1
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Chen S, Collart MA. Membrane-associated mRNAs: A Post-transcriptional Pathway for Fine-turning Gene Expression. J Mol Biol 2024; 436:168579. [PMID: 38648968 DOI: 10.1016/j.jmb.2024.168579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 04/14/2024] [Accepted: 04/16/2024] [Indexed: 04/25/2024]
Abstract
Gene expression is a fundamental and highly regulated process involving a series of tightly coordinated steps, including transcription, post-transcriptional processing, translation, and post-translational modifications. A growing number of studies have revealed an additional layer of complexity in gene expression through the phenomenon of mRNA subcellular localization. mRNAs can be organized into membraneless subcellular structures within both the cytoplasm and the nucleus, but they can also targeted to membranes. In this review, we will summarize in particular our knowledge on localization of mRNAs to organelles, focusing on important regulators and available techniques for studying organellar localization, and significance of this localization in the broader context of gene expression regulation.
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Affiliation(s)
- Siyu Chen
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Institute of Genetics and Genomics of Geneva, Geneva, Switzerland.
| | - Martine A Collart
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Institute of Genetics and Genomics of Geneva, Geneva, Switzerland.
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2
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Hu Q, Wu G, Ma H, Zhang J, Yang Z. Signal sequence receptor subunit 3: A novel indicator of immunosuppressive tumor microenvironment and clinical benefits from immunotherapy. Cell Signal 2023; 111:110871. [PMID: 37652395 DOI: 10.1016/j.cellsig.2023.110871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 07/25/2023] [Accepted: 08/25/2023] [Indexed: 09/02/2023]
Abstract
BACKGROUND Signal sequence receptor subunit 3 (SSR3), a translocation-associated protein complex, plays a vital role in various diseases. However, its involvement in human cancers remains unclear. METHODS We conducted a comprehensive analysis by integrating data from multiple sources, including the Cancer Genome Atlas, Cancer Cell Lineage Encyclopedia, Genotype Tissue Expression, Human Protein Atlas, cBioPortal, TIMER, and ImmuCellAI. Additionally, we incorporated data from a clinical trial, two immunotherapy cohorts, and in vitro experiments to investigate SSR3's impact on cancer prognosis and immune response. RESULTS Our findings revealed a significant correlation between elevated SSR3 expression and unfavorable prognosis across various cancer types. Amplification is the most common genetic alteration in SSR3. Furthermore, functional enrichment analysis highlighted SSR3's regulatory role in promoting proliferation. In addition, SSR3 also serves as a pivotal mediator bridging the innate and adaptive immune systems and several related signaling pathways. Moreover, the correlation of SSR3 expression with tumor mutation burden in five cancer types, as well as with microsatellite instability in nine cancer types, suggests the potential of SSR3 as a predictive marker for immunotherapy response. To validate this hypothesis, we examined data from patients who underwent immunotherapy treatment. Our analysis revealed that individuals with low SSR3 expression demonstrated higher response rates to immune checkpoint inhibitors and longer overall survival compared to those with high SSR3 expression. CONCLUSIONS Our study identifies SSR3 as a potential oncogene in humans, implicated in both tumorigenesis and cancer immunity. Elevated SSR3 expression is indicative of an immunosuppressive tumor microenvironment. Therefore, SSR3 holds promise as a potential prognostic biomarker and a target for immunotherapy in cancer treatment.
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Affiliation(s)
- Qin Hu
- Department of Respiratory Medicine, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China; Department of Cardiothoracic Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China
| | - Gujie Wu
- Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Huiyun Ma
- Department of Respiratory Medicine, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China; Department of Cardiothoracic Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China
| | - Jiaxin Zhang
- Department of Cardiothoracic Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China
| | - Zheng Yang
- Department of Respiratory Medicine, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong 226000, China.
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3
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Alacid E, Irwin NAT, Smilansky V, Milner DS, Kilias ES, Leonard G, Richards TA. A diversified and segregated mRNA spliced-leader system in the parasitic Perkinsozoa. Open Biol 2022; 12:220126. [PMID: 36000319 PMCID: PMC9399869 DOI: 10.1098/rsob.220126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Spliced-leader trans-splicing (SLTS) has been described in distantly related eukaryotes and acts to mark mRNAs with a short 5′ exon, giving different mRNAs identical 5′ sequence-signatures. The function of these systems is obscure. Perkinsozoa encompasses a diversity of parasitic protists that infect bivalves, toxic-tide dinoflagellates, fish and frog tadpoles. Here, we report considerable sequence variation in the SLTS-system across the Perkinsozoa and find that multiple variant SLTS-systems are encoded in parallel in the ecologically important Perkinsozoa parasite Parvilucifera sinerae. These results demonstrate that the transcriptome of P. sinerae is segregated based on the addition of different spliced-leader (SL) exons. This segregation marks different gene categories, suggesting that SL-segregation relates to functional differentiation of the transcriptome. By contrast, both sets of gene categories are present in the single SL-transcript type sampled from Maranthos, implying that the SL-segregation of the Parvilucifera transcriptome is a recent evolutionary innovation. Furthermore, we show that the SLTS-system marks a subsection of the transcriptome with increased mRNA abundance and includes genes that encode the spliceosome system necessary for SLTS-function. Collectively, these data provide a picture of how the SLTS-systems can vary within a major evolutionary group and identify how additional transcriptional-complexity can be achieved through SL-segregation.
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Affiliation(s)
- Elisabet Alacid
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
| | - Nicholas A T Irwin
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK.,Merton College, University of Oxford, Oxford, Oxfordshire OX1 4JD, UK
| | - Vanessa Smilansky
- Living Systems Institute, University of Exeter, Exeter, Devon EX4 4QD, UK
| | - David S Milner
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
| | - Estelle S Kilias
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
| | - Guy Leonard
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
| | - Thomas A Richards
- Department of Zoology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
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4
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Sun S, Mariappan M. C-terminal tail length guides insertion and assembly of membrane proteins. J Biol Chem 2020; 295:15498-15510. [PMID: 32878985 DOI: 10.1074/jbc.ra120.012992] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 08/27/2020] [Indexed: 11/06/2022] Open
Abstract
A large number of newly synthesized membrane proteins in the endoplasmic reticulum (ER) are assembled into multiprotein complexes, but little is known about the mechanisms required for assembly membrane proteins. It has been suggested that membrane chaperones might exist, akin to the molecular chaperones that stabilize and direct the assembly of soluble protein complexes, but the mechanisms by which these proteins would bring together membrane protein components is unclear. Here, we have identified that the tail length of the C-terminal transmembrane domains (C-TMDs) determines efficient insertion and assembly of membrane proteins in the ER. We found that membrane proteins with C-TMD tails shorter than ∼60 amino acids are poorly inserted into the ER membrane, which suggests that translation is terminated before they are recognized by the Sec61 translocon for insertion. These C-TMDs with insufficient hydrophobicity are post-translationally recognized and retained by the Sec61 translocon complex, providing a time window for efficient assembly with TMDs from partner proteins. Retained TMDs that fail to assemble with their cognate TMDs are slowly translocated into the ER lumen and are recognized by the ER-associated degradation (ERAD) pathway for removal. In contrast, C-TMDs with sufficient hydrophobicity or tails longer than ∼80 residues are quickly released from the Sec61 translocon into the membrane or the ER lumen, resulting in inefficient assembly with partner TMDs. Thus, our data suggest that C-terminal tails harbor crucial signals for both the insertion and assembly of membrane proteins.
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Affiliation(s)
- Sha Sun
- Frome the Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, Yale West Campus, West Haven, Connecticut, USA
| | - Malaiyalam Mariappan
- Frome the Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, Yale West Campus, West Haven, Connecticut, USA.
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5
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Zheng J, Zheng J, Ma Y, Zuo G, Feng Y. The role of Lys2-Cl - -Lys2 salt linkages in oligomeric intermediates of RbsD protein in Escherichia coli. J Basic Microbiol 2019; 60:185-194. [PMID: 31588591 DOI: 10.1002/jobm.201900337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 09/07/2019] [Accepted: 09/13/2019] [Indexed: 11/06/2022]
Abstract
As a homo-oligomeric protein, the disassembly of Escherichia coli RbsD decamer produces a urea-unfolded oligomeric intermediate structure, as the dissociation speed of the protein is lower than that of the unfolding process. There are five Lys2-Cl- -Lys2 salt linkages to connect these subunits. To explore the role of the salt linkages in these oligomeric intermediates, the Lys2Ala mutated in the N-terminal of E. coli RbsD protein subunit was designed. It was found that the RbsD mutation protein (RbsD:K2A) loses its minor larger oligomers, which exist in RbsD, and displays other several oligomeric states (less than decamers), meanwhile the state of the oligomers depends on the protein concentration. It was also found that compared with RbsD, the crosslinking capability of the subunits of RbsD:K2A is weaker, while the crosslinking rate of dimers is higher, RbsD:K2A needs to substantially adjust its conformation to meet the space requirements when combined with d-ribose. On the basis of these results, we suggest that Lys2-Cl- -Lys2 salt linkages in E. coli RbsD protein play an important role in stabilizing the intermediate products of oligomers and maintaining interaction between the intermediate products of oligomers, which may shed light on the study of these oligomeric proteins.
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Affiliation(s)
- Jing Zheng
- School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Jie Zheng
- School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Yuanwu Ma
- School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Guocai Zuo
- School of Software and Information Engineering, Hunan Software Vocational Institute, Xiangtan, China
| | - Yongjun Feng
- School of Life Science, Beijing Institute of Technology, Beijing, China
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6
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Overexpression of signal sequence receptor γ predicts poor survival in patients with hepatocellular carcinoma. Hum Pathol 2018; 81:47-54. [PMID: 29940286 DOI: 10.1016/j.humpath.2018.06.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 05/30/2018] [Accepted: 06/09/2018] [Indexed: 01/08/2023]
Abstract
SSR subunit γ (SSR3), an SSR family member, is heavily involved in cell growth and differentiation and closely associated with many tumor types. However, the role of this protein in HCC remains unknown. In this study, we used data from public databases to analyze SSR3 expression in HCC. We subjected 20 pairs of fresh-frozen tissues to quantitative real-time polymerase chain reaction to investigate SSR3 expression. We also subjected 95 formalin-fixed, paraffin-embedded HCC tissues to immunohistochemistry to detect SSR3 expression and determine the clinical significance of SSR3 expression in HCC. Bioinformatics analysis and quantitative real-time polymerase chain reaction results showed that compared with that in adjacent normal liver tissues, SSR3 was highly expressed in HCC tissues. High SSR3 expression was positively correlated with tumor size (P < .01), cancer embolus (P = .01), TNM stages (P = .02), and differentiation grades (P < .01). Kaplan-Meier and Cox proportional hazards analyses indicated that high SSR3 expression was significantly associated with poor survival in HCC patients and that SSR3 was an independent prognostic factor for overall survival in HCC patients. In conclusion, SSR3 acts as an oncogene in HCC and can therefore serve as a biomarker for the prognoses of HCC patients.
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7
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Queiroz RML, Ricart CAO, Machado MO, Bastos IMD, de Santana JM, de Sousa MV, Roepstorff P, Charneau S. Insight into the Exoproteome of the Tissue-Derived Trypomastigote form of Trypanosoma cruzi. Front Chem 2016; 4:42. [PMID: 27872839 PMCID: PMC5097913 DOI: 10.3389/fchem.2016.00042] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 10/19/2016] [Indexed: 01/07/2023] Open
Abstract
The protozoan parasite Trypanosoma cruzi causes Chagas disease, one of the major neglected infectious diseases. It has the potential to infect any nucleated mammalian cell. The secreted/excreted protein repertoire released by T. cruzi trypomastigotes is crucial in host-pathogen interactions. In this study, mammalian tissue culture-derived trypomastigotes (Y strain) were used to characterize the exoproteome of the infective bloodstream life form. Proteins released into the serum-free culture medium after 3 h of incubation were harvested and digested with trypsin. NanoLC-MS/MS analysis resulted in the identification of 540 proteins, the largest set of released proteins identified to date in Trypanosoma spp. Bioinformatic analysis predicted most identified proteins as secreted, predominantly by non-classical pathways, and involved in host-cell infection. Some proteins possess predicted GPI-anchor signals, these being mostly trans-sialidases, mucin associated surface proteins and surface glycoproteins. Moreover, we enriched phosphopeptides and glycopeptides from tryptic digests. The majority of identified glycoproteins are trans-sialidases and surface glycoproteins involved in host-parasite interaction. Conversely, most identified phosphoproteins have no Gene Ontology classification. The existence of various proteins related to similar functions in the exoproteome likely reflects this parasite's enhanced mechanisms for adhesion, invasion, and internalization of different host-cell types, and escape from immune defenses.
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Affiliation(s)
- Rayner M L Queiroz
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, University of Brasilia, Brasilia, Brazil; Department of Biochemistry and Molecular Biology, University of Southern DenmarkOdense, Denmark
| | - Carlos A O Ricart
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, University of Brasilia , Brasilia, Brazil
| | - Mara O Machado
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, University of Brasilia , Brasilia, Brazil
| | - Izabela M D Bastos
- Laboratory of Host-Pathogen Interaction, Department of Cell Biology, University of Brasilia Brasilia, Brazil
| | - Jaime M de Santana
- Laboratory of Host-Pathogen Interaction, Department of Cell Biology, University of Brasilia Brasilia, Brazil
| | - Marcelo V de Sousa
- Laboratory of Host-Pathogen Interaction, Department of Cell Biology, University of Brasilia Brasilia, Brazil
| | - Peter Roepstorff
- Department of Biochemistry and Molecular Biology, University of Southern Denmark Odense, Denmark
| | - Sébastien Charneau
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, University of Brasilia , Brasilia, Brazil
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8
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Heaton NS, Moshkina N, Fenouil R, Gardner TJ, Aguirre S, Shah PS, Zhao N, Manganaro L, Hultquist JF, Noel J, Sachs D, Hamilton J, Leon PE, Chawdury A, Tripathi S, Melegari C, Campisi L, Hai R, Metreveli G, Gamarnik AV, García-Sastre A, Greenbaum B, Simon V, Fernandez-Sesma A, Krogan NJ, Mulder LCF, van Bakel H, Tortorella D, Taunton J, Palese P, Marazzi I. Targeting Viral Proteostasis Limits Influenza Virus, HIV, and Dengue Virus Infection. Immunity 2016; 44:46-58. [PMID: 26789921 DOI: 10.1016/j.immuni.2015.12.017] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 12/22/2022]
Abstract
Viruses are obligate parasites and thus require the machinery of the host cell to replicate. Inhibition of host factors co-opted during active infection is a strategy hosts use to suppress viral replication and a potential pan-antiviral therapy. To define the cellular proteins and processes required for a virus during infection is thus crucial to understanding the mechanisms of virally induced disease. In this report, we generated fully infectious tagged influenza viruses and used infection-based proteomics to identify pivotal arms of cellular signaling required for influenza virus growth and infectivity. Using mathematical modeling and genetic and pharmacologic approaches, we revealed that modulation of Sec61-mediated cotranslational translocation selectively impaired glycoprotein proteostasis of influenza as well as HIV and dengue viruses and led to inhibition of viral growth and infectivity. Thus, by studying virus-human protein-protein interactions in the context of active replication, we have identified targetable host factors for broad-spectrum antiviral therapies.
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Affiliation(s)
- Nicholas S Heaton
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Natasha Moshkina
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Romain Fenouil
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Thomas J Gardner
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Sebastian Aguirre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Priya S Shah
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158-2140, USA
| | - Nan Zhao
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Lara Manganaro
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Judd F Hultquist
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158-2140, USA
| | - Justine Noel
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - David Sachs
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Jennifer Hamilton
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Paul E Leon
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Amit Chawdury
- Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Division of Hematology and Oncology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Shashank Tripathi
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Camilla Melegari
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Laura Campisi
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Rong Hai
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Giorgi Metreveli
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Andrea V Gamarnik
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires 1405, Argentina
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Division of Infectious Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Benjamin Greenbaum
- Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Division of Hematology and Oncology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Viviana Simon
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Ana Fernandez-Sesma
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158-2140, USA
| | - Lubbertus C F Mulder
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Harm van Bakel
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Domenico Tortorella
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Jack Taunton
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158-2140, USA
| | - Peter Palese
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Ivan Marazzi
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA.
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9
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Di Bartolo N, Compton ELR, Warne T, Edwards PC, Tate CG, Schertler GFX, Booth PJ. Complete Reversible Refolding of a G-Protein Coupled Receptor on a Solid Support. PLoS One 2016; 11:e0151582. [PMID: 26982879 PMCID: PMC4794186 DOI: 10.1371/journal.pone.0151582] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 03/01/2016] [Indexed: 12/22/2022] Open
Abstract
The factors defining the correct folding and stability of integral membrane proteins are poorly understood. Folding of only a few select membrane proteins has been scrutinised, leaving considerable deficiencies in knowledge for large protein families, such as G protein coupled receptors (GPCRs). Complete reversible folding, which is problematic for any membrane protein, has eluded this dominant receptor family. Moreover, attempts to recover receptors from denatured states are inefficient, yielding at best 40–70% functional protein. We present a method for the reversible unfolding of an archetypal family member, the β1-adrenergic receptor, and attain 100% recovery of the folded, functional state, in terms of ligand binding, compared to receptor which has not been subject to any unfolding and retains its original, folded structure. We exploit refolding on a solid support, which could avoid unwanted interactions and aggregation that occur in bulk solution. We determine the changes in structure and function upon unfolding and refolding. Additionally, we employ a method that is relatively new to membrane protein folding; pulse proteolysis. Complete refolding of β1-adrenergic receptor occurs in n-decyl-β-D-maltoside (DM) micelles from a urea-denatured state, as shown by regain of its original helical structure, ligand binding and protein fluorescence. The successful refolding strategy on a solid support offers a defined method for the controlled refolding and recovery of functional GPCRs and other membrane proteins that suffer from instability and irreversible denaturation once isolated from their native membranes.
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Affiliation(s)
- Natalie Di Bartolo
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
- * E-mail:
| | - Emma L. R. Compton
- Organisational and Staff Development Unit, University of Strathclyde, Glasgow, United Kingdom
| | - Tony Warne
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Patricia C. Edwards
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Christopher G. Tate
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | | | - Paula J. Booth
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
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10
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Folding energetics and oligomerization of polytopic α-helical transmembrane proteins. Arch Biochem Biophys 2014; 564:281-96. [DOI: 10.1016/j.abb.2014.07.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 06/26/2014] [Accepted: 07/14/2014] [Indexed: 01/06/2023]
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11
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Menon R, Gasser RB, Mitreva M, Ranganathan S. An analysis of the transcriptome of Teladorsagia circumcincta: its biological and biotechnological implications. BMC Genomics 2012; 13 Suppl 7:S10. [PMID: 23282110 PMCID: PMC3521389 DOI: 10.1186/1471-2164-13-s7-s10] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Teladorsagia circumcincta (order Strongylida) is an economically important parasitic nematode of small ruminants (including sheep and goats) in temperate climatic regions of the world. Improved insights into the molecular biology of this parasite could underpin alternative methods required to control this and related parasites, in order to circumvent major problems associated with anthelmintic resistance. The aims of the present study were to define the transcriptome of the adult stage of T. circumcincta and to infer the main pathways linked to molecules known to be expressed in this nematode. Since sheep develop acquired immunity against T. circumcincta, there is some potential for the development of a vaccine against this parasite. Hence, we infer excretory/secretory molecules for T. circumcincta as possible immunogens and vaccine candidates. RESULTS A total of 407,357 ESTs were assembled yielding 39,852 putative gene sequences. Conceptual translation predicted 24,013 proteins, which were then subjected to detailed annotation which included pathway mapping of predicted proteins (including 112 excreted/secreted [ES] and 226 transmembrane peptides), domain analysis and GO annotation was carried out using InterProScan along with BLAST2GO. Further analysis was carried out for secretory signal peptides using SignalP and non-classical sec pathway using SecretomeP tools. For ES proteins, key pathways, including Fc epsilon RI, T cell receptor, and chemokine signalling as well as leukocyte transendothelial migration were inferred to be linked to immune responses, along with other pathways related to neurodegenerative diseases and infectious diseases, which warrant detailed future studies. KAAS could identify new and updated pathways like phagosome and protein processing in endoplasmic reticulum. Domain analysis for the assembled dataset revealed families of serine, cysteine and proteinase inhibitors which might represent targets for parasite intervention. InterProScan could identify GO terms pertaining to the extracellular region. Some of the important domain families identified included the SCP-like extracellular proteins which belong to the pathogenesis-related proteins (PRPs) superfamily along with C-type lectin, saposin-like proteins. The 'extracellular region' that corresponds to allergen V5/Tpx-1 related, considered important in parasite-host interactions, was also identified. Six cysteine motif (SXC1) proteins, transthyretin proteins, C-type lectins, activation-associated secreted proteins (ASPs), which could represent potential candidates for developing novel anthelmintics or vaccines were few other important findings. Of these, SXC1, protein kinase domain-containing protein, trypsin family protein, trypsin-like protease family member (TRY-1), putative major allergen and putative lipid binding protein were identified which have not been reported in the published T. circumcincta proteomics analysis. Detailed analysis of 6,058 raw EST sequences from dbEST revealed 315 putatively secreted proteins. Amongst them, C-type single domain activation associated secreted protein ASP3 precursor, activation-associated secreted proteins (ASP-like protein), cathepsin B-like cysteine protease, cathepsin L cysteine protease, cysteine protease, TransThyretin-Related and Venom-Allergen-like proteins were the key findings. CONCLUSIONS We have annotated a large dataset ESTs of T. circumcincta and undertaken detailed comparative bioinformatics analyses. The results provide a comprehensive insight into the molecular biology of this parasite and disease manifestation which provides potential focal point for future research. We identified a number of pathways responsible for immune response. This type of large-scale computational scanning could be coupled with proteomic and metabolomic studies of this parasite leading to novel therapeutic intervention and disease control strategies. We have also successfully affirmed the use of bioinformatics tools, for the study of ESTs, which could now serve as a benchmark for the development of new computational EST analysis pipelines.
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Affiliation(s)
- Ranjeeta Menon
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
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12
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Öjemalm K, Watson HR, Roboti P, Cross BCS, Warwicker J, von Heijne G, High S. Positional editing of transmembrane domains during ion channel assembly. J Cell Sci 2012; 126:464-72. [PMID: 23230148 PMCID: PMC3613178 DOI: 10.1242/jcs.111773] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The integration of transmembrane (TM)-spanning regions of many channels and ion transporters is potentially compromised by the presence of polar and charged residues required for biological function. Although the two TMs of the ATP-gated ion channel subunit P2X2 each contain charged/polar amino acids, we found that each TM is efficiently membrane inserted when it is analysed in isolation, and uncovered no evidence for cooperativity between these two TMs during P2X2 integration. However, using minimal N-glycosylation distance mapping, we find that the positioning of TM2 in newly synthesized P2X2 monomers is distinct from that seen in subunits of the high-resolution structures of assembled homologous trimers. We conclude that P2X2 monomers are initially synthesised at the endoplasmic reticulum in a distinct conformation, where the extent of the TM-spanning regions is primarily defined by the thermodynamic cost of their membrane integration at the Sec61 translocon. In this model, TM2 of P2X2 subsequently undergoes a process of positional editing within the membrane that correlates with trimerisation of the monomer, a process requiring specific polar/charged residues in both TM1 and TM2. We postulate that the assembly process offsets any energetic cost of relocating TM2, and find evidence that positional editing of TM2 in the acid-sensing ion channel (ASIC1a) is even more pronounced than that observed for P2X2. Taken together, these data further underline the potential complexities involved in accurately predicting TM domains. We propose that the orchestrated repositioning of TM segments during subunit oligomerisation plays an important role in generating the functional architecture of active ion channels, and suggest that the regulation of this underappreciated biosynthetic step may provide an elegant mechanism for maintaining ER homeostasis.
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Affiliation(s)
- Karin Öjemalm
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-10691 Stockholm, Sweden
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Guerriero CJ, Brodsky JL. The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology. Physiol Rev 2012; 92:537-76. [PMID: 22535891 DOI: 10.1152/physrev.00027.2011] [Citation(s) in RCA: 306] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.
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Affiliation(s)
- Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, PA 15260, USA
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Palmitoylated calnexin is a key component of the ribosome-translocon complex. EMBO J 2012; 31:1823-35. [PMID: 22314232 DOI: 10.1038/emboj.2012.15] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 01/03/2012] [Indexed: 12/11/2022] Open
Abstract
A third of the human genome encodes N-glycosylated proteins. These are co-translationally translocated into the lumen/membrane of the endoplasmic reticulum (ER) where they fold and assemble before they are transported to their final destination. Here, we show that calnexin, a major ER chaperone involved in glycoprotein folding is palmitoylated and that this modification is mediated by the ER palmitoyltransferase DHHC6. This modification leads to the preferential localization of calnexin to the perinuclear rough ER, at the expense of ER tubules. Moreover, palmitoylation mediates the association of calnexin with the ribosome-translocon complex (RTC) leading to the formation of a supercomplex that recruits the actin cytoskeleton, leading to further stabilization of the assembly. When formation of the calnexin-RTC supercomplex was affected by DHHC6 silencing, mutation of calnexin palmitoylation sites or actin depolymerization, folding of glycoproteins was impaired. Our findings thus show that calnexin is a stable component of the RTC in a manner that is exquisitely dependent on its palmitoylation status. This association is essential for the chaperone to capture its client proteins as they emerge from the translocon, acquire their N-linked glycans and initiate folding.
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Garg G, Ranganathan S. In silico secretome analysis approach for next generation sequencing transcriptomic data. BMC Genomics 2011; 12 Suppl 3:S14. [PMID: 22369360 PMCID: PMC3333173 DOI: 10.1186/1471-2164-12-s3-s14] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Excretory/secretory proteins (ESPs) play a major role in parasitic infection as they are present at the host-parasite interface and regulate host immune system. In case of parasitic helminths, transcriptomics has been used extensively to understand the molecular basis of parasitism and for developing novel therapeutic strategies against parasitic infections. However, none of transcriptomic studies have extensively covered ES protein prediction for identifying novel therapeutic targets, especially as parasites adopt non-classical secretion pathways. RESULTS We developed a semi-automated computational approach for prediction and annotation of ES proteins using transcriptomic data from next generation sequencing platforms. For the prediction of non-classically secreted proteins, we have used an improved computational strategy, together with homology matching to a dataset of experimentally determined parasitic helminth ES proteins. We applied this protocol to analyse 454 short reads of parasitic nematode, Strongyloides ratti. From 296231 reads, we derived 28901 contigs, which were translated into 20877 proteins. Based on our improved ES protein prediction pipeline, we identified 2572 ES proteins, of which 407 (1.9%) proteins have classical N-terminal signal peptides, 923 (4.4%) were computationally identified as non-classically secreted while 1516 (7.26%) were identified by homology to experimentally identified parasitic helminth ES proteins. Out of 2572 ES proteins, 2310 (89.8%) ES proteins had homologues in the free-living nematode Caenorhabditis elegans and 2220 (86.3%) in parasitic nematodes. We could functionally annotate 1591 (61.8%) ES proteins with protein families and domains and establish pathway associations for 691 (26.8%) proteins. In addition, we have identified 19 representative ES proteins, which have no homologues in the host organism but homologous to lethal RNAi phenotypes in C. elegans, as potential therapeutic targets. CONCLUSION We report a comprehensive approach using freely available computational tools for the secretome analysis of NGS data. This approach has been applied to S. ratti 454 transcriptomic data for in silico excretory/secretory proteins prediction and analysis, providing a foundation for developing new therapeutic solutions for parasitic infections.
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Affiliation(s)
- Gagan Garg
- Dept. of Chemistry and Biomolecular Sciences, Macquarie University, Sydney NSW 2109, Australia
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Houck SA, Cyr DM. Mechanisms for quality control of misfolded transmembrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1108-14. [PMID: 22100602 DOI: 10.1016/j.bbamem.2011.11.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 11/01/2011] [Accepted: 11/03/2011] [Indexed: 01/21/2023]
Abstract
To prevent the accumulation of misfolded and aggregated proteins, the cell has developed a complex network of cellular quality control (QC) systems to recognize misfolded proteins and facilitate their refolding or degradation. The cell faces numerous obstacles when performing quality control on transmembrane proteins. Transmembrane proteins have domains on both sides of a membrane and QC systems in distinct compartments must coordinate to monitor the folding status of the protein. Additionally, transmembrane domains can have very complex organization and QC systems must be able to monitor the assembly of transmembrane domains in the membrane. In this review, we will discuss the QC systems involved in repair and degradation of misfolded transmembrane proteins. Also, we will elaborate on the factors that recognize folding defects of transmembrane domains and what happens when misfolded transmembrane proteins escape QC and aggregate. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Scott A Houck
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA
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Gupta S, Wardhan V, Verma S, Gayali S, Rajamani U, Datta A, Chakraborty S, Chakraborty N. Characterization of the Secretome of Chickpea Suspension Culture Reveals Pathway Abundance and the Expected and Unexpected Secreted Proteins. J Proteome Res 2011; 10:5006-15. [DOI: 10.1021/pr200493d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Sonika Gupta
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Vijay Wardhan
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Shikha Verma
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Saurabh Gayali
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Uma Rajamani
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Asis Datta
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Subhra Chakraborty
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Niranjan Chakraborty
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi-110067, India
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Membrane Insertion and Topology of the Translocating Chain-Associating Membrane Protein (TRAM). J Mol Biol 2011; 406:571-82. [DOI: 10.1016/j.jmb.2011.01.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 12/30/2010] [Accepted: 01/04/2011] [Indexed: 11/24/2022]
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Zimmermann R, Eyrisch S, Ahmad M, Helms V. Protein translocation across the ER membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:912-24. [PMID: 20599535 DOI: 10.1016/j.bbamem.2010.06.015] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/11/2010] [Accepted: 06/14/2010] [Indexed: 01/02/2023]
Abstract
Protein translocation into the endoplasmic reticulum (ER) is the first and decisive step in the biogenesis of most extracellular and many soluble organelle proteins in eukaryotic cells. It is mechanistically related to protein export from eubacteria and archaea and to the integration of newly synthesized membrane proteins into the ER membrane and the plasma membranes of eubacteria and archaea (with the exception of tail anchored membrane proteins). Typically, protein translocation into the ER involves cleavable amino terminal signal peptides in precursor proteins and sophisticated transport machinery components in the cytosol, the ER membrane, and the ER lumen. Depending on the hydrophobicity and/or overall amino acid content of the precursor protein, transport can occur co- or posttranslationally. The respective mechanism determines the requirements for certain cytosolic transport components. The two mechanisms merge at the level of the ER membrane, specifically, at the heterotrimeric Sec61 complex present in the membrane. The Sec61 complex provides a signal peptide recognition site and forms a polypeptide conducting channel. Apparently, the Sec61 complex is gated by various ligands, such as signal peptides of the transport substrates, ribosomes (in cotranslational transport), and the ER lumenal molecular chaperone, BiP. Binding of BiP to the incoming polypeptide contributes to efficiency and unidirectionality of transport. Recent insights into the structure of the Sec61 complex and the comparison of the transport mechanisms and machineries in the yeast Saccharomyces cerevisiae, the human parasite Trypanosoma brucei, and mammals have various important mechanistic as well as potential medical implications. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Richard Zimmermann
- Medical Biochemistry & Molecular Biology, Saarland University, D-66041 Homburg, Germany.
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20
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Fujita H, Kida Y, Hagiwara M, Morimoto F, Sakaguchi M. Positive charges of translocating polypeptide chain retrieve an upstream marginal hydrophobic segment from the endoplasmic reticulum lumen to the translocon. Mol Biol Cell 2010; 21:2045-56. [PMID: 20427573 PMCID: PMC2883948 DOI: 10.1091/mbc.e09-12-1060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Positive charges of nascent chain facilitate membrane spanning of a marginally hydrophobic segment, even when separated by 70 residues from the segment. The segment is exposed to the lumen and then slides back into the membrane. They not only fix the hydrophobic segment in the membrane, but exert a much more dynamic action than previously realized. Positively charged amino acid residues are well recognized topology determinants of membrane proteins. They contribute to the stop-translocation of a polypeptide translocating through the translocon and to determine the orientation of signal sequences penetrating the membrane. Here we analyzed the function of these positively charged residues during stop-translocation in vitro. Surprisingly, the positive charges facilitated membrane spanning of a marginally hydrophobic segment, even when separated from the hydrophobic segment by 70 residues. In this case, the hydrophobic segment was exposed to the lumen, and then the downstream positive charges triggered the segment to slide back into the membrane. The marginally hydrophobic segment spanned the membrane, but maintained access to the water environment. The positive charges not only fix the hydrophobic segment in the membrane at its flanking position, but also have a much more dynamic action than previously realized.
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Affiliation(s)
- Hidenobu Fujita
- Graduate School of Life Science, University of Hyogo, Kouto Ako-gun, Hyogo 678-1297, Japan
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Abstract
The secretome encompasses the complete set of gene products secreted by a cell. Recent studies on secretome analysis reveal that secretory proteins play an important role in pathogen infection and host-pathogen interactions. Excretory/secretory proteins of pathogens change the host cell environment by suppressing the immune system, to aid the proliferation of infection. Identifying secretory proteins involved in pathogen infection will lead to the discovery of potential drug targets and biomarkers for diagnostic applications.
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Affiliation(s)
- Shoba Ranganathan
- Department of Chemistry and Biomolecular Sciences and ARC Centre of Excellence in Bioinformatics, Macquarie University, Sydney NSW 2109, Australia
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Tanegashima K, Zhao H, Rebbert ML, Dawid IB. Coordinated activation of the secretory pathway during notochord formation in the Xenopus embryo. Development 2009; 136:3543-8. [PMID: 19793890 DOI: 10.1242/dev.036715] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We compared the transcriptome in the developing notochord of Xenopus laevis embryos with that of other embryonic regions. A coordinated and intense activation of a large set of secretory pathway genes was observed in the notochord, but not in notochord precursors in the axial mesoderm at early gastrula stage. The genes encoding Xbp1 and Creb3l2 were also activated in the notochord. These two transcription factors are implicated in the activation of secretory pathway genes during the unfolded protein response, where cells react to the stress of a build-up of unfolded proteins in their endoplasmic reticulum. Xbp1 and Creb3l2 are differentially expressed but not differentially activated in the notochord. Reduction of expression of Xbp1 or Creb3l2 by injection of antisense morpholinos led to strong deficits in notochord but not somitic muscle development. In addition, the expression of some, but not all, genes encoding secretory proteins was inhibited by injection of xbp1 morpholinos. Furthermore, expression of activated forms of Xbp1 or Creb3l2 in animal explants could activate a similar subset of secretory pathway genes. We conclude that coordinated activation of a battery of secretory pathway genes mediated by Xbp1 and Creb/ATF factors is a characteristic and necessary feature of notochord formation.
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Affiliation(s)
- Kosuke Tanegashima
- Laboratory of Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Doolittle MH, Neher SB, Ben-Zeev O, Ling-Liao J, Gallagher CM, Hosseini M, Yin F, Wong H, Walter P, Péterfy M. Lipase maturation factor LMF1, membrane topology and interaction with lipase proteins in the endoplasmic reticulum. J Biol Chem 2009; 284:33623-33. [PMID: 19783858 DOI: 10.1074/jbc.m109.049395] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipase maturation factor 1 (LMF1) is predicted to be a polytopic protein localized to the endoplasmic reticulum (ER) membrane. It functions in the post-translational attainment of enzyme activity for both lipoprotein lipase and hepatic lipase. By using transmembrane prediction methods in mouse and human orthologs, models of LMF1 topology were constructed and tested experimentally. Employing a tagging strategy that used insertion of ectopic glycan attachment sites and terminal fusions of green fluorescent protein, we established a five-transmembrane model, thus dividing LMF1 into six domains. Three domains were found to face the cytoplasm (the amino-terminal domain and loops B and D), and the other half was oriented to the ER lumen (loops A and C and the carboxyl-terminal domain). This representative model shows the arrangement of an evolutionarily conserved domain within LMF1 (DUF1222) that is essential to lipase maturation. DUF1222 comprises four of the six domains, with the two largest ones facing the ER lumen. We showed for the first time, using several naturally occurring variants featuring DUF1222 truncations, that Lmf1 interacts physically with lipoprotein lipase and hepatic lipase and localizes the lipase interaction site to loop C within DUF1222. We discuss the implication of our results with regard to lipase maturation and DUF1222 domain structure.
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Affiliation(s)
- Mark H Doolittle
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
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Abstract
The insertion efficiency of transmembrane (TM) helices by the Sec61 translocon depends on helix amino acid composition, the positions of the amino acids within the helix, and helix length. We have used an in vitro expression system to examine systematically the insertion efficiency of short polyleucine segments (L(n), n = 4 ... 12) flanked at either end by 4-residue sequences of the form XXPX-L(n)-XPXX with X = G, N, D, or K. Except for X = K, insertion efficiency (p) is <10% for n < 8, but rises steeply to 100% for n = 12. For X = K, p is already close to 100% for n = 10. A similar pattern is observed for synthetic peptides incorporated into oriented phospholipid bilayer arrays, consistent with the idea that recognition of TM segments by the translocon critically involves physical partitioning of nascent peptide chains into the lipid bilayer. Molecular dynamics simulations suggest that insertion efficiency is determined primarily by the energetic cost of distorting the bilayer in the vicinity of the TM helix. Very short lysine-flanked leucine segments can reduce the energetic cost by extensive hydrogen bonding with water and lipid phosphate groups (snorkeling) and by partial unfolding.
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Pitonzo D, Yang Z, Matsumura Y, Johnson AE, Skach WR. Sequence-specific retention and regulated integration of a nascent membrane protein by the endoplasmic reticulum Sec61 translocon. Mol Biol Cell 2008; 20:685-98. [PMID: 19019984 DOI: 10.1091/mbc.e08-09-0902] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A defining feature of eukaryotic polytopic protein biogenesis involves integration, folding, and packing of hydrophobic transmembrane (TM) segments into the apolar environment of the lipid bilayer. In the endoplasmic reticulum, this process is facilitated by the Sec61 translocon. Here, we use a photocross-linking approach to examine integration intermediates derived from the ATP-binding cassette transporter cystic fibrosis transmembrane conductance regulator (CFTR) and show that the timing of translocon-mediated integration can be regulated at specific stages of synthesis. During CFTR biogenesis, the eighth TM segment exits the ribosome and enters the translocon in proximity to Sec61alpha. This interaction is initially weak, and TM8 spontaneously dissociates from the translocon when the nascent chain is released from the ribosome. Polypeptide extension by only a few residues, however, results in stable TM8-Sec61alpha photocross-links that persist after peptidyl-tRNA bond cleavage. Retention of these untethered polypeptides within the translocon requires ribosome binding and is mediated by an acidic residue, Asp924, near the center of the putative TM8 helix. Remarkably, at this stage of synthesis, nascent chain release from the translocon is also strongly inhibited by ATP depletion. These findings contrast with passive partitioning models and indicate that Sec61alpha can retain TMs and actively inhibit membrane integration in a sequence-specific and ATP-dependent manner.
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Affiliation(s)
- David Pitonzo
- Department of Biochemistry and Molecular Biology, Oregon Health and Sciences University, Portland, OR 97239, USA
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Calì T, Vanoni O, Molinari M. The endoplasmic reticulum crossroads for newly synthesized polypeptide chains. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2008; 83:135-79. [PMID: 19186254 DOI: 10.1016/s0079-6603(08)00604-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Tito Calì
- Institute for Research in Biomedicine, Bellizona, Switzerland
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