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Manduca sexta hemolymph protease HP6 functions in innate immune responses
Author(s) -
An Chunju,
Ishibashi Jun,
Jiang Haobo,
Kanost Michael
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a649-a
Subject(s) - manduca sexta , serine protease , manduca , hemolymph , prophenoloxidase , protease , biology , cecropin , proteases , innate immune system , zymogen , serine , biochemistry , mutant , antimicrobial peptides , microbiology and biotechnology , enzyme , peptide , gene , insect , ecology , receptor
We have identified 25 serine proteases in hemolymph of the tobacco hornworm, Manduca sexta . Hemolymph protease 6 (HP6), composed of an amino‐terminal clip domain and a carboxyl‐terminal protease domain, is most similar to Drosophila Persephone, a clip‐domain protease leading to Toll pathway activation and induced synthesis of antifungal peptide drosomycin upon infection. HP6 mRNA is expressed constitutively in the fat body and hemocytes. Exposure to bacteria stimulated the cleavage of proHP6 zymogen in plasma to yield its active form. We expressed recombinant proHP6 and a mutant proHP6(S287A) in which the catalytic triad serine was replaced with alanine. Addition of purified recombinant proHP6 to plasma resulted in significantly elevated proPO activation, but proHP6(S287A) did not. This result suggests that HP6 may participate in the proPO activation cascade. Furthermore, injection of proHP6 into the larvae resulted in elevated mRNA levels for several antimicrobial genes, including attacin, cecropin, lysozyme, gloverin, and moricin, but this did not occur after injection of the proHP6(S287A). This result is consistent with the hypothesis that HP6 functions in a manner similar to its Drosophila ortholog Persephone in activating a Toll pathway in Manduca . Therefore, HP6 may function in more than one immune protease cascade during responses to microbial infection. Supported by NIH GM41247.