1
|
Hendrix S, Dartigue V, Hall H, Bawaria S, Kingma J, Bajaj B, Zelcer N, Kober DL. SPRING licenses S1P-mediated cleavage of SREBP2 by displacing an inhibitory pro-domain. Nat Commun 2024; 15:5732. [PMID: 38977690 PMCID: PMC11231238 DOI: 10.1038/s41467-024-50068-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Accepted: 06/28/2024] [Indexed: 07/10/2024] Open
Abstract
Site-one protease (S1P) conducts the first of two cleavage events in the Golgi to activate Sterol regulatory element binding proteins (SREBPs) and upregulate lipogenic transcription. S1P is also required for a wide array of additional signaling pathways. A zymogen serine protease, S1P matures through autoproteolysis of two pro-domains, with one cleavage event in the endoplasmic reticulum (ER) and the other in the Golgi. We recently identified the SREBP regulating gene, (SPRING), which enhances S1P maturation and is necessary for SREBP signaling. Here, we report the cryo-EM structures of S1P and S1P-SPRING at sub-2.5 Å resolution. SPRING activates S1P by dislodging its inhibitory pro-domain and stabilizing intra-domain contacts. Functionally, SPRING licenses S1P to cleave its cognate substrate, SREBP2. Our findings reveal an activation mechanism for S1P and provide insights into how spatial control of S1P activity underpins cholesterol homeostasis.
Collapse
Affiliation(s)
- Sebastian Hendrix
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, the Netherlands
| | - Vincent Dartigue
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Hailee Hall
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Shrankhla Bawaria
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jenina Kingma
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, the Netherlands
| | - Bilkish Bajaj
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Noam Zelcer
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, the Netherlands.
| | - Daniel L Kober
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
| |
Collapse
|
2
|
Bost C, Hartlaub J, Pinho Dos Reis V, Strecker T, Seidah NG, Groschup MH, Diederich S, Fischer K. The proprotein convertase SKI-1/S1P is a critical host factor for Nairobi sheep disease virus infectivity. Virus Res 2023; 329:199099. [PMID: 36948228 DOI: 10.1016/j.virusres.2023.199099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/14/2023] [Accepted: 03/18/2023] [Indexed: 03/24/2023]
Abstract
Nairobi sheep disease virus (NSDV) belongs to the Orthonairovirus genus in the Bunyavirales order and is genetically related to human-pathogenic Crimean-Congo hemorrhagic fever virus (CCHFV). NSDV is a zoonotic pathogen transmitted by ticks and primarily affects naïve small ruminants in which infection leads to severe and often fatal hemorrhagic gastroenteritis. Despite its veterinary importance and the striking similarities in the clinical picture between NSDV-infected ruminants and CCHFV patients, the molecular pathogenesis of NSDV and its interactions with the host cell are largely unknown. Here, we identify the membrane-bound proprotein convertase site-1 protease (S1P), also known as subtilisin/kexin-isozyme-1 (SKI-1), as a host factor affecting NSDV infectivity. Absence of S1P in SRD-12B cells, a clonal CHO-K1 cell variant with a genetic defect in the S1P gene (MBTPS1), results in significantly decreased NSDV infectivity while transient complementation of SKI-1/S1P rescues NSDV infection. SKI-1/S1P is dispensable for virus uptake but critically required for production of infectious virus progeny. Moreover, we provide evidence that SKI-1/S1P is involved in the posttranslational processing of the NSDV glycoprotein precursor. Our results demonstrate the role of SKI-1/S1P in the virus life cycle of NSDV and suggest that this protease is a common host factor for orthonairoviruses and may thus represent a promising broadly-effective, indirect antiviral target.
Collapse
Affiliation(s)
- Caroline Bost
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Julia Hartlaub
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | | | - Thomas Strecker
- Institute for Virology, Philipps-University Marburg, Germany
| | - Nabil G Seidah
- Montreal Clinical Research Institute (IRCM), affiliated to the University of Montreal, Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada
| | - Martin H Groschup
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Sandra Diederich
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Kerstin Fischer
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany.
| |
Collapse
|
3
|
Abstract
This article reviews the discovery of PCSK9, its structure-function characteristics, and its presently known and proposed novel biological functions. The major critical function of PCSK9 deduced from human and mouse studies, as well as cellular and structural analyses, is its role in increasing the levels of circulating low-density lipoprotein (LDL)-cholesterol (LDLc), via its ability to enhance the sorting and escort of the cell surface LDL receptor (LDLR) to lysosomes. This implicates the binding of the catalytic domain of PCSK9 to the EGF-A domain of the LDLR. This also requires the presence of the C-terminal Cys/His-rich domain, its binding to the secreted cytosolic cyclase associated protein 1, and possibly another membrane-bound "protein X". Curiously, in PCSK9-deficient mice, an alternative to the downregulation of the surface levels of the LDLR by PCSK9 is taking place in the liver of female mice in a 17β-estradiol-dependent manner by still an unknown mechanism. Recent studies have extended our understanding of the biological functions of PCSK9, namely its implication in septic shock, vascular inflammation, viral infections (Dengue; SARS-CoV-2) or immune checkpoint modulation in cancer via the regulation of the cell surface levels of the T-cell receptor and MHC-I, which govern the antitumoral activity of CD8+ T cells. Because PCSK9 inhibition may be advantageous in these processes, the availability of injectable safe PCSK9 inhibitors that reduces by 50% to 60% LDLc above the effect of statins is highly valuable. Indeed, injectable PCSK9 monoclonal antibody or small interfering RNA could be added to current immunotherapies in cancer/metastasis.
Collapse
Affiliation(s)
- Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute (IRCM, affiliated to the University of Montreal), Montreal, QC, Canada
| | - Annik Prat
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute (IRCM, affiliated to the University of Montreal), Montreal, QC, Canada
| |
Collapse
|
4
|
Danyukova T, Schöneck K, Pohl S. Site-1 and site-2 proteases: A team of two in regulated proteolysis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119138. [PMID: 34619164 DOI: 10.1016/j.bbamcr.2021.119138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/12/2021] [Accepted: 09/06/2021] [Indexed: 12/19/2022]
Abstract
The site-1 and site-2 proteases (S1P and S2P) were identified over 20 years ago, and the functions of both have been addressed in numerous studies ever since. Whereas S1P processes a set of substrates independently of S2P, the latter acts in concert with S1P in a mechanism, called regulated intramembrane proteolysis, that controls lipid metabolism and response to unfolded proteins. This review summarizes the molecular roles that S1P and S2P jointly play in these processes. As S1P and S2P deficiencies mainly affect connective tissues, yet with varying phenotypes, we discuss the segregated functions of S1P and S2P in terms of cell homeostasis and maintenance of the connective tissues. In addition, we provide experimental data that point at S2P, but not S1P, as a critical regulator of cell adaptation to proteotoxicity or lipid imbalance. Therefore, we hypothesize that S2P can also function independently of S1P activity.
Collapse
Affiliation(s)
- Tatyana Danyukova
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
| | - Kenneth Schöneck
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Sandra Pohl
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| |
Collapse
|
5
|
Caengprasath N, Theerapanon T, Porntaveetus T, Shotelersuk V. MBTPS2, a membrane bound protease, underlying several distinct skin and bone disorders. J Transl Med 2021; 19:114. [PMID: 33743732 PMCID: PMC7981912 DOI: 10.1186/s12967-021-02779-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 03/08/2021] [Indexed: 12/27/2022] Open
Abstract
The MBTPS2 gene on the X-chromosome encodes the membrane-bound transcription factor protease, site-2 (MBTPS2) or site-2 protease (S2P) which cleaves and activates several signaling and regulatory proteins from the membrane. The MBTPS2 is critical for a myriad of cellular processes, ranging from the regulation of cholesterol homeostasis to unfolded protein responses. While its functional role has become much clearer in the recent years, how mutations in the MBTPS2 gene lead to several human disorders with different phenotypes including Ichthyosis Follicularis, Atrichia and Photophobia syndrome (IFAP) with or without BRESHECK syndrome, Keratosis Follicularis Spinulosa Decalvans (KFSD), Olmsted syndrome, and Osteogenesis Imperfecta type XIX remains obscure. This review presents the biological role of MBTPS2 in development, summarizes its mutations and implicated disorders, and discusses outstanding unanswered questions.
Collapse
Affiliation(s)
- Natarin Caengprasath
- Center of Excellence for Medical Genomics, Medical Genomics Cluster, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
- Excellence Center for Genomics and Precision Medicine, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, 10330, Thailand
| | - Thanakorn Theerapanon
- Genomics and Precision Dentistry Research Unit, Department of Physiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Thantrira Porntaveetus
- Genomics and Precision Dentistry Research Unit, Department of Physiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, 10330, Thailand.
| | - Vorasuk Shotelersuk
- Center of Excellence for Medical Genomics, Medical Genomics Cluster, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
- Excellence Center for Genomics and Precision Medicine, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, 10330, Thailand
| |
Collapse
|
6
|
Kühnle N, Dederer V, Lemberg MK. Intramembrane proteolysis at a glance: from signalling to protein degradation. J Cell Sci 2019; 132:132/16/jcs217745. [DOI: 10.1242/jcs.217745] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
ABSTRACT
Over the last two decades, a group of unusual proteases, so-called intramembrane proteases, have become increasingly recognized for their unique ability to cleave peptide bonds within cellular membranes. They are found in all kingdoms of life and fulfil versatile functions ranging from protein maturation, to activation of signalling molecules, to protein degradation. In this Cell Science at a Glance article and the accompanying poster, we focus on intramembrane proteases in mammalian cells. By comparing intramembrane proteases in different cellular organelles, we set out to review their functions within the context of the roles of individual cellular compartments. Additionally, we exemplify their mode of action in relation to known substrates by distinguishing cleavage events that promote degradation of substrate from those that release active domains from the membrane bilayer.
Collapse
Affiliation(s)
- Nathalie Kühnle
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Verena Dederer
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Marius K. Lemberg
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| |
Collapse
|
7
|
Schweitzer GG, Gan C, Bucelli RC, Wegner D, Schmidt RE, Shinawi M, Finck BN, Brookheart RT. A mutation in Site-1 Protease is associated with a complex phenotype that includes episodic hyperCKemia and focal myoedema. Mol Genet Genomic Med 2019; 7:e00733. [PMID: 31070020 PMCID: PMC6625134 DOI: 10.1002/mgg3.733] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 01/25/2019] [Accepted: 04/04/2019] [Indexed: 01/04/2023] Open
Abstract
Background Site‐1 Protease (S1P) is a Golgi‐resident protein required for the activation of regulatory proteins that drive key cellular functions, including, the unfolded protein response (UPR) and lipid and cholesterol biosynthesis. While disruptions in S1P function have been widely characterized in animal models, to date, the implications of disrupted S1P function in human disease states are not completely known. Methods The patient and both parents underwent whole exome and mitochondrial DNA sequencing, and Sanger sequencing was used to confirm the mutation. Western blotting and immunofluorescence studies were performed on either proband‐derived fibroblasts or on an established cell line to assess protein expression and cellular localization of the mutated S1P protein. Quantitative real‐time PCR and luciferase reporter assays were used to examine activation of S1P target pathways in the context of the S1P mutation. Results We describe a female patient with a de novo heterozygous missense mutation in the transmembrane domain of S1P (p. Pro1003Ser). The patient presented to our neuromuscular clinic with episodic, activity‐induced, focal myoedema and myalgias with hyperCKemia. Her clinical phenotype was complex and included gastrointestinal hypomotility, ocular migraines, and polycystic ovary syndrome. Molecular analysis using proband‐derived fibroblasts and cell lines harboring the Pro1003Ser mutation demonstrated increased activation of UPR and lipid and cholesterol regulatory pathways and localization of S1P Pro1003Ser in the Golgi. Conclusion These findings suggest a critical function for S1P in several human organ systems and implicate an important role for S1P in various human disease states.
Collapse
Affiliation(s)
- George G Schweitzer
- John T. Milliken Department of Medicine, Division of Geriatrics and Nutritional Sciences, Washington University School of Medicine, St. Louis, Missouri
| | - Connie Gan
- John T. Milliken Department of Medicine, Division of Geriatrics and Nutritional Sciences, Washington University School of Medicine, St. Louis, Missouri
| | - Robert C Bucelli
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri
| | - Daniel Wegner
- Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Robert E Schmidt
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri
| | - Marwan Shinawi
- Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.,Division of Genetics and Genomic Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Brian N Finck
- John T. Milliken Department of Medicine, Division of Geriatrics and Nutritional Sciences, Washington University School of Medicine, St. Louis, Missouri
| | - Rita T Brookheart
- John T. Milliken Department of Medicine, Division of Geriatrics and Nutritional Sciences, Washington University School of Medicine, St. Louis, Missouri
| |
Collapse
|
8
|
Papatheodorou P, Song S, López-Ureña D, Witte A, Marques F, Ost GS, Schorch B, Chaves-Olarte E, Aktories K. Cytotoxicity of Clostridium difficile toxins A and B requires an active and functional SREBP-2 pathway. FASEB J 2018; 33:4883-4892. [PMID: 30592645 DOI: 10.1096/fj.201801440r] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Clostridium difficile is associated with antibiotic-associated diarrhea and pseudomembranous colitis in humans. Its 2 major toxins, toxins A and B, enter host cells and inactivate GTPases of the Ras homologue/rat sarcoma family by glucosylation. Pore formation of the toxins in the endosomal membrane enables the translocation of their glucosyltransferase domain into the cytosol, and membrane cholesterol is crucial for this process. Here, we asked whether the activity of the sterol regulatory element-binding protein 2 (SREBP-2) pathway, which regulates the cholesterol content in membranes, affects the susceptibility of target cells toward toxins A and B. We show that the SREBP-2 pathway is crucial for the intoxication process of toxins A and B by using pharmacological inhibitors (PF-429242, 25-hydroxycholesterol) and cells that are specifically deficient in SREBP-2 pathway signaling. SREBP-2 pathway inhibition disturbed the cholesterol-dependent pore formation of toxin B in cellular membranes. Preincubation with the cholesterol-lowering drug simvastatin protected cells from toxin B intoxication. Inhibition of the SREBP-2 pathway was without effect when the enzyme portion of toxin B was introduced into target cells via the cell delivery property of anthrax protective antigen. Taken together, these findings allowed us to identify the SREBP-2 pathway as a suitable target for the development of antitoxin therapeutics against C. difficile toxins A and B.-Papatheodorou, P., Song, S., López-Ureña, D., Witte, A., Marques, F., Ost, G. S., Schorch, B., Chaves-Olarte, E., Aktories, K. Cytotoxicity of Clostridium difficile toxins A and B requires an active and functional SREBP-2 pathway.
Collapse
Affiliation(s)
- Panagiotis Papatheodorou
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Shuo Song
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Diana López-Ureña
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Alexander Witte
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Felícia Marques
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Gerhard Stefan Ost
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Björn Schorch
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Klaus Aktories
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| |
Collapse
|
9
|
Zhou H, Yu H, Zhao X, Yang L, Huang X. Molecular dynamics simulations investigate the pathway of substrate entry active site of rhomboid protease. J Biomol Struct Dyn 2018; 37:3445-3455. [PMID: 30175657 DOI: 10.1080/07391102.2018.1517609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Rhomboid proteases can catalyze peptide bond cleavage and participate in abundant biological processes encompassing all branches of life; however, the pathway for substrate entry into its active site remains ambiguous. Here, the two possible pathways are preliminarily determined through molecular dynamics: One pathway is between Tm2 and Tm5, and the other is between Loop3 and Loop5. Then, the umbrella sampling simulations are performed to investigate the more feasible pathway for substrate entry. The results show that free energy barriers along the two pathways are similar; in the pathway 1, Trp236 and Trp157 as pivotal residues are responsible for the rotation of substrate in the binding process; in the pathway 2, among some important residues, the residue His150 plays an important role in substrate entry. Further, combining with previous experiment results, it is concluded that the substrate is inclined to enter into the active site along pathway 2. Our results are important for further understanding the function and catalysis mechanism of rhomboid proteases. Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Hua Zhou
- a Institute of Theoretical Chemistry , Jilin University , Changchun , China
| | - Hui Yu
- b College of Chemistry and Biology , Beihua University , Jilin , China
| | - Xi Zhao
- a Institute of Theoretical Chemistry , Jilin University , Changchun , China
| | - Lianjuan Yang
- c The Fungal Reference Laboratory of Shanghai Dermatology Hospital , Shanghai , China
| | - Xuri Huang
- a Institute of Theoretical Chemistry , Jilin University , Changchun , China
| |
Collapse
|
10
|
Urata S, Uno Y, Kurosaki Y, Yasuda J. The cholesterol, fatty acid and triglyceride synthesis pathways regulated by site 1 protease (S1P) are required for efficient replication of severe fever with thrombocytopenia syndrome virus. Biochem Biophys Res Commun 2018; 503:631-636. [PMID: 29906459 DOI: 10.1016/j.bbrc.2018.06.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 06/11/2018] [Indexed: 10/14/2022]
Abstract
Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by the SFTS virus (SFTSV), which has a high mortality rate. Currently, no licensed vaccines or therapeutic agents have been approved for use against SFTSV infection. Here, we report that the cholesterol, fatty acid, and triglyceride synthesis pathways regulated by S1P is involved in SFTSV replication, using CHO-K1 cell line (SRD-12B) that is deficient in site 1 protease (S1P) enzymatic activity, PF-429242, a small compound targeting S1P enzymatic activity, and Fenofibrate and Lovastatin, which inhibit triglyceride and cholesterol synthesis, respectively. These results enhance our understanding of the SFTSV replication mechanism and may contribute to the development of novel therapies for SFTSV infection.
Collapse
Affiliation(s)
- Shuzo Urata
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Japan; National Research Center for the Control and Prevention of Infectious Diseases (CCPID), Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan.
| | - Yukiko Uno
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Japan.
| | - Yohei Kurosaki
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Japan.
| | - Jiro Yasuda
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Japan; National Research Center for the Control and Prevention of Infectious Diseases (CCPID), Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan.
| |
Collapse
|
11
|
Site-1 protease and lysosomal homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:2162-2168. [PMID: 28693924 DOI: 10.1016/j.bbamcr.2017.06.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/29/2017] [Accepted: 06/30/2017] [Indexed: 11/22/2022]
Abstract
The Golgi-resident site-1 protease (S1P) is a key regulator of cholesterol homeostasis and ER stress responses by converting latent transcription factors sterol regulatory element binding proteins (SREPBs) and activating transcription factor 6 (ATF6), as well as viral glycoproteins to their active forms. S1P is also essential for lysosome biogenesis via proteolytic activation of the hexameric GlcNAc-1-phosphotransferase complex required for modification of newly synthesized lysosomal enzymes with the lysosomal targeting signal, mannose 6-phosphate. In the absence of S1P, the catalytically inactive α/β-subunit precursor of GlcNAc-1-phosphotransferase fails to be activated and results in missorting of newly synthesized lysosomal enzymes, and lysosomal accumulation of non-degraded material, which are biochemical features of defective GlcNAc-1-phosphotransferase subunits and the associated pediatric lysosomal diseases mucolipidosis type II and III. The early embryonic death of S1P-deficient mice and the importance of various S1P-regulated biological processes, including lysosomal homeostasis, cautioned for clinical inhibition of S1P. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.
Collapse
|
12
|
Abstract
Cellular cholesterol levels are intricately controlled to maintain homeostasis. Here, we describe ways in which cellular cholesterol status can be manipulated for the study of cholesterol homeostasis, including sterol starvation (by culturing cells in lipoprotein-deficient serum and pretreating/treating with the cholesterol-lowering drug, statin) and sterol enrichment (using cholesterol complexed to cyclodextrin, and low-density lipoprotein). We also describe how to prepare lipoprotein-deficient serum and complex cholesterol to cyclodextrin.
Collapse
Affiliation(s)
- Winnie Luu
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Biological Sciences Building D26, Sydney, NSW, 2052, Australia
| | - Ingrid C Gelissen
- Faculty of Pharmacy, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Biological Sciences Building D26, Sydney, NSW, 2052, Australia.
| |
Collapse
|
13
|
Shao W, Machamer CE, Espenshade PJ. Fatostatin blocks ER exit of SCAP but inhibits cell growth in a SCAP-independent manner. J Lipid Res 2016; 57:1564-73. [PMID: 27324795 DOI: 10.1194/jlr.m069583] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Indexed: 12/30/2022] Open
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of cellular lipid homeostasis and activate expression of genes required for fatty acid, triglyceride, and cholesterol synthesis and uptake. SREBP cleavage activating protein (SCAP) plays an essential role in SREBP activation by mediating endoplasmic reticulum (ER)-to-Golgi transport of SREBP. In the Golgi, membrane-bound SREBPs are cleaved sequentially by the site-1 and site-2 proteases. Recent studies have shown a requirement for the SREBP pathway in the development of fatty liver disease and tumor growth, making SCAP a target for drug development. Fatostatin is a chemical inhibitor of the SREBP pathway that directly binds SCAP and blocks its ER-to-Golgi transport. In this study, we determined that fatostatin blocks ER exit of SCAP and showed that inhibition is independent of insulin-induced gene proteins, which function to retain the SCAP-SREBP complex in the ER. Fatostatin potently inhibited cell growth, but unexpectedly exogenous lipids failed to rescue proliferation of fatostatin-treated cells. Furthermore, fatostatin inhibited growth of cells lacking SCAP Using a vesicular stomatitis virus glycoprotein (VSVG) trafficking assay, we demonstrated that fatostatin delays ER-to-Golgi transport of VSVG. In summary, fatostatin inhibited SREBP activation, but fatostatin additionally inhibited cell proliferation through both lipid-independent and SCAP-independent mechanisms, possibly by general inhibition of ER-to-Golgi transport.
Collapse
Affiliation(s)
- Wei Shao
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Peter J Espenshade
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| |
Collapse
|
14
|
da Palma JR, Cendron L, Seidah NG, Pasquato A, Kunz S. Mechanism of Folding and Activation of Subtilisin Kexin Isozyme-1 (SKI-1)/Site-1 Protease (S1P). J Biol Chem 2015; 291:2055-66. [PMID: 26645686 DOI: 10.1074/jbc.m115.677757] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Indexed: 11/06/2022] Open
Abstract
The proprotein convertase subtilisin kexin isozyme-1 (SKI-1)/site-1 protease (S1P) is implicated in lipid homeostasis, the unfolded protein response, and lysosome biogenesis. The protease is further hijacked by highly pathogenic emerging viruses for the processing of their envelope glycoproteins. Zymogen activation of SKI-1/S1P requires removal of an N-terminal prodomain, by a multistep process, generating the mature enzyme. Here, we uncover a modular structure of the human SKI-1/S1P prodomain and define its function in folding and activation. We provide evidence that the N-terminal AB fragment of the prodomain represents an autonomous structural and functional unit that is necessary and sufficient for folding and partial activation. In contrast, the C-terminal BC fragment lacks a defined structure but is crucial for autoprocessing and full catalytic activity. Phylogenetic analysis revealed that the sequence of the AB domain is highly conserved, whereas the BC fragment shows considerable variation and seems even absent in some species. Notably, SKI-1/S1P of arthropods, like the fruit fly Drosophila melanogaster, contains a shorter prodomain comprised of full-length AB and truncated BC regions. Swapping the prodomain fragments between fly and human resulted in a fully mature and active SKI-1/S1P chimera. Our study suggests that primordial SKI-1/S1P likely contained a simpler prodomain consisting of the highly conserved AB fragment that represents an independent folding unit. The BC region appears as a later evolutionary acquisition, possibly allowing more subtle fine-tuning of the maturation process.
Collapse
Affiliation(s)
- Joel Ramos da Palma
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne CH-1011, Switzerland
| | - Laura Cendron
- the Department of Biology, University of Padua, 35122 Padua, Italy, and
| | - Nabil Georges Seidah
- the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Antonella Pasquato
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne CH-1011, Switzerland,
| | - Stefan Kunz
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne CH-1011, Switzerland,
| |
Collapse
|
15
|
A Molecular Sensor To Characterize Arenavirus Envelope Glycoprotein Cleavage by Subtilisin Kexin Isozyme 1/Site 1 Protease. J Virol 2015; 90:705-14. [PMID: 26512085 DOI: 10.1128/jvi.01751-15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Accepted: 10/14/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Arenaviruses are emerging viruses including several causative agents of severe hemorrhagic fevers in humans. The advent of next-generation sequencing technology has greatly accelerated the discovery of novel arenavirus species. However, for many of these viruses, only genetic information is available, and their zoonotic disease potential remains unknown. During the arenavirus life cycle, processing of the viral envelope glycoprotein precursor (GPC) by the cellular subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P) is crucial for productive infection. The ability of newly emerging arenaviruses to hijack human SKI-1/S1P appears, therefore, to be a requirement for efficient zoonotic transmission and human disease potential. Here we implement a newly developed cell-based molecular sensor for SKI-1/S1P to characterize the processing of arenavirus GPC-derived target sequences by human SKI-1/S1P in a quantitative manner. We show that only nine amino acids flanking the putative cleavage site are necessary and sufficient to accurately recapitulate the efficiency and subcellular location of arenavirus GPC processing. In a proof of concept, our sensor correctly predicts efficient processing of the GPC of the newly emergent pathogenic Lujo virus by human SKI-1/S1P and defines the exact cleavage site. Lastly, we employed our sensor to show efficient GPC processing of a panel of pathogenic and nonpathogenic New World arenaviruses, suggesting that GPC cleavage represents no barrier for zoonotic transmission of these pathogens. Our SKI-1/S1P sensor thus represents a rapid and robust test system for assessment of the processing of putative cleavage sites derived from the GPCs of newly discovered arenavirus by the SKI-1/S1P of humans or any other species, based solely on sequence information. IMPORTANCE Arenaviruses are important emerging human pathogens that can cause severe hemorrhagic fevers with high mortality in humans. A crucial step in productive arenavirus infection of human cells is the processing of the viral envelope glycoprotein by the cellular subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P). In order to break the species barrier during zoonotic transmission and cause severe disease in humans, newly emerging arenaviruses must be able to hijack human SKI-1/S1P efficiently. Here we implement a newly developed cell-based molecular sensor for human SKI-1/S1P to characterize the processing of arenavirus glycoproteins in a quantitative manner. We further use our sensor to correctly predict efficient processing of the glycoprotein of the newly emergent pathogenic Lujo virus by human SKI-1/S1P. Our sensor thus represents a rapid and robust test system with which to assess whether the glycoprotein of any newly emerging arenavirus can be efficiently processed by human SKI-1/S1P, based solely on sequence information.
Collapse
|
16
|
McFarlane MR, Cantoria MJ, Linden AG, January BA, Liang G, Engelking LJ. Scap is required for sterol synthesis and crypt growth in intestinal mucosa. J Lipid Res 2015; 56:1560-71. [PMID: 25896350 DOI: 10.1194/jlr.m059709] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Indexed: 11/20/2022] Open
Abstract
SREBP cleavage-activating protein (Scap) is an endoplasmic reticulum membrane protein required for cleavage and activation of sterol regulatory element-binding proteins (SREBPs), which activate the transcription of genes in sterol and fatty acid biosynthesis. Liver-specific loss of Scap is well tolerated; hepatic synthesis of sterols and fatty acids is reduced, but mice are otherwise healthy. To determine whether Scap loss is tolerated in the intestine, we generated a mouse model (Vil-Scap(-)) in which tamoxifen-inducible Cre-ER(T2), a fusion protein of Cre recombinase with a mutated ligand binding domain of the human estrogen receptor, ablates Scap in intestinal mucosa. After 4 days of tamoxifen, Vil-Scap(-) mice succumb with a severe enteropathy and near-complete collapse of intestinal mucosa. Organoids grown ex vivo from intestinal crypts of Vil-Scap(-) mice are readily killed when Scap is deleted by 4-hydroxytamoxifen. Death is prevented when culture medium is supplemented with cholesterol and oleate. These data show that, unlike the liver, the intestine requires Scap to sustain tissue integrity by maintaining the high levels of lipid synthesis necessary for proliferation of intestinal crypts.
Collapse
Affiliation(s)
- Matthew R McFarlane
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Mary Jo Cantoria
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Albert G Linden
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Brandon A January
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Guosheng Liang
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Luke J Engelking
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046 Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| |
Collapse
|
17
|
Velho RV, De Pace R, Klünder S, Sperb-Ludwig F, Lourenço CM, Schwartz IVD, Braulke T, Pohl S. Analyses of disease-related GNPTAB mutations define a novel GlcNAc-1-phosphotransferase interaction domain and an alternative site-1 protease cleavage site. Hum Mol Genet 2015; 24:3497-505. [PMID: 25788519 PMCID: PMC4498157 DOI: 10.1093/hmg/ddv100] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/13/2015] [Indexed: 12/22/2022] Open
Abstract
Mucolipidosis II (MLII) and III alpha/beta are autosomal-recessive diseases of childhood caused by mutations in GNPTAB encoding the α/β-subunit precursor protein of the GlcNAc-1-phosphotransferase complex. This enzyme modifies lysosomal hydrolases with mannose 6-phosphate targeting signals. Upon arrival in the Golgi apparatus, the newly synthesized α/β-subunit precursor is catalytically activated by site-1 protease (S1P). Here we performed comprehensive expression studies of GNPTAB mutations, including two novel mutations T644M and T1223del, identified in Brazilian MLII/MLIII alpha/beta patients. We show that the frameshift E757KfsX1 and the non-sense R587X mutations result in the retention of enzymatically inactive truncated precursor proteins in the endoplasmic reticulum (ER) due to loss of cytosolic ER exit motifs consistent with a severe clinical phenotype in homozygosity. The luminal missense mutations, C505Y, G575R and T644M, partially impaired ER exit and proteolytic activation in accordance with less severe MLIII alpha/beta disease symptoms. Analogous to the previously characterized S399F mutant, we found that the missense mutation I403T led to retention in the ER and loss of catalytic activity. Substitution of further conserved residues in stealth domain 2 (I346 and W357) revealed similar biochemical properties and allowed us to define a putative binding site for accessory proteins required for ER exit of α/β-subunit precursors. Interestingly, the analysis of the Y937_M972del mutant revealed partial Golgi localization and formation of abnormal inactive β-subunits generated by S1P which correlate with a clinical MLII phenotype. Expression analyses of mutations identified in patients underline genotype–phenotype correlations in MLII/MLIII alpha/beta and provide novel insights into structural requirements of proper GlcNAc-1-phosphotransferase activity.
Collapse
Affiliation(s)
- Renata Voltolini Velho
- Department of Genetics, Universidade Federal do Rio Grande do Sul, Avenida Paulo Gama 110, 90040-060 Porto Alegre, Brazil
| | - Raffaella De Pace
- Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Sarah Klünder
- Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Fernanda Sperb-Ludwig
- Laboratory of Basic Research and Advanced Investigations in Neurosciences, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcellos 2350, 90035-903 Porto Alegre, Brazil and
| | - Charles Marques Lourenço
- Neurogenetics Unit, Department of Neurology, School of Medicine of Ribeirao Preto, University of São Paulo, Avenida Bandeirantes 3900, 14050-260 Ribeirão Preto, Brazil
| | - Ida V D Schwartz
- Department of Genetics, Universidade Federal do Rio Grande do Sul, Avenida Paulo Gama 110, 90040-060 Porto Alegre, Brazil, Laboratory of Basic Research and Advanced Investigations in Neurosciences, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcellos 2350, 90035-903 Porto Alegre, Brazil and
| | - Thomas Braulke
- Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Sandra Pohl
- Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany,
| |
Collapse
|
18
|
da Palma JR, Burri DJ, Oppliger J, Salamina M, Cendron L, de Laureto PP, Seidah NG, Kunz S, Pasquato A. Zymogen activation and subcellular activity of subtilisin kexin isozyme 1/site 1 protease. J Biol Chem 2014; 289:35743-56. [PMID: 25378398 DOI: 10.1074/jbc.m114.588525] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proprotein convertase subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P) plays crucial roles in cellular homeostatic functions and is hijacked by pathogenic viruses for the processing of their envelope glycoproteins. Zymogen activation of SKI-1/S1P involves sequential autocatalytic processing of its N-terminal prodomain at sites B'/B followed by the herein newly identified C'/C sites. We found that SKI-1/S1P autoprocessing results in intermediates whose catalytic domain remains associated with prodomain fragments of different lengths. In contrast to other zymogen proprotein convertases, all incompletely matured intermediates of SKI-1/S1P showed full catalytic activity toward cellular substrates, whereas optimal cleavage of viral glycoproteins depended on B'/B processing. Incompletely matured forms of SKI-1/S1P further process cellular and viral substrates in distinct subcellular compartments. Using a cell-based sensor for SKI-1/S1P activity, we found that 9 amino acid residues at the cleavage site (P1-P8) and P1' are necessary and sufficient to define the subcellular location of processing and to determine to what extent processing of a substrate depends on SKI-1/S1P maturation. In sum, our study reveals novel and unexpected features of SKI-1/S1P zymogen activation and subcellular specificity of activity toward cellular and pathogen-derived substrates.
Collapse
Affiliation(s)
- Joel Ramos da Palma
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland
| | - Dominique Julien Burri
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland
| | - Joël Oppliger
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland
| | | | | | - Patrizia Polverino de Laureto
- the Department of Pharmaceutical Sciences, Centro Ricerche Interdipartimentale Biotecnologie Innovative, University of Padua, 35121 Padua, Italy, and
| | - Nabil Georges Seidah
- the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Stefan Kunz
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland,
| | - Antonella Pasquato
- From the Institute of Microbiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland,
| |
Collapse
|
19
|
Petersen J, Drake MJ, Bruce EA, Riblett AM, Didigu CA, Wilen CB, Malani N, Male F, Lee FH, Bushman FD, Cherry S, Doms RW, Bates P, Briley K. The major cellular sterol regulatory pathway is required for Andes virus infection. PLoS Pathog 2014; 10:e1003911. [PMID: 24516383 PMCID: PMC3916400 DOI: 10.1371/journal.ppat.1003911] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 12/18/2013] [Indexed: 12/21/2022] Open
Abstract
The Bunyaviridae comprise a large family of RNA viruses with worldwide distribution and includes the pathogenic New World hantavirus, Andes virus (ANDV). Host factors needed for hantavirus entry remain largely enigmatic and therapeutics are unavailable. To identify cellular requirements for ANDV infection, we performed two parallel genetic screens. Analysis of a large library of insertionally mutagenized human haploid cells and a siRNA genomic screen converged on components (SREBP-2, SCAP, S1P and S2P) of the sterol regulatory pathway as critically important for infection by ANDV. The significance of this pathway was confirmed using functionally deficient cells, TALEN-mediated gene disruption, RNA interference and pharmacologic inhibition. Disruption of sterol regulatory complex function impaired ANDV internalization without affecting virus binding. Pharmacologic manipulation of cholesterol levels demonstrated that ANDV entry is sensitive to changes in cellular cholesterol and raises the possibility that clinically approved regulators of sterol synthesis may prove useful for combating ANDV infection. As obligate, intracellular parasites viruses are dependent upon the host cell for numerous factors and processes. However, for many important viruses few of the required host factors have been identified. Hantaviruses are rodent-borne viruses that are associated with severe human disease. Transmission to humans occurs sporadically with a recent notable example in Yosemite National park. In the present study, we utilized two independent genetic strategies to discover cellular factors needed for replication of the highly pathogenic hantavirus Andes virus. We found that four genes, encoding components of a complex involved in regulation of cholesterol synthesis and uptake, were critical for Andes virus infection. Drugs that inhibit an enzyme in this complex or that reduce cellular cholesterol levels effectively blocked Andes virus infection, suggesting new ways for combating this pathogenic virus.
Collapse
Affiliation(s)
- Josiah Petersen
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Mary Jane Drake
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Emily A. Bruce
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amber M. Riblett
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Chukwuka A. Didigu
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Craig B. Wilen
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Nirav Malani
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Frances Male
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Fang-Hua Lee
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Frederic D. Bushman
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Sara Cherry
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Robert W. Doms
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Paul Bates
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (PB); (KB)
| | - Kenneth Briley
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (PB); (KB)
| |
Collapse
|
20
|
Shao W, Espenshade PJ. Sterol regulatory element-binding protein (SREBP) cleavage regulates Golgi-to-endoplasmic reticulum recycling of SREBP cleavage-activating protein (SCAP). J Biol Chem 2014; 289:7547-57. [PMID: 24478315 DOI: 10.1074/jbc.m113.545699] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of cellular lipogenesis. Release of membrane-bound SREBP requires SREBP cleavage-activating protein (SCAP) to escort SREBP from the endoplasmic reticulum (ER) to the Golgi for cleavage by site-1 and site-2 proteases. SCAP then recycles to the ER for additional rounds of SREBP binding and transport. Mechanisms regulating ER-to-Golgi transport of SCAP-SREBP are understood in molecular detail, but little is known about SCAP recycling. Here, we have demonstrated that SCAP Golgi-to-ER transport requires cleavage of SREBP at site-1. Reductions in SREBP cleavage lead to SCAP degradation in lysosomes, providing additional negative feedback control to the SREBP pathway. Current models suggest that SREBP plays a passive role prior to cleavage. However, we show that SREBP actively prevents premature recycling of SCAP-SREBP until initiation of SREBP cleavage. SREBP regulates SCAP in human cells and yeast, indicating that this is an ancient regulatory mechanism.
Collapse
Affiliation(s)
- Wei Shao
- From the Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | | |
Collapse
|
21
|
Radhakrishnan SK, den Besten W, Deshaies RJ. p97-dependent retrotranslocation and proteolytic processing govern formation of active Nrf1 upon proteasome inhibition. eLife 2014; 3:e01856. [PMID: 24448410 PMCID: PMC3896944 DOI: 10.7554/elife.01856] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Proteasome inhibition elicits an evolutionarily conserved response wherein proteasome subunit mRNAs are upregulated, resulting in recovery (i.e., ‘bounce-back’) of proteasome activity. We previously demonstrated that the transcription factor Nrf1/NFE2L1 mediates this homeostatic response in mammalian cells. We show here that Nrf1 is initially translocated into the lumen of the ER, but is rapidly and efficiently retrotranslocated to the cytosolic side of the membrane in a manner that depends on p97/VCP. Normally, retrotranslocated Nrf1 is degraded promptly by the proteasome and active species do not accumulate. However, in cells with compromised proteasomes, retrotranslocated Nrf1 escapes degradation and is cleaved N-terminal to Leu-104 to yield a fragment that is no longer tethered to the ER membrane. Importantly, this cleavage event is essential for Nrf1-dependent activation of proteasome gene expression upon proteasome inhibition. Our data uncover an unexpected role for p97 in activation of a transcription factor by relocalizing it from the ER lumen to the cytosol. DOI:http://dx.doi.org/10.7554/eLife.01856.001 Cells exposed to high temperatures, infections and other forms of stress often produce oxygen ions and peroxide molecules that can cause damage to proteins and DNA. Cells therefore rely on molecular machines called proteasomes to eliminate damaged proteins, before they cause too much harm. Two related transcription factors—proteins that interact with DNA to ‘switch on’ the expression of genes—are involved in a cell’s responses to stress, but in different ways. Nrf2 switches on genes that limit the damage caused by oxygen ions and peroxide molecules, while Nrf1 switches on the genes that encode the components of the proteasome. As such, Nrf1 helps to restart proteasome activity if it has been shut off—a phenomenon known as ‘bounce-back’. Within a cell, Nrf1 is known to start off embedded within the membranes of a structure called the endoplasmic reticulum. However, it is not clear how activated Nrf1 leaves this membrane and enters the nucleus to interact with the cell’s DNA. Now, Radhakrishnan et al. show that when Nrf1 is produced, most of its length is found inside the endoplasmic reticulum, with only a small piece being anchored in the surrounding membrane. This is unlike previously described transcription factors that associate with the endoplasmic reticulum, which are stuck to the outside of this structure. Radhakrishnan et al. also discovered that the activation of Nrf1 depends on an enzyme called p97 or VCP. This enzyme helps to flip Nrf1 from the inside of the endoplasmic reticulum to its outside surface. In most cells, the proteasome then breaks down this part of Nrf1. However, if the proteasome is inhibited, an unknown enzyme cuts Nrf1 free from the endoplasmic reticulum, allowing it to migrate to the nucleus and promote the production of more proteasome components to counteract the inhibition. Interestingly, drugs that inhibit the proteasome are used to combat cancer because the build-up of damaged proteins is toxic to the cancer cells. By showing that p97 promotes the ‘bounce-back’ of the proteasome, the work of Radhakrishnan et al. suggests that combining existing proteasome inhibitors with drugs that inhibit p97 could eventually lead to new, more effective, therapies for cancer or other diseases. DOI:http://dx.doi.org/10.7554/eLife.01856.002
Collapse
Affiliation(s)
- Senthil K Radhakrishnan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | | | | |
Collapse
|
22
|
Differential recognition of Old World and New World arenavirus envelope glycoproteins by subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P). J Virol 2013; 87:6406-14. [PMID: 23536681 DOI: 10.1128/jvi.00072-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The arenaviruses are an important family of emerging viruses that includes several causative agents of severe hemorrhagic fevers in humans that represent serious public health problems. A crucial step of the arenavirus life cycle is maturation of the envelope glycoprotein precursor (GPC) by the cellular subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P). Comparison of the currently known sequences of arenavirus GPCs revealed the presence of a highly conserved aromatic residue at position P7 relative to the SKI-1/S1P cleavage side in Old World and clade C New World arenaviruses but not in New World viruses of clades A and B or cellular substrates of SKI-1/S1P. Using a combination of molecular modeling and structure-function analysis, we found that residue Y285 of SKI-1/S1P, distal from the catalytic triad, is implicated in the molecular recognition of the aromatic "signature residue" at P7 in the GPC of Old World Lassa virus. Using a quantitative biochemical approach, we show that Y285 of SKI-1/S1P is crucial for the efficient processing of peptides derived from Old World and clade C New World arenavirus GPCs but not of those from clade A and B New World arenavirus GPCs. The data suggest that during coevolution with their mammalian hosts, GPCs of Old World and clade C New World viruses expanded the molecular contacts with SKI-1/S1P beyond the classical four-amino-acid recognition sequences and currently occupy an extended binding pocket.
Collapse
|
23
|
Dong XY, Tang SQ, Chen JD. Dual functions of Insig proteins in cholesterol homeostasis. Lipids Health Dis 2012; 11:173. [PMID: 23249523 PMCID: PMC3564778 DOI: 10.1186/1476-511x-11-173] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 12/05/2012] [Indexed: 01/29/2023] Open
Abstract
The molecular mechanism of how cells maintain cholesterol homeostasis has become clearer for the understanding of complicated association between sterol regulatory element-binding proteins (SREBPs), SREBP cleavage-activating protein (SCAP), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) and Insuin induced-genes (Insigs). The pioneering researches suggested that SREBP activated the transcription of genes encoding HMG-CoA reductase and all of the other enzymes involved in the synthesis of cholesterol and lipids. However, SREBPs can not exert their activities alone, they must form a complex with another protein, SCAP in the endoplasmic reticulum (ER) and translocate to Golgi. Insigs are sensors and mediators that regulate cholesterol homeostasis through binding to SCAP and HMG-CoA reductase in diverse tissues such as adipose tissue and liver, as well as the cultured cells. In this article, we aim to review on the dual functions of Insig protein family in cholesterol homeostasis.
Collapse
Affiliation(s)
- Xiao-Ying Dong
- College of Veterinary Medicine, South China Agricultural University, No,483 Wu Shan Road, Tian He District, Guangzhou, 510642, China.
| | | | | |
Collapse
|
24
|
Denard B, Lee C, Ye J. Doxorubicin blocks proliferation of cancer cells through proteolytic activation of CREB3L1. eLife 2012; 1:e00090. [PMID: 23256041 PMCID: PMC3524649 DOI: 10.7554/elife.00090] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 10/02/2012] [Indexed: 01/10/2023] Open
Abstract
Doxorubicin is used extensively for chemotherapy of diverse types of cancer, yet the mechanism through which it inhibits proliferation of cancer cells remains unclear. Here we report that doxorubicin stimulates de novo synthesis of ceramide, which in turn activates CREB3L1, a transcription factor synthesized as a membrane-bound precursor. Doxorubicin stimulates proteolytic cleavage of CREB3L1 by Site-1 Protease and Site-2 Protease, allowing the NH2-terminal domain of CREB3L1 to enter the nucleus where it activates transcription of genes encoding inhibitors of the cell cycle, including p21. Knockdown of CREB3L1 mRNA in human hepatoma Huh7 cells and immortalized human fibroblast SV589 cells conferred increased resistance to doxorubicin, whereas overexpression of CREB3L1 in human breast cancer MCF-7 cells markedly enhanced the sensitivity of these cells to doxorubicin. These results suggest that measurement of CREB3L1 expression may be a useful biomarker in identifying cancer cells sensitive to doxorubicin. DOI:http://dx.doi.org/10.7554/eLife.00090.001 Cancer is a broad term to describe over 200 diseases that are caused by cells proliferating in an out-of-control manner. Cell replication and division are normally very tightly regulated, and as cells become old, damaged or mutated, they are either repaired or undergo programmed cell death (apoptosis). However, if defective cells continue to replicate, the resulting clusters of abnormal cells can become cancerous. With so many different types of cancer, there is no ‘magic bullet’ to cure all of them. Many cancer therapies are targeted, relying on drugs that block the spread of cancer by interfering with specific molecules involved in the growth and progression of certain tumors. However, the fact that diseased cells replicate faster than normal cells in many forms of cancer makes it possible to use non-specific drugs, such as doxorubicin, to treat tumors when targeted therapies are not available. Doxorubicin can induce DNA breaks in a variety of different cancers by inhibiting the activity of topoisomerase II but a consistent relationship between the inhibition of this enzyme and the blocking of cell proliferation has not been established. This lack of understanding of the mechanism through which doxorubicin inhibits cell proliferation makes it difficult to identify cancer patients who are most likely to benefit from doxorubicin treatment. Denard et al. have now shown that doxorubicin blocks cell replication by cleaving a transcription factor called CREB3L1. This latest work builds on previous work in which they showed that cleavage of this transcription factor can inhibit the replication of cells infected with hepatitis C virus. It has been known since 2000 that CREB3L1 is a membrane protein with one end inside the lumen of the endoplasmic reticulum, and the other end (which is terminated with an NH2 group) in the cytosol of the cell. When CREB3L1 is cleaved, the NH2-terminal domain travels into the nucleus of the cell, where it drives the transcription of genes that suppress the cell cycle. Denard et al. clearly show that doxorubicin triggers the cleavage of CREB3L1 by stimulating the production of ceramide molecules. Thus, It might be possible, with further research, to use CREB3L1 as a biomarker to identify tumors that are suitable for treatment by doxorubicin. DOI:http://dx.doi.org/10.7554/eLife.00090.002
Collapse
Affiliation(s)
- Bray Denard
- Department of Molecular Genetics , University of Texas Southwestern Medical Center , Dallas , United States
| | | | | |
Collapse
|
25
|
Burri DJ, Pasquato A, da Palma JR, Igonet S, Oldstone MBA, Kunz S. The role of proteolytic processing and the stable signal peptide in expression of the Old World arenavirus envelope glycoprotein ectodomain. Virology 2012; 436:127-33. [PMID: 23218200 DOI: 10.1016/j.virol.2012.10.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 09/21/2012] [Accepted: 10/30/2012] [Indexed: 11/18/2022]
Abstract
Maturation of the arenavirus GP precursor (GPC) involves proteolytic processing by cellular signal peptidase and the proprotein convertase subtilisin kexin isozyme 1 (SKI-1)/site 1 protease (S1P), yielding a tripartite complex comprised of a stable signal peptide (SSP), the receptor-binding GP1, and the fusion-active transmembrane GP2. Here we investigated the roles of SKI-1/S1P processing and SSP in the biosynthesis of the recombinant GP ectodomains of lymphocytic choriomeningitis virus (LCMV) and Lassa virus (LASV). When expressed in mammalian cells, the LCMV and LASV GP ectodomains underwent processing by SKI-1/S1P, followed by dissociation of GP1 from GP2. The GP2 ectodomain spontaneously formed trimers as revealed by chemical cross-linking. The endogenous SSP, known to be crucial for maturation and transport of full-length arenavirus GPC was dispensable for processing and secretion of the soluble GP ectodomain, suggesting a specific role of SSP in the stable prefusion conformation and transport of full-length GPC.
Collapse
Affiliation(s)
- Dominique J Burri
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne CH-1011, Switzerland
| | | | | | | | | | | |
Collapse
|
26
|
Seidah NG, Prat A. The biology and therapeutic targeting of the proprotein convertases. Nat Rev Drug Discov 2012; 11:367-83. [PMID: 22679642 DOI: 10.1038/nrd3699] [Citation(s) in RCA: 588] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mammalian proprotein convertases constitute a family of nine secretory serine proteases that are related to bacterial subtilisin and yeast kexin. Seven of these (proprotein convertase 1 (PC1), PC2, furin, PC4, PC5, paired basic amino acid cleaving enzyme 4 (PACE4) and PC7) activate cellular and pathogenic precursor proteins by cleavage at single or paired basic residues, whereas subtilisin kexin isozyme 1 (SKI-1) and proprotein convertase subtilisin kexin 9 (PCSK9) regulate cholesterol and/or lipid homeostasis via cleavage at non-basic residues or through induced degradation of receptors. Proprotein convertases are now considered to be attractive targets for the development of powerful novel therapeutics. In this Review, we summarize the physiological functions and pathological implications of the proprotein convertases, and discuss proposed strategies to control some of their activities, including their therapeutic application and validation in selected disease states.
Collapse
Affiliation(s)
- Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal (affiliated to University of Montreal), 110 Pine Ave West, Montreal, Quebec H2W 1R7, Canada.
| | | |
Collapse
|
27
|
Burri DJ, Pasqual G, Rochat C, Seidah NG, Pasquato A, Kunz S. Molecular characterization of the processing of arenavirus envelope glycoprotein precursors by subtilisin kexin isozyme-1/site-1 protease. J Virol 2012; 86:4935-46. [PMID: 22357276 PMCID: PMC3347368 DOI: 10.1128/jvi.00024-12] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 02/14/2012] [Indexed: 01/27/2023] Open
Abstract
A crucial step in the life cycle of arenaviruses is the biosynthesis of the mature fusion-active viral envelope glycoprotein (GP) that is essential for virus-host cell attachment and entry. The maturation of the arenavirus GP precursor (GPC) critically depends on proteolytic processing by the cellular proprotein convertase (PC) subtilisin kexin isozyme-1 (SKI-1)/site-1 protease (S1P). Here we undertook a molecular characterization of the SKI-1/S1P processing of the GPCs of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) and the pathogenic Lassa virus (LASV). Previous studies showed that the GPC of LASV undergoes processing in the endoplasmic reticulum (ER)/cis-Golgi compartment, whereas the LCMV GPC is cleaved in a late Golgi compartment. Herein we confirm these findings and provide evidence that the SKI-1/S1P recognition site RRLL, present in the SKI-1/S1P prodomain and LASV GPC, but not in the LCMV GPC, is crucial for the processing of the LASV GPC in the ER/cis-Golgi compartment. Our structure-function analysis revealed that the cleavage of arenavirus GPCs, but not cellular substrates, critically depends on the autoprocessing of SKI-1/S1P, suggesting differences in the processing of cellular and viral substrates. Deletion mutagenesis showed that the transmembrane and intracellular domains of SKI-1/S1P are dispensable for arenavirus GPC processing. The expression of a soluble form of the protease in SKI-I/S1P-deficient cells resulted in the efficient processing of arenavirus GPCs and rescued productive virus infection. However, exogenous soluble SKI-1/S1P was unable to process LCMV and LASV GPCs displayed at the surface of SKI-I/S1P-deficient cells, indicating that GPC processing occurs in an intracellular compartment. In sum, our study reveals important differences in the SKI-1/S1P processing of viral and cellular substrates.
Collapse
Affiliation(s)
- Dominique J. Burri
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Giulia Pasqual
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Cylia Rochat
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Nabil G. Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Canada
| | - Antonella Pasquato
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Stefan Kunz
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
28
|
Chevet E. From stress specificity to basal necessity: ATF6 uprising. Focus on “Pancreatic β-cells depend on basal expression of active ATF6α-p50 for cell survival even under nonstress conditions”. Am J Physiol Cell Physiol 2012; 302:C966-7. [DOI: 10.1152/ajpcell.00001.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Eric Chevet
- Inserm U1053 and Université Bordeaux Segalen, Bordeaux, France
| |
Collapse
|
29
|
Zandberg WF, Gao N, Kumarasamy J, Lehrman MA, Seidah NG, Pinto BM. 5-thiomannosides block the biosynthesis of dolichol-linked oligosaccharides and mimic class I congenital disorders of glycosylation. Chembiochem 2012; 13:392-401. [PMID: 22262650 PMCID: PMC3433809 DOI: 10.1002/cbic.201100647] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Indexed: 01/05/2023]
Abstract
In a cell-based assay for novel inhibitors, we have discovered that two glycosides of 5-thiomannose, each containing an interglycosidic nitrogen atom, prevented the correct zymogen processing of the prohormone proopiomelanocortinin (POMC) and the transcription factor sterol-regulatory element-binding protein-2 (SREBP-2) in mouse pituitary cells and Chinese hamster ovary (CHO) cells, respectively. In the case of SREBP-2, these effects were correlated with the altered N-linked glycosylation of subtilisin/kexin-like isozyme-1 (SKI-1), the protease responsible for SREBP-2 processing under sterol-limiting conditions. Further examination of the effects of these compounds in CHO cells showed that they cause extensive protein hypoglycosylation in a manner similar to type I congenital disorders of glycosylation (CDGs) since the remaining N-glycans in treated cells were complete (normal) structures. The under-glycosylation of glycoproteins in 5-thiomannoside-treated cells is now shown to be caused by the compromised biosynthesis of the dolichol-linked oligosaccharide (DLO) N-glycosylation donor, although the nucleotide sugars required for the synthesis of DLOs were neither reduced under these conditions, nor were their effects reversed upon the addition of exogenous mannose. Analysis of DLO intermediates by fluorophore-assisted carbohydrate electrophoresis demonstrated that 5-thiomannose-containing glycosides block DLO biosynthesis most likely at a stage prior to the GlcNAc(2) Man(3) intermediate, on the cytosolic face of the endoplasmic reticulum.
Collapse
Affiliation(s)
- Wesley F Zandberg
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Ningguo Gao
- Department of Pharmacology, UT-Southwestern Medical Center, Dallas, Texas, USA, 75390-9041
| | | | - Mark A Lehrman
- Department of Pharmacology, UT-Southwestern Medical Center, Dallas, Texas, USA, 75390-9041
| | - Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, 110 Pine Avenue West Montreal, QC H2W 1R7, Canada
| | - B Mario Pinto
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| |
Collapse
|
30
|
Evaluation of the anti-arenaviral activity of the subtilisin kexin isozyme-1/site-1 protease inhibitor PF-429242. Virology 2011; 423:14-22. [PMID: 22154237 DOI: 10.1016/j.virol.2011.11.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/08/2011] [Accepted: 11/10/2011] [Indexed: 11/23/2022]
Abstract
The cellular protease subtilisin kexin isozyme-1 (SKI-1)/site-1 protease (S1P) is implicated in the proteolytic processing of the viral envelope glycoprotein precursor (GPC) of arenaviruses, a step strictly required for production of infectious progeny. The small molecule SKI-1/S1P inhibitor PF-429242 was shown to have anti-viral activity against Old World arenaviruses. Here we extended these studies and show that PF-429242 also inhibits GPC processing and productive infection of New World arenaviruses, making PF-429242 a broadly active anti-arenaviral drug. In combination therapy, PF-429242 potentiated the anti-viral activity of ribavirin, indicating a synergism between the two drugs. A hallmark of arenaviruses is their ability to establish persistent infection in vitro and in vivo. Notably, PF-429242 was able to efficiently and rapidly clear persistent infection by arenaviruses. Interruption of drug treatment did not result in re-emergence of infection, indicating that PF-429242 treatment leads to virus extinction.
Collapse
|
31
|
Marschner K, Kollmann K, Schweizer M, Braulke T, Pohl S. A key enzyme in the biogenesis of lysosomes is a protease that regulates cholesterol metabolism. Science 2011; 333:87-90. [PMID: 21719679 DOI: 10.1126/science.1205677] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mucolipidosis II is a severe lysosomal storage disorder caused by defects in the α and β subunits of the hexameric N-acetylglucosamine-1-phosphotransferase complex essential for the formation of the mannose 6-phosphate targeting signal on lysosomal enzymes. Cleavage of the membrane-bound α/β-subunit precursor by an unknown protease is required for catalytic activity. Here we found that the α/β-subunit precursor is cleaved by the site-1 protease (S1P) that activates sterol regulatory element-binding proteins in response to cholesterol deprivation. S1P-deficient cells failed to activate the α/β-subunit precursor and exhibited a mucolipidosis II-like phenotype. Thus, S1P functions in the biogenesis of lysosomes, and lipid-independent phenotypes of S1P deficiency may be caused by lysosomal dysfunction.
Collapse
Affiliation(s)
- Katrin Marschner
- Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | | | | | | |
Collapse
|
32
|
Zandberg WF, Benjannet S, Hamelin J, Pinto BM, Seidah NG. N-glycosylation controls trafficking, zymogen activation and substrate processing of proprotein convertases PC1/3 and subtilisin kexin isozyme-1. Glycobiology 2011; 21:1290-300. [PMID: 21527438 DOI: 10.1093/glycob/cwr060] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The limited proteolysis of proteins by the proprotein convertases (PCs) is a common means of producing bioactive proteins or peptides. The PCs are associated with numerous human pathologies and their activity can be reduced through the use of specific inhibitors. Here, we demonstrate an alternative approach to inhibiting PCs by altering their N-glycosylation. Through site-directed mutagenesis, we show that the convertase PC1/3 contains two N-glycans, only one of which is critical for its prosegment cleavage. The exact structure of PC1/3 N-glycans does not significantly affect its zymogen activation within endocrine cells, but glycosylation of Asn(146) is critical. Processing of the PC1/3's substrate proopiomelanocortin (POMC) was used in a cell-based assay to screen a collection of 45 compounds structurally related to known glycosidase inhibitors. Two 5-thiomannose-containing disaccharide derivatives were discovered to block PC1/3 and POMC processing into the analgesic peptide β-endorphin. These compounds also reduced the zymogen activation of the convertase subtilisin kexin isozyme-1 (SKI-1), blocked the processing of its substrate the sterol regulatory element-binding protein SREBP-2 and altered its glycosylation. Thus, modification of PC glycosylation may also be a means of blocking their activity, an effect which, in the case of SKI-1, may be of possible therapeutic use since SREBP-2 regulates sterol levels including cholesterol biosynthesis and its metabolism.
Collapse
Affiliation(s)
- Wesley F Zandberg
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | | | | | | | | |
Collapse
|
33
|
Vinothkumar KR, Strisovsky K, Andreeva A, Christova Y, Verhelst S, Freeman M. The structural basis for catalysis and substrate specificity of a rhomboid protease. EMBO J 2010; 29:3797-809. [PMID: 20890268 DOI: 10.1038/emboj.2010.243] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 09/06/2010] [Indexed: 12/28/2022] Open
Abstract
Rhomboids are intramembrane proteases that use a catalytic dyad of serine and histidine for proteolysis. They are conserved in both prokaryotes and eukaryotes and regulate cellular processes as diverse as intercellular signalling, parasitic invasion of host cells, and mitochondrial morphology. Their widespread biological significance and consequent medical potential provides a strong incentive to understand the mechanism of these unusual enzymes for identification of specific inhibitors. In this study, we describe the structure of Escherichia coli rhomboid GlpG covalently bound to a mechanism-based isocoumarin inhibitor. We identify the position of the oxyanion hole, and the S₁- and S₂'-binding subsites of GlpG, which are the key determinants of substrate specificity. The inhibitor-bound structure suggests that subtle structural change is sufficient for catalysis, as opposed to large changes proposed from previous structures of unliganded GlpG. Using bound inhibitor as a template, we present a model for substrate binding at the active site and biochemically test its validity. This study provides a foundation for a structural explanation of rhomboid specificity and mechanism, and for inhibitor design.
Collapse
|
34
|
Targeting the proteolytic processing of the viral glycoprotein precursor is a promising novel antiviral strategy against arenaviruses. J Virol 2010; 84:573-84. [PMID: 19846507 DOI: 10.1128/jvi.01697-09] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A crucial step in the arenavirus life cycle is the biosynthesis of the viral envelope glycoprotein (GP) responsible for virus attachment and entry. Processing of the GP precursor (GPC) by the cellular proprotein convertase site 1 protease (S1P), also known as subtilisin-kexin-isozyme 1 (SKI-1), is crucial for cell-to-cell propagation of infection and production of infectious virus. Here, we sought to evaluate arenavirus GPC processing by S1P as a target for antiviral therapy using a recently developed peptide-based S1P inhibitor, decanoyl (dec)-RRLL-chloromethylketone (CMK), and the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV). To control for off-target effects of dec-RRLL-CMK, we employed arenavirus reverse genetics to introduce a furin recognition site into the GPC of LCMV. The rescued mutant virus grew to normal titers, and the processing of its GPC critically depended on cellular furin, but not S1P. Treatment with the S1P inhibitor dec-RRLL-CMK resulted in specific blocking of viral spread and virus production of LCMV. Combination of the protease inhibitor with ribavirin, currently used clinically for treatment of human arenavirus infections, resulted in additive drug effects. In cells deficient in S1P, the furin-dependent LCMV variant established persistent infection, whereas wild-type LCMV underwent extinction without the emergence of S1P-independent escape variants. Together, the potent antiviral activity of an inhibitor of S1P-dependent GPC cleavage, the additive antiviral effect with ribavirin, and the low probability of emergence of S1P-independent viral escape variants make S1P-mediated GPC processing by peptide-derived inhibitors a promising strategy for the development of novel antiarenaviral drugs.
Collapse
|
35
|
Maisa A, Ströher U, Klenk HD, Garten W, Strecker T. Inhibition of Lassa virus glycoprotein cleavage and multicycle replication by site 1 protease-adapted alpha(1)-antitrypsin variants. PLoS Negl Trop Dis 2009; 3:e446. [PMID: 19488405 PMCID: PMC2685025 DOI: 10.1371/journal.pntd.0000446] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 04/28/2009] [Indexed: 12/02/2022] Open
Abstract
Background Proteolytic processing of the Lassa virus envelope glycoprotein precursor GP-C by the host proprotein convertase site 1 protease (S1P) is a prerequisite for the incorporation of the subunits GP-1 and GP-2 into viral particles and, hence, essential for infectivity and virus spread. Therefore, we tested in this study the concept of using S1P as a target to block efficient virus replication. Methodology/Principal Finding We demonstrate that stable cell lines inducibly expressing S1P-adapted α1-antitrypsin variants inhibit the proteolytic maturation of GP-C. Introduction of the S1P recognition motifs RRIL and RRLL into the reactive center loop of α1-antitrypsin resulted in abrogation of GP-C processing by endogenous S1P to a similar level observed in S1P-deficient cells. Moreover, S1P-specific α1-antitrypsins significantly inhibited replication and spread of a replication-competent recombinant vesicular stomatitis virus expressing the Lassa virus glycoprotein GP as well as authentic Lassa virus. Inhibition of viral replication correlated with the ability of the different α1-antitrypsin variants to inhibit the processing of the Lassa virus glycoprotein precursor. Conclusions/Significance Our data suggest that glycoprotein cleavage by S1P is a promising target for the development of novel anti-arenaviral strategies. The virus family Arenaviridae includes several hemorrhagic fever causing agents such as Lassa, Guanarito, Junin, Machupo, and Sabia virus that pose a major public health concern to the human population in West African and South American countries. Current treatment options to control fatal outcome of disease are limited to the ribonucleoside analogue ribavirin, although its use has some significant limitations. The lack of effective treatment alternatives emphasizes the need for novel antiviral therapeutics to counteract these life-threatening infections. Maturation cleavage of the viral envelope glycoprotein by the host cell proprotein convertase site 1 protease (S1P) is critical for infectious virion production of several pathogenic arenaviruses. This finding makes this protease an attractive target for the development of novel anti-arenaviral therapeutics. We demonstrate here that highly selective S1P-adapted α1-antitrypsins have the potential to efficiently inhibit glycoprotein processing, which resulted in reduced Lassa virus replication. Our findings suggest that S1P should be considered as an antiviral target and that further optimization of modified α1-antitrypsins could lead to potent and specific S1P inhibitors with the potential for treatment of certain viral hemorrhagic fevers.
Collapse
Affiliation(s)
- Anna Maisa
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Ute Ströher
- Molecular Virology & Antiviral Approaches Unit, Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
- Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Hans-Dieter Klenk
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Wolfgang Garten
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail:
| | - Thomas Strecker
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| |
Collapse
|
36
|
Brown MS, Goldstein JL. Cholesterol feedback: from Schoenheimer's bottle to Scap's MELADL. J Lipid Res 2009; 50 Suppl:S15-27. [PMID: 18974038 PMCID: PMC2674699 DOI: 10.1194/jlr.r800054-jlr200] [Citation(s) in RCA: 365] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 10/29/2008] [Indexed: 01/12/2023] Open
Abstract
Cholesterol biosynthesis is among the most intensely regulated processes in biology. Synthetic rates vary over hundreds of fold depending on the availability of an external source of cholesterol. Studies of this feedback regulatory process have a rich history. The field began 75 years ago when Rudolf Schoenheimer measured cholesterol balance in mice in a bottle. He found that cholesterol feeding led to decreased cholesterol synthesis, thereby introducing the general phenomenon by which end products of biosynthetic pathways inhibit their own synthesis. Recently, cholesterol feedback has been explained at a molecular level with the discovery of membrane-bound transcription factors called sterol regulatory element-binding proteins (SREBPs), and an appreciation of the sterol-sensing role of their partner, an escort protein called Scap. The key element in Scap is a hexapeptide sequence designated MELADL (rhymes with bottle). Thus, over 75 years, Schoenheimer's bottle led to Scap's MELADL. In addition to their basic importance in membrane biology, these studies have implications for the regulation of plasma cholesterol levels and consequently for the development of atherosclerotic plaques, myocardial infarctions, and strokes. In this article we review the major milestones in the cholesterol feedback story.
Collapse
Affiliation(s)
- Michael S. Brown
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Joseph L. Goldstein
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| |
Collapse
|
37
|
Site 1 protease is required for proteolytic processing of the glycoproteins of the South American hemorrhagic fever viruses Junin, Machupo, and Guanarito. J Virol 2008; 82:6045-51. [PMID: 18400865 DOI: 10.1128/jvi.02392-07] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cellular proprotein convertase site 1 protease (S1P) has been implicated in the proteolytic processing of the glycoproteins (GPs) of Old World arenaviruses. Here we report that S1P is also involved in the processing of the GPs of the genetically more-distant South American hemorrhagic fever viruses Guanarito, Machupo, and Junin. Efficient cleavage of Guanarito virus GP, whose protease recognition sites deviate from the reported S1P consensus sequence, indicates a broader specificity of S1P than anticipated. Lack of GP processing of Junin virus dramatically reduced production of infectious virus and prevented cell-to-cell propagation. Infection of S1P-deficient cells resulted in viral persistence over several weeks without the emergence of escape variants able to use other cellular proteases for GP processing.
Collapse
|
38
|
Bergeron E, Vincent MJ, Nichol ST. Crimean-Congo hemorrhagic fever virus glycoprotein processing by the endoprotease SKI-1/S1P is critical for virus infectivity. J Virol 2007; 81:13271-6. [PMID: 17898072 PMCID: PMC2169102 DOI: 10.1128/jvi.01647-07] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Crimean-Congo hemorrhagic fever virus (CCHFV) causes severe human disease. The CCHFV medium RNA encodes a polyprotein which is proteolytically processed to yield the glycoprotein precursors PreGn and PreGc, followed by structural glycoproteins Gn and Gc. Subtilisin kexin isozyme-1/site-1 protease (SKI-1/S1P) plays a central role in Gn processing. Here we show that CCHFV-infected cells deficient in SKI-1/S1P produce no infectious virus, although PreGn and PreGc accumulated normally in the Golgi apparatus, the site of virus assembly. Only nucleoprotein-containing particles which lacked virus glycoproteins (Gn/Gc or PreGn/PreGc) were secreted. Complementation of SKI-1/S1P-deficient cells with a SKI-1/S1P expression vector restored release of infectious virus (>10(6) PFU/ml), confirming that SKI-1/S1P processing is required for incorporation of viral glycoproteins. SKI-1/S1P may represent a promising antiviral target.
Collapse
Affiliation(s)
- Eric Bergeron
- Special Pathogens Branch, Division of Viral and Rickettsial Diseases, National Center for Zoonotic, Vector-borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | | | | |
Collapse
|
39
|
Abstract
Subtilisin kexin isozyme-1 (SKI-1) represents the first mammalian member of secretory subtilisin-like processing enzymes that cleaves after nonbasic residues. It is synthesized as an inactive precursor that undergoes three sequential autocatalytic processing steps of its N-terminal prosegment and an ectodomain shedding at a site near the transmembrane domain. The various cellular functions of SKI-1 emphasize the need to understand the sites of its activation and shedding. We have previously shown that SKI-1 undergoes autocatalytic shedding at the sequence KHQKLL(953) downward arrow, resulting in a membrane-bound stump called St-1 (amino acids 954-1052). However, little is known about the cellular localization of SKI-1 or its shed forms. In the present study, we have further identified a smaller C-terminal fragment St-2 generated closer to the transmembrane domain. By sequencing and mass spectrometric analysis, the start site and the molecular mass of St-2 were determined. Site-directed mutagenesis revealed the critical amino acid involved in this novel process. Mutation of Met(990) to M990A, M990I, and M990L failed to generate St-2, suggesting an internal alternate translation event at Met(990), as confirmed by an in vitro transcription/translation assay. Confocal microscopy defined the subcellular localization of SKI-1 and its fragments. The data show that most of membrane-bound SKI-1 and its stumps St-1 and St-2 localize to the Golgi and can enter the endosomal/lysosomal compartments but do not sort to the cell surface. Deletion studies showed that the transmembrane domain of SKI-1 determines its trafficking. Finally, rSt-1 and rSt-2 seem to affect the processing of ATF6 by SKI-1, but cellular stress does not regulate the production of St-2.
Collapse
Affiliation(s)
- Philomena Pullikotil
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada and
| | - Suzanne Benjannet
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada and
| | - Janice Mayne
- Hormones, Growth, and Development, Ottawa Health Research Institute, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada
| | - Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada and.
| |
Collapse
|
40
|
Bartz R, Seemann J, Zehmer JK, Serrero G, Chapman KD, Anderson RG, Liu P. Evidence that mono-ADP-ribosylation of CtBP1/BARS regulates lipid storage. Mol Biol Cell 2007; 18:3015-25. [PMID: 17538025 PMCID: PMC1949384 DOI: 10.1091/mbc.e06-09-0869] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mono-ADP-ribosylation is emerging as an important posttranslational modification that modulates a variety of cell signaling pathways. Here, we present evidence that mono-ADP-ribosylation of the transcriptional corepressor C terminal binding protein, brefeldin A (BFA)-induced ADP-ribosylated substrate (CtBP1/BARS) regulates neutral lipid storage in droplets that are surrounded by a monolayer of phospholipid and associated proteins. CtBP1/BARS is an NAD-binding protein that becomes ribosylated when cells are exposed to BFA. Both endogenous lipid droplets and droplets enlarged by oleate treatment are lost after 12-h exposure to BFA. Lipid loss requires new protein synthesis, and it is blocked by multiple ribosylation inhibitors, but it is not stimulated by disruption of the Golgi apparatus or the endoplasmic reticulum unfolded protein response. Small interfering RNA knockdown of CtBP1/BARS mimics the effect of BFA, and mouse embryonic fibroblasts derived from embryos that are deficient in CtBP1/BARS seem to be defective in lipid accumulation. We conclude that mono-ADP-ribosylation of CtBP1/BARS inactivates its repressor function, which leads to the activation of genes that regulate neutral lipid storage.
Collapse
Affiliation(s)
- René Bartz
- *Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Joachim Seemann
- *Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - John K. Zehmer
- *Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | | | - Kent D. Chapman
- Department of Biological Sciences, University of North Texas, Denton, TX 76203
| | - Richard G.W. Anderson
- *Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Pingsheng Liu
- *Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| |
Collapse
|
41
|
Ko MH, Puglielli L. The sterol carrier protein SCP-x/pro-SCP-2 gene has transcriptional activity and regulates the Alzheimer disease gamma-secretase. J Biol Chem 2007; 282:19742-52. [PMID: 17485462 DOI: 10.1074/jbc.m611426200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The sterol carrier protein SCP-x/pro-SCP-2 gene is a fusion gene having two initiation sites that generate a long (SCP-x; 58.9-kDa) and a short (pro-SCP-2; 15.4-kDa) product, both containing the common SCP-2 module at the C terminus. Here, we show that SCP-x is processed on the peroxisomal surface to liberate a short C-terminal product of 12.9 kDa. This fragment has DNA binding activity in vivo and in vitro, as assessed by chromatin immunoprecipitation analysis, DNA-protein pull-down, electrophoretic mobility shift assay, and luciferase reporter activity. In addition, it is preferentially found in the nucleus where it regulates the transcription of CD147, the regulatory subunit of the Alzheimer disease gamma-secretase. Overexpression of SCP-x increased, whereas antisense oligonucleotides against scp-x decreased, the generation of the above transcription factor. Both biochemical and genetic approaches indicate that pro-SCP-2 acts as a competitive inhibitor of SCP-x processing, thereby controlling the release of the 12.9-kDa transcriptionally active fragment. The transcription regulatory function of pro-SCP-2 requires a peroxisomal targeting sequence at the C terminus and a 20-amino acid leading sequence at the N terminus. Finally, pro-SCP-2 has also cholesterol carrier activity, which is functionally separated from the transcription regulatory one. In conclusion, we have identified two novel functions (transcriptional and transcription regulatory) of the SCP-x/pro-SCP-2 gene that have impact on gamma-secretase activity.
Collapse
Affiliation(s)
- Mi Hee Ko
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | | |
Collapse
|
42
|
Radhakrishnan A, Ikeda Y, Kwon HJ, Brown MS, Goldstein JL. Sterol-regulated transport of SREBPs from endoplasmic reticulum to Golgi: oxysterols block transport by binding to Insig. Proc Natl Acad Sci U S A 2007; 104:6511-8. [PMID: 17428920 PMCID: PMC1851665 DOI: 10.1073/pnas.0700899104] [Citation(s) in RCA: 445] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cholesterol synthesis in animals is controlled by the regulated transport of sterol regulatory element-binding proteins (SREBPs) from the endoplasmic reticulum to the Golgi, where the transcription factors are processed proteolytically to release active fragments. Transport is inhibited by either cholesterol or oxysterols, blocking cholesterol synthesis. Cholesterol acts by binding to the SREBP-escort protein Scap, thereby causing Scap to bind to anchor proteins called Insigs. Here, we show that oxysterols act by binding to Insigs, causing Insigs to bind to Scap. Mutational analysis of the six transmembrane helices of Insigs reveals that the third and fourth are important for Insig's binding to oxysterols and to Scap. These studies define Insigs as oxysterol-binding proteins, explaining the long-known ability of oxysterols to inhibit cholesterol synthesis in animal cells.
Collapse
Affiliation(s)
| | | | - Hyock Joo Kwon
- Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Michael S. Brown
- Departments of *Molecular Genetics and
- To whom correspondence may be addressed. E-mail: or
| | - Joseph L. Goldstein
- Departments of *Molecular Genetics and
- To whom correspondence may be addressed. E-mail: or
| |
Collapse
|
43
|
Gurcel L, Abrami L, Girardin S, Tschopp J, van der Goot FG. Caspase-1 activation of lipid metabolic pathways in response to bacterial pore-forming toxins promotes cell survival. Cell 2006; 126:1135-45. [PMID: 16990137 DOI: 10.1016/j.cell.2006.07.033] [Citation(s) in RCA: 411] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 04/12/2006] [Accepted: 07/24/2006] [Indexed: 11/27/2022]
Abstract
Many pathogenic organisms produce pore-forming toxins as virulence factors. Target cells however mount a response to such membrane damage. Here we show that toxin-induced membrane permeabilization leads to a decrease in cytoplasmic potassium, which promotes the formation of a multiprotein oligomeric innate immune complex, called the inflammasome, and the activation of caspase-1. Further, we find that when rendered proteolytic in this context caspase-1 induces the activation of the central regulators of membrane biogenesis, the Sterol Regulatory Element Binding Proteins (SREBPs), which in turn promote cell survival upon toxin challenge possibly by facilitating membrane repair. This study highlights that, in addition to its well-established role in triggering inflammation via the processing of the precursor forms of interleukins, caspase-1 has a broader role, in particular linking the intracellular ion composition to lipid metabolic pathways, membrane biogenesis, and survival.
Collapse
Affiliation(s)
- Laure Gurcel
- Department Microbiology and Molecular Medicine, University of Geneva, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland
| | | | | | | | | |
Collapse
|
44
|
Yang C, McDonald JG, Patel A, Zhang Y, Umetani M, Xu F, Westover EJ, Covey DF, Mangelsdorf DJ, Cohen JC, Hobbs HH. Sterol intermediates from cholesterol biosynthetic pathway as liver X receptor ligands. J Biol Chem 2006; 281:27816-26. [PMID: 16857673 DOI: 10.1074/jbc.m603781200] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The liver X receptors (LXRs) are ligand-activated transcription factors that regulate the expression of genes controlling lipid metabolism. Oxysterols bind LXRs with high affinity in vitro and are implicated as ligands for the receptor. We showed previously that accumulation of selected dietary sterols, in particular stigmasterol, is associated with activation of LXR in vivo. In the course of the defining of structural features of stigmasterol that confer LXR agonist activity, we determined that the presence of an unsaturated bond in the side chain of the sterol was necessary and sufficient for activity, with the C-24 unsaturated cholesterol precursor sterols desmosterol and zymosterol exerting the largest effects. Desmosterol failed to increase expression of the LXR target gene, ABCA1, in LXRalpha/beta-deficient mouse fibroblasts, but was fully active in cells lacking cholesterol 24-, 25-, and 27-hydroxylase; thus, the effect of desmosterol was LXR-dependent and did not require conversion to a side chain oxysterol. Desmosterol bound to purified LXRalpha and LXRbeta in vitro and supported the recruitment of steroid receptor coactivator 1. Desmosterol also inhibited processing of the sterol response element-binding protein-2 and reduced expression of hydroxymethylglutaryl-CoA reductase. These observations are consistent with specific intermediates in the cholesterol biosynthetic pathway regulating lipid homeostasis through both the LXR and sterol response element-binding protein pathways.
Collapse
Affiliation(s)
- Chendong Yang
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, 75390, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Zhang K, Shen X, Wu J, Sakaki K, Saunders T, Rutkowski DT, Back SH, Kaufman RJ. Endoplasmic reticulum stress activates cleavage of CREBH to induce a systemic inflammatory response. Cell 2006; 124:587-99. [PMID: 16469704 DOI: 10.1016/j.cell.2005.11.040] [Citation(s) in RCA: 628] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 09/08/2005] [Accepted: 11/11/2005] [Indexed: 12/16/2022]
Abstract
Regulated intramembrane proteolysis (RIP) of endoplasmic reticulum (ER) membrane-anchored transcription factors is known to maintain sterol homeostasis and to mediate the unfolded protein response (UPR). Here, we identified CREBH as a RIP-regulated liver-specific transcription factor that is cleaved upon ER stress and required to activate expression of acute phase response (APR) genes. Proinflammatory cytokines increase expression of ER membrane-anchored CREBH. In response to ER stress, CREBH is cleaved by site-1 and site-2 proteases to liberate an amino-terminal fragment that transits to the nucleus to activate transcription of the genes encoding serum amyloid P-component (SAP) and C-reactive protein (CRP). Proinflammatory cytokines and lipopolysaccharide activate the UPR and induce cleavage of CREBH in the liver in vivo. Together, our studies delineate a molecular mechanism for activation of an ER-localized transcription factor, CREBH, and reveal an unprecedented link by which ER stress initiates an acute inflammatory response.
Collapse
Affiliation(s)
- Kezhong Zhang
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Xu F, Rychnovsky SD, Belani JD, Hobbs HH, Cohen JC, Rawson RB. Dual roles for cholesterol in mammalian cells. Proc Natl Acad Sci U S A 2005; 102:14551-6. [PMID: 16199524 PMCID: PMC1239893 DOI: 10.1073/pnas.0503590102] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structural features of sterols required to support mammalian cell growth have not been fully defined. Here, we use mutant CHO cells that synthesize only small amounts of cholesterol to test the capacity of various sterols to support growth. Sterols with minor modifications of the side chain (e.g., campesterol, beta-sitosterol, and desmosterol) supported long-term growth of mutant cells, but sterols with more complex modifications of the side chain, the sterol nucleus, or the 3-hydroxy group did not. After 60 days in culture, the exogenous sterol comprised >90% of cellular sterols. Inactivation of residual endogenous synthesis with the squalene epoxidase inhibitor NB-598 prevented growth in beta-sitosterol and greatly reduced growth in campesterol. Growth of cells cultured in beta-sitosterol and NB-598 was restored by adding small amounts of cholesterol to the medium. Surprisingly, enantiomeric cholesterol also supported cell growth, even in the presence of NB-598. Thus, sterols fulfill two roles in mammalian cells: (i) a bulk membrane requirement in which phytosterols can substitute for cholesterol and (ii) other processes that specifically require small amounts of cholesterol but are not enantioselective.
Collapse
Affiliation(s)
- Fang Xu
- Center for Human Nutrition, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | | | | | | | | | | |
Collapse
|
47
|
Lee PCW, Sever N, Debose-Boyd RA. Isolation of Sterol-resistant Chinese Hamster Ovary Cells with Genetic Deficiencies in Both Insig-1 and Insig-2. J Biol Chem 2005; 280:25242-9. [PMID: 15866869 DOI: 10.1074/jbc.m502989200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Insig-1 and Insig-2, a pair of endoplasmic reticulum (ER) membrane proteins, mediate feedback control of cholesterol synthesis through their sterol-dependent binding to the following two polytopic ER membrane proteins: sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Sterol-induced binding of Insigs to SCAP prevents the proteolytic processing of SREBPs, membrane-bound transcription factors that enhance the synthesis of cholesterol, by retaining complexes between SCAP and SREBP in the ER. Sterol-induced binding of Insigs to reductase leads to the ubiquitination and ER-associated degradation of the enzyme, thereby slowing a rate-controlling step in cholesterol synthesis. Here we report the isolation of a new line of mutant Chinese hamster ovary cells, designated SRD-15, deficient in both Insig-1 and Insig-2. The SRD-15 cells were produced by gamma-irradiation of Insig-1-deficient SRD-14 cells, followed by selection in high levels of the oxysterol, 25-hydroxycholesterol. Sterols neither inhibit SREBP processing nor promote reductase ubiquitination/degradation in SRD-15 cells. Sterol regulation of SREBP processing and reductase ubiquitination/degradation is fully restored in SRD-15 cells when they are transfected with expression plasmids encoding either Insig-1 or Insig-2. These results demonstrate an absolute requirement for Insig proteins in the regulatory system that mediates lipid homeostasis in animal cells.
Collapse
Affiliation(s)
- Peter C W Lee
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046, USA
| | | | | |
Collapse
|
48
|
Olry A, Chastagner P, Israël A, Brou C. Generation and characterization of mutant cell lines defective in gamma-secretase processing of Notch and amyloid precursor protein. J Biol Chem 2005; 280:28564-71. [PMID: 15958385 DOI: 10.1074/jbc.m502199200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Several type I integral membrane proteins, such as the Notch receptor or the amyloid precursor protein, are cleaved in their intramembrane domain by a gamma-secretase enzyme, which is carried within a multiprotein complex. These cleavages generate molecules that are involved in intracellular or extracellular signaling. At least four transmembrane proteins belong to the gamma-secretase complex: presenilin, nicastrin, Aph-1, and Pen-2. It is still unclear whether these proteins are the only components of the complex and whether a unique complex is involved in the different gamma-secretase cleavage events. We have set up a genetic screen based on the permanent acquisition or loss of an antibiotic resistance depending on the presence of an active gamma-secretase able to cleave a Notch-derived substrate. We selected clones deficient in gamma-secretase activity using this screen on mammalian cells after random mutagenesis. We further analyzed two of these clones and identified previously undescribed mutations in the nicastrin gene. The first mutation abolishes nicastrin production, and the second mutation, a point mutation in the ectodomain, abolishes nicastrin maturation. In both cases, gamma-secretase activity on Notch and APP is impaired.
Collapse
Affiliation(s)
- Annie Olry
- Unité de Signalisation Moléculaire et Activation Cellulaire, URA 2582, CNRS, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France
| | | | | | | |
Collapse
|
49
|
Maeda M, Ishida A, Ni L, Kobayashi A. Isolation of CHO-K1 clones defective in cAMP-dependent proteolysis, as determined by the stability of exogenously expressed GATA-6. Biochem Biophys Res Commun 2005; 329:140-6. [PMID: 15721285 DOI: 10.1016/j.bbrc.2005.01.118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Indexed: 12/01/2022]
Abstract
Degradation of the GATA-6(Delta50) protein expressed in a CHO-K1 clone (tc1-17a) is stimulated in the presence of dbcAMP through proteasome without new protein synthesis [FEBS Lett. 408 (1997) 301], whereas the intrinsic GC-box-binding protein was stable. To examine the cellular mechanism responsible for this specific degradation of GATA-6(Delta50), we initially introduced the blasticidin-S deaminase gene carrying a promoter with GATA motifs that are recognized by GATA-6. The resulting cell line (tc2G2) grew in the presence of blasticidin S. However, the presence of both blasticidin S and dbcAMP was lethal due to degradation of GATA-6. Cells resistant to such lethality were isolated by chemical mutagenesis. The GATA-6(Delta50) in these resistant cells was stable in the presence of dbcAMP in contrast to that in the parent tc2G2 cells, as determined by gel-mobility shift analysis and Western blotting. These clones could be beneficial for identification and characterization of the components participating in the signaling pathway for both protein degradation and cAMP-dependent biological processes.
Collapse
Affiliation(s)
- Masatomo Maeda
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan.
| | | | | | | |
Collapse
|
50
|
Abstract
The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane proteins are members of the basic helix-loop-helix-leucine zipper (bHLH-Zip) family of transcription factors. They activate the expression of at least 30 genes involved in the synthesis of cholesterol and lipids. SREBPs are synthesized as precursor proteins in the endoplasmic reticulum (ER), where they form a complex with another protein, SREBP cleavage activating protein (SCAP). The SCAP molecule contains a sterol sensory domain. In the presence of high cellular sterol concentrations SCAP confines SREBP to the ER. With low cellular concentrations, SCAP escorts SREBP to activation in the Golgi. There, SREBP undergoes two proteolytic cleavage steps to release the mature, biologically active transcription factor, nuclear SREBP (nSREBP). nSREBP translocates to the nucleus and binds to sterol response elements (SRE) in the promoter/enhancer regions of target genes. Additional transcription factors are required to activate transcription of these genes. Three different SREBPs are known, SREBPs-1a, -1c and -2. SREBP-1a and -1c are isoforms produced from a single gene by alternate splicing. SREBP-2 is encoded by a different gene and does not display any isoforms. It appears that SREBPs alone, in the sequence described above, can exert complete control over cholesterol synthesis, whereas many additional factors (hormones, cytokines, etc.) are required for complete control of lipid metabolism. Medicinal manipulation of the SREBP/SCAP system is expected to prove highly beneficial in the management of cholesterol-related disease.
Collapse
Affiliation(s)
- Lutz-W Weber
- Institute of Toxicology, GSF-National Research Center for Environment and Health, Munich, D-85758 Neuherberg, Germany.
| | | | | |
Collapse
|