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Title: A serpin released by an entomopathogen impairs clot formation in insect defense system
Authors: Toubarro, Duarte
Avila, Mónica M.
Hao, Youjin
Balasubramanian, Natesan
Jing, Yingjun
Montiel, Rafael 
Faria, Tiago Q. 
Brito, Rui M. 
Simões, Nelson 
Issue Date: 2013
Publisher: Public Library of Science
Project: This research was supported by Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT) (PDCT/AGR/AAM/104487/2008) and by FLAD (Proj. 223/2006) accorded to NS; a fellowship from the Regional Government of Ac¸ores (RGA) (M3.1.2/F/005/2007) to MMA; a mobility grant from FCT (Procu 441 Ac. C. Mexico) to NS and RM; a grant from Conacyt-Hidalgo State Government (Fomix-Hgo-2008-C01-97032) to RM. DT received a fellowship from FCT (PDCT/AGR/AAM/104487/2008); NB from RGA (M3.1.7/F/009A/2009) and YJ from RGA (M112/F/031/2007); Y-JH from FCT (SFRH/BPD/21079/2004). 
Serial title, monograph or event: PLoS ONE
Volume: 8
Issue: 7
Abstract: Steinernema carpocapsae is an entomopathogenic nematode widely used for the control of insect pests due to its virulence, which is mainly attributed to the ability the parasitic stage has to overcome insect defences. To identify the mechanisms underlying such a characteristic, we studied a novel serpin-like inhibitor (sc-srp-6) that was detected in a transcriptome analysis. Recombinant Sc-SRP-6 produced in Escherichia coli had a native fold of serpins belonging to the α-1-peptidase family and exhibited inhibitory activity against trypsin and α-chymotrypsin with Ki of 0.42 × 10(-7) M and 1.22 × 10(-7) M, respectively. Functional analysis revealed that Sc-SRP-6 inhibits insect digestive enzymes, thus preventing the hydrolysis of ingested particles. Moreover, Sc-SRP-6 impaired the formation of hard clots at the injury site, a major insect defence mechanism against invasive pathogens. Sc-SRP-6 does not prevent the formation of clot fibres and the activation of prophenoloxidases but impairs the incorporation of the melanin into the clot. Binding assays showed a complex formation between Sc-SRP-6 and three proteins in the hemolymph of lepidopteran required for clotting, apolipophorin, hexamerin and trypsin-like, although the catalytic inhibition occurred exclusively in trypsin-like. This data allowed the conclusion that Sc-SRP-6 promotes nematode virulence by inhibiting insect gut juices and by impairing immune clot reaction.
ISSN: 1932-6203
DOI: 10.1371/journal.pone.0069161
Rights: openAccess
Appears in Collections:I&D CNC - Artigos em Revistas Internacionais

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