scholarly journals Repair of a Bacterial Small β-Barrel Toxin Pore Depends on Channel Width

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Gisela von Hoven ◽  
Amable J. Rivas ◽  
Claudia Neukirch ◽  
Martina Meyenburg ◽  
Qianqian Qin ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Cellular Responses ◽  
Channel Width ◽  
Target Cells ◽  
Alpha Toxin ◽  
Membrane Repair ◽  
Critical Determinant ◽  
Membrane Pores ◽  
Transmembrane Pores ◽  
Repair Mechanisms

ABSTRACT Membrane repair emerges as an innate defense protecting target cells against bacterial pore-forming toxins. Here, we report the first paradigm of Ca2+-dependent repair following attack by a small β-pore-forming toxin, namely, plasmid-encoded phobalysin of Photobacterium damselae subsp. damselae. In striking contrast, Vibrio cholerae cytolysin, the closest ortholog of phobalysin, subverted repair. Mutational analysis uncovered a role of channel width in toxicity and repair. Thus, the replacement of serine at phobalysin´s presumed channel narrow point with the bulkier tryptophan, the corresponding residue in Vibrio cholerae cytolysin (W318), modulated Ca2+ influx, lysosomal exocytosis, and membrane repair. And yet, replacing tryptophan (W318) with serine in Vibrio cholerae cytolysin enhanced toxicity. The data reveal divergent strategies evolved by two related small β-pore-forming toxins to manipulate target cells: phobalysin leads to fulminant perturbation of ion concentrations, closely followed by Ca2+ influx-dependent membrane repair. In contrast, V. cholerae cytolysin causes insidious perturbations and escapes control by the cellular wounded membrane repair-like response. IMPORTANCE Previous studies demonstrated that large transmembrane pores, such as those formed by perforin or bacterial toxins of the cholesterol-dependent cytolysin family, trigger rapid, Ca2+ influx-dependent repair mechanisms. In contrast, recovery from attack by the small β-pore-forming Staphylococcus aureus alpha-toxin or aerolysin is slow in comparison and does not depend on extracellular Ca2+. To further elucidate the scope of Ca2+ influx-dependent repair and understand its limitations, we compared the cellular responses to phobalysin and V. cholerae cytolysin, two related small β-pore-forming toxins which create membrane pores of slightly different sizes. The data indicate that the channel width of a small β-pore-forming toxin is a critical determinant of both primary toxicity and susceptibility to Ca2+-dependent repair. IMPORTANCE Previous studies demonstrated that large transmembrane pores, such as those formed by perforin or bacterial toxins of the cholesterol-dependent cytolysin family, trigger rapid, Ca2+ influx-dependent repair mechanisms. In contrast, recovery from attack by the small β-pore-forming Staphylococcus aureus alpha-toxin or aerolysin is slow in comparison and does not depend on extracellular Ca2+. To further elucidate the scope of Ca2+ influx-dependent repair and understand its limitations, we compared the cellular responses to phobalysin and V. cholerae cytolysin, two related small β-pore-forming toxins which create membrane pores of slightly different sizes. The data indicate that the channel width of a small β-pore-forming toxin is a critical determinant of both primary toxicity and susceptibility to Ca2+-dependent repair.

scholarly journals Molecular mechanism of pore formation by aerolysin-like proteins

2017 ◽  
Vol 372 (1726) ◽  
pp. 20160209 ◽  
Author(s):  
Marjetka Podobnik ◽  
Matic Kisovec ◽  
Gregor Anderluh
Keyword(s):  
Cell Biology ◽  
Pore Formation ◽  
Target Cells ◽  
Membrane Pores ◽  
Surface Molecules ◽  
Structural Details ◽  
Transmembrane Pores ◽  
Future Drug ◽  
Pore Forming Proteins ◽  
Unique Domain

Aerolysin-like pore-forming proteins are an important family of proteins able to efficiently damage membranes of target cells by forming transmembrane pores. They are characterized by a unique domain organization and mechanism of action that involves extensive conformational rearrangements. Although structures of soluble forms of many different members of this family are well understood, the structures of pores and their mechanism of assembly have been described only recently. The pores are characterized by well-defined β-barrels, which are devoid of any vestibular regions commonly found in other protein pores. Many members of this family are bacterial toxins; therefore, structural details of their transmembrane pores, as well as the mechanism of pore formation, are an important base for future drug design. Stability of pores and other properties, such as specificity for some cell surface molecules, make this family of proteins a useful set of molecular tools for molecular recognition and sensing in cell biology. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

scholarly journals Combined In Vitro and In Vivo Approaches to Propose a Putative Adverse Outcome Pathway for Acute Lung Inflammation Induced by Nanoparticles: A Study on Carbon Dots

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 180
Author(s):  
Maud Weiss ◽  
Jiahui Fan ◽  
Mickaël Claudel ◽  
Luc Lebeau ◽  
Françoise Pons ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Lung Inflammation ◽  
Adverse Outcome ◽  
Cellular Responses ◽  
Target Cells ◽  
Inflammasome Activation ◽  
Adverse Outcome Pathway ◽  
Acute Lung Inflammation

With the growth of nanotechnologies, concerns raised regarding the potential adverse effects of nanoparticles (NPs), especially on the respiratory tract. Adverse outcome pathways (AOP) have become recently the subject of intensive studies in order to get a better understanding of the mechanisms of NP toxicity, and hence hopefully predict the health risks associated with NP exposure. Herein, we propose a putative AOP for the lung toxicity of NPs using emerging nanomaterials called carbon dots (CDs), and in vivo and in vitro experimental approaches. We first investigated the effect of a single administration of CDs on mouse airways. We showed that CDs induce an acute lung inflammation and identified airway macrophages as target cells of CDs. Then, we studied the cellular responses induced by CDs in an in vitro model of macrophages. We observed that CDs are internalized by these cells (molecular initial event) and induce a series of key events, including loss of lysosomal integrity and mitochondrial disruption (organelle responses), as well as oxidative stress, inflammasome activation, inflammatory cytokine upregulation and macrophage death (cellular responses). All these effects triggering lung inflammation as tissular response may lead to acute lung injury.

scholarly journals Plasma membrane integrity in health and disease: significance and therapeutic potential

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Catarina Dias ◽  
Jesper Nylandsted
Keyword(s):  
Plasma Membrane ◽  
Therapeutic Potential ◽  
Calcium Influx ◽  
Membrane Integrity ◽  
Cell Types ◽  
Physical Parameters ◽  
Membrane Repair ◽  
Plasma Membrane Integrity ◽  
Repair Mechanisms ◽  
And Function

AbstractMaintenance of plasma membrane integrity is essential for normal cell viability and function. Thus, robust membrane repair mechanisms have evolved to counteract the eminent threat of a torn plasma membrane. Different repair mechanisms and the bio-physical parameters required for efficient repair are now emerging from different research groups. However, less is known about when these mechanisms come into play. This review focuses on the existence of membrane disruptions and repair mechanisms in both physiological and pathological conditions, and across multiple cell types, albeit to different degrees. Fundamentally, irrespective of the source of membrane disruption, aberrant calcium influx is the common stimulus that activates the membrane repair response. Inadequate repair responses can tip the balance between physiology and pathology, highlighting the significance of plasma membrane integrity. For example, an over-activated repair response can promote cancer invasion, while the inability to efficiently repair membrane can drive neurodegeneration and muscular dystrophies. The interdisciplinary view explored here emphasises the widespread potential of targeting plasma membrane repair mechanisms for therapeutic purposes.

scholarly journals Listeriolysin O: from bazooka to Swiss army knife

2017 ◽  
Vol 372 (1726) ◽  
pp. 20160222 ◽  
Author(s):  
Suzanne E. Osborne ◽  
John H. Brumell
Keyword(s):  
Systemic Disease ◽  
Membrane Damage ◽  
Host Cells ◽  
Listeriolysin O ◽  
Tissue Destruction ◽  
Membrane Repair ◽  
Membrane Pores ◽  
Bacterial Dissemination ◽  
Versatile Tool ◽  
Cell Spread

Listeria monocytogenes ( Lm ) is a Gram-positive facultative intracellular pathogen. Infections in humans can lead to listeriosis, a systemic disease with a high mortality rate. One important mechanism of Lm dissemination involves cell-to-cell spread after bacteria have entered the cytosol of host cells. Listeriolysin O (LLO; encoded by the hly gene) is a virulence factor present in Lm that plays a central role in the cell-to-cell spread process. LLO is a member of the cholesterol-dependent cytolysin (CDC) family of toxins that were initially thought to promote disease largely by inducing cell death and tissue destruction—essentially acting like a ‘bazooka’. This view was supported by structural studies showing CDCs can form large pores in membranes. However, it is now appreciated that LLO has many subtle activities during Lm infection of host cells, and many of these likely do not involve large pores, but rather small membrane perforations. It is also appreciated that membrane repair pathways of host cells play a major role in limiting membrane damage by LLO and other toxins. LLO is now thought to represent a ‘Swiss army knife’, a versatile tool that allows Lm to induce many membrane alterations and cellular responses that promote bacterial dissemination during infection. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

A role for PS integrins in morphological growth and synaptic function at the postembryonic neuromuscular junction of Drosophila

Development ◽  
1999 ◽  
Vol 126 (24) ◽  
pp. 5833-5846 ◽  
Author(s):  
K.J. Beumer ◽  
J. Rohrbough ◽  
A. Prokop ◽  
K. Broadie
Keyword(s):  
Neuromuscular Junction ◽  
Synapse Formation ◽  
Postsynaptic Membrane ◽  
Synaptic Function ◽  
Beta Subunit ◽  
Target Cells ◽  
Type I ◽  
Critical Determinant ◽  
Beta Subunit Gene ◽  
Mutant Phenotypes

A family of three position-specific (PS) integrins are expressed at the Drosophila neuromuscular junction (NMJ): a beta subunit ((betaPS), expressed in both presynaptic and postsynaptic membranes, and two alpha subunits (alphaPS1, alphaPS2), expressed at least in the postsynaptic membrane. PS integrins appear at postembryonic NMJs coincident with the onset of rapid morphological growth and terminal type-specific differentiation, and are restricted to type I synaptic boutons, which mediate fast, excitatory glutamatergic transmission. We show that two distinctive hypomorphic mutant alleles of the beta subunit gene myospheroid (mys(b9) and mys(ts1)), differentially affect betaPS protein expression at the synapse to produce distinctive alterations in NMJ branching, bouton formation, synaptic architecture and the specificity of synapse formation on target cells. The mys(b9) mutation alters betaPS localization to cause a striking reduction in NMJ branching, bouton size/number and the formation of aberrant ‘mini-boutons’, which may represent a developmentally arrested state. The mys(ts1) mutation strongly reduces betaPS expression to cause the opposite phenotype of excessive synaptic sprouting and morphological growth. NMJ function in these mutant conditions is altered in line with the severity of the morphological aberrations. Consistent with these mutant phenotypes, transgenic overexpression of the betaPS protein with a heat-shock construct or tissue-specific GAL4 drivers causes a reduction in synaptic branching and bouton number. We conclude that betaPS integrin at the postembryonic NMJ is a critical determinant of morphological growth and synaptic specificity. These data provide the first genetic evidence for a functional role of integrins at the postembryonic synapse.

scholarly journals Membrane Repair: Mechanisms and Pathophysiology

2015 ◽  
Vol 95 (4) ◽  
pp. 1205-1240 ◽  
Author(s):  
Sandra T. Cooper ◽  
Paul L. McNeil
Keyword(s):  
Molecular Mechanisms ◽  
Eukaryotic Cells ◽  
Membrane Repair ◽  
Membrane Pore ◽  
Rapid Repair ◽  
Repair Mechanisms ◽  
Molecular Machinery ◽  
Repair Pathways ◽  
Different Tissues ◽  
Ischemic Stress

Eukaryotic cells have been confronted throughout their evolution with potentially lethal plasma membrane injuries, including those caused by osmotic stress, by infection from bacterial toxins and parasites, and by mechanical and ischemic stress. The wounded cell can survive if a rapid repair response is mounted that restores boundary integrity. Calcium has been identified as the key trigger to activate an effective membrane repair response that utilizes exocytosis and endocytosis to repair a membrane tear, or remove a membrane pore. We here review what is known about the cellular and molecular mechanisms of membrane repair, with particular emphasis on the relevance of repair as it relates to disease pathologies. Collective evidence reveals membrane repair employs primitive yet robust molecular machinery, such as vesicle fusion and contractile rings, processes evolutionarily honed for simplicity and success. Yet to be fully understood is whether core membrane repair machinery exists in all cells, or whether evolutionary adaptation has resulted in multiple compensatory repair pathways that specialize in different tissues and cells within our body.

scholarly journals Haemolytic actinoporins interact with carbohydrates using their lipid-binding module

2017 ◽  
Vol 372 (1726) ◽  
pp. 20160216 ◽  
Author(s):  
Koji Tanaka ◽  
Jose M. M. Caaveiro ◽  
Koldo Morante ◽  
Kouhei Tsumoto
Keyword(s):  
Protein Interactions ◽  
Pore Formation ◽  
Plasma Membranes ◽  
Lipid Binding ◽  
Target Cells ◽  
Sea Anemones ◽  
Molecular Systems ◽  
Membrane Pores ◽  
Living Organisms ◽  
Lipid Protein Interactions

Pore-forming toxins (PFTs) are proteins endowed with metamorphic properties that enable them to stably fold in water solutions as well as in cellular membranes. PFTs produce lytic pores on the plasma membranes of target cells conducive to lesions, playing key roles in the defensive and offensive molecular systems of living organisms. Actinoporins are a family of potent haemolytic toxins produced by sea anemones vigorously studied as a paradigm of α-helical PFTs, in the context of lipid–protein interactions, and in connection with nanopore technologies. We have recently reported that fragaceatoxin C (FraC), an actinoporin, engages biological membranes with a large adhesive motif allowing the simultaneous attachment of up to four lipid molecules prior to pore formation. Since actinoporins also interact with carbohydrates, we sought to understand the molecular and energetic basis of glycan recognition by FraC. By employing structural and biophysical methodologies, we show that FraC engages glycans with low affinity using its lipid-binding module. Contrary to other PFTs requiring separate domains for glycan and lipid recognition, the small single-domain actinoporins economize resources by achieving dual recognition with a single binding module. This mechanism could enhance the recruitment of actinoporins to the surface of target tissues in their marine environment. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

scholarly journals Signaling beyond Punching Holes: Modulation of Cellular Responses by Vibrio cholerae Cytolysin

Toxins ◽  
2015 ◽  
Vol 7 (8) ◽  
pp. 3344-3358 ◽  
Author(s):  
Barkha Khilwani ◽  
Kausik Chattopadhyay
Keyword(s):  
Vibrio Cholerae ◽  
Cellular Responses

Rapid S-nitrosothiol metabolism by platelets and megakaryocytes

2003 ◽  
Vol 31 (6) ◽  
pp. 1450-1452 ◽  
Author(s):  
C.M. Shah ◽  
I.C. Locke ◽  
H.S. Chowdrey ◽  
M.P. Gordge
Keyword(s):  
Critical Role ◽  
Cellular Responses ◽  
Blocking Agent ◽  
Target Cells ◽  
Pharmacological Effects ◽  
Surface Receptors ◽  
Nitrobenzoic Acid ◽  
Short Time ◽  
Glutamyl Transpeptidase

RSNOs (S-nitrosothiols) regulate platelet and megakaryocyte function, and may act in vivo as a nitric oxide reservoir. There is a discrepancy between the spontaneous rate of NO release from different RSNO compounds and their pharmacological effects, implying that target cells may mediate biological activity either by metabolism of RSNOs or by displaying cell surface receptors. In the present study, we sought evidence for rapid cell-mediated metabolism of RSNOs. Exposure of platelets to GSNO (S-nitrosoglutathione) for as little as 5 s inhibited thrombin-induced platelet aggregation by >95%; however, AlbSNO (S-nitrosoalbumin) was much less effective over these short time periods. Incubation of 1 μM GSNO or AlbSNO with platelets and megakaryocytes resulted in a 25–34% loss of RSNO recoverable from the supernatant (P<0.02) within 30 s. This rapid cell-mediated RSNO decay did not progress further over 5 min, and could not be accounted for by release of free NO. The γ-glutamyl transpeptidase inhibitor acivicin (100 μM) partially decreased GSNO decay, whereas the membrane-impermeable thiol-blocking agent 5,5´-dithiobis-(2-nitrobenzoic acid) (100 μM) completely blocked cell-mediated GSNO decay and partially blocked AlbSNO decay. Our results highlight differences between high- and low-molecular-mass RSNOs with regard to their rapid metabolism/uptake and subsequent cellular responses, and indicate a critical role for extracellular thiols in RSNO metabolism by platelets and megakaryocytes.

scholarly journals Phobalysin, a Small β-Pore-Forming Toxin of Photobacterium damselae subsp. damselae

2015 ◽  
Vol 83 (11) ◽  
pp. 4335-4348 ◽  
Author(s):  
Amable J. Rivas ◽  
Gisela von Hoven ◽  
Claudia Neukirch ◽  
Martina Meyenburg ◽  
Qianqian Qin ◽  
...  
Keyword(s):  
Lactate Dehydrogenase ◽  
Epithelial Cells ◽  
Necrotizing Fasciitis ◽  
Vibrio Cholerae ◽  
Gene Product ◽  
Morphological Changes ◽  
Marine Animals ◽  
Content Type ◽  
Membrane Pores ◽  
Photobacterium Damselae

ABSTRACTPhotobacterium damselaesubsp.damselae, an important pathogen of marine animals, may also cause septicemia or hyperaggressive necrotizing fasciitis in humans. We previously showed that hemolysin genes are critical for virulence of this organism in mice and fish. In the present study, we characterized thehlyAgene product, a putative small β-pore-forming toxin, and termed it phobalysin P (PhlyP), for “photobacterial lysin encoded on a plasmid.” PhlyP formed stable oligomers and small membrane pores, causing efflux of K+, with no significant leakage of lactate dehydrogenase but entry of vital dyes. The latter feature distinguished PhlyP from the relatedVibrio choleraecytolysin. Attack by PhlyP provoked a loss of cellular ATP, attenuated translation, and caused profound morphological changes in epithelial cells. In coculture experiments with epithelial cells,Photobacterium damselaesubsp.damselaeled to rapid hemolysin-dependent membrane permeabilization. Unexpectedly, hemolysins also promoted the association ofP. damselaesubsp.damselaewith epithelial cells. The collective observations of this study suggest that membrane-damaging toxins commonly enhance bacterial adherence.

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