1
|
Pham C, Guo S, Han X, Coleman L, Sze CW, Wang H, Liu J, Li C. A pleiotropic role of sialidase in the pathogenicity of Porphyromonas gingivalis. Infect Immun 2024; 92:e0034423. [PMID: 38376159 DOI: 10.1128/iai.00344-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 02/01/2024] [Indexed: 02/21/2024] Open
Abstract
As one of the keystone pathogens of periodontitis, the oral bacterium Porphyromonas gingivalis produces an array of virulence factors, including a recently identified sialidase (PG0352). Our previous report involving loss-of-function studies indicated that PG0352 plays an important role in the pathophysiology of P. gingivalis. However, this report had not been corroborated by gain-of-function studies or substantiated in different P. gingivalis strains. To fill these gaps, herein we first confirm the role of PG0352 in cell surface structures (e.g., capsule) and serum resistance using P. gingivalis W83 strain through genetic complementation and then recapitulate these studies using P. gingivalis ATCC33277 strain. We further investigate the role of PG0352 and its counterpart (PGN1608) in ATCC33277 in cell growth, biofilm formation, neutrophil killing, cell invasion, and P. gingivalis-induced inflammation. Our results indicate that PG0352 and PGN1608 are implicated in P. gingivalis cell surface structures, hydrophobicity, biofilm formation, resistance to complement and neutrophil killing, and host immune responses. Possible molecular mechanisms involved are also discussed. In summary, this report underscores the importance of sialidases in the pathophysiology of P. gingivalis and opens an avenue to elucidate their underlying molecular mechanisms.
Collapse
Affiliation(s)
- Christopher Pham
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Shuaiqi Guo
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, Connecticut, USA
- Microbial Sciences Institute, Yale University, West Haven, Connecticut, USA
| | - Xiao Han
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Laurynn Coleman
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ching Wooen Sze
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Huizhi Wang
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Jun Liu
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, Connecticut, USA
- Microbial Sciences Institute, Yale University, West Haven, Connecticut, USA
| | - Chunhao Li
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, USA
| |
Collapse
|
2
|
Sze CW, Zhang K, Lynch MJ, Iyer R, Crane BR, Schwartz I, Li C. A chemosensory-like histidine kinase is dispensable for chemotaxis in vitro but regulates the virulence of Borrelia burgdorferi through modulating the stability of RpoS. PLoS Pathog 2023; 19:e1011752. [PMID: 38011206 PMCID: PMC10703414 DOI: 10.1371/journal.ppat.1011752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 12/07/2023] [Accepted: 10/14/2023] [Indexed: 11/29/2023] Open
Abstract
As an enzootic pathogen, the Lyme disease bacterium Borrelia burgdorferi possesses multiple copies of chemotaxis proteins, including two chemotaxis histidine kinases (CHK), CheA1 and CheA2. Our previous study showed that CheA2 is a genuine CHK that is required for chemotaxis; however, the role of CheA1 remains mysterious. This report first compares the structural features that differentiate CheA1 and CheA2 and then provides evidence to show that CheA1 is an atypical CHK that controls the virulence of B. burgdorferi through modulating the stability of RpoS, a key transcriptional regulator of the spirochete. First, microscopic analyses using green-fluorescence-protein (GFP) tags reveal that CheA1 has a unique and dynamic cellular localization. Second, loss-of-function studies indicate that CheA1 is not required for chemotaxis in vitro despite sharing a high sequence and structural similarity to its counterparts from other bacteria. Third, mouse infection studies using needle inoculations show that a deletion mutant of CheA1 (cheA1mut) is able to establish systemic infection in immune-deficient mice but fails to do so in immune-competent mice albeit the mutant can survive at the inoculation site for up to 28 days. Tick and mouse infection studies further demonstrate that CheA1 is dispensable for tick colonization and acquisition but essential for tick transmission. Lastly, mechanistic studies combining immunoblotting, protein turnover, mutagenesis, and RNA-seq analyses reveal that depletion of CheA1 affects RpoS stability, leading to reduced expression of several RpoS-regulated virulence factors (i.e., OspC, BBK32, and DbpA), likely due to dysregulated clpX and lon protease expression. Bulk RNA-seq analysis of infected mouse skin tissues further show that cheA1mut fails to elicit mouse tnf-α, il-10, il-1β, and ccl2 expression, four important cytokines for Lyme disease development and B. burgdorferi transmigration. Collectively, these results reveal a unique role and regulatory mechanism of CheA1 in modulating virulence factor expression and add new insights into understanding the regulatory network of B. burgdorferi.
Collapse
Affiliation(s)
- Ching Wooen Sze
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Kai Zhang
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Michael J. Lynch
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States of America
| | - Radha Iyer
- Department of Pathology, Microbiology, and Immunology, New York Medical College, Valhalla, New York, United States of America
| | - Brian R. Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States of America
| | - Ira Schwartz
- Department of Pathology, Microbiology, and Immunology, New York Medical College, Valhalla, New York, United States of America
| | - Chunhao Li
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
| |
Collapse
|
3
|
Clark ND, Pham C, Kurniyati K, Sze CW, Coleman L, Fu Q, Zhang S, Malkowski MG, Li C. Functional and structural analyses reveal that a dual domain sialidase protects bacteria from complement killing through desialylation of complement factors. PLoS Pathog 2023; 19:e1011674. [PMID: 37747935 PMCID: PMC10553830 DOI: 10.1371/journal.ppat.1011674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 10/05/2023] [Accepted: 09/08/2023] [Indexed: 09/27/2023] Open
Abstract
The complement system is the first line of innate immune defense against microbial infections. To survive in humans and cause infections, bacterial pathogens have developed sophisticated mechanisms to subvert the complement-mediated bactericidal activity. There are reports that sialidases, also known as neuraminidases, are implicated in bacterial complement resistance; however, its underlying molecular mechanism remains elusive. Several complement proteins (e.g., C1q, C4, and C5) and regulators (e.g., factor H and C4bp) are modified by various sialoglycans (glycans with terminal sialic acids), which are essential for their functions. This report provides both functional and structural evidence that bacterial sialidases can disarm the complement system via desialylating key complement proteins and regulators. The oral bacterium Porphyromonas gingivalis, a "keystone" pathogen of periodontitis, produces a dual domain sialidase (PG0352). Biochemical analyses reveal that PG0352 can desialylate human serum and complement factors and thus protect bacteria from serum killing. Structural analyses show that PG0352 contains a N-terminal carbohydrate-binding module (CBM) and a C-terminal sialidase domain that exhibits a canonical six-bladed β-propeller sialidase fold with each blade composed of 3-4 antiparallel β-strands. Follow-up functional studies show that PG0352 forms monomers and is active in a broad range of pH. While PG0352 can remove both N-acetylneuraminic acid (Neu5Ac) and N-glycolyl-neuraminic acid (Neu5Gc), it has a higher affinity to Neu5Ac, the most abundant sialic acid in humans. Structural and functional analyses further demonstrate that the CBM binds to carbohydrates and serum glycoproteins. The results shown in this report provide new insights into understanding the role of sialidases in bacterial virulence and open a new avenue to investigate the molecular mechanisms of bacterial complement resistance.
Collapse
Affiliation(s)
- Nicholas D. Clark
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, University of Buffalo, the State University of New York, Buffalo, New York, United States of America
| | - Christopher Pham
- Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Kurni Kurniyati
- Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Ching Wooen Sze
- Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Laurynn Coleman
- Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Qin Fu
- Proteomics Facility, Institute of Biotechnology, Cornell University, Ithaca, New York, United States of America
| | - Sheng Zhang
- Proteomics Facility, Institute of Biotechnology, Cornell University, Ithaca, New York, United States of America
| | - Michael G. Malkowski
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, University of Buffalo, the State University of New York, Buffalo, New York, United States of America
| | - Chunhao Li
- Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia, United States of America
| |
Collapse
|
4
|
Sze CW, Li C. Chemotaxis Coupling Protein CheW 2 Is Not Required for the Chemotaxis but Contributes to the Full Pathogenicity of Borreliella burgdorferi. Infect Immun 2023; 91:e0000823. [PMID: 36939335 PMCID: PMC10112267 DOI: 10.1128/iai.00008-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 02/23/2023] [Indexed: 03/21/2023] Open
Abstract
The bacterial chemotaxis regulatory circuit mainly consists of coupling protein CheW, sensor histidine kinase CheA, and response regulator CheY. Most bacteria, such as Escherichia coli, have a single gene encoding each of these proteins. Interestingly, the Lyme disease pathogen, Borreliella burgdorferi, has multiple chemotaxis proteins, e.g., two CheA, three CheW, and three CheY proteins. The genes encoding these proteins mainly reside in two operons: cheW2-cheA1-cheB2-cheY2 (A-I) and cheA2-cheW3-cheX-cheY3 (A-II). Previous studies demonstrate that all the genes in A-II are essential for the chemotaxis of B. burgdorferi; however, the role of those genes in A-I remains unknown. This study aimed to fill this gap using the CheW2 gene, the first gene in A-I, as a surrogate. We first mapped the transcription start site of A-I upstream of cheW2 and identified a σ70-like promoter (PW2) and two binding sites (BS1 and BS2) of BosR, an unorthodox Fur/Per homolog. We then demonstrated that BosR binds to PW2 via BS1 and BS2 and that deletion of bosR significantly represses the expression of cheW2 and other genes in A-I, implying that BosR is a positive regulator of A-I. Deletion of cheW2 has no impact on the chemotaxis of B. burgdorferi in vitro but abrogates its ability to evade host adaptive immunity, because the mutant can establish systemic infection only in SCID mice and not in immunocompetent BALB/c mice. This report substantiates the previous proposition that A-I is not implicated in chemotaxis; rather, it may function as a signaling transduction pathway to regulate B. burgdorferi virulence gene expression.
Collapse
Affiliation(s)
- Ching Wooen Sze
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Chunhao Li
- Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| |
Collapse
|
5
|
Zheng Z, Sze CW, Keng CT, Al-Haddawi M, Liu M, Tan SY, Kwek HL, Her Z, Chan XY, Barnwal B, Loh E, Chang KTE, Tan TC, Tan YJ, Chen Q. Hepatitis C virus mediated chronic inflammation and tumorigenesis in the humanised immune system and liver mouse model. PLoS One 2017; 12:e0184127. [PMID: 28886065 PMCID: PMC5590885 DOI: 10.1371/journal.pone.0184127] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 08/18/2017] [Indexed: 12/24/2022] Open
Abstract
Hepatitis C is a liver disease caused by infection of the Hepatitis C virus (HCV). Many individuals infected by the virus are unable to resolve the viral infection and develop chronic hepatitis, which can lead to formation of liver cirrhosis and cancer. To understand better how initial HCV infections progress to chronic liver diseases, we characterised the long term pathogenic effects of HCV infections with the use of a humanised mouse model (HIL mice) we have previously established. Although HCV RNA could be detected in infected mice up to 9 weeks post infection, HCV infected mice developed increased incidences of liver fibrosis, granulomatous inflammation and tumour formation in the form of hepatocellular adenomas or hepatocellular carcinomas by 28 weeks post infection compared to uninfected mice. We also demonstrated that chronic liver inflammation in HCV infected mice was mediated by the human immune system, particularly by monocytes/macrophages and T cells which exhibited exhaustion phenotypes. In conclusion, HIL mice can recapitulate some of the clinical symptoms such as chronic inflammation, immune cell exhaustion and tumorigenesis seen in HCV patients. Our findings also suggest that persistence of HCV-associated liver disease appear to require initial infections of HCV and immune responses but not long term HCV viraemia.
Collapse
MESH Headings
- Animals
- Antigens, CD/metabolism
- Antigens, Differentiation, Myelomonocytic/metabolism
- Biomarkers
- Carcinoma, Hepatocellular/etiology
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Cell Transformation, Neoplastic/immunology
- Cytokines/blood
- Disease Models, Animal
- Hepacivirus/immunology
- Hepatitis C, Chronic/complications
- Hepatitis C, Chronic/immunology
- Hepatitis C, Chronic/metabolism
- Hepatitis C, Chronic/virology
- Liver Function Tests
- Liver Neoplasms/etiology
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Macrophages/immunology
- Macrophages/metabolism
- Mice
- Monocytes/immunology
- Monocytes/metabolism
- Serum Albumin/metabolism
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Viremia/immunology
- Viremia/virology
Collapse
Affiliation(s)
- Zhiqiang Zheng
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Ching Wooen Sze
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | - Choong Tat Keng
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | | | - Min Liu
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Sue Yee Tan
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Hwee Ling Kwek
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Zhisheng Her
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Xue Ying Chan
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Bhaskar Barnwal
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Eva Loh
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore
| | - Kenneth Tou En Chang
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore
- Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Thiam Chye Tan
- Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Obstetrics & Gynaecology, KK Women's and Children's Hospital, Singapore, Singapore
| | - Yee-Joo Tan
- Institute of Molecular and Cell Biology, Singapore, Singapore
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
- * E-mail: (Y-JT); (QC)
| | - Qingfeng Chen
- Institute of Molecular and Cell Biology, Singapore, Singapore
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
- Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
- * E-mail: (Y-JT); (QC)
| |
Collapse
|
6
|
Keng CT, Sze CW, Zheng D, Zheng Z, Yong KSM, Tan SQ, Ong JJY, Tan SY, Loh E, Upadya MH, Kuick CH, Hotta H, Lim SG, Tan TC, Chang KTE, Hong W, Chen J, Tan YJ, Chen Q. Characterisation of liver pathogenesis, human immune responses and drug testing in a humanised mouse model of HCV infection. Gut 2016; 65:1744-53. [PMID: 26149491 PMCID: PMC5036242 DOI: 10.1136/gutjnl-2014-307856] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 05/11/2015] [Indexed: 12/13/2022]
Abstract
OBJECTIVE HCV infection affects millions of people worldwide, and many patients develop chronic infection leading to liver cancers. For decades, the lack of a small animal model that can recapitulate HCV infection, its immunopathogenesis and disease progression has impeded the development of an effective vaccine and therapeutics. We aim to provide a humanised mouse model for the understanding of HCV-specific human immune responses and HCV-associated disease pathologies. DESIGN Recently, we have established human liver cells with a matched human immune system in NOD-scid Il2rg(-/-) (NSG) mice (HIL mice). These mice are infected with HCV by intravenous injection, and the pathologies are investigated. RESULTS In this study, we demonstrate that HIL mouse is capable of supporting HCV infection and can present some of the clinical symptoms found in HCV-infected patients including hepatitis, robust virus-specific human immune cell and cytokine responses as well as liver fibrosis and cirrhosis. Similar to results obtained from the analysis of patient samples, the human immune cells, particularly T cells and macrophages, play critical roles during the HCV-associated liver disease development in the HIL mice. Furthermore, our model is demonstrated to be able to reproduce the therapeutic effects of human interferon alpha 2a antiviral treatment. CONCLUSIONS The HIL mouse provides a model for the understanding of HCV-specific human immune responses and HCV-associated disease pathologies. It could also serve as a platform for antifibrosis and immune-modulatory drug testing.
Collapse
Affiliation(s)
- Choong Tat Keng
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Ching Wooen Sze
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Dahai Zheng
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Zhiqiang Zheng
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | | | - Shu Qi Tan
- Department of Obstetrics & Gynaecology, KK Women's and Children's Hospital, Singapore, Singapore
| | | | - Sue Yee Tan
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Eva Loh
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore
| | - Megha Haridas Upadya
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Chik Hong Kuick
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore
| | - Hak Hotta
- Division of Microbiology, Kobe University Graduate School of Medicine, Hyogo, Japan
| | - Seng Gee Lim
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore Department of Gastroenterology and Hepatology, National University Health System, Singapore, Singapore
| | - Thiam Chye Tan
- Department of Obstetrics & Gynaecology, KK Women's and Children's Hospital, Singapore, Singapore Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Kenneth T E Chang
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Wanjin Hong
- Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Jianzhu Chen
- Interdisciplinary Research Group in Infectious Diseases, Singapore-Massachusetts Institute of Technology Alliance for Research and Technology, Singapore, Singapore The Koch Institute for Integrative Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Yee-Joo Tan
- Institute of Molecular and Cell Biology, Singapore, Singapore Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Qingfeng Chen
- Institute of Molecular and Cell Biology, Singapore, Singapore Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore Interdisciplinary Research Group in Infectious Diseases, Singapore-Massachusetts Institute of Technology Alliance for Research and Technology, Singapore, Singapore
| |
Collapse
|
7
|
Aweya JJ, Sze CW, Bayega A, Mohd-Ismail NK, Deng L, Hotta H, Tan YJ. NS5B induces up-regulation of the BH3-only protein, BIK, essential for the hepatitis C virus RNA replication and viral release. Virology 2014; 474:41-51. [PMID: 25463603 PMCID: PMC7127593 DOI: 10.1016/j.virol.2014.10.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 10/24/2014] [Indexed: 12/14/2022]
Abstract
Hepatitis C virus (HCV) induces cytopathic effects in the form of hepatocytes apoptosis thought to be resulted from the interaction between viral proteins and host factors. Using pathway specific PCR array, we identified 9 apoptosis-related genes that are dysregulated during HCV infection, of which the BH3-only pro-apoptotic Bcl-2 family protein, BIK, was consistently up-regulated at the mRNA and protein levels. Depletion of BIK protected host cells from HCV-induced caspase-3/7 activation but not the inhibitory effect of HCV on cell viability. Furthermore, viral RNA replication and release were significantly suppressed in BIK-depleted cells and over-expression of the RNA-dependent RNA polymerase, NS5B, was able to induce BIK expression. Immunofluorescence and co-immunoprecipitation assays showed co-localization and interaction of BIK and NS5B, suggesting that BIK may be interacting with the HCV replication complex through NS5B. These results imply that BIK is essential for HCV replication and that NS5B is able to induce BIK expression.
Collapse
Affiliation(s)
- Jude Juventus Aweya
- Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System (NUHS), National University of Singapore, Singapore
| | - Ching Wooen Sze
- Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System (NUHS), National University of Singapore, Singapore
| | - Anthony Bayega
- Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System (NUHS), National University of Singapore, Singapore; Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A⁎STAR), Singapore 138673, Singapore
| | - Nur Khairiah Mohd-Ismail
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A⁎STAR), Singapore 138673, Singapore
| | - Lin Deng
- Division of Microbiology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan
| | - Hak Hotta
- Division of Microbiology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan
| | - Yee-Joo Tan
- Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System (NUHS), National University of Singapore, Singapore; Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A⁎STAR), Singapore 138673, Singapore.
| |
Collapse
|
8
|
Sze CW, Morado DR, Liu J, Charon NW, Xu H, Li C. Carbon storage regulator A (CsrA(Bb)) is a repressor of Borrelia burgdorferi flagellin protein FlaB. Mol Microbiol 2011; 82:851-64. [PMID: 21999436 DOI: 10.1111/j.1365-2958.2011.07853.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The Lyme disease spirochete Borrelia burgdorferi lacks the transcriptional cascade control of flagellar protein synthesis common to other bacteria. Instead, it relies on a post-transcriptional mechanism to control its flagellar synthesis. The underlying mechanism of this control remains elusive. A recent study reported that the increased level of BB0184 (CsrA(Bb); a homologue of carbon storage regulator A) substantially inhibited the accumulation of FlaB, the major flagellin protein of B. burgdorferi. In this report, we deciphered the regulatory role of CsrA(Bb) on FlaB synthesis and the mechanism involved by analysing two mutants, csrA(Bb)(-) (a deletion mutant of csrA(Bb)) and csrA(Bb)(+) (a mutant conditionally overexpressing csrA(Bb)). We found that FlaB accumulation was significantly inhibited in csrA(Bb)(+) but was substantially increased in csrA(Bb)(-) . In contrast, the levels of other flagellar proteins remained unchanged. Cryo-electron tomography and immuno-fluorescence microscopic analyses revealed that the altered synthesis of CsrA(Bb) in these two mutants specifically affected flagellar filament length. The leader sequence of flaB transcript contains two conserved CsrA-binding sites, with one of these sites overlapping the Shine-Dalgarno sequence. We found that CsrA(Bb) bound to the flaB transcripts via these two binding sites, and this binding inhibited the synthesis of FlaB at the translational level. Taken together, our results indicate that CsrA(Bb) specifically regulates the periplasmic flagellar synthesis by inhibiting translation initiation of the flaB transcript.
Collapse
Affiliation(s)
- Ching Wooen Sze
- Department of Oral Biology, The State University of New York at Buffalo, New York 14214, USA
| | | | | | | | | | | |
Collapse
|