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Yang H, Li Z, Wang Z, Zhang X, Dai X, Zhou G, Ding Q. Histocompatibility Minor 13 (HM13), targeted by miR-760, exerts oncogenic role in breast cancer by suppressing autophagy and activating PI3K-AKT-mTOR pathway. Cell Death Dis 2022; 13:728. [PMID: 36153332 PMCID: PMC9509374 DOI: 10.1038/s41419-022-05154-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 07/29/2022] [Accepted: 08/01/2022] [Indexed: 01/21/2023]
Abstract
Histocompatibility Minor 13 (HM13) is reported to participate in regulating multiple cancers. In the present study, we uncovered that HM13 was highly expressed in breast cancer and correlated with worse prognosis. Downregulation of HM13 could suppress breast cancer cell proliferation and metastasis abilities. Tumorigenicity mediated by HM13 was also observed in the xenograft model. Knockdown of HM13 could activate autophagy by inducing endoplasmic reticulum (ER) stress. Moreover, further experiments demonstrated that downregulated HM13 could inhibit PI3K-AKT-mTOR pathway. We then verified that HM13 was a direct target of miR-760 functioned as a tumor -suppressor in breast cancer. And the tumor suppressive effects of miR-760 could be partially reversed by HM13. Taken together, these findings elucidated that HM13, targeted by miR-760, could play an oncogenic role in breast cancer by inducing autophagic inhibition and facilitating PI3K-AKT-mTOR pathway. Our findings suggested HM13 could act as a novel therapeutic target candidate for breast cancer and supported the idea that autophagy inducers might represent a new approach to treat breast cancer.
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Affiliation(s)
- Haiyan Yang
- grid.412676.00000 0004 1799 0784Jiangsu Breast Disease Center, the First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu 210029 PR China
| | - Zhi Li
- grid.89957.3a0000 0000 9255 8984Department of Breast and Thyroid Surgery, Huai’an First People’s Hospital, Nanjing Medical University, Huai’an, Jiangsu 223399 PR China
| | - Zhangwei Wang
- grid.412676.00000 0004 1799 0784Jiangsu Breast Disease Center, the First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu 210029 PR China
| | - Xu Zhang
- grid.412676.00000 0004 1799 0784Jiangsu Breast Disease Center, the First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu 210029 PR China
| | - Xinyuan Dai
- grid.412676.00000 0004 1799 0784Jiangsu Breast Disease Center, the First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu 210029 PR China
| | - Guoren Zhou
- grid.452509.f0000 0004 1764 4566Department of Oncology, Jiangsu Cancer Hospital & the Affiliated Cancer Hospital of Nanjing Medical University & Jiangsu Institute of Cancer Research, Nanjing, Jiangsu 210009 PR China
| | - Qiang Ding
- grid.412676.00000 0004 1799 0784Jiangsu Breast Disease Center, the First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu 210029 PR China
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O’Keefe S, Roebuck QP, Nakagome I, Hirono S, Kato A, Nash R, High S. Characterizing the selectivity of ER α-glucosidase inhibitors. Glycobiology 2019; 29:530-542. [PMID: 30976784 PMCID: PMC6583763 DOI: 10.1093/glycob/cwz029] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/15/2019] [Accepted: 04/08/2019] [Indexed: 02/06/2023] Open
Abstract
The endoplasmic reticulum (ER) contains both α-glucosidases and α-mannosidases which process the N-linked oligosaccharides of newly synthesized glycoproteins and thereby facilitate polypeptide folding and glycoprotein quality control. By acting as structural mimetics, iminosugars can selectively inhibit these ER localized α-glycosidases, preventing N-glycan trimming and providing a molecular basis for their therapeutic applications. In this study, we investigate the effects of a panel of nine iminosugars on the actions of ER luminal α-glucosidase I and α-glucosidase II. Using ER microsomes to recapitulate authentic protein N-glycosylation and oligosaccharide processing, we identify five iminosugars that selectively inhibit N-glycan trimming. Comparison of their inhibitory activities in ER microsomes against their effects on purified ER α-glucosidase II, suggests that 3,7a-diepi-alexine acts as a selective inhibitor of ER α-glucosidase I. The other active iminosugars all inhibit α-glucosidase II and, having identified 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) as the most effective of these compounds, we use in silico modeling to understand the molecular basis for this enhanced activity. Taken together, our work identifies the C-3 substituted pyrrolizidines casuarine and 3,7a-diepi-alexine as promising "second-generation" iminosugar inhibitors.
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Affiliation(s)
- Sarah O’Keefe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Quentin P Roebuck
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Izumi Nakagome
- School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Shuichi Hirono
- School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Atsushi Kato
- Department of Hospital Pharmacy, University of Toyama, 2630 Sugitani, Toyama, Japan
| | - Robert Nash
- PhytoQuest Ltd, Plas Gogerddan, Aberystwyth, Ceredigion, UK
| | - Stephen High
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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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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4
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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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5
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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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Baldwin M, Russo C, Li X, Chishti AH. Plasmodium falciparum signal peptide peptidase cleaves malaria heat shock protein 101 (HSP101). Implications for gametocytogenesis. Biochem Biophys Res Commun 2014; 450:1427-32. [PMID: 25017910 DOI: 10.1016/j.bbrc.2014.07.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 07/02/2014] [Indexed: 10/25/2022]
Abstract
Previously we described the identification of a Plasmodium falciparum signal peptide peptidase (PfSPP) functioning at the blood stage of malaria infection. Our studies also demonstrated that mammalian SPP inhibitors prevent malaria parasite growth at the late-ring/early trophozoite stage of intra-erythrocytic development. Consistent with its role in development, we tested the hypothesis that PfSPP functions at the endoplasmic reticulum of P.falciparum where it cleaves membrane-bound signal peptides generated following the enzyme activity of signal peptidase. The localization of PfSPP to the endoplasmic reticulum was confirmed by immunofluorescence microscopy and immunogold electron microscopy. Biochemical analysis indicated the existence of monomer and dimer forms of PfSPP in the parasite lysate. A comprehensive bioinformatics screen identified several candidate PfSPP substrates in the parasite genome. Using an established transfection based in vivo luminescence assay, malaria heat shock protein 101 (HSP101) was identified as a substrate of PfSPP, and partial inhibition of PfSPP correlated with the emergence of gametocytes. This finding unveils the first known substrate of PfSPP, and provides new perspectives for the function of intra-membrane proteolysis at the erythrocyte stage of malaria parasite life cycle.
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Affiliation(s)
- Michael Baldwin
- Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Crystal Russo
- Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Xuerong Li
- Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Athar H Chishti
- Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States; Sackler School of Graduate Biomedical Sciences, Programs in Physiology, Pharmacology, and Microbiology, Tufts University School of Medicine, Boston, MA 02111, United States.
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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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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: 96] [Impact Index Per Article: 8.7] [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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9
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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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10
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Targeting the ERAD pathway via inhibition of signal peptide peptidase for antiparasitic therapeutic design. Proc Natl Acad Sci U S A 2012; 109:21486-91. [PMID: 23236186 DOI: 10.1073/pnas.1216016110] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Early secretory and endoplasmic reticulum (ER)-localized proteins that are terminally misfolded or misassembled are degraded by a ubiquitin- and proteasome-mediated process known as ER-associated degradation (ERAD). Protozoan pathogens, including the causative agents of malaria, toxoplasmosis, trypanosomiasis, and leishmaniasis, contain a minimal ERAD network relative to higher eukaryotic cells, and, because of this, we observe that the malaria parasite Plasmodium falciparum is highly sensitive to the inhibition of components of this protein quality control system. Inhibitors that specifically target a putative protease component of ERAD, signal peptide peptidase (SPP), have high selectivity and potency for P. falciparum. By using a variety of methodologies, we validate that SPP inhibitors target P. falciparum SPP in parasites, disrupt the protein's ability to facilitate degradation of unstable proteins, and inhibit its proteolytic activity. These compounds also show low nanomolar activity against liver-stage malaria parasites and are also equipotent against a panel of pathogenic protozoan parasites. Collectively, these data suggest ER quality control as a vulnerability of protozoan parasites, and that SPP inhibition may represent a suitable transmission blocking antimalarial strategy and potential pan-protozoan drug target.
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11
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Guerriero CJ, Brodsky JL. The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology. Physiol Rev 2012; 92:537-76. [PMID: 22535891 DOI: 10.1152/physrev.00027.2011] [Citation(s) in RCA: 301] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.
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Affiliation(s)
- Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, PA 15260, USA
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12
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Lu SHJ, Jeon AHW, Schmitt-Ulms G, Qamar S, Dodd R, McDonald B, Li Y, Meadows W, Cox K, Bohm C, Chen F, Fraser P, George-Hyslop PS. Vigilin interacts with signal peptide peptidase. Proteome Sci 2012; 10:33. [PMID: 22607704 PMCID: PMC3490818 DOI: 10.1186/1477-5956-10-33] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 05/04/2012] [Indexed: 11/11/2022] Open
Abstract
Background Signal peptide peptidase (SPP), a member of the presenilin-like intra-membrane cleaving aspartyl protease family, migrates on Blue Native (BN) gels as 100 kDa, 200 kDa and 450 kDa species. SPP has recently been implicated in other non-proteolytic functions such as retro-translocation of MHC Class I molecules and binding of misfolded proteins in the endoplasmic reticulum (ER). These high molecular weight SPP complexes might contain additional proteins that regulate the proteolytic activity of SPP or support its non-catalytic functions. Results In this study, an unbiased iTRAQ-labeling mass spectrometry approach was used to identify SPP-interacting proteins. We found that vigilin, a ubiquitous multi-KH domain containing cytoplasmic protein involved in RNA binding and protein translation control, selectively enriched with SPP. Vigilin interacted with SPP and both proteins co-localized in restricted intracellular domains near the ER, biochemically co-fractionated and were part of the same 450 kDa complex on BN gels. However, vigilin does not alter the protease activity of SPP, suggesting that the SPP-vigilin interaction might be involved in the non-proteolytic functions of SPP. Conclusions We have identified and validated vigilin as a novel interacting partner of SPP that could play an important role in the non-proteolytic functions of SPP. This data adds further weight to the idea that intramembrane-cleaving aspartyl proteases, such as presenilin and SPPs, could have other functions besides the proteolysis of short membrane stubs.
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Affiliation(s)
- Stephen Hsueh-Jeng Lu
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Hills Road, England, Cambridge, CB2 0XY, United Kingdom.
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13
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Post-liberation cleavage of signal peptides is catalyzed by the site-2 protease (S2P) in bacteria. Proc Natl Acad Sci U S A 2011; 108:13740-5. [PMID: 21810987 DOI: 10.1073/pnas.1108376108] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A signal peptide (SP) is cleaved off from presecretory proteins by signal peptidase during or immediately after insertion into the membrane. In metazoan cells, the cleaved SP then receives proteolysis by signal peptide peptidase, an intramembrane-cleaving protease (I-CLiP). However, bacteria lack any signal peptide peptidase member I-CLiP, and little is known about the metabolic fate of bacterial SPs. Here we show that Escherichia coli RseP, an site-2 protease (S2P) family I-CLiP, introduces a cleavage into SPs after their signal peptidase-mediated liberation from preproteins. A Bacillus subtilis S2P protease, RasP, is also shown to be involved in SP cleavage. These results uncover a physiological role of bacterial S2P proteases and update the basic knowledge about the fate of signal peptides in bacterial cells.
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14
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Miyashita H, Maruyama Y, Isshiki H, Osawa S, Ogura T, Mio K, Sato C, Tomita T, Iwatsubo T. Three-dimensional structure of the signal peptide peptidase. J Biol Chem 2011; 286:26188-97. [PMID: 21636854 DOI: 10.1074/jbc.m111.260273] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal peptide peptidase (SPP) is an atypical aspartic protease that hydrolyzes peptide bonds within the transmembrane domain of substrates and is implicated in several biological and pathological functions. Here, we analyzed the structure of human SPP by electron microscopy and reconstructed the three-dimensional structure at a resolution of 22 Å. Enzymatically active SPP forms a slender, bullet-shaped homotetramer with dimensions of 85 × 85 × 130 Å. The SPP complex has four concaves on the rhombus-like sides, connected to a large chamber inside the molecule. Intriguingly, the N-terminal region of SPP is sufficient for the tetrameric assembly. Moreover, overexpression of the N-terminal region inhibited the formation of the endogenous SPP tetramer and the proteolytic activity within cells. These data suggest that the homotetramer is the functional unit of SPP and that its N-terminal region, which works as the structural scaffold, has a novel modulatory function for the intramembrane-cleaving activity of SPP.
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Affiliation(s)
- Hiroyuki Miyashita
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
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15
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Signal peptide peptidase (SPP) assembles with substrates and misfolded membrane proteins into distinct oligomeric complexes. Biochem J 2010; 427:523-34. [PMID: 20196774 PMCID: PMC2860808 DOI: 10.1042/bj20091005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
SPP (signal peptide peptidase) is an aspartyl intramembrane cleaving protease, which processes a subset of signal peptides, and is linked to the quality control of ER (endoplasmic reticulum) membrane proteins. We analysed SPP interactions with signal peptides and other membrane proteins by co-immunoprecipitation assays. We found that SPP interacts specifically and tightly with a large range of newly synthesized membrane proteins, including signal peptides, preproteins and misfolded membrane proteins, but not with all co-expressed type II membrane proteins. Signal peptides are trapped by the catalytically inactive SPP mutant SPPD/A. Preproteins and misfolded membrane proteins interact with both SPP and the SPPD/A mutant, and are not substrates for SPP-mediated intramembrane proteolysis. Proteins interacting with SPP are found in distinct complexes of different sizes. A signal peptide is mainly trapped in a 200 kDa SPP complex, whereas a preprotein is predominantly found in a 600 kDa SPP complex. A misfolded membrane protein is detected in 200, 400 and 600 kDa SPP complexes. We conclude that SPP not only processes signal peptides, but also collects preproteins and misfolded membrane proteins that are destined for disposal.
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16
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Protein disulphide isomerase is required for signal peptide peptidase-mediated protein degradation. EMBO J 2009; 29:363-75. [PMID: 19942855 DOI: 10.1038/emboj.2009.359] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 11/04/2009] [Indexed: 11/08/2022] Open
Abstract
The human cytomegalovirus glycoprotein US2 induces dislocation of MHC class I heavy chains from the endoplasmic reticulum (ER) into the cytosol and targets them for proteasomal degradation. Signal peptide peptidase (SPP) has been shown to be integral for US2-induced dislocation of MHC class I heavy chains although its mechanism of action remains poorly understood. Here, we show that knockdown of protein disulphide isomerase (PDI) by RNA-mediated interference inhibited the degradation of MHC class I molecules catalysed by US2 but not by its functional homolog US11. Overexpression of the substrate-binding mutant of PDI, but not the catalytically inactive mutant, dominant-negatively inhibited US2-mediated dislocation of MHC class I molecules by preventing their release from US2. Furthermore, PDI associated with SPP independently of US2 and knockdown of PDI inhibited SPP-mediated degradation of CD3delta but not Derlin-1-dependent degradation of CFTR DeltaF508. Together, our data suggest that PDI is a component of the SPP-mediated ER-associated degradation machinery.
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17
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Koizumi M, Momoeda M, Hiroi H, Nakazawa F, Nakae H, Ohno T, Yano T, Taketani Y. Inhibition of proteases involved in embryo implantation by cholesterol sulfate. Hum Reprod 2009; 25:192-7. [DOI: 10.1093/humrep/dep370] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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18
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Cross BCS, High S. Dissecting the physiological role of selective transmembrane-segment retention at the ER translocon. J Cell Sci 2009; 122:1768-77. [PMID: 19417003 DOI: 10.1242/jcs.046094] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The membrane integration of polytopic proteins is coordinated at the endoplasmic reticulum (ER) by the conserved Sec61 translocon, which facilitates the lateral release of transmembrane (TM) segments into the lipid phase during polypeptide translocation. Here we use a site-specific crosslinking strategy to study the membrane integration of a new model protein and show that the TM segments of the P2X2 receptor are retained at the Sec61 complex for the entire duration of the biosynthetic process. This extremely prolonged association implicates the Sec61 complex in the regulation of the membrane integration process, and we use both in vitro and in vivo analyses to study this effect further. TM-segment retention depends on the association of the ribosome with the Sec61 complex, and complete lateral exit of the P2X2 TM segments was only induced by the artificial termination of translation. In the event of the premature release of P2X2 TM1 from the ER translocon, the truncated polypeptide fragment was to found aggregate in the ER membrane, suggesting a distinct physiological requirement for the delayed release of TM segments from the ER translocon site.
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Affiliation(s)
- Benedict C S Cross
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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19
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Han S, Green L, Schnell DJ. The signal peptide peptidase is required for pollen function in Arabidopsis. PLANT PHYSIOLOGY 2009; 149:1289-1301. [PMID: 19168645 PMCID: PMC2649412 DOI: 10.1104/pp.108.130252] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Accepted: 01/20/2009] [Indexed: 05/27/2023]
Abstract
The Signal Peptide Peptidases (SPP) are members of the Intramembrane Cleaving Proteases, which are involved in an array of protein-processing and intracellular signaling events in animals. Arabidopsis (Arabidopsis thaliana) has six genes encoding SPP-like proteins, the physiological functions of which are unknown. As a first step in defining the roles of the SPPs in plants, we examined the distribution and activities of Arabidopsis SPP (AtSPP; accession no. At2g03120), the SPP-like gene with the highest degree of similarity to human SPP. The protease is expressed at low levels throughout the plant, with the highest levels in emerging leaves, roots, and floral tissues. Homozygous plants carrying a T-DNA insertion mutation in AtSPP, spp-2, could not be recovered, and transmission of the mutant allele through pollen was reduced to less than 2% in reciprocal cross experiments. Although viable, pollen from spp-2 heterozygous plants exhibited a 50% reduction in germination rate and a disruption in male germ unit organization. These data demonstrate that AtSPP is required for male gametophyte development and pollen maturation in Arabidopsis.
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Affiliation(s)
- Sungwon Han
- Department of Biochemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA
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20
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Robakis T, Bak B, Lin SH, Bernard DJ, Scheiffele P. An internal signal sequence directs intramembrane proteolysis of a cellular immunoglobulin domain protein. J Biol Chem 2008; 283:36369-76. [PMID: 18981173 DOI: 10.1074/jbc.m807527200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Precursor proteolysis is a crucial mechanism for regulating protein structure and function. Signal peptidase (SP) is an enzyme with a well defined role in cleaving N-terminal signal sequences but no demonstrated function in the proteolysis of cellular precursor proteins. We provide evidence that SP mediates intraprotein cleavage of IgSF1, a large cellular Ig domain protein that is processed into two separate Ig domain proteins. In addition, our results suggest the involvement of signal peptide peptidase (SPP), an intramembrane protease, which acts on substrates that have been previously cleaved by SP. We show that IgSF1 is processed through sequential proteolysis by SP and SPP. Cleavage is directed by an internal signal sequence and generates two separate Ig domain proteins from a polytopic precursor. Our findings suggest that SP and SPP function are not restricted to N-terminal signal sequence cleavage but also contribute to the processing of cellular transmembrane proteins.
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Affiliation(s)
- Thalia Robakis
- Department of Physiology & Cellular Biophysics, Columbia University, New York, New York 10032, USA
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21
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Targett-Adams P, Hope G, Boulant S, McLauchlan J. Maturation of hepatitis C virus core protein by signal peptide peptidase is required for virus production. J Biol Chem 2008; 283:16850-9. [PMID: 18424431 DOI: 10.1074/jbc.m802273200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Complete maturation of hepatitis C virus (HCV) core protein requires coordinate cleavage by signal peptidase and an intramembrane protease, signal peptide peptidase. We show that reducing the intracellular levels of signal peptide peptidase lowers the titer of infectious virus released from cells, indicating that it plays an important role in virus production. Proteolysis by the enzyme at a signal peptide between core and the E1 glycoprotein is needed to permit targeting of core to lipid droplets. From mutagenesis studies, introducing mutations into the core-E1 signal peptide delayed the appearance of signal peptide peptidase-processed core until between 48 and 72 h after the beginning of the infectious cycle. Accumulation of mature core at these times coincided with its localization to lipid droplets and a rise in titer of infectious HCV. Therefore, processing of core by signal peptide peptidase is a critical event in the virus life cycle. To study the stage in virus production that may be blocked by interfering with intramembrane cleavage of core, we examined the distribution of viral RNA in cells harboring the core-E1 signal peptide mutant. Results revealed that colocalization of core with HCV RNA required processing of the protein by signal peptide peptidase. Our findings provide new insights into the sequence requirements for proteolysis by signal peptide peptidase. Moreover, they offer compelling evidence for a function for an intramembrane protease to facilitate the association of core with viral genomes, thereby creating putative sites for assembly of nascent virus particles.
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Affiliation(s)
- Paul Targett-Adams
- MRC Virology Unit, Institute of Virology, Glasgow G11 5JR, United Kingdom
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22
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Crawshaw SG, Cross BCS, Wilson CM, High S. The oligomeric state of Derlin-1 is modulated by endoplasmic reticulum stress. Mol Membr Biol 2007; 24:113-20. [PMID: 17453418 DOI: 10.1080/09687860600988727] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The endoplasmic reticulum (ER) is a major site of protein synthesis in eukaryotes. Newly synthesized proteins are monitored by a process of quality control, which removes misfolded or unassembled polypeptides from the ER for degradation by the proteasome. This requires the retrotranslocation of the misfolded proteins from the ER lumen into the cytosol via a pathway that, for some substrates, involves members of the recently discovered Derlin family. The Derlin-1 isoform is present as a dimer in the ER, and we now show that its dimerization is modulated by ER stress. Three distinct types of chemically-induced ER stress substantially reduce the levels of Derlin-1 dimer as assayed by both cross-linking and co-immunoprecipitation. The potential function of the different Derlin-1 populations with respect to ER quality control is investigated by analysing their capacity to associate with a misfolded membrane protein fragment. We show for the first time that Derlin-1 can associate with an aberrant membrane protein fragment in the absence of the viral component US11, and conclude that it is the monomeric form of Derlin-1 that interacts with this potential ER-associated degradation substrate. On the basis of these data we propose a model where the pool of active Derlin-1 in the ER membrane can be modulated in response to ER stress.
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23
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Vauloup-Fellous C, Pène V, Garaud-Aunis J, Harper F, Bardin S, Suire Y, Pichard E, Schmitt A, Sogni P, Pierron G, Briand P, Rosenberg AR. Signal Peptide Peptidase-catalyzed Cleavage of Hepatitis C Virus Core Protein Is Dispensable for Virus Budding but Destabilizes the Viral Capsid. J Biol Chem 2006; 281:27679-92. [PMID: 16849324 DOI: 10.1074/jbc.m602587200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The capsid of hepatitis C virus (HCV) particles is considered to be composed of the mature form (p21) of core protein. Maturation to p21 involves cleavage of the transmembrane domain of the precursor form (p23) of core protein by signal peptide peptidase (SPP), a cellular protease embedded in the endoplasmic reticulum membrane. Here we have addressed whether SPP-catalyzed maturation to p21 is a prerequisite for HCV particle morphogenesis in the endoplasmic reticulum. HCV structural proteins were expressed by using recombinant Semliki Forest virus replicon in mammalian cells or recombinant baculovirus in insect cells, because these systems have been shown to allow the visualization of HCV budding events and the isolation of HCV-like particles, respectively. Inhibition of SPP-catalyzed cleavage of core protein by either an SPP inhibitor or HCV core mutations not only did not prevent but instead tended to facilitate the observation of viral buds and the recovery of virus-like particles. Remarkably, although maturation to p21 was only partially inhibited by mutations in insect cells, p23 was the only form of core protein found in HCV-like particles. Finally, newly developed assays demonstrated that p23 capsids are more stable than p21 capsids. These results show that SPP-catalyzed cleavage of core protein is dispensable for HCV budding but decreases the stability of the viral capsid. We propose a model in which p23 is the form of HCV core protein committed to virus assembly, and cleavage by SPP occurs during and/or after virus budding to predispose the capsid to subsequent disassembly in a new cell.
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24
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Young ARJ, Chan EYW, Hu XW, Köchl R, Crawshaw SG, High S, Hailey DW, Lippincott-Schwartz J, Tooze SA. Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. J Cell Sci 2006; 119:3888-900. [PMID: 16940348 DOI: 10.1242/jcs.03172] [Citation(s) in RCA: 605] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Autophagy, fundamentally a lysosomal degradation pathway, functions in cells during normal growth and certain pathological conditions, including starvation, to maintain homeostasis. Autophagosomes are formed through a mechanism that is not well understood, despite the identification of many genes required for autophagy. We have studied the mammalian homologue of Atg9p, a multi-spanning transmembrane protein essential in yeast for autophagy, to gain a better understanding of the function of this ubiquitious protein. We show that both the N- and C-termini of mammalian Atg9 (mAtg9) are cytosolic, and predict that mAtg9 spans the membrane six times. We find that mAtg9 is located in the trans-Golgi network and late endosomes and colocalizes with TGN46, the cation-independent mannose-6-phosphate receptor, Rab7 and Rab9. Amino acid starvation or rapamycin treatment, which upregulates autophagy, causes a redistribution of mAtg9 from the TGN to peripheral, endosomal membranes, which are positive for the autophagosomal marker GFP-LC3. siRNA-mediated depletion of the putative mammalian homologue of Atg1p, ULK1, inhibits this starvation-induced redistribution. The redistribution of mAtg9 also requires PI 3-kinase activity, and is reversed after restoration of amino acids. We speculate that starvation-induced autophagy, which requires mAtg9, may rely on an alteration of the steady-state trafficking of mAtg9, in a Atg1-dependent manner.
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Affiliation(s)
- Andrew R J Young
- Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London, WC2A 3PX, UK
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25
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Loureiro J, Lilley BN, Spooner E, Noriega V, Tortorella D, Ploegh HL. Signal peptide peptidase is required for dislocation from the endoplasmic reticulum. Nature 2006; 441:894-7. [PMID: 16738546 DOI: 10.1038/nature04830] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 04/18/2006] [Indexed: 11/08/2022]
Abstract
Human cytomegalovirus (HCMV) prevents the display of class I major histocompatibility complex (MHC) peptide complexes at the surface of infected cells as a means of escaping immune detection. Two HCMV-encoded immunoevasins, US2 and US11, induce the dislocation of class I MHC heavy chains from the endoplasmic reticulum membrane and target them for proteasomal degradation in the cytosol. Although the outcome of the dislocation reactions catalysed is similar, US2 and US11 operate differently: Derlin-1 is a key component of the US11 but not the US2 pathway. So far, proteins essential for US2-dependent dislocation have not been identified. Here we compare interacting partners of wild-type US2 with those of a dislocation-incompetent US2 mutant, and identify signal peptide peptidase (SPP) as a partner for the active form of US2. We show that a decrease in SPP levels by RNA-mediated interference inhibits heavy-chain dislocation by US2 but not by US11. Our data implicate SPP in the US2 pathway and indicate the possibility of a previously unknown function for this intramembrane-cleaving aspartic protease in dislocation from the endoplasmic reticulum.
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Affiliation(s)
- Joana Loureiro
- Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA
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26
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Boulant S, Montserret R, Hope RG, Ratinier M, Targett-Adams P, Lavergne JP, Penin F, McLauchlan J. Structural determinants that target the hepatitis C virus core protein to lipid droplets. J Biol Chem 2006; 281:22236-22247. [PMID: 16704979 DOI: 10.1074/jbc.m601031200] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Hepatitis C virus core protein is targeted to lipid droplets, which serve as intracellular storage organelles, by its C-terminal domain, termed D2. From circular dichroism and nuclear magnetic resonance analyses, we demonstrate that the major structural elements within D2 consist of two amphipathic alpha-helices (Helix I and Helix II) separated by a hydrophobic loop. Both helices require a hydrophobic environment for folding, indicating that lipid interactions contribute to their structural integrity. Mutational studies revealed that a combination of Helix I, the hydrophobic loop, and Helix II is essential for efficient lipid droplet association and pointed to an in-plane membrane interaction of the two helices at the phospholipid layer interface. Aside from lipid droplet association, membrane interaction of D2 is necessary for folding and stability of core following maturation at the endoplasmic reticulum membrane by signal peptide peptidase. These studies identify critical determinants within a targeting domain that enable trafficking and attachment of a viral protein to lipid droplets. They also serve as a unique model for elucidating the specificity of protein-lipid interactions between two membrane-bound organelles.
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Affiliation(s)
- Steeve Boulant
- Medical Research Council Virology Unit, Institute of Virology, Church St., Glasgow G11 5JR, Scotland, United Kingdom; Institut de Biologie et Chimie des Protéines, CNRS-UMR 5086, IFR128 BioSciences, University of Lyon, 7 Passage du Vercors, Lyon-Gerland, Lyon F-69367, Cedex 07, France
| | - Roland Montserret
- Institut de Biologie et Chimie des Protéines, CNRS-UMR 5086, IFR128 BioSciences, University of Lyon, 7 Passage du Vercors, Lyon-Gerland, Lyon F-69367, Cedex 07, France
| | - R Graham Hope
- Medical Research Council Virology Unit, Institute of Virology, Church St., Glasgow G11 5JR, Scotland, United Kingdom
| | - Maxime Ratinier
- Institut de Biologie et Chimie des Protéines, CNRS-UMR 5086, IFR128 BioSciences, University of Lyon, 7 Passage du Vercors, Lyon-Gerland, Lyon F-69367, Cedex 07, France
| | - Paul Targett-Adams
- Medical Research Council Virology Unit, Institute of Virology, Church St., Glasgow G11 5JR, Scotland, United Kingdom
| | - Jean-Pierre Lavergne
- Institut de Biologie et Chimie des Protéines, CNRS-UMR 5086, IFR128 BioSciences, University of Lyon, 7 Passage du Vercors, Lyon-Gerland, Lyon F-69367, Cedex 07, France
| | - Francois Penin
- Institut de Biologie et Chimie des Protéines, CNRS-UMR 5086, IFR128 BioSciences, University of Lyon, 7 Passage du Vercors, Lyon-Gerland, Lyon F-69367, Cedex 07, France.
| | - John McLauchlan
- Medical Research Council Virology Unit, Institute of Virology, Church St., Glasgow G11 5JR, Scotland, United Kingdom.
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27
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Urny J, Hermans-Borgmeyer I, Schaller HC. Cell-surface expression of a new splice variant of the mouse signal peptide peptidase. ACTA ACUST UNITED AC 2006; 1759:159-65. [PMID: 16730383 DOI: 10.1016/j.bbaexp.2006.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 02/17/2006] [Accepted: 02/28/2006] [Indexed: 10/24/2022]
Abstract
The signal peptide peptidase (SPP) is an intramembrane-cleaving aspartyl protease that acts on type II transmembrane proteins. SPP substrates include signal peptides after they have been cleaved from a preprotein, hence the name. The known SPP isoform, which we renamed SPPalpha, contains an endoplasmic reticulum retention signal at the carboxy terminus. We found a new splice variant, SPPbeta, with an additional in-frame exon inserted between exons 11 and 12 of SPPalpha. Insertion of the new exon led to a complete change in the amino-acid sequence of the carboxy tail. A stop codon within this new exon resulted in silencing of exon 12 and eliminated the endoplasmic reticulum retention signal. The new SPP isoform predominantly localised to the cell surface in contrast to the more restricted localisation of SPPalpha in the endoplasmic reticulum. Differential expression in mouse tissues and in subcellular compartments suggests new functions for SPP in addition to cleaving signal peptides.
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Affiliation(s)
- Jens Urny
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, Martinistr. 52, 20246 Hamburg, Germany
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28
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McCracken AA, Brodsky JL. Recognition and delivery of ERAD substrates to the proteasome and alternative paths for cell survival. Curr Top Microbiol Immunol 2006; 300:17-40. [PMID: 16573235 DOI: 10.1007/3-540-28007-3_2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Endoplasmic reticulum-associated protein degradation (ERAD) is a protein quality control mechanism that minimizes the detrimental effects of protein misfolding in the secretory pathway. Molecular chaperones and ER lumenal lectins are essential components of this process because they maintain the solubility of unfolded proteins and can target ERAD substrates to the cytoplasmic proteasome. Other factors are likely required to aid in the selection of ERAD substrates, and distinct proteinaceous machineries are required for substrate retrotranslocation/dislocation from the ER and proteasome targeting. When the capacity of the ERAD machinery is exceeded or compromised, multiple degradative routes can be enlisted to prevent the detrimental consequences of ERAD substrate accumulation, which include cell death and disease.
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Affiliation(s)
- A A McCracken
- Biology Department, University of Nevada, Reno, NV 89557, USA.
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29
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Oberdorf J, Carlson EJ, Skach WR. Uncoupling proteasome peptidase and ATPase activities results in cytosolic release of an ER polytopic protein. J Cell Sci 2006; 119:303-13. [PMID: 16390870 DOI: 10.1242/jcs.02732] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The 26S proteasome is the primary protease responsible for degrading misfolded membrane proteins in the endoplasmic reticulum. Here we examine the specific role of beta subunit function on polypeptide cleavage and membrane release of CFTR, a prototypical ER-associated degradation substrate with 12 transmembrane segments. In the presence of ATP, cytosol and fully active proteasomes, CFTR was rapidly degraded and released into the cytosol solely in the form of trichloroacetic acid (TCA)-soluble peptide fragments. Inhibition of proteasome beta subunits markedly decreased CFTR degradation but surprisingly, had relatively minor effects on membrane extraction and release. As a result, large TCA-insoluble degradation intermediates derived from multiple CFTR domains accumulated in the cytosol where they remained stably bound to inhibited proteasomes. Production of TCA-insoluble fragments varied for different proteasome inhibitors and correlated inversely with the cumulative proteolytic activities of beta1, beta2 and beta5 subunits. By contrast, ATPase inhibition decreased CFTR release but had no effect on the TCA solubility of the released fragments. Our results indicate that the physiologic balance between membrane extraction and peptide cleavage is maintained by excess proteolytic capacity of the 20S subunit. Active site inhibitors reduce this capacity, uncouple ATPase and peptidase activities, and generate cytosolic degradation intermediates by allowing the rate of unfolding to exceed the rate of polypeptide cleavage.
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Affiliation(s)
- Jon Oberdorf
- Department of Biochemistry and Molecular Biology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA
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30
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Abstract
Relatively small genomes and high replication rates allow viruses and bacteria to accumulate mutations. This continuously presents the host immune system with new challenges. On the other side of the trenches, an increasingly well-adjusted host immune response, shaped by coevolutionary history, makes a pathogen's life a rather complicated endeavor. It is, therefore, no surprise that pathogens either escape detection or modulate the host immune response, often by redirecting normal cellular pathways to their advantage. For the purpose of this chapter, we focus mainly on the manipulation of the class I and class II major histocompatibility complex (MHC) antigen presentation pathways and the ubiquitin (Ub)-proteasome system by both viral and bacterial pathogens. First, we describe the general features of antigen presentation pathways and the Ub-proteasome system and then address how they are manipulated by pathogens. We discuss the many human cytomegalovirus (HCMV)-encoded immunomodulatory genes that interfere with antigen presentation (immunoevasins) and focus on the HCMV immunoevasins US2 and US11, which induce the degradation of class I MHC heavy chains by the proteasome by catalyzing their export from the endoplasmic reticulum (ER)-membrane into the cytosol, a process termed ER dislocation. US2- and US11-mediated subversion of ER dislocation ensures proteasomal degradation of class I MHC molecules and presumably allows HCMV to avoid recognition by cytotoxic T cells, whilst providing insight into general aspects of ER-associated degradation (ERAD) which is used by eukaryotic cells to purge their ER of defective proteins. We discuss the similarities and differences between the distinct pathways co-opted by US2 and US11 for dislocation and degradation of human class I MHC molecules and also a putatively distinct pathway utilized by the murine herpes virus (MHV)-68 mK3 immunoevasin for ER dislocation of murine class I MHC. We speculate on the implications of the three pathogen-exploited dislocation pathways to cellular ER quality control. Moreover, we discuss the ubiquitin (Ub)-proteasome system and its position at the core of antigen presentation as proteolysis and intracellular trafficking rely heavily on Ub-dependent processes. We add a few examples of manipulation of the Ub-proteasome system by pathogens in the context of the immune system and such diverse aspects of the host-pathogen relationship as virus budding, bacterial chromosome integration, and programmed cell death, to name a few. Finally, we speculate on newly found pathogen-encoded deubiquitinating enzymes (DUBs) and their putative roles in modulation of host-pathogen interactions.
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Affiliation(s)
- Joana Loureiro
- Whitehead Institute, 9 Cambridge Center, Cambridge, Massachusetts, USA
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