1
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Lang S, Nguyen D, Bhadra P, Jung M, Helms V, Zimmermann R. Signal Peptide Features Determining the Substrate Specificities of Targeting and Translocation Components in Human ER Protein Import. Front Physiol 2022; 13:833540. [PMID: 35899032 PMCID: PMC9309488 DOI: 10.3389/fphys.2022.833540] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 05/17/2022] [Indexed: 12/11/2022] Open
Abstract
In human cells, approximately 30% of all polypeptides enter the secretory pathway at the level of the endoplasmic reticulum (ER). This process involves cleavable amino-terminal signal peptides (SPs) or more or less amino-terminal transmembrane helices (TMHs), which serve as targeting determinants, at the level of the precursor polypeptides and a multitude of cytosolic and ER proteins, which facilitate their ER import. Alone or in combination SPs and TMHs guarantee the initial ER targeting as well as the subsequent membrane integration or translocation. Cytosolic SRP and SR, its receptor in the ER membrane, mediate cotranslational targeting of most nascent precursor polypeptide chains to the polypeptide-conducting Sec61 complex in the ER membrane. Alternatively, fully-synthesized precursor polypeptides and certain nascent precursor polypeptides are targeted to the ER membrane by either the PEX-, SND-, or TRC-pathway. Although these targeting pathways may have overlapping functions, the question arises how relevant this is under cellular conditions and which features of SPs and precursor polypeptides determine preference for a certain pathway. Irrespective of their targeting pathway(s), most precursor polypeptides are integrated into or translocated across the ER membrane via the Sec61 channel. For some precursor polypeptides specific Sec61 interaction partners have to support the gating of the channel to the open state, again raising the question why and when this is the case. Recent progress shed light on the client spectrum and specificities of some auxiliary components, including Sec62/Sec63, TRAM1 protein, and TRAP. To address the question which precursors use a certain pathway or component in intact human cells, i.e., under conditions of fast translation rates and molecular crowding, in the presence of competing precursors, different targeting organelles, and relevant stoichiometries of the involved components, siRNA-mediated depletion of single targeting or transport components in HeLa cells was combined with label-free quantitative proteomics and differential protein abundance analysis. Here, we present a summary of the experimental approach as well as the resulting differential protein abundance analyses and discuss their mechanistic implications in light of the available structural data.
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Affiliation(s)
- Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
- *Correspondence: Sven Lang, ; Richard Zimmermann,
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Pratiti Bhadra
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Martin Jung
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
- *Correspondence: Sven Lang, ; Richard Zimmermann,
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2
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Tirincsi A, Sicking M, Hadzibeganovic D, Haßdenteufel S, Lang S. The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum. Int J Mol Sci 2021; 23:143. [PMID: 35008565 PMCID: PMC8745461 DOI: 10.3390/ijms23010143] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/15/2022] Open
Abstract
Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.
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Affiliation(s)
- Andrea Tirincsi
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Drazena Hadzibeganovic
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Sarah Haßdenteufel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
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3
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Park J, Chang J, Hwang HJ, Jeong K, Lee HJ, Ha H, Park Y, Lim C, Woo JS, Kim YK. The pioneer round of translation ensures proper targeting of ER and mitochondrial proteins. Nucleic Acids Res 2021; 49:12517-12534. [PMID: 34850140 PMCID: PMC8643669 DOI: 10.1093/nar/gkab1098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 10/14/2021] [Accepted: 10/21/2021] [Indexed: 11/12/2022] Open
Abstract
The pioneer (or first) round of translation of newly synthesized mRNAs is largely mediated by a nuclear cap-binding complex (CBC). In a transcriptome-wide analysis of polysome-associated and CBC-bound transcripts, we identify RN7SL1, a noncoding RNA component of a signal recognition particle (SRP), as an interaction partner of the CBC. The direct CBC–SRP interaction safeguards against abnormal expression of polypeptides from a ribosome–nascent chain complex (RNC)–SRP complex until the latter is properly delivered to the endoplasmic reticulum. Failure of this surveillance causes abnormal expression of misfolded proteins at inappropriate intracellular locations, leading to a cytosolic stress response. This surveillance pathway also blocks protein synthesis through RNC–SRP misassembled on an mRNA encoding a mitochondrial protein. Thus, our results reveal a surveillance pathway in which pioneer translation ensures proper targeting of endoplasmic reticulum and mitochondrial proteins.
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Affiliation(s)
- Joori Park
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Jeeyoon Chang
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyun Jung Hwang
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Kwon Jeong
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyuk-Joon Lee
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hongseok Ha
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Yeonkyoung Park
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Chunghun Lim
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Jae-Sung Woo
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Yoon Ki Kim
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
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4
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Pinheiro H, Pimentel MR, Sequeira C, Oliveira LM, Pezzarossa A, Roman W, Gomes ER. mRNA distribution in skeletal muscle is associated with mRNA size. J Cell Sci 2021; 134:jcs256388. [PMID: 34297126 PMCID: PMC7611476 DOI: 10.1242/jcs.256388] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 06/18/2021] [Indexed: 12/30/2022] Open
Abstract
Skeletal muscle myofibers are large and elongated cells with multiple and evenly distributed nuclei. Nuclear distribution suggests that each nucleus influences a specific compartment within the myofiber and implies a functional role for nuclear positioning. Compartmentalization of specific mRNAs and proteins has been reported at the neuromuscular and myotendinous junctions, but mRNA distribution in non-specialized regions of the myofibers remains largely unexplored. We report that the bulk of mRNAs are enriched around the nucleus of origin and that this perinuclear accumulation depends on recently transcribed mRNAs. Surprisingly, mRNAs encoding large proteins - giant mRNAs - are spread throughout the cell and do not exhibit perinuclear accumulation. Furthermore, by expressing exogenous transcripts with different sizes we found that size contributes to mRNA spreading independently of mRNA sequence. Both these mRNA distribution patterns depend on microtubules and are independent of nuclear dispersion, mRNA expression level and stability, and the characteristics of the encoded protein. Thus, we propose that mRNA distribution in non-specialized regions of skeletal muscle is size selective to ensure cellular compartmentalization and simultaneous long-range distribution of giant mRNAs.
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Affiliation(s)
- Helena Pinheiro
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Mafalda Ramos Pimentel
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Catarina Sequeira
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Luís Manuel Oliveira
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Anna Pezzarossa
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - William Roman
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
- Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Edgar R. Gomes
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa. Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
- Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
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5
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Bhadra P, Schorr S, Lerner M, Nguyen D, Dudek J, Förster F, Helms V, Lang S, Zimmermann R. Quantitative Proteomics and Differential Protein Abundance Analysis after Depletion of Putative mRNA Receptors in the ER Membrane of Human Cells Identifies Novel Aspects of mRNA Targeting to the ER. Molecules 2021; 26:3591. [PMID: 34208277 PMCID: PMC8230838 DOI: 10.3390/molecules26123591] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/07/2021] [Accepted: 06/09/2021] [Indexed: 11/28/2022] Open
Abstract
In human cells, one-third of all polypeptides enter the secretory pathway at the endoplasmic reticulum (ER). The specificity and efficiency of this process are guaranteed by targeting of mRNAs and/or polypeptides to the ER membrane. Cytosolic SRP and its receptor in the ER membrane facilitate the cotranslational targeting of most ribosome-nascent precursor polypeptide chain (RNC) complexes together with the respective mRNAs to the Sec61 complex in the ER membrane. Alternatively, fully synthesized precursor polypeptides are targeted to the ER membrane post-translationally by either the TRC, SND, or PEX19/3 pathway. Furthermore, there is targeting of mRNAs to the ER membrane, which does not involve SRP but involves mRNA- or RNC-binding proteins on the ER surface, such as RRBP1 or KTN1. Traditionally, the targeting reactions were studied in cell-free or cellular assays, which focus on a single precursor polypeptide and allow the conclusion of whether a certain precursor can use a certain pathway. Recently, cellular approaches such as proximity-based ribosome profiling or quantitative proteomics were employed to address the question of which precursors use certain pathways under physiological conditions. Here, we combined siRNA-mediated depletion of putative mRNA receptors in HeLa cells with label-free quantitative proteomics and differential protein abundance analysis to characterize RRBP1- or KTN1-involving precursors and to identify possible genetic interactions between the various targeting pathways. Furthermore, we discuss the possible implications on the so-called TIGER domains and critically discuss the pros and cons of this experimental approach.
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Affiliation(s)
- Pratiti Bhadra
- Center for Bioinformatics, Saarland Informatics Campus, Saarland University, 66041 Saarbrücken, Germany; (P.B.); (D.N.); (V.H.)
| | - Stefan Schorr
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.S.); (M.L.); (J.D.); (S.L.)
| | - Monika Lerner
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.S.); (M.L.); (J.D.); (S.L.)
| | - Duy Nguyen
- Center for Bioinformatics, Saarland Informatics Campus, Saarland University, 66041 Saarbrücken, Germany; (P.B.); (D.N.); (V.H.)
| | - Johanna Dudek
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.S.); (M.L.); (J.D.); (S.L.)
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands;
| | - Volkhard Helms
- Center for Bioinformatics, Saarland Informatics Campus, Saarland University, 66041 Saarbrücken, Germany; (P.B.); (D.N.); (V.H.)
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.S.); (M.L.); (J.D.); (S.L.)
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.S.); (M.L.); (J.D.); (S.L.)
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6
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Lv SW, Shi ZG, Wang XH, Zheng PY, Li HB, Han QJ, Li ZJ. Ribosome Binding Protein 1 Correlates with Prognosis and Cell Proliferation in Bladder Cancer. Onco Targets Ther 2020; 13:6699-6707. [PMID: 32764960 PMCID: PMC7367924 DOI: 10.2147/ott.s252043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 05/13/2020] [Indexed: 12/14/2022] Open
Abstract
Introduction Ribosome binding protein 1 (RRBP1) is reported to be correlated with tumor formation and progression. However, the role of RRBP1 in bladder cancer is unclear. In this study, we aimed to investigate the expression of RRBP1 and its influence on cell proliferation in bladder cancer. Methods Quantification real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) were used to detect the expression levels of RRBP1 in 138 bladder cancer and matched adjacent normal bladder tissues. Then, the clinical significance of RRBP1 in bladder cancer was evaluated. The effect of RRBP1 on cell proliferation and its potential mechanism were further explored. Results Results show that the mRNA levels of RRBP1 in bladder cancer were significantly higher compared with those in normal tissues (P< 0.001). IHC results show the high-expression rate of RRBP1 in bladder cancer was 68.8%, which was significantly greater than those in normal tissues (40.6%, P< 0.001). RRBP1 high-expression was significantly associated with differentiation, T stage and lymph node metastasis in bladder cancer (P< 0.05). The overall survival time of patients with RRBP1 high-expression was significantly reduced compared to those with RRBP1 low-expression. Moreover, RRBP1 overexpression significantly promoted cell proliferation, which was correlated with Smad1/Smad3/TGF-β1 signal pathway. Conclusion RRBP1 high-expression correlates with prognosis and promotes cell proliferation in bladder cancer, which could be a potential biomarker.
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Affiliation(s)
- Shuang-Wu Lv
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Zhen-Guo Shi
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Xiao-Hui Wang
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Peng-Yi Zheng
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Hui-Bing Li
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Qing-Jiang Han
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
| | - Zhi-Jun Li
- The First Affiliated Hospital and College of Clinical Medicineof Henan University of Science and Technology, Luoyang, Henan 471003, People's Republic of China
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7
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Sébastien M, Aubin P, Brocard J, Brocard J, Marty I, Fauré J. Dynamics of triadin, a muscle-specific triad protein, within sarcoplasmic reticulum subdomains. Mol Biol Cell 2020; 31:261-272. [PMID: 31877066 PMCID: PMC7183767 DOI: 10.1091/mbc.e19-07-0399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
In skeletal muscle, proteins of the calcium release complex responsible for the excitation-contraction (EC) coupling are exclusively localized in specific reticulum–plasma membrane (ER-PM) contact points named triads. The CRC protein triadin (T95) is localized in the sarcoplasmic reticulum (SR) subdomain of triads where it forms large multimers. However, the mechanisms leading to the steady-state accumulation of T95 in these specific areas of SR are largely unknown. To visualize T95 dynamics, fluorescent chimeras were expressed in triadin knockout myotubes, and their mobility was compared with the mobility of Sec61β, a membrane protein of the SR unrelated to the EC coupling process. At all stages of skeletal muscle cells differentiation, we show a permanent flux of T95 diffusing in the SR membrane. Moreover, we find evidence that a longer residence time in the ER-PM contact point is due to the transmembrane domain of T95 resulting in an overall triad localization.
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Affiliation(s)
- Muriel Sébastien
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
| | - Perrine Aubin
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
| | - Jacques Brocard
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
| | - Julie Brocard
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
| | - Isabelle Marty
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
| | - Julien Fauré
- Grenoble Institut Neurosciences, Inserm, U1216, University Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France.,Grenoble Institut Neurosciences, Inserm, U1216, CHU Grenoble Alpes, University Grenoble Alpes, 38000 Grenoble, France
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8
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Abstract
In eukaryotes, most mRNAs that encode secretory or membrane-bound proteins are translated by ribosomes associated with the surface of the endoplasmic reticulum (ER). Other such mRNAs are tethered to the ER by mRNA receptors. However, there has been much debate as to whether all mRNAs, regardless of their encoded polypeptide, are anchored to the ER at some low level. Here we describe a protocol to visualize ER-associated mRNAs in tissue culture cells by single-molecule fluorescence in situ hybridization (smFISH). Using this protocol, we have established that a subset of all mRNAs, regardless of whether they encode secretory or cytosolic proteins, are ER associated in a ribosome-dependent manner.
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Affiliation(s)
- Jingze J Wu
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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9
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Xu Y, Mak HY, Lukmantara I, Li YE, Hoehn KL, Huang X, Du X, Yang H. CDP-DAG synthase 1 and 2 regulate lipid droplet growth through distinct mechanisms. J Biol Chem 2019; 294:16740-16755. [PMID: 31548309 DOI: 10.1074/jbc.ra119.009992] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 08/17/2019] [Indexed: 12/25/2022] Open
Abstract
Lipid droplets (LDs) are evolutionarily conserved organelles that play critical roles in mammalian lipid storage and metabolism. However, the molecular mechanisms governing the biogenesis and growth of LDs remain poorly understood. Phosphatidic acid (PA) is a precursor of phospholipids and triacylglycerols and substrate of CDP-diacylglycerol (CDP-DAG) synthase 1 (CDS1) and CDS2, which catalyze the formation of CDP-DAG. Here, using siRNA-based gene knockdowns and CRISPR/Cas9-mediated gene knockouts, along with immunological, molecular, and fluorescence microscopy approaches, we examined the role of CDS1 and CDS2 in LD biogenesis and growth. Knockdown of either CDS1 or CDS2 expression resulted in the formation of giant or supersized LDs in cultured mammalian cells. Interestingly, down-regulation of cell death-inducing DFF45-like effector C (CIDEC), encoding a prominent regulator of LD growth in adipocytes, restored LD size in CDS1- but not in CDS2-deficient cells. On the other hand, reducing expression of two enzymes responsible for triacylglycerol synthesis, diacylglycerol O-acyltransferase 2 (DGAT2) and glycerol-3-phosphate acyltransferase 4 (GPAT4), rescued the LD phenotype in CDS2-deficient, but not CDS1-deficient, cells. Moreover, CDS2 deficiency, but not CDS1 deficiency, promoted the LD association of DGAT2 and GPAT4 and impaired initial LD maturation. Finally, although both CDS1 and CDS2 appeared to regulate PA levels on the LD surface, CDS2 had a stronger effect. We conclude that CDS1 and CDS2 regulate LD dynamics through distinct mechanisms.
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Affiliation(s)
- Yanqing Xu
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Hoi Yin Mak
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Ivan Lukmantara
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Yang E Li
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Kyle L Hoehn
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100049, China
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales 2052, Australia
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10
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Voigt F, Zhang H, Cui XA, Triebold D, Liu AX, Eglinger J, Lee ES, Chao JA, Palazzo AF. Single-Molecule Quantification of Translation-Dependent Association of mRNAs with the Endoplasmic Reticulum. Cell Rep 2019; 21:3740-3753. [PMID: 29281824 DOI: 10.1016/j.celrep.2017.12.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 09/29/2017] [Accepted: 12/04/2017] [Indexed: 10/25/2022] Open
Abstract
It is well established that mRNAs encoding secretory or membrane-bound proteins are translated on the surface of the endoplasmic reticulum (ER). The extent to which mRNAs that encode cytosolic proteins associate with the ER, however, remains controversial. To address this question, we quantified the number of cytosolic protein-encoding mRNAs that co-localize with the ER using single-molecule RNA imaging in fixed and living cells. We found that a small but significant number of mRNAs that encode cytosolic proteins associate with the ER and show that this interaction is translation dependent. Furthermore, we demonstrate that cytosolic protein-encoding transcripts can remain on the ER with dwell times consistent with multiple rounds of translation and have higher ribosome occupancies than transcripts translated in the cytosol. These results advance our understanding of the diversity and dynamics of localized translation on the ER.
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Affiliation(s)
- Franka Voigt
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Hui Zhang
- Department of Biochemistry, University of Toronto, 1 King's College Circle, MSB Room 5336, Toronto, ON M5S 1A8, Canada
| | - Xianying A Cui
- Department of Biochemistry, University of Toronto, 1 King's College Circle, MSB Room 5336, Toronto, ON M5S 1A8, Canada
| | - Désirée Triebold
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland; University of Basel, 4003 Basel, Switzerland
| | - Ai Xin Liu
- Department of Biochemistry, University of Toronto, 1 King's College Circle, MSB Room 5336, Toronto, ON M5S 1A8, Canada
| | - Jan Eglinger
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Eliza S Lee
- Department of Biochemistry, University of Toronto, 1 King's College Circle, MSB Room 5336, Toronto, ON M5S 1A8, Canada
| | - Jeffrey A Chao
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland.
| | - Alexander F Palazzo
- Department of Biochemistry, University of Toronto, 1 King's College Circle, MSB Room 5336, Toronto, ON M5S 1A8, Canada.
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11
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Figueiredo Costa B, Cassella P, Colombo SF, Borgese N. Discrimination between the endoplasmic reticulum and mitochondria by spontaneously inserting tail‐anchored proteins. Traffic 2018; 19:182-197. [DOI: 10.1111/tra.12550] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 01/18/2018] [Accepted: 01/18/2018] [Indexed: 01/16/2023]
Affiliation(s)
- Bruna Figueiredo Costa
- CNR Institute of Neuroscience and BIOMETRA DepartmentUniversità degli Studi di Milano Milan Italy
| | - Patrizia Cassella
- CNR Institute of Neuroscience and BIOMETRA DepartmentUniversità degli Studi di Milano Milan Italy
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12
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Nesprin-2 Interacts with Condensin Component SMC2. Int J Cell Biol 2018; 2017:8607532. [PMID: 29445399 PMCID: PMC5763115 DOI: 10.1155/2017/8607532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 11/17/2017] [Accepted: 12/07/2017] [Indexed: 01/24/2023] Open
Abstract
The nuclear envelope proteins, Nesprins, have been primarily studied during interphase where they function in maintaining nuclear shape, size, and positioning. We analyze here the function of Nesprin-2 in chromatin interactions in interphase and dividing cells. We characterize a region in the rod domain of Nesprin-2 that is predicted as SMC domain (aa 1436-1766). We show that this domain can interact with itself. It furthermore has the capacity to bind to SMC2 and SMC4, the core subunits of condensin. The interaction was observed during all phases of the cell cycle; it was particularly strong during S phase and persisted also during mitosis. Nesprin-2 knockdown did not affect condensin distribution; however we noticed significantly higher numbers of chromatin bridges in Nesprin-2 knockdown cells in anaphase. Thus, Nesprin-2 may have an impact on chromosomes which might be due to its interaction with condensins or to indirect mechanisms provided by its interactions at the nuclear envelope.
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Kejiou NS, Palazzo AF. mRNA localization as a rheostat to regulate subcellular gene expression. WILEY INTERDISCIPLINARY REVIEWS-RNA 2017; 8. [DOI: 10.1002/wrna.1416] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/20/2016] [Accepted: 12/21/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Nevraj S. Kejiou
- Department of Biochemistry; University of Toronto; Toronto Canada
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