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Ullah H, Shi X, Taj A, Cheng L, Yan Q, Sha S, Ahmad, Kang J, Haris M, Ma X, Ma Y. Mycobacterium tuberculosis PE_PGRS38 Enhances Intracellular Survival of Mycobacteria by Inhibiting TLR4/NF-κB-Dependent Inflammation and Apoptosis of the Host. BIOLOGY 2024; 13:313. [PMID: 38785795 PMCID: PMC11118070 DOI: 10.3390/biology13050313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/20/2024] [Accepted: 04/27/2024] [Indexed: 05/25/2024]
Abstract
Mycobacterium tuberculosis (Mtb) ranks as the most lethal human pathogen, able to fend off repeated attacks by the immune system or medications. PE_PGRS proteins are hallmarks of the pathogenicity of Mtb and contribute to its antigenic diversity, virulence, and persistence during infection. M. smegmatis is a nonpathogenic mycobacterium that naturally lacks PE_PGRS and is used as a model to express Mtb proteins. PE_PGRS has the capability to evade host immune responses and enhance the intracellular survival of M. smegmatis. Despite the intense investigations into PE_PGRS proteins, their role in tuberculosis remains elusive. We engineered the recombinant M. smegmatis strain Ms-PE_PGRS38. The result shows that PE_PGRS38 is expressed in the cell wall of M. smegmatis. PE_PGRS38 contributes to biofilm formation, confers permeability to the cell wall, and shows variable responses to exogenous stresses. PE_PGRS38 downregulated TLR4/NF-κB signaling in RAW264.7 macrophages and lung tissues of infected mice. In addition, PE_PGRS38 decreased NLRP3-dependent IL-1β release and limited pathogen-mediated inflammasome activity during infection. Moreover, PE_PGRS38 inhibited the apoptosis of RAW264.7 cells by downregulating the expression of apoptotic markers including Bax, cytochrome c, caspase-3, and caspase-9. In a nutshell, our findings demonstrate that PE_PGRS38 is a virulence factor for Mtb that enables recombinant M. smegmatis to survive by resisting and evading the host's immune responses during infection.
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Affiliation(s)
- Hayan Ullah
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
- Department of Microbiology, Dalian Medical University, Dalian 116044, China;
| | - Xiaoxia Shi
- Department of Experimental Teaching Center of Public Health, Dalian Medical University, Dalian 116044, China;
| | - Ayaz Taj
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
| | - Lin Cheng
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
| | - Qiulong Yan
- Department of Microbiology, Dalian Medical University, Dalian 116044, China;
| | - Shanshan Sha
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
| | - Ahmad
- Department of Immunology, Dalian Medical University, Dalian 116044, China;
| | - Jian Kang
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
| | - Muhammad Haris
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
| | - Xiaochi Ma
- Pharmaceutical Research Center, The Second Affiliated Hospital, Dalian Medical University, Dalian 116044, China
| | - Yufang Ma
- Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China; (H.U.); (A.T.); (L.C.); (S.S.); (J.K.); (M.H.)
- Department of Microbiology, Dalian Medical University, Dalian 116044, China;
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D'Souza C, Kishore U, Tsolaki AG. The PE-PPE Family of Mycobacterium tuberculosis: Proteins in Disguise. Immunobiology 2023; 228:152321. [PMID: 36805109 DOI: 10.1016/j.imbio.2022.152321] [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: 06/28/2022] [Revised: 12/22/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022]
Abstract
Mycobacterium tuberculosis has thrived in parallel with humans for millennia, and despite our efforts, M. tuberculosis continues to plague us, currently infecting a third of the world's population. The success of M. tuberculosis has recently been attributed, in part, to the PE-PPE family; a unique collection of 168 proteins fundamentally involved in the pathogenesis of M. tuberculosis. The PE-PPE family proteins have been at the forefront of intense research efforts since their discovery in 1998 and whilst our knowledge and understanding has significantly advanced over the last two decades, many important questions remain to be elucidated. This review consolidates and examines the vast body of existing literature regarding the PE-PPE family proteins, with respect to the latest developments in elucidating their evolution, structure, subcellular localisation, function, and immunogenicity. This review also highlights significant inconsistencies and contradictions within the field. Additionally, possible explanations for these knowledge gaps are explored. Lastly, this review poses many important questions, which need to be addressed to complete our understanding of the PE-PPE family, as well as highlighting the challenges associated with studying this enigmatic family of proteins. Further research into the PE-PPE family, together with technological advancements in genomics and proteomics, will undoubtedly improve our understanding of the pathogenesis of M. tuberculosis, as well as identify key targets/candidates for the development of novel drugs, diagnostics, and vaccines.
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Affiliation(s)
- Christopher D'Souza
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge UB8 3PH, United Kingdom
| | - Uday Kishore
- Department of Veterinary Medicine, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Anthony G Tsolaki
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge UB8 3PH, United Kingdom.
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Ehtram A, Shariq M, Ali S, Quadir N, Sheikh JA, Ahmad F, Sharma T, Ehtesham NZ, Hasnain SE. Teleological cooption of Mycobacterium tuberculosis PE/PPE proteins as porins: Role in molecular immigration and emigration. Int J Med Microbiol 2021; 311:151495. [PMID: 33730677 DOI: 10.1016/j.ijmm.2021.151495] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 02/01/2021] [Accepted: 03/05/2021] [Indexed: 01/09/2023] Open
Abstract
Permeation through bacterial cells for exchange or uptake of biomolecules and ions invariably depend upon the existence of pore-forming proteins (porins) in their outer membrane. Mycobacterium tuberculosis (M. tb) harbours one of the most rigid cell envelopes across bacterial genera and is devoid of the classical porins for solute transport across the cell membrane. Though canonical porins are incompatible with the evolution of permeability barrier, porin like activity has been reported from membrane preparations of pathogenic mycobacteria. This suggests a sophisticated transport mechanism that has been elusive until now, along with the protein family responsible for it. Recent evidence suggests that these slow-growing mycobacteria have co-opted some of PE/PPE family proteins as molecular transport channels, in place of porins, to facilitate uptake of nutrients required to thrive in the restrictive host environment. These reports advocate that PE/PPE proteins, due to their structural ability, have a potential role in importing small molecules to the cell's interior. This mechanism unveils how a successful pathogen overcomes its restrictive membrane's transport limitations for selective uptake of nutrients. If extrapolated to have a role in drug transport, these channels could help understand the emergence of drug resistance. Further, as these proteins are associated with the export of virulence factors, they can be exploited as novel drug targets. There remains, however, an interesting question that as the PE/PPE proteins can allow the 'import' of molecules from outside the cell, is the reverse transport also possible across the M. tb membrane. In this review, we have discussed recent evidence supporting PE/PPE's role as a specific transport channel for selective uptake of small molecule nutrients and, as possible molecular export machinery of M. tb. This newly discovered role as transmembrane channels demands further research on this enigmatic family of proteins to comprehend the pathomechanism of this very smart pathogen.
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Affiliation(s)
- Aquib Ehtram
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India
| | - Mohd Shariq
- ICMR-National Institute of Pathology, Ansari Nagar West, New Delhi, India
| | - Sabeeha Ali
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India
| | - Neha Quadir
- ICMR-National Institute of Pathology, Ansari Nagar West, New Delhi, India; Jamia Hamdard- Institute of Molecular Medicine, Jamia Hamdard, Hamdard Nagar, New Delhi, India
| | - Javaid A Sheikh
- Department of Biotechnology, School of Chemical and Life Sciences, Jamia Hamdard, Hamdard Nagar, New Delhi, 110062, India
| | - Faraz Ahmad
- ICMR-National Institute of Pathology, Ansari Nagar West, New Delhi, India
| | - Tarina Sharma
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India; ICMR-National Institute of Pathology, Ansari Nagar West, New Delhi, India
| | - Nasreen Z Ehtesham
- ICMR-National Institute of Pathology, Ansari Nagar West, New Delhi, India.
| | - Seyed E Hasnain
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India; Dr Reddy's Institute of Life Sciences, University of Hyderabad Campus, Hyderabad, India.
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PE_PGRS33, an Important Virulence Factor of Mycobacterium tuberculosis and Potential Target of Host Humoral Immune Response. Cells 2021; 10:cells10010161. [PMID: 33467487 PMCID: PMC7830552 DOI: 10.3390/cells10010161] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/04/2021] [Accepted: 01/12/2021] [Indexed: 01/16/2023] Open
Abstract
PE_PGRS proteins are surface antigens of Mycobacterium tuberculosis (Mtb) and a few other pathogenic mycobacteria. The PE_PGRS33 protein is among the most studied PE_PGRSs. It is known that the PE domain of PE_PGRS33 is required for the protein translocation through the mycobacterial cell wall, where the PGRS domain remains available for interaction with host receptors. Interaction with Toll like receptor 2 (TLR2) promotes secretion of inflammatory chemokines and cytokines, which are key in the immunopathogenesis of tuberculosis (TB). In this review, we briefly address some key challenges in the development of a TB vaccine and attempt to provide a rationale for the development of new vaccines aimed at fostering a humoral response against Mtb. Using PE_PGRS33 as a model for a surface-exposed antigen, we exploit the availability of current structural data using homology modeling to gather insights on the PGRS domain features. Our study suggests that the PGRS domain of PE_PGRS33 exposes four PGII sandwiches on the outer surface, which, we propose, are directly involved through their loops in the interactions with the host receptors and, as such, are promising targets for a vaccination strategy aimed at inducing a humoral response.
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