Special Issue "Protein Toxins as Proteases"

Guest Editor
Prof. Dr. Shin-ichi Miyoshi
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Tsushima-Naka, Okayama, Okayama 700-8530, Japan
Website: http://www.pharm.okayama-u.ac.jp/lab/user/miyoshi.html
E-Mail:
Interests: bacterial protein toxins; pore-forming toxins; cell membrane proteins/receptors; proteolytic enzymes

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

Submission

All manuscripts should be submitted to toxins@mdpi.org with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed Open Access monthly journal published by MDPI.

• metallo-protease
• serine protease
• bacterial protein toxin
• hemorrhagic toxin
• inhibitor
• molecular tool

Type of Paper: Review
Title: Snake Venom Metalloproteases: The Toxins with ADAM Structure
Authors: Satohiko Araki, Kazuma Onizuka and Hitoshi Sawada
Affiliation: Graduate School of Science, Marine Biological Laboratory, Nagoya University, Toba, Mie 517-0004, Japan; E-mail: saraki@bio.nagoya-u.ac.jp
Abstract: Snake venom metalloproteases (SVMPs) are the responsible toxins for the hemorrhage induced by snake venom. They belong to the ADAM (A Disintegrin And Metalloprotease) family, which is involved in the cell moving, proliferation, inflammation, malignant transformation, etc. The structure and mechanism of SVMPs present many suggestions to understand the life mechanisms correlated with ADAMs. We introduce SVMPs in the light of the structures which are recently clarified.

Type of Paper: Review
Title: Pathological Effects of Bacterial Proteases on the Gastro-intestinal Tract
Author: John Holton
Affiliation: Centre for Infectious Diseases and International Health, Windeyer Institute of Medical Sciences, University College London, 46 Cleveland Street, London, W1T 4JF, UK; E-Mail: john.holton@uclh.nhs.uk
Abstract: The gastrointestinal tract has a rich and largely unexplored microflora, although the complex ecology is being better defined by metagonomic and metabolomic studies. Many of the microbial components of this ecosystem produce proteases, which are either secreted into the environment or expressed as surface outer membrane proteins. These bacterial proteases can cause direct pathological damage to the gastrointestinal epithelial cells or indirectly, auto-proteolytic activity of some proteins, can lead to the expression of toxic activity of the protein. Additionally a key regulatory signal pathway in the gastrointestinal tract – protease activated receptors (PARs) which control secretory and permeability effects may be affected by bacterial proteases. The recognition of bacterial proteases having patho-physiological effects on gastrointestinal function could led to the development of novel therapeutic agents that can inhibit or modulate these adverse outcomes. This review will focus on the gastrointestinal bacterial proteases affecting intestinal physiology and inducing pathological changes which lead to disease.

Type of Paper: Review
Title: Serine Protease Autotransporters of Enterobacteriaceae (SPATEs): Biogenesis and Function.
Author: Nathalie Dautin
Affiliation: Department of Biology, The Catholic University of America, 620 Michigan Avenue, N.E., Washington DC, 20064, USA; E-Mail: dautin@cua.edu
Abstract: Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) constitute a large family of proteases secreted by pathogenic strains of Escherichia coli as well as Shigella species. SPATEs exhibit two distinct proteolytic activities. First, a C-terminal catalytic site triggers an intra-molecular cleavage that releases the N-terminal portion of those proteins in the extracellular medium. Second, the secreted, N-terminal domains of the SPATEs are themselves proteases, each containing a canonical serine-protease site. Those secreted proteases are also toxins, eliciting various effects on mammalian cells. Here, we discuss the biogenesis of SPATEs and their function as toxins.

Type of Paper: Review
Title: The Zinc-Dependent Protease Activity of the Botulinum Neurotoxins
Author: Frank J. Lebeda
Affiliation: Deputy Director, Research Area Directorate 2, Combat Casualty Care Research Program, US Army Medical Research and Materiel Command, 504 Scott Street, Fort Detrick, MD 21702-5012, USA; E-Mail: Frank.Lebeda@us.army.mil
Abstract: The botulinum neurotoxins (BoNTs) are some of the most toxic proteins known and are the causative agents of botulism. The overall mechanism of action of the seven immunological distinct serotypes (A-G) is similar. Following ingestion, intramuscular or intravenous injection the neurotoxin binds to peripheral cholinergic nerves, enters their presynaptic terminals and specifically cleaves one or more SNARE proteins. These homologous neurotoxins have been exploited as pharmacologic tools in understanding the role of these highly conserved SNAREs in vertebrates which are involved in neurally evoked, Ca-dependent release of neurotransmitter from synaptic vesicles. This article focuses on the metalloproteolytic enzymatic activities of these neurotoxins using cell-free assays, their kinetic properties, the search for potent active-site inhibitors and the phenomenon of persistence of toxicity that is the hallmark of the A serotype.

Type of Paper: Review
Title: Proteases as Insecticidal Agents
Authors: Robert L. Harrison ¹ and Bryony C. Bonning ²
Affiliation: ¹ USDA, ARS, Beltsville, MD 20705, USA; E-Mail: Robert.L.Harrison@ars.usda.gov
² Department of Entomology, Iowa State University, Ames, IA 50011, USA; E-Mail: bbonning@iastate.edu
Abstract: Proteases from a variety of sources including viruses, bacteria, fungi, plants, and insects, have been shown to have toxicity towards insects. Some of these insecticidal proteases evolved as venom components, herbivore resistance factors, or microbial pathogenicity factors, while others that function in insect development or digestion exert an insecticidal effect when over-expressed from genetically engineered plants or viruses. The majority of insecticidal proteases are cysteine proteases, and sites of toxic activity range from the insect midgut to the hemocoel (body cavity) to the cuticle. This review will describe insecticidal proteases and their evaluation as potential pesticides, with a special emphasis on the use of proteases to enhance the insecticidal efficacy of baculoviruses.

Type of Paper: Review
Title: Host-Toxin Interactions Involving EspC and Pet, Two Serine Protease Autotransporters of the Enterobacteriaceae
Authors: Fernando Navarro-Garcia ¹, Michael Sonnested ¹ and Ken Teter ²
Affiliation: ¹ Department of Cell Biology, Centro de Investigación y de Estudios Avanzados (CINVESTAV-IPN), Ap. Postal 14-740, 07000 Mexico DF, Mexico
² Department of Molecular Biology and Microbiology, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, USA; E-Mail: kteter@mail.ucf.edu
Abstract: 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 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.

Type of Paper: Review
Title: Prothrombinase-Like Enzyme Complex in Australian Elapid Venom
Authors: Mettine H.A. Bos ^1,2 and Rodney M. Camire ^1,2
Affiliation: ¹ Department of Pediatrics, Division of Hematology, The Children’s Hospital of Philadelphia, PA 19104, USA
² School of Medicine, The University of Pennsylvania , Philadelphia, PA 19104, USA; E-Mail: rcamire@mail.med.upenn.edu
Abstract: The macromolecular enzyme complex prothrombinase serves an indispensable role in blood coagulation as it catalyzes the conversion of prothrombin to thrombin, the latter being 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. Their venom is among the most toxic in the world and consists of 20-40% of this prothrombinase-like complex, which is composed of the protein cofactor factor Va and a serine protease factor Xa-like subunit. This review will give an overview of the identification and characterization of the venom prothrombinase complex and will discuss the biochemical rationale for its powerful procoagulant nature that contributes to the potent hemostatic toxicity of the elapid venom.

Type of Paper: Review
Title: Utilization of microRNA to Neutralize Class I Bacterial and Viral Toxins
Authors: Omar Bagasra ¹ and Donald Gene Pace ²
Affiliation: ¹ South Carolina Center for Biotechnology, Claflin University, Orangeburg, SC 29115, USA; E-Mail: obagasra@claflin.edu
² Department of English and Foreign Languages, Claflin University, Orangeburg, SC 29115, USA; E-Mail: dpace@claflin.edu
Abstract: Biological weapons are of significant concern for the US military and the world community. In a November, 2003 report from the CIA, “The Darker Bioweapons Future”, panelists of life science experts advised that “advances in biotechnology, coupled with the difficulty in detecting nefarious biological activity, have the potential to create a much more dangerous biological warfare threat.” It will be very difficult to predict the type and nature of pathogens that could be used as bioweapons. It could be a chimera smallpox/cowpox virus or a innocuous virus or bacterial carrying anthrax/tetanus toxins or hemorrhagic genes weaving a friendly outfit. If traditional methods of vaccination are utilized, it may take years before an appropriate vaccine or therapy could be developed. However, we believe that a custom designed RNA-based vector that will carry the information for a wide range of antitoxins (i.e., poxviruses, Ebola, plague, anthrax etc) that could express specific RNAi or microRNAs. This sort of post-exposure therapy can be mass-produced in weeks, after the evidence of a ‘new recombinant or chimeric’ illness becomes available. The goal of this review article is to present formulas for develop novel post-exposure therapy against the potential viral or bacterial pathogens/toxins utilizing miRNA technology that can be utilized as neutralizing agents against bio-weapons including either wild-type or binary engineered forms of smallpox (Variola major), hemorrhagic viruses (filoviruses, especially ebola), anthrax (Bacillus anthracis), and plague (Yersinia pestis) by RNA-interference (RNAi) or miRNAs. The propose to utilize vectors that will express small interfering RNAs (siRNAs) or miRNAs in the host cells that would target the viral or bacterial genes/plasmids responsible for the virulence and pathogenecity.

Type of paper: Review
Title: Secreted Toxins of Bioinsecticidal Bacterium Photorhabdus luminescens
Authors: Athina Rodou, Dennis O. Ankrah and Christos Stathopoulos
Affiliation: Department of Biological Sciences, California State Polytechnic University, Pomona, CA 91768, USA; E-Mail: stathopoulos@csupomona.edu
Abstract: 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 bioinsecticides, as well as an emerging human pathogen. Due to these features, the study of extracellular toxins of Photorhabdus luminescens is of great importance. Herein, we review the latest information on the secreted exotoxins of this pathogen.