The IMD pathway regulates lysozyme-like proteins (LLPs) in the silkmoth Antheraea mylitta.

Lysozyme-like proteins (LLPs) are members of the glycoside hydrolase family 22 (CAZY GH22). Unlike conventional c-type lysozymes (EC 3.2.1.17), LLPs lack specific catalytic amino acid residues essential for muramidase activity. Previous reports indicated upregulation of LLPs upon bacterial infection in the wild silkworm, Antheraea mylitta as well as in the domesticated silkworm, Bombyx mori. In the present work, we studied the signaling pathways mediating the production of LLPs using RNA interference-mediated knockdown of Spätzle, Relish and STAT, the key regulators of Toll, IMD (Immune deficiency) and JAK/STAT pathways, respectively. We observed that knockdown of the Relish variant RD1 resulted in reduced expression levels of the ALLP1. We also showed that recombinant LLP has antiviral activity. We infer that LLPs showing both antibacterial and antiviral activity are regulated by the conventional IMD pathway in the silkmoths.

Epoxide hydrolase activities and epoxy fatty acids in the mosquito Culex quinquefasciatus.

Culex mosquitoes have emerged as important model organisms for mosquito biology, and are disease vectors for multiple mosquito-borne pathogens, including West Nile virus. We characterized epoxide hydrolase activities in the mosquito Culex quinquefasciatus, which suggested multiple forms of epoxide hydrolases were present. We found EH activities on epoxy eicosatrienoic acids (EETs). EETs and other eicosanoids are well-established lipid signaling molecules in vertebrates. We showed EETs can be synthesized in vitro from arachidonic acids by mosquito lysate, and EETs were also detected in vivo both in larvae and adult mosquitoes by LC-MS/MS. The EH activities on EETs can be induced by blood feeding, and the highest activity was observed in the midgut of female mosquitoes. The enzyme activities on EETs can be inhibited by urea-based inhibitors designed for mammalian soluble epoxide hydrolases (sEH). The sEH inhibitors have been shown to play diverse biological roles in mammalian systems, and they can be useful tools to study the function of EETs in mosquitoes. Besides juvenile hormone metabolism and detoxification, insect epoxide hydrolases may also play a role in regulating lipid signaling molecules, such as EETs and other epoxy fatty acids, synthesized in vivo or obtained from blood feeding by female mosquitoes.