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Miller J, Murray PJ. Space and time on the membrane: modelling Type VI secretion system dynamics as a state-dependent random walk. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230284. [PMID: 37920566 PMCID: PMC10618060 DOI: 10.1098/rsos.230284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 09/19/2023] [Indexed: 11/04/2023]
Abstract
The type six secretion system (T6SS) is a transmembrane protein complex that mediates bacterial cell killing. The T6SS comprises three main components (transmembrane, baseplate and sheath/tube complexes) that are sequentially assembled in order to enable an attacking cell to transport payloads into neighbouring cells. A T6SS attack disrupts the function of essential cellular components of target cells, typically resulting in their death. While the assembled T6SS adopts a fixed position in the cell membrane of the attacking cell, the location of the firing site varies between firing events. In Serratia marcescens, a post-translational regulatory network regulates the assembly and firing kinetics of the T6SS in a manner that affects the attacking cell's ability to kill target cells. Moreover, when the ability of membrane complexes to reorient is reduced, an attacking cell's competitiveness is also reduced. In this study, we will develop a mathematical model that describes both the spatial motion and assembly/disassembly of a firing T6SS. The model represents the motion of a T6SS on the cell membrane as a state-dependent random walk. Using the model, we will explore how both spatial and temporal effects can combine to give rise to different firing phenotypes. Using parameters inferred from the available literature, we show that variation in estimated diffusion coefficients is sufficient to give rise to either spatially local or global firers.
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Wang Y, Zeng M, Xia L, Valerie Olovo C, Su Z, Zhang Y. Bacterial strategies for immune systems - Role of the type VI secretion system. Int Immunopharmacol 2023; 114:109550. [PMID: 36525796 DOI: 10.1016/j.intimp.2022.109550] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/09/2022] [Accepted: 12/02/2022] [Indexed: 12/15/2022]
Abstract
The process of host infection by bacteria is complicated. Bacterial infections strongly induce the host immune system, which necessitates a robust clearance of the infection. However, bacteria have over time developed strategies that enable their evasion of attacks by the host immune system. One such strategy is the type VI secretion system (T6SS), a special needle-like secretion system that is widespread in Gram-negative bacteria and is responsible for delivering effector proteins into the external bacterial environment or directly into the host cell cytosol. Bacterial T6SS and its secreted effector proteins play an important role in the interaction between bacteria and host immune system. They also serve as antigens that are employed in the development of vaccines for clinical trials as well as future vaccine candidates. This review focuses mainly on aspects of T6SS effectors that impact the strength of the host immune system, including inflammation, autophagy, and apoptosis (silent programmed cell death). The T6SS-based vaccines are also described.
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Affiliation(s)
- Yurou Wang
- Institute for Medical Immunology of Jiangsu University, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212013, China; Department of Biochemistry and Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China
| | - Minmin Zeng
- Department of Biochemistry and Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China
| | - Lin Xia
- Department of Laboratory Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China; International Genome Center, Jiangsu University, Zhenjiang 212013, China
| | - Chinasa Valerie Olovo
- Department of Biochemistry and Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China
| | - Zhaoliang Su
- Institute for Medical Immunology of Jiangsu University, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212013, China; International Genome Center, Jiangsu University, Zhenjiang 212013, China
| | - Ying Zhang
- Institute for Medical Immunology of Jiangsu University, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212013, China; Department of Biochemistry and Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China.
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Prindle JR, Wang Y, Rocha JM, Diepold A, Gahlmann A. Distinct Cytosolic Complexes Containing the Type III Secretion System ATPase Resolved by Three-Dimensional Single-Molecule Tracking in Live Yersinia enterocolitica. Microbiol Spectr 2022; 10:e0174422. [PMID: 36354362 PMCID: PMC9769973 DOI: 10.1128/spectrum.01744-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 10/20/2022] [Indexed: 11/12/2022] Open
Abstract
The membrane-embedded injectisome, the structural component of the virulence-associated type III secretion system (T3SS), is used by Gram-negative bacterial pathogens to inject species-specific effector proteins into eukaryotic host cells. The cytosolic injectisome proteins are required for export of effectors and display both stationary, injectisome-bound populations and freely diffusing cytosolic populations. How the cytosolic injectisome proteins interact with each other in the cytosol and associate with membrane-embedded injectisomes remains unclear. Here, we utilized three-dimensional (3D) single-molecule tracking to resolve distinct cytosolic complexes of injectisome proteins in living Yersinia enterocolitica cells. Tracking of the enhanced yellow fluorescent protein (eYFP)-labeled ATPase YeSctN and its regulator, YeSctL, revealed that these proteins form a cytosolic complex with each other and then further with YeSctQ. YeSctNL and YeSctNLQ complexes can be observed both in wild-type cells and in ΔsctD mutants, which cannot assemble injectisomes. In ΔsctQ mutants, the relative abundance of the YeSctNL complex is considerably increased. These data indicate that distinct cytosolic complexes of injectisome proteins can form prior to injectisome binding, which has important implications for how injectisomes are functionally regulated. IMPORTANCE Injectisomes are membrane-embedded, multiprotein assemblies used by bacterial pathogens to inject virulent effector proteins into eukaryotic host cells. Protein secretion is regulated by cytosolic proteins that dynamically bind and unbind at injectisomes. However, how these regulatory proteins interact with each other remains unknown. By measuring the diffusion rates of single molecules in living cells, we show that cytosolic injectisome proteins form distinct oligomeric complexes with each other prior to binding to injectisomes. We additionally identify the molecular compositions of these complexes and quantify their relative abundances. Quantifying to what extent cytosolic proteins exist as part of larger complexes in living cells has important implications for deciphering the complexity of biomolecular mechanisms. The results and methods reported here are thus relevant for advancing our understanding of how injectisomes and related multiprotein assemblies, such as bacterial flagellar motors, are functionally regulated.
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Affiliation(s)
- Joshua R. Prindle
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Yibo Wang
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Julian M. Rocha
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Andreas Diepold
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Gahlmann
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology & Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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Abstract
Bacterial type IV secretion systems (T4SSs) are a versatile group of nanomachines that can horizontally transfer DNA through conjugation and deliver effector proteins into a wide range of target cells. The components of T4SSs in gram-negative bacteria are organized into several large subassemblies: an inner membrane complex, an outer membrane core complex, and, in some species, an extracellular pilus. Cryo-electron tomography has been used to define the structures of T4SSs in intact bacteria, and high-resolution structural models are now available for isolated core complexes from conjugation systems, the Xanthomonas citri T4SS, the Helicobacter pylori Cag T4SS, and the Legionella pneumophila Dot/Icm T4SS. In this review, we compare the molecular architectures of these T4SSs, focusing especially on the structures of core complexes. We discuss structural features that are shared by multiple T4SSs as well as evolutionary strategies used for T4SS diversification. Finally, we discuss how structural variations among T4SSs may confer specialized functional properties.
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Affiliation(s)
- Michael J. Sheedlo
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Melanie D. Ohi
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America
| | - D. Borden Lacy
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Timothy L. Cover
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
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Tocheva EI. A picture is worth a thousand words: Direct in vivo visualization of the bacterial chromosome segregation protein, PopZ. J Mol Biol 2022; 434:167521. [PMID: 35245499 DOI: 10.1016/j.jmb.2022.167521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Elitza I Tocheva
- Department of Microbiology and Immunology, Life Sciences Institute, 2350 Health Sciences Mall, The University of British Columbia, Canada.
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Emerging technologies and infection models in cellular microbiology. Nat Commun 2021; 12:6764. [PMID: 34799563 PMCID: PMC8604907 DOI: 10.1038/s41467-021-26641-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 10/18/2021] [Indexed: 01/09/2023] Open
Abstract
The field of cellular microbiology, rooted in the co-evolution of microbes and their hosts, studies intracellular pathogens and their manipulation of host cell machinery. In this review, we highlight emerging technologies and infection models that recently promoted opportunities in cellular microbiology. We overview the explosion of microscopy techniques and how they reveal unprecedented detail at the host-pathogen interface. We discuss the incorporation of robotics and artificial intelligence to image-based screening modalities, biochemical mapping approaches, as well as dual RNA-sequencing techniques. Finally, we describe chips, organoids and animal models used to dissect biophysical and in vivo aspects of the infection process. As our knowledge of the infected cell improves, cellular microbiology holds great promise for development of anti-infective strategies with translational applications in human health.
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In Situ Visualization of the pKM101-Encoded Type IV Secretion System Reveals a Highly Symmetric ATPase Energy Center. mBio 2021; 12:e0246521. [PMID: 34634937 PMCID: PMC8510550 DOI: 10.1128/mbio.02465-21] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Bacterial conjugation systems are members of the type IV secretion system (T4SS) superfamily. T4SSs can be classified as “minimized” or “expanded” based on whether they are composed of a core set of signature subunits or additional system-specific components. Prototypical minimized systems mediating Agrobacterium tumefaciens transfer DNA (T-DNA) and pKM101 and R388 plasmid transfer are built from subunits generically named VirB1 to VirB11 and VirD4. We visualized the pKM101-encoded T4SS in its native cellular context by in situ cryo-electron tomography (CryoET). The T4SSpKM101 is composed of an outer membrane core complex (OMCC) connected by a thin stalk to an inner membrane complex (IMC). The OMCC exhibits 14-fold symmetry and resembles that of the T4SSR388 analyzed previously by single-particle electron microscopy. The IMC is highly symmetrical and exhibits 6-fold symmetry. It is dominated by a hexameric collar in the periplasm and a cytoplasmic complex composed of a hexamer of dimers of the VirB4-like TraB ATPase. The IMC closely resembles equivalent regions of three expanded T4SSs previously visualized by in situ CryoET but differs strikingly from the IMC of the purified T4SSR388, whose cytoplasmic complex instead presents as two side-by-side VirB4 hexamers. Analyses of mutant machines lacking each of the three ATPases required for T4SSpKM101 function supplied evidence that TraBB4 as well as VirB11-like TraG contribute to distinct stages of machine assembly. We propose that the VirB4-like ATPases, configured as hexamers of dimers at the T4SS entrance, orchestrate IMC assembly and recruitment of the spatially dynamic VirB11 and VirD4 ATPases to activate the T4SS for substrate transfer.
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Basanta B, Chowdhury S, Lander GC, Grotjahn DA. A guided approach for subtomogram averaging of challenging macromolecular assemblies. J Struct Biol X 2020; 4:100041. [PMID: 33319208 PMCID: PMC7724198 DOI: 10.1016/j.yjsbx.2020.100041] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 10/13/2020] [Accepted: 11/18/2020] [Indexed: 11/20/2022] Open
Affiliation(s)
- Benjamin Basanta
- Department of Integrative Structural and Computational Biology, Scripps Research, HZ 175, 10550 N Torrey Pines Rd., La Jolla, CA 92037, United States
| | - Saikat Chowdhury
- Department of Biochemistry and Cell Biology, 144 Center for Molecular Medicine, Stony Brook University, Stony Brook, NY 11794, United States
| | - Gabriel C. Lander
- Department of Integrative Structural and Computational Biology, Scripps Research, HZ 175, 10550 N Torrey Pines Rd., La Jolla, CA 92037, United States
| | - Danielle A. Grotjahn
- Department of Integrative Structural and Computational Biology, Scripps Research, HZ 175, 10550 N Torrey Pines Rd., La Jolla, CA 92037, United States
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Bleves S, Galán JE, Llosa M. Bacterial injection machines: Evolutionary diverse but functionally convergent. Cell Microbiol 2020; 22:e13157. [PMID: 31891220 PMCID: PMC7138736 DOI: 10.1111/cmi.13157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 12/19/2019] [Indexed: 12/23/2022]
Abstract
Many human pathogens use Type III, Type IV, and Type VI secretion systems to deliver effectors into their target cells. The contribution of these secretion systems to microbial virulence was the main focus of a workshop organised by the International University of Andalusia in Spain. The meeting addressed structure-function, substrate recruitment, and translocation processes, which differ widely on the different secretion machineries, as well as the nature of the translocated effectors and their roles in subverting the host cell. An excellent panel of worldwide speakers presented the state of the art of the field, highlighting the involvement of bacterial secretion in human disease and discussing mechanistic aspects of bacterial pathogenicity, which can provide the bases for the development of novel antivirulence strategies.
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Affiliation(s)
- Sophie Bleves
- LISM (Laboratoire d’Ingénierie des Systèmes Macromoléculaires-UMR7255), IMM (Institut de Microbiologie de la Méditerranée), Aix-Marseille Univ and CNRS, Marseille, France
| | - Jorge E. Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, USA
| | - Matxalen Llosa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC-SODERCAN, Santander, Spain
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Abstract
The translocation of proteins across membranes is a fundamental cellular function. Bacteria have evolved a striking array of pathways for delivering proteins into or across cytoplasmic membranes and, when present, outer membranes. Translocated proteins can form part of the membrane landscape, reside in the periplasmic space situated between the inner and outer membranes of Gram-negative bacteria, deposit on the cell surface, or be released to the extracellular milieu or injected directly into target cells. One protein translocation system, the general secretory pathway, is conserved in all domains of life. A second, the twin-arginine translocation pathway, is also phylogenetically distributed among most bacteria and plant chloroplasts. While all cell types have evolved additional systems dedicated to the translocation of protein cargoes, the number of such systems in bacteria is now known to exceed nine. These dedicated protein translocation systems, which include the types 1 through 9 secretion systems (T1SSs-T9SSs), the chaperone-usher pathway, and type IV pilus system, are the subject of this review. Most of these systems were originally identified and have been extensively characterized in Gram-negative or diderm (two-membrane) species. It is now known that several of these systems also have been adapted to function in Gram-positive or monoderm (single-membrane) species, and at least one pathway is found only in monoderms. This review briefly summarizes the distinctive mechanistic and structural features of each dedicated pathway, as well as the shared properties, that together account for the broad biological diversity of protein translocation in bacteria.
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Affiliation(s)
- Peter J Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St., Houston, TX, USA.
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