Therapeutic Chemistry Department, the National Research Center, Cairo, Egypt
| | - Ahmed A Ibrahim
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Therapeutic Chemistry Department, the National Research Center, Cairo, Egypt
| | - Dina N Abdel Shafy
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Water Pollution Research Department, the National Research Center, Cairo, Egypt
| | - Rola N Abdel Shafy
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Therapeutic Chemistry Department, the National Research Center, Cairo, Egypt
| | - Nahed Emara
- Clinical and Chemical Pathology Department, the National Research Center, Cairo, Egypt
| | - Soha M Hamdy
- Division of Biochemistry, Faculty of Science, Fayoum University, Cairo, Egypt
| | | | - Mahmoud M Bahgat
- Research Group Immune- and Bio-markers for Infection, the Center of Excellence for Advanced Sciences, the National Research Center, Cairo, Egypt.,Therapeutic Chemistry Department, the National Research Center, Cairo, Egypt
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52
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Voth W, Jakob U. Stress-Activated Chaperones: A First Line of Defense. Trends Biochem Sci 2017; 42:899-913. [PMID: 28893460 DOI: 10.1016/j.tibs.2017.08.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/18/2017] [Accepted: 08/21/2017] [Indexed: 10/18/2022]
Abstract
Proteins are constantly challenged by environmental stress conditions that threaten their structure and function. Especially problematic are oxidative, acid, and severe heat stress which induce very rapid and widespread protein unfolding and generate conditions that make canonical chaperones and/or transcriptional responses inadequate to protect the proteome. We review here recent advances in identifying and characterizing stress-activated chaperones which are inactive under non-stress conditions but become potent chaperones under specific protein-unfolding stress conditions. We discuss the post-translational mechanisms by which these chaperones sense stress, and consider the role that intrinsic disorder plays in their regulation and function. We examine their physiological roles under both non-stress and stress conditions, their integration into the cellular proteostasis network, and their potential as novel therapeutic targets.
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Affiliation(s)
- Wilhelm Voth
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular Biology, Universitätsmedizin Göttingen, 37073 Göttingen, Germany
| | - Ursula Jakob
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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53
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Shing JC, Lindquist LD, Borgese N, Bram RJ. CAML mediates survival of Myc-induced lymphoma cells independent of tail-anchored protein insertion. Cell Death Discov 2017; 3:16098. [PMID: 28580168 PMCID: PMC5447128 DOI: 10.1038/cddiscovery.2016.98] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 11/06/2016] [Accepted: 11/23/2016] [Indexed: 12/17/2022] Open
Abstract
Calcium-modulating cyclophilin ligand (CAML) is an endoplasmic reticulum (ER) protein that functions, along with WRB and TRC40, to mediate tail-anchored (TA) protein insertion into the ER membrane. Physiologic roles for CAML include endocytic trafficking, intracellular calcium signaling, and the survival and proliferation of specialized immune cells, recently attributed to its requirement for TA protein insertion. To identify a possible role for CAML in cancer cells, we generated Eμ-Myc transgenic mice that carry a tamoxifen-inducible deletion allele of Caml. In multiple B-cell lymphoma cell lines derived from these mice, homozygous loss of Caml activated apoptosis. Cell death was blocked by Bcl-2/Bcl-xL overexpression; however, rescue from apoptosis was insufficient to restore proliferation. Tumors established from an Eμ-Myc lymphoma cell line completely regressed after tamoxifen administration, suggesting that CAML is also required for these cancer cells to survive and grow in vivo. Cell cycle analyses of Caml-deleted lymphoma cells revealed an arrest in G2/M, accompanied by low expression of the mitotic marker, phospho-histone H3 (Ser10). Surprisingly, lymphoma cell viability did not depend on the domain of CAML required for its interaction with TRC40. Furthermore, a small protein fragment consisting of the C-terminal 111 amino acid residues of CAML, encompassing the WRB-binding domain, was sufficient to rescue growth and survival of Caml-deleted lymphoma cells. Critically, this minimal region of CAML did not restore TA protein insertion in knockout cells. Taken together, these data reveal an essential role for CAML in supporting survival and mitotic progression in Myc-driven lymphomas that is independent of its TA protein insertion function.
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Affiliation(s)
- Jennifer C Shing
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Lonn D Lindquist
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Nica Borgese
- Consiglio Nazionale delle Ricerche Institute of Neuroscience, Milan, Italy
| | - Richard J Bram
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.,Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN, USA
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54
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Costello JL, Castro IG, Camões F, Schrader TA, McNeall D, Yang J, Giannopoulou EA, Gomes S, Pogenberg V, Bonekamp NA, Ribeiro D, Wilmanns M, Jedd G, Islinger M, Schrader M. Predicting the targeting of tail-anchored proteins to subcellular compartments in mammalian cells. J Cell Sci 2017; 130:1675-1687. [PMID: 28325759 PMCID: PMC5450235 DOI: 10.1242/jcs.200204] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/14/2017] [Indexed: 12/22/2022] Open
Abstract
Tail-anchored (TA) proteins contain a single transmembrane domain (TMD) at the C-terminus that anchors them to the membranes of organelles where they mediate critical cellular processes. Accordingly, mutations in genes encoding TA proteins have been identified in a number of severe inherited disorders. Despite the importance of correctly targeting a TA protein to its appropriate membrane, the mechanisms and signals involved are not fully understood. In this study, we identify additional peroxisomal TA proteins, discover more proteins that are present on multiple organelles, and reveal that a combination of TMD hydrophobicity and tail charge determines targeting to distinct organelle locations in mammals. Specifically, an increase in tail charge can override a hydrophobic TMD signal and re-direct a protein from the ER to peroxisomes or mitochondria and vice versa. We show that subtle changes in those parameters can shift TA proteins between organelles, explaining why peroxisomes and mitochondria have many of the same TA proteins. This enabled us to associate characteristic physicochemical parameters in TA proteins with particular organelle groups. Using this classification allowed successful prediction of the location of uncharacterized TA proteins for the first time.
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Affiliation(s)
| | - Inês G Castro
- Biosciences, University of Exeter, Exeter EX4 4QD, UK
| | - Fátima Camões
- Centre for Cell Biology/Institute of Biomedicine & Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | | | | | - Jing Yang
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore
| | | | - Sílvia Gomes
- Centre for Cell Biology/Institute of Biomedicine & Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | | | - Nina A Bonekamp
- Centre for Cell Biology/Institute of Biomedicine & Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Daniela Ribeiro
- Centre for Cell Biology/Institute of Biomedicine & Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | | | - Gregory Jedd
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore
| | - Markus Islinger
- Institute of Neuroanatomy, Center for Biomedicine and Medical Technology Mannheim, University of Heidelberg, Mannheim 68167, Germany
| | - Michael Schrader
- Biosciences, University of Exeter, Exeter EX4 4QD, UK
- Centre for Cell Biology/Institute of Biomedicine & Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
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55
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Xing S, Mehlhorn DG, Wallmeroth N, Asseck LY, Kar R, Voss A, Denninger P, Schmidt VAF, Schwarzländer M, Stierhof YD, Grossmann G, Grefen C. Loss of GET pathway orthologs in Arabidopsis thaliana causes root hair growth defects and affects SNARE abundance. Proc Natl Acad Sci U S A 2017; 114:E1544-E1553. [PMID: 28096354 PMCID: PMC5338382 DOI: 10.1073/pnas.1619525114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are key players in cellular trafficking and coordinate vital cellular processes, such as cytokinesis, pathogen defense, and ion transport regulation. With few exceptions, SNAREs are tail-anchored (TA) proteins, bearing a C-terminal hydrophobic domain that is essential for their membrane integration. Recently, the Guided Entry of Tail-anchored proteins (GET) pathway was described in mammalian and yeast cells that serve as a blueprint of TA protein insertion [Schuldiner M, et al. (2008) Cell 134(4):634-645; Stefanovic S, Hegde RS (2007) Cell 128(6):1147-1159]. This pathway consists of six proteins, with the cytosolic ATPase GET3 chaperoning the newly synthesized TA protein posttranslationally from the ribosome to the endoplasmic reticulum (ER) membrane. Structural and biochemical insights confirmed the potential of pathway components to facilitate membrane insertion, but the physiological significance in multicellular organisms remains to be resolved. Our phylogenetic analysis of 37 GET3 orthologs from 18 different species revealed the presence of two different GET3 clades. We identified and analyzed GET pathway components in Arabidopsis thaliana and found reduced root hair elongation in Atget lines, possibly as a result of reduced SNARE biogenesis. Overexpression of AtGET3a in a receptor knockout (KO) results in severe growth defects, suggesting presence of alternative insertion pathways while highlighting an intricate involvement for the GET pathway in cellular homeostasis of plants.
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Affiliation(s)
- Shuping Xing
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Dietmar Gerald Mehlhorn
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Niklas Wallmeroth
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Lisa Yasmin Asseck
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Ritwika Kar
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Alessa Voss
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Philipp Denninger
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Vanessa Aphaia Fiona Schmidt
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Markus Schwarzländer
- Institute of Crop Science and Resource Conservation, University of Bonn, 53113 Bonn, Germany
| | - York-Dieter Stierhof
- Centre for Plant Molecular Biology, Microscopy, University of Tübingen, 72076 Tuebingen, Germany
| | - Guido Grossmann
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Christopher Grefen
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany;
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56
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Padgett LR, Arrizabalaga G, Sullivan WJ. Targeting of tail-anchored membrane proteins to subcellular organelles in Toxoplasma gondii. Traffic 2017; 18:149-158. [PMID: 27991712 DOI: 10.1111/tra.12464] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 12/12/2016] [Accepted: 12/12/2016] [Indexed: 12/20/2022]
Abstract
Proper protein localization is essential for critical cellular processes, including vesicle-mediated transport and protein translocation. Tail-anchored (TA) proteins are integrated into organellar membranes via the C-terminus, orienting the N-terminus towards the cytosol. Localization of TA proteins occurs posttranslationally and is governed by the C-terminus, which contains the integral transmembrane domain (TMD) and targeting sequence. Targeting of TA proteins is dependent on the hydrophobicity of the TMD as well as the length and composition of flanking amino acid sequences. We previously identified an unusual homologue of elongator protein, Elp3, in the apicomplexan parasite Toxoplasma gondii as a TA protein targeting the outer mitochondrial membrane. We sought to gain further insight into TA proteins and their targeting mechanisms using this early-branching eukaryote as a model. Our bioinformatics analysis uncovered 59 predicted TA proteins in Toxoplasma, 9 of which were selected for follow-up analyses based on representative features. We identified novel TA proteins that traffic to specific organelles in Toxoplasma, including the parasite endoplasmic reticulum, mitochondrion, and Golgi apparatus. Domain swap experiments elucidated that targeting of TA proteins to these specific organelles was strongly influenced by the TMD sequence, including charge of the flanking C-terminal sequence.
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Affiliation(s)
- Leah R Padgett
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Gustavo Arrizabalaga
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana.,Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana
| | - William J Sullivan
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana.,Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana
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57
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Pietro DSG, Fabrizio B. Transient Secretory Enzyme Expression in Leaf Protoplasts to Characterize SNARE Functional Classes in Conventional and Unconventional Secretion. Methods Mol Biol 2017; 1662:209-221. [PMID: 28861831 DOI: 10.1007/978-1-4939-7262-3_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Despite a long case history, the use of protoplasts in cell biology research still divides scientists but their weaknesses can be exploited as strengths. Transient expression in protoplasts can saturate protein-protein interactions very efficiently, inhibiting the process of interest more efficiently than other approaches at gene expression level. The method described here consists of an assay providing a functional characterization of SNARE proteins in a heterogeneous population of cells, by the comparison of native and dominant negative mutant forms. In particular, it allows for discriminating between t-SNARE and i-SNARE functional classes.
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Affiliation(s)
- Di Sansebastiano Gian Pietro
- DiSTeBA (Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali), University of Salento, Campus ECOTEKNE, Lecce, 73100, Italy.
| | - Barozzi Fabrizio
- DiSTeBA (Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali), University of Salento, Campus ECOTEKNE, Lecce, 73100, Italy
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58
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Chu L, Gruber A, Ast M, Schmitz-Esser S, Altensell J, Neuhaus HE, Kroth PG, Haferkamp I. Shuttling of (deoxy-) purine nucleotides between compartments of the diatom Phaeodactylum tricornutum. THE NEW PHYTOLOGIST 2017; 213:193-205. [PMID: 27504715 DOI: 10.1111/nph.14126] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 06/25/2016] [Indexed: 05/10/2023]
Abstract
Diatom plastids show several peculiarities when compared with primary plastids of higher plants or algae. They are surrounded by four membranes and depend on nucleotide uptake because, unlike in plants, nucleotide de novo synthesis exclusively occurs in the cytosol. Previous analyses suggest that two specifically adapted nucleotide transporters (NTTs) facilitate the required passage of nucleotides across the innermost plastid membrane. However, nucleotide transport across the additional plastid membranes remains to be clarified. Phylogenetic studies, transport assays with the recombinant protein as well as GFP-based targeting analyses allowed detailed characterization of a novel isoform (PtNTT5) of the six NTTs of Phaeodactylum tricornutum. PtNTT5 exhibits low amino acid similarities and is only distantly related to all previously characterized NTTs. However, in a heterologous expression system, it acts as a nucleotide antiporter and prefers various (deoxy-) purine nucleotides as substrates. Interestingly, PtNTT5 is probably located in the endoplasmic reticulum, which in diatoms also represents the outermost plastid membrane. PtNTT5, with its unusual transport properties, phylogeny and localization, can be taken as further evidence for the establishment of a sophisticated and specifically adapted nucleotide transport system in diatom plastids.
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Affiliation(s)
- Lili Chu
- Pflanzliche Ökophysiologie, Fachbereich Biologie, Universität Konstanz, 78457, Konstanz, Germany
| | - Ansgar Gruber
- Pflanzliche Ökophysiologie, Fachbereich Biologie, Universität Konstanz, 78457, Konstanz, Germany
| | - Michelle Ast
- Pflanzenphysiologie, Technische Universität Kaiserslautern, 67653, Kaiserslautern, Germany
| | | | - Jacqueline Altensell
- Pflanzenphysiologie, Technische Universität Kaiserslautern, 67653, Kaiserslautern, Germany
| | - Horst Ekkehard Neuhaus
- Pflanzenphysiologie, Technische Universität Kaiserslautern, 67653, Kaiserslautern, Germany
| | - Peter G Kroth
- Pflanzliche Ökophysiologie, Fachbereich Biologie, Universität Konstanz, 78457, Konstanz, Germany
| | - Ilka Haferkamp
- Pflanzenphysiologie, Technische Universität Kaiserslautern, 67653, Kaiserslautern, Germany
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59
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Rao M, Okreglak V, Chio US, Cho H, Walter P, Shan SO. Multiple selection filters ensure accurate tail-anchored membrane protein targeting. eLife 2016; 5. [PMID: 27925580 PMCID: PMC5214336 DOI: 10.7554/elife.21301] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 12/06/2016] [Indexed: 11/13/2022] Open
Abstract
Accurate protein localization is crucial to generate and maintain organization in all cells. Achieving accuracy is challenging, as the molecular signals that dictate a protein's cellular destination are often promiscuous. A salient example is the targeting of an essential class of tail-anchored (TA) proteins, whose sole defining feature is a transmembrane domain near their C-terminus. Here we show that the Guided Entry of Tail-anchored protein (GET) pathway selects TA proteins destined to the endoplasmic reticulum (ER) utilizing distinct molecular steps, including differential binding by the co-chaperone Sgt2 and kinetic proofreading after ATP hydrolysis by the targeting factor Get3. Further, the different steps select for distinct physicochemical features of the TA substrate. The use of multiple selection filters may be general to protein biogenesis pathways that must distinguish correct and incorrect substrates based on minor differences.
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Affiliation(s)
- Meera Rao
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Voytek Okreglak
- Howard Hughes Medical Institute, University of California, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California, San Francisco, United States
| | - Un Seng Chio
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Peter Walter
- Howard Hughes Medical Institute, University of California, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California, San Francisco, United States
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
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60
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Guan Y, Wang DY, Ying SH, Feng MG. Miro GTPase controls mitochondrial behavior affecting stress tolerance and virulence of a fungal insect pathogen. Fungal Genet Biol 2016; 93:1-9. [DOI: 10.1016/j.fgb.2016.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 05/25/2016] [Accepted: 05/26/2016] [Indexed: 10/21/2022]
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61
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Pagliuso A, Valente C, Giordano LL, Filograna A, Li G, Circolo D, Turacchio G, Marzullo VM, Mandrich L, Zhukovsky MA, Formiggini F, Polishchuk RS, Corda D, Luini A. Golgi membrane fission requires the CtBP1-S/BARS-induced activation of lysophosphatidic acid acyltransferase δ. Nat Commun 2016; 7:12148. [PMID: 27401954 PMCID: PMC4945875 DOI: 10.1038/ncomms12148] [Citation(s) in RCA: 214] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 06/03/2016] [Indexed: 11/25/2022] Open
Abstract
Membrane fission is an essential cellular process by which continuous membranes split into separate parts. We have previously identified CtBP1-S/BARS (BARS) as a key component of a protein complex that is required for fission of several endomembranes, including basolateral post-Golgi transport carriers. Assembly of this complex occurs at the Golgi apparatus, where BARS binds to the phosphoinositide kinase PI4KIIIβ through a 14-3-3γ dimer, as well as to ARF and the PKD and PAK kinases. We now report that, when incorporated into this complex, BARS binds to and activates a trans-Golgi lysophosphatidic acid (LPA) acyltransferase type δ (LPAATδ) that converts LPA into phosphatidic acid (PA); and that this reaction is essential for fission of the carriers. LPA and PA have unique biophysical properties, and their interconversion might facilitate the fission process either directly or indirectly (via recruitment of proteins that bind to PA, including BARS itself).
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Affiliation(s)
- Alessandro Pagliuso
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, Pozzuoli 80078, Italy
| | - Carmen Valente
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Lucia Laura Giordano
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Angela Filograna
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Guiling Li
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Diego Circolo
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Gabriele Turacchio
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Vincenzo Manuel Marzullo
- IRCCS SDN Istituto di Ricerca Diagnostica e Nucleare, Via Emanuele Gianturco 113, 80143 Naples, Italy
| | - Luigi Mandrich
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Mikhail A. Zhukovsky
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Fabio Formiggini
- Italian Institute of Technology, Centre for Advanced Biomaterials for Health Care at CRIB, Largo Barsanti e Matteucci 53, Naples 80125, Italy
| | - Roman S. Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, Pozzuoli 80078, Italy
| | - Daniela Corda
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Alberto Luini
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
- IRCCS SDN Istituto di Ricerca Diagnostica e Nucleare, Via Emanuele Gianturco 113, 80143 Naples, Italy
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62
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Hawthorne JL, Mehta PR, Singh PP, Wong NQ, Quintero OA. Positively charged residues within the MYO19 MyMOMA domain are essential for proper localization of MYO19 to the mitochondrial outer membrane. Cytoskeleton (Hoboken) 2016; 73:286-299. [PMID: 27126804 DOI: 10.1002/cm.21305] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 11/06/2022]
Abstract
Myosins are well characterized molecular motors essential for intracellular transport. MYO19 copurifies with mitochondria, and can be released from mitochondrial membranes by high pH buffer, suggesting that positively-charged residues participate in interactions between MYO19 and mitochondria. The MYO19-specific mitochondria outer membrane association (MyMOMA) domain contains approximately 150 amino acids with a pI approximately 9 and is sufficient for localization to the mitochondrial outer membrane. The minimal sequence and specific residues involved in mitochondrial binding have not been identified. To address this, we generated GFP-MyMOMA truncations, establishing the boundaries for truncations based on sequence homology. We identified an 83-amino acid minimal binding region enriched with basic residues (pI ∼ 10.5). We sequentially replaced basic residues in this region with alanine, identifying residues R882 and K883 as essential for mitochondrial localization. Constructs containing the RK882-883AA mutation primarily localized with the endoplasmic reticulum (ER). To determine if ER-associated mutant MyMOMA domain and mitochondria-associated wild type MyMOMA display differences in kinetics of membrane interaction, we paired FRAP analysis with permeabilization activated reduction in fluorescence (PARF) analysis. Mitochondria-bound and ER-bound MYO19 constructs displayed slow dissociation from their target membrane when assayed by PARF; both constructs displayed exchange within their respective organelle networks. However, ER-bound mutant MYO19 displayed more rapid exchange within the ER network than did mitochondria-bound MYO19. Taken together these data indicate that the MyMOMA domain contains strong membrane-binding activity, and membrane targeting is mediated by a specific, basic region of the MYO19 tail with slow dissociation kinetics appropriate for its role(s) in mitochondrial network dynamics. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
| | | | - Pali P Singh
- Department of Biology, University of Richmond, VA 23173
| | - Nathan Q Wong
- Department of Biology, University of Richmond, VA 23173
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Karnkowska A, Vacek V, Zubáčová Z, Treitli SC, Petrželková R, Eme L, Novák L, Žárský V, Barlow LD, Herman EK, Soukal P, Hroudová M, Doležal P, Stairs CW, Roger AJ, Eliáš M, Dacks JB, Vlček Č, Hampl V. A Eukaryote without a Mitochondrial Organelle. Curr Biol 2016; 26:1274-84. [PMID: 27185558 DOI: 10.1016/j.cub.2016.03.053] [Citation(s) in RCA: 218] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/05/2016] [Accepted: 03/23/2016] [Indexed: 11/28/2022]
Abstract
The presence of mitochondria and related organelles in every studied eukaryote supports the view that mitochondria are essential cellular components. Here, we report the genome sequence of a microbial eukaryote, the oxymonad Monocercomonoides sp., which revealed that this organism lacks all hallmark mitochondrial proteins. Crucially, the mitochondrial iron-sulfur cluster assembly pathway, thought to be conserved in virtually all eukaryotic cells, has been replaced by a cytosolic sulfur mobilization system (SUF) acquired by lateral gene transfer from bacteria. In the context of eukaryotic phylogeny, our data suggest that Monocercomonoides is not primitively amitochondrial but has lost the mitochondrion secondarily. This is the first example of a eukaryote lacking any form of a mitochondrion, demonstrating that this organelle is not absolutely essential for the viability of a eukaryotic cell.
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Affiliation(s)
- Anna Karnkowska
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic; Department of Molecular Phylogenetics and Evolution, University of Warsaw, Warsaw 00478, Poland.
| | - Vojtěch Vacek
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Zuzana Zubáčová
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Sebastian C Treitli
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Romana Petrželková
- Department of Biology and Ecology, University of Ostrava, Ostrava 710 00, Czech Republic
| | - Laura Eme
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Lukáš Novák
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Vojtěch Žárský
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Lael D Barlow
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Emily K Herman
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Petr Soukal
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Miluše Hroudová
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague 14220, Czech Republic
| | - Pavel Doležal
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic
| | - Courtney W Stairs
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Andrew J Roger
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Marek Eliáš
- Department of Biology and Ecology, University of Ostrava, Ostrava 710 00, Czech Republic
| | - Joel B Dacks
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Čestmír Vlček
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague 14220, Czech Republic
| | - Vladimír Hampl
- Department of Parasitology, Charles University in Prague, Prague 12843, Czech Republic.
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de Marcos Lousa C, Soubeyrand E, Bolognese P, Wattelet-Boyer V, Bouyssou G, Marais C, Boutté Y, Filippini F, Moreau P. Subcellular localization and trafficking of phytolongins (non-SNARE longins) in the plant secretory pathway. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:2627-2639. [PMID: 26962210 PMCID: PMC4861013 DOI: 10.1093/jxb/erw094] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
SNARE proteins are central elements of the machinery involved in membrane fusion of eukaryotic cells. In animals and plants, SNAREs have diversified to sustain a variety of specific functions. In animals, R-SNARE proteins called brevins have diversified; in contrast, in plants, the R-SNARE proteins named longins have diversified. Recently, a new subfamily of four longins named 'phytolongins' (Phyl) was discovered. One intriguing aspect of Phyl proteins is the lack of the typical SNARE motif, which is replaced by another domain termed the 'Phyl domain'. Phytolongins have a rather ubiquitous tissue expression in Arabidopsis but still await intracellular characterization. In this study, we found that the four phytolongins are distributed along the secretory pathway. While Phyl2.1 and Phyl2.2 are strictly located at the endoplasmic reticulum network, Phyl1.2 associates with the Golgi bodies, and Phyl1.1 locates mainly at the plasma membrane and partially in the Golgi bodies and post-Golgi compartments. Our results show that export of Phyl1.1 from the endoplasmic reticulum depends on the GTPase Sar1, the Sar1 guanine nucleotide exchange factor Sec12, and the SNAREs Sec22 and Memb11. In addition, we have identified the Y48F49 motif as being critical for the exit of Phyl1.1 from the endoplasmic reticulum. Our results provide the first characterization of the subcellular localization of the phytolongins, and we discuss their potential role in regulating the secretory pathway.
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Affiliation(s)
- Carine de Marcos Lousa
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK Faculty of Clinical and Applied Sciences, School of Biomedical Sciences, Leeds Beckett University, Portland Building 611, Leeds Beckett University City Campus, LS1 3HE, Leeds, UK
| | - Eric Soubeyrand
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France
| | - Paolo Bolognese
- Molecular Biology and Bioinformatics Unit, Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy
| | - Valerie Wattelet-Boyer
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France
| | - Guillaume Bouyssou
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France
| | - Claireline Marais
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France
| | - Yohann Boutté
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France
| | - Francesco Filippini
- Molecular Biology and Bioinformatics Unit, Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy
| | - Patrick Moreau
- CNRS-University of Bordeaux, UMR 5200 Membrane Biogenesis Laboratory, INRA Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux, CS 20032, 33140 Villenave d'Ornon, France Bordeaux Imaging Center, UMS 3420 CNRS, US004 INSERM, University of Bordeaux, 33000 Bordeaux, France
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65
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Liang M, Li H, Zhou F, Li H, Liu J, Hao Y, Wang Y, Zhao H, Han S. Subcellular Distribution of NTL Transcription Factors inArabidopsis thaliana. Traffic 2015. [DOI: 10.1111/tra.12311] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Mingwei Liang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Hongjuan Li
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Fang Zhou
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Huiyong Li
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Jin Liu
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Yi Hao
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Yingdian Wang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Heping Zhao
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
| | - Shengcheng Han
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences; Beijing Normal University; Beijing 100875 China
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Yamamoto Y, Sakisaka T. The emerging role of calcium-modulating cyclophilin ligand in posttranslational insertion of tail-anchored proteins into the endoplasmic reticulum membrane. J Biochem 2015; 157:419-29. [PMID: 25869254 DOI: 10.1093/jb/mvv035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 02/18/2015] [Indexed: 01/08/2023] Open
Abstract
Tail-anchored (TA) proteins, a class of membrane proteins having an N-terminal cytoplasmic region anchored to the membrane by a single C-terminal transmembrane domain, are posttranslationally inserted into the endoplasmic reticulum (ER) membrane. In yeasts, the posttranslational membrane insertion is mediated by the Guided Entry of TA Proteins (GET) complex. Get3, a cytosolic ATPase, targets newly synthesized TA proteins to the ER membrane, where Get2 and Get3 constitute the Get3 receptor driving the membrane insertion. While mammalian cells employ TRC40 and WRB, mammalian homologs of Get3 and Get1, respectively, they lack the gene homologous to Get2. We recently identified calcium-modulating cyclophilin ligand (CAML) as a TRC40 receptor, indicating that CAML was equivalent to Get2 in the context of the membrane insertion. On the other hand, CAML has been well characterized as a signaling molecule that regulates various biological processes, raising the question of how the two distinct actions of CAML, the membrane insertion and the signal transduction, are assembled. In this review, we summarize recent progress of the molecular mechanism of the membrane insertion of TA proteins and discuss the possibility that CAML could sense the various signals at the ER membrane, thereby controlling TA protein biogenesis.
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Affiliation(s)
- Yasunori Yamamoto
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Toshiaki Sakisaka
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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Bernier SC, Horchani H, Salesse C. Structure and binding of the C-terminal segment of R9AP to lipid monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1967-1979. [PMID: 25614992 DOI: 10.1021/la503867h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Phototransduction cascade takes place in disc membranes of photoreceptor cells. Following its activation by light, rhodopsin activates the G-protein transducin causing the dissociation of its GTP-bound α-subunit, which in turn activates phosphodiesterase 6 (PDE6) leading to the hyperpolarization of photoreceptor cells. PDE6 must then be inactivated to return to the dark state. This is achieved by a protein complex which is presumably anchored to photoreceptor disc membranes by means of the transmembrane C-terminal segment of RGS9-1-Anchor Protein (R9AP). Information on the secondary structure and membrane binding properties of the C-terminal segment of R9AP is not yet available to further support its role in the membrane anchoring of this protein. In the present study, circular dichroism and infrared spectroscopy measurements have allowed us to determine that the C-terminal segment of human and bovine R9AP adopts an α-helical structure in solution. Moreover, this C-terminal segment has shown affinity for most of the phospholipids typical of photoreceptor membranes. In fact, the physical state and the type of phospholipid as well as electrostatic interactions influence the binding of the human and bovine peptides to phospholipid monolayers. In addition, these measurements revealed that the human peptide has a high affinity for saturated phosphocholine, which may suggest a possible localization of R9AP in photoreceptor microdomains. Accordingly, infrared spectroscopy measurements have allowed determining that the C-terminal segment of R9AP adopts an ordered α-helical structure in the presence of saturated phospholipid monolayers. Altogether, these data are consistent with the typical α-helical secondary structure and behavior observed for transmembrane segments and with the proposed role of membrane anchoring of the C-terminal segment of human and bovine R9AP.
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Affiliation(s)
- Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval , Québec (Québec) Canada
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68
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Hydrophobic mismatch sorts SNARE proteins into distinct membrane domains. Nat Commun 2015; 6:5984. [PMID: 25635869 PMCID: PMC4313621 DOI: 10.1038/ncomms6984] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 11/28/2014] [Indexed: 12/12/2022] Open
Abstract
The clustering of proteins and lipids in distinct microdomains is emerging as an important principle for the spatial patterning of biological membranes. Such domain formation can be the result of hydrophobic and ionic interactions with membrane lipids as well as of specific protein–protein interactions. Here using plasma membrane-resident SNARE proteins as model, we show that hydrophobic mismatch between the length of transmembrane domains (TMDs) and the thickness of the lipid membrane suffices to induce clustering of proteins. Even when the TMDs differ in length by only a single residue, hydrophobic mismatch can segregate structurally closely homologous membrane proteins in distinct membrane domains. Domain formation is further fine-tuned by interactions with polyanionic phosphoinositides and homo and heterotypic protein interactions. Our findings demonstrate that hydrophobic mismatch contributes to the structural organization of membranes. Clustering of proteins in the plasma membrane plays an important role in the regulation of both cellular signalling and membrane remodelling. Milovanovic et al. demonstrate that mismatch between transmembrane domain length and the lipid bilayer thickness is sufficient to drive clustering of SNARE proteins.
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69
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Chen Y, Pieuchot L, Loh RA, Yang J, Kari TMA, Wong JY, Jedd G. Hydrophobic handoff for direct delivery of peroxisome tail-anchored proteins. Nat Commun 2014; 5:5790. [PMID: 25517356 DOI: 10.1038/ncomms6790] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023] Open
Abstract
Tail-anchored (TA) proteins are inserted into membranes post-translationally through a C-terminal transmembrane domain (TMD). The PEX19 protein binds peroxisome TA proteins in the cytoplasm and delivers them to the membrane through the PEX3 receptor protein. An amphipathic segment in PEX19 promotes docking on PEX3. However, how this leads to substrate insertion is unknown. Here we reconstitute peroxisome TA protein biogenesis into two sequential steps of substrate TMD engagement and membrane insertion. We identify a series of previously uncharacterized amphipathic segments in PEX19 and identify one whose hydrophobicity is required for membrane insertion, but not TMD chaperone activity or PEX3 binding. A membrane-proximal hydrophobic surface of PEX3 promotes an unconventional form of membrane intercalation, and is also required for TMD insertion. Together, these data support a mechanism in which hydrophobic moieties in the TMD chaperone and its membrane-associated receptor act in a concerted manner to prompt TMD release and membrane insertion.
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Affiliation(s)
- Yinxiao Chen
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Laurent Pieuchot
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Rachel Ann Loh
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jing Yang
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Teuku Mahfuzh Aufar Kari
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jie Yun Wong
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Gregory Jedd
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
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70
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Structural and functional characterization of ybr137wp implicates its involvement in the targeting of tail-anchored proteins to membranes. Mol Cell Biol 2014; 34:4500-12. [PMID: 25288638 DOI: 10.1128/mcb.00697-14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nearly 5% of membrane proteins are guided to nuclear, endoplasmic reticulum (ER), mitochondrial, Golgi, or peroxisome membranes by their C-terminal transmembrane domain and are classified as tail-anchored (TA) membrane proteins. In Saccharomyces cerevisiae, the guided entry of TA protein (GET) pathway has been shown to function in the delivery of TA proteins to the ER. The sorting complex for this pathway is comprised of Sgt2, Get4, and Get5 and facilitates the loading of nascent tail-anchored proteins onto the Get3 ATPase. Multiple pulldown assays also indicated that Ybr137wp associates with this complex in vivo. Here, we report a 2.8-Å-resolution crystal structure for Ybr137wp from Saccharomyces cerevisiae. The protein is a decamer in the crystal and also in solution, as observed by size exclusion chromatography and analytical ultracentrifugation. In addition, isothermal titration calorimetry indicated that the C-terminal acidic motif of Ybr137wp interacts with the tetratricopeptide repeat (TPR) domain of Sgt2. Moreover, an in vivo study demonstrated that Ybr137wp is induced in yeast exiting the log phase and ameliorates the defect of TA protein delivery and cell viability derived by the impaired GET system under starvation conditions. Therefore, this study suggests a possible role for Ybr137wp related to targeting of tail-anchored proteins.
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71
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Chen YC, Umanah GKE, Dephoure N, Andrabi SA, Gygi SP, Dawson TM, Dawson VL, Rutter J. Msp1/ATAD1 maintains mitochondrial function by facilitating the degradation of mislocalized tail-anchored proteins. EMBO J 2014; 33:1548-64. [PMID: 24843043 DOI: 10.15252/embj.201487943] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The majority of ER-targeted tail-anchored (TA) proteins are inserted into membranes by the Guided Entry of Tail-anchored protein (GET) system. Disruption of this system causes a subset of TA proteins to mislocalize to mitochondria. We show that the AAA+ ATPase Msp1 limits the accumulation of mislocalized TA proteins on mitochondria. Deletion of MSP1 causes the Pex15 and Gos1 TA proteins to accumulate on mitochondria when the GET system is impaired. Likely as a result of failing to extract mislocalized TA proteins, yeast with combined mutation of the MSP1 gene and the GET system exhibit strong synergistic growth defects and severe mitochondrial damage, including loss of mitochondrial DNA and protein and aberrant mitochondrial morphology. Like yeast Msp1, human ATAD1 limits the mitochondrial mislocalization of PEX26 and GOS28, orthologs of Pex15 and Gos1, respectively. GOS28 protein level is also increased in ATAD1(-/-) mouse tissues. Therefore, we propose that yeast Msp1 and mammalian ATAD1 are conserved members of the mitochondrial protein quality control system that might promote the extraction and degradation of mislocalized TA proteins to maintain mitochondrial integrity.
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Affiliation(s)
- Yu-Chan Chen
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City UT, USA
| | - George K E Umanah
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Noah Dephoure
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Shaida A Andrabi
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Ted M Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA Departments of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Valina L Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jared Rutter
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City UT, USA
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Lhor M, Bernier SC, Horchani H, Bussières S, Cantin L, Desbat B, Salesse C. Comparison between the behavior of different hydrophobic peptides allowing membrane anchoring of proteins. Adv Colloid Interface Sci 2014; 207:223-39. [PMID: 24560216 PMCID: PMC4028306 DOI: 10.1016/j.cis.2014.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 01/11/2014] [Accepted: 01/13/2014] [Indexed: 10/25/2022]
Abstract
Membrane binding of proteins such as short chain dehydrogenase reductases or tail-anchored proteins relies on their N- and/or C-terminal hydrophobic transmembrane segment. In this review, we propose guidelines to characterize such hydrophobic peptide segments using spectroscopic and biophysical measurements. The secondary structure content of the C-terminal peptides of retinol dehydrogenase 8, RGS9-1 anchor protein, lecithin retinol acyl transferase, and of the N-terminal peptide of retinol dehydrogenase 11 has been deduced by prediction tools from their primary sequence as well as by using infrared or circular dichroism analyses. Depending on the solvent and the solubilization method, significant structural differences were observed, often involving α-helices. The helical structure of these peptides was found to be consistent with their presumed membrane binding. Langmuir monolayers have been used as membrane models to study lipid-peptide interactions. The values of maximum insertion pressure obtained for all peptides using a monolayer of 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE) are larger than the estimated lateral pressure of membranes, thus suggesting that they bind membranes. Polarization modulation infrared reflection absorption spectroscopy has been used to determine the structure and orientation of these peptides in the absence and in the presence of a DOPE monolayer. This lipid induced an increase or a decrease in the organization of the peptide secondary structure. Further measurements are necessary using other lipids to better understand the membrane interactions of these peptides.
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Affiliation(s)
- Mustapha Lhor
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Habib Horchani
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Sylvain Bussières
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Line Cantin
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Bernard Desbat
- CBMN-UMR 5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy Saint Hilaire, 33600 Pessac, France
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement, Département d'ophtalmologie, Faculté de médecine, Université Laval, Québec, Québec G1V 0A6, Canada; Regroupement stratégique PROTEO, Université Laval, Québec, Québec G1V 0A6, Canada.
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Lee J, Kim DH, Hwang I. Specific targeting of proteins to outer envelope membranes of endosymbiotic organelles, chloroplasts, and mitochondria. FRONTIERS IN PLANT SCIENCE 2014; 5:173. [PMID: 24808904 PMCID: PMC4010795 DOI: 10.3389/fpls.2014.00173] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 04/10/2014] [Indexed: 05/21/2023]
Abstract
Chloroplasts and mitochondria are endosymbiotic organelles thought to be derived from endosymbiotic bacteria. In present-day eukaryotic cells, these two organelles play pivotal roles in photosynthesis and ATP production. In addition to these major activities, numerous reactions, and cellular processes that are crucial for normal cellular functions occur in chloroplasts and mitochondria. To function properly, these organelles constantly communicate with the surrounding cellular compartments. This communication includes the import of proteins, the exchange of metabolites and ions, and interactions with other organelles, all of which heavily depend on membrane proteins localized to the outer envelope membranes. Therefore, correct and efficient targeting of these membrane proteins, which are encoded by the nuclear genome and translated in the cytosol, is critically important for organellar function. In this review, we summarize the current knowledge of the mechanisms of protein targeting to the outer membranes of mitochondria and chloroplasts in two different directions, as well as targeting signals and cytosolic factors.
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Affiliation(s)
- Junho Lee
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Dae Heon Kim
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Inhwan Hwang
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Division of Integrative Biosciences and Bioengineering, Pohang University of Science and TechnologyPohang, South Korea
- *Correspondence: Inhwan Hwang, Cellular Systems Biology, Department of Life Sciences and Division of Integrative Biosciences and Bioengineering, Pohang University of Science and Technology, Hyojadong, Nam-Gu, Pohang 790-784, South Korea e-mail:
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Marty NJ, Teresinski HJ, Hwang YT, Clendening EA, Gidda SK, Sliwinska E, Zhang D, Miernyk JA, Brito GC, Andrews DW, Dyer JM, Mullen RT. New insights into the targeting of a subset of tail-anchored proteins to the outer mitochondrial membrane. FRONTIERS IN PLANT SCIENCE 2014; 5:426. [PMID: 25237314 PMCID: PMC4154396 DOI: 10.3389/fpls.2014.00426] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 08/12/2014] [Indexed: 05/21/2023]
Abstract
Tail-anchored (TA) proteins are a unique class of functionally diverse membrane proteins defined by their single C-terminal membrane-spanning domain and their ability to insert post-translationally into specific organelles with an Ncytoplasm-Corganelle interior orientation. The molecular mechanisms by which TA proteins are sorted to the proper organelles are not well-understood. Herein we present results indicating that a dibasic targeting motif (i.e., -R-R/K/H-X({X≠E})) identified previously in the C terminus of the mitochondrial isoform of the TA protein cytochrome b 5, also exists in many other A. thaliana outer mitochondrial membrane (OMM)-TA proteins. This motif is conspicuously absent, however, in all but one of the TA protein subunits of the translocon at the outer membrane of mitochondria (TOM), suggesting that these two groups of proteins utilize distinct biogenetic pathways. Consistent with this premise, we show that the TA sequences of the dibasic-containing proteins are both necessary and sufficient for targeting to mitochondria, and are interchangeable, while the TA regions of TOM proteins lacking a dibasic motif are necessary, but not sufficient for localization, and cannot be functionally exchanged. We also present results from a comprehensive mutational analysis of the dibasic motif and surrounding sequences that not only greatly expands the functional definition and context-dependent properties of this targeting signal, but also led to the identification of other novel putative OMM-TA proteins. Collectively, these results provide important insight to the complexity of the targeting pathways involved in the biogenesis of OMM-TA proteins and help define a consensus targeting motif that is utilized by at least a subset of these proteins.
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Affiliation(s)
- Naomi J. Marty
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
| | - Howard J. Teresinski
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
| | - Yeen Ting Hwang
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
| | - Eric A. Clendening
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
| | - Satinder K. Gidda
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
| | - Elwira Sliwinska
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
- Department of Plant Genetics, Physiology and Biotechnology, University of Technology and Life Sciences in BydgoszczBydgoszcz, Poland
| | - Daiyuan Zhang
- United States Department of Agriculture, Agricultural Research Service, US Arid-Land Agricultural Research CenterMaricopa, AZ, USA
| | - Ján A. Miernyk
- United States Department of Agriculture, Agricultural Research Service, Plant Genetics Research Unit, University of MissouriColumbia, MO, USA
| | - Glauber C. Brito
- Instituto do Cancer do Estado de Sao Paulo, Fundacao Faculdade de Medicina, Universidade de Sao PauloSao Paulo, Brazil
| | - David W. Andrews
- Sunnybrook Research Institute and Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - John M. Dyer
- United States Department of Agriculture, Agricultural Research Service, US Arid-Land Agricultural Research CenterMaricopa, AZ, USA
| | - Robert T. Mullen
- Department of Molecular and Cellular Biology, University of GuelphGuelph, ON, Canada
- *Correspondence: Robert T. Mullen, Department of Molecular and Cellular, Biology, University of Guelph, Room 4470 Science Complex, 488 Gordon Street, Guelph, ON N1G 2W1, Canada e-mail:
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75
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Arias DG, Marquez VE, Chiribao ML, Gadelha FR, Robello C, Iglesias AA, Guerrero SA. Redox metabolism in Trypanosoma cruzi: functional characterization of tryparedoxins revisited. Free Radic Biol Med 2013; 63:65-77. [PMID: 23665397 DOI: 10.1016/j.freeradbiomed.2013.04.036] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 04/04/2013] [Accepted: 04/30/2013] [Indexed: 01/01/2023]
Abstract
Tryparedoxins (TXNs) are multipurpose oxidoreductases from trypanosomatids that transfer reducing equivalents from trypanothione to various thiol proteins. In Trypanosoma cruzi, two genes coding for TXN-like proteins have been identified: TXNI, previously characterized as a cytoplasmic protein, and TXNII, a putative tail-anchored membrane protein. In this work, we performed a comparative functional characterization of T. cruzi TXNs. Particularly, we cloned the gene region coding for the soluble version of TXNII for its heterologous expression. The truncated recombinant protein (without its 22 C-terminal transmembrane amino acids) showed TXN activity. It was also able to transfer reducing equivalents from trypanothione, glutathione, or dihydrolipoamide to various acceptors, including methionine sulfoxide reductases and peroxiredoxins. The results support the occurrence and functionality of a second tryparedoxin, which appears as a new component in the redox scenario for T. cruzi.
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Affiliation(s)
- Diego G Arias
- Instituto de Agrobiotecnología del Litoral, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral-CONICET, 3000 Santa Fe, Argentina
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76
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Tung JY, Li YC, Lin TW, Hsiao CD. Structure of the Sgt2 dimerization domain complexed with the Get5 UBL domain involved in the targeting of tail-anchored membrane proteins to the endoplasmic reticulum. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:2081-90. [PMID: 24100326 DOI: 10.1107/s0907444913019379] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 07/13/2013] [Indexed: 11/10/2022]
Abstract
The insertion of tail-anchored membrane (TA) proteins into the appropriate membrane is a post-translational event that requires stabilization of the transmembrane domain and targeting to the proper destination. Sgt2, a small glutamine-rich tetratricopeptide-repeat protein, is a heat-shock protein cognate (HSC) co-chaperone that preferentially binds endoplasmic reticulum-destined TA proteins and directs them to the GET pathway via Get4 and Get5. The N-terminal domain of Sgt2 seems to exert dual functions. It mediates Get5 interaction and allows substrate delivery to Get3. Following the N-terminus of Get5 is a ubiquitin-like (Ubl) domain that interacts with the N-terminus of Sgt2. Here, the crystal structure of the Sgt2 dimerization domain complexed with the Get5 Ubl domain (Sgt2N-Get5Ubl) is reported. This complex reveals an intimate interaction between one Sgt2 dimer and one Get5 monomer. This research further demonstrates that hydrophobic residues from both Sgt2 and Get5 play an important role in cell survival under heat stress. This study provides detailed molecular insights into the specific binding of this GET-pathway complex.
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Affiliation(s)
- Jung-Yu Tung
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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77
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Ring BA, Ferreira Lacerda A, Drummond DJ, Wangen C, Eaton HE, Brunetti CR. Frog virus 3 open reading frame 97R localizes to the endoplasmic reticulum and induces nuclear invaginations. J Virol 2013; 87:9199-207. [PMID: 23760249 PMCID: PMC3754063 DOI: 10.1128/jvi.00637-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 06/08/2013] [Indexed: 12/18/2022] Open
Abstract
Frog virus 3 (FV3) is the type species of the genus Ranavirus, family Iridoviridae. The genome of FV3 is 105,903 bases in length and encodes 97 open reading frames (ORFs). The FV3 ORF 97R contains a B-cell lymphoma 2 (Bcl-2) homology 1 (BH1) domain and has sequence similarity to the myeloid cell leukemia-1 (Mcl-1) protein, suggesting a potential role in apoptosis. To begin to understand the role of 97R, we characterized 97R through immunofluorescence and mutagenesis. Here we demonstrated that 97R localized to the endoplasmic reticulum (ER) at 24 h posttransfection. However, at 35 h posttransfection, 97R localized to the ER but also began to form concentrated pockets continuous with the nuclear membrane. After 48 h posttransfection, 97R was still localized to the ER, but we began to observe the ER and the outer nuclear membrane invaginating into the nucleus. To further explore 97R targeting to the ER, we created a series of C-terminal transmembrane domain deletion mutants. We found that deletion of 29 amino acids from the C terminus of 97R abolished localization to the ER. In contrast, deletion of 12 amino acids from the C terminus of 97R did not affect 97R localization to the ER. In addition, a hybrid protein containing the 97R C-terminal 33 amino acids was similarly targeted to the ER. These data indicate that the C-terminal 33 amino acids of 97R are necessary and sufficient for ER targeting.
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Affiliation(s)
- Brooke A Ring
- Department of Biology, Trent University, Peterborough, Ontario, Canada
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78
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Pogozheva ID, Tristram-Nagle S, Mosberg HI, Lomize AL. Structural adaptations of proteins to different biological membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2592-608. [PMID: 23811361 DOI: 10.1016/j.bbamem.2013.06.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 06/04/2013] [Accepted: 06/19/2013] [Indexed: 02/06/2023]
Abstract
To gain insight into adaptations of proteins to their membranes, intrinsic hydrophobic thicknesses, distributions of different chemical groups and profiles of hydrogen-bonding capacities (α and β) and the dipolarity/polarizability parameter (π*) were calculated for lipid-facing surfaces of 460 integral α-helical, β-barrel and peripheral proteins from eight types of biomembranes. For comparison, polarity profiles were also calculated for ten artificial lipid bilayers that have been previously studied by neutron and X-ray scattering. Estimated hydrophobic thicknesses are 30-31Å for proteins from endoplasmic reticulum, thylakoid, and various bacterial plasma membranes, but differ for proteins from outer bacterial, inner mitochondrial and eukaryotic plasma membranes (23.9, 28.6 and 33.5Å, respectively). Protein and lipid polarity parameters abruptly change in the lipid carbonyl zone that matches the calculated hydrophobic boundaries. Maxima of positively charged protein groups correspond to the location of lipid phosphates at 20-22Å distances from the membrane center. Locations of Tyr atoms coincide with hydrophobic boundaries, while distributions maxima of Trp rings are shifted by 3-4Å toward the membrane center. Distributions of Trp atoms indicate the presence of two 5-8Å-wide midpolar regions with intermediate π* values within the hydrocarbon core, whose size and symmetry depend on the lipid composition of membrane leaflets. Midpolar regions are especially asymmetric in outer bacterial membranes and cell membranes of mesophilic but not hyperthermophilic archaebacteria, indicating the larger width of the central nonpolar region in the later case. In artificial lipid bilayers, midpolar regions are observed up to the level of acyl chain double bonds.
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Affiliation(s)
- Irina D Pogozheva
- College of Pharmacy, Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109-1065, USA.
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79
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Schmeiser C, Borst E, Sticht H, Marschall M, Milbradt J. The cytomegalovirus egress proteins pUL50 and pUL53 are translocated to the nuclear envelope through two distinct modes of nuclear import. J Gen Virol 2013; 94:2056-2069. [PMID: 23740483 DOI: 10.1099/vir.0.052571-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The nucleocytoplasmic export of cytomegaloviral capsids is regulated by formation of a multi-component nuclear egress complex (NEC), essentially based on viral proteins pUL50 and pUL53. In this study, the generation of recombinant human cytomegaloviruses, expressing tagged versions of pUL50 and pUL53, enabled the investigation of NEC formation in infected primary fibroblasts. For these recombinant viruses, a wild-type-like mode of pUL50-pUL53 interaction and recruitment of both proteins to the nuclear envelope could be demonstrated. Importantly, pUL50 was translocated from an initial cytoplasmic distribution to the nuclear rim, whereas pUL53 accumulated in the nucleus before attaining overall rim colocalization with pUL50. Specified experimental settings illustrated that pUL50 and pUL53 were subject to different pathways of intracellular trafficking. Importantly, a novel nuclear localization signal (NLS) could be identified and functionally verified for pUL53 (amino acids 18-27), whereas no NLS was present in pUL50. Analysis of amino acid replacement mutants further illustrated the differential modes of nuclear import of the two essential viral egress proteins. Taken together, our findings suggest a combination of classical nuclear import (pUL53) and interaction-mediated recruitment (pUL50) as the driving forces for core NEC formation and viral nuclear egress.
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Affiliation(s)
- Cathrin Schmeiser
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Eva Borst
- Department of Virology, Hannover Medical School, Hannover, Germany
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Jens Milbradt
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
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80
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Ast T, Cohen G, Schuldiner M. A network of cytosolic factors targets SRP-independent proteins to the endoplasmic reticulum. Cell 2013; 152:1134-45. [PMID: 23452858 DOI: 10.1016/j.cell.2013.02.003] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 11/08/2012] [Accepted: 02/04/2013] [Indexed: 12/23/2022]
Abstract
Translocation into the endoplasmic reticulum (ER) is an initial and crucial biogenesis step for all secreted and endomembrane proteins in eukaryotes. ER insertion can take place through the well-characterized signal recognition particle (SRP)-dependent pathway or the less-studied route of SRP-independent translocation. To better understand the prevalence of the SRP-independent pathway, we systematically defined the translocational dependence of the yeast secretome. By combining hydropathy-based analysis and microscopy, we uncovered that a previously unappreciated fraction of the yeast secretome translocates without the aid of the SRP. Furthermore, we validated a family of SRP-independent substrates-the glycosylphosphatidylinositol (GPI)-anchored proteins. Studying this family, we identified a determinant for ER targeting and uncovered a network of cytosolic proteins that facilitate SRP-independent targeting and translocation. These findings highlight the underappreciated complexity of SRP-independent translocation, which enables this pathway to efficiently cope with its extensive substrate flux.
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Affiliation(s)
- Tslil Ast
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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81
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Yagita Y, Hiromasa T, Fujiki Y. Tail-anchored PEX26 targets peroxisomes via a PEX19-dependent and TRC40-independent class I pathway. ACTA ACUST UNITED AC 2013; 200:651-66. [PMID: 23460677 PMCID: PMC3587837 DOI: 10.1083/jcb.201211077] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tail-anchored (TA) proteins are anchored into cellular membranes by a single transmembrane domain (TMD) close to the C terminus. Although the targeting of TA proteins to peroxisomes is dependent on PEX19, the mechanistic details of PEX19-dependent targeting and the signal that directs TA proteins to peroxisomes have remained elusive, particularly in mammals. The present study shows that PEX19 formed a complex with the peroxisomal TA protein PEX26 in the cytosol and translocated it directly to peroxisomes by interacting with the peroxisomal membrane protein PEX3. Unlike in yeast, the adenosine triphosphatase TRC40, which delivers TA proteins to the endoplasmic reticulum, was dispensable for the peroxisomal targeting of PEX26. Moreover, the basic amino acids within the luminal domain of PEX26 were essential for binding to PEX19 and thereby for peroxisomal targeting. Finally, our results suggest that a TMD that escapes capture by TRC40 and is followed by a highly basic luminal domain directs TA proteins to peroxisomes via the PEX19-dependent route.
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Affiliation(s)
- Yuichi Yagita
- Graduate School of Systems Life Sciences, Faculty of Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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82
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Venkatakrishnan S, Mackey D, Meier I. Functional investigation of the plant-specific long coiled-coil proteins PAMP-INDUCED COILED-COIL (PICC) and PICC-LIKE (PICL) in Arabidopsis thaliana. PLoS One 2013; 8:e57283. [PMID: 23451199 PMCID: PMC3581476 DOI: 10.1371/journal.pone.0057283] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 01/23/2013] [Indexed: 12/20/2022] Open
Abstract
We have identified and characterized two Arabidopsis long coiled-coil proteins PAMP-INDUCED COILED-COIL (PICC) and PICC-LIKE (PICL). PICC (147 kDa) and PICL (87 kDa) are paralogs that consist predominantly of a long coiled-coil domain (expanded in PICC), with a predicted transmembrane domain at the immediate C-terminus. Orthologs of PICC and PICL were found exclusively in vascular plants. PICC and PICL GFP fusion proteins are anchored to the cytoplasmic surface of the endoplasmic reticulum (ER) membrane by a C-terminal transmembrane domain and a short tail domain, via a tail-anchoring mechanism. T-DNA-insertion mutants of PICC and PICL as well as the double mutant show an increased sensitivity to the plant abiotic stress hormone abscisic acid (ABA) in a post-germination growth response. PICC, but not PICL gene expression is induced by the bacterial pathogen-associated molecular pattern (PAMP) flg22. T-DNA insertion alleles of PICC, but not PICL, show increased susceptibility to the non-virulent strain P. syringae pv. tomato DC3000 hrcC, but not to the virulent strain P. syringae pv. tomato DC3000. This suggests that PICC mutants are compromised in PAMP-triggered immunity (PTI). The data presented here provide first evidence for the involvement of a plant long coiled-coil protein in a plant defense response.
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Affiliation(s)
- Sowmya Venkatakrishnan
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - David Mackey
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio, United States of America
| | - Iris Meier
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
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83
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Itakura E, Kishi-Itakura C, Mizushima N. The hairpin-type tail-anchored SNARE syntaxin 17 targets to autophagosomes for fusion with endosomes/lysosomes. Cell 2013; 151:1256-69. [PMID: 23217709 DOI: 10.1016/j.cell.2012.11.001] [Citation(s) in RCA: 910] [Impact Index Per Article: 82.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 08/20/2012] [Accepted: 10/16/2012] [Indexed: 12/14/2022]
Abstract
The lysosome is a degradative organelle, and its fusion with other organelles is strictly regulated. In contrast to fusion with the late endosome, the mechanisms underlying autophagosome-lysosome fusion remain unknown. Here, we identify syntaxin 17 (Stx17) as the autophagosomal SNARE required for fusion with the endosome/lysosome. Stx17 localizes to the outer membrane of completed autophagosomes but not to the isolation membrane (unclosed intermediate structures); for this reason, the lysosome does not fuse with the isolation membrane. Stx17 interacts with SNAP-29 and the endosomal/lysosomal SNARE VAMP8. Depletion of Stx17 causes accumulation of autophagosomes without degradation. Stx17 has a unique C-terminal hairpin structure mediated by two tandem transmembrane domains containing glycine zipper-like motifs, which is essential for its association with the autophagosomal membrane. These findings reveal a mechanism by which the SNARE protein is available to the completed autophagosome.
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Affiliation(s)
- Eisuke Itakura
- Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
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84
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Krumpe K, Rapaport D. An assay to monitor the membrane integration of single-span proteins. Methods Mol Biol 2013; 1033:301-306. [PMID: 23996185 DOI: 10.1007/978-1-62703-487-6_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In vitro import experiments with isolated organelles are a powerful tool for investigation of the biogenesis of proteins. A key issue in such experiments is an assay to distinguish between correctly and incorrectly imported proteins. Here we describe an assay to monitor in vitro the proper membrane integration of single-span proteins. In this assay non-imported proteins are distinguished from correctly imported protein species by labelling of unprotected cysteine residues and a resulting migration shift in SDS-PAGE.
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Affiliation(s)
- Katrin Krumpe
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
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85
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Yamamoto Y, Sakisaka T. Molecular Machinery for Insertion of Tail-Anchored Membrane Proteins into the Endoplasmic Reticulum Membrane in Mammalian Cells. Mol Cell 2012; 48:387-97. [DOI: 10.1016/j.molcel.2012.08.028] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 07/02/2012] [Accepted: 08/27/2012] [Indexed: 11/27/2022]
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86
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Brambillasca S, Altkrueger A, Colombo SF, Friederich A, Eickelmann P, Mark M, Borgese N, Solimena M. CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1) is a tail-anchored protein in the endoplasmic reticulum (ER) of insulinoma cells. J Biol Chem 2012; 287:41808-19. [PMID: 23048041 DOI: 10.1074/jbc.m112.376558] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genome-wide association studies have led to the identification of numerous susceptibility genes for type 2 diabetes. Among them is Cdkal1, which is associated with reduced β-cell function and insulin release. Recently, CDKAL1 has been shown to be a methylthiotransferase that modifies tRNA(Lys) to enhance translational fidelity of transcripts, including the one encoding proinsulin. Here, we report that out of several CDKAL1 isoforms deposited in public databases, only isoform 1, which migrates as a 61-kDa protein by SDS-PAGE, is expressed in human islets and pancreatic insulinoma INS-1 and MIN6 cells. We show that CDKAL1 is a novel member of the tail-anchored protein family and exploits the TCR40/Get3-assisted pathway for insertion of its C-terminal transmembrane domain into the endoplasmic reticulum. Using endo-β-N-acetylglucosaminidase H and peptide:N-glycosidase F sensitivity assays on CDKAL1 constructs carrying an N-glycosylation site within the luminal domain, we further established that CDKAL1 is an endoplasmic reticulum-resident protein. Moreover, we observed that silencing CDKAL1 in INS-1 cells reduces the expression of secretory granule proteins prochromogranin A and proICA512/ICA512-TMF, in addition to proinsulin and insulin. This correlated with reduced glucose-stimulated insulin secretion. Taken together, our findings provide new insight into the role of CDKAL1 in insulin-producing cells and help to understand its involvement in the pathogenesis of diabetes.
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Affiliation(s)
- Silvia Brambillasca
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus, Dresden University of Technology, Fetscherstrasse 74, 01307 Dresden, Germany
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87
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Li Y, Li LL, Fan RC, Peng CC, Sun HL, Zhu SY, Wang XF, Zhang LY, Zhang DP. Arabidopsis sucrose transporter SUT4 interacts with cytochrome b5-2 to regulate seed germination in response to sucrose and glucose. MOLECULAR PLANT 2012; 5:1029-41. [PMID: 22311778 DOI: 10.1093/mp/sss001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
It remains unknown whether a sucrose transporter mediates sugar signaling. Here, we report that the Arabidopsis (Arabidopsis thaliana) sucrose transporter SUT4 interacts with five members of the Arabidopsis cytochrome b5 (Cyb5) family, and sucrose represses the interaction between SUT4 and a Cyb5 member Cyb5-2/A. We observed that down-regulation of SUT4 and three cytochrome b5 members (Cyb5-2, Cyb5-4, and Cyb5-6) confers the sucrose- and glucose-insensitive phenotypes in the sucrose/glucose-induced inhibition of seed germination. The sut4 cyb5-2 double mutant displays slightly stronger sucrose/glucose-insensitive phenotypes than either the sut4 or cyb5-2 single mutant. We showed that the SUT4/Cyb5-2-mediated signaling in the sucrose/glucose-induced inhibition of seed germination does not require ABA or the currently known ABI2/ABI4/ABI5-mediated signaling pathway(s). These data provide evidence that the sucrose transporter SUT4 interacts with Cyb5 to positively mediate sucrose and glucose signaling in the sucrose/glucose-induced inhibition of seed germination.
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Affiliation(s)
- Yan Li
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
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88
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Krumpe K, Frumkin I, Herzig Y, Rimon N, Özbalci C, Brügger B, Rapaport D, Schuldiner M. Ergosterol content specifies targeting of tail-anchored proteins to mitochondrial outer membranes. Mol Biol Cell 2012; 23:3927-35. [PMID: 22918956 PMCID: PMC3469509 DOI: 10.1091/mbc.e11-12-0994] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial outer membrane tail-anchored proteins are a unique class of membrane proteins with unknown targeting mechanism. Using two high-throughput microscopy screens, we demonstrate that the inherent differences in membrane composition between organelle membranes is enough to determine membrane integration specificity in a living cell. Tail-anchored (TA) proteins have a single C-terminal transmembrane domain, making their biogenesis dependent on posttranslational translocation. Despite their importance, no dedicated insertion machinery has been uncovered for mitochondrial outer membrane (MOM) TA proteins. To decipher the molecular mechanisms guiding MOM TA protein insertion, we performed two independent systematic microscopic screens in which we visualized the localization of model MOM TA proteins on the background of mutants in all yeast genes. We could find no mutant in which insertion was completely blocked. However, both screens demonstrated that MOM TA proteins were partially localized to the endoplasmic reticulum (ER) in ∆spf1 cells. Spf1, an ER ATPase with unknown function, is the first protein shown to affect MOM TA protein insertion. We found that ER membranes in ∆spf1 cells become similar in their ergosterol content to mitochondrial membranes. Indeed, when we visualized MOM TA protein distribution in yeast strains with reduced ergosterol content, they phenocopied the loss of Spf1. We therefore suggest that the inherent differences in membrane composition between organelle membranes are sufficient to determine membrane integration specificity in a eukaryotic cell.
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Affiliation(s)
- Katrin Krumpe
- Interfaculty Institute of Biochemistry, University of Tübingen, 72076 Tübingen, Germany
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Sun F, Carrie C, Law S, Murcha MW, Zhang R, Law YS, Suen PK, Whelan J, Lim BL. AtPAP2 is a tail-anchored protein in the outer membrane of chloroplasts and mitochondria. PLANT SIGNALING & BEHAVIOR 2012; 7:927-32. [PMID: 22751362 PMCID: PMC3474687 DOI: 10.4161/psb.20769] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
To date, Arabidopsis purple acid phosphatase 2 (AtPAP2) is the only known plant protein that is dual-targeted to chloroplasts and mitochondria by a C-terminal targeting signal. Using in vitro organelle import and green fluorescence protein (GFP) localization assays, we showed that AtPAP2 is located on, but not imported across the outer membrane (OM) of chloroplasts and mitochondria and exposed its N-terminal enzymatic domain to the cytosol. It was also found that a short stretch of 30 amino acids (a.a.) at the C-terminal region (a.a. 615-644) that contains a stretch of 18 hydrophobic residues, a WYAK motif and 8 hydrophilic residues is sufficient for dual-targeting. Mutation of WYAK to WYAE had no effect on dual-targeting ability suggesting that the charge within this flanking region alone is not an important determinant for dual-targeting.
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Affiliation(s)
- Feng Sun
- School of Biological Sciences; The University of Hong Kong; Pokfulam, Hong Kong, China
| | - Chris Carrie
- Australian Research Council Centre of Excellence in Plant Energy Biology; University of Western Australia; Crawley, WA Australia
| | - Simon Law
- Australian Research Council Centre of Excellence in Plant Energy Biology; University of Western Australia; Crawley, WA Australia
| | - Monika W. Murcha
- Australian Research Council Centre of Excellence in Plant Energy Biology; University of Western Australia; Crawley, WA Australia
| | - Renshan Zhang
- School of Biological Sciences; The University of Hong Kong; Pokfulam, Hong Kong, China
| | - Yee Song Law
- School of Biological Sciences; The University of Hong Kong; Pokfulam, Hong Kong, China
| | - Pui Kit Suen
- School of Biological Sciences; The University of Hong Kong; Pokfulam, Hong Kong, China
| | - James Whelan
- Australian Research Council Centre of Excellence in Plant Energy Biology; University of Western Australia; Crawley, WA Australia
| | - Boon Leong Lim
- School of Biological Sciences; The University of Hong Kong; Pokfulam, Hong Kong, China
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90
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Subcellular localization of iron and heme metabolism related proteins at early stages of erythrophagocytosis. PLoS One 2012; 7:e42199. [PMID: 22860081 PMCID: PMC3408460 DOI: 10.1371/journal.pone.0042199] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 07/02/2012] [Indexed: 12/26/2022] Open
Abstract
Background Senescent red blood cells (RBC) are recognized, phagocytosed and cleared by tissue macrophages. During this erythrophagocytosis (EP), RBC are engulfed and processed in special compartments called erythrophagosomes. We previously described that following EP, heme is rapidly degraded through the catabolic activity of heme oxygenase (HO). Extracted heme iron is then either exported or stored by macrophages. However, the cellular localization of the early steps of heme processing and iron extraction during EP remains to be clearly defined. Methodology/Principal Findings We took advantage of our previously described cellular model of EP, using bone marrow-derived macrophages (BMDM). The subcellular localization of both inducible and constitutive isoforms of HO (HO-1 and HO-2), of the divalent metal transporters (Nramp1, Nramp2/DMT1, Fpn), and of the recently identified heme transporter HRG-1, was followed by fluorescence and electron microscopy during the earliest steps of EP. We also looked at some ER [calnexin, glucose-6-phosphatase (G6Pase) activity] and lysosomes (Lamp1) markers during EP. In both quiescent and LPS-activated BMDM, Nramp1 and Lamp1 were shown to be strong markers of the erythrophagolysosomal membrane. HRG-1 was also recruited to the erythrophagosome. Furthermore, we observed calnexin labeling and G6Pase activity at the erythrophagosomal membrane, indicating the contribution of ER in this phagocytosis model. In contrast, Nramp2/DMT1, Fpn, HO-1 and HO-2 were not detected at the membrane of erythrophagosomes. Conclusions/Significance Our study highlights the subcellular localization of various heme- and iron-related proteins during early steps of EP, thereby suggesting a model for heme catabolism occurring outside the phagosome, with heme likely being transported into the cytosol through HRG1. The precise function of Nramp1 at the phagosomal membrane in this model remains to be determined.
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91
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Ferrer PE, Frederick P, Gulbis JM, Dewson G, Kluck RM. Translocation of a Bak C-terminus mutant from cytosol to mitochondria to mediate cytochrome C release: implications for Bak and Bax apoptotic function. PLoS One 2012; 7:e31510. [PMID: 22442658 PMCID: PMC3307716 DOI: 10.1371/journal.pone.0031510] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 01/11/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND One of two proapoptotic Bcl-2 proteins, Bak or Bax, is required to permeabilize the mitochondrial outer membrane during apoptosis. While Bax is mostly cytosolic and translocates to mitochondria following an apoptotic stimulus, Bak is constitutively integrated within the outer membrane. Membrane anchorage occurs via a C-terminal transmembrane domain that has been studied in Bax but not in Bak, therefore what governs their distinct subcellular distribution is uncertain. In addition, whether the distinct subcellular distributions of Bak and Bax contributes to their differential regulation during apoptosis remains unclear. METHODOLOGY/PRINCIPAL FINDINGS To gain insight into Bak and Bax targeting to mitochondria, elements of the Bak C-terminus were mutated, or swapped with those of Bax. Truncation of the C-terminal six residues (C-segment) or substitution of three basic residues within the C-segment destabilized Bak. Replacing the Bak C-segment with that from Bax rescued stability and function, but unexpectedly resulted in a semi-cytosolic protein, termed Bak/BaxCS. When in the cytosol, both Bax and Bak/BaxCS sequestered their hydrophobic transmembrane domains in their hydrophobic surface groove. Upon apoptotic signalling, Bak/BaxCS translocated to the mitochondrial outer membrane, inserted its transmembrane domain, oligomerized, and released cytochrome c. Despite this Bax-like subcellular distribution, Bak/BaxCS retained Bak-like regulation following targeting of Mcl-1. CONCLUSIONS/SIGNIFICANCE Residues in the C-segment of Bak and of Bax contribute to their distinct subcellular localizations. That a semi-cytosolic form of Bak, Bak/BaxCS, could translocate to mitochondria and release cytochrome c indicates that Bak and Bax share a conserved mode of activation. In addition, the differential regulation of Bak and Bax by Mcl-1 is predominantly independent of the initial subcellular localizations of Bak and Bax.
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Affiliation(s)
- Pedro Eitz Ferrer
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Paul Frederick
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Jacqueline M. Gulbis
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Grant Dewson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Ruth M. Kluck
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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92
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The coronavirus E protein: assembly and beyond. Viruses 2012; 4:363-82. [PMID: 22590676 PMCID: PMC3347032 DOI: 10.3390/v4030363] [Citation(s) in RCA: 191] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Revised: 02/18/2012] [Accepted: 02/27/2012] [Indexed: 12/14/2022] Open
Abstract
The coronavirus E protein is a small membrane protein that has an important role in the assembly of virions. Recent studies have indicated that the E protein has functions during infection beyond assembly, including in virus egress and in the host stress response. Additionally, the E protein has ion channel activity, interacts with host proteins, and may have multiple membrane topologies. The goal of this review is to highlight the properties and functions of the E protein, and speculate on how they may be related.
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93
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Membrane integration of a mitochondrial signal-anchored protein does not require additional proteinaceous factors. Biochem J 2012; 442:381-9. [DOI: 10.1042/bj20111363] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The MOM (mitochondrial outer membrane) contains SA (signal-anchored) proteins that bear at their N-terminus a single hydrophobic segment that serves as both a mitochondrial targeting signal and an anchor at the membrane. These proteins, like the vast majority of mitochondrial proteins, are encoded in the nucleus and have to be imported into the organelle. Currently, the mechanisms by which they are targeted to and inserted into the OM (outer membrane) are unclear. To shed light on these issues, we employed a recombinant version of the SA protein OM45 and a synthetic peptide corresponding to its signal-anchor segment. Both forms are associated with isolated mitochondria independently of cytosolic factors. Interaction with mitochondria was diminished when a mutated form of the signal-anchor was employed. We demonstrate that the signal-anchor peptide acquires an α-helical structure in a lipid environment and adopted a TM (transmembrane) topology within artificial lipid bilayers. Moreover, the peptide's affinity to artificial membranes with OM-like lipid composition was much higher than that of membranes with ER (endoplasmic reticulum)-like lipid composition. Collectively, our results suggest that SA proteins are specifically inserted into the MOM by a process that is not dependent on additional proteins, but is rather facilitated by the distinct lipid composition of this membrane.
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94
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Sakamoto Y, Miura M, Takeuchi F, Park SY, Tsubaki M. Interaction of modified tail-anchored proteins with liposomes: effect of extensions of hydrophilic segment at the COOH-terminus of holo-cytochromes b₅. J Biosci Bioeng 2011; 113:322-31. [PMID: 22138382 DOI: 10.1016/j.jbiosc.2011.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 10/27/2011] [Accepted: 11/04/2011] [Indexed: 11/19/2022]
Abstract
A group of membrane proteins having a single COOH-terminal hydrophobic domain capable of post-translational insertion into lipid bilayer is known as tail-anchored (TA) proteins. To clarify the insertion mechanism of the TA-domain of human cytochrome b(5) (Hcytb5) into ER membranes, we produced and purified various membrane-bound forms of Hcytb5 with their heme b-bound, in which various truncated forms of NH(2)-terminal bovine opsin sequence were appended at the COOH-terminus of the native form. We analyzed the integration of the TA-domains of these forms onto protein-free liposomes. The integration occurred efficiently even in the presence of a small amount of sodium cholate and, once incorporated, such proteoliposomes were very stable. The mode of the integration was further analyzed by treatment of the proteoliposomes with trypsin either on the extravesicular side or on the luminal side. LC-MS analyses of the trypsin digests obtained from the proteoliposomes indicated that most of the C-terminal hydrophilic segment of the native Hcytb5 were exposed towards the lumen of the vesicles and, further, a significant part of the population of the extended C-terminal hydrophilic segments of the modified Hcytb5 were exposed in the lumen as well, suggesting efficient translocation ability of the TA-domain without any assistance from other protein factors. Present results opened a route for the use of the C-terminal TA-domain as a convenient tool for the transport of proteins as well as short peptides into artificial liposomes.
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Affiliation(s)
- Yoichi Sakamoto
- Departmemt of Chemistry, Graduate School of Science, Kobe University, Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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95
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Tail-anchor targeting by a Get3 tetramer: the structure of an archaeal homologue. EMBO J 2011; 31:707-19. [PMID: 22124326 PMCID: PMC3273380 DOI: 10.1038/emboj.2011.433] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 11/09/2011] [Indexed: 11/09/2022] Open
Abstract
Efficient delivery of membrane proteins is a critical cellular process. The recently elucidated GET (Guided Entry of TA proteins) pathway is responsible for the targeted delivery of tail-anchored (TA) membrane proteins to the endoplasmic reticulum. The central player is the ATPase Get3, which in its free form exists as a dimer. Biochemical evidence suggests a role for a tetramer of Get3. Here, we present the first crystal structure of an archaeal Get3 homologue that exists as a tetramer and is capable of TA protein binding. The tetramer generates a hydrophobic chamber that we propose binds the TA protein. We use small-angle X-ray scattering to provide the first structural information of a fungal Get3/TA protein complex showing that the overall molecular envelope is consistent with the archaeal tetramer structure. Moreover, we show that this fungal tetramer complex is capable of TA insertion. This allows us to suggest a model where a tetramer of Get3 sequesters a TA protein during targeting to the membrane.
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96
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Vilardi F, Lorenz H, Dobberstein B. WRB is the receptor for TRC40/Asna1-mediated insertion of tail-anchored proteins into the ER membrane. J Cell Sci 2011; 124:1301-7. [PMID: 21444755 PMCID: PMC3115773 DOI: 10.1242/jcs.084277] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tail-anchored (TA) proteins are post-translationally targeted to and inserted into the endoplasmic reticulum (ER) membrane through their single C-terminal transmembrane domain. Membrane insertion of TA proteins in mammalian cells is mediated by the ATPase TRC40/Asna1 (Get3 in yeast) and a receptor in the ER membrane. We have identified tryptophan-rich basic protein (WRB), also known as congenital heart disease protein 5 (CHD5), as the ER membrane receptor for TRC40/Asna1. WRB shows sequence similarity to Get1, a subunit of the membrane receptor complex for yeast Get3. Using biochemical and cell imaging approaches, we demonstrate that WRB is an ER-resident membrane protein that interacts with TRC40/Asna1 and recruits it to the ER membrane. We identify the coiled-coil domain of WRB as the binding site for TRC40/Asna1 and show that a soluble form of the coiled-coil domain interferes with TRC40/Asna1-mediated membrane insertion of TA proteins. The identification of WRB as a component of the TRC (Get) pathway for membrane insertion of TA proteins raises new questions concerning the proposed roles of WRB (CHD5) in congenital heart disease, and heart and eye development.
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Affiliation(s)
- Fabio Vilardi
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, INF282, 69120 Heidelberg, Germany
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97
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Hradsky J, Raghuram V, Reddy PP, Navarro G, Hupe M, Casado V, McCormick PJ, Sharma Y, Kreutz MR, Mikhaylova M. Post-translational membrane insertion of tail-anchored transmembrane EF-hand Ca2+ sensor calneurons requires the TRC40/Asna1 protein chaperone. J Biol Chem 2011; 286:36762-76. [PMID: 21878631 DOI: 10.1074/jbc.m111.280339] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Calneuron-1 and -2 are neuronal EF-hand-type calcium sensor proteins that are prominently targeted to trans-Golgi network membranes and impose a calcium threshold at the Golgi for phosphatidylinositol 4-OH kinase IIIβ activation and the regulated local synthesis of phospholipids that are crucial for TGN-to-plasma membrane trafficking. In this study, we show that calneurons are nonclassical type II tail-anchored proteins that are post-translationally inserted into the endoplasmic reticulum membrane via an association of a 23-amino acid-long transmembrane domain (TMD) with the TRC40/Asna1 chaperone complex. Following trafficking to the Golgi, calneurons are probably retained in the TGN because of the length of the TMD and phosphatidylinositol 4-phosphate lipid binding. Both calneurons rapidly self-associate in vitro and in vivo via their TMD and EF-hand containing the N terminus. Although dimerization and potentially multimerization precludes TRC40/Asna1 binding and thereby membrane insertion, we found no evidence for a cytosolic pool of calneurons and could demonstrate that self-association of calneurons is restricted to membrane-inserted protein. The dimerization properties and the fact that they, unlike every other EF-hand calmodulin-like Ca(2+) sensor, are always associated with membranes of the secretory pathway, including vesicles and plasma membrane, suggests a high degree of spatial segregation for physiological target interactions.
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Affiliation(s)
- Johannes Hradsky
- Research Group Neuroplasticity, Leibniz-Institute for Neurobiology, 39118 Magdeburg, Germany
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98
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Abstract
Integral membrane proteins of the cell surface and most intracellular compartments of eukaryotic cells are assembled at the endoplasmic reticulum. Two highly conserved and parallel pathways mediate membrane protein targeting to and insertion into this organelle. The classical cotranslational pathway, utilized by most membrane proteins, involves targeting by the signal recognition particle followed by insertion via the Sec61 translocon. A more specialized posttranslational pathway, employed by many tail-anchored membrane proteins, is composed of entirely different factors centered around a cytosolic ATPase termed TRC40 or Get3. Both of these pathways overcome the same biophysical challenges of ferrying hydrophobic cargo through an aqueous milieu, selectively delivering it to one among several intracellular membranes and asymmetrically integrating its transmembrane domain(s) into the lipid bilayer. Here, we review the conceptual and mechanistic themes underlying these core membrane protein insertion pathways, the complexities that challenge our understanding, and future directions to overcome these obstacles.
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Affiliation(s)
- Sichen Shao
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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99
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Stability and function of the Sec61 translocation complex depends on the Sss1p tail-anchor sequence. Biochem J 2011; 436:291-303. [PMID: 21355855 DOI: 10.1042/bj20101865] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sss1p, an essential component of the heterotrimeric Sec61 complex in the ER (endoplasmic reticulum), is a tail-anchored protein whose precise mechanism of action is largely unknown. Tail-anchored proteins are involved in many cellular processes and are characterized by a single transmembrane sequence at or near the C-terminus. The Sec61 complex is the molecular machine through which secretory and membrane proteins translocate into and across the ER membrane. To understand the function of the tail anchor of Sss1p, we introduced mutations into the tail-anchor sequence and analysed the resulting yeast phenotypes. Point mutations in the C-terminal hydrophobic core of the tail anchor of Sss1p were identified that allowed Sss1p assembly into Sec61 complexes, but resulted in diminished growth, defects in co- and post-translational translocation, inefficient ribosome binding to Sec61 complexes, reduction in the stability of both heterotrimeric Sec61 and heptameric Sec complexes and a complete breakdown of ER structure. The underlying defect caused by the mutations involves loss of a stabilizing function of the Sss1p tail-anchor sequence for both the heterotrimeric Sec61 and the heptameric Sec complexes. These results indicate that by stabilizing multiprotein membrane complexes, the hydrophobic core of a tail-anchor sequence can be more than a simple membrane anchor.
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100
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Neumann S, Langosch D. Conserved conformational dynamics of membrane fusion protein transmembrane domains and flanking regions indicated by sequence statistics. Proteins 2011; 79:2418-27. [DOI: 10.1002/prot.23063] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2011] [Revised: 03/26/2011] [Accepted: 04/19/2011] [Indexed: 11/07/2022]
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