1
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Abstract
The type-2 peroxisomal targeting signal (PTS2) is one of two peptide motifs destining soluble proteins for peroxisomes. This signal acts as amphiphilic α-helix exposing the side chains of all conserved residues to the same side. PTS2 motifs are recognized by a bipartite protein complex consisting of the receptor PEX7 and a co-receptor. Cargo-loaded receptor complexes are translocated across the peroxisomal membrane by a transient pore and inside peroxisomes, cargo proteins are released and processed in many, but not all species. The components of the bipartite receptor are re-exported into the cytosol by a ubiquitin-mediated and ATP-driven export mechanism. Structurally, PTS2 motifs resemble other N-terminal targeting signals, whereas the functional relation to the second peroxisomal targeting signal (PTS1) is unclear. Although only a few PTS2-carrying proteins are known in humans, subjects lacking a functional import mechanism for these proteins suffer from the severe inherited disease rhizomelic chondrodysplasia punctata.
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Affiliation(s)
- Markus Kunze
- Medical University of Vienna, Center for Brain Research, Department of Pathobiology of the Nervous System, Spitalgasse 4, 1090 Vienna, Austria.
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2
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Pedrosa AG, Francisco T, Ferreira MJ, Rodrigues TA, Barros-Barbosa A, Azevedo JE. A Mechanistic Perspective on PEX1 and PEX6, Two AAA+ Proteins of the Peroxisomal Protein Import Machinery. Int J Mol Sci 2019; 20:E5246. [PMID: 31652724 DOI: 10.3390/ijms20215246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 12/11/2022] Open
Abstract
In contrast to many protein translocases that use ATP or GTP hydrolysis as the driving force to transport proteins across biological membranes, the peroxisomal matrix protein import machinery relies on a regulated self-assembly mechanism for this purpose and uses ATP hydrolysis only to reset its components. The ATP-dependent protein complex in charge of resetting this machinery—the Receptor Export Module (REM)—comprises two members of the “ATPases Associated with diverse cellular Activities” (AAA+) family, PEX1 and PEX6, and a membrane protein that anchors the ATPases to the organelle membrane. In recent years, a large amount of data on the structure/function of the REM complex has become available. Here, we discuss the main findings and their mechanistic implications.
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3
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Barros-Barbosa A, Rodrigues TA, Ferreira MJ, Pedrosa AG, Teixeira NR, Francisco T, Azevedo JE. The intrinsically disordered nature of the peroxisomal protein translocation machinery. FEBS J 2018; 286:24-38. [PMID: 30443986 DOI: 10.1111/febs.14704] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/14/2018] [Indexed: 12/18/2022]
Abstract
Despite having a membrane that is impermeable to all but the smallest of metabolites, peroxisomes acquire their newly synthesized (cytosolic) matrix proteins in an already folded conformation. In some cases, even oligomeric proteins have been reported to translocate the organelle membrane. The protein sorting machinery that accomplishes this feat must be rather flexible and, unsurprisingly, several of its key components have large intrinsically disordered domains. Here, we provide an overview on these domains and their interactions trying to infer their functional roles in this protein sorting pathway.
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Affiliation(s)
- Aurora Barros-Barbosa
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Tony A Rodrigues
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Maria J Ferreira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Ana G Pedrosa
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Nélson R Teixeira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Tânia Francisco
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
| | - Jorge E Azevedo
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Portugal
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4
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Luo M, Zhuang X. Review: Selective degradation of peroxisome by autophagy in plants: Mechanisms, functions, and perspectives. Plant Sci 2018; 274:485-491. [PMID: 30080638 DOI: 10.1016/j.plantsci.2018.06.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 06/28/2018] [Accepted: 06/29/2018] [Indexed: 06/08/2023]
Abstract
Peroxisome, a single-membrane organelle conserved in eukaryotic, is responsible for a series of oxidative reactions with its specific enzymatic components. A counterbalance between peroxisome biogenesis and degradation is crucial for the homeostasis of peroxisomes. One such degradation mechanism, termed pexophagy, is a type of selective autophagic process to deliver the excess/damaged peroxisomes into the vacuole. In plants, pexophagy is involved in the remodeling of seedlings and quality control of peroxisomes. Here, we describe the recent advance in plant pexophagy, with a focus to discuss the key regulators in plants in comparison with those in yeast and mammals, as well as future directions for pexophagy studies in plants.
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Affiliation(s)
- Mengqian Luo
- Centre for Cell & Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Xiaohong Zhuang
- Centre for Cell & Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
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5
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de Abreu E Lima F, Li K, Wen W, Yan J, Nikoloski Z, Willmitzer L, Brotman Y. Unraveling lipid metabolism in maize with time-resolved multi-omics data. Plant J 2018; 93:1102-1115. [PMID: 29385634 DOI: 10.1111/tpj.13833] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 01/03/2018] [Accepted: 01/04/2018] [Indexed: 05/19/2023]
Abstract
Maize is the cereal crop with the highest production worldwide, and its oil is a key energy resource. Improving the quantity and quality of maize oil requires a better understanding of lipid metabolism. To predict the function of maize genes involved in lipid biosynthesis, we assembled transcriptomic and lipidomic data sets from leaves of B73 and the high-oil line By804 in two distinct time-series experiments. The integrative analysis based on high-dimensional regularized regression yielded lipid-transcript associations indirectly validated by Gene Ontology and promoter motif enrichment analyses. The co-localization of lipid-transcript associations using the genetic mapping of lipid traits in leaves and seedlings of a B73 × By804 recombinant inbred line population uncovered 323 genes involved in the metabolism of phospholipids, galactolipids, sulfolipids and glycerolipids. The resulting association network further supported the involvement of 50 gene candidates in modulating levels of representatives from multiple acyl-lipid classes. Therefore, the proposed approach provides high-confidence candidates for experimental testing in maize and model plant species.
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Affiliation(s)
| | - Kun Li
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Shizishan Lu 1, 430070, Hongshan, Wuhan, China
| | - Weiwei Wen
- Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam, Germany
| | - Jianbing Yan
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Shizishan Lu 1, 430070, Hongshan, Wuhan, China
| | - Zoran Nikoloski
- Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam, Germany
- Bioinformatics Group, Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14476, Potsdam, Germany
| | - Lothar Willmitzer
- Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam, Germany
| | - Yariv Brotman
- Department of Life Sciences, Ben Gurion University of the Negev, Beersheva, Israel
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6
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Kao YT, Gonzalez KL, Bartel B. Peroxisome Function, Biogenesis, and Dynamics in Plants. Plant Physiol 2018; 176:162-177. [PMID: 29021223 PMCID: PMC5761812 DOI: 10.1104/pp.17.01050] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 10/09/2017] [Indexed: 05/19/2023]
Abstract
Recent advances highlight understanding of the diversity of peroxisome contributions to plant biology and the mechanisms through which these essential organelles are generated.
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Affiliation(s)
- Yun-Ting Kao
- Department of Biosciences, Rice University, Houston, Texas 77005
| | - Kim L Gonzalez
- Department of Biosciences, Rice University, Houston, Texas 77005
| | - Bonnie Bartel
- Department of Biosciences, Rice University, Houston, Texas 77005
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7
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Lyman KA, Han Y, Heuermann RJ, Cheng X, Kurz JE, Lyman RE, Van Veldhoven PP, Chetkovich DM. Allostery between two binding sites in the ion channel subunit TRIP8b confers binding specificity to HCN channels. J Biol Chem 2017; 292:17718-17730. [PMID: 28887304 DOI: 10.1074/jbc.m117.802256] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 09/05/2017] [Indexed: 12/20/2022] Open
Abstract
Tetratricopeptide repeat (TPR) domains are ubiquitous structural motifs that mediate protein-protein interactions. For example, the TPR domains in the peroxisomal import receptor PEX5 enable binding to a range of type 1 peroxisomal targeting signal motifs. A homolog of PEX5, tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b), binds to and functions as an auxiliary subunit of hyperpolarization-activated cyclic nucleotide (HCN)-gated channels. Given the similarity between TRIP8b and PEX5, this difference in function raises the question of what mechanism accounts for their binding specificity. In this report, we found that the cyclic nucleotide-binding domain and the C terminus of the HCN channel are critical for conferring specificity to TRIP8b binding. We show that TRIP8b binds the HCN cyclic nucleotide-binding domain through a 37-residue domain and the HCN C terminus through the TPR domains. Using a combination of fluorescence polarization- and co-immunoprecipitation-based assays, we establish that binding at either site increases affinity at the other. Thus, allosteric coupling of the TRIP8b TPR domains both promotes binding to HCN channels and limits binding to type 1 peroxisomal targeting signal substrates. These results raise the possibility that other TPR domains may be similarly influenced by allosteric mechanisms as a general feature of protein-protein interactions.
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Affiliation(s)
- Kyle A Lyman
- From the Davee Department of Neurology and Clinical Neurosciences and
| | - Ye Han
- From the Davee Department of Neurology and Clinical Neurosciences and
| | | | - Xiangying Cheng
- From the Davee Department of Neurology and Clinical Neurosciences and
| | | | - Reagan E Lyman
- From the Davee Department of Neurology and Clinical Neurosciences and
| | - Paul P Van Veldhoven
- the Laboratory of Lipid Biochemistry and Protein Interactions, Campus Gasthuisberg, KU Leuven, 3000 Leuven, Belgium
| | - Dane M Chetkovich
- From the Davee Department of Neurology and Clinical Neurosciences and .,Physiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611 and
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8
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Cross LL, Paudyal R, Kamisugi Y, Berry A, Cuming AC, Baker A, Warriner SL. Towards designer organelles by subverting the peroxisomal import pathway. Nat Commun 2017; 8:454. [PMID: 28878206 DOI: 10.1038/s41467-017-00487-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 07/03/2017] [Indexed: 01/09/2023] Open
Abstract
The development of ‘designer’ organelles could be a key strategy to enable foreign pathways to be efficiently controlled within eukaryotic biotechnology. A fundamental component of any such system will be the implementation of a bespoke protein import pathway that can selectively deliver constituent proteins to the new compartment in the presence of existing endogenous trafficking systems. Here we show that the protein–protein interactions that control the peroxisomal protein import pathway can be manipulated to create a pair of interacting partners that still support protein import in moss cells, but are orthogonal to the naturally occurring pathways. In addition to providing a valuable experimental tool to give new insights into peroxisomal protein import, the variant receptor-signal sequence pair forms the basis of a system in which normal peroxisomal function is downregulated and replaced with an alternative pathway, an essential first step in the creation of a designer organelle. Designer organelles could allow the isolation of synthetic biological pathways from endogenous components of the host cell. Here the authors engineer a peroxisomal protein import pathway orthogonal to the naturally occurring system.
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9
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Abstract
Peroxisomal matrix proteins are synthesized on cytosolic ribosomes and rapidly transported into the organelle by a complex machinery. The data gathered in recent years suggest that this machinery operates through a syringe-like mechanism, in which the shuttling receptor PEX5 - the "plunger" - pushes a newly synthesized protein all the way through a peroxisomal transmembrane protein complex - the "barrel" - into the matrix of the organelle. Notably, insertion of cargo-loaded receptor into the "barrel" is an ATP-independent process, whereas extraction of the receptor back into the cytosol requires its monoubiquitination and the action of ATP-dependent mechanoenzymes. Here, we review the main data behind this model.
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Affiliation(s)
- Tânia Francisco
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Tony A Rodrigues
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | - Ana F Dias
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | - Aurora Barros-Barbosa
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Diana Bicho
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Jorge E Azevedo
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
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10
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Reumann S, Bartel B. Plant peroxisomes: recent discoveries in functional complexity, organelle homeostasis, and morphological dynamics. Curr Opin Plant Biol 2016; 34:17-26. [PMID: 27500947 PMCID: PMC5161562 DOI: 10.1016/j.pbi.2016.07.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 07/15/2016] [Accepted: 07/20/2016] [Indexed: 05/20/2023]
Abstract
Peroxisomes are essential for life in plants. These organelles house a variety of metabolic processes that generate and inactivate reactive oxygen species. Our knowledge of pathways and mechanisms that depend on peroxisomes and their constituent enzymes continues to grow, and in this review we highlight recent advances in understanding the identity and biological functions of peroxisomal enzymes and metabolic processes. We also review how peroxisomal matrix and membrane proteins enter the organelle from their sites of synthesis. Peroxisome homeostasis is regulated by specific degradation mechanisms, and we discuss the contributions of specialized autophagy and a peroxisomal protease to the degradation of entire peroxisomes and peroxisomal enzymes that are damaged or superfluous. Finally, we review how peroxisomes can flexibly change their morphology to facilitate inter-organellar contacts.
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Affiliation(s)
- Sigrun Reumann
- Department of Plant Biochemistry and Infection Biology, Biocentre Klein Flottbek, University of Hamburg, D-22609 Hamburg, Germany; Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway
| | - Bonnie Bartel
- Department of BioSciences, Rice University, Houston, TX 77005, USA.
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11
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Abstract
The import of proteins into peroxisomes possesses many unusual features such as the ability to import folded proteins, and a surprising diversity of targeting signals with differing affinities that can be recognized by the same receptor. As understanding of the structure and function of many components of the protein import machinery has grown, an increasingly complex network of factors affecting each step of the import pathway has emerged. Structural studies have revealed the presence of additional interactions between cargo proteins and the PEX5 receptor that affect import potential, with a subtle network of cargo-induced conformational changes in PEX5 being involved in the import process. Biochemical studies have also indicated an interdependence of receptor-cargo import with release of unloaded receptor from the peroxisome. Here, we provide an update on recent literature concerning mechanisms of protein import into peroxisomes.
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Affiliation(s)
- Alison Baker
- School of Molecular and Cellular Biology, Astbury Centre for Structural Molecular Biology and Centre for Plant Sciences, University of Leeds, Leeds LS2 9JT, U.K.
| | - Thomas Lanyon-Hogg
- Institute of Chemical Biology, Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Stuart L Warriner
- School of Chemistry, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K
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12
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Cross LL, Ebeed HT, Baker A. Peroxisome biogenesis, protein targeting mechanisms and PEX gene functions in plants. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2016; 1863:850-62. [DOI: 10.1016/j.bbamcr.2015.09.027] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/15/2015] [Accepted: 09/21/2015] [Indexed: 12/16/2022]
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13
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Bhogal MS, Lanyon-Hogg T, Johnston KA, Warriner SL, Baker A. Covalent Label Transfer between Peroxisomal Importomer Components Reveals Export-driven Import Interactions. J Biol Chem 2015; 291:2460-8. [PMID: 26567336 PMCID: PMC4732227 DOI: 10.1074/jbc.m115.686501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Indexed: 11/06/2022] Open
Abstract
Peroxisomes are vital metabolic organelles found in almost all eukaryotic organisms, and they rely exclusively on import of their matrix protein content from the cytosol. In vitro import of proteins into isolated peroxisomal fractions has provided a wealth of knowledge on the import process. However, the common method of protease protection garnered no information on the import of an N-terminally truncated PEX5 (PEX5C) receptor construct or peroxisomal malate dehydrogenase 1 (pMDH1) cargo protein into sunflower peroxisomes because of high degrees of protease susceptibility or resistance, respectively. Here we present a means for analysis of in vitro import through a covalent biotin label transfer and employ this method to the import of PEX5C. Label transfer demonstrates that the PEX5C construct is monomeric under the conditions of the import assay. This technique was capable of identifying the PEX5-PEX14 interaction as the first interaction of the import process through competition experiments. Labeling of the peroxisomal protein import machinery by PEX5C demonstrated that this interaction was independent of added cargo protein, and, strikingly, the interaction between PEX5C and the import machinery was shown to be ATP-dependent. These important mechanistic insights highlight the power of label transfer in studying interactions, rather than proteins, of interest and demonstrate that this technique should be applied to future studies of peroxisomal in vitro import.
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Affiliation(s)
- Moninder S Bhogal
- From the Centre for Plant Sciences and School of Molecular and Cellular Biology and
| | - Thomas Lanyon-Hogg
- From the Centre for Plant Sciences and School of Molecular and Cellular Biology and School of Chemistry and Astbury Centre, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Katherine A Johnston
- From the Centre for Plant Sciences and School of Molecular and Cellular Biology and
| | - Stuart L Warriner
- School of Chemistry and Astbury Centre, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Alison Baker
- From the Centre for Plant Sciences and School of Molecular and Cellular Biology and
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14
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Kao YT, Bartel B. Elevated growth temperature decreases levels of the PEX5 peroxisome-targeting signal receptor and ameliorates defects of Arabidopsis mutants with an impaired PEX4 ubiquitin-conjugating enzyme. BMC Plant Biol 2015; 15:224. [PMID: 26377801 PMCID: PMC4574000 DOI: 10.1186/s12870-015-0605-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 09/06/2015] [Indexed: 05/29/2023]
Abstract
BACKGROUND Peroxisomes house critical metabolic reactions. For example, fatty acid β-oxidation enzymes, which are essential during early seedling development, are peroxisomal. Peroxins (PEX proteins) are needed to bring proteins into peroxisomes. Most matrix proteins are delivered to peroxisomes by PEX5, a receptor that forms transient pores to escort proteins across the peroxisomal membrane. After cargo delivery, a peroxisome-tethered ubiquitin-conjugating enzyme (PEX4) and peroxisomal ubiquitin-protein ligases mono- or polyubiquitinate PEX5 for recycling back to the cytosol or for degradation, respectively. Arabidopsis pex mutants β-oxidize fatty acids inefficiently and therefore fail to germinate or grow less vigorously. These defects can be partially alleviated by providing a fixed carbon source, such as sucrose, in the growth medium. Despite extensive characterization of peroxisome biogenesis in Arabidopsis grown in non-challenged conditions, the effects of environmental stressors on peroxisome function and pex mutant dysfunction are largely unexplored. RESULTS We surveyed the impact of growth temperature on a panel of pex mutants and found that elevated temperature ameliorated dependence on external sucrose and reduced PEX5 levels in the pex4-1 mutant. Conversely, growth at low temperature exacerbated pex4-1 physiological defects and increased PEX5 levels. Overexpressing PEX5 also worsened pex4-1 defects, implying that PEX5 lingering on the peroxisomal membrane when recycling is impaired impedes peroxisome function. Growth at elevated temperature did not reduce the fraction of membrane-associated PEX5 in pex4-1, suggesting that elevated temperature did not restore PEX4 enzymatic function in the mutant. Moreover, preventing autophagy in pex4-1 did not restore PEX5 levels at high temperature. In contrast, MG132 treatment increased PEX5 levels, implicating the proteasome in degrading PEX5, especially at high temperature. CONCLUSIONS We conclude that growth at elevated temperature increases proteasomal degradation of PEX5 to reduce overall PEX5 levels and ameliorate pex4-1 physiological defects. Our results support the hypothesis that efficient retrotranslocation of PEX5 after cargo delivery is needed not only to make PEX5 available for further rounds of cargo delivery, but also to prevent the peroxisome dysfunction that results from PEX5 lingering in the peroxisomal membrane.
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Affiliation(s)
- Yun-Ting Kao
- Biochemistry and Cell Biology Program, Department of BioSciences, Rice University, Houston, TX, USA.
| | - Bonnie Bartel
- Biochemistry and Cell Biology Program, Department of BioSciences, Rice University, Houston, TX, USA.
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15
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Rodrigues TA, Grou CP, Azevedo JE. Revisiting the intraperoxisomal pathway of mammalian PEX7. Sci Rep 2015; 5:11806. [PMID: 26138649 DOI: 10.1038/srep11806] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 06/08/2015] [Indexed: 02/07/2023] Open
Abstract
Newly synthesized peroxisomal proteins containing a cleavable type 2 targeting signal (PTS2) are transported to the peroxisome by a cytosolic PEX5-PEX7 complex. There, the trimeric complex becomes inserted into the peroxisomal membrane docking/translocation machinery (DTM), a step that leads to the translocation of the cargo into the organelle matrix. Previous work suggests that PEX5 is retained at the DTM during all the steps occurring at the peroxisome but whether the same applies to PEX7 was unknown. By subjecting different pre-assembled trimeric PEX5-PEX7-PTS2 complexes to in vitro co-import/export assays we found that the export competence of peroxisomal PEX7 is largely determined by the PEX5 molecule that transported it to the peroxisome. This finding suggests that PEX7 is also retained at the DTM during the peroxisomal steps and implies that cargo proteins are released into the organelle matrix by DTM-embedded PEX7. The release step does not depend on PTS2 cleavage. Rather, our data suggest that insertion of the trimeric PEX5-PEX7-PTS2 protein complex into the DTM is probably accompanied by conformational alterations in PEX5 to allow release of the PTS2 protein into the organelle matrix.
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16
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Abstract
Peroxisomes are unique among the organelles of the endomembrane system. Unlike other organelles that derive most if not all of their proteins from the ER (endoplasmic reticulum), peroxisomes contain dedicated machineries for import of matrix proteins and insertion of membrane proteins. However, peroxisomes are also able to import a subset of their membrane proteins from the ER. One aspect of peroxisome biology that has remained ill defined is the role the various import pathways play in peroxisome maintenance. In this review, we discuss the available data on matrix and membrane protein import into peroxisomes. Peroxisomal membrane and matrix proteins require distinct factors for their transport. Matrix proteins fold in the cytosol prior to their import. Loaded targeting receptors form part of the matrix protein translocation pore. Many membrane proteins are directly inserted into the peroxisomal membrane. Some peroxisomal membrane proteins are transported via the ER to peroxisomes.
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Affiliation(s)
- P K Kim
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - E H Hettema
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, South Yorkshire S10 2TN, United Kingdom.
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Skoulding NS, Chowdhary G, Deus MJ, Baker A, Reumann S, Warriner SL. Experimental validation of plant peroxisomal targeting prediction algorithms by systematic comparison of in vivo import efficiency and in vitro PTS1 binding affinity. J Mol Biol 2014; 427:1085-101. [PMID: 25498386 DOI: 10.1016/j.jmb.2014.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/30/2014] [Accepted: 12/04/2014] [Indexed: 01/19/2023]
Abstract
Most peroxisomal matrix proteins possess a C-terminal targeting signal type 1 (PTS1). Accurate prediction of functional PTS1 sequences and their relative strength by computational methods is essential for determination of peroxisomal proteomes in silico but has proved challenging due to high levels of sequence variability of non-canonical targeting signals, particularly in higher plants, and low levels of availability of experimentally validated non-canonical examples. In this study, in silico predictions were compared with in vivo targeting analyses and in vitro thermodynamic binding of mutated variants within the context of one model targeting sequence. There was broad agreement between the methods for entire PTS1 domains and position-specific single amino acid residues, including residues upstream of the PTS1 tripeptide. The hierarchy Leu>Met>Ile>Val at the C-terminal position was determined for all methods but both experimental approaches suggest that Tyr is underweighted in the prediction algorithm due to the absence of this residue in the positive training dataset. A combination of methods better defines the score range that discriminates a functional PTS1. In vitro binding to the PEX5 receptor could discriminate among strong targeting signals while in vivo targeting assays were more sensitive, allowing detection of weak functional import signals that were below the limit of detection in the binding assay. Together, the data provide a comprehensive assessment of the factors driving PTS1 efficacy and provide a framework for the more quantitative assessment of the protein import pathway in higher plants.
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Affiliation(s)
- Nicola S Skoulding
- School of Chemistry and the Astbury Centre, University of Leeds, Leeds LS2 9JT, UK
| | - Gopal Chowdhary
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Richard Johansens Gate 4, N-4021 Stavanger, Norway; KIIT School of Biotechnology, Campus XI, KIIT University, I-751024 Bhubaneswar, India
| | - Mara J Deus
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Richard Johansens Gate 4, N-4021 Stavanger, Norway
| | - Alison Baker
- Centre for Plant Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Sigrun Reumann
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Richard Johansens Gate 4, N-4021 Stavanger, Norway; Department of Biology, Biocentre Klein Flottbek, University of Hamburg, D-22609 Hamburg, Germany
| | - Stuart L Warriner
- School of Chemistry and the Astbury Centre, University of Leeds, Leeds LS2 9JT, UK.
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Baker A, Paudyal R. The life of the peroxisome: from birth to death. Curr Opin Plant Biol 2014; 22:39-47. [PMID: 25261594 DOI: 10.1016/j.pbi.2014.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 07/24/2014] [Accepted: 09/05/2014] [Indexed: 06/03/2023]
Abstract
Peroxisomes are dynamic and metabolically plastic organelles. Their multiplicity of functions impacts on many aspects of plant development and survival. New functions for plant peroxisomes such as in the synthesis of biotin, ubiquinone and phylloquinone are being uncovered and their role in generating reactive oxygen species (ROS) and reactive nitrogen species (RNS) as signalling hubs in defence and development is becoming appreciated. Understanding of the biogenesis of peroxisomes, mechanisms of import and turnover of their protein complement, and the wholesale destruction of the organelle by specific autophagic processes is giving new insight into the ways that plants can adjust peroxisome function in response to changing needs.
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Affiliation(s)
- Alison Baker
- Centre for Plant Sciences, School of Biology, University of Leeds, Leeds LS2 9JT, UK.
| | - Rupesh Paudyal
- Centre for Plant Sciences, School of Biology, University of Leeds, Leeds LS2 9JT, UK
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