Innexin hemichannel activation by Microplitis bicoloratus ecSOD monopolymer reduces ROS

Area of Science:

• Insect-microbe interactions
• Molecular biology
• Biochemistry

Background:

• Microplitis bicoloratus secretes extracellular superoxide dismutases (ecSODs) to counteract reactive oxygen species (ROS) induced by the Microplitis bicoloratus bracovirus.
• ROS elevation can impair host hemocyte function and parasitoid development.

Purpose of the Study:

• To elucidate the mechanism by which ecSODs reduce ROS.
• To identify the specific domains and motifs responsible for ecSODs' cell membrane binding and hemichannel activity.
• To investigate the role of ecSODs in host-parasitoid interactions.

Main Methods:

• RNA interference (RNAi) for ecSOD silencing in vivo.
• In vitro assays to assess ecSOD-monopolymer binding and hemichannel activity.
• Analysis of specific ecSOD domains (hexapeptide motif, BIg-like domain) and their role in membrane binding and ROS reduction.

Main Results:

• The bacterial transferase hexapeptide (hexapep) motif and bacterial-immunoglobulin-like (BIg-like) domain of ecSODs facilitate ROS reduction by binding to cell membranes and opening hemichannels.
• ecSOD silencing in vivo led to increased ROS in host hemocytes, hindering parasitoid development.
• Specific motifs (hexapep in ecSOD49/58, BIg-like in ecSOD67) are essential for membrane binding, hemichannel opening, and ROS reduction, mediating binding through innexin upregulation and hemichannel stabilization.

Conclusions:

• ecSODs utilize specific motifs to bind host cell membranes, transiently open hemichannels, and reduce ROS, a critical process for parasitoid survival and development.
• The findings reveal a novel mechanism of ROS modulation by insect-secreted proteins.
• This research provides insights for developing novel anti-redox therapies targeting hemichannel function.