title: Trypsin- and Chymotrypsin-like serine proteases in schistosoma mansoni-- 'the undiscovered country'.
abstract: BACKGROUND
  Blood flukes (Schistosoma spp.) are parasites that can survive for years or decades in the vasculature of permissive mammalian hosts, including humans. Proteolytic enzymes (proteases) are crucial for successful parasitism, including aspects of invasion, maturation and reproduction. Most attention has focused on the 'cercarial elastase' serine proteases that facilitate skin invasion by infective schistosome larvae, and the cysteine and aspartic proteases that worms use to digest the blood meal. Apart from the cercarial elastases, information regarding other S. mansoni serine proteases (SmSPs) is limited. To address this, we investigated SmSPs using genomic, transcriptomic, phylogenetic and functional proteomic approaches.
  
  
  RESULTS
  Genes encoding five distinct SmSPs, termed SmSP1 - SmSP5, some of which comprise disparate protein domains, were retrieved from the S. mansoni genome database and annotated. Reverse transcription quantitative PCR (RT- qPCR) in various schistosome developmental stages indicated complex expression patterns for SmSPs, including their constituent protein domains. SmSP2 stood apart as being massively expressed in schistosomula and adult stages. Phylogenetic analysis segregated SmSPs into diverse clusters of family S1 proteases. SmSP1 to SmSP4 are trypsin-like proteases, whereas SmSP5 is chymotrypsin-like. In agreement, trypsin-like activities were shown to predominate in eggs, schistosomula and adults using peptidyl fluorogenic substrates. SmSP5 is particularly novel in the phylogenetics of family S1 schistosome proteases, as it is part of a cluster of sequences that fill a gap between the highly divergent cercarial elastases and other family S1 proteases.
  
  
  CONCLUSIONS
  Our series of post-genomics analyses clarifies the complexity of schistosome family S1 serine proteases and highlights their interrelationships, including the cercarial elastases and, not least, the identification of a 'missing-link' protease cluster, represented by SmSP5. A framework is now in place to guide the characterization of individual proteases, their stage-specific expression and their contributions to parasitism, in particular, their possible modulation of host physiology.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Horn
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Pavla
authors.initials: P
authors.lastname: Fajtová
authors.affiliation: Center for Discovery and Innovation in Parasitic Diseases, Department of Pathology, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Liliana
authors.initials: L
authors.lastname: Rojo Arreola
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic; Department of Parasitology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Ulrychová
authors.affiliation: Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic.
authors.forename: Pavla
authors.initials: P
authors.lastname: Bartošová-Sojková
authors.affiliation: Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic; Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Project Group Bioresources, Gießen, Germany.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Franta
authors.affiliation: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, United Kingdom.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Protasio
authors.affiliation: Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Opavský
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Vondrášek
authors.affiliation: Center for Discovery and Innovation in Parasitic Diseases, Department of Pathology, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: James H
authors.initials: JH
authors.lastname: McKerrow
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Michael
authors.initials: M
authors.lastname: Mareš
authors.affiliation: Center for Discovery and Innovation in Parasitic Diseases, Department of Pathology, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Conor R
authors.initials: CR
authors.lastname: Caffrey
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic; Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Dvořák
mesh_terms: D000818:Animals; D001671:Biochemistry; D016000:Cluster Analysis; D023281:Genomics; D008969:Molecular Sequence Data; D010802:Phylogeny; D040901:Proteomics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012550:Schistosoma mansoni / Q000201:enzymology* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D057057:Serine Proteases / Q000235:genetics* / Q000378:metabolism*; D059467:Transcriptome
chemical_list: D057057:Serine Proteases