1
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Zhou C, Li Z, Li Y, Li Y, Wang W, Shang W, Liu JP, Wang L, Tong C. TRABD modulates mitochondrial homeostasis and tissue integrity. Cell Rep 2024; 43:114304. [PMID: 38843396 DOI: 10.1016/j.celrep.2024.114304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 03/26/2024] [Accepted: 05/15/2024] [Indexed: 07/02/2024] Open
Abstract
High TRABD expression is associated with tau pathology in patients with Alzheimer's disease; however, the function of TRABD is unknown. Human TRABD encodes a mitochondrial outer-membrane protein. The loss of TRABD resulted in mitochondrial fragmentation, and TRABD overexpression led to mitochondrial clustering and fusion. The C-terminal tail of the TRABD anchored to the mitochondrial outer membrane and the TraB domain could form homocomplexes. Additionally, TRABD forms complexes with MFN2, MIGA2, and PLD6 to facilitate mitochondrial fusion. Flies lacking dTRABD are viable and have normal lifespans. However, aging flies exhibit reduced climbing ability and abnormal mitochondrial morphology in their muscles. The expression of dTRABD is increased in aged flies. dTRABD overexpression leads to neurodegeneration and enhances tau toxicity in fly eyes. The overexpression of dTRABD also increased reactive oxygen species (ROS), ATP production, and protein turnover in the mitochondria. This study suggested that TRABD-induced mitochondrial malfunctions contribute to age-related neurodegeneration.
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Affiliation(s)
- Caixia Zhou
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Zhirong Li
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Yawen Li
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Yaoyao Li
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Wei Wang
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Weina Shang
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jun-Ping Liu
- Institute of Aging Research, Hangzhou Normal University, Hangzhou, Zhejiang 311121, China
| | - Liquan Wang
- Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Chao Tong
- MOE Key Laboratory for Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Gastroenterology of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China; Institute of Aging Research, Hangzhou Normal University, Hangzhou, Zhejiang 311121, China; Institute of Neurological and Psychiatric Disorders, Shenzhen Bay Laboratory, Shenzhen 518132, China.
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2
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Li M, Zheng J, Luo D, Xu K, Sheng R, MacDonald BT, He X, Zhang X. Frizzled receptors facilitate Tiki inhibition of Wnt signaling at the cell surface. EMBO Rep 2023; 24:e55873. [PMID: 36994853 PMCID: PMC10240186 DOI: 10.15252/embr.202255873] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 02/28/2023] [Accepted: 03/17/2023] [Indexed: 03/31/2023] Open
Abstract
The membrane-tethered protease Tiki antagonizes Wnt3a signaling by cleaving and inactivating Wnt3a in Wnt-producing cells. Tiki also functions in Wnt-receiving cells to antagonize Wnt signaling by an unknown mechanism. Here, we demonstrate that Tiki inhibition of Wnt signaling at the cell surface requires Frizzled (FZD) receptors. Tiki associates with the Wnt-FZD complex and cleaves the N-terminus of Wnt3a or Wnt5a, preventing the Wnt-FZD complex from recruiting and activating the coreceptor LRP6 or ROR1/2 without affecting Wnt-FZD complex stability. Intriguingly, we demonstrate that the N-terminus of Wnt3a is required for Wnt3a binding to LRP6 and activating β-catenin signaling, while the N-terminus of Wnt5a is dispensable for recruiting and phosphorylating ROR1/2. Both Tiki enzymatic activity and its association with the Wnt-FZD complex contribute to its inhibitory function on Wnt5a. Our study uncovers the mechanism by which Tiki antagonizes Wnt signaling at the cell surface and reveals a negative role of FZDs in Wnt signaling by acting as Tiki cofactors. Our findings also reveal an unexpected role of the Wnt3a N-terminus in the engagement of the coreceptor LRP6.
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Affiliation(s)
- Mingyi Li
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and the Department of Laboratory Medicine, Sichuan Provincial People's HospitalUniversity of Electronic Science and Technology of ChinaChengduChina
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Jing Zheng
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and the Department of Laboratory Medicine, Sichuan Provincial People's HospitalUniversity of Electronic Science and Technology of ChinaChengduChina
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Dong Luo
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and the Department of Laboratory Medicine, Sichuan Provincial People's HospitalUniversity of Electronic Science and Technology of ChinaChengduChina
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Kai Xu
- Department of Orthopedics, Tongji Hospital, Tongji Medical CollegeHuazhong University of Science and TechnologyWuhanChina
| | - Ren Sheng
- College of Life and Health ScienceNortheastern UniversityShenyangChina
| | | | - Xi He
- Department of Neurology, Harvard Medical School, The F. M. Kirby Neurobiology CenterBoston Children's HospitalBostonMAUSA
| | - Xinjun Zhang
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and the Department of Laboratory Medicine, Sichuan Provincial People's HospitalUniversity of Electronic Science and Technology of ChinaChengduChina
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
- Research Unit for Blindness Prevention of the Chinese Academy of Medical Sciences (2019RU026)Sichuan Academy of Medical Sciences and Sichuan Provincial People's HospitalChengduChina
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3
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Craig SEL, Michalski MN, Williams BO. Got WNTS? Insight into bone health from a WNT perspective. Curr Top Dev Biol 2023; 153:327-346. [PMID: 36967199 DOI: 10.1016/bs.ctdb.2023.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
WNT signaling, essential for many aspects of development, is among the most commonly altered pathways associated with human disease. While initially studied in cancer, dysregulation of WNT signaling has been determined to be essential for skeletal development and the maintenance of bone health throughout life. In this review, we discuss the role of Wnt signaling in bone development and disease with a particular focus on two areas. First, we discuss the roles of WNT signaling pathways in skeletal development, with an emphasis on congenital and idiopathic skeletal syndromes and diseases that are associated with genetic variations in WNT signaling components. Next, we cover a topic that has long been an interest of our laboratory, how high and low levels of WNT signaling affects the establishment and maintenance of healthy bone mass. We conclude with a discussion of the status of WNT-based therapeutics in the treatment of skeletal disease.
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Affiliation(s)
- Sonya E L Craig
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI, United States
| | - Megan N Michalski
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI, United States
| | - Bart O Williams
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI, United States.
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4
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Sterling AJ, Snelling WJ, Naughton PJ, Ternan NG, Dooley JSG. Competent but complex communication: The phenomena of pheromone-responsive plasmids. PLoS Pathog 2020; 16:e1008310. [PMID: 32240270 PMCID: PMC7117660 DOI: 10.1371/journal.ppat.1008310] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Enterococci are robust gram-positive bacteria that are found in a variety of surroundings and that cause a significant number of healthcare-associated infections. The genus possesses a high-efficiency pheromone-responsive plasmid (PRP) transfer system for genetic exchange that allows antimicrobial-resistance determinants to spread within bacterial populations. The pCF10 plasmid system is the best characterised, and although other PRP systems are structurally similar, they lack exact functional homologues of pCF10-encoded genes. In this review, we provide an overview of the enterococcal PRP systems, incorporating functional details for the less-well-defined systems. We catalogue the virulence-associated elements of the PRPs that have been identified to date, and we argue that this reinforces the requirement for elucidation of the less studied systems.
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Affiliation(s)
- Amy J. Sterling
- Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, Londonderry, Northern Ireland
- * E-mail:
| | - William J. Snelling
- Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, Londonderry, Northern Ireland
| | - Patrick J. Naughton
- Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, Londonderry, Northern Ireland
| | - Nigel G. Ternan
- Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, Londonderry, Northern Ireland
| | - James S. G. Dooley
- Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, Londonderry, Northern Ireland
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5
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Jang SY, Hwang J, Kim BS, Lee EY, Oh BH, Kim MH. Structural basis of inactivation of Ras and Rap1 small GTPases by Ras/Rap1-specific endopeptidase from the sepsis-causing pathogen Vibrio vulnificus. J Biol Chem 2018; 293:18110-18122. [PMID: 30282804 PMCID: PMC6254334 DOI: 10.1074/jbc.ra118.004857] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 09/25/2018] [Indexed: 12/15/2022] Open
Abstract
Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are secreted by Gram-negative bacteria and function as primary virulence-promoting macromolecules that deliver multiple cytopathic and cytotoxic effector domains into the host cytoplasm. Among these effectors, Ras/Rap1-specific endopeptidase (RRSP) catalyzes the sequence-specific cleavage of the Switch I region of the cellular substrates Ras and Rap1 that are crucial for host innate immune defenses during infection. To dissect the molecular basis underpinning RRSP-mediated substrate inactivation, we determined the crystal structure of an RRSP from the sepsis-causing bacterial pathogen Vibrio vulnificus (VvRRSP). Structural and biochemical analyses revealed that VvRRSP is a metal-independent TIKI family endopeptidase composed of an N-terminal membrane-localization and substrate-recruitment domain (N lobe) connected via an inter-lobe linker to the C-terminal active site-coordinating core β-sheet-containing domain (C lobe). Structure-based mutagenesis identified the 2His/2Glu catalytic residues in the core catalytic domain that are shared with other TIKI family enzymes and that are essential for Ras processing. In vitro KRas cleavage assays disclosed that deleting the N lobe in VvRRSP causes complete loss of enzymatic activity. Endogenous Ras cleavage assays combined with confocal microscopy analysis of HEK293T cells indicated that the N lobe functions both in membrane localization via the first α-helix and in substrate assimilation by altering the functional conformation of the C lobe to facilitate recruitment of cellular substrates. Collectively, these results indicate that RRSP is a critical virulence factor that robustly inactivates Ras and Rap1 and augments the pathogenicity of invading bacteria via the combined effects of its N and C lobes.
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Affiliation(s)
- Song Yee Jang
- From the Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141,; the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, and
| | - Jungwon Hwang
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, and.
| | - Byoung Sik Kim
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, and; the Department of Food Science and Engineering, Ewha Womans University, Seoul 03760, Korea
| | - Eun-Young Lee
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, and
| | - Byung-Ha Oh
- From the Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141,.
| | - Myung Hee Kim
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, and.
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6
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Biancucci M, Minasov G, Banerjee A, Herrera A, Woida PJ, Kieffer MB, Bindu L, Abreu-Blanco M, Anderson WF, Gaponenko V, Stephen AG, Holderfield M, Satchell KJF. The bacterial Ras/Rap1 site-specific endopeptidase RRSP cleaves Ras through an atypical mechanism to disrupt Ras-ERK signaling. Sci Signal 2018; 11:eaat8335. [PMID: 30279169 PMCID: PMC6309442 DOI: 10.1126/scisignal.aat8335] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Ras-extracellular signal-regulated kinase pathway is critical for controlling cell proliferation, and its aberrant activation drives the growth of various cancers. Because many pathogens produce toxins that inhibit Ras activity, efforts to develop effective Ras inhibitors to treat cancer could be informed by studies of Ras inhibition by pathogens. Vibrio vulnificus causes fatal infections in a manner that depends on multifunctional autoprocessing repeats-in-toxin, a toxin that releases bacterial effector domains into host cells. One such domain is the Ras/Rap1-specific endopeptidase (RRSP), which site-specifically cleaves the Switch I domain of the small GTPases Ras and Rap1. We solved the crystal structure of RRSP and found that its backbone shares a structural fold with the EreA/ChaN-like superfamily of enzymes. Unlike other proteases in this family, RRSP is not a metalloprotease. Through nuclear magnetic resonance analysis and nucleotide exchange assays, we determined that the processing of KRAS by RRSP did not release any fragments or cause KRAS to dissociate from its bound nucleotide but instead only locally affected its structure. However, this structural alteration of KRAS was sufficient to disable guanine nucleotide exchange factor-mediated nucleotide exchange and prevent KRAS from binding to RAF. Thus, RRSP is a bacterial effector that represents a previously unrecognized class of protease that disconnects Ras from its signaling network while inducing limited structural disturbance in its target.
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Affiliation(s)
- Marco Biancucci
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - George Minasov
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Avik Banerjee
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Alfa Herrera
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Patrick J Woida
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Matthew B Kieffer
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Lakshman Bindu
- National Cancer Institute-RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21702, USA
| | - Maria Abreu-Blanco
- National Cancer Institute-RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21702, USA
| | - Wayne F Anderson
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Vadim Gaponenko
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Andrew G Stephen
- National Cancer Institute-RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21702, USA
| | - Matthew Holderfield
- National Cancer Institute-RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21702, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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7
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Zhao Y, Ren J, Lu W, Harlos K, Jones EY. Structure of the Wnt signaling enhancer LYPD6 and its interactions with the Wnt coreceptor LRP6. FEBS Lett 2018; 592:3152-3162. [PMID: 30069874 DOI: 10.1002/1873-3468.13212] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 07/12/2018] [Accepted: 07/27/2018] [Indexed: 01/10/2023]
Abstract
Ly6/urokinase-type plasminogen activator receptor (uPAR) (LU) domain containing 6 (LYPD6) is a Wnt signaling enhancer that promotes phosphorylation of the Wnt coreceptor low density lipoprotein receptor-related protein 6 (LRP6). It also binds the nicotinic acetylcholine receptor (nAChR). We report here the 1.25 Å resolution structure of the LYPD6 extracellular LU domain and map its interaction with LRP6 by mutagenesis and surface plasmon resonance. The LYPD6LU structure reveals a 'trifingered protein domain' fold with the middle fingertip bearing an 'NxI' motif, a tripeptide motif associated with LRP5/6 binding by Wnt inhibitors. Of the Ly6 protein family members, only LYPD6 has an NxI motif. Since mutations in the LYPD6 NxI motif abolish or severely reduce interaction with LRP6, our results indicate its key role in the interaction of LYPD6 with LRP6.
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Affiliation(s)
- Yuguang Zhao
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, UK
| | - Jingshan Ren
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, UK
| | - Weixian Lu
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, UK
| | - Karl Harlos
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, UK
| | - Edith Yvonne Jones
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, UK
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8
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Yan J, Xia Y, Yang M, Zou J, Chen Y, Zhang D, Ma L. Quantitative Proteomics Analysis of Membrane Proteins in Enterococcus faecalis With Low-Level Linezolid-Resistance. Front Microbiol 2018; 9:1698. [PMID: 30100900 PMCID: PMC6072972 DOI: 10.3389/fmicb.2018.01698] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 07/09/2018] [Indexed: 11/26/2022] Open
Abstract
Despite increasing reports of low-level linezolid-resistant enterococci worldwide, the mechanism of this resistance remains poorly understood. Previous transcriptome studies of low-level linezolid-resistant Enterococcus faecalis isolates have demonstrated a number of significantly up-regulated genes potentially involved in mediation of drug resistance. However, whether the transcriptome faithfully reflects the proteome remains unknown. In this study, we performed quantitative proteomics analysis of membrane proteins in an E. faecalis isolate (P10748) with low-level linezolid-resistance in comparison with two linezolid-susceptible strains 3138 and ATCC 29212, all of which have been previously investigated by whole transcriptome analysis. A total of 8,197 peptides associated with 1,170 proteins were identified in all three isolates with false discovery rate (FDR) at 1% and P < 0.05. There were 14 significantly up-regulated and 6 significantly down-regulated proteins in strain P10748 compared to strains 3138 and ATCC 29212, which were in general positively correlated with transcription levels revealed in previous transcriptome studies. Our analysis suggests that the low-level linezolid-resistance in E. faecalis is conferred primarily by the ATP-binding cassette protein OptrA through ribosomal protection and, possibly, also by the enterococcal surface protein (Esp) and other proteins through biofilm formation. The genetic transfer of optrA is potentially regulated by the surface exclusion protein Sea1, conjugal transfer protein TraB, replication protein RepA and XRE family transcription regulator protein. This report represents the first investigation of the mechanisms of linezolid-resistance in E. faecalis by a quantitative proteomics approach.
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Affiliation(s)
- Jia Yan
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yun Xia
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Mi Yang
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jiaqi Zou
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yingzhu Chen
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Dawei Zhang
- Department of Clinical Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Liang Ma
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, United States
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9
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Driehuis E, Clevers H. WNT signalling events near the cell membrane and their pharmacological targeting for the treatment of cancer. Br J Pharmacol 2017; 174:4547-4563. [PMID: 28244067 PMCID: PMC5727251 DOI: 10.1111/bph.13758] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 02/16/2017] [Accepted: 02/18/2017] [Indexed: 12/16/2022] Open
Abstract
WNT signalling is an essential signalling pathway for all multicellular animals. Although first described more than 30 years ago, new components and regulators of the pathway are still being discovered. Considering its importance in both embryonic development and adult homeostasis, it is not surprising that this pathway is often deregulated in human diseases such as cancer. Recently, it became clear that in addition to cytoplasmic components such as β-catenin, other, membrane-bound or extracellular, components of the WNT pathway are also altered in cancer. This review gives an overview of the recent discoveries on WNT signalling events near the cell membrane. Furthermore, membrane-associated components of the WNT pathway, which are more accessible for therapeutic intervention, as well therapeutic approaches that already target those components will be discussed. In this way, we hope to stimulate the development of effective anti-cancer therapies that target this fascinating pathway. LINKED ARTICLES This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.
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Affiliation(s)
- Else Driehuis
- Hubrecht InstituteRoyal Netherlands Academy of Arts and Sciences (KNAW)UtrechtThe Netherlands
- University medical center (UMC)UtrechtThe Netherlands
| | - Hans Clevers
- Hubrecht InstituteRoyal Netherlands Academy of Arts and Sciences (KNAW)UtrechtThe Netherlands
- University medical center (UMC)UtrechtThe Netherlands
- Princess Maxime Center (PMC)UtrechtThe Netherlands
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10
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Tortelote GG, Reis RR, de Almeida Mendes F, Abreu JG. Complexity of the Wnt/β‑catenin pathway: Searching for an activation model. Cell Signal 2017; 40:30-43. [PMID: 28844868 DOI: 10.1016/j.cellsig.2017.08.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 08/08/2017] [Accepted: 08/23/2017] [Indexed: 12/13/2022]
Abstract
Wnt signaling refers to a conserved signaling pathway, widely studied due to its roles in cellular communication, cell fate decisions, development and cancer. However, the exact mechanism underlying inhibition of the GSK phosphorylation towards β-catenin and activation of the pathway after biding of Wnt ligand to its cognate receptors at the plasma membrane remains unclear. Wnt target genes are widely spread over several animal phyla. They participate in a plethora of functions during the development of an organism, from axial specification, gastrulation and organogenesis all the way to regeneration and repair in adults. Temporal and spatial oncogenetic re-activation of Wnt signaling almost certainly leads to cancer. Wnt signaling components have been extensively studied as possible targets in anti-cancer therapies. In this review we will discuss one of the most intriguing questions in this field, that is how β-catenin, a major component in this pathway, escapes the destruction complex, gets stabilized in the cytosol and it is translocated to the nucleus where it acts as a co-transcription factor. Four major models have evolved during the past 20years. We dissected each of them along with current views and future perspectives on this pathway. This review will focus on the molecular mechanisms by which Wnt proteins modulate β-catenin cytoplasmic levels and the relevance of this pathway for the development and cancer.
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Affiliation(s)
- Giovane G Tortelote
- Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
| | - Renata R Reis
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Fabio de Almeida Mendes
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jose Garcia Abreu
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
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11
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Nishimura MT, Anderson RG, Cherkis KA, Law TF, Liu QL, Machius M, Nimchuk ZL, Yang L, Chung EH, El Kasmi F, Hyunh M, Osborne Nishimura E, Sondek JE, Dangl JL. TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis. Proc Natl Acad Sci U S A 2017; 114:E2053-E2062. [PMID: 28137883 PMCID: PMC5347586 DOI: 10.1073/pnas.1620973114] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Detection of pathogens by plants is mediated by intracellular nucleotide-binding site leucine-rich repeat (NLR) receptor proteins. NLR proteins are defined by their stereotypical multidomain structure: an N-terminal Toll-interleukin receptor (TIR) or coiled-coil (CC) domain, a central nucleotide-binding (NB) domain, and a C-terminal leucine-rich repeat (LRR). The plant innate immune system contains a limited NLR repertoire that functions to recognize all potential pathogens. We isolated Response to the bacterial type III effector protein HopBA1 (RBA1), a gene that encodes a TIR-only protein lacking all other canonical NLR domains. RBA1 is sufficient to trigger cell death in response to HopBA1. We generated a crystal structure for HopBA1 and found that it has similarity to a class of proteins that includes esterases, the heme-binding protein ChaN, and an uncharacterized domain of Pasteurella multocida toxin. Self-association, coimmunoprecipitation with HopBA1, and function of RBA1 require two previously identified TIR-TIR dimerization interfaces. Although previously described as distinct in other TIR proteins, in RBA1 neither of these interfaces is sufficient when the other is disrupted. These data suggest that oligomerization of RBA1 is required for function. Our identification of RBA1 demonstrates that "truncated" NLRs can function as pathogen sensors, expanding our understanding of both receptor architecture and the mechanism of activation in the plant immune system.
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Affiliation(s)
- Marc T Nishimura
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599;
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599
| | - Ryan G Anderson
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Karen A Cherkis
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Terry F Law
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599
| | - Qingli L Liu
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Mischa Machius
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599
| | - Zachary L Nimchuk
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Li Yang
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Eui-Hwan Chung
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599
| | - Farid El Kasmi
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Michael Hyunh
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Erin Osborne Nishimura
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - John E Sondek
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Jeffery L Dangl
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599;
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599
- Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, NC 27599
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599
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12
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Enterococcal Sex Pheromones: Evolutionary Pathways to Complex, Two-Signal Systems. J Bacteriol 2016; 198:1556-1562. [PMID: 27021562 DOI: 10.1128/jb.00128-16] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Gram-positive bacteria carry out intercellular communication using secreted peptides. Important examples of this type of communication are the enterococcal sex pheromone systems, in which the transfer of conjugative plasmids is controlled by intercellular signaling among populations of donors and recipients. This review focuses on the pheromone response system of the conjugative plasmid pCF10. The peptide pheromones regulating pCF10 transfer act by modulating the ability of the PrgX transcription factor to repress the transcription of an operon encoding conjugation functions. Many Gram-positive bacteria regulate important processes, including the production of virulence factors, biofilm formation, sporulation, and genetic exchange using peptide-mediated signaling systems. The key master regulators of these systems comprise the RRNPP (RggRap/NprR/PlcR/PrgX) family of intracellular peptide receptors; these regulators show conserved structures. While many RRNPP systems include a core module of two linked genes encoding the regulatory protein and its cognate signaling peptide, the enterococcal sex pheromone plasmids have evolved to a complex system that also recognizes a second host-encoded signaling peptide. Additional regulatory genes not found in most RRNPP systems also modulate signal production and signal import in the enterococcal pheromone plasmids. This review summarizes several structural studies that cumulatively demonstrate that the ability of three pCF10 regulatory proteins to recognize the same 7-amino-acid pheromone peptide arose by convergent evolution of unrelated proteins from different families. We also focus on the selective pressures and structure/function constraints that have driven the evolution of pCF10 from a simple, single-peptide system resembling current RRNPPs in other bacteria to the current complex inducible plasmid transfer system.
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Zhang X, MacDonald BT, Gao H, Shamashkin M, Coyle AJ, Martinez RV, He X. Characterization of Tiki, a New Family of Wnt-specific Metalloproteases. J Biol Chem 2015; 291:2435-43. [PMID: 26631728 DOI: 10.1074/jbc.m115.677807] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Indexed: 11/06/2022] Open
Abstract
The Wnt family of secreted glycolipoproteins plays pivotal roles in development and human diseases. Tiki family proteins were identified as novel Wnt inhibitors that act by cleaving the Wnt amino-terminal region to inactivate specific Wnt ligands. Tiki represents a new metalloprotease family that is dependent on Mn(2+)/Co(2+) but lacks known metalloprotease motifs. The Tiki extracellular domain shares homology with bacterial TraB/PrgY proteins, known for their roles in the inhibition of mating pheromones. The TIKI/TraB fold is predicted to be distantly related to structures of additional bacterial proteins and may use a core β-sheet within an α+β-fold to coordinate conserved residues for catalysis. In this study, using assays for Wnt3a cleavage and signaling inhibition, we performed mutagenesis analyses of human TIKI2 to examine the structural prediction and identify the active site residues. We also established an in vitro assay for TIKI2 protease activity using FRET peptide substrates derived from the cleavage motifs of Wnt3a and Xenopus wnt8 (Xwnt8). We further identified two pairs of potential disulfide bonds that reside outside the β-sheet catalytic core but likely assist the folding of the TIKI domain. Finally, we systematically analyzed TIKI2 cleavage of the 19 human WNT proteins, of which we identified 10 as potential TIKI2 substrates, revealing the hydrophobic nature of Tiki cleavage sites. Our study provides insights into the Tiki family of proteases and its Wnt substrates.
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Affiliation(s)
- Xinjun Zhang
- From the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115 and
| | - Bryan T MacDonald
- From the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115 and
| | - Huilan Gao
- the Centers for Therapeutic Innovation, Pfizer, Boston, Massachusetts 02115
| | - Michael Shamashkin
- the Centers for Therapeutic Innovation, Pfizer, Boston, Massachusetts 02115
| | - Anthony J Coyle
- the Centers for Therapeutic Innovation, Pfizer, Boston, Massachusetts 02115
| | - Robert V Martinez
- the Centers for Therapeutic Innovation, Pfizer, Boston, Massachusetts 02115
| | - Xi He
- From the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115 and
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Reis AH, Macdonald B, Feistel K, Brito JM, Amado NG, Xu C, Abreu JG, He XI. Expression and evolution of the Tiki1 and Tiki2 genes in vertebrates. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2015; 58:355-362. [PMID: 25354456 DOI: 10.1387/ijdb.140106ja] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Tiki1 is a Wnt protease and antagonist specifically expressed in the Spemann-Mangold Organizer and is required for head formation in Xenopus embryos. Here we report neighbor-joining phylogenetic analysis of vertebrate Tiki genes and their mRNA expression patterns in chick, mouse, and rabbit embryos. Tiki1 and Tiki2 orthologues are highly conserved, and exhibit similar but also different developmental expression patterns among the vertebrate/mammalian species analyzed. The Tiki1 gene is noticeably absent in the rodent lineage, but is present in lagomorphs and all other vertebrate/mammalian species examined. Expression in Hensen's node, the equivalent of the Xenopus Organizer, was observed for Chick Tiki2 and Rabbit Tiki1 and Tiki2. Mouse Tiki2 was detected at low levels at gastrulation and head fold stages, but not in the node. Mouse Tiki2 and chick Tiki1 display similar expression in the dorsal spinal cord. Chick Tiki1 expression was also detected in the surface ectoderm and maxillary bud, while chick Tiki2 was found in the anterior intestinal portal, head mesenchyme and primitive atrium. Our expression analyses provide evidence that Tiki1 and Tiki2 are evolutionarily conserved among vertebrate species and their expression in the Organizer and other regions suggests contributions of these Wnt inhibitors to embryonic patterning, as well as organogenesis. Our analyses further reveal mis-regulation of TIKI1 and TIKI2 in human cancer and diseases.
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Affiliation(s)
- Alice H Reis
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21949-590, Brazil
| | - Bryan Macdonald
- F. M. Kirby Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Kerstin Feistel
- Institute of Zoology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Jose M Brito
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21949-590, Brazil
| | - Nathalia G Amado
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21949-590, Brazil
| | - Chiwei Xu
- F. M. Kirby Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Jose G Abreu
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21949-590, Brazil
| | - X I He
- F. M. Kirby Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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15
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Malinauskas T, Jones EY. Extracellular modulators of Wnt signalling. Curr Opin Struct Biol 2014; 29:77-84. [PMID: 25460271 DOI: 10.1016/j.sbi.2014.10.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 09/26/2014] [Accepted: 10/02/2014] [Indexed: 10/24/2022]
Abstract
Wnt morphogens are secreted signalling proteins that play leading roles in embryogenesis and tissue homeostasis throughout life. Wnt signalling is controlled by multiple mechanisms, including posttranslational modification of Wnts, antagonist binding (to Wnts or their receptors), and regulation of the availability of Wnt receptors. Recent crystallographic, structure-guided biophysical and cell-based studies have advanced our understanding of how Wnt signalling is regulated at the cell surface. Structures include Wnt in complex with the cysteine-rich domain (CRD) of Frizzled, extracellular fragments of Wnt co-receptor LRP6, LRP6-binding antagonists Dickkopf and Sclerostin, antagonists 5T4/WAIF1 and Wnt inhibitory factor 1 (WIF-1), as well as Frizzled-ubiquitin ligases ZNRF3/RNF43 (in isolation and in complexes with Wnt signalling promoters R-spondins and LGR5). We review recent discoveries and remaining questions.
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Affiliation(s)
- Tomas Malinauskas
- Cold Spring Harbor Laboratory, W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, NY 11724, USA
| | - E Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom.
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16
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Antic I, Biancucci M, Satchell KJF. Cytotoxicity of the Vibrio vulnificus MARTX toxin effector DUF5 is linked to the C2A subdomain. Proteins 2014; 82:2643-56. [PMID: 24935440 DOI: 10.1002/prot.24628] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 06/02/2014] [Accepted: 06/11/2014] [Indexed: 12/19/2022]
Abstract
The multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are bacterial protein toxins that serve as delivery platforms for cytotoxic effector domains. The domain of unknown function in position 5 (DUF5) effector domain is present in at least six different species' MARTX toxins and as a hypothetical protein in Photorhabdus spp. Its presence increases the potency of the Vibrio vulnificus MARTX toxin in mouse virulence studies, indicating DUF5 directly contributes to pathogenesis. In this work, DUF5 is shown to be cytotoxic when transiently expressed in HeLa cells. DUF5 localized to the plasma membrane dependent upon its C1 domain and the cells become rounded dependent upon its C2 domain. Both full-length DUF5 and the C2 domain caused growth inhibition when expressed in Saccharomyces cerevisiae. A structural model of DUF5 was generated based on the structure of Pasteurella multocida toxin facilitating localization of the cytotoxic activity to a 186 amino acid subdomain termed C2A. Within this subdomain, an alanine scanning mutagenesis revealed aspartate-3721 and arginine-3841 as residues critical for cytotoxicity. These residues were also essential for HeLa cell intoxication when purified DUF5 fused to anthrax toxin lethal factor was delivered cytosolically. Thermal shift experiments indicated that these conserved residues are important to maintain protein structure, rather than for catalysis. The Aeromonas hydrophila MARTX toxin DUF5(Ah) domain was also cytotoxic, while the weakly conserved C1-C2 domains from P. multocida toxin were not. Overall, this study is the first demonstration that DUF5 as found in MARTX toxins has cytotoxic activity that depends on conserved residues in the C2A subdomain.
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Affiliation(s)
- Irena Antic
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, 60611
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17
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Secretion of bacterial lipoproteins: through the cytoplasmic membrane, the periplasm and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1509-16. [PMID: 24780125 DOI: 10.1016/j.bbamcr.2014.04.022] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/16/2014] [Accepted: 04/18/2014] [Indexed: 11/20/2022]
Abstract
Bacterial lipoproteins are peripherally anchored membrane proteins that play a variety of roles in bacterial physiology and virulence in monoderm (single membrane-enveloped, e.g., gram-positive) and diderm (double membrane-enveloped, e.g., gram-negative) bacteria. After export of prolipoproteins through the cytoplasmic membrane, which occurs predominantly but not exclusively via the general secretory or Sec pathway, the proteins are lipid-modified at the cytoplasmic membrane in a multistep process that involves sequential modification of a cysteine residue and cleavage of the signal peptide by the signal II peptidase Lsp. In both monoderms and diderms, signal peptide processing is preceded by acylation with a diacylglycerol through preprolipoprotein diacylglycerol transferase (Lgt). In diderms but also some monoderms, lipoproteins are further modified with a third acyl chain through lipoprotein N-acyl transferase (Lnt). Fully modified lipoproteins that are destined to be anchored in the inner leaflet of the outer membrane (OM) are selected, transported and inserted by the Lol (lipoprotein outer membrane localization) pathway machinery, which consists of the inner-membrane (IM) ABC transporter-like LolCDE complex, the periplasmic LolA chaperone and the OM LolB lipoprotein receptor. Retention of lipoproteins in the cytoplasmic membrane results from Lol avoidance signals that were originally described as the "+2 rule". Surface localization of lipoproteins in diderms is rare in most bacteria, with the exception of several spirochetal species. Type 2 (T2SS) and type 5 (T5SS) secretion systems are involved in secretion of specific surface lipoproteins of γ-proteobacteria. In the model spirochete Borrelia burgdorferi, surface lipoprotein secretion does not follow established sorting rules, but remains dependent on N-terminal peptide sequences. Secretion through the outer membrane requires maintenance of lipoproteins in a translocation-competent unfolded conformation, likely through interaction with a periplasmic holding chaperone, which delivers the proteins to an outer membrane lipoprotein flippase. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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18
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Abstract
Tiki proteins appear to antagonize Wnt signalling pathway by acting as Wnt proteases, thereby affecting Wnt solubility by its amino-terminal cleavage. Tiki1 protease activity was shown to be metal ion-dependent and was inhibited by chelating agents and thus was tentatively proposed to be a metalloprotease. Nevertheless, Tiki proteins exhibit no detectable sequence similarity to previously described metalloproteases, but instead have been reported as being homologues of TraB proteins (Pfam ID: PF01963), a widely distributed family of unknown function and structure. Here, we show that Tiki proteins are members of a new superfamily of domains contained not just in TraB proteins, but also in erythromycin esterase (Pfam ID: PF05139), DUF399 (domain of unknown function 399; Pfam ID: PF04187) and MARTX toxins that contribute to host invasion and pathogenesis by bacteria. We establish the core fold of this enzymatic domain and its catalytic residues.
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Affiliation(s)
- Luis Sanchez-Pulido
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK
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