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Yang S, Zhuo Y, Lin Y, Huang M, Tang W, Zheng W, Lu G, Wang Z, Yun Y. The Signal Peptidase FoSpc2 Is Required for Normal Growth, Conidiation, Virulence, Stress Response, and Regulation of Light Sensitivity in Fusarium odoratissimum. Microbiol Spectr 2023; 11:e0440322. [PMID: 37367437 PMCID: PMC10433827 DOI: 10.1128/spectrum.04403-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 06/05/2023] [Indexed: 06/28/2023] Open
Abstract
Signal peptidase (SPase) is responsible for cleavage of N-terminal signal peptides in most secretory precursor proteins and many membrane proteins during maturation. In this study, we identified four components of the SPase complex (FoSec11, FoSpc1, FoSpc2, and FoSpc3) in the banana wilt fungal pathogen Fusarium odoratissimum. We proved that interactions exist among the four SPase subunits by bimolecular fluorescence complementation (BiFC) and affinity purification and mass spectrometry (AP-MS) assays. Among the four SPase genes, FoSPC2 was successfully deleted. FoSPC2 deletion caused defects in vegetative growth, conidiation, and virulence. Loss of FoSPC2 also affected the secretion of some pathogenicity-related extracellular enzymes, suggesting that SPase without FoSpc2 may have a lower efficiency in managing the maturation of the extracellular enzymes in F. odoratissimum. In addition, we found that the ΔFoSPC2 mutant had increased sensitivity to light, and the colonies of the mutant grew faster under all-dark conditions than under all-light conditions. We further observed that deletion of FoSPC2 affected expression of the blue light photoreceptor gene FoWC2, leading to cytoplasmic accumulation of FoWc2 under all-light conditions. Since FoWc2 has signal peptides, FoSpc2 may regulate the expression and subcellular localization of FoWc2 indirectly. Contrary to its response to light, the ΔFoSPC2 mutant displayed a significant decreased sensitivity to osmotic stress, and culturing the mutant under osmotic stress conditions restored both the localization of FoWc2 and light sensitivity of the ΔFoSPC2, suggesting that a cross talk between osmotic stress and light response pathways in F. odoratissimum and FoSpc2 takes part in these processes. IMPORTANCE In this study, we identified four components of SPase in the banana wilt pathogen Fusarium odoratissimum and characterized the SPase FoSpc2. Loss of FoSPC2 affected the secretion of extracellular enzymes, suggesting that SPase without FoSpc2 may have a lower efficiency in managing the maturation of the extracellular enzymes in F. odoratissimum. In addition, this is the first time that we have found a relationship between the SPase and fungal light response. Deletion of FoSPC2 resulted in decreased sensitivity to the osmotic stresses but with increased sensitivity to light. Continuous light inhibited the growth rate of the ΔFoSPC2 mutant and affected the cellular localization of the blue light photoreceptor FoWc2 in this mutant, but culturing the mutant under osmotic stress both restored the localization of FoWc2 and eliminated the light sensitivity of the ΔFoSPC2 mutant, suggesting that loss of FoSPC2 may affect a cross talk between the osmotic stress and light response pathways in F. odoratissimum.
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Affiliation(s)
- Shuai Yang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yanghong Zhuo
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yaqi Lin
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Meimei Huang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wei Tang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wenhui Zheng
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guodong Lu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
| | - Yingzi Yun
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian Key Laboratory for Monitoring and Integrated Management of Crop Pests, Fuzhou, China
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2
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Yang WB, Luo F, Zhang W, Sun CS, Tan C, Zhou A, Hu W. Inhibition of signal peptidase complex expression affects the development and survival of Schistosoma japonicum. Front Cell Infect Microbiol 2023; 13:1136056. [PMID: 36936776 PMCID: PMC10020623 DOI: 10.3389/fcimb.2023.1136056] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 02/20/2023] [Indexed: 03/06/2023] Open
Abstract
Background Schistosomiasis, the second most neglected tropical disease defined by the WHO, is a significant zoonotic parasitic disease infecting approximately 250 million people globally. This debilitating disease has seriously threatened public health, while only one drug, praziquantel, is used to control it. Because of this, it highlights the significance of identifying more satisfactory target genes for drug development. Protein translocation into the endoplasmic reticulum (ER) is vital to the subsequent localization of secretory and transmembrane proteins. The signal peptidase complex (SPC) is an essential component of the translocation machinery and functions to cleave the signal peptide sequence (SP) of secretory and membrane proteins entering the ER. Inhibiting the expression of SPC can lead to the abolishment or weaker cleavage of the signal peptide, and the accumulation of uncleaved protein in the ER would affect the survival of organisms. Despite the evident importance of SPC, in vivo studies exploring its function have yet to be reported in S. japonicum. Methods The S. japonicum SPC consists of four proteins: SPC12, SPC18, SPC22 and SPC25. RNA interference was used to investigate the impact of SPC components on schistosome growth and development in vivo. qPCR and in situ hybridization were applied to localize the SPC25 expression. Mayer's carmalum and Fast Blue B staining were used to observe morphological changes in the reproductive organs of dsRNA-treated worms. The effect of inhibitor treatment on the worm's viability and pairing was also examined in vitro. Results Our results showed that RNAi-SPC delayed the worm's normal development and was even lethal for schistosomula in vivo. Among them, the expression of SPC25 was significantly higher in the developmental stages of the reproductive organs in schistosomes. Moreover, SPC25 possessed high expression in the worm tegument, testes of male worms and the ovaries and vitellarium of female worms. The SPC25 knockdown led to the degeneration of reproductive organs, such as the ovaries and vitellarium of female worms. The SPC25 exhaustion also reduced egg production while reducing the pathological damage of the eggs to the host. Additionally, the SPC-related inhibitor AEBSF or suppressing the expression of SPC25 also impacted cultured worms' pairing and viability in vitro. Conclusions These data demonstrate that SPC is necessary to maintain the development and reproduction of S. japonicum. This research provides a promising anti-schistosomiasis drug target and discovers a new perspective on preventing worm fecundity and maturation.
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Affiliation(s)
- Wen-Bin Yang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- The State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, College of Life Sciences, Inner Mongolia University, Hohhot, China
| | - Fang Luo
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Wei Zhang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Cheng-Song Sun
- Central Laboratory, Anhui Provincial Institute of Parasitic Diseases, Anhui, China
| | - Cong Tan
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- The State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, College of Life Sciences, Inner Mongolia University, Hohhot, China
| | - An Zhou
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Wei Hu
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Human Phenome Institute, Fudan University, Shanghai, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- The State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, College of Life Sciences, Inner Mongolia University, Hohhot, China
- *Correspondence: Wei Hu,
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3
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Kim KH, Kang S, Seo H, Yun CW. AfSec1 is a signal peptidase and removes signal peptides of 1,3-β-glucanosyltransferases in Aspergillus fumigatus. Med Mycol 2022; 61:6993075. [PMID: 36657388 DOI: 10.1093/mmy/myad005] [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: 09/28/2022] [Revised: 01/11/2023] [Accepted: 01/18/2023] [Indexed: 01/20/2023] Open
Abstract
To identify the infection mechanism of Aspergillus fumigatus, which is an opportunistic fungal pathogen, we analyzed the expression profile of the whole genome of A. fumigatus during the infection of murine macrophages. A previously reported RNA-seq data analysis showed that many genes involved in cell wall synthesis were upregulated during the infection process. Interestingly, AfSec1 (3g12840), which encodes a putative signal peptidase, was upregulated dramatically, and its putative target protein Gel1, which encodes a 1,3-β-glucanosyltransferase, was also upregulated. Instead of the AfSec1 deletion strain, the AfSec1-ΔP strain was constructed, in which the promoter region of AfSec1 was deleted, and AfSec1 expression was not detected in the AfSec1-ΔP strain. The expression of AfSec1 was recovered by the introduction of the promoter region (the AfSec1-ΔP/P strain). The nonprocessed form of Gel1 was identified in the AfSec1-ΔP strain, which lacked the promoter, but mature forms of Gel1 were found in the wild-type and in AfSec1-ΔP/P, which was the promoter complementation strain. In the plate assay, the AfSec1-ΔP strain showed higher sensitivity against caspofungin than the wild-type. However, compared with the wild-type, the deletion strain showed no difference in the sensitivity to other antifungal drugs, such as amphotericin B and voriconazole, which inhibit different targets compared with caspofungin. The AfSec1-ΔP strain exhibited ∼20% lower levels of β-glucan in the cell wall than the wild-type. Finally, the virulence decreased when the promoter region of AfSec1 was deleted, as observed in the murine infection test and conidia-killing assay using human macrophages and neutrophils. These results suggest that AfSec1 exerts signal peptidase activity on its target Gel1 and has an important role in fungal pathogenesis.
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Affiliation(s)
- Ki-Hwan Kim
- School of Life Sciences and Biotechnology, Korea University Anam-dong, Sungbuk-gu, Seoul, Republic of Korea
| | - Suzie Kang
- School of Life Sciences and Biotechnology, Korea University Anam-dong, Sungbuk-gu, Seoul, Republic of Korea
| | - Hyewon Seo
- School of Life Sciences and Biotechnology, Korea University Anam-dong, Sungbuk-gu, Seoul, Republic of Korea
| | - Cheol-Won Yun
- School of Life Sciences and Biotechnology, Korea University Anam-dong, Sungbuk-gu, Seoul, Republic of Korea.,NeuroEsgel Co., Anam-dong, Sungbuk-gu, Seoul, 02841, Korea
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4
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Alzahrani N, Wu MJ, Sousa CF, Kalinina OV, Welsch C, Yi M. SPCS1-Dependent E2-p7 processing determines HCV Assembly efficiency. PLoS Pathog 2022; 18:e1010310. [PMID: 35130329 PMCID: PMC8853643 DOI: 10.1371/journal.ppat.1010310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 02/17/2022] [Accepted: 01/26/2022] [Indexed: 11/18/2022] Open
Abstract
Recent studies identified signal peptidase complex subunit 1 (SPCS1) as a proviral host factor for Flaviviridae viruses, including HCV. One of the SPCS1’s roles in flavivirus propagation was attributed to its regulation of signal peptidase complex (SPC)-mediated processing of flavivirus polyprotein, especially C-prM junction. However, whether SPCS1 also regulates any SPC-mediated processing sites within HCV polyprotein remains unclear. In this study, we determined that loss of SPCS1 specifically impairs the HCV E2-p7 processing by the SPC. We also determined that efficient separation of E2 and p7, regardless of its dependence on SPC-mediated processing, leads to SPCS1 dispensable for HCV assembly These results suggest that SPCS1 regulates HCV assembly by facilitating the SPC-mediated processing of E2-p7 precursor. Structural modeling suggests that intrinsically delayed processing of the E2-p7 is likely caused by the structural rigidity of p7 N-terminal transmembrane helix-1 (p7/TM1/helix-1), which has mostly maintained membrane-embedded conformations during molecular dynamics (MD) simulations. E2-p7-processing-impairing p7 mutations narrowed the p7/TM1/helix-1 bending angle against the membrane, resulting in closer membrane embedment of the p7/TM1/helix-1 and less access of E2-p7 junction substrate to the catalytic site of the SPC, located well above the membrane in the ER lumen. Based on these results we propose that the key mechanism of action of SPCS1 in HCV assembly is to facilitate the E2-p7 processing by enhancing the E2-p7 junction site presentation to the SPC active site. By providing evidence that SPCS1 facilitates HCV assembly by regulating SPC-mediated cleavage of E2-p7 junction, equivalent to the previously established role of this protein in C-prM junction processing in flavivirus, this study establishes the common role of SPCS1 in Flaviviridae family virus propagation as to exquisitely regulate the SPC-mediated processing of specific, suboptimal target sites.
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Affiliation(s)
- Nabeel Alzahrani
- Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Ming-Jhan Wu
- Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Carla F. Sousa
- Drug Bioinformatics Group, HIPS, HZI, Saarbrücken, Germany
| | - Olga V. Kalinina
- Drug Bioinformatics Group, HIPS, HZI, Saarbrücken, Germany
- Medical Faculty, Saarland University, Homburg, Germany
| | - Christoph Welsch
- Department of Internal Medicine 1, Goethe University Hospital, Frankfurt am Main, Germany
| | - MinKyung Yi
- Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail:
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5
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Liaci AM, Steigenberger B, Telles de Souza PC, Tamara S, Gröllers-Mulderij M, Ogrissek P, Marrink SJ, Scheltema RA, Förster F. Structure of the human signal peptidase complex reveals the determinants for signal peptide cleavage. Mol Cell 2021; 81:3934-3948.e11. [PMID: 34388369 DOI: 10.1016/j.molcel.2021.07.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 06/02/2021] [Accepted: 07/26/2021] [Indexed: 12/18/2022]
Abstract
The signal peptidase complex (SPC) is an essential membrane complex in the endoplasmic reticulum (ER), where it removes signal peptides (SPs) from a large variety of secretory pre-proteins with exquisite specificity. Although the determinants of this process have been established empirically, the molecular details of SP recognition and removal remain elusive. Here, we show that the human SPC exists in two functional paralogs with distinct proteolytic subunits. We determined the atomic structures of both paralogs using electron cryo-microscopy and structural proteomics. The active site is formed by a catalytic triad and abuts the ER membrane, where a transmembrane window collectively formed by all subunits locally thins the bilayer. Molecular dynamics simulations indicate that this unique architecture generates specificity for SPs based on the length of their hydrophobic segments.
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Affiliation(s)
- A Manuel Liaci
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, the Netherlands
| | - Barbara Steigenberger
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, the Netherlands
| | - Paulo Cesar Telles de Souza
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Material, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, the Netherlands; Molecular Microbiology and Structural Biochemistry, UMR 5086, CNRS and University of Lyon, Lyon, France
| | - Sem Tamara
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, the Netherlands
| | - Mariska Gröllers-Mulderij
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, the Netherlands
| | - Patrick Ogrissek
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, the Netherlands; Institute of Chemistry and Metabolomics, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Material, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, the Netherlands
| | - Richard A Scheltema
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, the Netherlands
| | - Friedrich Förster
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, the Netherlands.
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6
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Yim C, Chung Y, Kim J, Nilsson I, Kim JS, Kim H. Spc1 regulates the signal peptidase-mediated processing of membrane proteins. J Cell Sci 2021; 134:269144. [PMID: 34125229 PMCID: PMC8277137 DOI: 10.1242/jcs.258936] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 06/01/2021] [Indexed: 11/20/2022] Open
Abstract
Signal peptidase (SPase) cleaves the signal sequences (SSs) of secretory precursors. It contains an evolutionarily conserved membrane protein subunit, Spc1, that is dispensable for the catalytic activity of SPase and whose role remains unknown. In this study, we investigated the function of yeast Spc1. First, we set up an in vivo SPase cleavage assay using variants of the secretory protein carboxypeptidase Y (CPY) with SSs modified in the N-terminal and hydrophobic core regions. When comparing the SS cleavage efficiencies of these variants in cells with or without Spc1, we found that signal-anchored sequences became more susceptible to cleavage by SPase without Spc1. Furthermore, SPase-mediated processing of model membrane proteins was enhanced in the absence of Spc1 and was reduced upon overexpression of Spc1. Spc1 co-immunoprecipitated with proteins carrying uncleaved signal-anchored or transmembrane (TM) segments. Taken together, these results suggest that Spc1 protects TM segments from SPase action, thereby sharpening SPase substrate selection and acting as a negative regulator of the SPase-mediated processing of membrane proteins.
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Affiliation(s)
- Chewon Yim
- School of Biological Sciences and Institute of Microbiology , Seoul National University, Seoul 08826, South Korea
| | - Yeonji Chung
- School of Biological Sciences and Institute of Microbiology , Seoul National University, Seoul 08826, South Korea
| | - Jeesoo Kim
- School of Biological Sciences and Institute of Microbiology , Seoul National University, Seoul 08826, South Korea.,Center for RNA Research , Institute for Basic Science, Seoul 08826, South Korea
| | - IngMarie Nilsson
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Jong-Seo Kim
- School of Biological Sciences and Institute of Microbiology , Seoul National University, Seoul 08826, South Korea.,Center for RNA Research , Institute for Basic Science, Seoul 08826, South Korea
| | - Hyun Kim
- School of Biological Sciences and Institute of Microbiology , Seoul National University, Seoul 08826, South Korea
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7
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Hosomi A, Iida K, Cho T, Iida H, Kaneko M, Suzuki T. The ER-associated protease Ste24 prevents N-terminal signal peptide-independent translocation into the endoplasmic reticulum in Saccharomyces cerevisiae. J Biol Chem 2020; 295:10406-10419. [PMID: 32513868 DOI: 10.1074/jbc.ra120.012575] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 06/03/2020] [Indexed: 12/14/2022] Open
Abstract
Soluble proteins destined for the secretory pathway contain an N-terminal signal peptide that induces their translocation into the endoplasmic reticulum (ER). The importance of N-terminal signal peptides for ER translocation has been extensively examined over the past few decades. However, in the budding yeast Saccharomyces cerevisiae, a few proteins devoid of a signal peptide are still translocated into the ER and then N-glycosyl-ated. Using signal peptide-truncated reporter proteins, here we report the detection of significant translocation of N-terminal signal peptide-truncated proteins in a yeast mutant strain (ste24Δ) that lacks the endopeptidase Ste24 at the ER membrane. Furthermore, several ER/cytosolic proteins, including Sec61, Sec66, and Sec72, were identified as being involved in the translocation process. On the basis of screening for 20 soluble proteins that may be N-glycosylated in the ER in the ste24Δ strain, we identified the transcription factor Rme1 as a protein that is partially N-glycosylated despite the lack of a signal peptide. These results clearly indicate that some proteins lacking a signal peptide can be translocated into the ER and that Ste24 typically suppresses this process.
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Affiliation(s)
- Akira Hosomi
- Department of Agriculture, Graduate School of Science and Technology, Shinshu University, Kamiina, Nagano, Japan
| | - Kazuko Iida
- Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Toshihiko Cho
- Department of Biology, Tokyo Gakugei University, Koganei, Tokyo, Japan
| | - Hidetoshi Iida
- Department of Biology, Tokyo Gakugei University, Koganei, Tokyo, Japan
| | - Masashi Kaneko
- Department of Agriculture, Graduate School of Science and Technology, Shinshu University, Kamiina, Nagano, Japan
| | - Tadashi Suzuki
- Glycometabolic Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, Japan
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8
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Marapana DS, Dagley LF, Sandow JJ, Nebl T, Triglia T, Pasternak M, Dickerman BK, Crabb BS, Gilson PR, Webb AI, Boddey JA, Cowman AF. Plasmepsin V cleaves malaria effector proteins in a distinct endoplasmic reticulum translocation interactome for export to the erythrocyte. Nat Microbiol 2018; 3:1010-1022. [DOI: 10.1038/s41564-018-0219-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 07/13/2018] [Indexed: 01/10/2023]
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9
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Millership SJ, Da Silva Xavier G, Choudhury AI, Bertazzo S, Chabosseau P, Pedroni SM, Irvine EE, Montoya A, Faull P, Taylor WR, Kerr-Conte J, Pattou F, Ferrer J, Christian M, John RM, Latreille M, Liu M, Rutter GA, Scott J, Withers DJ. Neuronatin regulates pancreatic β cell insulin content and secretion. J Clin Invest 2018; 128:3369-3381. [PMID: 29864031 PMCID: PMC6063487 DOI: 10.1172/jci120115] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 05/17/2018] [Indexed: 02/06/2023] Open
Abstract
Neuronatin (Nnat) is an imprinted gene implicated in human obesity and widely expressed in neuroendocrine and metabolic tissues in a hormone- and nutrient-sensitive manner. However, its molecular and cellular functions and precise role in organismal physiology remain only partly defined. Here we demonstrate that mice lacking Nnat globally or specifically in β cells display impaired glucose-stimulated insulin secretion leading to defective glucose handling under conditions of nutrient excess. In contrast, we report no evidence for any feeding or body weight phenotypes in global Nnat-null mice. At the molecular level neuronatin augments insulin signal peptide cleavage by binding to the signal peptidase complex and facilitates translocation of the nascent preprohormone. Loss of neuronatin expression in β cells therefore reduces insulin content and blunts glucose-stimulated insulin secretion. Nnat expression, in turn, is glucose-regulated. This mechanism therefore represents a novel site of nutrient-sensitive control of β cell function and whole-animal glucose homeostasis. These data also suggest a potential wider role for Nnat in the regulation of metabolism through the modulation of peptide processing events.
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Affiliation(s)
- Steven J. Millership
- MRC London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Gabriela Da Silva Xavier
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | | | - Sergio Bertazzo
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Pauline Chabosseau
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Silvia M.A. Pedroni
- MRC London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Elaine E. Irvine
- MRC London Institute of Medical Sciences, London, United Kingdom
| | - Alex Montoya
- MRC London Institute of Medical Sciences, London, United Kingdom
| | - Peter Faull
- MRC London Institute of Medical Sciences, London, United Kingdom
| | - William R. Taylor
- Computational Cell and Molecular Biology Laboratory, Francis Crick Institute, London, United Kingdom
| | - Julie Kerr-Conte
- European Genomic Institute for Diabetes, UMR 1190 Translational Research for Diabetes, INSERM, CHU Lille, University of Lille, Lille, France
| | - Francois Pattou
- European Genomic Institute for Diabetes, UMR 1190 Translational Research for Diabetes, INSERM, CHU Lille, University of Lille, Lille, France
| | - Jorge Ferrer
- Beta Cell Genome Regulation Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Mark Christian
- Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, London, United Kingdom
| | - Rosalind M. John
- School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | | | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - James Scott
- National Heart and Lung Institute, Department of Medicine, Imperial College London, London, United Kingdom
| | - Dominic J. Withers
- MRC London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
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10
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Guan J, Zhang J, Yuan S, Yang B, Clark KD, Ling E, Huang W. Analysis of the functions of the signal peptidase complex in the midgut of Tribolium castaneum. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2018; 97:e21441. [PMID: 29265467 DOI: 10.1002/arch.21441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Signal peptidase complexes (SPCs) are conserved from bacteria to human beings, and are typically composed of four to five subunits. There are four genes encoding SPC proteins in the red flour beetle, Tribolium castaneum. To understand their importance to insect development, double-stranded RNA for each SPC gene was injected into red flour beetles at the early larval and adult stages. Knockdown of all four signal peptidase genes was lethal to larvae. Moreover, larvae had difficulty with old cuticle ecdysis. Knockdown of TcSPC12 alone did not affect pupal or adult development. When TcSPC12, TcSPC18, and TcSPC25 were knocked down in larvae, the melanization of hemocytes and midguts was observed. When knocked down in larvae and adults, TcSPC18 induced severe cell apoptosis in midguts, and the adult midgut lost the ability to maintain crypts after knockdown of TcSPC18, indicating its importance to midgut cell proliferation and differentiation. Knockdown of TcSPC22 or TcSPC25 also resulted in many apoptotic cells in the midguts. However, TcSPC12 appeared to be unimportant for midgut development. We conclude that TcSPC18 is essential for maintaining the adult midgut crypts.
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Affiliation(s)
- Jingmin Guan
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jie Zhang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Shenglei Yuan
- School of Life Sciences, Shanghai University, Shanghai, China
| | - Bing Yang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Kevin D Clark
- Department of Food Science and Technology, University of Georgia, Athens, GA, USA
| | - Erjun Ling
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Wuren Huang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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11
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Estoppey D, Lee CM, Janoschke M, Lee BH, Wan KF, Dong H, Mathys P, Filipuzzi I, Schuhmann T, Riedl R, Aust T, Galuba O, McAllister G, Russ C, Spiess M, Bouwmeester T, Bonamy GM, Hoepfner D. The Natural Product Cavinafungin Selectively Interferes with Zika and Dengue Virus Replication by Inhibition of the Host Signal Peptidase. Cell Rep 2017; 19:451-460. [DOI: 10.1016/j.celrep.2017.03.071] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 03/06/2017] [Accepted: 03/24/2017] [Indexed: 12/31/2022] Open
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12
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Gowen BG, Chim B, Marceau CD, Greene TT, Burr P, Gonzalez JR, Hesser CR, Dietzen PA, Russell T, Iannello A, Coscoy L, Sentman CL, Carette JE, Muljo SA, Raulet DH. A forward genetic screen reveals novel independent regulators of ULBP1, an activating ligand for natural killer cells. eLife 2015; 4. [PMID: 26565589 PMCID: PMC4629278 DOI: 10.7554/elife.08474] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 08/28/2015] [Indexed: 02/07/2023] Open
Abstract
Recognition and elimination of tumor cells by the immune system is crucial for limiting tumor growth. Natural killer (NK) cells become activated when the receptor NKG2D is engaged by ligands that are frequently upregulated in primary tumors and on cancer cell lines. However, the molecular mechanisms driving NKG2D ligand expression on tumor cells are not well defined. Using a forward genetic screen in a tumor-derived human cell line, we identified several novel factors supporting expression of the NKG2D ligand ULBP1. Our results show stepwise contributions of independent pathways working at multiple stages of ULBP1 biogenesis. Deeper investigation of selected hits from the screen showed that the transcription factor ATF4 drives ULBP1 gene expression in cancer cell lines, while the RNA-binding protein RBM4 supports ULBP1 expression by suppressing a novel alternatively spliced isoform of ULBP1 mRNA. These findings offer insight into the stress pathways that alert the immune system to danger. DOI:http://dx.doi.org/10.7554/eLife.08474.001 Cancer is caused by a series of mutations that result in uncontrolled cell growth and division. Yet, the body's immune system can often detect and destroy abnormal cells before they cause tumors and disease. Natural killer cells are part of the immune system and have receptors on their surface that allow them to tell the difference between healthy host cells and host cells that are stressed or abnormal. Some of these receptors activate the natural killer cells when they bind to their target molecules. Other receptors have the opposite effect and inhibit the natural killer cells. Activation occurs when the signaling from the activating receptors is stronger than the signals from the inhibitory receptors. One of the well-studied activating receptors recognizes a number of proteins and molecules that are produced by abnormal or tumor cells, including a protein called ULBP1. This protein is absent from the surface of healthy cells but is found in abundance on tumor cells. However, it is still not clear what drives tumor cells to produce ULBP1 (or other molecules) that are recognized by natural killer cell receptors. Now, Gowen et al. report on a genetic screen that has revealed numerous genes that regulate the levels of ULBP1 in human cells. Many of these genes had independent effects that when added together accounted for most of the ULBP1 present on the cell surface. Gowen et al. then explored some of the ‘regulators’ encoded by these genes in more detail. One called ATF4, which had previously been linked to stress responses, was shown to increase the expression of the gene for ULBP1 in cancer cells. Another regulator called RBM4 instead acted in a different way and at a later stage in ULBP1 production. All together, these findings offer insight into the stress pathways that alert the immune system to abnormal cells. The next challenge will be investigating how these pathways might be exploited for cancer immunotherapy. DOI:http://dx.doi.org/10.7554/eLife.08474.002
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Affiliation(s)
- Benjamin G Gowen
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Bryan Chim
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - Caleb D Marceau
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Trever T Greene
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Patrick Burr
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - Jeanmarie R Gonzalez
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Charles R Hesser
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Peter A Dietzen
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Teal Russell
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Alexandre Iannello
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Laurent Coscoy
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Charles L Sentman
- Center for Synthetic Immunity, Department of Microbiology and Immunology, Dartmouth Geisel School of Medicine, Lebanon, United States
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Stefan A Muljo
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - David H Raulet
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
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13
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Cui J, Chen W, Sun J, Guo H, Madley R, Xiong Y, Pan X, Wang H, Tai AW, Weiss MA, Arvan P, Liu M. Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos. J Biol Chem 2015; 290:28131-28140. [PMID: 26446786 DOI: 10.1074/jbc.m115.692350] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 12/30/2022] Open
Abstract
Upon translocation across the endoplasmic reticulum (ER) membrane, secretory proteins are proteolytically processed to remove their signal peptide by signal peptidase (SPase). This process is critical for subsequent folding, intracellular trafficking, and maturation of secretory proteins. Prokaryotic SPase has been shown to be a promising antibiotic target. In contrast, to date, no eukaryotic SPase inhibitors have been reported. Here we report that introducing a proline immediately following the natural signal peptide cleavage site not only blocks preprotein cleavage but also, in trans, impairs the processing and maturation of co-expressed preproteins in the ER. Specifically, we find that a variant preproinsulin, pPI-F25P, is translocated across the ER membrane, where it binds to the catalytic SPase subunit SEC11A, inhibiting SPase activity in a dose-dependent manner. Similar findings were obtained with an analogous variant of preproparathyroid hormone, demonstrating that inhibition of the SPase does not depend strictly on the sequence or structure of the downstream mature protein. We further show that inhibiting SPase in the ER impairs intracellular processing of viral polypeptides and their subsequent maturation. These observations suggest that eukaryotic SPases (including the human ortholog) are, in principle, suitable therapeutic targets for antiviral drug design.
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Affiliation(s)
- Jingqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China,; Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Wei Chen
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105,; Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Jinhong Sun
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Huan Guo
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Rachel Madley
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Yi Xiong
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Xingyi Pan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Hongliang Wang
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Andrew W Tai
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106.
| | - Peter Arvan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China,; Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
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14
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Fox RM, Andrew DJ. Transcriptional regulation of secretory capacity by bZip transcription factors. ACTA ACUST UNITED AC 2014; 10:28-51. [PMID: 25821458 PMCID: PMC4374484 DOI: 10.1007/s11515-014-1338-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cells of specialized secretory organs expand their secretory pathways to accommodate the increased protein load necessary for their function. The endoplasmic reticulum (ER), the Golgi apparatus and the secretory vesicles, expand not only the membrane components but also the protein machinery required for increased protein production and transport. Increased protein load causes an ER stress response akin to the Unfolded Protein Response (UPR). Recent work has implicated several bZip transcription factors in the regulation of protein components of the early secretory pathway necessary to alleviate this stress. Here, we highlight eight bZip transcription factors in regulating secretory pathway component genes. These include components of the three canonical branches of the UPR-ATF4, XBP1, and ATF6, as well as the five members of the Creb3 family of transcription factors.We review findings from both invertebrate and vertebrate model systems suggesting that all of these proteins increase secretory capacity in response to increased protein load. Finally, we propose that the Creb3 family of factors may have a dual role in secretory cell differentiation by also regulating the pathways necessary for cell cycle exit during terminal differentiation.
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Affiliation(s)
- Rebecca M Fox
- The Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Deborah J Andrew
- The Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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15
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Suzuki R, Matsuda M, Watashi K, Aizaki H, Matsuura Y, Wakita T, Suzuki T. Signal peptidase complex subunit 1 participates in the assembly of hepatitis C virus through an interaction with E2 and NS2. PLoS Pathog 2013; 9:e1003589. [PMID: 24009510 PMCID: PMC3757040 DOI: 10.1371/journal.ppat.1003589] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 07/19/2013] [Indexed: 12/12/2022] Open
Abstract
Hepatitis C virus (HCV) nonstructural protein 2 (NS2) is a hydrophobic, transmembrane protein that is required not only for NS2-NS3 cleavage, but also for infectious virus production. To identify cellular factors that interact with NS2 and are important for HCV propagation, we screened a human liver cDNA library by split-ubiquitin membrane yeast two-hybrid assay using full-length NS2 as a bait, and identified signal peptidase complex subunit 1 (SPCS1), which is a component of the microsomal signal peptidase complex. Silencing of endogenous SPCS1 resulted in markedly reduced production of infectious HCV, whereas neither processing of structural proteins, cell entry, RNA replication, nor release of virus from the cells was impaired. Propagation of Japanese encephalitis virus was not affected by knockdown of SPCS1, suggesting that SPCS1 does not widely modulate the viral lifecycles of the Flaviviridae family. SPCS1 was found to interact with both NS2 and E2. A complex of NS2, E2, and SPCS1 was formed in cells as demonstrated by co-immunoprecipitation assays. Knockdown of SPCS1 impaired interaction of NS2 with E2. Our findings suggest that SPCS1 plays a key role in the formation of the membrane-associated NS2-E2 complex via its interaction with NS2 and E2, which leads to a coordinating interaction between the structural and non-structural proteins and facilitates the early step of assembly of infectious particles. Viruses hijack host cells and utilize host-derived proteins for viral propagation. In the case of hepatitis C virus (HCV), many host factors have been identified that are required for genome replication; however, only a little is known about cellular proteins that interact with HCV proteins and are important for the viral assembly process. The C-terminal half of nonstructural protein 2 (NS2), and the N-terminal third of NS3, form the NS2-3 protease that cleaves the NS2/3 junction. NS2 also plays a key role in the viral assembly process independently of the protease activity. We performed split-ubiquitin yeast two-hybrid screening and identified signal peptidase complex subunit 1 (SPCS1), which is a subunit of the microsomal signal peptidase complex. In this study, we provide evidence that SPCS1 interacts with both NS2 and E2, resulting in E2-SPCS1-NS2 complex formation, and has a critical role in the assembly of infectious HCV particles. To our knowledge, SPCS1 is the first NS2-interacting cellular factor that is involved in regulation of the HCV lifecycle.
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Affiliation(s)
- Ryosuke Suzuki
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan
- * E-mail: (RS); (TS)
| | - Mami Matsuda
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Koichi Watashi
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Hideki Aizaki
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yoshiharu Matsuura
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Takaji Wakita
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Tetsuro Suzuki
- Department of Infectious Diseases, Hamamatsu University School of Medicine, Shizuoka, Japan
- * E-mail: (RS); (TS)
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16
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Haase Gilbert E, Kwak SJ, Chen R, Mardon G. Drosophila signal peptidase complex member Spase12 is required for development and cell differentiation. PLoS One 2013; 8:e60908. [PMID: 23573290 PMCID: PMC3616019 DOI: 10.1371/journal.pone.0060908] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 03/05/2013] [Indexed: 01/22/2023] Open
Abstract
It is estimated that half of all proteins expressed in eukaryotic cells are transferred across or into at least one cellular membrane to reach their functional location. Protein translocation into the endoplasmic reticulum (ER) is critical to the subsequent localization of secretory and transmembrane proteins. A vital component of the translocation machinery is the signal peptidase complex (SPC) - which is conserved from yeast to mammals – and functions to cleave the signal peptide sequence (SP) of secretory and membrane proteins entering the ER. Failure to cleave the SP, due to mutations that abolish the cleavage site or reduce SPC function, leads to the accumulation of uncleaved proteins in the ER that cannot be properly localized resulting in a wide range of defects depending on the protein(s) affected. Despite the obvious importance of the SPC, in vivo studies investigating its function in a multicellular organism have not been reported. The Drosophila SPC comprises four proteins: Spase18/21, Spase22/23, Spase25 and Spase12. Spc1p, the S. cerevisiae homolog of Spase12, is not required for SPC function or viability; Drosophila spase12 null alleles, however, are embryonic lethal. The data presented herein show that spase12 LOF clones disrupt development of all tissues tested including the eye, wing, leg, and antenna. In the eye, spase12 LOF clones result in a disorganized eye, defective cell differentiation, ectopic interommatidial bristles, and variations in support cell size, shape, number, and distribution. In addition, spase12 mosaic tissue is susceptible to melanotic mass formation suggesting that spase12 LOF activates immune response pathways. Together these data demonstrate that spase12 is an essential gene in Drosophila where it functions to mediate cell differentiation and development. This work represents the first reported in vivo analysis of a SPC component in a multicellular organism.
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Affiliation(s)
- Erin Haase Gilbert
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Su-Jin Kwak
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Rui Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Graeme Mardon
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, United States of America
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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17
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Charlton WL, Harel HYM, Bakhetia M, Hibbard JK, Atkinson HJ, McPherson MJ. Additive effects of plant expressed double-stranded RNAs on root-knot nematode development. Int J Parasitol 2010; 40:855-64. [PMID: 20100489 DOI: 10.1016/j.ijpara.2010.01.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 12/22/2009] [Accepted: 01/04/2010] [Indexed: 10/19/2022]
Abstract
Ectopically expressed double-stranded RNAs (dsRNAs) have recently been shown to suppress parasitic success of Meloidogyne spp. in plants. We have targeted two genes from the root-knot nematode Meloidogyne incognita; a dual oxidase gene implicated in the tyrosine cross-linking of the developing cuticle and a subunit of signal peptidase, a protein complex required for the processing of secreted proteins. While these genes are involved in different aspects of nematode development, the phenotypic consequences of RNA interference (RNAi) were similar with >or=50% reduction in nematode numbers in the roots and retardation of development to the egg-producing saccate females. Expression of processed dsRNA was observed, but no evidence of detectable levels of small interfering RNAs (siRNAs) was found in the transgenic plants. We show, to our knowledge for the first time, that combining expression of these dsRNAs by crossing appropriate Arabidopsis thaliana lines resulted in an additive effect that further reduced nematode numbers and developmental capacity. Combining RNAi target genes has the potential to enhance the efficacy of RNAi and may allow control of different nematode species or genera in the crop of interest.
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Affiliation(s)
- Wayne L Charlton
- Centre for Plant Sciences, University of Leeds, Leeds LS2 9JT, UK
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18
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Kaderbhai NN, Khan T, Kaderbhai MA. An Anti-microbial Peptide Derivative of Flesh Fruit Fly Mimics Secretory Signal Sequence and Inhibits Signal Peptidase-I in the Export Pathway. Int J Pept Res Ther 2008. [DOI: 10.1007/s10989-008-9128-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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19
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Choo KH, Tong JC, Ranganathan S. Modeling Escherichia coli signal peptidase complex with bound substrate: determinants in the mature peptide influencing signal peptide cleavage. BMC Bioinformatics 2008; 9 Suppl 1:S15. [PMID: 18315846 PMCID: PMC2259416 DOI: 10.1186/1471-2105-9-s1-s15] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background Type I signal peptidases (SPases) are essential membrane-bound serine proteases responsible for the cleavage of signal peptides from proteins that are translocated across biological membranes. The crystal structure of SPase in complex with signal peptide has not been solved and their substrate-binding site and binding specificities remain poorly understood. We report here a structure-based model for Escherichia coli DsbA 13–25 in complex with its endogenous type I SPase. Results The bound structure of DsbA 13–25 in complex with its endogenous type I SPase reported here reveals the existence of an extended conformation of the precursor protein with a pronounced backbone twist between positions P3 and P1'. Residues 13–25 of DsbA occupy, and thereby define 13 subsites, S7 to S6', within the SPase substrate-binding site. The newly defined subsites, S1' to S6' play critical roles in the substrate specificities of E. coli SPase. Our results are in accord with available experimental data. Conclusion Collectively, the results of this study provide interesting new insights into the binding conformation of signal peptides and the substrate-binding site of E. coli SPase. This is the first report on the modeling of a precursor protein into the entire SPase binding site. Together with the conserved precursor protein binding conformation, the existing and newly identified substrate binding sites readily explain SPase cleavage fidelity, consistent with existing biochemical results and solution structures of inhibitors in complex with E. coli SPase. Our data suggests that both signal and mature moiety sequences play important roles and should be considered in the development of predictive tools.
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Affiliation(s)
- Khar Heng Choo
- Institute for Infocomm Research, 21 Heng Mui Keng Terrace, Singapore 119613.
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20
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White MA, Clark KM, Grayhack EJ, Dumont ME. Characteristics affecting expression and solubilization of yeast membrane proteins. J Mol Biol 2007; 365:621-36. [PMID: 17078969 PMCID: PMC1839945 DOI: 10.1016/j.jmb.2006.10.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/27/2006] [Accepted: 10/03/2006] [Indexed: 11/26/2022]
Abstract
Biochemical and structural analysis of membrane proteins often critically depends on the ability to overexpress and solubilize them. To identify properties of eukaryotic membrane proteins that may be predictive of successful overexpression, we analyzed expression levels of the genomic complement of over 1000 predicted membrane proteins in a recently completed Saccharomyces cerevisiae protein expression library. We detected statistically significant positive and negative correlations between high membrane protein expression and protein properties such as size, overall hydrophobicity, number of transmembrane helices, and amino acid composition of transmembrane segments. Although expression levels of membrane and soluble proteins exhibited similar negative correlations with overall hydrophobicity, high-level membrane protein expression was positively correlated with the hydrophobicity of predicted transmembrane segments. To further characterize yeast membrane proteins as potential targets for structure determination, we tested the solubility of 122 of the highest expressed yeast membrane proteins in six commonly used detergents. Almost all the proteins tested could be solubilized using a small number of detergents. Solubility in some detergents depended on protein size, number of transmembrane segments, and hydrophobicity of predicted transmembrane segments. These results suggest that bioinformatic approaches may be capable of identifying membrane proteins that are most amenable to overexpression and detergent solubilization for structural and biochemical analyses. Bioinformatic approaches could also be used in the redesign of proteins that are not intrinsically well-adapted to such studies.
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Affiliation(s)
- Michael A. White
- Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642
| | - Kathleen M. Clark
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642
| | - Elizabeth J. Grayhack
- Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642
| | - Mark E. Dumont
- Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642
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21
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Yan A, Lennarz WJ. Two oligosaccharyl transferase complexes exist in yeast and associate with two different translocons. Glycobiology 2005; 15:1407-15. [PMID: 16096345 DOI: 10.1093/glycob/cwj026] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Oligosaccharyl transferase (OT) scans and selectively glycosylates -Asn-X-Thr/Ser-motifs in nascent polypeptide chains in the endoplasmic reticulum (ER). Several groups have reported different results for the composition of this enzyme complex. In this study, using a membrane protein two-hybrid approach, the split-ubiquitin system, we show that except for Ost3p and Ost6p, all of the other subunits of OT exist as dimers or oligomers in the yeast, Saccharomyces cerevisiae. Ost3p and Ost6p behave strikingly similar in a series of genetic and biochemical assays, but clearly do not exist in the same OT complex. This observation, as well as the results in an accompanying study to analyze the composition of OT complex by blue native gel electrophoresis using a series of wild-type and mutant yeast strains strongly suggests that two isoforms of the OT complex exist in the ER, differing only in the presence of Ost3p or Ost6p. Each of these two isoforms of the OT complex specifically interacts with two structurally similar, but functionally different translocon complexes: the Sec61 and the Ssh1 translocon complexes.
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Affiliation(s)
- Aixin Yan
- Department of Biochemistry and Cell Biology and the Institute for Cell and Developmental Biology, State University of New York, Stony Brook, NY 11794-5215, USA
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Miller JP, Lo RS, Ben-Hur A, Desmarais C, Stagljar I, Noble WS, Fields S. Large-scale identification of yeast integral membrane protein interactions. Proc Natl Acad Sci U S A 2005; 102:12123-8. [PMID: 16093310 PMCID: PMC1189342 DOI: 10.1073/pnas.0505482102] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We carried out a large-scale screen to identify interactions between integral membrane proteins of Saccharomyces cerevisiae by using a modified split-ubiquitin technique. Among 705 proteins annotated as integral membrane, we identified 1,985 putative interactions involving 536 proteins. To ascribe confidence levels to the interactions, we used a support vector machine algorithm to classify interactions based on the assay results and protein data derived from the literature. Previously identified and computationally supported interactions were used to train the support vector machine, which identified 131 interactions of highest confidence, 209 of the next highest confidence, 468 of the next highest, and the remaining 1,085 of low confidence. This study provides numerous putative interactions among a class of proteins that have been difficult to analyze on a high-throughput basis by other approaches. The results identify potential previously undescribed components of established biological processes and roles for integral membrane proteins of ascribed functions.
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Affiliation(s)
- John P Miller
- Department of Genome Sciences, Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
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23
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Liang H, Luo W, Green N, Fang H. Cargo sequences are important for Som1p-dependent signal peptide cleavage in yeast mitochondria. J Biol Chem 2004; 279:39396-400. [PMID: 15254042 DOI: 10.1074/jbc.m406915200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The inner membrane protease (IMP) has two catalytic subunits, Imp1p and Imp2p, that exhibit nonoverlapping substrate specificity in mitochondria of the yeast Saccharomyces cerevisiae. The IMP also has at least one noncatalytic subunit, Som1p, which is required to cleave signal peptides from a subset of Imp1p substrates. To understand how Som1p mediates Imp1p substrate specificity, we addressed the possibility that Som1p functions as a molecular chaperone, which binds to specific substrates and directs them to the catalytic site. Our results show that cargo sequences attached to the signal peptide are important for Som1p-dependent presequence cleavage; however, no specific cargo sequence is required. Indeed, we show that a substrate normally destined for Imp2p is cleaved in a Som1p-dependent manner when the substrate is directed to Imp1p. These results argue against the notion that Som1p is a molecular chaperone. Instead, we propose that the cargo of some Imp1p substrates can assume a conformation incompatible with presequence cleavage. Som1p could thus act through Imp1p to improve cleavage efficiency early during substrate maturation.
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Affiliation(s)
- Haobo Liang
- Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363, USA
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24
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Liang H, VanValkenburgh C, Chen X, Mullins C, Van Kaer L, Green N, Fang H. Genetic Complementation in Yeast Reveals Functional Similarities between the Catalytic Subunits of Mammalian Signal Peptidase Complex. J Biol Chem 2003; 278:50932-9. [PMID: 14559916 DOI: 10.1074/jbc.m307542200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type I signal peptidases (SPs) comprise a family of structurally related enzymes that cleave signal peptides from precursor proteins following their transport out of the cytoplasmic space in eukaryotic and prokaryotic cells. One such enzyme, the mitochondrial inner membrane peptidase, has two catalytic subunits, which recognize distinct cleavage site motifs in their signal peptide substrates. The only other known type I SP with two catalytic subunits is the signal peptidase complex (SPC) in the mammalian endoplasmic reticulum. Here, we tested the hypothesis that, as with inner membrane peptidase catalytic subunits, SPC catalytic subunits exhibit nonoverlapping substrate specificity. We constructed two yeast strains without endogenous SP, one expressing canine SPC18 and the other expressing a truncation of canine SPC21 (SPC21 Delta N), which lacks 24 N-terminal residues that prevent expression of SPC21 in yeast. By monitoring a variety of soluble and membrane-bound substrates, we find that, in contrast to the tested hypothesis, SPC catalytic subunits exhibit overlapping substrate specificity. SPC18 and SPC21 Delta N do, however, cleave some substrates with different efficiencies, although no pattern for this behavior could be discerned. In light of the functional similarities between SPC proteins, we developed a membrane protein fragmentation assay to monitor the position of the catalytic sites relative to the surface of the endoplasmic reticulum membrane. Using this assay, our results suggest that the active sites of SPC18 and SPC21 Delta N are located 4-11 A above the membrane surface. These data, thus, support a model that SPC18 and SPC21 are functionally and structurally similar to each other.
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Affiliation(s)
- Haobo Liang
- Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363, USA
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25
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Travers KJ, Patil CK, Weissman JS. Functional genomic approaches to understanding molecular chaperones and stress responses. ADVANCES IN PROTEIN CHEMISTRY 2002; 59:345-90. [PMID: 11868277 DOI: 10.1016/s0065-3233(01)59011-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- K J Travers
- Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, Department of Biochemistry and Biophysics, University of California-San Francisco, San Francisco, California, USA
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26
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Chen X, VanValkenburgh C, Liang H, Fang H, Green N. Signal peptidase and oligosaccharyltransferase interact in a sequential and dependent manner within the endoplasmic reticulum. J Biol Chem 2001; 276:2411-6. [PMID: 11058593 DOI: 10.1074/jbc.m007723200] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We demonstrate that the signal peptides of prepro-alpha-factor and preinvertase must be cleaved before Asn-X-Ser/Thr acceptor tripeptides located near the signal peptides of these precursors can be efficiently glycosylated within the endoplasmic reticulum of the yeast Saccharomyces cerevisiae. The data support a model whereby the interaction of a signal peptide with the membrane prevents an acceptor tripeptide juxtaposed to the signal peptide from accessing the oligosaccharyltransferase active site until the signal peptide is cleaved.
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Affiliation(s)
- X Chen
- Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363, USA
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27
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Antonin W, Meyer HA, Hartmann E. Interactions between Spc2p and other components of the endoplasmic reticulum translocation sites of the yeast Saccharomyces cerevisiae. J Biol Chem 2000; 275:34068-72. [PMID: 10921929 DOI: 10.1074/jbc.m006126200] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In yeast, the endoplasmic reticulum membrane proteins Sec11p and Spc3p are essential for the cleavage of signal peptides of nascent polypeptide chains during their passage through translocation sites. Genetic and biochemical experiments demonstrate that Sec11p and Spc3p are tightly associated with two other proteins, Spc1p and Spc2p, whose functions are largely unknown. Using anti-Spc2p antibodies, we show here that this heterotetrameric complex associates with Sbh1p and Sbh2p, the beta-subunits of the Sec61p complex and the Ssh1p complex, respectively. Depletion of Spc2p decreased the enzymatic activity of the SPC in vitro, led to a loss of Spc1p, and led to a down-regulation of the amount of Sec11p and Spc3p in the endoplasmic reticulum. Moreover, the deletion of Spc2p also decreased the expression level of Sbh2p. These data implicate that Spc2p not only enhances the enzymatic activity of the SPC but also facilitates the interactions between different components of the translocation site.
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Affiliation(s)
- W Antonin
- Abteilung Biochemie II, Zentrum Biochemie und Molekulare Zellbiologie, Universität Göttingen, Heinrich-Düker Weg 12, Göttingen 37073, Germany
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28
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Paetzel M, Dalbey RE, Strynadka NC. The structure and mechanism of bacterial type I signal peptidases. A novel antibiotic target. Pharmacol Ther 2000; 87:27-49. [PMID: 10924740 DOI: 10.1016/s0163-7258(00)00064-4] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Type I signal peptidases are essential membrane-bound serine proteases that function to cleave the amino-terminal signal peptide extension from proteins that are translocated across biological membranes. The bacterial signal peptidases are unique serine proteases that utilize a Ser/Lys catalytic dyad mechanism in place of the classical Ser/His/Asp catalytic triad mechanism. They represent a potential novel antibiotic target at the bacterial membrane surface. This review will discuss the bacterial signal peptidases that have been characterized to date, as well as putative signal peptidase sequences that have been recognized via bacterial genome sequencing. We review the investigations into the mechanism of Escherichia coli and Bacillus subtilis signal peptidase, and discuss the results in light of the recent crystal structure of the E. coli signal peptidase in complex with a beta-lactam-type inhibitor. The proposed conserved structural features of Type I signal peptidases give additional insight into the mechanism of this unique enzyme.
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Affiliation(s)
- M Paetzel
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
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29
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VanValkenburgh C, Chen X, Mullins C, Fang H, Green N. The catalytic mechanism of endoplasmic reticulum signal peptidase appears to be distinct from most eubacterial signal peptidases. J Biol Chem 1999; 274:11519-25. [PMID: 10206957 DOI: 10.1074/jbc.274.17.11519] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many type I signal peptidases from eubacterial cells appear to contain a serine/lysine catalytic dyad. In contrast, our data show that the signal peptidase complex from the endoplasmic reticulum lacks an apparent catalytic lysine. Instead, a serine, histidine, and two aspartic acids are important for signal peptidase activity by the Sec11p subunit of the yeast signal peptidase complex. Amino acids critical to the eubacterial signal peptidases and Sec11p are, however, positioned similarly along their primary sequences, suggesting the presence of a common structural element(s) near the catalytic sites of these enzymes.
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Affiliation(s)
- C VanValkenburgh
- Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363, USA
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30
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Kalies KU, Rapoport TA, Hartmann E. The beta subunit of the Sec61 complex facilitates cotranslational protein transport and interacts with the signal peptidase during translocation. J Cell Biol 1998; 141:887-94. [PMID: 9585408 PMCID: PMC2132780 DOI: 10.1083/jcb.141.4.887] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the beta subunit (Sec61beta) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61beta is essentially inactive when elongation and membrane targeting of a nascent chain occur at the same time. The translocation process is perturbed at a step where the nascent chain would be inserted into the translocation channel. However, if sufficient time is given for the interaction of the nascent polypeptide with the mutant Sec61 complex, translocation is almost normal. Thus Sec61beta kinetically facilitates cotranslational translocation, but is not essential for it. Using chemical cross-linking we show that Sec61beta not only interacts with subunits of the Sec61 complex but also with the 25-kD subunit of the signal peptidase complex (SPC25), thus demonstrating for the first time a tight interaction between the SPC and the Sec61 complex. Interestingly, the cross-links between Sec61beta and SPC25 and between Sec61beta and Sec61alpha depend on the presence of membrane-bound ribosomes, suggesting that these interactions are induced when translocation is initiated. We propose that the SPC is transiently recruited to the translocation site, thus enhancing its activity.
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Affiliation(s)
- K U Kalies
- Abteilung Biochemie II, Zentrum Biochemie und Molekulare Zellbiologie, Georg-August-Universität, 37073 Göttingen, Germany
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31
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Abstract
The components responsible for protein translocation across the endoplasmic reticulum membrane have been identified and their functions have been clarified in vitro. The structural features of the signal peptide specify the factors and pathways of membrane translocation. Various chaperones and folding enzymes are involved in the folding and quality control of secretory proteins in the lumen.
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Affiliation(s)
- M Sakaguchi
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
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32
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Dalbey RE, Lively MO, Bron S, van Dijl JM. The chemistry and enzymology of the type I signal peptidases. Protein Sci 1997; 6:1129-38. [PMID: 9194173 PMCID: PMC2143710 DOI: 10.1002/pro.5560060601] [Citation(s) in RCA: 190] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The discovery that proteins exported from the cytoplasm are typically synthesized as larger precursors with cleavable signal peptides has focused interest on the peptidases that remove the signal peptides. Here, we review the membrane-bound peptidases dedicated to the processing of protein precursors that are found in the plasma membrane of prokaryotes and the endoplasmic reticulum, the mitochondrial inner membrane, and the chloroplast thylakoidal membrane of eukaryotes. These peptidases are termed type I signal (or leader) peptidases. They share the unusual feature of being resistant to the general inhibitors of the four well-characterized peptidase classes. The eukaryotic and prokaryotic signal peptidases appear to belong to a single peptidase family. This review emphasizes the evolutionary concepts, current knowledge of the catalytic mechanism, and substrate specificity requirements of the signal peptidases.
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Affiliation(s)
- R E Dalbey
- Department of Chemistry, Ohio State University, Columbus 43210, USA
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33
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Meyer HA, Hartmann E. The yeast SPC22/23 homolog Spc3p is essential for signal peptidase activity. J Biol Chem 1997; 272:13159-64. [PMID: 9148931 DOI: 10.1074/jbc.272.20.13159] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In eucaryotic cells signal sequences of secretory and membrane proteins are cleaved by the signal peptidase complex during their transport into the lumen of the endoplasmic reticulum. The signal peptidase complex in yeast consists of four subunits. To date, three of these subunits have been functionally characterized. One of them, the Sec11p, is essential for viability of yeast cells. It shows significant homology to the mammalian SPC18 and SPC21 as well as to bacterial leader peptidases. Two other subunits, Spc1p and Spc2p, have been shown to be homologous to mammalian SPC12 and SPC25, respectively, and are not essential for protein translocation or signal peptide cleavage. We have purified and analyzed the fourth subunit of yeast signal peptidase, Spc3p. The protein is essential for viability of yeast cells. Depletion of SPC3 leads to accumulation of precursors of secretory proteins in vivo and to the loss of the signal peptidase activity in vitro. Therefore, in contrast to the bacterial leader peptidases, yeast signal peptidase requires a second subunit for its function.
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Affiliation(s)
- H A Meyer
- Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany
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34
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Fang H, Mullins C, Green N. In addition to SEC11, a newly identified gene, SPC3, is essential for signal peptidase activity in the yeast endoplasmic reticulum. J Biol Chem 1997; 272:13152-8. [PMID: 9148930 DOI: 10.1074/jbc.272.20.13152] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Among the three characterized subunits comprising the signal peptidase complex of the yeast Saccharomyces cerevisiae (Sec11p, Spc1p, and Spc2p), only Sec11p is essential for cell growth, signal peptide cleavage, and signal peptidase-dependent protein degradation. Here we report the cloning of the SPC3 gene encoding the homolog to mammalian signal peptidase subunit SPC22/23. We find that Spc3p is also required for cell growth and signal peptidase activity within the yeast endoplasmic reticulum.
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Affiliation(s)
- H Fang
- Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363, USA
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