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Abstract
Egress is a pivotal step in the life cycle of intracellular pathogens initiating the transition from an expiring host cell to a fresh target cell. While much attention has been focused on understanding cell invasion by intracellular pathogens, recent work is providing a new appreciation of mechanisms and therapeutic potential of microbial egress. This review highlights recent insight into cell egress by apicomplexan parasites and emerging contributions of membranolytic and proteolytic secretory products, along with host proteases. New findings suggest that Toxoplasma gondii secretes a pore-forming protein, TgPLP1, during egress that facilitates parasite escape from the cell by perforating the parasitophorous membrane. Also, in a cascade of proteolytic events, Plasmodium falciparum late-stage schizonts activate and secrete a subtilisin, PfSUB1, which processes enigmatic putative proteases called serine-repeat antigens that contribute to merozoite egress. A new report also suggests that calcium-activated host proteases called calpains aid parasite exit, possibly by acting upon the host cytoskeleton. Together these discoveries reveal important new molecular players involved in the principal steps of egress by apicomplexans.
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Affiliation(s)
- Marijo S Roiko
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, 48109, USA
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202
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Chia J, Yeo KP, Whisstock JC, Dunstone MA, Trapani JA, Voskoboinik I. Temperature sensitivity of human perforin mutants unmasks subtotal loss of cytotoxicity, delayed FHL, and a predisposition to cancer. Proc Natl Acad Sci U S A 2009; 106:9809-14. [PMID: 19487666 PMCID: PMC2701033 DOI: 10.1073/pnas.0903815106] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Indexed: 11/18/2022] Open
Abstract
The pore-forming protein perforin is critical for defense against many human pathogens and for preventing a catastrophic collapse of immune homeostasis, manifested in infancy as Type 2 familial hemophagocytic lymphohistiocytosis (FHL). However, no evidence has yet linked defective perforin cytotoxicity with cancer susceptibility in humans. Here, we examined perforin function in every patient reported in the literature who lived to at least 10 years of age without developing FHL despite inheriting mutations in both of their perforin (PRF1) alleles. Our analysis showed that almost 50% of these patients developed at least 1 hematological malignancy in childhood or adolescence. The broad range of pathologies argued strongly against a common environmental or viral cause for the extraordinary cancer incidence. Functionally, what distinguished these patients was their inheritance of PRF1 alleles encoding temperature-sensitive missense mutations. By contrast, truly null missense mutations with no rescue at the permissive temperature were associated with the more common severe presentation with FHL in early infancy. Our study provides the first mechanistic evidence for a link between defective perforin-mediated cytotoxicity and cancer susceptibility in humans and establishes the paradigm that temperature sensitivity of perforin function is a predictor of FHL severity.
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Affiliation(s)
- Jenny Chia
- Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne, Victoria 3002, Australia
| | - Kim Pin Yeo
- Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne, Victoria 3002, Australia
| | - James C. Whisstock
- Department of Biochemistry and Molecular Biology
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and
| | - Michelle A. Dunstone
- Department of Biochemistry and Molecular Biology
- Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia; and
| | - Joseph A. Trapani
- Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne, Victoria 3002, Australia
- Department of Biochemistry and Molecular Biology
- Department of Microbiology and Immunology and
| | - Ilia Voskoboinik
- Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne, Victoria 3002, Australia
- Department of Genetics, University of Melbourne, Parkville, Victoria 3010, Australia
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203
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Athanasopoulou S, Marioli D, Mikrou A, Papanastasiou AD, Zarkadis IK. Cloning and characterization of the trout perforin. FISH & SHELLFISH IMMUNOLOGY 2009; 26:908-912. [PMID: 19366634 DOI: 10.1016/j.fsi.2009.03.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 03/19/2009] [Accepted: 03/30/2009] [Indexed: 05/27/2023]
Abstract
The pore-forming protein, perforin is one of the effectors of cell-mediated killing. A perforin cDNA clone was isolated from rainbow trout (Oncorhynchus mykiss) after screening of a spleen cDNA library. The full-length cDNA is 2070 bp in size, encoding for a polypeptide of 589 amino acids. The predicted amino acid sequence of the trout perforin is 64, 58 and 40% identical to those of Japanese flounder, zebrafish and human perforins, respectively. Although its membrane attack complex/perforin (MACPF) domain is conserved, trout perforin shows low homology to human and trout terminal complement components (C6, C7, C8 and C9), ranging from 19 to 26% identity. Expression analysis reveals that the trout perforin gene is expressed in the blood, brain, heart, kidney, intestine and spleen. Phylogenetic analysis of proteins which belong to the MACPF superfamily clusters the trout perforin in the same group with other known perforins.
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Affiliation(s)
- Sofia Athanasopoulou
- Department of Biology, School of Medicine, University of Patras, Rion 26 500 Patras, Greece
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204
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Baran K, Dunstone M, Chia J, Ciccone A, Browne KA, Clarke CJP, Lukoyanova N, Saibil H, Whisstock JC, Voskoboinik I, Trapani JA. The molecular basis for perforin oligomerization and transmembrane pore assembly. Immunity 2009; 30:684-95. [PMID: 19446473 DOI: 10.1016/j.immuni.2009.03.016] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Revised: 11/24/2008] [Accepted: 03/06/2009] [Indexed: 01/30/2023]
Abstract
Perforin, a pore-forming protein secreted by cytotoxic lymphocytes, is indispensable for destroying virus-infected cells and for maintaining immune homeostasis. Perforin polymerizes into transmembrane channels that inflict osmotic stress and facilitate target cell uptake of proapoptotic granzymes. Despite this, the mechanism through which perforin monomers self-associate remains unknown. Our current study establishes the molecular basis for perforin oligomerization and pore assembly. We show that after calcium-dependent membrane binding, direct ionic attraction between the opposite faces of adjacent perforin monomers was necessary for pore formation. By using mutagenesis, we identified the opposing charges on residues Arg213 (positive) and Glu343 (negative) to be critical for intermolecular interaction. Specifically, disrupting this interaction had no effect on perforin synthesis, folding, or trafficking in the killer cell, but caused a marked kinetic defect of oligomerization at the target cell membrane, severely disrupting lysis and granzyme B-induced apoptosis. Our study provides important insights into perforin's mechanism of action.
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Affiliation(s)
- Katherine Baran
- Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne, Victoria 3002, Australia
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205
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Flanagan JJ, Tweten RK, Johnson AE, Heuck AP. Cholesterol exposure at the membrane surface is necessary and sufficient to trigger perfringolysin O binding. Biochemistry 2009; 48:3977-87. [PMID: 19292457 PMCID: PMC2825173 DOI: 10.1021/bi9002309] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Perfringolysin O (PFO) is the prototype for the cholesterol-dependent cytolysins, a family of bacterial pore-forming toxins that act on eukaryotic membranes. The pore-forming mechanism of PFO exhibits an absolute requirement for membrane cholesterol, but the complex interplay between the structural arrangement of the PFO C-terminal domain and the distribution of cholesterol in the target membrane is poorly understood. Herein we show that PFO binding to the bilayer and the initiation of the sequence of events that culminate in the formation of a transmembrane pore depend on the availability of free cholesterol at the membrane surface, while changes in the acyl chain packing of the phospholipids and cholesterol in the membrane core, or the presence or absence of detergent-resistant domains do not correlate with PFO binding. Moreover, PFO association with the membrane was inhibited by the addition of sphingomyelin, a typical component of membrane rafts in cell membranes. Finally, addition of molecules that do not interact with PFO, but intercalate into the membrane and displace cholesterol from its association with phospholipids (e.g., epicholesterol), reduced the amount of cholesterol required to trigger PFO binding. Taken together, our studies reveal that PFO binding to membranes is triggered when the concentration of cholesterol exceeds the association capacity of the phospholipids, and this cholesterol excess is then free to associate with the toxin.
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Affiliation(s)
- John J. Flanagan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
| | - Rodney K. Tweten
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Arthur E. Johnson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
- Department of Chemistry, Texas A&M University, College Station, Texas 77843
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Alejandro P. Heuck
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003
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206
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Bischofberger M, Gonzalez MR, van der Goot FG. Membrane injury by pore-forming proteins. Curr Opin Cell Biol 2009; 21:589-95. [PMID: 19442503 DOI: 10.1016/j.ceb.2009.04.003] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Revised: 04/06/2009] [Accepted: 04/06/2009] [Indexed: 02/02/2023]
Abstract
The plasma membrane defines the boundary of every living cell, and its integrity is essential for life. The plasma membrane may, however, be challenged by mechanical stress or pore-forming proteins produced by the organism itself or invading pathogens. We will here review recent findings about pore-forming proteins from different organisms, highlighting their structural and functional similarities, and describe the mechanisms that lead to membrane repair, since remarkably, cells can repair breaches in their plasma membrane of up to 10,000 microm(2).
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Affiliation(s)
- Mirko Bischofberger
- Ecole Polytechnique Fédérale de Lausanne, Global Health Institute, Lausanne, Switzerland
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207
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Lena G, Trapani JA, Sutton VR, Ciccone A, Browne KA, Smyth MJ, Denny WA, Spicer JA. Dihydrofuro[3,4-c]pyridinones as inhibitors of the cytolytic effects of the pore-forming glycoprotein perforin. J Med Chem 2009; 51:7614-24. [PMID: 19007200 DOI: 10.1021/jm801063n] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dihydrofuro[3,4-c]pyridinones are the first class of small molecules reported to inhibit the cytolytic effects of the lymphocyte toxin perforin. A lead structure was identified from a high throughput screen, and a series of analogues were designed and prepared to explore structure-activity relationships around the core bicyclic thioxofuropyridinone and pendant furan ring. This resulted in the identification of a submicromolar inhibitor of the perforin-induced lysis of Jurkat T-lymphoma cells.
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Affiliation(s)
- Gersande Lena
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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208
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Bourdeau RW, Malito E, Chenal A, Bishop BL, Musch MW, Villereal ML, Chang EB, Mosser EM, Rest RF, Tang WJ. Cellular functions and X-ray structure of anthrolysin O, a cholesterol-dependent cytolysin secreted by Bacillus anthracis. J Biol Chem 2009; 284:14645-56. [PMID: 19307185 DOI: 10.1074/jbc.m807631200] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Anthrolysin O (ALO) is a pore-forming, cholesterol-dependent cytolysin (CDC) secreted by Bacillus anthracis, the etiologic agent for anthrax. Growing evidence suggests the involvement of ALO in anthrax pathogenesis. Here, we show that the apical application of ALO decreases the barrier function of human polarized epithelial cells as well as increases intracellular calcium and the internalization of the tight junction protein occludin. Using pharmacological agents, we also found that barrier function disruption requires increased intracellular calcium and protein degradation. We also report a crystal structure of the soluble state of ALO. Based on our analytical ultracentrifugation and light scattering studies, ALO exists as a monomer. Our ALO structure provides the molecular basis as to how ALO is locked in a monomeric state, in contrast to other CDCs that undergo antiparallel dimerization or higher order oligomerization in solution. ALO has four domains and is globally similar to perfringolysin O (PFO) and intermedilysin (ILY), yet the highly conserved undecapeptide region in domain 4 (D4) adopts a completely different conformation in all three CDCs. Consistent with the differences within D4 and at the D2-D4 interface, we found that ALO D4 plays a key role in affecting the barrier function of C2BBE cells, whereas PFO domain 4 cannot substitute for this role. Novel structural elements and unique cellular functions of ALO revealed by our studies provide new insight into the molecular basis for the diverse nature of the CDC family.
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Affiliation(s)
- Raymond W Bourdeau
- Ben-May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637, USA
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209
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Andreeva-Kovalevskaya ZI, Solonin AS, Sineva EV, Ternovsky VI. Pore-forming proteins and adaptation of living organisms to environmental conditions. BIOCHEMISTRY (MOSCOW) 2009; 73:1473-92. [DOI: 10.1134/s0006297908130087] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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210
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Kafsack BFC, Pena JDO, Coppens I, Ravindran S, Boothroyd JC, Carruthers VB. Rapid membrane disruption by a perforin-like protein facilitates parasite exit from host cells. Science 2008; 323:530-3. [PMID: 19095897 DOI: 10.1126/science.1165740] [Citation(s) in RCA: 216] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Perforin-like proteins are expressed by many bacterial and protozoan pathogens, yet little is known about their function or mode of action. Here, we describe Toxoplasma perforin-like protein 1 (TgPLP1), a secreted perforin-like protein of the intracellular protozoan pathogen Toxoplasma gondii that displays structural features necessary for pore formation. After intracellular growth, TgPLP1-deficient parasites failed to exit normally, resulting in entrapment within host cells. We show that this defect is due to an inability to rapidly permeabilize the parasitophorous vacuole membrane and host plasma membrane during exit. TgPLP1 ablation had little effect on growth in culture but resulted in a reduction greater than five orders of magnitude of acute virulence in mice. Perforin-like proteins from other intracellular pathogens may play a similar role in microbial egress and virulence.
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Affiliation(s)
- Björn F C Kafsack
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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211
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Kayed R, Pensalfini A, Margol L, Sokolov Y, Sarsoza F, Head E, Hall J, Glabe C. Annular protofibrils are a structurally and functionally distinct type of amyloid oligomer. J Biol Chem 2008; 284:4230-7. [PMID: 19098006 DOI: 10.1074/jbc.m808591200] [Citation(s) in RCA: 257] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Amyloid oligomers are believed to play causal roles in several types of amyloid-related neurodegenerative diseases. Several different types of amyloid oligomers have been reported that differ in morphology, size, or toxicity, raising the question of the pathological significance and structural relationships between different amyloid oligomers. Annular protofibrils (APFs) have been described in oligomer preparations of many different amyloidogenic proteins and peptides as ring-shaped or pore-like structures. They are interesting because their pore-like morphology is consistent with numerous reports of membrane-permeabilizing activity of amyloid oligomers. Here we report the preparation of relatively homogeneous preparations of APFs and an antiserum selective for APFs (alphaAPF) compared with prefibrillar oligomers (PFOs) and fibrils. PFOs appear to be precursors for APF formation, which form in high yield after exposure to a hydrophobic-hydrophilic interface. Surprisingly, preformed APFs do not permeabilize lipid bilayers, unlike the precursor PFOs. APFs display a conformation-dependent, generic epitope that is distinct from that of PFOs and amyloid fibrils. Incubation of PFOs with phospholipids vesicles results in a loss of PFO immunoreactivity with a corresponding increase in alphaAPF immunoreactivity, suggesting that lipid vesicles catalyze the conversion of PFOs into APFs. The annular anti-protofibril antibody also recognizes heptameric alpha-hemolysin pores, but not monomers, suggesting that the antibody recognizes an epitope that is specific for a beta barrel structural motif.
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Affiliation(s)
- Rakez Kayed
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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212
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Beinrohr L, Dobó J, Závodszky P, Gál P. C1, MBL-MASPs and C1-inhibitor: novel approaches for targeting complement-mediated inflammation. Trends Mol Med 2008; 14:511-21. [PMID: 18977695 DOI: 10.1016/j.molmed.2008.09.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 09/26/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
Complement activation is initiated by the pattern-recognition molecules complement component C1q, mannose-binding lectin (MBL) and ficolins (H-, L-, M-ficolin), which typically recognize antibody-antigen complexes or foreign polysaccharides. The associated proteases (C1r, C1s, MASP-1 and MASP-2) then activate the complement system. The serpin C1-inhibitor (C1-inh) blocks activity of all these complexes and has been successfully used in models of disease. Many structures of these components became available recently, including that of C1-inh, facilitating the structure-guided design of drugs targeting complement activation. Here, we propose an approach in which therapeutic proteins are made up of natural protein domains and C1-inh to allow targeting to the site of inflammation and more specific inhibition of complement activation. In particular, engineering a fast-acting C1-inh or fusing it to an 'aiming module' has been shown to be feasible and economical using a humanized yeast expression system. Complement-mediated inflammation has been linked to ischemia-reperfusion injury, organ graft rejection and even neurodegeneration, so targeting this process has direct clinical implications.
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Affiliation(s)
- László Beinrohr
- Institute of Enzymology, Karolina út 29, H-1113 Budapest, Hungary.
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213
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Anderluh G, Lakey JH. Disparate proteins use similar architectures to damage membranes. Trends Biochem Sci 2008; 33:482-90. [PMID: 18778941 DOI: 10.1016/j.tibs.2008.07.004] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 06/22/2008] [Accepted: 07/24/2008] [Indexed: 01/30/2023]
Abstract
Membrane disruption can efficiently alter cellular function; indeed, pore-forming toxins (PFTs) are well known as important bacterial virulence factors. However, recent data have revealed that structures similar to those found in PFTs are found in membrane active proteins across disparate phyla. Many similarities can be identified only at the 3D-structural level. Of note, domains found in membrane-attack complex proteins of complement and perforin (MACPF) resemble cholesterol-dependent cytolysins from Gram-positive bacteria, and the Bcl family of apoptosis regulators share similar architectures with Escherichia coli pore-forming colicins. These and other correlations provide considerable help in understanding the structural requirements for membrane binding and pore formation.
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Affiliation(s)
- Gregor Anderluh
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, 1000, Ljubljana, Slovenia.
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214
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Granzyme B delivery via perforin is restricted by size, but not by heparan sulfate-dependent endocytosis. Proc Natl Acad Sci U S A 2008; 105:13799-804. [PMID: 18772390 DOI: 10.1073/pnas.0801724105] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
How granzymes gain entry into the cytosol of target cells during killer cell attack has been the subject of several studies in the past, but the effective delivery mechanism during target cell encounter has not been clarified. Here we show that granzyme B (GzmB) mutants lacking binding to negatively charged, essentially heparan-sulfate-containing membrane receptors are poorly endocytosed yet are delivered to the cytosol with efficacy similar to that of WT GzmB. In a cell-based system GzmB-deficient natural killer cells provided perforin (pfn) by natural polarized secretion and synergized with externally added GzmB. Whereas receptor (heparan sulfate)-dependent endocytosis was dispensable, delivery of larger cargo like that of GzmB fusion proteins and GzmB-antibody complexes was restricted by their size. Our data support the model in which granzymes are primarily translocated through repairable membrane pores of finite size and not by the disruption of endocytosed vesicles. We conclude that structurally related translocators, i.e., perforin and cholesterol-dependent cytolysins, deliver deathly cargo across host cell membranes in a similar manner.
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215
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Carrero JA, Vivanco-Cid H, Unanue ER. Granzymes drive a rapid listeriolysin O-induced T cell apoptosis. THE JOURNAL OF IMMUNOLOGY 2008; 181:1365-74. [PMID: 18606691 DOI: 10.4049/jimmunol.181.2.1365] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The Listeria monocytogenes protein listeriolysin O (LLO) is a pore-forming protein essential for virulence. Although the major role for LLO is to allow L. monocytogenes entry into the cytosol, it also induces apoptosis of activated lymphocytes, an obligatory cellular response that modulates the infection. Induction of apoptosis by LLO proceeds through a fast, caspase-dependent pathway and a slow, caspase-independent pathway. Polyclonal T cell lines were generated from either normal mice or mice deficient in granzyme and perforin proteins, and then treated with apoptogenic doses of LLO. In this study we show that apoptosis of lymphocytes induced by LLO was characterized by activation of caspases as quickly as 30 min that was dependent on the expression of granzymes. In the absence of granzymes, all parameters of apoptosis such as caspase activation, phosphatidylserine exposure, mitochondrial depolarization, and DNA fragmentation were dramatically reduced in magnitude. Removal of perforin inhibited the apoptotic effect of LLO on cells by approximately 50%. Neutralization of intracellular acidification using chloroquine inhibited the rapid apoptotic death. In agreement with these findings granzyme-deficient mice harbored lower bacterial titers and decrease splenic pathology compared with normal mice following L. monocytogenes infection. Thus, LLO exploits apoptotic enzymes of the adaptive immune response to eliminate immune cells and increase its virulence.
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Affiliation(s)
- Javier A Carrero
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO 63110, USA
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216
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Cellular sterol trafficking and metabolism: spotlight on structure. Curr Opin Cell Biol 2008; 20:371-7. [DOI: 10.1016/j.ceb.2008.03.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 03/30/2008] [Accepted: 03/31/2008] [Indexed: 11/20/2022]
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217
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Rosado CJ, Kondos S, Bull TE, Kuiper MJ, Law RHP, Buckle AM, Voskoboinik I, Bird PI, Trapani JA, Whisstock JC, Dunstone MA. The MACPF/CDC family of pore-forming toxins. Cell Microbiol 2008; 10:1765-74. [PMID: 18564372 PMCID: PMC2654483 DOI: 10.1111/j.1462-5822.2008.01191.x] [Citation(s) in RCA: 211] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pore-forming toxins (PFTs) are commonly associated with bacterial pathogenesis. In eukaryotes, however, PFTs operate in the immune system or are deployed for attacking prey (e.g. venoms). This review focuses upon two families of globular protein PFTs: the cholesterol-dependent cytolysins (CDCs) and the membrane attack complex/perforin superfamily (MACPF). CDCs are produced by Gram-positive bacteria and lyse or permeabilize host cells or intracellular organelles during infection. In eukaryotes, MACPF proteins have both lytic and non-lytic roles and function in immunity, invasion and development. The structure and molecular mechanism of several CDCs are relatively well characterized. Pore formation involves oligomerization and assembly of soluble monomers into a ring-shaped pre-pore which undergoes conformational change to insert into membranes, forming a large amphipathic transmembrane β-barrel. In contrast, the structure and mechanism of MACPF proteins has remained obscure. Recent crystallographic studies now reveal that although MACPF and CDCs are extremely divergent at the sequence level, they share a common fold. Together with biochemical studies, these structural data suggest that lytic MACPF proteins use a CDC-like mechanism of membrane disruption, and will help understand the roles these proteins play in immunity and development.
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Affiliation(s)
- Carlos J Rosado
- Department of Biochemistry, Monash University, Clayton, Victoria 3800, Australia
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218
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Sonnen AFP, Rowe AJ, Andrew PW, Gilbert RJ. Oligomerisation of pneumolysin on cholesterol crystals: Similarities to the behaviour of polyene antibiotics. Toxicon 2008; 51:1554-9. [DOI: 10.1016/j.toxicon.2008.03.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 03/21/2008] [Accepted: 03/25/2008] [Indexed: 11/27/2022]
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219
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Functional and phylogenetic characterization of Vaginolysin, the human-specific cytolysin from Gardnerella vaginalis. J Bacteriol 2008; 190:3896-903. [PMID: 18390664 DOI: 10.1128/jb.01965-07] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pore-forming toxins are essential to the virulence of a wide variety of pathogenic bacteria. Gardnerella vaginalis is a bacterial species associated with bacterial vaginosis (BV) and its significant adverse sequelae, including preterm birth and acquisition of human immunodeficiency virus. G. vaginalis makes a protein toxin that generates host immune responses and has been hypothesized to be involved in the pathogenesis of BV. We demonstrate that G. vaginalis produces a toxin (vaginolysin [VLY]) that is a member of the cholesterol-dependent cytolysin (CDC) family, most closely related to intermedilysin from Streptococcus intermedius. Consistent with this predicted relationship, VLY lyses target cells in a species-specific manner, dependent upon the complement regulatory molecule CD59. In addition to causing erythrocyte lysis, VLY activates the conserved epithelial p38 mitogen-activated protein kinase pathway and induces interleukin-8 production by human epithelial cells. Transfection of human CD59 into nonsusceptible cells renders them sensitive to VLY-mediated lysis. In addition, a single amino acid substitution in the VLY undecapeptide [VLY(P480W)] generates a toxoid that does not form pores, and introduction of the analogous proline residue into another CDC, pneumolysin, significantly decreases its cytolytic activity. Further investigation of the mechanism of action of VLY may improve understanding of the functions of the CDC family as well as diagnosis and therapy for BV.
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Slade DJ, Lovelace LL, Chruszcz M, Minor W, Lebioda L, Sodetz JM. Crystal structure of the MACPF domain of human complement protein C8 alpha in complex with the C8 gamma subunit. J Mol Biol 2008; 379:331-42. [PMID: 18440555 DOI: 10.1016/j.jmb.2008.03.061] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 03/21/2008] [Accepted: 03/21/2008] [Indexed: 11/27/2022]
Abstract
Human C8 is one of five complement components (C5b, C6, C7, C8, and C9) that assemble on bacterial membranes to form a porelike structure referred to as the "membrane attack complex" (MAC). C8 contains three genetically distinct subunits (C8 alpha, C8 beta, C8 gamma) arranged as a disulfide-linked C8 alpha-gamma dimer that is noncovalently associated with C8 beta. C6, C7 C8 alpha, C8 beta, and C9 are homologous. All contain N- and C-terminal modules and an intervening 40-kDa segment referred to as the membrane attack complex/perforin (MACPF) domain. The C8 gamma subunit is unrelated and belongs to the lipocalin family of proteins that display a beta-barrel fold and generally bind small, hydrophobic ligands. Several hundred proteins with MACPF domains have been identified based on sequence similarity; however, the structure and function of most are unknown. Crystal structures of the secreted bacterial protein Plu-MACPF and the human C8 alpha MACPF domain were recently reported and both display a fold similar to those of the bacterial pore-forming cholesterol-dependent cytolysins (CDCs). In the present study, we determined the crystal structure of the human C8 alpha MACPF domain disulfide-linked to C8 gamma (alphaMACPF-gamma) at 2.15 A resolution. The alphaMACPF portion has the predicted CDC-like fold and shows two regions of interaction with C8 gamma. One is in a previously characterized 19-residue insertion (indel) in C8 alpha and fills the entrance to the putative C8 gamma ligand-binding site. The second is a hydrophobic pocket that makes contact with residues on the side of the C8 gamma beta-barrel. The latter interaction induces conformational changes in alphaMACPF that are likely important for C8 function. Also observed is structural conservation of the MACPF signature motif Y/W-G-T/S-H-F/Y-X(6)-G-G in alphaMACPF and Plu-MACPF, and conservation of several key glycine residues known to be important for refolding and pore formation by CDCs.
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Affiliation(s)
- Daniel J Slade
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
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Iacovache I, van der Goot FG, Pernot L. Pore formation: an ancient yet complex form of attack. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1611-23. [PMID: 18298943 DOI: 10.1016/j.bbamem.2008.01.026] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 01/03/2008] [Accepted: 01/04/2008] [Indexed: 02/07/2023]
Abstract
Bacteria, as well as higher organisms such as sea anemones or earthworms, have developed sophisticated virulence factors such as the pore-forming toxins (PFTs) to mount their attack against the host. One of the most fascinating aspects of PFTs is that they can adopt a water-soluble form at the beginning of their lifetime and become an integral transmembrane protein in the membrane of the target cells. There is a growing understanding of the sequence of events and the various conformational changes undergone by these toxins in order to bind to the host cell surface, to penetrate the cell membranes and to achieve pore formation. These points will be addressed in this review.
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Affiliation(s)
- Ioan Iacovache
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Faculty of Life Sciences, Station 15, Lausanne, Switzerland
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222
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Friend or foe: the same fold for attack and defense. Trends Immunol 2008; 29:51-3. [PMID: 18248850 DOI: 10.1016/j.it.2007.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 11/26/2007] [Accepted: 11/27/2007] [Indexed: 11/21/2022]
Abstract
Two recent crystal structures of membrane attack complex/perforin (MACPF) domains found in the complement and perforin families unexpectedly reveal that some proteins of the immune system share a common core fold with their bacterial targets. Although a relationship between MACPF proteins and the previously characterized bacterial cholesterol-dependent cytolysins (CDCs) is not detectable by sequence analysis, the MACPF structures show that eukaryotic defense and bacterial CDC attack share a common mechanism of membrane insertion and pore formation.
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Konagurthu AS, Stuckey PJ, Lesk AM. Structural search and retrieval using a tableau representation of protein folding patterns. ACTA ACUST UNITED AC 2008; 24:645-51. [PMID: 18175768 DOI: 10.1093/bioinformatics/btm641] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
UNLABELLED Comparison and classification of folding patterns from a database of protein structures is crucial to understand the principles of protein architecture, evolution and function. Current search methods for proteins with similar folding patterns are slow and computationally intensive. The sharp growth in the number of known protein structures poses severe challenges for methods of structural comparison. There is a need for methods that can search the database of structures accurately and rapidly. We provide several methods to search for similar folding patterns using a concise tableau representation of proteins that encodes the relative geometry of secondary structural elements. Our first approach allows the extraction of identical and very closely-related protein folding patterns in constant-time (per hit). Next, we address the hard computational problem of extraction of maximally-similar subtableaux, when comparing two tableaux. We solve the problem using Quadratic and Linear integer programming formulations and demonstrate their power to identify subtle structural similarities, especially when protein structures significantly diverge. Finally, we describe a rapid and accurate method for comparing a query structure against a database of protein domains, TableauSearch. TableauSearch is rapid enough to search the entire structural database in seconds on a standard desktop computer. Our analysis of TableauSearch on many queries shows that the method is very accurate in identifying similarities of folding patterns, even between distantly related proteins. AVAILABILITY A web server implementing the TableauSearch is available from http://hollywood.bx.psu.edu/TabSearch.
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Affiliation(s)
- Arun S Konagurthu
- Department of Biochemistry and Molecular Biology and The Huck Institute for Genomics, Proteomics and Bioinformatics, The Pennsylvania State University, University Park, PA 16802, USA.
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224
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Abstract
The apicomplexa are parasitic protozoa that are responsible for important human and animal diseases, including malaria, toxoplasmosis, cryptosporidiosis, coccidiosis and babesiosis. Like other members of the superphylum Alveolata, apicomplexans have regulated exocytosis of specialized secretory organelles, such as the apicomplexan-specific rhoptries and micronemes that are required for host cell invasion. The secretions of another class of organelles, the dense granules and osmiophilic bodies, are proposed to be required for maintenance of the parasitophorous vacuole and host cell egress. Little is known about the osmiophilic bodies and to date only one protein, P377, has been localized to this organelle. In this issue, de Koning-Ward et al. describe the disruption of pfg377 in the virulent human malaria parasite, Plasmodium falciparum, which results in reduced osmiophilic body formation, a marked decrease in female fitness, and dramatically impaired infectivity to mosquitoes. These findings suggest that targeting PFG377 may be a strategy to block parasite transmission.
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Affiliation(s)
- Karen Hayton
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-8132, USA.
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