Sucharit Bhakdi

Sucharit Bhakdi
Johannes Gutenberg-Universität Mainz | JGU · Institut für Medizinische Mikrobiologie und Hygiene

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381
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Introduction

Publications

Publications (381)
Article
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Asymmetrical distribution of lipids in the cell membrane is a fundamental feature of all eukaryotic cells. The most important negatively charged phospholipids phosphatidylserine (PS) and phosphatidylinositol species reside almost exclusively in the cytoplasmic leaflet, where they serve as essential co-factors for many membrane-bound enzymes includi...
Article
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ADAM17, a prominent member of the ‘Disintegrin and Metalloproteinase’ (ADAM) family, controls vital cellular functions through cleavage of transmembrane substrates. Here we present evidence that surface exposure of phosphatidylserine (PS) is pivotal for ADAM17 to exert sheddase activity. PS exposure is tightly coupled to substrate shedding provoked...
Article
Full-text available
The digestive vacuole (DV) of Plasmodium falciparum, which is released into the bloodstream upon rupture of each parasitized red blood cell (RBC), was recently discovered to activate the alternative complement pathway. In the present work, we show that C3- and C5-convertases assembling on the parasitic organelle are able to provoke deposition of ac...
Article
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The Collaborative Research Center 490 was founded in 2000 and devoted itself over a period of 12 years to the study of cellular and molecular mechanisms underlying invasion and persistence of infectious agents in the host. A broad range of pathogens, all of major medical importance, were studied with two long-term objectives. The first was to expan...
Article
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Human umbilical cord vein endothelial cells (HUVECs) secrete a number of factors which greatly impact the proliferation and differentiation of hematopoietic stem and progenitor cells (HSPC). These factors remain largely unknown. Here, we report on the most comprehensive proteomic profiling of the HUVEC secretome and identified 827 different secrete...
Article
Atherosclerosis is widely regarded as a chronic inflammatory disease that develops as a consequence of entrapment of oxidized low-density lipoprotein (LDL) in the arterial intima and its interaction with components of both innate and adaptive immunity. This article reviews the role of the complement system in the context of a different concept on a...
Article
Membrane-perturbating proteins and peptides are widespread agents in biology. Pore-forming bacterial toxins represent major virulence factors of pathogenic microorganisms. Membrane-damaging peptides constitute important antimicrobial effectors of innate immunity. Membrane perturbation can incur multiple responses in mammalian cells. The present dis...
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Plasmodium falciparum malaria claims 1 million lives around the globe every year. Parasitemia can reach remarkably high levels. The developing parasite digests hemoglobin and converts the waste product to hemozoin alias malaria pigment. These processes occur in a vesicular compartment named the digestive vacuole (DV). Each parasitized cell releases...
Article
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Melittin, the major component of the bee venom, is an amphipathic, cationic peptide with a wide spectrum of biological properties that is being considered as an anti-inflammatory and anti-cancer agent. It modulates multiple cellular functions but the underlying mechanisms are not clearly understood. Here, we report that melittin activates disintegr...
Article
In the summer of 2010, parenteral nutrition (PN) admixtures were administered to neonates in the Pediatric Department of the University Medical Center Mainz that provoked severe clinical sequelae. Contamination of a dummy infusion with Enterobacter cloacae and Escherichia hermannii was detected on the day of the incident, and the same isolates were...
Article
Full-text available
Severe Plasmodium falciparum malaria evolves through the interplay among capillary sequestration of parasitized erythrocytes, deregulated inflammatory responses, and hemostasis dysfunction. After rupture, each parasitized erythrocyte releases not only infective merozoites, but also the digestive vacuole (DV), a membrane-bounded organelle containing...
Article
Full-text available
Sequestration of parasitized erythrocytes and dysregulation of the coagulation and complement system are hallmarks of severe Plasmodium falciparum malaria. A link between these events emerged through the discovery that the parasite digestive vacuole (DV), which is released together with infective merozoites into the bloodstream, dually activates th...
Article
Full-text available
The disintegrin-metalloproteinases ADAM10 and ADAM17 mediate the release of several cell signaling molecules and cell adhesion molecules such as vascular endothelial cadherin or L-selectin affecting endothelial permeability and leukocyte transmigration. Dysregulation of ADAM activity may contribute to the pathogenesis of vascular diseases, but the...
Article
Objective: The bulk of LDL entrapped in the arterial intima is modified by hydrolytic enzymes, leading to extensive cleavage of cholesterylesters and liberation of fatty acids. The latter induce apoptosis in endothelial cells but are far less cytotoxic towards macrophages. We have compared the cytotoxic effects of enzymatically modified LDL (E-LDL...
Article
Although there is a statistically significant association between modestly raised baseline plasma C-reactive protein (CRP) values and future cardiovascular events, the debate is still unsettled in regard to whether CRP plays a causal role in the pathogenesis of atherosclerosis. We generated 2 lines of transgenic (Tg) rabbits expressing human CRP (h...
Article
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Programs for vaccination against the new influenza A/H1N1 targeting many hundred million citizens in Europe and the USA are to be launched in the fall of this year. The USA is planning to employ a non-adjuvanted vaccine, whereas European nations are opting for inclusion of MF59, the adjuvant contained in an alternative seasonal flu vaccine, or the...
Article
Mitogen activated protein kinase (MAPK) p38 has emerged as a survival protein in cells that are attacked by bacterial toxins forming small membrane pores. Activation of p38 by pore forming toxins (PFT) has been attributed to osmotic stress, but here we show that loss of K+ is likely to be the critical parameter. Several lines of evidence support th...
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Full-text available
Vibrio cholerae cytolysin (VCC) forms SDS-stable heptameric beta-barrel transmembrane pores in mammalian cell membranes. In contrast to structurally related pore formers of gram-positive organisms, no oligomeric prepore stage of assembly has been detected to date. In the present study, disulfide bonds were engineered to tie the pore-forming amino a...
Article
Sheep erythrocyte membranes lysed with human complement were solubilized in 1% Berol EMU-043 (w/v) and subjected to crossed immunoelectrophoresis in the presence of this detergent. Using antibodies to human serum proteins, we found 5–6 protein precipitates whose presence was dependent on complement action. Among these, C3 and C4 components of compl...
Article
Although atherosclerosis in infants and children is generally acknowledged, the temporal and spatial sequence of LDL insudation, modification and intimal monocyte accumulation has not been systematically studied. We have investigated herein very early stages of lesion formation in human aortas of individuals up to the age of 15 years. Aortic specim...
Article
Mast cells are known to be important effector cells in innate immune responses to bacterial infections. However, up to now, neither the mechanisms nor the relevance of mast cell degranulation in innate skin immune responses to bacteria have been adequately addressed. In this article, we show that the bacterial toxins streptolysin O (SLO) and alpha-...
Article
Staphylococcus aureus alpha-toxin is the archetype of bacterial pore forming toxins and a key virulence factor secreted by the majority of clinical isolates of S. aureus. Toxin monomers bind to target cells and oligomerize to form small beta-barrel pores in the plasma membrane. Many nucleated cells are able to repair a limited number of lesions by...
Article
There is evidence that low-density lipoprotein (LDL) is modified by hydrolytic enzymes, and that the product (E-LDL) induces selective production of interleukin 8 (IL-8) in endothelial cells. Since nuclear factor-kappaB (NF-kappaB) is a major regulator of IL-8 transcription, we studied its activation in endothelial cells treated with E-LDL. Unexpec...
Article
Vibrio cholerae cytolysin (VCC) is a pore-forming toxin that is secreted in precursor form (pro-VCC) and requires proteolytic cleavage in order to attain membrane-permeabilizing properties. Pro-VCC can be activated both in solution and membrane-bound state. Processing of membrane-bound pro-VCC can in turn be achieved through the action of both cell...
Article
We have previously reported that endotoxin accelerates atherosclerosis in rabbits on hypercholesterolemic diet. To investigate whether this phenomenon depends on the activation of the terminal complement sequence, we repeated the experiment using complement C6-deficient rabbits. C6 -/- rabbits were fed a hypercholesterolemic diet and received eithe...
Article
Abstract Escherichia coli hemolysin is a pore-forming protein belonging to the RTX toxin family. Cysteine scanning mutagenesis was performed to characterize the putative pore-forming domain of the molecule. A single cysteine residue was introduced at 48 positions within the sequence spanning residues 170-400 and labeled with the polarity-sensitive...
Article
Following entrapment in the arterial intima, low-density lipoprotein (LDL) can be modified by hydrolytic enzymes to yield a lipoprotein derivative that binds C-reactive protein, activates complement, and is rapidly taken up by monocytes/macrophages. Free fatty acids contained in enzymatically modified LDL (E-LDL) render the lipoprotein cytotoxic du...
Chapter
Origin of Pore-forming Toxins (PFTs)Evolution of the PFT FieldRelationship to Other ToxinsMolecular Mechanism of ActionCell-biological EffectsPathogenic AspectsPurification ProtocolsApplication of PFTs as Tools in ResearchReagents and Chemicals
Article
The association between increased concentrations of C-reactive protein (CRP) and future cardiovascular events is well established. However, it is currently unclear whether this clinical observation represents an epiphenomenon or whether the pentraxin may actively promote the development of atherosclerosis. Experimental studies with knockout mice wi...
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Full-text available
We describe an unusual clinical strain of catalase-negative methicillin-resistant Staphylococcus aureus sensu stricto. Sequence analysis of its catalase gene showed 99.60% identities to the catalase genes of the reference strains. A 5-base deletion, however, led to a shift of the nucleotide reading frame and a loss of the enzymatic activity.
Article
Atherosclerosis is widely regarded as a chronic inflammatory disease that develops as a consequence of entrapment of low density lipoprotein (LDL) in the arterial intima. Native LDL lacks inflammatory properties, so the lipoprotein must undergo biochemical alterations in order to become atherogenic. Modification is commonly regarded as being danger...
Article
Staphylococcal alpha-toxin is an archetypal killer protein that homo-oligomerizes in target cells to create small transmembrane pores. The membrane-perforating beta-barrel motif is a conserved attack element of cytolysins of Gram-positive and Gram-negative bacteria. Following the recognition that nucleated cells can survive membrane permeabilizatio...
Article
Full-text available
High susceptibility of rabbit erythrocytes toward the poreforming action of staphylococcal α-toxin correlates with the presence of saturable, high affinity binding sites. All efforts to identify a protein or glycolipid receptor have failed, and the fact that liposomes composed solely of phosphatidylcholine are efficiently permeabilized adds to the...
Article
Following the observation that cells are able to recover from membrane lesions incurred by Staphylococcus aureus alpha-toxin and streptolysin O (SLO), we investigated the role of p38 in this process. p38 phosphorylation occurred in response to attack by both toxins, commencing within minutes after toxin treatment and waning after several hours. Whi...
Article
Early identification of Acanthamoeba in cerebrospinal fluid is mandatory to prevent fatal granulomatous amebic encephalitis. In the case presented here amebic trophozoites were detected in a routine cerebrospinal fluid sample. The antibiotic treatment and the apparently low virulence of this isolate were responsible for the benign progression of th...
Article
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Escherichia coli alpha-hemolysin (HlyA), archetype of a bacterial pore-forming toxin, has been reported to deregulate physiological Ca2+ channels, thus inducing periodic low-frequency Ca2+ oscillations that trigger transcriptional processes in mammalian cells. The present study was undertaken to delineate the mechanisms underlying the Ca2+ oscillat...
Article
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Vascular leakage and shock are the major causes of death in patients with dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Thirty years ago, complement activation was proposed to be a key underlying event, but the cause of complement activation has remained unknown. The major nonstructural dengue virus (DV) protein NS1 was tested for...
Article
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Production of a single cysteine substitution mutant, S177C, allowed Escherichia coli hemolysin (HlyA) to be radioactively labeled with tritiated N-ethylmaleimide without affecting biological activity. It thus became possible to study the binding characteristics of HlyA as well as of toxin mutants in which one or both acylation sites were deleted. A...
Article
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Staphylococcal gamma-hemolysins are bicomponent toxins forming a protein family with leucocidins and alpha-toxin. Two active toxins (AB and CB) can be formed combining one of the class-S components, HlgA or HlgC, with the class-F component HlgB. These two gamma-hemolysins form pores with marked similarities to alpha-toxin in terms of conductance, n...
Article
Human C-reactive protein (CRP) was reported to accelerate atherosclerotic lesion development in male but not in female apolipoprotein E (apoE) knockout mice. Here, mice expressing rabbit CRP (rbCRP) were crossbred onto apoE knockout animals, and the effect on atherogenesis was studied. Hemolytic complement activity could not be detected in apoE kno...
Article
Full-text available
Enzymatic modification of low-density lipoprotein (LDL) as it probably occurs in the arterial intima drastically increases its cytotoxicity, which could be relevant for the progression of atherosclerotic lesions. LDL was treated with a protease and cholesterylesterase to generate a derivative similar to lesional LDL, with a high content of free cho...
Article
Vibrio cholerae cytolysin (VCC) is an oligomerizing pore-forming toxin that is related to cytolysins of many other Gram-negative organisms. VCC contains six cysteine residues, of which two were found to be present in free sulphydryl form. The positions of two intramolecular disulphide bonds were mapped, and one was shown to be essential for correct...
Chapter
Staphylococcal alpha-toxin, archetype of an oligomerizing pore-forming toxin, is produced and secreted as a water-soluble 34 kD monomer. High affinity binding possibly occurs to clustered phosphocholine head groups in cholesterol/sphingomyelin-rich membrane microdomains. Toxin heptamers can rapidly assemble at such sites, and oligomerization trigge...
Article
Functionally interactive proteases of the plasminogen/plasmin and the matrix metalloproteinase (MMP) system degrade and reorganize the extracellular matrix of the vessel wall in atherosclerosis. Here we investigated whether such proteases are able to confer atherogenic properties onto low density lipoprotein by nonoxidative modification. Similar to...
Article
Full-text available
Streptolysin O (SLO) is the prototype of a family of cytolysins that consists of proteins which bind to cholesterol and form very large transmembrane pores. Structure/function studies on the pore-forming cytolysin SLO have been complicated by the proteolytic inactivation of a substantial portion of recombinant SLO (rSLO) expressed in Escherichia co...
Article
Full-text available
Many strains of Vibrio cholerae produce a cytolysin (VCC) that forms oligomeric transmembrane pores in animal cells. The molecule is secreted as a procytolysin (pro-VCC) of 79 kDa that must be cleaved at the N terminus to generate the active 65-kDa toxin. Processing can occur in solution, and previous studies have described the action of mature VCC...
Article
Atherosclerosis is widely regarded as a chronic inflammatory disease that develops as a consequence of entrapment of low density lipoprotein (LDL) in the arterial intima. Native LDL lacks inflammatory properties, so the lipoprotein must undergo biochemical alterations in order to become atherogenic. Modification is commonly regarded as being danger...
Article
Previous work indicated that enzymatically remodeled LDL (E-LDL) might activate complement in atherosclerotic lesions via a C-reactive protein (CRP)-dependent and CRP-independent pathway. We sought to substantiate this contention and determine whether both pathways drive the sequence to completion. E-LDL was prepared by sequential treatment of LDL...
Article
Full-text available
Streptolysin O (SLO), a major virulence factor of pyogenic streptococci, binds to cholesterol in the membranes of eukaryotic cells and oligomerizes to form large transmembrane pores. While high toxin doses are rapidly cytocidal, low doses are tolerated because a limited number of lesions can be resealed. Here, we report that at sublethal doses, SLO...
Article
According to the textbooks, oxidative processes transform low density lipoprotein (LDL) to an atherogenic moiety. Oxidized LDL contains potentially harmful constituents that induce inflammatory responses in endothelial cells, smooth muscle cells and macrophages. The oxidation hypothesis, born 20 years ago through the work of Steinberg and colleague...
Article
Modification with proteases and cholesterylesterase transforms LDL to a moiety that resembles lipoproteins isolated from atherosclerotic lesions and possesses atherogenic properties. To identify changes in monocyte-derived foam cells laden with enzymatically modified LDL (E-LDL), we compared patterns of the most abundant transcripts in these cells...
Article
Full-text available
Treatment of low-density lipoprotein (LDL) with a protease and cholesterolesterase transforms the lipoprotein to an entity that resembles lipoprotein particles in atherosclerotic lesions, which have a high content of free cholesterol, reflecting extensive de-esterification in the intima. Because de-esterification would occur beneath the endothelium...
Article
The Vibrio cholerae cytolysin (VCC) 63-kDa monomer has been shown to interact in aqueous suspension with cholesterol microcystals to produce a ring/pore-like heptameric oligomer approximately 8 nm in outer diameter. Transmission electron microscopy data were produced from cholesterol samples adsorbed to carbon support films, spread across the holes...
Article
To evaluate the effects of an early, short-term albumin infusion on mesenteric microcirculation and global hemodynamics in hemorrhagic shock. A prospective, randomized study. Animal laboratory at a university medical clinic. Seventeen Sprague-Dawley rats weighing 250-400 g. The rats underwent median laparotomy and exteriorization of an ileal loop f...
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To determine the presence of activated complement components in eyes affected by diabetic retinopathy. Eyes of 50 deceased donors with diabetic retinopathy and of 10 nondiabetic subjects with uveal melanoma (n = 6) or phthisical eyes (n = 4), as well as eyes of 16 deceased donors without diabetic retinopathy were subjected to immunohistochemical st...