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Thulasi Devendrakumar K, Peng TS, Pierdzig L, Jackson E, Lipka V, Li X. Signal Peptide Peptidase and PI4Kβ1/2 play opposite roles in plant ER stress response and immunity. STRESS BIOLOGY 2024; 4:20. [PMID: 38507026 PMCID: PMC10954597 DOI: 10.1007/s44154-024-00155-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 02/07/2024] [Indexed: 03/22/2024]
Abstract
The Arabidopsis pi4kβ1,2 mutant is mutated in the phosphatidylinositol 4-kinase (PI4K) β1 and PI4Kβ2 enzymes which are involved in the biosynthesis of phosphatidylinositol 4-phosphate (PI4P), a minor membrane lipid with important signaling roles. pi4kβ1,2 plants display autoimmunity and shorter roots. Though the pi4kβ1,2 mutant has been extensively characterized, the source of its autoimmunity remains largely unknown. In this study, through a genetic suppressor screen, we identified multiple partial loss-of-function alleles of signal peptide peptidase (spp) that can suppress all the defects of pi4kβ1,2. SPP is an intramembrane cleaving aspartic protease. Interestingly, pi4kβ1,2 plants display enhanced ER stress response and mutations in SPP can suppress such phenotype. Furthermore, reduced ER stress responses were observed in the spp single mutants. Overall, our study reveals a previously unknown function of PI4Kβ and SPP in ER stress and plant immunity.
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Affiliation(s)
- Karen Thulasi Devendrakumar
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Tony ShengZhe Peng
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Leon Pierdzig
- Department of Plant Cell Biology, Georg August Universität Göttingen, 37077, Göttingen, Lower Saxony, Germany
| | - Edan Jackson
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Volker Lipka
- Department of Plant Cell Biology, Georg August Universität Göttingen, 37077, Göttingen, Lower Saxony, Germany
| | - Xin Li
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
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2
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Christianson JC, Jarosch E, Sommer T. Mechanisms of substrate processing during ER-associated protein degradation. Nat Rev Mol Cell Biol 2023; 24:777-796. [PMID: 37528230 DOI: 10.1038/s41580-023-00633-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2023] [Indexed: 08/03/2023]
Abstract
Maintaining proteome integrity is essential for long-term viability of all organisms and is overseen by intrinsic quality control mechanisms. The secretory pathway of eukaryotes poses a challenge for such quality assurance as proteins destined for secretion enter the endoplasmic reticulum (ER) and become spatially segregated from the cytosolic machinery responsible for disposal of aberrant (misfolded or otherwise damaged) or superfluous polypeptides. The elegant solution provided by evolution is ER-membrane-bound ubiquitylation machinery that recognizes misfolded or surplus proteins or by-products of protein biosynthesis in the ER and delivers them to 26S proteasomes for degradation. ER-associated protein degradation (ERAD) collectively describes this specialized arm of protein quality control via the ubiquitin-proteasome system. But, instead of providing a single strategy to remove defective or unwanted proteins, ERAD represents a collection of independent processes that exhibit distinct yet overlapping selectivity for a wide range of substrates. Not surprisingly, ER-membrane-embedded ubiquitin ligases (ER-E3s) act as central hubs for each of these separate ERAD disposal routes. In these processes, ER-E3s cooperate with a plethora of specialized factors, coordinating recognition, transport and ubiquitylation of undesirable secretory, membrane and cytoplasmic proteins. In this Review, we focus on substrate processing during ERAD, highlighting common threads as well as differences between the many routes via ERAD.
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Affiliation(s)
- John C Christianson
- Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
| | - Ernst Jarosch
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany
| | - Thomas Sommer
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany.
- Institute for Biology, Humboldt Universität zu Berlin, Berlin, Germany.
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3
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Yang J, Zhai N, Chen Y, Wang L, Chen R, Pan H. A signal peptide peptidase is required for ER-symbiosome proximal association and protein secretion. Nat Commun 2023; 14:4355. [PMID: 37468528 DOI: 10.1038/s41467-023-40008-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Accepted: 07/09/2023] [Indexed: 07/21/2023] Open
Abstract
During legume-rhizobia symbiosis, differentiation of the symbiosome (engulfed intracellular rhizobia) is necessary for successful nitrogen fixation. To control symbiosome differentiation, host cell subcellular components, e.g., ER (endoplasmic reticulum), must adapt robustly to ensure large-scale host protein secretion to the new organelle. However, the key components controlling the adaption of ER in nodule cells remain elusive. We report that Medicago BID1, a nodule-specific signal peptide peptidase (SPP), is central to ER structural dynamics and host protein secretion. In bid1, symbiosome differentiation is blocked. BID1 localizes specifically to the ER membrane and expresses exclusively in nodule cells with symbiosomes. In the wild type ER forms proximal association structures with symbiosomes, but not in bid1. Consequently, in bid1 excessive ER stress responses are induced and ER-to-symbiosome protein secretion is impaired. In summary, a nodule-specific SPP is necessary for ER-symbiosome proximal association, host protein secretion, and symbiosome differentiation.
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Affiliation(s)
- Jian Yang
- College of Biology, Hunan University, Changsha, China
| | - Niu Zhai
- Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Yuhui Chen
- College of Life Sciences, Lanzhou University, Lanzhou, China
| | - Luying Wang
- College of Biology, Hunan University, Changsha, China
| | - Rujin Chen
- College of Life Sciences, Lanzhou University, Lanzhou, China
| | - Huairong Pan
- College of Biology, Hunan University, Changsha, China.
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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Xue S, Liu X, Pan Y, Xiao C, Feng Y, Zheng L, Zhao M, Huang M. Comprehensive Analysis of Signal Peptides in Saccharomyces cerevisiae Reveals Features for Efficient Secretion. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2203433. [PMID: 36478443 PMCID: PMC9839866 DOI: 10.1002/advs.202203433] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 11/10/2022] [Indexed: 05/30/2023]
Abstract
Signal peptides (SPs) are N-terminus sequences on the nascent polypeptide for protein export or localization delivery, which are essential for maintaining cell function. SPs are also employed as a key element for industrial production of secreted recombinant proteins. Yet, detailed information and rules about SPs and their cellular interactions are still not well understood. Here, systematic bioinformatics analysis and secretion capacity measurement of genome-wide SPs from the model organism Saccharomyces cerevisiae is performed. Several key features of SPs, including region properties, consensus motifs, evolutionary relationships, codon bias, e.g., are successfully revealed. Diverse cell metabolism can be trigged by using different SPs for heterologous protein secretion. Influences on SPs with different properties by chaperones can cause different secretory efficiencies. Protein secretion by the SP NCW2 in SEC72 deletion strain is 10 times than the control. These findings provide insights into the properties and functions of SPs and contribute to both fundamental research and industrial application.
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Affiliation(s)
- Songlyu Xue
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Xiufang Liu
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Yuyang Pan
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Chufan Xiao
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Yunzi Feng
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Lin Zheng
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Mouming Zhao
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
| | - Mingtao Huang
- School of Food Science and EngineeringSouth China University of TechnologyGuangzhou510641China
- Guangdong Food Green Processing and Nutrition Regulation Technologies Research CenterGuangzhou510650China
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6
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Liu J, Li W, Wu L. Pan-cancer analysis suggests histocompatibility minor 13 is an unfavorable prognostic biomarker promoting cell proliferation, migration, and invasion in hepatocellular carcinoma. Front Pharmacol 2022; 13:950156. [PMID: 36046831 PMCID: PMC9421072 DOI: 10.3389/fphar.2022.950156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 07/21/2022] [Indexed: 02/05/2023] Open
Abstract
Histocompatibility Minor 13 (HM13) encoding the signal peptide peptidase plays an important role in maintaining protein homeostasis but its role in tumors remains unclear. In this study, 33 tumor RNA-seq datasets were extracted from The Cancer Genome Atlas (TCGA) database, and the pan-cancer expression profile of HM13 was evaluated in combination with The Genotype-Tissue Expression (GTEx) datasets. The prognostic significance of abnormal HM13 pan-cancer expression was evaluated by univariate Cox regression and Kaplan-Meier analyses. Co-expression analysis was performed to examine the correlation between abnormal pan-cancer expression of HM13 and immune cell infiltration, immune checkpoint, molecules related to RNA modification, tumor mutational burden (TMB), microsatellite instability (MSI), and other related molecules. CellMiner database was used to evaluate the relationship between the expression of HM13 and drug sensitivity. The results showed overexpression of HM13 in almost all tumors except kidney chromophobe (KICH). Abnormally high expression of HM13 in adrenocortical carcinoma (ACC), kidney renal papillary cell carcinoma (KIRP), uveal melanoma (UVM), liver hepatocellular carcinoma (LIHC), brain lower grade glioma (LGG), head and neck squamous cell carcinoma (HNSC), and kidney renal clear cell carcinoma (KIRC) was associated with poor prognosis. Expression of HM13 correlated strongly with pan-cancer immune checkpoint gene expression and immune cell infiltration. Drug sensitivity analysis indicated that the expression of HM13 was an excellent predictor of drug sensitivity. We verified that both mRNA and protein levels of HM13 were abnormally upregulated in HCC tissues, and were independent risk factors for poor prognosis. Furthermore, interference with HM13 expression in Huh-7 and HCCLM3 cells significantly inhibited proliferation, migration, and invasion. Therefore, our findings demonstrate that HM13 is a potential pan-cancer prognostic marker, thus providing a new dimension for understanding tumor development.
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Affiliation(s)
- Jun Liu
- Department of Clinical Laboratory, Yue Bei People’s Hospital, Shantou University Medical College, Shaoguan, Guangdong, China
- Medical Research Center, Yue Bei People’s Hospital, Shantou University Medical College, Shaoguan, Guangdong, China
| | - Wenli Li
- Reproductive Medicine Center, Yue Bei People’s Hospital, Shantou University Medical College, Shaoguan, Guangdong, China
| | - Liangyin Wu
- Department of Clinical Laboratory, Yue Bei People’s Hospital, Shantou University Medical College, Shaoguan, Guangdong, China
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7
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Zhang G, Lv X, Yang Q, Liu H. Identification of HM13 as a prognostic indicator and a predictive biomarker for immunotherapy in hepatocellular carcinoma. BMC Cancer 2022; 22:888. [PMID: 35964022 PMCID: PMC9375928 DOI: 10.1186/s12885-022-09987-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 08/02/2022] [Indexed: 12/12/2022] Open
Abstract
Background Histocompatibility minor 13 (HM13) is a signal sequence stubbed intramembrane cleavage catalytic protein that is essential for cell signaling, intracellular communication, and cancer. However, the expression of HM13 and its prognostic value, association with tumor-infiltrating immune cells (TIICs) in the microenvironment, and potential to predict immunotherapeutic response in HCC are unknown. Methods The HM13 expression, clinicopathology analysis, and its influence on survival were analyzed in multiple public databases and further verified in collected HCC and normal tissues by qRT-PCR and immunohistochemistry staining assay (IHC). Furthermore, the lentivirus vector encoding HM13-shRNA to manipulate HM13 expression was selected to investigate whether HM13 could influence the malignant growth and metastasis potential of HCC cells. Finally, significant impacts of HM13 on the HCC tumor microenvironment (TME) and reaction to immune checkpoint inhibitors were analyzed. Results Upregulated HM13 was substantially correlated with poor prognosis in patients with HCC, and could facilitate the proliferation and migratory potential of HCC cells. Additionally, patients with high HM13 expression might be more sensitive to immunotherapy. Conclusions HM13 might be a prognostic biomarker and potential molecular therapeutic target for HCC. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-022-09987-2.
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Affiliation(s)
- Genhao Zhang
- Department of Blood transfusion, Zhengzhou University First Affiliated Hospital, Zhengzhou, China
| | - Xianping Lv
- Department of Blood transfusion, Zhengzhou University First Affiliated Hospital, Zhengzhou, China
| | - Qiankun Yang
- Department of Blood transfusion, Zhengzhou University First Affiliated Hospital, Zhengzhou, China
| | - Hongchun Liu
- Department of Medical Laboratory, Zhengzhou University First Affiliated Hospital, Zhengzhou, China.
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8
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Lemberg MK, Strisovsky K. Maintenance of organellar protein homeostasis by ER-associated degradation and related mechanisms. Mol Cell 2021; 81:2507-2519. [PMID: 34107306 DOI: 10.1016/j.molcel.2021.05.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 04/14/2021] [Accepted: 05/05/2021] [Indexed: 12/19/2022]
Abstract
Protein homeostasis mechanisms are fundamentally important to match cellular needs and to counteract stress conditions. A fundamental challenge is to understand how defective proteins are recognized and extracted from cellular organelles to be degraded in the cytoplasm. The endoplasmic reticulum (ER)-associated degradation (ERAD) pathway is the best-understood organellar protein quality control system. Here, we review new insights into the mechanism of recognition and retrotranslocation of client proteins in ERAD. In addition to the membrane-integral ERAD E3 ubiquitin ligases, we highlight one protein family that is remarkably often involved in various aspects of membrane protein quality control and protein dislocation: the rhomboid superfamily, which includes derlins and intramembrane serine proteases. Rhomboid-like proteins have been found to control protein homeostasis in the ER, but also in other eukaryotic organelles and in bacteria, pointing toward conserved principles of membrane protein quality control across organelles and evolution.
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Affiliation(s)
- Marius K Lemberg
- Center for Molecular Biology of Heidelberg University (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany; Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 52, 50931 Cologne, Germany.
| | - Kvido Strisovsky
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czechia.
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9
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Hepatitis C virus modulates signal peptide peptidase to alter host protein processing. Proc Natl Acad Sci U S A 2021; 118:2026184118. [PMID: 34035171 PMCID: PMC8179148 DOI: 10.1073/pnas.2026184118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mechanism by which hepatitis C virus (HCV) evades immune surveillance and causes chronic infection is unclear. We demonstrate here that HCV core protein interferes with the maturation of major histocompatibility complex (MHC) class I catalyzed by signal peptide peptidase (SPP) and induces degradation via HMG-CoA reductase degradation 1 homolog. In addition, we found that the core protein transmembrane domain is homologous to the human cytomegalovirus US2 protein, whose transmembrane region also targets SPP to impair MHC class I molecule expression in a similar manner. Therefore, our data suggest that SPP represents a potential target for the impairment of MHC class I molecules by DNA and RNA viruses. Immunoevasins are viral proteins that prevent antigen presentation on major histocompatibility complex (MHC) class I, thus evading host immune recognition. Hepatitis C virus (HCV) evades immune surveillance to induce chronic infection; however, how HCV-infected hepatocytes affect immune cells and evade immune recognition remains unclear. Herein, we demonstrate that HCV core protein functions as an immunoevasin. Its expression interfered with the maturation of MHC class I molecules catalyzed by the signal peptide peptidase (SPP) and induced their degradation via HMG-CoA reductase degradation 1 homolog, thereby impairing antigen presentation to CD8+ T cells. The expression of MHC class I in the livers of HCV core transgenic mice and chronic hepatitis C patients was impaired but was restored in patients achieving sustained virological response. Finally, we show that the human cytomegalovirus US2 protein, possessing a transmembrane region structurally similar to the HCV core protein, targets SPP to impair MHC class I molecule expression. Thus, SPP represents a potential target for the impairment of MHC class I molecules by DNA and RNA viruses.
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10
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Spatially Resolved Tagging of Proteolytic Neo-N termini with Subtiligase-TM. J Membr Biol 2021; 254:119-125. [PMID: 33599828 DOI: 10.1007/s00232-021-00171-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 01/07/2021] [Indexed: 12/11/2022]
Abstract
Mass spectrometry-based proteomics has been used successfully to identify substrates for proteases. Identification of protease substrates at the cell surface, however, can be challenging since cleavages are less abundant compared to other cellular events. Precise methods are required to delineate cleavage events that take place in these compartmentalized areas. This article by up-and-coming scientist Dr. Amy Weeks, an Assistant Professor at the University of Wisconsin-Madison, provides an overview of methods developed to identify protease substrates and their cleavage sites at the membrane. An overview is presented with the pros and cons for each method and in particular the N-terminomics subtiligase-TM method, developed by Dr. Weeks as a postdoctoral fellow in the lab of Dr. Jim Wells at University of California, San Francisco, is described in detail. Subtiligase-TM is a genetically engineered subtilisin protease variant that acts to biotinylate newly generated N termini, hence revealing new cleavage events in the presence of a specific enzyme, and furthermore can precisely identify the cleavage P1 site. Importantly, this proteomics method is compatible with living cells. This method will open the door to understanding protein shedding events at the biological membrane controlled by proteases to regulate biological processes.
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11
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Signal Peptide Peptidase-Type Proteases: Versatile Regulators with Functions Ranging from Limited Proteolysis to Protein Degradation. J Mol Biol 2020; 432:5063-5078. [DOI: 10.1016/j.jmb.2020.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/02/2020] [Accepted: 05/19/2020] [Indexed: 12/15/2022]
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12
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Kusunoki K, Hoshi M, Tamura T, Maeda T, Abe K, Asakura T. Yeast-based reporter assay system for identifying the requirements of intramembrane proteolysis by signal peptide peptidase of Arabidopsis thaliana. FEBS Open Bio 2020; 10:1833-1842. [PMID: 32686366 PMCID: PMC7459403 DOI: 10.1002/2211-5463.12936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 06/11/2020] [Accepted: 07/05/2020] [Indexed: 11/09/2022] Open
Abstract
Signal peptide peptidase (SPP) is an aspartic protease with two active sites, YD and GXGD, in the transmembrane domain. SPP cleaves signal peptides, and the released fragments play key roles in the immune system, embryo development and protein turnover in cells. Despite SPP having an important function, a general system to identify the requirements of intramembrane proteolysis by SPP has not been developed because proteolysis occurs in the membrane. In this study, we first established a reporter assay system in yeast to verify the cleavage activity of the Arabidopsis thaliana SPP (AtSPP). Next, we screened candidate substrates of AtSPP from A. thaliana pollen and roots. In the pollen, 13 signal peptides with 'pollen' and 'cell wall' as gene ontology terms were selected. In the roots, mutants overexpressing AtSPP were constructed, and gene expression changes were compared with the wild‐type. Nine signal peptides expressed in the roots were selected. Then we used the candidate substrates in our reporter assay system to determine the requirements for proteolysis by AtSPP. Fifteen of 22 signal peptides were cleaved by AtSPP. The absence of the positively charged amino acids, His and Lys on the C terminus of the signal sequence, was observed in cleaved substrates. Moreover, mutation of a helix breaker‐to‐Leu substitution in the intramembrane region in substrates prevented cleavage by AtSPP. These results indicated that substrates of AtSPP required the helix breaker structure to be cleaved.
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Affiliation(s)
- Kenta Kusunoki
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan
| | - Masako Hoshi
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan
| | - Tomoko Tamura
- Department of Nutritional Science and Food Safety, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Tatsuya Maeda
- Department of Biology, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Keiko Abe
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan
| | - Tomiko Asakura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan
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Tang D, Sandoval W, Lam C, Haley B, Liu P, Xue D, Roy D, Patapoff T, Louie S, Snedecor B, Misaghi S. UBR E3 ligases and the PDIA3 protease control degradation of unfolded antibody heavy chain by ERAD. J Cell Biol 2020; 219:151862. [PMID: 32558906 PMCID: PMC7337499 DOI: 10.1083/jcb.201908087] [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: 08/09/2019] [Revised: 02/03/2020] [Accepted: 04/06/2020] [Indexed: 12/01/2022] Open
Abstract
Accumulation of unfolded antibody chains in the ER triggers ER stress that may lead to reduced productivity in therapeutic antibody manufacturing processes. We identified UBR4 and UBR5 as ubiquitin E3 ligases involved in HC ER-associated degradation. Knockdown of UBR4 and UBR5 resulted in intracellular accumulation, enhanced secretion, and reduced ubiquitination of HC. In concert with these E3 ligases, PDIA3 was shown to cleave ubiquitinated HC molecules to accelerate HC dislocation. Interestingly, UBR5, and to a lesser degree UBR4, were down-regulated as cellular demand for antibody expression increased in CHO cells during the production phase, or in plasma B cells. Reducing UBR4/UBR5 expression before the production phase increased antibody productivity in CHO cells, possibly by redirecting antibody molecules from degradation to secretion. Altogether we have characterized a novel proteolysis/proteasome-dependent pathway involved in degradation of unfolded antibody HC. Proteins characterized in this pathway may be novel targets for CHO cell engineering.
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Affiliation(s)
- Danming Tang
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
| | - Wendy Sandoval
- Department of Microchemistry, Proteomics and Lipidomics, Genentech Inc., South San Francisco, CA
| | - Cynthia Lam
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
| | - Benjamin Haley
- Department of Molecular Biology, Genentech Inc., South San Francisco, CA
| | - Peter Liu
- Department of Microchemistry, Proteomics and Lipidomics, Genentech Inc., South San Francisco, CA
| | - Di Xue
- Department of Research Biology, Genentech Inc., South San Francisco, CA
| | - Deepankar Roy
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
| | - Tom Patapoff
- Department of Early Stage Pharmaceutical Development, Genentech Inc., South San Francisco, CA
| | - Salina Louie
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
| | - Brad Snedecor
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
| | - Shahram Misaghi
- Cell Culture and Bioprocess Operations Department, Genentech Inc., South San Francisco, CA
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14
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Began J, Cordier B, Březinová J, Delisle J, Hexnerová R, Srb P, Rampírová P, Kožíšek M, Baudet M, Couté Y, Galinier A, Veverka V, Doan T, Strisovsky K. Rhomboid intramembrane protease YqgP licenses bacterial membrane protein quality control as adaptor of FtsH AAA protease. EMBO J 2020; 39:e102935. [PMID: 31930742 PMCID: PMC7231995 DOI: 10.15252/embj.2019102935] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 11/18/2019] [Accepted: 12/12/2019] [Indexed: 12/31/2022] Open
Abstract
Magnesium homeostasis is essential for life and depends on magnesium transporters, whose activity and ion selectivity need to be tightly controlled. Rhomboid intramembrane proteases pervade the prokaryotic kingdom, but their functions are largely elusive. Using proteomics, we find that Bacillus subtilis rhomboid protease YqgP interacts with the membrane‐bound ATP‐dependent processive metalloprotease FtsH and cleaves MgtE, the major high‐affinity magnesium transporter in B. subtilis. MgtE cleavage by YqgP is potentiated in conditions of low magnesium and high manganese or zinc, thereby protecting B. subtilis from Mn2+/Zn2+ toxicity. The N‐terminal cytosolic domain of YqgP binds Mn2+ and Zn2+ ions and facilitates MgtE cleavage. Independently of its intrinsic protease activity, YqgP acts as a substrate adaptor for FtsH, a function that is necessary for degradation of MgtE. YqgP thus unites protease and pseudoprotease function, hinting at the evolutionary origin of rhomboid pseudoproteases such as Derlins that are intimately involved in eukaryotic ER‐associated degradation (ERAD). Conceptually, the YqgP‐FtsH system we describe here is analogous to a primordial form of “ERAD” in bacteria and exemplifies an ancestral function of rhomboid‐superfamily proteins.
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Affiliation(s)
- Jakub Began
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic.,Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Baptiste Cordier
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie de la Méditerranée (IMM), CNRS, UMR 7283, Aix Marseille Univ, Marseille Cedex 20, France
| | - Jana Březinová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic.,Department of Biochemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Jordan Delisle
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie de la Méditerranée (IMM), CNRS, UMR 7283, Aix Marseille Univ, Marseille Cedex 20, France
| | - Rozálie Hexnerová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
| | - Pavel Srb
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
| | - Petra Rampírová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
| | - Milan Kožíšek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
| | - Mathieu Baudet
- CEA, Inserm, IRIG-BGE, Univ. Grenoble Alpes, Grenoble, France
| | - Yohann Couté
- CEA, Inserm, IRIG-BGE, Univ. Grenoble Alpes, Grenoble, France
| | - Anne Galinier
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie de la Méditerranée (IMM), CNRS, UMR 7283, Aix Marseille Univ, Marseille Cedex 20, France
| | - Václav Veverka
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic.,Department of Cell Biology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Thierry Doan
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie de la Méditerranée (IMM), CNRS, UMR 7283, Aix Marseille Univ, Marseille Cedex 20, France.,Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), CNRS, UMR 7255, Aix Marseille Univ, Marseille Cedex 20, France
| | - Kvido Strisovsky
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
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Absence of Signal Peptide Peptidase, an Essential Herpes Simplex Virus 1 Glycoprotein K Binding Partner, Reduces Virus Infectivity In Vivo. J Virol 2019; 93:JVI.01309-19. [PMID: 31511378 DOI: 10.1128/jvi.01309-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 09/02/2019] [Indexed: 12/12/2022] Open
Abstract
We previously reported that herpes simplex virus (HSV) glycoprotein K (gK) binds to signal peptide peptidase (SPP), also known as minor histocompatibility antigen H13. Binding of gK to SPP is required for HSV-1 infectivity in vitro SPP is a member of the γ-secretase family, and mice lacking SPP are embryonic lethal. To determine how SPP affects HSV-1 infectivity in vivo, the SPP gene was deleted using a tamoxifen-inducible Cre recombinase driven by the ubiquitously expressed ROSA26 promoter. SPP mRNA was reduced by more than 93% in the cornea and trigeminal ganglia (TG) and by 99% in the liver of tamoxifen-injected mice, while SPP protein expression was reduced by 90% compared to the level in control mice. Mice lacking SPP had significantly less HSV-1 replication in the eye as well as reduced gK, UL20, ICP0, and gB transcripts in the cornea and TG compared to levels in control mice. In addition, reduced infiltration of CD45+, CD4+, CD8+, F4/80+, CD11c+, and NK1.1+ T cells was observed in the cornea and TG of SPP-inducible knockout mice compared to that in control mice. Finally, in the absence of SPP, latency was significantly reduced in SPP-inducible knockout mice compared to that in control mice. Thus, in this study we have generated SPP-inducible knockout mice and shown that the absence of SPP affects virus replication in the eye of ocularly infected mice and that this reduction is correlated with the interaction of gK and SPP. These results suggest that blocking this interaction may have therapeutic potential in treating HSV-1-associated eye disease.IMPORTANCE Glycoprotein K (gK) is an essential and highly conserved HSV-1 protein. Previously, we reported that gK binds to SPP, an endoplasmic reticulum (ER) protein, and blocking this binding reduces virus infectivity in vitro and also affects gK and UL20 subcellular localization. To evaluate the function of gK binding to SPP in vivo, we generated SPP-inducible knockout mice and observed the following in the absence of SPP: (i) that significantly less HSV-1 replication was seen in ocularly infected mice than in control mice; (ii) that expression of various HSV-1 genes and cellular infiltrates in the eye and trigeminal ganglia of infected mice was less than that in control mice; and (iii) that latency was significantly reduced in infected mice. Thus, blocking of gK binding to SPP may be a useful tool to control HSV-1-induced eye disease in patients with herpes stromal keratitis (HSK).
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16
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Needham PG, Guerriero CJ, Brodsky JL. Chaperoning Endoplasmic Reticulum-Associated Degradation (ERAD) and Protein Conformational Diseases. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033928. [PMID: 30670468 DOI: 10.1101/cshperspect.a033928] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases. In this review, we discuss the factors that constitute the ERAD machinery and detail how each step in the pathway occurs. We then highlight the underlying pathophysiology of protein conformational diseases associated with ERAD.
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Affiliation(s)
- Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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17
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Manandhar T, Hò GGT, Pump WC, Blasczyk R, Bade-Doeding C. Battle between Host Immune Cellular Responses and HCMV Immune Evasion. Int J Mol Sci 2019; 20:E3626. [PMID: 31344940 PMCID: PMC6695940 DOI: 10.3390/ijms20153626] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/18/2019] [Accepted: 07/19/2019] [Indexed: 12/16/2022] Open
Abstract
Human cytomegalovirus (HCMV) is ubiquitously prevalent. HCMV infection is typically asymptomatic and controlled by the immune system in healthy individuals, yet HCMV can be severely pathogenic for the fetus during pregnancy and in immunocompromised persons, such as transplant recipients or HIV infected patients. HCMV has co-evolved with the hosts, developed strategies to hide from immune effector cells and to successfully survive in the human organism. One strategy for evading or delaying the immune response is maintenance of the viral genome to establish the phase of latency. Furthermore, HCMV immune evasion involves the downregulation of human leukocyte antigens (HLA)-Ia molecules to hide infected cells from T-cell recognition. HCMV expresses several proteins that are described for downregulation of the HLA class I pathway via various mechanisms. Here, we review the wide range of immune evasion mechanisms of HCMV. Understanding the mechanisms of HCMV immune evasion will contribute to the development of new customized therapeutic strategies against the virus.
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Affiliation(s)
- Trishna Manandhar
- Institute for Transfusion Medicine, Hannover Medical School, 30625 Hannover, Germany
| | - Gia-Gia T Hò
- Institute for Transfusion Medicine, Hannover Medical School, 30625 Hannover, Germany
| | - Wiebke C Pump
- Institute for Transfusion Medicine, Hannover Medical School, 30625 Hannover, Germany
| | - Rainer Blasczyk
- Institute for Transfusion Medicine, Hannover Medical School, 30625 Hannover, Germany
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18
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Hsu FF, Chou YT, Chiang MT, Li FA, Yeh CT, Lee WH, Chau LY. Signal peptide peptidase promotes tumor progression via facilitating FKBP8 degradation. Oncogene 2018; 38:1688-1701. [PMID: 30348988 DOI: 10.1038/s41388-018-0539-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 08/28/2018] [Accepted: 09/21/2018] [Indexed: 11/09/2022]
Abstract
Signal peptide peptidase (SPP) is an endoplasmic reticulum (ER)-resident aspartyl protease mediating intramembrane cleavage of type II transmembrane proteins. Increasing evidence has supported the role of SPP in ER-associated protein degradation. In the present study, we show that SPP expression is highly induced in human lung and breast cancers and correlated with disease outcome. Stable depletion of SPP expression in lung and breast cancer cell lines significantly reduced cell growth and migration/invasion abilities. Quantitative analysis of the proteomic changes of microsomal proteins in lung cancer cells by the stable isotope labeling with amino acids in cell culture (SILAC) approach revealed that the level of FKBP8, an endogenous inhibitor of mTOR, was significantly increased following SPP depletion. Co-immunoprecipitation assay and confocal immunofluorescence demonstrated that SPP interacted and colocalized with FKBP8 in ER, supporting that FKBP8 is a protein substrate of SPP. Cycloheximide chase and proteasome inhibition experiments revealed that SPP-mediated proteolysis facilitated FKBP8 protein degradation in cytosol. Further experiment demonstrated that the levels of phosphorylation in mTOR and its downstream effectors, S6K and 4E-BP1, were significantly lower in SPP-depleted cells. The reduced mTOR signaling and decreases of growth and migration/invasion abilities induced by SPP depletion in cancer cells could be reversed by FKBP8 downregulation. The implication of FKBP8 in SPP-mediated tumorigenicity was also observed in the xenograft model. Together, these findings disclose that SPP promotes tumor progression, at least in part, via facilitating the degradation of FKBP8 to enhance mTOR signaling.
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Affiliation(s)
- Fu-Fei Hsu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yi-Tai Chou
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ming-Tsai Chiang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Fu-An Li
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chi-Tai Yeh
- Cancer Center, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan
| | - Wei-Hwa Lee
- Cancer Center, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan
| | - Lee-Young Chau
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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19
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Lichtenthaler SF, Lemberg MK, Fluhrer R. Proteolytic ectodomain shedding of membrane proteins in mammals-hardware, concepts, and recent developments. EMBO J 2018; 37:e99456. [PMID: 29976761 PMCID: PMC6068445 DOI: 10.15252/embj.201899456] [Citation(s) in RCA: 189] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/05/2018] [Accepted: 06/18/2018] [Indexed: 12/14/2022] Open
Abstract
Proteolytic removal of membrane protein ectodomains (ectodomain shedding) is a post-translational modification that controls levels and function of hundreds of membrane proteins. The contributing proteases, referred to as sheddases, act as important molecular switches in processes ranging from signaling to cell adhesion. When deregulated, ectodomain shedding is linked to pathologies such as inflammation and Alzheimer's disease. While proteases of the "a disintegrin and metalloprotease" (ADAM) and "beta-site APP cleaving enzyme" (BACE) families are widely considered as sheddases, in recent years a much broader range of proteases, including intramembrane and soluble proteases, were shown to catalyze similar cleavage reactions. This review demonstrates that shedding is a fundamental process in cell biology and discusses the current understanding of sheddases and their substrates, molecular mechanisms and cellular localizations, as well as physiological functions of protein ectodomain shedding. Moreover, we provide an operational definition of shedding and highlight recent conceptual advances in the field. While new developments in proteomics facilitate substrate discovery, we expect that shedding is not a rare exception, but rather the rule for many membrane proteins, and that many more interesting shedding functions await discovery.
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Affiliation(s)
- Stefan F Lichtenthaler
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Neuroproteomics, Klinikum rechts der Isar, School of Medicine, and Institute for Advanced Study, Technical University Munich, Munich, Germany
- Munich Center for Systems Neurology (SyNergy), Munich, Germany
| | - Marius K Lemberg
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Regina Fluhrer
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Biomedizinisches Centrum (BMC), Ludwig-Maximilians University of Munich, Munich, Germany
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20
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Wei JW, Cai JQ, Fang C, Tan YL, Huang K, Yang C, Chen Q, Jiang CL, Kang CS. Signal Peptide Peptidase, Encoded by HM13, Contributes to Tumor Progression by Affecting EGFRvIII Secretion Profiles in Glioblastoma. CNS Neurosci Ther 2017; 23:257-265. [PMID: 28198167 DOI: 10.1111/cns.12672] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 12/06/2016] [Accepted: 12/08/2016] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND AND AIMS EGFRvIII is the most prevalent glioblastoma mutation, occurring in more than 25% of glioblastomas. EGFRvIII cells release microvesicles that contain proteins, miRNAs, and mRNAs that enhance the growth and survival of surrounding tumor cells. However, little is known about the maturation process and regulatory mechanisms of secreted vesicles in EGFRvIII cells. METHODS Signal peptide peptidase (SPP) provides a fascinating mechanism for protein cleavage and subsequent dislocation in the endoplasmic reticulum transmembrane domain. RESULTS In this study, we reported that SPP facilitates the secretion of cytokines in vitro and promotes tumor progression in mice. Human cytokine antibody arrays revealed that EGFRvIII secreted higher levels of cytokines, but these levels were significantly reduced following SPP knockdown, suggesting that cytokines in EGFRvIII secretion profiles play important roles in GBM development. Identical results were confirmed in intracellular maturation tracking of TGF-β1 in mouse serum. Clinically, analyses of GBM patient data from the database revealed that HM13 expression was closely related to patient prognosis and survival, suggesting an influence by the secreted vesicles of EGFRvIII tumor cells. CONCLUSIONS Collectively, our study identifies that SPP affects EGFRvIII secretion profiles and thus promotes tumor progression, providing further understanding of the formation of secreted vesicles and driving role of EGFRvIII in GBM.
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Affiliation(s)
- Jian-Wei Wei
- Department of Neurosurgery, Laboratory of Neuro-oncology, Tianjin Neurological Institute, Key Laboratory of Post-Neuro injury Neuro-repair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Medical University General Hospital, Tianjin, China
| | - Jin-Quan Cai
- Department of Neurosurgery, The Second Affiliated Hospital of Harbin Medical University, NanGang District, Harbin, Heilongjiang Province, China
| | - Chuan Fang
- Department of Neurosurgery, The Hospital affiliated to Hebei University, Baoding, China
| | - Yan-Li Tan
- College of Fundamental Medicine, Hebei University, Baoding, China
| | - Kai Huang
- Department of Neurosurgery, Laboratory of Neuro-oncology, Tianjin Neurological Institute, Key Laboratory of Post-Neuro injury Neuro-repair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Medical University General Hospital, Tianjin, China
| | - Chao Yang
- Department of Neurosurgery, Laboratory of Neuro-oncology, Tianjin Neurological Institute, Key Laboratory of Post-Neuro injury Neuro-repair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Medical University General Hospital, Tianjin, China
| | - Qun Chen
- Department of Neurosurgery, The Second Affiliated Hospital of Harbin Medical University, NanGang District, Harbin, Heilongjiang Province, China
| | - Chuan-Lu Jiang
- Department of Neurosurgery, The Second Affiliated Hospital of Harbin Medical University, NanGang District, Harbin, Heilongjiang Province, China
| | - Chun-Sheng Kang
- Department of Neurosurgery, Laboratory of Neuro-oncology, Tianjin Neurological Institute, Key Laboratory of Post-Neuro injury Neuro-repair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Medical University General Hospital, Tianjin, China
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21
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Moriishi K. The potential of signal peptide peptidase as a therapeutic target for hepatitis C. Expert Opin Ther Targets 2017; 21:827-836. [DOI: 10.1080/14728222.2017.1369959] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Kohji Moriishi
- Department of Microbiology, Graduate School of Medical Science, University of Yamanashi, Yamanashi, Japan
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22
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Mentrup T, Fluhrer R, Schröder B. Latest emerging functions of SPP/SPPL intramembrane proteases. Eur J Cell Biol 2017; 96:372-382. [DOI: 10.1016/j.ejcb.2017.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/28/2017] [Accepted: 03/02/2017] [Indexed: 10/20/2022] Open
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23
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Signal peptide peptidase and SPP-like proteases - Possible therapeutic targets? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017. [PMID: 28624439 DOI: 10.1016/j.bbamcr.2017.06.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Signal peptide peptidase (SPP) and the four homologous SPP-like proteases SPPL2a, SPPL2b, SPPL2c and SPPL3 are GxGD-type intramembrane-cleaving proteases (I-CLIPs). In addition to divergent subcellular localisations, distinct differences in the mechanistic properties and substrate requirements of individual family members have been unravelled. SPP/SPPL proteases employ a catalytic mechanism related to that of the γ-secretase complex. Nevertheless, differential targeting of SPP/SPPL proteases and γ-secretase by inhibitors has been demonstrated. Furthermore, also within the SPP/SPPL family significant differences in the sensitivity to currently available inhibitory compounds have been reported. Though far from complete, our knowledge on pathophysiological functions of SPP/SPPL proteases, in particular based on studies in mice, has been significantly increased over the last years. Based on this, inhibition of distinct SPP/SPPL proteases has been proposed as a novel therapeutic concept e.g. for the treatment of autoimmunity and viral or protozoal infections, as we will discuss in this review. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.
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24
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Kaiser G, De Niz M, Zuber B, Burda PC, Kornmann B, Heussler VT, Stanway RR. High resolution microscopy reveals an unusual architecture of the Plasmodium berghei endoplasmic reticulum. Mol Microbiol 2016; 102:775-791. [PMID: 27566438 DOI: 10.1111/mmi.13490] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2016] [Indexed: 02/04/2023]
Abstract
To fuel the tremendously fast replication of Plasmodium liver stage parasites, the endoplasmic reticulum (ER) must play a critical role as a major site of protein and lipid biosynthesis. In this study, we analysed the parasite's ER morphology and function. Previous studies exploring the parasite ER have mainly focused on the blood stage. Visualizing the Plasmodium berghei ER during liver stage development, we found that the ER forms an interconnected network throughout the parasite with perinuclear and peripheral localizations. Surprisingly, we observed that the ER additionally generates huge accumulations. Using stimulated emission depletion microscopy and serial block-face scanning electron microscopy, we defined ER accumulations as intricate dense networks of ER tubules. We provide evidence that these accumulations are functional subdivisions of the parasite ER, presumably generated in response to elevated demands of the parasite, potentially consistent with ER stress. Compared to higher eukaryotes, Plasmodium parasites have a fundamentally reduced unfolded protein response machinery for reacting to ER stress. Accordingly, parasite development is greatly impaired when ER stress is applied. As parasites appear to be more sensitive to ER stress than are host cells, induction of ER stress could potentially be used for interference with parasite development.
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Affiliation(s)
- Gesine Kaiser
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Baltzerstrasse 2, 3012, Bern, Switzerland
| | - Mariana De Niz
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland.,Wellcome Trust Center for Molecular Parasitology, G12 8TA, Glasgow, UK
| | - Benoît Zuber
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012, Bern, Switzerland
| | - Paul-Christian Burda
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
| | - Benoît Kornmann
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, 8093, Zürich, Switzerland
| | - Volker T Heussler
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
| | - Rebecca R Stanway
- Institute of Cell Biology, University of Bern, Baltzerstr. 4, 3012 Bern, Switzerland
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25
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Frabutt DA, Zheng YH. Arms Race between Enveloped Viruses and the Host ERAD Machinery. Viruses 2016; 8:v8090255. [PMID: 27657106 PMCID: PMC5035969 DOI: 10.3390/v8090255] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/12/2016] [Accepted: 09/12/2016] [Indexed: 12/12/2022] Open
Abstract
Enveloped viruses represent a significant category of pathogens that cause serious diseases in animals. These viruses express envelope glycoproteins that are singularly important during the infection of host cells by mediating fusion between the viral envelope and host cell membranes. Despite low homology at protein levels, three classes of viral fusion proteins have, as of yet, been identified based on structural similarities. Their incorporation into viral particles is dependent upon their proper sub-cellular localization after being expressed and folded properly in the endoplasmic reticulum (ER). However, viral protein expression can cause stress in the ER, and host cells respond to alleviate the ER stress in the form of the unfolded protein response (UPR); the effects of which have been observed to potentiate or inhibit viral infection. One important arm of UPR is to elevate the capacity of the ER-associated protein degradation (ERAD) pathway, which is comprised of host quality control machinery that ensures proper protein folding. In this review, we provide relevant details regarding viral envelope glycoproteins, UPR, ERAD, and their interactions in host cells.
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Affiliation(s)
- Dylan A Frabutt
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
| | - Yong-Hui Zheng
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
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26
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Avci D, Lemberg MK. Clipping or Extracting: Two Ways to Membrane Protein Degradation. Trends Cell Biol 2016; 25:611-622. [PMID: 26410407 DOI: 10.1016/j.tcb.2015.07.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/18/2015] [Accepted: 07/17/2015] [Indexed: 12/20/2022]
Abstract
Protein degradation is a fundamentally important process that allows cells to recognize and remove damaged protein species and to regulate protein abundance according to functional need. A fundamental challenge is to understand how membrane proteins are recognized and removed from cellular organelles. While most of our understanding of this mechanism comes from studies on p97/Cdc48-mediated protein dislocation along the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway, recent studies have revealed intramembrane proteolysis to be an additional mechanism that can extract transmembrane segments. Here, we review these two principles in membrane protein degradation and discuss how intramembrane proteolysis, which introduces an irreversible step in protein dislocation, is used to drive regulated protein turnover.
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Affiliation(s)
- Dönem Avci
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Marius K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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27
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TRC8-dependent degradation of hepatitis C virus immature core protein regulates viral propagation and pathogenesis. Nat Commun 2016; 7:11379. [PMID: 27142248 PMCID: PMC4857398 DOI: 10.1038/ncomms11379] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 03/21/2016] [Indexed: 01/07/2023] Open
Abstract
Signal-peptide peptidase (SPP) is an intramembrane protease that participates in the production of the mature core protein of hepatitis C virus (HCV). Here we show that SPP inhibition reduces the production of infectious HCV particles and pathogenesis. The immature core protein produced in SPP-knockout cells or by treatment with an SPP inhibitor is quickly degraded by the ubiquitin–proteasome pathway. Oral administration of the SPP inhibitor to transgenic mice expressing HCV core protein (CoreTg) reduces the expression of core protein and ameliorates insulin resistance and liver steatosis. Moreover, the haploinsufficiency of SPP in CoreTg has similar effects. TRC8, an E3 ubiquitin ligase, is required for the degradation of the immature core protein. The expression of the HCV core protein alters endoplasmic reticulum (ER) distribution and induces ER stress in SPP/TRC8 double-knockout cells. These data suggest that HCV utilizes SPP cleavage to circumvent the induction of ER stress in host cells. A cellular protease, SPP, participates in production of the mature core protein of hepatitis C virus (HCV). Here, the authors show in mouse models that SPP inhibition reduces viral propagation and pathogenesis via proteasomal degradation of the immature core protein mediated by the E3 ubiquitin ligase TRC8.
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Chapman DC, Stocki P, Williams DB. Cyclophilin C Participates in the US2-Mediated Degradation of Major Histocompatibility Complex Class I Molecules. PLoS One 2015; 10:e0145458. [PMID: 26691022 PMCID: PMC4686535 DOI: 10.1371/journal.pone.0145458] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 12/03/2015] [Indexed: 02/07/2023] Open
Abstract
Human cytomegalovirus uses a variety of mechanisms to evade immune recognition through major histocompatibility complex class I molecules. One mechanism mediated by the immunoevasin protein US2 causes rapid disposal of newly synthesized class I molecules by the endoplasmic reticulum-associated degradation pathway. Although several components of this degradation pathway have been identified, there are still questions concerning how US2 targets class I molecules for degradation. In this study we identify cyclophilin C, a peptidyl prolyl isomerase of the endoplasmic reticulum, as a component of US2-mediated immune evasion. Cyclophilin C could be co-isolated with US2 and with the class I molecule HLA-A2. Furthermore, it was required at a particular expression level since depletion or overexpression of cyclophilin C impaired the degradation of class I molecules. To better characterize the involvement of cyclophilin C in class I degradation, we used LC-MS/MS to detect US2-interacting proteins that were influenced by cyclophilin C expression levels. We identified malectin, PDIA6, and TMEM33 as proteins that increased in association with US2 upon cyclophilin C knockdown. In subsequent validation all were shown to play a functional role in US2 degradation of class I molecules. This was specific to US2 rather than general ER-associated degradation since depletion of these proteins did not impede the degradation of a misfolded substrate, the null Hong Kong variant of α1-antitrypsin.
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Affiliation(s)
- Daniel C. Chapman
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Pawel Stocki
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - David B. Williams
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Abstract
ER-associated degradation (ERAD) is a protein clearance mechanism by which misfolded, misassembled, or metabolically regulated proteins are specifically dislocated from the ER into the cytosol and degraded by the ubiquitin proteasome system. ERAD very likely evolved to maintain proteostasis and sterol homeostasis in the ER. However, the ironic truth is that membrane-penetrating transportation and protein degradation machineries in ERAD are preferably hijacked by exogenous pathogens such as viruses and toxins for their invasion and evasion from immunological surveillance. In this Review, we provide an overview of our current understanding of the pathogenic hijacking of the host cell ERAD, in which pathogens exploit the complex ERAD machinery in a variety of manners for their own use, suggesting flexibility and plasticity of the molecular machinery of ERAD.
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Abstract
E3 ubiquitin ligases play a central role in viral and cellular degradation of MHC-I. HCMV US2 and US11 hijack the mammalian ERAD machinery to induce MHC-I degradation. We identified the TRC8 and TMEM129 E3 ligases as crucial for US2/11 function. The US2/11 degradation hubs are flexible and enable viral evasion of different immune functions. Cellular quality control of MHC-I is controlled by the HRD1/SEL1L E3 ligase complex.
The human cytomegalovirus (HCMV) US2 and US11 gene products hijack mammalian ER-associated degradation (ERAD) to induce rapid degradation of major histocompatibility class I (MHC-I) molecules. The rate-limiting step in this pathway is thought to be the polyubiquitination of MHC-I by distinct host ERAD E3 ubiquitin ligases. TRC8 was identified as the ligase responsible for US2-mediated MHC-I degradation and shown to be required for the cleavage-dependent degradation of some tail-anchored proteins. In addition to MHC-I, plasma membrane profiling identified further immune receptors, which are also substrates for the US2/TRC8 complex. These include at least six α integrins, the coagulation factor thrombomodulin and the NK cell ligand CD112. US2’s use of specific HCMV-encoded adaptors makes it an adaptable viral degradation hub. US11-mediated degradation is MHC-I-specific and genetic screens have identified TMEM129, an uncharacterised RING-C2 E3 ligase, as responsible for US11-mediated degradation. In a unique auto-regulatory loop, US11 readily responds to changes in cellular expression of MHC-I. Free US11 either rebinds more MHC-I or is itself degraded by the HRD1/SEL1L E3 ligase complex. While virally encoded US2 and US11 appropriate mammalian ERAD, the MHC-I complex also undergoes stringent cellular quality control and misfolded MHC-I is degraded by the HRD1/SEL1L complex. We discuss the identification and central role of E3 ubiquitin ligases in ER quality control and viral degradation of the MHC-I chain.
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Affiliation(s)
- D J H van den Boomen
- Cambridge Institute for Medical Research, Department of Medicine, University of Cambridge, Cambridge CB2 0XY, UK.
| | - P J Lehner
- Cambridge Institute for Medical Research, Department of Medicine, University of Cambridge, Cambridge CB2 0XY, UK.
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31
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Ran Y, Ladd GZ, Ceballos-Diaz C, Jung JI, Greenbaum D, Felsenstein KM, Golde TE. Differential Inhibition of Signal Peptide Peptidase Family Members by Established γ-Secretase Inhibitors. PLoS One 2015; 10:e0128619. [PMID: 26046535 PMCID: PMC4457840 DOI: 10.1371/journal.pone.0128619] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 04/29/2015] [Indexed: 11/19/2022] Open
Abstract
The signal peptide peptidases (SPPs) are biomedically important proteases implicated as therapeutic targets for hepatitis C (human SPP, (hSPP)), plasmodium (Plasmodium SPP (pSPP)), and B-cell immunomodulation and neoplasia (signal peptide peptidase like 2a, (SPPL2a)). To date, no drug-like, selective inhibitors have been reported. We use a recombinant substrate based on the amino-terminus of BRI2 fused to amyloid β 1-25 (Aβ1-25) (FBA) to develop facile, cost-effective SPP/SPPL protease assays. Co-transfection of expression plasmids expressing the FBA substrate with SPP/SPPLs were conducted to evaluate cleavage, which was monitored by ELISA, Western Blot and immunoprecipitation/MALDI-TOF Mass spectrometry (IP/MS). No cleavage is detected in the absence of SPP/SPPL overexpression. Multiple γ-secretase inhibitors (GSIs) and (Z-LL)2 ketone differentially inhibited SPP/SPPL activity; for example, IC50 of LY-411,575 varied from 51±79 nM (on SPPL2a) to 5499±122 nM (on SPPL2b), while Compound E showed inhibition only on hSPP with IC50 of 1465±93 nM. Data generated were predictive of effects observed for endogenous SPPL2a cleavage of CD74 in a murine B-Cell line. Thus, it is possible to differentially inhibit SPP family members. These SPP/SPPL cleavage assays will expedite the search for selective inhibitors. The data also reinforce similarities between SPP family member cleavage and cleavage catalyzed by γ-secretase.
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Affiliation(s)
- Yong Ran
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine University of Florida, Gainesville, Florida, United States of America
- * E-mail: (YR); (TG)
| | - Gabriela Z. Ladd
- College of Pharmacy, University of Florida, Gainesville, Florida, United States of America
| | - Carolina Ceballos-Diaz
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine University of Florida, Gainesville, Florida, United States of America
| | - Joo In Jung
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine University of Florida, Gainesville, Florida, United States of America
| | - Doron Greenbaum
- Pennsylvania Drug Discovery Institute, Philadelphia, Pennsylvania, United States of America
| | - Kevin M. Felsenstein
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine University of Florida, Gainesville, Florida, United States of America
| | - Todd E. Golde
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine University of Florida, Gainesville, Florida, United States of America
- * E-mail: (YR); (TG)
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32
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Oliveira CC, van Hall T. Alternative Antigen Processing for MHC Class I: Multiple Roads Lead to Rome. Front Immunol 2015; 6:298. [PMID: 26097483 PMCID: PMC4457021 DOI: 10.3389/fimmu.2015.00298] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/22/2015] [Indexed: 12/31/2022] Open
Abstract
The well described conventional antigen-processing pathway is accountable for most peptides that end up in MHC class I molecules at the cell surface. These peptides experienced liberation by the proteasome and transport by the peptide transporter TAP. However, there are multiple roads that lead to Rome, illustrated by the increasing number of alternative processing pathways that have been reported during last years. Interestingly, TAP-deficient individuals do not succumb to viral infections, suggesting that CD8 T cell immunity is sufficiently supported by alternative TAP-independent processing pathways. To date, a diversity of viral and endogenous TAP-independent peptides have been identified in the grooves of different MHC class I alleles. Some of these peptides are not displayed by normal TAP-positive cells and we therefore called them TEIPP, for “T-cell epitopes associated with impaired peptide processing.” TEIPPs are hidden self-antigens, are derived from normal housekeeping proteins, and are processed via unconventional processing pathways. Per definition, TEIPPs are presented via TAP-independent pathways, but recent data suggest that part of this repertoire still depend on proteasome and metalloprotease activity. An exception is the C-terminal peptide of the endoplasmic reticulum (ER)-membrane-spanning ceramide synthase Trh4 that is surprisingly liberated by the signal peptide peptidase (SPP), the proteolytic enzyme involved in cleaving leader sequences. The intramembrane cleaving SPP is thereby an important contributor of TAP-independent peptides. Its family members, like the Alzheimer’s related presenilins, might contribute as well, according to our preliminary data. Finally, alternative peptide routing is an emerging field and includes processes like the unfolded protein response, the ER-associated degradation, and autophagy-associated vesicular pathways. These data convince us that there is a world to be discovered in the field of unconventional antigen processing.
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Affiliation(s)
- Cláudia C Oliveira
- Department of Clinical Oncology, Leiden University Medical Center , Leiden , Netherlands
| | - Thorbald van Hall
- Department of Clinical Oncology, Leiden University Medical Center , Leiden , Netherlands
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van de Weijer ML, Luteijn RD, Wiertz EJHJ. Viral immune evasion: Lessons in MHC class I antigen presentation. Semin Immunol 2015; 27:125-37. [PMID: 25887630 DOI: 10.1016/j.smim.2015.03.010] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/13/2015] [Indexed: 12/19/2022]
Abstract
The MHC class I antigen presentation pathway enables cells infected with intracellular pathogens to signal the presence of the invader to the immune system. Cytotoxic T lymphocytes are able to eliminate the infected cells through recognition of pathogen-derived peptides presented by MHC class I molecules at the cell surface. In the course of evolution, many viruses have acquired inhibitors that target essential stages of the MHC class I antigen presentation pathway. Studies on these immune evasion proteins reveal fascinating strategies used by viruses to elude the immune system. Viral immunoevasins also constitute great research tools that facilitate functional studies on the MHC class I antigen presentation pathway, allowing the investigation of less well understood routes, such as TAP-independent antigen presentation and cross-presentation of exogenous proteins. Viral immunoevasins have also helped to unravel more general cellular processes. For instance, basic principles of ER-associated protein degradation via the ubiquitin-proteasome pathway have been resolved using virus-induced degradation of MHC class I as a model. This review highlights how viral immunoevasins have increased our understanding of MHC class I-restricted antigen presentation.
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Affiliation(s)
| | - Rutger D Luteijn
- Medical Microbiology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Emmanuel J H J Wiertz
- Medical Microbiology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands.
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34
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Avci D, Fuchs S, Schrul B, Fukumori A, Breker M, Frumkin I, Chen CY, Biniossek M, Kremmer E, Schilling O, Steiner H, Schuldiner M, Lemberg M. The Yeast ER-Intramembrane Protease Ypf1 Refines Nutrient Sensing by Regulating Transporter Abundance. Mol Cell 2014; 56:630-40. [DOI: 10.1016/j.molcel.2014.10.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 06/19/2014] [Accepted: 10/09/2014] [Indexed: 02/08/2023]
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35
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Classical and non-classical MHC I molecule manipulation by human cytomegalovirus: so many targets—but how many arrows in the quiver? Cell Mol Immunol 2014; 12:139-53. [PMID: 25418469 PMCID: PMC4654289 DOI: 10.1038/cmi.2014.105] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 02/07/2023] Open
Abstract
Major mechanisms for the recognition of pathogens by immune cells have evolved to employ classical and non-classical major histocompatibility complex class I (MHC I) molecules. Classical MHC I molecules present antigenic peptide ligands on infected cells to CD8+ T cells, whereas a key function for non-classical MHC I molecules is to mediate inhibitory or activating stimuli in natural killer (NK) cells. The structural diversity of MHC I puts immense pressure on persisting viruses, including cytomegaloviruses. The very large coding capacity of the human cytomegalovirus allows it to express a whole arsenal of immunoevasive factors assigned to individual MHC class I targets. This review summarizes achievements from more than two decades of intense research on how human cytomegalovirus manipulates MHC I molecules and escapes elimination by the immune system.
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36
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Chen CY, Malchus NS, Hehn B, Stelzer W, Avci D, Langosch D, Lemberg MK. Signal peptide peptidase functions in ERAD to cleave the unfolded protein response regulator XBP1u. EMBO J 2014; 33:2492-506. [PMID: 25239945 DOI: 10.15252/embj.201488208] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Signal peptide peptidase (SPP) catalyzes intramembrane proteolysis of signal peptides at the endoplasmic reticulum (ER), but has also been suggested to play a role in ER-associated degradation (ERAD). Here, we show that SPP forms a complex with the ERAD factor Derlin1 and the E3 ubiquitin ligase TRC8 to cleave the unfolded protein response (UPR) regulator XBP1u. Cleavage occurs within a so far unrecognized type II transmembrane domain, which renders XBP1u as an SPP substrate through specific sequence features. Additionally, Derlin1 acts in the complex as a substrate receptor by recognizing the luminal tail of XBP1u. Remarkably, this interaction of Derlin1 with XBP1u obviates the need for ectodomain shedding prior to SPP cleavage, commonly required for intramembrane cuts. Furthermore, we show that XBP1u inhibits the UPR transcription factor XBP1s by targeting it toward proteasomal degradation. Thus, we identify an ERAD complex that controls the abundance of XBP1u and thereby tunes signaling through the UPR.
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Affiliation(s)
- Chia-yi Chen
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Nicole S Malchus
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Beate Hehn
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Walter Stelzer
- Lehrstuhl für Chemie der Biopolymere, Department für Biowissenschaftliche Grundlagen, Technische Universität München, Freising, Germany
| | - Dönem Avci
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Dieter Langosch
- Lehrstuhl für Chemie der Biopolymere, Department für Biowissenschaftliche Grundlagen, Technische Universität München, Freising, Germany
| | - Marius K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) DKFZ-ZMBH Allianz, Heidelberg, Germany
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37
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Boname JM, Bloor S, Wandel MP, Nathan JA, Antrobus R, Dingwell KS, Thurston TL, Smith DL, Smith JC, Randow F, Lehner PJ. Cleavage by signal peptide peptidase is required for the degradation of selected tail-anchored proteins. ACTA ACUST UNITED AC 2014; 205:847-62. [PMID: 24958774 PMCID: PMC4068138 DOI: 10.1083/jcb.201312009] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Intramembrane proteolytic cleavage by signal peptide peptidase is required for the turnover of some ER-resident, tail-anchored membrane proteins. The regulated turnover of endoplasmic reticulum (ER)–resident membrane proteins requires their extraction from the membrane lipid bilayer and subsequent proteasome-mediated degradation. Cleavage within the transmembrane domain provides an attractive mechanism to facilitate protein dislocation but has never been shown for endogenous substrates. To determine whether intramembrane proteolysis, specifically cleavage by the intramembrane-cleaving aspartyl protease signal peptide peptidase (SPP), is involved in this pathway, we generated an SPP-specific somatic cell knockout. In a stable isotope labeling by amino acids in cell culture–based proteomics screen, we identified HO-1 (heme oxygenase-1), the rate-limiting enzyme in the degradation of heme to biliverdin, as a novel SPP substrate. Intramembrane cleavage by catalytically active SPP provided the primary proteolytic step required for the extraction and subsequent proteasome-dependent degradation of HO-1, an ER-resident tail-anchored protein. SPP-mediated proteolysis was not limited to HO-1 but was required for the dislocation and degradation of additional tail-anchored ER-resident proteins. Our study identifies tail-anchored proteins as novel SPP substrates and a specific requirement for SPP-mediated intramembrane cleavage in protein turnover.
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Affiliation(s)
- Jessica M Boname
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, England, UK
| | - Stuart Bloor
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, England, UK
| | - Michal P Wandel
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK Division of Protein and Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - James A Nathan
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, England, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK
| | - Kevin S Dingwell
- Medical Research Council National Institute for Medical Research, London NW7 1AA, England, UK
| | - Teresa L Thurston
- Division of Protein and Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Duncan L Smith
- Cancer Research UK Manchester Institute, University of Manchester, Manchester M20 4B, England, UK
| | - James C Smith
- Medical Research Council National Institute for Medical Research, London NW7 1AA, England, UK
| | - Felix Randow
- Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, England, UK Division of Protein and Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Paul J Lehner
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, England, UK Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, England, UK
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38
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Abstract
Proteins and peptides are well-documented as useful marker adjuncts to cardiovascular clinical decision-making. Most markers measured derive from a defined, stable proprotein region of their respective gene. However, a neglected portion of preproproteins known as the signal peptide (SP) is also present in the circulation and may also present as a measurable marker. SPs were assumed to be degraded intracellularly after directing secretion, but a small, growing body of evidence is identifying SPs as not being degraded within and without cells. In this article, evidence for the persistence of SPs after translation is presented and their role as potential cardiovascular biomarkers is discussed.
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39
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Koenig PA, Ploegh HL. Protein quality control in the endoplasmic reticulum. F1000PRIME REPORTS 2014; 6:49. [PMID: 25184039 PMCID: PMC4108957 DOI: 10.12703/p6-49] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
THE TOPOLOGICAL BARRIERS DEFINED BY BIOLOGICAL MEMBRANES ARE NOT IMPERMEABLE: from small solutes to intact proteins, specialized transport and translocation mechanisms adjust to the cell's needs. Here, we review the removal of unwanted proteins from the endoplasmic reticulum (ER) and emphasize the need to extend observations from tissue culture models and simple eukaryotes to studies in whole animals. The variation in protein production and composition that characterizes different cell types and tissues requires tailor-made solutions to exert proper control over both protein synthesis and breakdown. The ER is an organelle essential to achieve and maintain such homeostasis.
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Affiliation(s)
- Paul-Albert Koenig
- Klinikum rechts der Isar, Technische Universität München, Institut für Klinische Chemie und Pathobiochemie, Ismaninger Straße22, 81675 MünchenGermany
| | - Hidde L. Ploegh
- Whitehead Institute for Biomedical Research9 Cambridge Center, Cambridge, 02142 MAUSA
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40
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Byun H, Gou Y, Zook A, Lozano MM, Dudley JP. ERAD and how viruses exploit it. Front Microbiol 2014; 5:330. [PMID: 25071743 PMCID: PMC4080680 DOI: 10.3389/fmicb.2014.00330] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 06/16/2014] [Indexed: 01/09/2023] Open
Abstract
Endoplasmic reticulum (ER)-associated degradation (ERAD) is a universally important process among eukaryotic cells. ERAD is necessary to preserve cell integrity since the accumulation of defective proteins results in diseases associated with neurological dysfunction, cancer, and infections. This process involves recognition of misfolded or misassembled proteins that have been translated in association with ER membranes. Recognition of ERAD substrates leads to their extraction through the ER membrane (retrotranslocation or dislocation), ubiquitination, and destruction by cytosolic proteasomes. This review focuses on ERAD and its components as well as how viruses use this process to promote their replication and to avoid the immune response.
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Affiliation(s)
- Hyewon Byun
- Department of Molecular Biosciences, Center for Infectious Diseases and Institute for Cellular and Molecular Biology, The University of Texas at Austin Austin, TX, USA
| | - Yongqiang Gou
- Department of Molecular Biosciences, Center for Infectious Diseases and Institute for Cellular and Molecular Biology, The University of Texas at Austin Austin, TX, USA
| | - Adam Zook
- Department of Molecular Biosciences, Center for Infectious Diseases and Institute for Cellular and Molecular Biology, The University of Texas at Austin Austin, TX, USA
| | - Mary M Lozano
- Department of Molecular Biosciences, Center for Infectious Diseases and Institute for Cellular and Molecular Biology, The University of Texas at Austin Austin, TX, USA
| | - Jaquelin P Dudley
- Department of Molecular Biosciences, Center for Infectious Diseases and Institute for Cellular and Molecular Biology, The University of Texas at Austin Austin, TX, USA
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41
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Ruggiano A, Foresti O, Carvalho P. Quality control: ER-associated degradation: protein quality control and beyond. ACTA ACUST UNITED AC 2014; 204:869-79. [PMID: 24637321 PMCID: PMC3998802 DOI: 10.1083/jcb.201312042] [Citation(s) in RCA: 441] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Even with the assistance of many cellular factors, a significant fraction of newly synthesized proteins ends up misfolded. Cells evolved protein quality control systems to ensure that these potentially toxic species are detected and eliminated. The best characterized of these pathways, the ER-associated protein degradation (ERAD), monitors the folding of membrane and secretory proteins whose biogenesis takes place in the endoplasmic reticulum (ER). There is also increasing evidence that ERAD controls other ER-related functions through regulated degradation of certain folded ER proteins, further highlighting the role of ERAD in cellular homeostasis.
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Affiliation(s)
- Annamaria Ruggiano
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 88 08003 Barcelona, Spain
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42
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43
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Abstract
Cells use messenger RNAs (mRNAs) to ensure the accurate dissemination of genetic information encoded by DNA. Given that mRNAs largely direct the synthesis of a critical effector of cellular phenotype, i.e., proteins, tight regulation of both the quality and quantity of mRNA is a prerequisite for effective cellular homeostasis. Here, we review nonsense-mediated mRNA decay (NMD), which is the best-characterized posttranscriptional quality control mechanism that cells have evolved in their cytoplasm to ensure transcriptome fidelity. We use protein quality control as a conceptual framework to organize what is known about NMD, highlighting overarching similarities between these two polymer quality control pathways, where the protein quality control and NMD pathways intersect, and how protein quality control can suggest new avenues for research into mRNA quality control.
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Affiliation(s)
- Maximilian Wei-Lin Popp
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642;
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44
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Binding of HSV-1 glycoprotein K (gK) to signal peptide peptidase (SPP) is required for virus infectivity. PLoS One 2014; 9:e85360. [PMID: 24465545 PMCID: PMC3896391 DOI: 10.1371/journal.pone.0085360] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/20/2013] [Indexed: 11/19/2022] Open
Abstract
Glycoprotein K (gK) is a virion envelope protein of herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), which plays important roles in virion entry, morphogenesis and egress. Two-hybrid and pull-down assays were utilized to demonstrate that gK and no other HSV-1 genes specifically binds to signal peptide peptidase (SPP), also known as minor histocompatibility antigen H13. SPP dominant negative mutants, shRNA against SPP significantly reduced HSV-1 replication in vitro. SPP also affected lysosomes and ER responses to HSV-1 infection. Thus, in this study we have shown for the first time that gK, despite its role in fusion and egress, is also involved in binding the cytoplasmic protein SPP. These results also suggest that SPP plays an important role in viral replication and possibly virus pathogenesis. This makes SPP unique in that its function appears to be required by the virus as no other protein can compensate its loss in terms of viral replication.
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45
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Sibley LD. The roles of intramembrane proteases in protozoan parasites. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2908-15. [PMID: 24099008 DOI: 10.1016/j.bbamem.2013.04.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/02/2013] [Accepted: 04/11/2013] [Indexed: 11/30/2022]
Abstract
Intramembrane proteolysis is widely conserved throughout different forms of life, with three major types of proteases being known for their ability to cleave peptide bonds directly within the transmembrane domains of their substrates. Although intramembrane proteases have been extensively studied in humans and model organisms, they have only more recently been investigated in protozoan parasites, where they turn out to play important and sometimes unexpected roles. Signal peptide peptidases are involved in endoplasmic reticulum (ER) quality control and signal peptide degradation from exported proteins. Recent studies suggest that repurposing inhibitors developed for blocking presenilins may be useful for inhibiting the growth of Plasmodium, and possibly other protozoan parasites, by blocking signal peptide peptidases. Rhomboid proteases, originally described in the fly, are also widespread in parasites, and are especially expanded in apicomplexans. Their study in parasites has revealed novel roles that expand our understanding of how these proteases function. Within this diverse group of parasites, rhomboid proteases contribute to processing of adhesins involved in attachment, invasion, intracellular replication, phagocytosis, and immune evasion, placing them at the vertex of host-parasite interactions. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- L David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Voss M, Schröder B, Fluhrer R. Mechanism, specificity, and physiology of signal peptide peptidase (SPP) and SPP-like proteases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2828-39. [PMID: 24099004 DOI: 10.1016/j.bbamem.2013.03.033] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 03/25/2013] [Accepted: 03/29/2013] [Indexed: 01/09/2023]
Abstract
Signal peptide peptidase (SPP) and the homologous SPP-like (SPPL) proteases SPPL2a, SPPL2b, SPPL2c and SPPL3 belong to the family of GxGD intramembrane proteases. SPP/SPPLs selectively cleave transmembrane domains in type II orientation and do not require additional co-factors for proteolytic activity. Orthologues of SPP and SPPLs have been identified in other vertebrates, plants, and eukaryotes. In line with their diverse subcellular localisations ranging from the ER (SPP, SPPL2c), the Golgi (SPPL3), the plasma membrane (SPPL2b) to lysosomes/late endosomes (SPPL2a), the different members of the SPP/SPPL family seem to exhibit distinct functions. Here, we review the substrates of these proteases identified to date as well as the current state of knowledge about the physiological implications of these proteolytic events as deduced from in vivo studies. Furthermore, the present knowledge on the structure of intramembrane proteases of the SPP/SPPL family, their cleavage mechanism and their substrate requirements are summarised. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Matthias Voss
- Adolf Butenandt Institute for Biochemistry, Ludwig-Maximilians University Munich, Schillerstr. 44, 80336 Munich, Germany
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Ye J. Roles of regulated intramembrane proteolysis in virus infection and antiviral immunity. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1828:2926-32. [PMID: 24099010 PMCID: PMC3837687 DOI: 10.1016/j.bbamem.2013.05.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 01/24/2023]
Abstract
Regulated intramembrane proteolysis (RIP) is a signaling mechanism through which transmembrane precursor proteins are cleaved to liberate their cytoplasmic and/or luminal/extracellular fragments from membranes so that these fragments are able to function at a new location. Recent studies have indicated that this proteolytic reaction plays an important role in host-virus interaction. On one hand, RIP transfers the signal from the endoplasmic reticulum (ER) to nucleus to activate antiviral genes in response to alteration of the ER caused by viral infection. On the other hand, RIP can be hijacked by virus to process transmembrane viral protein precursors and to destroy transmembrane antiviral proteins. Understanding this Yin and Yang side of RIP may lead to new strategies to combat viral infection. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Jin Ye
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9046, USA.
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Feige MJ, Hendershot LM. Quality control of integral membrane proteins by assembly-dependent membrane integration. Mol Cell 2013; 51:297-309. [PMID: 23932713 DOI: 10.1016/j.molcel.2013.07.013] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/28/2013] [Accepted: 07/09/2013] [Indexed: 02/07/2023]
Abstract
Cell-surface multiprotein complexes are synthesized in the endoplasmic reticulum (ER), where they undergo cotranslational membrane integration and assembly. The quality control mechanisms that oversee these processes remain poorly understood. We show that less hydrophobic transmembrane (TM) regions derived from several single-pass TM proteins can enter the ER lumen completely. Once mislocalized, they are recognized by the Hsp70 chaperone BiP. In a detailed analysis for one of these proteins, the αβT cell receptor (αβTCR), we show that unassembled ER-lumenal subunits are rapidly degraded, whereas specific subunit interactions en route to the native receptor promote membrane integration of the less hydrophobic TM segments, thereby stabilizing the protein. For the TCR α chain, both complete ER import and subunit assembly depend on the same pivotal residue in its TM region. Thus, membrane integration linked to protein assembly allows cellular quality control of membrane proteins and connects the lumenal ER chaperone machinery to membrane protein biogenesis.
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Affiliation(s)
- Matthias J Feige
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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Oliveira CC, Querido B, Sluijter M, de Groot AF, van der Zee R, Rabelink MJWE, Hoeben RC, Ossendorp F, van der Burg SH, van Hall T. New role of signal peptide peptidase to liberate C-terminal peptides for MHC class I presentation. THE JOURNAL OF IMMUNOLOGY 2013; 191:4020-8. [PMID: 24048903 DOI: 10.4049/jimmunol.1301496] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The signal peptide peptidase (SPP) is an intramembrane cleaving aspartyl protease involved in release of leader peptide remnants from the endoplasmic reticulum membrane, hence its name. We now found a new activity of SPP that mediates liberation of C-terminal peptides. In our search for novel proteolytic enzymes involved in MHC class I (MHC-I) presentation, we found that SPP generates the C-terminal peptide-epitope of a ceramide synthase. The display of this immunogenic peptide-MHC-I complex at the cell surface was independent of conventional processing components like proteasome and peptide transporter TAP. Absence of TAP activity even increased the MHC-I presentation of this Ag. Mutagenesis studies revealed the crucial role of the C-terminal location of the epitope and "helix-breaking" residues in the transmembrane region just upstream of the peptide, indicating that SPP directly liberated the minimal 9-mer peptide. Moreover, silencing of SPP and its family member SPPL2a led to a general reduction of surface peptide-MHC-I complexes, underlining the involvement of these enzymes in Ag processing and presentation.
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Affiliation(s)
- Cláudia C Oliveira
- Department of Clinical Oncology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands
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Olzmann JA, Kopito RR, Christianson JC. The mammalian endoplasmic reticulum-associated degradation system. Cold Spring Harb Perspect Biol 2013; 5:cshperspect.a013185. [PMID: 23232094 DOI: 10.1101/cshperspect.a013185] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The endoplasmic reticulum (ER) is the site of synthesis for nearly one-third of the eukaryotic proteome and is accordingly endowed with specialized machinery to ensure that proteins deployed to the distal secretory pathway are correctly folded and assembled into native oligomeric complexes. Proteins failing to meet this conformational standard are degraded by ER-associated degradation (ERAD), a complex process through which folding-defective proteins are selected and ultimately degraded by the ubiquitin-proteasome system. ERAD proceeds through four tightly coupled steps involving substrate selection, dislocation across the ER membrane, covalent conjugation with polyubiquitin, and proteasomal degradation. The ERAD machinery shows a modular organization with central ER membrane-embedded ubiquitin ligases linking components responsible for recognition in the ER lumen to the ubiquitin-proteasome system in the cytoplasm. The core ERAD machinery is highly conserved among eukaryotes and much of our basic understanding of ERAD organization has been derived from genetic and biochemical studies of yeast. In this article we discuss how the core ERAD machinery is organized in mammalian cells.
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Affiliation(s)
- James A Olzmann
- Department of Biology, Stanford University, Stanford, California 94305, USA
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