1
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Xu S, Li X, Geng J, Cao Y, Yu Y, Qi L. Sec61γ is a vital protein in the endoplasmic reticulum membrane promoting tumor metastasis and invasion in lung adenocarcinoma. Br J Cancer 2023; 128:1478-1490. [PMID: 36759724 PMCID: PMC10070493 DOI: 10.1038/s41416-023-02150-z] [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: 06/16/2021] [Revised: 12/01/2022] [Accepted: 01/11/2023] [Indexed: 02/11/2023] Open
Abstract
BACKGROUND Lung adenocarcinoma (LUAD) is one of the most common malignant tumors worldwide. Finding effective prognostic markers and therapeutic targets is of great significance for controlling metastasis and invasion clinically. METHODS The open copy-number aberrations and gene expression datasets were analysed, and the data of 102 LUAD patients was used for further validation. The cell proliferation, colony formation, migration, invasion assays and mice tumor models were used to detect the function of SEC61G. The epidermal growth factor receptor (EGFR) pathway was also detected to find the mechanism of Sec61γ. RESULTS Based on the open datasets, we found that the high level of SEC61G mRNA may drive LUAD metastasis. Furthermore, the overexpression of Sec61γ protein was significantly associated with poor prognosis and greater tumor cell proliferation and metastasis. The SEC61G knockdown could inhibit the EGFR pathway, including STAT3, AKT and PI3K, which can be reversed by Sec61γ overexpression and epithelial growth factor (EGF) supplement. CONCLUSIONS Sec61γ promoted the proliferation, metastasis, and invasion of LUAD through EGFR pathways. Sec61γ might be a potential target for the treatment of LUAD metastases.
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Affiliation(s)
- Shanqi Xu
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Xin Li
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Jianxiong Geng
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Yingyue Cao
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Yan Yu
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, China.
| | - Lishuang Qi
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China.
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2
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Loquacious modulates flaviviral RNA replication in mosquito cells. PLoS Pathog 2022; 18:e1010163. [PMID: 35482886 PMCID: PMC9089905 DOI: 10.1371/journal.ppat.1010163] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 05/10/2022] [Accepted: 04/06/2022] [Indexed: 12/25/2022] Open
Abstract
Arthropod-borne viruses infect both mosquito and mammalian hosts. While much is known about virus-host interactions that modulate viral gene expression in their mammalian host, much less is known about the interactions that involve inhibition, subversion or avoidance strategies in the mosquito host. A novel RNA-Protein interaction detection assay was used to detect proteins that directly or indirectly bind to dengue viral genomes in infected mosquito cells. Membrane-associated mosquito proteins Sec61A1 and Loquacious (Loqs) were found to be in complex with the viral RNA. Depletion analysis demonstrated that both Sec61A1 and Loqs have pro-viral functions in the dengue viral infectious cycle. Co-localization and pull-down assays showed that Loqs interacts with viral protein NS3 and both full-length and subgenomic viral RNAs. While Loqs coats the entire positive-stranded viral RNA, it binds selectively to the 3’ end of the negative-strand of the viral genome. In-depth analyses showed that the absence of Loqs did not affect translation or turnover of the viral RNA but modulated viral replication. Loqs also displayed pro-viral functions for several flaviviruses in infected mosquito cells, suggesting a conserved role for Loqs in flavivirus-infected mosquito cells. There is a wealth of information that dictates virus-host interactions in flavivirus-infected mammalian cells, yet there is only sparse information on the mechanisms that modulate viral gene expression in the mosquito host. Using a novel RNA-protein detection assay, the interactions of Sec61A1 and Loqs with the dengue viral genome were found to have pro-viral functions in infected mosquito cells. In particular, Loqs forms complexes with the positive-strand of the viral RNA and the very 3’ end of the negative-strand viral RNA. Further analyses showed that Loqs modulates viral RNA replication of dengue virus and gene amplification of several other flaviviral genomes. These findings argue that Loqs is an essential pro-viral host factor in mosquitos.
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3
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Rengaraj D, Cha DG, Lee HJ, Lee KY, Choi YH, Jung KM, Kim YM, Choi HJ, Choi HJ, Yoo E, Woo SJ, Park JS, Park KJ, Kim JK, Han JY. Dissecting chicken germ cell dynamics by combining a germ cell tracing transgenic chicken model with single-cell RNA sequencing. Comput Struct Biotechnol J 2022; 20:1654-1669. [PMID: 35465157 PMCID: PMC9010679 DOI: 10.1016/j.csbj.2022.03.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/30/2022] [Accepted: 03/31/2022] [Indexed: 02/02/2023] Open
Abstract
Avian germ cells can be distinguished by certain characteristics during development. On the basis of these characteristics, germ cells can be used for germline transmission. However, the dynamic transcriptional landscape of avian germ cells during development is unknown. Here, we used a novel germ-cell-tracing method to monitor and isolate chicken germ cells at different stages of development. We targeted the deleted in azoospermia like (DAZL) gene, a germ-cell-specific marker, to integrate a green fluorescent protein (GFP) reporter gene without affecting endogenous DAZL expression. The resulting transgenic chickens (DAZL::GFP) were used to uncover the dynamic transcriptional landscape of avian germ cells. Single-cell RNA sequencing of 4,752 male and 13,028 female DAZL::GFP germ cells isolated from embryonic day E2.5 to 1 week post-hatch identified sex-specific developmental stages (4 stages in male and 5 stages in female) and trajectories (apoptosis and meiosis paths in female) of chicken germ cells. The male and female trajectories were characterized by a gradual acquisition of stage-specific transcription factor activities. We also identified evolutionary conserved and species-specific gene expression programs during both chicken and human germ-cell development. Collectively, these novel analyses provide mechanistic insights into chicken germ-cell development.
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Affiliation(s)
- Deivendran Rengaraj
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Dong Gon Cha
- Department of New Biology, DGIST, Daegu 42988, South Korea
| | - Hong Jo Lee
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Kyung Youn Lee
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Yoon Ha Choi
- Department of New Biology, DGIST, Daegu 42988, South Korea
- Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
| | - Kyung Min Jung
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Young Min Kim
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Hee Jung Choi
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Hyeon Jeong Choi
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Eunhui Yoo
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Seung Je Woo
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Jin Se Park
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Kyung Je Park
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
| | - Jong Kyoung Kim
- Department of New Biology, DGIST, Daegu 42988, South Korea
- Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
- Corresponding authors at: POSTECH, 77 Cheongam-ro, Nam-gu, Pohang-si, Gyeongsangbuk-do 37673, South Korea (J.K. Kim). Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea (J.Y. Han).
| | - Jae Yong Han
- Department of Agricultural Biotechnology, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea
- Corresponding authors at: POSTECH, 77 Cheongam-ro, Nam-gu, Pohang-si, Gyeongsangbuk-do 37673, South Korea (J.K. Kim). Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea (J.Y. Han).
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4
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Mycolactone enhances the Ca2+ leak from endoplasmic reticulum by trapping Sec61 translocons in a Ca2+ permeable state. Biochem J 2021; 478:4005-4024. [PMID: 34726690 PMCID: PMC8650850 DOI: 10.1042/bcj20210345] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 10/19/2021] [Accepted: 11/02/2021] [Indexed: 01/17/2023]
Abstract
The Mycobacterium ulcerans exotoxin, mycolactone, is an inhibitor of co-translational translocation via the Sec61 complex. Mycolactone has previously been shown to bind to, and alter the structure of the major translocon subunit Sec61α, and change its interaction with ribosome nascent chain complexes. In addition to its function in protein translocation into the ER, Sec61 also plays a key role in cellular Ca2+ homeostasis, acting as a leak channel between the endoplasmic reticulum (ER) and cytosol. Here, we have analysed the effect of mycolactone on cytosolic and ER Ca2+ levels using compartment-specific sensors. We also used molecular docking analysis to explore potential interaction sites for mycolactone on translocons in various states. These results show that mycolactone enhances the leak of Ca2+ ions via the Sec61 translocon, resulting in a slow but substantial depletion of ER Ca2+. This leak was dependent on mycolactone binding to Sec61α because resistance mutations in this protein completely ablated the increase. Molecular docking supports the existence of a mycolactone-binding transient inhibited state preceding translocation and suggests mycolactone may also bind Sec61α in its idle state. We propose that delayed ribosomal release after translation termination and/or translocon ‘breathing' during rapid transitions between the idle and intermediate-inhibited states allow for transient Ca2+ leak, and mycolactone's stabilisation of the latter underpins the phenotype observed.
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5
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Wei YY, Liang S, Zhang YR, Lu JP, Lin FC, Liu XH. MoSec61β, the beta subunit of Sec61, is involved in fungal development and pathogenicity, plant immunity, and ER-phagy in Magnaporthe oryzae. Virulence 2020; 11:1685-1700. [PMID: 33200669 PMCID: PMC7714445 DOI: 10.1080/21505594.2020.1848983] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The process of protein translocation into the endoplasmic reticulum (ER) is the initial and decisive step in the biosynthesis of all secretory proteins and many soluble organelle proteins. In this process, the Sec61 complex is the protein-conducting channel for transport. In this study, we identified and characterized the β subunit of the Sec61 complex in Magnaporthe oryzae (MoSec61β). Compared with the wild-type strain Guy11, the ΔMosec61β mutant exhibited highly branched mycelial morphology, reduced conidiation, high sensitivity to cell wall integrity stress, severely reduced virulence to rice and barley, and restricted biotrophic invasion. The turgor pressure of ΔMosec61β was notably reduced, which affected the function of appressoria. Moreover, ΔMosec61β was also sensitive to oxidative stress and exhibited a reduced ability to overcome plant immunity. Further examination demonstrated that MoSec61β affected the normal secretion of the apoplastic effectors Bas4 and Slp1. In addition, ΔMosec61β upregulated the level of ER-phagy. In conclusion, our results demonstrate the importance of the roles played by MoSec61β in the fungal development and pathogenesis of M. oryzae.
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Affiliation(s)
- Yun-Yun Wei
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University , Hangzhou, China
| | - Shuang Liang
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University , Hangzhou, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study , Hangzhou, China
| | - Yun-Ran Zhang
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University , Hangzhou, China
| | - Jian-Ping Lu
- College of Life Sciences, Zhejiang University , Hangzhou, China
| | - Fu-Cheng Lin
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University , Hangzhou, China.,State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences , Hangzhou, China
| | - Xiao-Hong Liu
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University , Hangzhou, China
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6
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Structure of the Inhibited State of the Sec Translocon. Mol Cell 2020; 79:406-415.e7. [PMID: 32692975 PMCID: PMC7427319 DOI: 10.1016/j.molcel.2020.06.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 04/30/2020] [Accepted: 06/05/2020] [Indexed: 02/06/2023]
Abstract
Protein secretion in eukaryotes and prokaryotes involves a universally conserved protein translocation channel formed by the Sec61 complex. Unrelated small-molecule natural products and synthetic compounds inhibit Sec61 with differential effects for different substrates or for Sec61 from different organisms, making this a promising target for therapeutic intervention. To understand the mode of inhibition and provide insight into the molecular mechanism of this dynamic translocon, we determined the structure of mammalian Sec61 inhibited by the Mycobacterium ulcerans exotoxin mycolactone via electron cryo-microscopy. Unexpectedly, the conformation of inhibited Sec61 is optimal for substrate engagement, with mycolactone wedging open the cytosolic side of the lateral gate. The inability of mycolactone-inhibited Sec61 to effectively transport substrate proteins implies that signal peptides and transmembrane domains pass through the site occupied by mycolactone. This provides a foundation for understanding the molecular mechanism of Sec61 inhibitors and reveals novel features of translocon function and dynamics. The inhibited Sec translocon adopts a conformation optimal for substrate engagement The inhibitor mycolactone wedges open the lateral gate of Sec61α Mycolactone blocks the path taken by the signal peptide during engagement Resistance mutations are likely to operate by modulating translocon dynamics
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7
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Sec61β facilitates the maintenance of endoplasmic reticulum homeostasis by associating microtubules. Protein Cell 2017; 9:616-628. [PMID: 29168059 PMCID: PMC6019657 DOI: 10.1007/s13238-017-0492-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/13/2017] [Indexed: 10/25/2022] Open
Abstract
Sec61β, a subunit of the Sec61 translocon complex, is not essential in yeast and commonly used as a marker of endoplasmic reticulum (ER). In higher eukaryotes, such as Drosophila, deletion of Sec61β causes lethality, but its physiological role is unclear. Here, we show that Sec61β interacts directly with microtubules. Overexpression of Sec61β containing small epitope tags, but not a RFP tag, induces dramatic bundling of the ER and microtubule. A basic region in the cytosolic domain of Sec61β is critical for microtubule association. Depletion of Sec61β induces ER stress in both mammalian cells and Caenorhabditis elegans, and subsequent restoration of ER homeostasis correlates with the microtubule binding ability of Sec61β. Loss of Sec61β causes increased mobility of translocon complexes and reduced level of membrane-bound ribosomes. These results suggest that Sec61β may stabilize protein translocation by linking translocon complex to microtubule and provide insight into the physiological function of ER-microtubule interaction.
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8
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Covell DG. A data mining approach for identifying pathway-gene biomarkers for predicting clinical outcome: A case study of erlotinib and sorafenib. PLoS One 2017; 12:e0181991. [PMID: 28792525 PMCID: PMC5549706 DOI: 10.1371/journal.pone.0181991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 07/10/2017] [Indexed: 12/28/2022] Open
Abstract
A novel data mining procedure is proposed for identifying potential pathway-gene biomarkers from preclinical drug sensitivity data for predicting clinical responses to erlotinib or sorafenib. The analysis applies linear ridge regression modeling to generate a small (N~1000) set of baseline gene expressions that jointly yield quality predictions of preclinical drug sensitivity data and clinical responses. Standard clustering of the pathway-gene combinations from gene set enrichment analysis of this initial gene set, according to their shared appearance in molecular function pathways, yields a reduced (N~300) set of potential pathway-gene biomarkers. A modified method for quantifying pathway fitness is used to determine smaller numbers of over and under expressed genes that correspond with favorable and unfavorable clinical responses. Detailed literature-based evidence is provided in support of the roles of these under and over expressed genes in compound efficacy. RandomForest analysis of potential pathway-gene biomarkers finds average treatment prediction errors of 10% and 22%, respectively, for patients receiving erlotinib or sorafenib that had a favorable clinical response. Higher errors were found for both compounds when predicting an unfavorable clinical response. Collectively these results suggest complementary roles for biomarker genes and biomarker pathways when predicting clinical responses from preclinical data.
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Affiliation(s)
- David G. Covell
- Information Technology Branch, Developmental Therapeutics Program, National Cancer Institute, Frederick, MD, United States of America
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9
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Kaiser G, De Niz M, Zuber B, Burda PC, Kornmann B, Heussler VT, Stanway RR. High resolution microscopy reveals an unusual architecture of the Plasmodium berghei endoplasmic reticulum. Mol Microbiol 2016; 102:775-791. [PMID: 27566438 DOI: 10.1111/mmi.13490] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2016] [Indexed: 02/04/2023]
Abstract
To fuel the tremendously fast replication of Plasmodium liver stage parasites, the endoplasmic reticulum (ER) must play a critical role as a major site of protein and lipid biosynthesis. In this study, we analysed the parasite's ER morphology and function. Previous studies exploring the parasite ER have mainly focused on the blood stage. Visualizing the Plasmodium berghei ER during liver stage development, we found that the ER forms an interconnected network throughout the parasite with perinuclear and peripheral localizations. Surprisingly, we observed that the ER additionally generates huge accumulations. Using stimulated emission depletion microscopy and serial block-face scanning electron microscopy, we defined ER accumulations as intricate dense networks of ER tubules. We provide evidence that these accumulations are functional subdivisions of the parasite ER, presumably generated in response to elevated demands of the parasite, potentially consistent with ER stress. Compared to higher eukaryotes, Plasmodium parasites have a fundamentally reduced unfolded protein response machinery for reacting to ER stress. Accordingly, parasite development is greatly impaired when ER stress is applied. As parasites appear to be more sensitive to ER stress than are host cells, induction of ER stress could potentially be used for interference with parasite development.
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Affiliation(s)
- Gesine Kaiser
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Baltzerstrasse 2, 3012, Bern, Switzerland
| | - Mariana De Niz
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland.,Wellcome Trust Center for Molecular Parasitology, G12 8TA, Glasgow, UK
| | - Benoît Zuber
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012, Bern, Switzerland
| | - Paul-Christian Burda
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
| | - Benoît Kornmann
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, 8093, Zürich, Switzerland
| | - Volker T Heussler
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
| | - Rebecca R Stanway
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
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10
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Xu W, Meng Y, Surana P, Fuerst G, Nettleton D, Wise RP. The knottin-like Blufensin family regulates genes involved in nuclear import and the secretory pathway in barley-powdery mildew interactions. FRONTIERS IN PLANT SCIENCE 2015; 6:409. [PMID: 26089830 PMCID: PMC4454880 DOI: 10.3389/fpls.2015.00409] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 05/21/2015] [Indexed: 05/24/2023]
Abstract
Plants have evolved complex regulatory mechanisms to control a multi-layered defense response to microbial attack. Both temporal and spatial gene expression are tightly regulated in response to pathogen ingress, modulating both positive and negative control of defense. BLUFENSINs, small knottin-like peptides in barley, wheat, and rice, are highly induced by attack from fungal pathogens, in particular, the obligate biotrophic fungus, Blumeria graminis f. sp. hordei (Bgh), causal agent of barley powdery mildew. Previous research indicated that Blufensin1 (Bln1) functions as a negative regulator of basal defense mechanisms. In the current report, we show that BLN1 and BLN2 can both be secreted to the apoplast and Barley stripe mosaic virus (BSMV)-mediated overexpression of Bln2 increases susceptibility of barley to Bgh. Bimolecular fluorescence complementation (BiFC) assays signify that BLN1 and BLN2 can interact with each other, and with calmodulin. We then used BSMV-induced gene silencing to knock down Bln1, followed by Barley1 GeneChip transcriptome analysis, to identify additional host genes influenced by Bln1. Analysis of differential expression revealed a gene set enriched for those encoding proteins annotated to nuclear import and the secretory pathway, particularly Importin α1-b and Sec61 γ subunits. Further functional analysis of these two affected genes showed that when silenced, they also reduced susceptibility to Bgh. Taken together, we postulate that Bln1 is co-opted by Bgh to facilitate transport of disease-related host proteins or effectors, influencing the establishment of Bgh compatibility on its barley host.
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Affiliation(s)
- Weihui Xu
- Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State UniversityAmes, IA, USA
| | - Yan Meng
- Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State UniversityAmes, IA, USA
| | - Priyanka Surana
- Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State UniversityAmes, IA, USA
- Bioinformatics and Computational Biology Graduate Program, Iowa State UniversityAmes, IA, USA
| | - Greg Fuerst
- Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State UniversityAmes, IA, USA
- Corn Insects and Crop Genetics Research Unit, U.S. Department of Agriculture-Agricultural Research Service, Iowa State UniversityAmes, IA, USA
| | - Dan Nettleton
- Department of Statistics, Iowa State UniversityAmes, IA, USA
| | - Roger P. Wise
- Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State UniversityAmes, IA, USA
- Corn Insects and Crop Genetics Research Unit, U.S. Department of Agriculture-Agricultural Research Service, Iowa State UniversityAmes, IA, USA
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11
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Escherichia coli SecG is required for residual export mediated by mutant signal sequences and for SecY-SecE complex stability. J Bacteriol 2014; 197:542-52. [PMID: 25404704 DOI: 10.1128/jb.02136-14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein export to the bacterial periplasm is achieved by SecYEG, an inner membrane heterotrimer. SecY and SecE are encoded by essential genes, while SecG is not essential for growth under standard laboratory conditions. Using a quantitative and sensitive export assay, we show that SecG plays a critical role for the residual export mediated by mutant signal sequences; the magnitude of this effect is not proportional to the strength of the export defect. In contrast, export mediated by wild-type signal sequences is only barely retarded in the absence of SecG. When probed with mutant signal sequences, secG loss of function mutations display a phenotype opposite to that of prlA mutations in secY. The analysis of secG and prlA single and double mutant strains shows that the increased export conferred by several prlA alleles is enhanced in the absence of SecG. Several combinations of prlA alleles with a secG deletion cannot be easily constructed. This synthetic phenotype is conditional, indicating that cells can adapt to the presence of both alleles. The biochemical basis of this phenomenon is linked to the stability of the SecYE dimer in solubilized membranes. With prlA alleles that can be normally introduced in a secG deletion strain, SecG has only a limited effect on the stability of the SecYE dimer. With the other prlA alleles, the SecYE dimer can often be detected only in the presence of SecG. A possible role for the maintenance of SecG during evolution is proposed.
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12
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Denks K, Vogt A, Sachelaru I, Petriman NA, Kudva R, Koch HG. The Sec translocon mediated protein transport in prokaryotes and eukaryotes. Mol Membr Biol 2014; 31:58-84. [DOI: 10.3109/09687688.2014.907455] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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13
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Stefanovic L, Longo L, Zhang Y, Stefanovic B. Characterization of binding of LARP6 to the 5' stem-loop of collagen mRNAs: implications for synthesis of type I collagen. RNA Biol 2014; 11:1386-401. [PMID: 25692237 PMCID: PMC4615758 DOI: 10.1080/15476286.2014.996467] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 10/31/2014] [Indexed: 01/11/2023] Open
Abstract
Type I collagen is composed of 2 polypeptides, α1(I) and α2(I), which fold into triple helix. Collagen α1(I) and α2(I) mRNAs have a conserved stem-loop structure in their 5' UTRs, the 5'SL. LARP6 binds the 5'SL to regulate type I collagen expression. We show that 5 nucleotides within the single stranded regions of 5'SL contribute to the high affinity of LARP6 binding. Mutation of individual nucleotides abolishes the binding in gel mobility shift assay. LARP6 binding to 5'SL of collagen α2(I) mRNA is more stable than the binding to 5'SL of α1(I) mRNA, although the equilibrium binding constants are similar. The more stable binding to α2(I) mRNA may favor synthesis of the heterotrimeric type I collagen. LARP6 needs 2 domains to contact 5'SL, the La domain and the RRM. T133 in the La domain is critical for folding of the protein, while loop 3 in the RRM is critical for binding 5'SL. Loop 3 is also involved in the interaction of LARP6 and protein translocation channel SEC61. This interaction is essential for type I collagen synthesis, because LARP6 mutant which binds 5'SL but which does not interact with SEC61, suppresses collagen synthesis in a dominant negative manner. We postulate that LARP6 directly targets collagen mRNAs to the SEC61 translocons to facilitate coordinated translation of the 2 collagen mRNAs. The unique sequences of LARP6 identified in this work may have evolved to enable its role in type I collagen biosynthesis.
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Affiliation(s)
- Lela Stefanovic
- Department of Biomedical Sciences; College of Medicine; Florida State University; Tallahassee, FL USA
- Current affiliation: Molecular Biophysics; Florida State University; Tallahassee, FL USA
| | - Liam Longo
- Current affiliation: Molecular Biophysics; Florida State University; Tallahassee, FL USA
| | - Yujie Zhang
- Department of Biomedical Sciences; College of Medicine; Florida State University; Tallahassee, FL USA
- Current affiliation: Molecular Biophysics; Florida State University; Tallahassee, FL USA
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14
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Pope SM, Lässer C. Toxoplasma gondii infection of fibroblasts causes the production of exosome-like vesicles containing a unique array of mRNA and miRNA transcripts compared to serum starvation. J Extracell Vesicles 2013; 2:22484. [PMID: 24363837 PMCID: PMC3862870 DOI: 10.3402/jev.v2i0.22484] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 09/30/2013] [Accepted: 10/11/2013] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Until recently thought to be of little significance unless occurring during pregnancy, Toxoplasma gondii infection of human hosts is now known to play a larger role in mental health and is a growing concern in the health care community. We sought to elucidate a possible mechanism by which Toxoplasma infection may cause some of the behavioural pathology now associated with infection. We hypothesized that exosomes may be playing a role. METHODS We utilized electron microscopy to detect the presence and size of extracellular vesicles in the supernatants of Toxoplasma-infected human foreskin fibroblasts (HFF). We then utilized microarray analysis to discern mRNA and miRNA content of the vesicles isolated from supernatants of Toxoplasma-infected (Toxo) and serum-starved (SS) HFF. RESULTS We recovered extracellular vesicles with a size consistent with exosomes that we called exosome-like vesicles (ELVs) from the supernatants of SS and Toxo cultures. The mRNA and miRNA content of these ELVs was highly regulated creating specific and unique expression profiles comparing Toxo ELVs, SS ELVs and RNA isolated from whole cell homogenates. Interestingly, among the most enriched mRNA isolated from ELVs of Toxo cells are 4 specific mRNA species that have been described in the literature as having neurologic activity: Rab-13, eukaryotic translation elongation factor 1 alpha 1, thymosin beta 4 and LLP homolog. In addition, miRNA species uniquely expressed in Toxo ELVs include miR-23b, a well-known regulator of IL-17. CONCLUSION While the production of ELVs containing mRNAs that modify behaviour are consistent with reported Toxoplasma pathology, the mechanism of enrichment and ultimate in vivo effect of these mRNA and miRNA containing ELVs remains to be investigated.
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Affiliation(s)
- Samuel M Pope
- Department of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis IN, USA
| | - Cecilia Lässer
- Department of Internal Medicine and Clinical Nutrition, Krefting Research Centre, University of Gothenburg, Gothenburg, Sweden
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15
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Zhang WJ, Hanisch S, Kwaaitaal M, Pedersen C, Thordal-Christensen H. A component of the Sec61 ER protein transporting pore is required for plant susceptibility to powdery mildew. FRONTIERS IN PLANT SCIENCE 2013; 4:127. [PMID: 23720664 PMCID: PMC3655284 DOI: 10.3389/fpls.2013.00127] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 04/18/2013] [Indexed: 05/03/2023]
Abstract
Biotrophic pathogens, like the powdery mildew fungi, require living plant cells for their growth and reproduction. During infection, a specialized structure called the haustorium is formed by the fungus. The haustorium is surrounded by a plant cell-derived extrahaustorial membrane (EHM). Over the EHM, the fungus obtains nutrients from and secretes effector proteins into the plant cell. In the plant cell these effectors interfere with cellular processes such as pathogen defense and membrane trafficking. However, the mechanisms behind effector delivery are largely unknown. This paper provides a model for and new insights into a putative transfer mechanism of effectors into the plant cell. We show that silencing of the barley Sec61βa transcript results in decreased susceptibility to the powdery mildew fungus. HvSec61βa is a component of both the endoplasmic reticulum (ER) translocon and retrotranslocon pores, the latter being part of the ER-associated protein degradation machinery. We provide support for a model suggesting that the retrotranslocon function of HvSec61βa is required for successful powdery mildew fungal infection. HvSec61βa-GFP and a luminal ER marker were co-localized to the ER, which was found to be in close proximity to the EHM around the haustorial body, but not the haustorial fingers. This differential EHM proximity suggests that the ER, including HvSec61βa, may be actively recruited by the haustorium, potentially to provide efficient effector transfer to the cytosol. Effector transport across this EHM-ER interface may occur by a vesicle-mediated process, while the Sec61 retrotranslocon pore potentially provides an escape route for these proteins to reach the cytosol.
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Affiliation(s)
| | | | | | | | - Hans Thordal-Christensen
- *Correspondence: Hans Thordal-Christensen, Section for Plant and Soil Science, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark. e-mail:
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16
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Efficient EGFR signaling and dorsal-ventral axis patterning requires syntaxin dependent Gurken trafficking. Dev Biol 2012; 373:349-58. [PMID: 23127433 DOI: 10.1016/j.ydbio.2012.10.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 10/26/2012] [Accepted: 10/27/2012] [Indexed: 11/22/2022]
Abstract
Vesicle trafficking plays a crucial role in the establishment of cell polarity in various cellular contexts, including axis-pattern formation in the developing egg chamber of Drosophila. The EGFR ligand, Gurken (Grk), is first localized at the posterior of young oocytes for anterior-posterior axis formation and later in the dorsal anterior region for induction of the dorsal-ventral (DV) axis, but regulation of Grk localization by membrane trafficking in the oocyte remains poorly understood. Here, we report that Syntaxin 1A (Syx1A) is required for efficient trafficking of Grk protein for DV patterning. We show that Syx1A is associated with the Golgi membrane and is required for the transportation of Grk-containing vesicles along the microtubules to their dorsal anterior destination in the oocyte. Our studies reveal that the Syx1A dependent trafficking of Grk protein is required for efficient EGFR signaling during DV patterning.
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Abada PB, Larson CA, Manorek G, Adams P, Howell SB. Sec61β controls sensitivity to platinum-containing chemotherapeutic agents through modulation of the copper-transporting ATPase ATP7A. Mol Pharmacol 2012; 82:510-20. [PMID: 22710939 DOI: 10.1124/mol.112.079822] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Sec61 protein translocon is a multimeric complex that transports proteins across lipid bilayers. We discovered that the Sec61β subunit modulates cellular sensitivity to chemotherapeutic agents, particularly the platinum drugs. To investigate the mechanism, expression of Sec61β was constitutively knocked down in 2008 ovarian cancer cells. Sec61β knockdown (KD) resulted in 8-, 16.8-, and 9-fold resistance to cisplatin (cDDP), carboplatin, and oxaliplatin, respectively. Sec61β KD reduced the cellular accumulation of cDDP to 67% of that in parental cells. Baseline copper levels, copper uptake, and copper cytotoxicity were also reduced. Because copper transporters and chaperones regulate platinum drug accumulation and efflux, their expression in 2008 Sec61β-KD cells was analyzed; ATP7A was found to be 2- to 3-fold overexpressed, whereas there was no change in ATP7B, ATOX1, CTR1, or CTR2 levels. Cells lacking ATP7A did not exhibit increased cDDP resistance upon knockdown of Sec61β. Sec61β-KD cells also exhibited altered ATP7A cellular distribution. We conclude that Sec61β modulates the cytotoxicity of many chemotherapeutic agents, with the largest effect being on the platinum drugs. This modulation occurs through effects of Sec61β on the expression and distribution of ATP7A, which was shown previously to control platinum drug sequestration and cytotoxicity.
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Affiliation(s)
- Paolo B Abada
- Moores UCSD Cancer Center, La Jolla, CA 92093-0819, USA.
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18
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Wang X, Ward RE. Sec61alpha is required for dorsal closure during Drosophila embryogenesis through its regulation of Dpp signaling. Dev Dyn 2010; 239:784-97. [PMID: 20112345 DOI: 10.1002/dvdy.22219] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
During dorsal closure in Drosophila, signaling events in the dorsalmost row of epidermal cells (DME cells) direct the migration of lateral epidermal sheets towards the dorsal midline where they fuse to enclose the embryo. A Jun amino-terminal kinase (JNK) cascade in the DME cells induces the expression of Decapentaplegic (Dpp). Dpp signaling then regulates the cytoskeleton in the DME cells and amnioserosa to affect the cell shape changes necessary to complete dorsal closure. We identified a mutation in Sec61alpha that specifically perturbs dorsal closure. Sec61alpha encodes the main subunit of the translocon complex for co-translational import of proteins into the ER. JNK signaling is normal in Sec61alpha mutant embryos, but Dpp signaling is attenuated and the DME cells fail to maintain an actinomyosin cable as epithelial migration fails. Consistent with this model, dorsal closure is rescued in Sec61alpha mutant embryos by an activated form of the Dpp receptor Thick veins.
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Affiliation(s)
- Xiaochen Wang
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
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Abstract
IQGAP1, an effector of CDC42p GTPase, is a widely conserved, multifunctional protein that bundles F-actin through its N-terminus and binds microtubules through its C-terminus to modulate the cell architecture. It has emerged as a potential oncogene associated with diverse human cancers. Therefore, IQGAP1 has been heavily investigated; regardless, its precise cellular function remains unclear. Work from yeast suggests that IQGAP1 plays an important role in directed cell growth, which is a conserved feature crucial to morphogenesis, division axis, and body plan determination. New evidence suggests a conserved role for IQGAP1 in protein synthesis and membrane traffic, which may help to explain the diversity of its cellular functions. Membrane traffic mediates infections by intracellular pathogens and a range of degenerative human diseases arise from dysfunctions in intracellular traffic; thus, elucidating the mechanisms of cellular traffic will be important in order to understand the basis of a wide range of inherited and acquired human diseases. Recent evidence suggests that IQGAP1 plays its role in cell growth through regulating the conserved mTOR pathway. The mTOR signaling cascade has been implicated in membrane traffic and is activated in nearly all human cancers, but clinical response to the mTOR-specific inhibitor rapamycin has been disappointing. Thus, understanding the regulators of this pathway will be crucial in order to identify predictors of rapamycin sensitivity. In this review, I discuss emerging evidence that supports a potential role of IQGAP1 in regulating membrane traffic via regulating the mTOR pathway.
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Affiliation(s)
- Mahasin Osman
- Department of Molecular Pharmacology, Physiology and Biotechnology, Division of Biology and Medicine, Alpert School of Medicine, Brown University, Providence, RI, USA.
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