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Llamas E, Koyuncu S, Lee HJ, Wehrmann M, Gutierrez-Garcia R, Dunken N, Charura N, Torres-Montilla S, Schlimgen E, Mandel AM, Theile EB, Grossbach J, Wagle P, Lackmann JW, Schermer B, Benzing T, Beyer A, Pulido P, Rodriguez-Concepcion M, Zuccaro A, Vilchez D. In planta expression of human polyQ-expanded huntingtin fragment reveals mechanisms to prevent disease-related protein aggregation. NATURE AGING 2023; 3:1345-1357. [PMID: 37783816 PMCID: PMC10645592 DOI: 10.1038/s43587-023-00502-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 09/01/2023] [Indexed: 10/04/2023]
Abstract
In humans, aggregation of polyglutamine repeat (polyQ) proteins causes disorders such as Huntington's disease. Although plants express hundreds of polyQ-containing proteins, no pathologies arising from polyQ aggregation have been reported. To investigate this phenomenon, we expressed an aggregation-prone fragment of human huntingtin (HTT) with an expanded polyQ stretch (Q69) in Arabidopsis thaliana plants. In contrast to animal models, we find that Arabidopsis sp. suppresses Q69 aggregation through chloroplast proteostasis. Inhibition of chloroplast proteostasis diminishes the capacity of plants to prevent cytosolic Q69 aggregation. Moreover, endogenous polyQ-containing proteins also aggregate on chloroplast dysfunction. We find that Q69 interacts with the chloroplast stromal processing peptidase (SPP). Synthetic Arabidopsis SPP prevents polyQ-expanded HTT aggregation in human cells. Likewise, ectopic SPP expression in Caenorhabditis elegans reduces neuronal Q67 aggregation and subsequent neurotoxicity. Our findings suggest that synthetic plant proteins, such as SPP, hold therapeutic potential for polyQ disorders and other age-related diseases involving protein aggregation.
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Affiliation(s)
- Ernesto Llamas
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Cluster of Excellence on Plant Sciences, Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | - Seda Koyuncu
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany
| | - Hyun Ju Lee
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany
| | - Markus Wehrmann
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany
| | - Ricardo Gutierrez-Garcia
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany
| | - Nick Dunken
- Cluster of Excellence on Plant Sciences, Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | - Nyasha Charura
- Cluster of Excellence on Plant Sciences, Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | | | - Elena Schlimgen
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany
| | - Amrei M Mandel
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University Hospital Cologne, Cologne, Germany
| | - Erik Boelen Theile
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Jan Grossbach
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Prerana Wagle
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Jan-Wilm Lackmann
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Bernhard Schermer
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University Hospital Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University Hospital Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Andreas Beyer
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
- Institute for Genetics, University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Pablo Pulido
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnologia, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | | | - Alga Zuccaro
- Cluster of Excellence on Plant Sciences, Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | - David Vilchez
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany.
- Institute for Integrated Stress Response Signaling, Faculty of Medicine, University Hospital Cologne, Cologne, Germany.
- Institute for Genetics, University of Cologne, Cologne, Germany.
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.
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Sidorczuk K, Mackiewicz P, Pietluch F, Gagat P. Characterization of signal and transit peptides based on motif composition and taxon-specific patterns. Sci Rep 2023; 13:15751. [PMID: 37735485 PMCID: PMC10514287 DOI: 10.1038/s41598-023-42987-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/17/2023] [Indexed: 09/23/2023] Open
Abstract
Targeting peptides or presequences are N-terminal extensions of proteins that encode information about their cellular localization. They include signal peptides (SP), which target proteins to the endoplasmic reticulum, and transit peptides (TP) directing proteins to the organelles of endosymbiotic origin: chloroplasts and mitochondria. TPs were hypothesized to have evolved from antimicrobial peptides (AMPs), which are responsible for the host defence against microorganisms, including bacteria, fungi and viruses. In this study, we performed comprehensive bioinformatic analyses of amino acid motifs of targeting peptides and AMPs using a curated set of experimentally verified proteins. We identified motifs frequently occurring in each type of presequence showing specific patterns associated with their amino acid composition, and investigated their position within the presequence. We also compared motif patterns among different taxonomic groups and identified taxon-specific features, providing some evolutionary insights. Considering the functional relevance and many practical applications of targeting peptides and AMPs, we believe that our analyses will prove useful for their design, and better understanding of protein import mechanism and presequence evolution.
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Affiliation(s)
- Katarzyna Sidorczuk
- Department of Bioinformatics and Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Paweł Mackiewicz
- Department of Bioinformatics and Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Filip Pietluch
- Department of Bioinformatics and Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Przemysław Gagat
- Department of Bioinformatics and Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland.
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3
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Nellaepalli S, Lau AS, Jarvis RP. Chloroplast protein translocation pathways and ubiquitin-dependent regulation at a glance. J Cell Sci 2023; 136:jcs241125. [PMID: 37732520 PMCID: PMC10546890 DOI: 10.1242/jcs.241125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023] Open
Abstract
Chloroplasts conduct photosynthesis and numerous metabolic and signalling processes that enable plant growth and development. Most of the ∼3000 proteins in chloroplasts are nucleus encoded and must be imported from the cytosol. Thus, the protein import machinery of the organelle (the TOC-TIC apparatus) is of fundamental importance for chloroplast biogenesis and operation. Cytosolic factors target chloroplast precursor proteins to the TOC-TIC apparatus, which drives protein import across the envelope membranes into the organelle, before various internal systems mediate downstream routing to different suborganellar compartments. The protein import system is proteolytically regulated by the ubiquitin-proteasome system (UPS), enabling centralized control over the organellar proteome. In addition, the UPS targets a range of chloroplast proteins directly. In this Cell Science at a Glance article and the accompanying poster, we present mechanistic details of these different chloroplast protein targeting and translocation events, and of the UPS systems that regulate chloroplast proteins.
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Affiliation(s)
- Sreedhar Nellaepalli
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Anne Sophie Lau
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
- Department of Plant Physiology, Faculty of Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R. Paul Jarvis
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
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4
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Ballabani G, Forough M, Kessler F, Shanmugabalaji V. The journey of preproteins across the chloroplast membrane systems. Front Physiol 2023; 14:1213866. [PMID: 37324391 PMCID: PMC10267391 DOI: 10.3389/fphys.2023.1213866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
The photosynthetic capacity of chloroplasts is vital for autotrophic growth in algae and plants. The origin of the chloroplast has been explained by the endosymbiotic theory that proposes the engulfment of a cyanobacterium by an ancestral eukaryotic cell followed by the transfer of many cyanobacterial genes to the host nucleus. As a result of the gene transfer, the now nuclear-encoded proteins acquired chloroplast targeting peptides (known as transit peptides; transit peptide) and are translated as preproteins in the cytosol. Transit peptides contain specific motifs and domains initially recognized by cytosolic factors followed by the chloroplast import components at the outer and inner envelope of the chloroplast membrane. Once the preprotein emerges on the stromal side of the chloroplast protein import machinery, the transit peptide is cleaved by stromal processing peptidase. In the case of thylakoid-localized proteins, cleavage of the transit peptides may expose a second targeting signal guiding the protein to the thylakoid lumen or allow insertion into the thylakoid membrane by internal sequence information. This review summarizes the common features of targeting sequences and describes their role in routing preproteins to and across the chloroplast envelope as well as the thylakoid membrane and lumen.
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Affiliation(s)
| | | | - Felix Kessler
- *Correspondence: Felix Kessler, ; Venkatasalam Shanmugabalaji,
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5
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Caspari OD, Garrido C, Law CO, Choquet Y, Wollman FA, Lafontaine I. Converting antimicrobial into targeting peptides reveals key features governing protein import into mitochondria and chloroplasts. PLANT COMMUNICATIONS 2023:100555. [PMID: 36733255 PMCID: PMC10363480 DOI: 10.1016/j.xplc.2023.100555] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/18/2023] [Accepted: 01/26/2023] [Indexed: 06/18/2023]
Abstract
We asked what peptide features govern targeting to the mitochondria versus the chloroplast, using antimicrobial peptides as a starting point. This approach was inspired by the endosymbiotic hypothesis that organelle-targeting peptides derive from antimicrobial amphipathic peptides delivered by the host cell, to which organelle progenitors became resistant. To explore the molecular changes required to convert antimicrobial into targeting peptides, we expressed a set of 13 antimicrobial peptides in Chlamydomonas reinhardtii. Peptides were systematically modified to test distinctive features of mitochondrion- and chloroplast-targeting peptides, and we assessed their targeting potential by following the intracellular localization and maturation of a Venus fluorescent reporter used as a cargo protein. Mitochondrial targeting can be achieved by some unmodified antimicrobial peptide sequences. Targeting to both organelles is improved by replacing lysines with arginines. Chloroplast targeting is enabled by the presence of flanking unstructured sequences, additional constraints consistent with chloroplast endosymbiosis having occurred in a cell that already contained mitochondria. If indeed targeting peptides evolved from antimicrobial peptides, then required modifications imply a temporal evolutionary scenario with an early exchange of cationic residues and a late acquisition of chloroplast-specific motifs.
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Affiliation(s)
- Oliver D Caspari
- UMR7141 (CNRS/Sorbonne Université), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France.
| | - Clotilde Garrido
- UMR7141 (CNRS/Sorbonne Université), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Chris O Law
- Centre for Microscopy and Cellular Imaging, Biology Department Loyola Campus of Concordia University, 7141 Sherbrooke W., Montréal, QC H4B 1R6, Canada
| | - Yves Choquet
- UMR7141 (CNRS/Sorbonne Université), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Francis-André Wollman
- UMR7141 (CNRS/Sorbonne Université), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Ingrid Lafontaine
- UMR7141 (CNRS/Sorbonne Université), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France.
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6
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Kim DB, Na C, Hwang I, Lee DW. Understanding protein translocation across chloroplast membranes: Translocons and motor proteins. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2023; 65:408-416. [PMID: 36223071 DOI: 10.1111/jipb.13385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Subcellular organelles in eukaryotes are surrounded by lipid membranes. In an endomembrane system, vesicle trafficking is the primary mechanism for the delivery of organellar proteins to specific organelles. However, organellar proteins for chloroplasts, mitochondria, the nucleus, and peroxisomes that are translated in the cytosol are directly imported into their target organelles. Chloroplasts are a plant-specific organelle with outer and inner envelope membranes, a dual-membrane structure that is similar to mitochondria. Interior chloroplast proteins translated by cytosolic ribosomes are thus translocated through TOC and TIC complexes (translocons in the outer and inner envelope of chloroplasts, respectively), with stromal ATPase motor proteins playing a critical role in pulling pre-proteins through these import channels. Over the last three decades, the identity and function of TOC/TIC components and stromal motor proteins have been actively investigated, which has shed light on the action mechanisms at a molecular level. However, there remains some disagreement over the exact composition of TIC complexes and genuine stromal motor proteins. In this review, we discuss recent findings on the mechanisms by which proteins are translocated through TOC/TIC complexes and discuss future prospects for this field of research.
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Affiliation(s)
- Da Been Kim
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
| | - Changhee Na
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Dong Wook Lee
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea
- Kumho Life Science Laboratory, Chonnam National University, Gwangju, 61186, Korea
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7
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Gan SS. Hypothesis: the subcellular senescence sequence of a mesophyll cell mirrors the cell origin and evolution. MOLECULAR HORTICULTURE 2022; 2:27. [PMID: 37789411 PMCID: PMC10515013 DOI: 10.1186/s43897-022-00048-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Affiliation(s)
- Su-Sheng Gan
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA.
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8
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Rozov SM, Deineko EV. Increasing the Efficiency of the Accumulation of Recombinant Proteins in Plant Cells: The Role of Transport Signal Peptides. PLANTS (BASEL, SWITZERLAND) 2022; 11:2561. [PMID: 36235427 PMCID: PMC9572730 DOI: 10.3390/plants11192561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
The problem with increasing the yield of recombinant proteins is resolvable using different approaches, including the transport of a target protein to cell compartments with a low protease activity. In the cell, protein targeting involves short-signal peptide sequences recognized by intracellular protein transport systems. The main systems of the protein transport across membranes of the endoplasmic reticulum and endosymbiotic organelles are reviewed here, as are the major types and structure of the signal sequences targeting proteins to the endoplasmic reticulum and its derivatives, to plastids, and to mitochondria. The role of protein targeting to certain cell organelles depending on specific features of recombinant proteins and the effect of this targeting on the protein yield are discussed, in addition to the main directions of the search for signal sequences based on their primary structure. This knowledge makes it possible not only to predict a protein localization in the cell but also to reveal the most efficient sequences with potential biotechnological utility.
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Jeong J, Moon B, Hwang I, Lee DW. GREEN FLUORESCENT PROTEIN variants with enhanced folding are more efficiently imported into chloroplasts. PLANT PHYSIOLOGY 2022; 190:238-249. [PMID: 35699510 PMCID: PMC9434181 DOI: 10.1093/plphys/kiac291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/05/2022] [Indexed: 06/15/2023]
Abstract
Chloroplasts and mitochondria are subcellular organelles that evolved from cyanobacteria and α-proteobacteria, respectively. Although they have their own genomes, the majority of their proteins are encoded by nuclear genes, translated by cytosolic ribosomes, and imported via outer and inner membrane translocon complexes. The unfolding of mature regions of proteins is thought to be a prerequisite for the import of the proteins into these organelles. However, it is not fully understood how protein folding properties affect their import into these organelles. In this study, we examined the import behavior of chloroplast and mitochondrial reporters with normal green fluorescent protein (GFP) and two GFP variants with enhanced folding propensity, superfolder GFP (sfGFP) and extra-superfolder GFP (esGFP), which is folded better than sfGFP. sfGFP and esGFP were less dependent on the sequence motifs of the transit peptide (TP) and import machinery during protein import into Arabidopsis (Arabidopsis thaliana) chloroplasts, compared with normal GFP. sfGFP and esGFP were efficiently imported into chloroplasts by a mutant TP with an alanine substitution in the N-terminal MLM motif, whereas the same mutant TP showed a defect in importing normal GFP into chloroplasts. Moreover, sfGFP and esGFP were efficiently imported into plastid protein import 2 (ppi2) and heat shock protein 93-V (hsp93-V) plants, which have mutations in atToc159 and Hsp93-V, respectively. In contrast, the presequence-mediated mitochondrial import of sfGFP and esGFP was severely impaired. Based on these results, we propose that the chloroplast import machinery is more tolerant to different folding states of preproteins, whereas the mitochondrial machinery is more specialized in the translocation of unfolded preproteins.
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Affiliation(s)
- Jinseung Jeong
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, South Korea
| | - Byeongho Moon
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, South Korea
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The Effects of Physical Activity on the Gut Microbiota and the Gut–Brain Axis in Preclinical and Human Models: A Narrative Review. Nutrients 2022; 14:nu14163293. [PMID: 36014798 PMCID: PMC9413457 DOI: 10.3390/nu14163293] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 08/10/2022] [Accepted: 08/10/2022] [Indexed: 11/17/2022] Open
Abstract
Increasing evidence supports the importance of the gut microbiota (GM) in regulating multiple functions related to host physical health and, more recently, through the gut–brain axis (GBA), mental health. Similarly, the literature on the impact of physical activity (PA), including exercise, on GM and GBA is growing. Therefore, this narrative review summarizes and critically appraises the existing literature that delves into the benefits or adverse effects produced by PA on physical and mental health status through modifications of the GM, highlighting differences and similarities between preclinical and human studies. The same exercise in animal models, whether performed voluntarily or forced, has different effects on the GM, just as, in humans, intense endurance exercise can have a negative influence. In humans and animals, only aerobic PA seems able to modify the composition of the GM, whereas cardiovascular fitness appears related to specific microbial taxa or metabolites that promote a state of physical health. The PA favors bacterial strains that can promote physical performance and that can induce beneficial changes in the brain. Currently, it seems useful to prioritize aerobic activities at a moderate and not prolonged intensity. There may be greater benefits if PA is undertaken from a young age and the effects on the GM seem to gradually disappear when the activity is stopped. The PA produces modifications in the GM that can mediate and induce mental health benefits.
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Zheng C, Xu X, Zhang L, Lu D. Liquid-Liquid Phase Separation Phenomenon on Protein Sorting Within Chloroplasts. Front Physiol 2022; 12:801212. [PMID: 35002776 PMCID: PMC8740050 DOI: 10.3389/fphys.2021.801212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 12/09/2021] [Indexed: 12/13/2022] Open
Abstract
In higher plants, chloroplasts are vital organelles possessing highly complex compartmentalization. As most chloroplast-located proteins are encoded in the nucleus and synthesized in the cytosol, the correct sorting of these proteins to appropriate compartments is critical for the proper functions of chloroplasts as well as plant survival. Nuclear-encoded chloroplast proteins are imported into stroma and further sorted to distinct compartments via different pathways. The proteins predicted to be sorted to the thylakoid lumen by the chloroplast twin arginine transport (cpTAT) pathway are shown to be facilitated by STT1/2 driven liquid-liquid phase separation (LLPS). Liquid-liquid phase separation is a novel mechanism to facilitate the formation of membrane-less sub-cellular compartments and accelerate biochemical reactions temporally and spatially. In this review, we introduce the sorting mechanisms within chloroplasts, and briefly summarize the properties and significance of LLPS, with an emphasis on the novel function of LLPS in the sorting of cpTAT substrate proteins. We conclude with perspectives for the future research on chloroplast protein sorting and targeting mechanisms.
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Affiliation(s)
- Canhui Zheng
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Xiumei Xu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Lixin Zhang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Dandan Lu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
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12
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Heidorn-Czarna M, Maziak A, Janska H. Protein Processing in Plant Mitochondria Compared to Yeast and Mammals. FRONTIERS IN PLANT SCIENCE 2022; 13:824080. [PMID: 35185991 PMCID: PMC8847149 DOI: 10.3389/fpls.2022.824080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/12/2022] [Indexed: 05/02/2023]
Abstract
Limited proteolysis, called protein processing, is an essential post-translational mechanism that controls protein localization, activity, and in consequence, function. This process is prevalent for mitochondrial proteins, mainly synthesized as precursor proteins with N-terminal sequences (presequences) that act as targeting signals and are removed upon import into the organelle. Mitochondria have a distinct and highly conserved proteolytic system that includes proteases with sole function in presequence processing and proteases, which show diverse mitochondrial functions with limited proteolysis as an additional one. In virtually all mitochondria, the primary processing of N-terminal signals is catalyzed by the well-characterized mitochondrial processing peptidase (MPP). Subsequently, a second proteolytic cleavage occurs, leading to more stabilized residues at the newly formed N-terminus. Lately, mitochondrial proteases, intermediate cleavage peptidase 55 (ICP55) and octapeptidyl protease 1 (OCT1), involved in proteolytic cleavage after MPP and their substrates have been described in the plant, yeast, and mammalian mitochondria. Mitochondrial proteins can also be processed by removing a peptide from their N- or C-terminus as a maturation step during insertion into the membrane or as a regulatory mechanism in maintaining their function. This type of limited proteolysis is characteristic for processing proteases, such as IMP and rhomboid proteases, or the general mitochondrial quality control proteases ATP23, m-AAA, i-AAA, and OMA1. Identification of processing protease substrates and defining their consensus cleavage motifs is now possible with the help of large-scale quantitative mass spectrometry-based N-terminomics, such as combined fractional diagonal chromatography (COFRADIC), charge-based fractional diagonal chromatography (ChaFRADIC), or terminal amine isotopic labeling of substrates (TAILS). This review summarizes the current knowledge on the characterization of mitochondrial processing peptidases and selected N-terminomics techniques used to uncover protease substrates in the plant, yeast, and mammalian mitochondria.
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Jeong J, Hwang I, Lee DW. Functional Organization of Sequence Motifs in Diverse Transit Peptides of Chloroplast Proteins. Front Physiol 2021; 12:795156. [PMID: 34880786 PMCID: PMC8645953 DOI: 10.3389/fphys.2021.795156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 10/28/2021] [Indexed: 11/17/2022] Open
Abstract
Although the chloroplasts in plants are characterized by an inherent genome, the chloroplast proteome is composed of proteins encoded by not only the chloroplast genome but also the nuclear genome. Nuclear-encoded chloroplast proteins are synthesized on cytosolic ribosomes and post-translationally targeted to the chloroplasts. In the latter process, an N-terminal cleavable transit peptide serves as a targeting signal required for the import of nuclear-encoded chloroplast interior proteins. This import process is mediated via an interaction between the sequence motifs in transit peptides and the components of the TOC/TIC (translocon at the outer/inner envelope of chloroplasts) translocons. Despite a considerable diversity in primary structures, several common features have been identified among transit peptides, including N-terminal moderate hydrophobicity, multiple proline residues dispersed throughout the transit peptide, preferential usage of basic residues over acidic residues, and an absence of N-terminal arginine residues. In this review, we will recapitulate and discuss recent progress in our current understanding of the functional organization of sequence elements commonly present in diverse transit peptides, which are essential for the multi-step import of chloroplast proteins.
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Affiliation(s)
- Jinseung Jeong
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, South Korea
| | - Dong Wook Lee
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea.,Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, South Korea
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