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Accueil > Bibliographie > Extracellular superoxide dismutase in insects : characterization, function (...)

Extracellular superoxide dismutase in insects : (...)

J Biol Chem. 2011 Sep ; [Epub ahead of print]
Extracellular superoxide dismutase in insects : characterization, function and interspecific variation in parasitoid wasps’ venom.
Colinet D, Cazes D, Belghazi M, Gatti JL, Poirie M.

Endoparasitoid wasps inject venom proteins with their eggs to protect them from the host immune response and ensure successful parasitism. Here, we report identification of intracellular (SOD1) and extracellular (SOD3) Cu,Zn superoxide dismutase transcripts in the venom apparatus of two Leptopilina species, parasitoids of Drosophila. Leptopilina SODs show sequence and structure similarity to human SODs, but phylogenetic analyses indicate that the extracellular SODs are more related to cytoplasmic vertebrate SODs than to extracellular ones, a feature shared by predicted insect extracellular SODs. We demonstrate that L. boulardi SOD3 (LbSOD3) is indeed secreted and active as monomeric glycosylated forms in venom. Our results also evidence quantitative variation in SOD3 venom contents between closely related parasitoid species since sod3 is 100-fold less expressed in L. heterotoma venom apparatus and no protein and SOD activity are detected in its venom. Leptopilina recombinant SOD3s as well as a mammalian SOD in vitro inhibit the Drosophila phenoloxidase activity in a dose-dependent manner, demonstrating that SODs may interfere with the Drosophila melanization process and therefore with production of cytotoxic compounds. Although the recombinant LbSOD3 quantity needed to observe this effect precludes a systemic effect of the wasp venom SOD3, it is still consistent with a local action at oviposition. This work provides the first demonstration that insect extracellular SODs are indeed secreted and active in an insect fluid and can be used as virulence factors to counteract the host immune response, a strategy largely used by bacterial and fungal pathogens but also protozoan parasites during infection.

PubMed

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