http://www.mdpi.com/journal/toxins/special_issues/toxins-proteases/ Dear Colleagues, Proteases are enzymes that hydrolyze a peptide bond in proteins and peptides. The enzymes are essential for the homeostatic control in both eukaryotes and prokaryotes; however, they produced by pathogenic microorganisms occasionally act as toxic factors to the host. Although proteases are classified into four groups, aspartic, cysteine, serine and metallo-proteases, many of the toxic proteases are metallo-proteases containing a zinc (II) ion in the catalytic center. The progress in molecular biology has provided much information on the DNA-derived amino acid sequences for metallo-proteases and has revealed the consensus sequence His-Glu-X-X-His as the zinc-binding motif. This motif was found in clostridial neurotoxins, Bacteroides fragilis enterotoxin (Fragilysin) and Bacillus anthracis lethal factor. These bacterial toxins show remarkably specific proteolytic actions toward a target host protein. For instance, clostridial neurotoxins can cleave the protein components of the neuroexocytosis machinery, which leads to the blockade of neurotransmitter release and consequent muscle paralysis. Hemorrhagic toxins from snake venoms are also metallo-protease. A novel cytotoxin from some enterohemorrhagic Escherichia coli strains consists of one A subunit and five B subunits. The A subunit is a subtilase-like serine protease. This special issue deals with various aspects of protein toxins acting as proteases, which include biochemical and pathological properties, molecular modes of the toxic actions, the development of inhibitors to prevent or interrupt the toxic actions, and application to the cell biology. Prof. Dr. Shin-ichi Miyoshi Guest Editor{snippet name="submission_info"} http://www.mdpi.com/2072-6651/2/6/1554/ The macromolecular enzyme complex prothrombinase serves an indispensable role in blood coagulation as it catalyzes the conversion of prothrombin to thrombin, a key regulatory enzyme in the formation of a blood clot. Interestingly, a virtually identical enzyme complex is found in the venom of some Australian elapid snakes, which is composed of a cofactor factor Va-component and a serine protease factor Xa-like subunit. This review will provide an overview of the identification and characterization of the venom prothrombinase complex and will discuss the rationale for its powerful procoagulant nature responsible for the potent hemostatic toxicity of the elapid venom. http://www.mdpi.com/2072-6651/2/6/1554/ Fri, 18 Jun 2010 00:00:00 CEST Toxins 2010-06-18 2 6 Review 1554 1567 2072-6651 Procoagulant Adaptation of a Blood Coagulation Prothrombinase-like Enzyme Complex in Australian Elapid Venom 2010-06-18 doi: 10.3390/toxins2061554 Bos Camire http://www.mdpi.com/2072-6651/2/6/1250/ Photorhabdus luminescens is a nematode-symbiotic, gram negative, bioluminescent bacterium, belonging to the family of Enterobacteriaceae.Recent studies show the importance of this bacterium as an alternative source of insecticides, as well as an emerging human pathogen. Various toxins have been identified and characterized in this bacterium. These toxins are classified into four major groups: the toxin complexes (Tcs), the Photorhabdus insect related (Pir) proteins, the “makes caterpillars floppy” (Mcf) toxins and the Photorhabdus virulence cassettes (PVC); the mechanisms however of toxin secretion are not fully elucidated. Using bioinformatics analysis and comparison against the components of known secretion systems, multiple copies of components of all known secretion systems, except the ones composing a type IV secretion system, were identified throughout the entire genome of the bacterium. This indicates that Photorhabdus luminescens has all the necessary means for the secretion of virulence factors, thus it is capable of establishing a microbial infection. http://www.mdpi.com/2072-6651/2/6/1250/ Tue, 01 Jun 2010 00:00:00 CEST Toxins 2010-06-01 2 6 Review 1250 1264 2072-6651 Toxins and Secretion Systems of Photorhabdus luminescens 2010-06-01 doi: 10.3390/toxins2061250 Rodou Ankrah Stathopoulos http://www.mdpi.com/2072-6651/2/6/1179/ Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) constitute a large family of proteases secreted by Escherichia coli and Shigella. SPATEs exhibit two distinct proteolytic activities. First, a C-terminal catalytic site triggers an intra-molecular cleavage that releases the N-terminal portion of these proteins in the extracellular medium. Second, the secreted N-terminal domains of SPATEs are themselves proteases; each contains a canonical serine-protease catalytic site. Some of these secreted proteases are toxins, eliciting various effects on mammalian cells. Here, we discuss the biogenesis of SPATEs and their function as toxins. http://www.mdpi.com/2072-6651/2/6/1179/ Fri, 28 May 2010 00:00:00 CEST Toxins 2010-05-28 2 6 Review 1179 1206 2072-6651 Serine Protease Autotransporters of Enterobacteriaceae (SPATEs): Biogenesis and Function 2010-05-28 doi: 10.3390/toxins2061179 Dautin http://www.mdpi.com/2072-6651/2/5/1148/ Staphylococcus aureus is an important pathogen of humans and livestock. It causes a diverse array of diseases, ranging from relatively harmless localized skin infections to life-threatening systemic conditions. Among multiple virulence factors, staphylococci secrete several exotoxins directly associated with particular disease symptoms. These include toxic shock syndrome toxin 1 (TSST-1), enterotoxins, and exfoliative toxins (ETs). The latter are particularly interesting as the sole agents responsible for staphylococcal scalded skin syndrome (SSSS), a disease predominantly affecting infants and characterized by the loss of superficial skin layers, dehydration, and secondary infections. The molecular basis of the clinical symptoms of SSSS is well understood. ETs are serine proteases with high substrate specificity, which selectively recognize and hydrolyze desmosomal proteins in the skin. The fascinating road leading to the discovery of ETs as the agents responsible for SSSS and the characterization of the molecular mechanism of their action, including recent advances in the field, are reviewed in this article. http://www.mdpi.com/2072-6651/2/5/1148/ Tue, 25 May 2010 00:00:00 CEST Toxins 2010-05-25 2 5 Review 1148 1165 2072-6651 Exfoliative Toxins of Staphylococcus aureus 2010-05-25 doi: 10.3390/toxins2051148 Bukowski Wladyka Dubin http://www.mdpi.com/2072-6651/2/5/1134/ EspC and Pet are toxins secreted by the diarrheagenic enteropathogenic and enteroaggregative Escherichia coli pathotypes, respectively. Both toxins have a molecular mass around 110 kDa and belong to the same protein family called Serine Protease Autotransporters of the Enterobacteriaceae (SPATE). Furthermore, both toxins act within the cytosol of intoxicated epithelial cells to disrupt the architecture of the actin cytoskeleton. This cytopathic and enterotoxic effect results from toxin cleavage of the actin-binding protein fodrin, although the two toxins recognize different cleavage sites on fodrin. EspC and Pet also have dramatically different mechanisms of entering the target cell which appear dependent upon the E. coli pathotype. In this review, we compare/contrast EspC and Pet in regards to their mode of delivery into the target cell, their effects on fodrin and the actin cytoskeleton, and their possible effects on the physiology of the intestinal epithelial cell. http://www.mdpi.com/2072-6651/2/5/1134/ Fri, 14 May 2010 00:00:00 CEST Toxins 2010-05-14 2 5 Review 1134 1147 2072-6651 Host-Toxin Interactions Involving EspC and Pet, Two Serine Protease Autotransporters of the Enterobacteriaceae 2010-05-14 doi: 10.3390/toxins2051134 Navarro-Garcia Sonnested Teter http://www.mdpi.com/2072-6651/2/5/1038/ Anthrax is caused by the gram-positive bacterium Bacillus anthracis. The pathogenesis of this disease is dependent on the presence of two binary toxins, edema toxin (EdTx) and lethal toxin (LeTx). LeTx, the major virulence factor contributing to anthrax, contains the effector moiety lethal factor (LF), a zinc-dependent metalloprotease specific for targeting mitogen-activated protein kinase kinases. This review will focus on the protease-specific activity and function of LF, and will include a discussion on the implications and consequences of this activity, both in terms of anthrax disease, and how this activity can be exploited to gain insight into other pathologic conditions. http://www.mdpi.com/2072-6651/2/5/1038/ Tue, 11 May 2010 00:00:00 CEST Toxins 2010-05-11 2 5 Review 1038 1053 2072-6651 Consequences and Utility of the Zinc-Dependent Metalloprotease Activity of Anthrax Lethal Toxin 2010-05-11 doi: 10.3390/toxins2051038 Bromberg-White Lee Duesbery http://www.mdpi.com/2072-6651/2/5/978/ The botulinum neurotoxins (BoNT, serotypes A-G) are some of the most toxic proteins known and are the causative agents of botulism. Following exposure, the neurotoxin binds and enters peripheral cholinergic nerve endings and specifically and selectively cleaves one or more SNARE proteins to produce flaccid paralysis. This review centers on the kinetics of the Zn-dependent proteolytic activities of these neurotoxins, and briefly describes inhibitors, activators and factors underlying persistence of toxin action. Some of the structural, enzymatic and inhibitor data that are discussed here are available at the botulinum neurotoxin resource, BotDB (http://botdb.abcc.ncifcrf.gov). http://www.mdpi.com/2072-6651/2/5/978/ Fri, 07 May 2010 00:00:00 CEST Toxins 2010-05-07 2 5 Review 978 997 2072-6651 The Zinc-Dependent Protease Activity of the Botulinum Neurotoxins 2010-05-07 doi: 10.3390/toxins2050978 Lebeda Cer Mudunuri Stephens Singh Adler http://www.mdpi.com/2072-6651/2/5/963/ Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD) in Multifunctional Autoprocessing RTX-like (MARTX) and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6), which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins. http://www.mdpi.com/2072-6651/2/5/963/ Thu, 06 May 2010 00:00:00 CEST Toxins 2010-05-06 2 5 Review 963 977 2072-6651 Autoproteolytic Activation of Bacterial Toxins 2010-05-06 doi: 10.3390/toxins2050963 Shen http://www.mdpi.com/2072-6651/2/5/935/ Proteases from a variety of sources (viruses, bacteria, fungi, plants, and insects) have toxicity towards insects. Some of these insecticidal proteases evolved as venom components, herbivore resistance factors, or microbial pathogenicity factors, while other proteases play roles in insect development or digestion, but exert an insecticidal effect when over-expressed from genetically engineered plants or microbial pathogens. Many of these proteases are cysteine proteases, although insect-toxic metalloproteases and serine proteases have also been examined. The sites of protease toxic activity range from the insect midgut to the hemocoel (body cavity) to the cuticle. This review discusses these insecticidal proteases along with their evaluation and use as potential pesticides. http://www.mdpi.com/2072-6651/2/5/935/ Wed, 05 May 2010 00:00:00 CEST Toxins 2010-05-05 2 5 Review 935 953 2072-6651 Proteases as Insecticidal Agents 2010-05-05 doi: 10.3390/toxins2050935 Harrison Bonning http://www.mdpi.com/2072-6651/2/3/341/ Porphyromonas gingivalis, the major etiologic agent of chronic periodontitis, produces a broad spectrum of virulence factors, including Arg- and Lys-gingipain cysteine proteinases. In this study, we investigated the capacity of P. gingivalis gingipains to trigger a proinflammatory response in human monocyte-derived macrophages. Both Arg- and Lys-gingipain preparations induced the secretion of TNF-α and IL-8 by macrophages. Stimulation of macrophages with Arg-gingipain A/B preparation at the highest concentration was associated with lower amounts of cytokines detected, a phenomenon likely related to proteolytic degradation. The inflammatory response induced by gingipains was not dependent of their catalytic activity since heat-inactivated preparations were still effective. Stimulating macrophages with gingipain preparations was associated with increased levels of phosphorylated p38α MAPK suggesting its involvement in cell activation. In conclusion, our study brought clear evidence that P. gingivalis Arg- and Lys-gingipains may contribute to the host inflammatory response, a critical factor in periodontitis-associated tissue destruction. http://www.mdpi.com/2072-6651/2/3/341/ Wed, 10 Mar 2010 00:00:00 CET Toxins 2010-03-10 2 3 Article 341 352 2072-6651 Porphyromonas gingivalis Gingipains Trigger a Proinflammatory Response in Human Monocyte-derived Macrophages Through the p38α Mitogen-activated Protein Kinase Signal Transduction Pathway 2010-03-10 doi: 10.3390/toxins2030341 Daniel Grenier Shin-ichi Tanabe