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Resko ZJ, Suhi RF, Thota AV, Kroken AR. Evidence for intracellular Pseudomonas aeruginosa. J Bacteriol 2024:e0010924. [PMID: 38597609 DOI: 10.1128/jb.00109-24] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024] Open
Abstract
Pseudomonas aeruginosa is a significant cause of global morbidity and mortality. Although it is often regarded as an extracellular pathogen toward human cells, numerous investigations report its ability to survive and replicate within host cells, and additional studies demonstrate specific mechanisms enabling it to adopt an intracellular lifestyle. This ability of P. aeruginosa remains less well-investigated than that of other intracellular bacteria, although it is currently gaining attention. If intracellular bacteria are not killed after entering host cells, they may instead receive protection from immune recognition and experience reduced exposure to antibiotic therapy, among additional potential advantages shared with other facultative intracellular pathogens. For this review, we compiled studies that observe intracellular P. aeruginosa across strains, cell types, and experimental systems in vitro, as well as contextualize these findings with the few studies that report similar observations in vivo. We also seek to address key findings that drove the perception that P. aeruginosa remains extracellular in order to reconcile what is currently understood about intracellular pathogenesis and highlight open questions regarding its contribution to disease.
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Affiliation(s)
- Zachary J Resko
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Rachel F Suhi
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Adam V Thota
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Abby R Kroken
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
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Kroken AR, Klein KA, Mitchell PS, Nieto V, Jedel EJ, Evans DJ, Fleiszig SMJ. Intracellular replication of Pseudomonas aeruginosa in epithelial cells requires suppression of the caspase-4 inflammasome. mSphere 2023; 8:e0035123. [PMID: 37589460 PMCID: PMC10597407 DOI: 10.1128/msphere.00351-23] [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: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 08/18/2023] Open
Abstract
Pathogenesis of Pseudomonas aeruginosa infections can include bacterial survival inside epithelial cells. Previously, we showed that this involves multiple roles played by the type three secretion system (T3SS), and specifically the effector ExoS. This includes ExoS-dependent inhibition of a lytic host cell response that subsequently enables intracellular replication. Here, we studied the underlying cell death response to intracellular P. aeruginosa, comparing wild-type to T3SS mutants varying in capacity to induce cell death and that localize to different intracellular compartments. Results showed that corneal epithelial cell death induced by intracellular P. aeruginosa lacking the T3SS, which remains in vacuoles, correlated with the activation of nuclear factor-κB as measured by p65 relocalization and tumor necrosis factor alpha transcription and secretion. Deletion of caspase-4 through CRISPR-Cas9 mutagenesis delayed cell death caused by these intracellular T3SS mutants. Caspase-4 deletion also countered more rapid cell death caused by T3SS effector-null mutants still expressing the T3SS apparatus that traffic to the host cell cytoplasm, and in doing so rescued intracellular replication normally dependent on ExoS. While HeLa cells lacked a lytic death response to T3SS mutants, it was found to be enabled by interferon gamma treatment. Together, these results show that epithelial cells can activate the noncanonical inflammasome pathway to limit proliferation of intracellular P. aeruginosa, not fully dependent on bacterially driven vacuole escape. Since ExoS inhibits the lytic response, the data implicate targeting of caspase-4, an intracellular pattern recognition receptor, as another contributor to the role of ExoS in the intracellular lifestyle of P. aeruginosa. IMPORTANCE Pseudomonas aeruginosa can exhibit an intracellular lifestyle within epithelial cells in vivo and in vitro. The type three secretion system (T3SS) effector ExoS contributes via multiple mechanisms, including extending the life of invaded host cells. Here, we aimed to understand the underlying cell death inhibited by ExoS when P. aeruginosa is intracellular. Results showed that intracellular P. aeruginosa lacking T3SS effectors could elicit rapid cell lysis via the noncanonical inflammasome pathway. Caspase-4 contributed to cell lysis even when the intracellular bacteria lacked the entire T33S and were consequently unable to escape vacuoles, representing a naturally occurring subpopulation during wild-type infection. Together, the data show the caspase-4 inflammasome as an epithelial cell defense against intracellular P. aeruginosa, and implicate its targeting as another mechanism by which ExoS preserves the host cell replicative niche.
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Affiliation(s)
- Abby R. Kroken
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, California, USA
| | - Keith A. Klein
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Patrick S. Mitchell
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Vincent Nieto
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, California, USA
| | - Eric J. Jedel
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, California, USA
| | - David J. Evans
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, California, USA
- College of Pharmacy, Touro University California, Vallejo, California, USA
| | - Suzanne M. J. Fleiszig
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, California, USA
- Graduate Groups in Vision Sciences, Microbiology, and Infectious Diseases & Immunity, University of California, Berkeley, California, USA
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Kroken AR, Klein KA, Mitchell PS, Nieto V, Jedel EJ, Evans DJ, Fleiszig SMJ. Intracellular replication of Pseudomonas aeruginosa in epithelial cells requires suppression of the caspase-4 inflammasome. bioRxiv 2023:2023.02.13.528260. [PMID: 36824932 PMCID: PMC9948977 DOI: 10.1101/2023.02.13.528260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Pathogenesis of Pseudomonas aeruginosa infections can include bacterial survival inside epithelial cells. Previously, we showed this involves multiple roles played by the type three-secretion system (T3SS), and specifically the effector ExoS. This includes ExoS-dependent inhibition of a lytic host cell response that subsequently enables intracellular replication. Here, we studied the underlying cell death response to intracellular P. aeruginosa, comparing wild-type to T3SS mutants varying in capacity to induce cell death and that localize to different intracellular compartments. Results showed that corneal epithelial cell death induced by intracellular P. aeruginosa lacking the T3SS, which remains in vacuoles, correlated with activation of NF-κB as measured by p65 relocalization and TNFα transcription and secretion. Deletion of caspase-4 through CRISPR-Cas9 mutagenesis delayed cell death caused by these intracellular T3SS mutants. Caspase-4 deletion also countered more rapid cell death caused by T3SS effector-null mutants still expressing the TSSS apparatus that traffic to the host cell cytoplasm, and in doing so rescued intracellular replication normally dependent on ExoS. While HeLa cells lacked a lytic death response to T3SS mutants, it was found to be enabled by interferon gamma treatment. Together, these results show that epithelial cells can activate the noncanonical inflammasome pathway to limit proliferation of intracellular P. aeruginosa, not fully dependent on bacterially-driven vacuole escape. Since ExoS inhibits the lytic response, the data implicate targeting of caspase-4, an intracellular pattern recognition receptor, as another contributor to the role of ExoS in the intracellular lifestyle of P. aeruginosa.
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Affiliation(s)
- Abby R Kroken
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL USA
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA USA
| | - Keith A Klein
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL USA
| | | | - Vincent Nieto
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA USA
| | - Eric J Jedel
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA USA
| | - David J Evans
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA USA
- College of Pharmacy, Touro University California, Vallejo, CA USA
| | - Suzanne M J Fleiszig
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA USA
- Graduate Groups in Vision Sciences, Microbiology, and Infectious Diseases & Immunity, University of California, Berkeley, CA USA
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Kroken AR, Gajenthra Kumar N, Yahr TL, Smith BE, Nieto V, Horneman H, Evans DJ, Fleiszig SMJ. Exotoxin S secreted by internalized Pseudomonas aeruginosa delays lytic host cell death. PLoS Pathog 2022; 18:e1010306. [PMID: 35130333 PMCID: PMC8853526 DOI: 10.1371/journal.ppat.1010306] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 02/17/2022] [Accepted: 01/25/2022] [Indexed: 12/22/2022] Open
Abstract
The Pseudomonas aeruginosa toxin ExoS, secreted by the type III secretion system (T3SS), supports intracellular persistence via its ADP-ribosyltransferase (ADPr) activity. For epithelial cells, this involves inhibiting vacuole acidification, promoting vacuolar escape, countering autophagy, and niche construction in the cytoplasm and within plasma membrane blebs. Paradoxically, ExoS and other P. aeruginosa T3SS effectors can also have antiphagocytic and cytotoxic activities. Here, we sought to reconcile these apparently contradictory activities of ExoS by studying the relationships between intracellular persistence and host epithelial cell death. Methods involved quantitative imaging and the use of antibiotics that vary in host cell membrane permeability to selectively kill intracellular and extracellular populations after invasion. Results showed that intracellular P. aeruginosa mutants lacking T3SS effector toxins could kill (permeabilize) cells when extracellular bacteria were eliminated. Surprisingly, wild-type strain PAO1 (encoding ExoS, ExoT and ExoY) caused cell death more slowly, the time extended from 5.2 to 9.5 h for corneal epithelial cells and from 10.2 to 13.0 h for HeLa cells. Use of specific mutants/complementation and controls for initial invasion showed that ExoS ADPr activity delayed cell death. Triggering T3SS expression only after bacteria invaded cells using rhamnose-induction in T3SS mutants rescued the ExoS-dependent intracellular phenotype, showing that injected effectors from extracellular bacteria were not required. The ADPr activity of ExoS was further found to support internalization by countering the antiphagocytic activity of both the ExoS and ExoT RhoGAP domains. Together, these results show two additional roles for ExoS ADPr activity in supporting the intracellular lifestyle of P. aeruginosa; suppression of host cell death to preserve a replicative niche and inhibition of T3SS effector antiphagocytic activities to allow invasion. These findings add to the growing body of evidence that ExoS-encoding (invasive) P. aeruginosa strains can be facultative intracellular pathogens, and that intracellularly secreted T3SS effectors contribute to pathogenesis. While the ADPr domain of the T3SS effector ExoS plays multiple roles in the intracellular lifestyle of P. aeruginosa, ExoS can also be cytotoxic and/or antiphagocytic. Here, we show that when P. aeruginosa enters the cytosol of epithelial cells, cell death is triggered independently of T3SS effector toxins, but ExoS ADPr activity delays this to enable continued intracellular survival and replication. Using rhamnose induction to express the T3SS only after invasion restored this ExoS-dependent phenotype, showing that intracellularly secreted effectors can enable intracellular pathogenesis. ExoS ADPr activity also countered antiphagocytic activity of ExoS and ExoT RhoGAP domains. These results show two additional roles for ExoS ADPr activity in promoting internalization of P. aeruginosa and protecting the intracellular niche, continuing to challenge the notions that P. aeruginosa is exclusively an extracellular pathogen, that it needs to inject T3SS effectors across plasma membranes, and that ExoS is necessarily cytotoxic to host cells.
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Affiliation(s)
- Abby R. Kroken
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Naren Gajenthra Kumar
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
| | - Timothy L. Yahr
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, United States of America
| | - Benjamin E. Smith
- Vision Science Program, University of California, Berkeley, Berkeley, California, United States of America
| | - Vincent Nieto
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
| | - Hart Horneman
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
| | - David J. Evans
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
- College of Pharmacy, Touro University California, Vallejo, California, United States of America
| | - Suzanne M. J. Fleiszig
- School of Optometry, University of California, Berkeley, Berkeley, California, United States of America
- Vision Science Program, University of California, Berkeley, Berkeley, California, United States of America
- Graduate Groups in Microbiology, and Infectious Diseases & Immunity, University of California, Berkeley, Berkeley, California, United States of America
- * E-mail:
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Wan SJ, Datta A, Flandrin O, Metruccio MME, Ma S, Nieto V, Kroken AR, Hill RZ, Bautista DM, Evans DJ, Fleiszig SMJ. Nerve-associated transient receptor potential ion channels can contribute to intrinsic resistance to bacterial adhesion in vivo. FASEB J 2021; 35:e21899. [PMID: 34569661 DOI: 10.1096/fj.202100874r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 08/05/2021] [Accepted: 08/18/2021] [Indexed: 12/15/2022]
Abstract
The cornea of the eye differs from other mucosal surfaces in that it lacks a viable bacterial microbiome and by its unusually high density of sensory nerve endings. Here, we explored the role of corneal nerves in preventing bacterial adhesion. Pharmacological and genetic methods were used to inhibit the function of corneal sensory nerves or their associated transient receptor potential cation channels TRPA1 and TRPV1. Impacts on bacterial adhesion, resident immune cells, and epithelial integrity were examined using fluorescent labeling and quantitative confocal imaging. TRPA1/TRPV1 double gene-knockout mice were more susceptible to adhesion of environmental bacteria and to that of deliberately-inoculated Pseudomonas aeruginosa. Supporting the involvement of TRPA1/TRPV1-expressing corneal nerves, P. aeruginosa adhesion was also promoted by treatment with bupivacaine, or ablation of TRPA1/TRPV1-expressing nerves using RTX. Moreover, TRPA1/TRPV1-dependent defense was abolished by enucleation which severs corneal nerves. High-resolution imaging showed normal corneal ultrastructure and surface-labeling by wheat-germ agglutinin for TRPA1/TRPV1 knockout murine corneas, and intact barrier function by absence of fluorescein staining. P. aeruginosa adhering to corneas after perturbation of nerve or TRPA1/TRPV1 function failed to penetrate the surface. Single gene-knockout mice showed roles for both TRPA1 and TRPV1, with TRPA1-/- more susceptible to P. aeruginosa adhesion while TRPV1-/- corneas instead accumulated environmental bacteria. Corneal CD45+/CD11c+ cell responses to P. aeruginosa challenge, previously shown to counter bacterial adhesion, also depended on TRPA1/TRPV1 and sensory nerves. Together, these results demonstrate roles for corneal nerves and TRPA1/TRPV1 in corneal resistance to bacterial adhesion in vivo and suggest that the mechanisms involve resident immune cell populations.
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Affiliation(s)
- Stephanie J Wan
- Vision Science Program, University of California, Berkeley, California, USA
| | - Ananya Datta
- School of Optometry, University of California, Berkeley, California, USA
| | - Orneika Flandrin
- Vision Science Program, University of California, Berkeley, California, USA
| | | | - Sophia Ma
- School of Optometry, University of California, Berkeley, California, USA
| | - Vincent Nieto
- School of Optometry, University of California, Berkeley, California, USA
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, California, USA
| | - Rose Z Hill
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
| | - Diana M Bautista
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
| | - David J Evans
- School of Optometry, University of California, Berkeley, California, USA.,College of Pharmacy, Touro University California, Vallejo, California, USA
| | - Suzanne M J Fleiszig
- Vision Science Program, University of California, Berkeley, California, USA.,School of Optometry, University of California, Berkeley, California, USA.,Graduate Groups in Microbiology and Infectious Diseases & Immunity, University of California, Berkeley, California, USA
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Szczotka-Flynn LB, Shovlin JP, Schnider CM, Caffery BE, Alfonso EC, Carnt NA, Chalmers RL, Collier S, Jacobs DS, Joslin CE, Kroken AR, Lakkis C, Pearlman E, Schein OD, Stapleton F, Tu E, Willcox MDP. American Academy of Optometry Microbial Keratitis Think Tank. Optom Vis Sci 2021; 98:182-198. [PMID: 33771951 PMCID: PMC8075116 DOI: 10.1097/opx.0000000000001664] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [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] [Indexed: 12/29/2022] Open
Abstract
SIGNIFICANCE Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies. PURPOSE The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting. METHODS Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives. RESULTS The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed. CONCLUSIONS The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.
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Affiliation(s)
| | | | | | | | - Eduardo C Alfonso
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida
| | - Nicole A Carnt
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | | | - Sarah Collier
- U.S. Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Deborah S Jacobs
- Massachusetts Eye and Ear, Cornea Service, Harvard Medical School, Boston, Massachusetts
| | - Charlotte E Joslin
- Department of Ophthalmology and Visual Science, College of Medicine, Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, Berkeley, California
| | | | - Eric Pearlman
- Departments of Ophthalmology, and Physiology and Biophysics, University of California, Irvine, Irvine, California
| | - Oliver D Schein
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Fiona Stapleton
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Elmer Tu
- University of Illinois Eye and Ear Infirmary, Chicago, Illinois
| | - Mark D P Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
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Fleiszig SMJ, Kroken AR, Nieto V, Grosser MR, Wan SJ, Metruccio MME, Evans DJ. Contact lens-related corneal infection: Intrinsic resistance and its compromise. Prog Retin Eye Res 2019; 76:100804. [PMID: 31756497 DOI: 10.1016/j.preteyeres.2019.100804] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 11/05/2019] [Accepted: 11/12/2019] [Indexed: 12/20/2022]
Abstract
Contact lenses represent a widely utilized form of vision correction with more than 140 million wearers worldwide. Although generally well-tolerated, contact lenses can cause corneal infection (microbial keratitis), with an approximate annualized incidence ranging from ~2 to ~20 cases per 10,000 wearers, and sometimes resulting in permanent vision loss. Research suggests that the pathogenesis of contact lens-associated microbial keratitis is complex and multifactorial, likely requiring multiple conspiring factors that compromise the intrinsic resistance of a healthy cornea to infection. Here, we outline our perspective of the mechanisms by which contact lens wear sometimes renders the cornea susceptible to infection, focusing primarily on our own research efforts during the past three decades. This has included studies of host factors underlying the constitutive barrier function of the healthy cornea, its response to bacterial challenge when intrinsic resistance is not compromised, pathogen virulence mechanisms, and the effects of contact lens wear that alter the outcome of host-microbe interactions. For almost all of this work, we have utilized the bacterium Pseudomonas aeruginosa because it is the leading cause of lens-related microbial keratitis. While not yet common among corneal isolates, clinical isolates of P. aeruginosa have emerged that are resistant to virtually all currently available antibiotics, leading the United States CDC (Centers for Disease Control) to add P. aeruginosa to its list of most serious threats. Compounding this concern, the development of advanced contact lenses for biosensing and augmented reality, together with the escalating incidence of myopia, could portent an epidemic of vision-threatening corneal infections in the future. Thankfully, technological advances in genomics, proteomics, metabolomics and imaging combined with emerging models of contact lens-associated P. aeruginosa infection hold promise for solving the problem - and possibly life-threatening infections impacting other tissues.
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Affiliation(s)
- Suzanne M J Fleiszig
- School of Optometry, University of California, Berkeley, CA, USA; Graduate Group in Vision Science, University of California, Berkeley, CA, USA; Graduate Groups in Microbiology and Infectious Diseases & Immunity, University of California, Berkeley, CA, USA.
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, CA, USA
| | - Vincent Nieto
- School of Optometry, University of California, Berkeley, CA, USA
| | | | - Stephanie J Wan
- Graduate Group in Vision Science, University of California, Berkeley, CA, USA
| | | | - David J Evans
- School of Optometry, University of California, Berkeley, CA, USA; College of Pharmacy, Touro University California, Vallejo, CA, USA
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Nieto V, Kroken AR, Grosser MR, Smith BE, Metruccio MME, Hagan P, Hallsten ME, Evans DJ, Fleiszig SMJ. Type IV Pili Can Mediate Bacterial Motility within Epithelial Cells. mBio 2019; 10:e02880-18. [PMID: 31431558 PMCID: PMC6703432 DOI: 10.1128/mbio.02880-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 07/31/2019] [Indexed: 02/07/2023] Open
Abstract
Pseudomonas aeruginosa is among bacterial pathogens capable of twitching motility, a form of surface-associated movement dependent on type IV pili (T4P). Previously, we showed that T4P and twitching were required for P. aeruginosa to cause disease in a murine model of corneal infection, to traverse human corneal epithelial multilayers, and to efficiently exit invaded epithelial cells. Here, we used live wide-field fluorescent imaging combined with quantitative image analysis to explore how twitching contributes to epithelial cell egress. Results using time-lapse imaging of cells infected with wild-type PAO1 showed that cytoplasmic bacteria slowly disseminated throughout the cytosol at a median speed of >0.05 μm s-1 while dividing intracellularly. Similar results were obtained with flagellin (fliC) and flagellum assembly (flhA) mutants, thereby excluding swimming, swarming, and sliding as mechanisms. In contrast, pilA mutants (lacking T4P) and pilT mutants (twitching motility defective) appeared stationary and accumulated in expanding aggregates during intracellular division. Transmission electron microscopy confirmed that these mutants were not trapped within membrane-bound cytosolic compartments. For the wild type, dissemination in the cytosol was not prevented by the depolymerization of actin filaments using latrunculin A and/or the disruption of microtubules using nocodazole. Together, these findings illustrate a novel form of intracellular bacterial motility differing from previously described mechanisms in being directly driven by bacterial motility appendages (T4P) and not depending on polymerized host actin or microtubules.IMPORTANCE Host cell invasion can contribute to disease pathogenesis by the opportunistic pathogen Pseudomonas aeruginosa Previously, we showed that the type III secretion system (T3SS) of invasive P. aeruginosa strains modulates cell entry and subsequent escape from vacuolar trafficking to host lysosomes. However, we also showed that mutants lacking either type IV pili (T4P) or T4P-dependent twitching motility (i) were defective in traversing cell multilayers, (ii) caused less pathology in vivo, and (iii) had a reduced capacity to exit invaded cells. Here, we report that after vacuolar escape, intracellular P. aeruginosa can use T4P-dependent twitching motility to disseminate throughout the host cell cytoplasm. We further show that this strategy for intracellular dissemination does not depend on flagellin and resists both host actin and host microtubule disruption. This differs from mechanisms used by previously studied pathogens that utilize either host actin or microtubules for intracellular dissemination independently of microbe motility appendages.
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Affiliation(s)
- Vincent Nieto
- School of Optometry, University of California, Berkeley, California, USA
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, California, USA
| | - Melinda R Grosser
- School of Optometry, University of California, Berkeley, California, USA
| | - Benjamin E Smith
- Vision Science Program, University of California, Berkeley, California, USA
| | | | - Patrick Hagan
- Undergraduate Research Apprentice Program, University of California, Berkeley, California, USA
| | - Mary E Hallsten
- Undergraduate Research Apprentice Program, University of California, Berkeley, California, USA
| | - David J Evans
- School of Optometry, University of California, Berkeley, California, USA
- College of Pharmacy, Touro University California, Vallejo, California, USA
| | - Suzanne M J Fleiszig
- School of Optometry, University of California, Berkeley, California, USA
- Vision Science Program, University of California, Berkeley, California, USA
- Graduate Group in Microbiology, University of California, Berkeley, California, USA
- Graduate Group in Infectious Diseases and Immunity, University of California, Berkeley, California, USA
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Kroken AR, Karalewitz APA, Fu Z, Kim JJP, Barbieri JT. Novel ganglioside-mediated entry of botulinum neurotoxin serotype D into neurons. J Biol Chem 2011; 286:26828-37. [PMID: 21632541 PMCID: PMC3143643 DOI: 10.1074/jbc.m111.254086] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [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: 04/22/2011] [Revised: 05/17/2011] [Indexed: 11/06/2022] Open
Abstract
Botulinum Neurotoxins (BoNTs) are organized into seven serotypes, A-G. Although several BoNT serotypes enter neurons through synaptic vesicle cycling utilizing dual receptors (a ganglioside and a synaptic vesicle-associated protein), the entry pathway of BoNT/D is less well understood. Although BoNT/D entry is ganglioside-dependent, alignment and structural studies show that BoNT/D lacks key residues within a conserved ganglioside binding pocket that are present in BoNT serotypes A, B, E, F, and G, which indicate that BoNT/D-ganglioside interactions may be unique. In this study BoNT/D is shown to have a unique association with ganglioside relative to the other BoNT serotypes, utilizing a ganglioside binding loop (GBL, residues Tyr-1235-Ala-1245) within the receptor binding domain of BoNT/D (HCR/D) via b-series gangliosides, including GT1b, GD1b, and GD2. HCR/D bound gangliosides and entered neurons dependent upon the aromatic ring of Phe-1240 within the GBL. This is the first BoNT-ganglioside interaction that is mediated by a phenylalanine. In contrast, Trp-1238, located near the N terminus of the ganglioside binding loop, was mostly solvent-inaccessible and appeared to contribute to maintaining the loop structure. BoNT/D entry and intoxication were enhanced by membrane depolarization via synaptic vesicle cycling, where HCR/D colocalized with synaptophysin, a synaptic vesicle marker, but immunoprecipitation experiments did not detect direct association with synaptic vesicle protein 2. Thus, BoNT/D utilizes unique associations with gangliosides and synaptic vesicles to enter neurons, which may facilitate new neurotoxin therapies.
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Affiliation(s)
- Abby R. Kroken
- From the Departments of Microbiology and Molecular Genetics and
| | | | - Zhuji Fu
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jung-Ja P. Kim
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Abstract
The botulinum neurotoxins (BoNTs) are the most potent protein toxins for humans. There are seven serotypes of BoNTs (A-G), based on a lack of cross-antiserum neutralization. The BoNT/C and BoNT/D serotypes include mosaic toxins that are organized as D-C and C-D toxins. One BoNT D-C mosaic toxin, BoNT/D-South Africa (BoNT/D-SA), was not fully neutralized by immunization with a vaccine composed of either prototype BoNT/C-Stockholm or BoNT/D-1873. Whereas several BoNT serotypes utilize dual receptors (gangliosides and proteins) to bind to and enter neurons, the basis for BoNT/C and BoNT/D entry into neurons is less well understood. Recent studies solved the crystal structures of the receptor-binding domains of BoNT/C, BoNT/D, and BoNT/D-SA. Comparative structural analysis showed that BoNT/C, BoNT/D and BoNT/D-SA lacked components of the ganglioside-binding pocket that exists within other BoNT serotypes. With the use of structure-based alignments, biochemical analyses, and cell-binding approaches, BoNT/C and BoNT/D-SA have been shown to possess a unique ganglioside-binding domain, the ganglioside-binding loop. Defining how BoNTs enter host cells provides insights towards understanding the evolution and extending the potential therapeutic and immunological values of the BoNT serotypes.
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Affiliation(s)
- Abby R Kroken
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Karalewitz APA, Kroken AR, Fu Z, Baldwin MR, Kim JJP, Barbieri JT. Identification of a unique ganglioside binding loop within botulinum neurotoxins C and D-SA . Biochemistry 2010; 49:8117-26. [PMID: 20731382 PMCID: PMC2939319 DOI: 10.1021/bi100865f] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [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] [Indexed: 11/29/2022]
Abstract
The botulinum neurotoxins (BoNTs) are the most potent protein toxins for humans. There are seven serotypes of BoNTs (A-G) based on a lack of cross antiserum neutralization. BoNTs utilize gangliosides as components of the host receptors for binding and entry into neurons. Members of BoNT/C and BoNT/D serotypes include mosaic toxins that are organized in D/C and C/D toxins. One D/C mosaic toxin, BoNT/D-South Africa (BoNT/D-SA), was not fully neutralized by immunization with BoNT serotype C or D, which stimulated this study. Here the crystal structures of the receptor binding domains of BoNT/C, BoNT/D, and BoNT/D-SA are presented. Biochemical and cell binding studies show that BoNT/C and BoNT/D-SA possess unique mechanisms for ganglioside binding. These studies provide new information about how the BoNTs can enter host cells as well as a basis for understanding the immunological diversity of these neurotoxins.
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Affiliation(s)
- Andrew P-A. Karalewitz
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Abby R. Kroken
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Zhuji Fu
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michael R. Baldwin
- Department of Microbiology and Immunology at the University of Missouri, Columbia, Missouri
| | - Jung-Ja P. Kim
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Joseph T. Barbieri
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
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