Involvement of Mytilins in Mussel Antimicrobial Defense*
- From the ‡Défense et Résistance chez les Invertébrés Marins, IFREMER-CNRS, Université de Montpellier 2, cc 80, 34095 Montpellier, France and §Centre de Biologie Cellulaire, Laboratoire d'Endocrinologie des Annélides, Groupe de Neuroimmunité des Hirudinées, UPRES A CNRS, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France
Abstract
Four cationic peptides were purified from mussel (Mytilus galloprovincialis) hemocytes. A combination of Edman degradation and mass spectrometry of plasma revealed (i) a previously characterized molecule, mytilin B (Charlet, M., Chernysh, S., Philippe, H., Hetrut, C., Hoffmann, J., and Bulet, P. (1996)J. Biol. Chem. 271, 21808–21813) and (ii) three new isoforms, mytilin C, D, and G1. The four molecules exhibited complementary antimicrobial properties. The cDNA sequence coding for the mytilin B precursor was obtained from a hemocyte cDNA library. This precursor contains a putative signal peptide of 22 residues, a processing peptide sequence of 34 amino acids, and a C-terminal extension of 48 residues rich in acidic residues. Distribution of mytilin B mRNA and of the corresponding peptide in various mussel tissues revealed that mytilins are synthesized and stored in a specific hemocyte subtype. Furthermore, in an experimental model of infection, we showed (i) a recruitment of hemocytes containing mytilins toward the injection site within hours following bacterial challenge, (ii) that mytilins probably play a prominent role in killing intracellular bacteria after phagocytosis, and (ii) later an increase of mytilin-like material occurred in the plasma suggesting a secondary systemic role.
Footnotes
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↵* This work was supported in part by the Commission of the European Communities, Agriculture and Fisheries (FAIR) specific RTD program, CT 97-3691. The Défense et Résistance chez les Invertébrés Marins (DRIM) is a Join Research Unit (UMR 5098) funded by IFREMER, CNRS, and Université de Montpellier 2.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed: Dr. Philippe Roch, DRIM-UMR 5098, Université de Montpellier 2, cc 80, Place Eugène Bataillon, 34095 Montpellier, France. Tel.: 33 4 6714 4625; Fax: 33 4 6714 4622; E-mail: proch@ifremer.fr.
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↵2 G. Mitta, P. Roch, and J.-P. Cadoret, manuscript in preparation.
- Abbreviations:
- UPW
-
ultrapure water
- HPLC
-
high pressure liquid chromatography
- MIC
-
minimal inhibitory concentration
- MBC
-
minimal bactericidal concentration
- BSA
-
bovine serum albumin
- PCR
-
polymerase chain reaction
- PBS
-
phosphate-buffered saline
- TBS
-
Tris-buffered saline
- ELISA
-
enzyme-linked immunosorbent assay
-
- Received July 14, 1999.
- Revision received February 1, 2000.
- The American Society for Biochemistry and Molecular Biology, Inc.
