Distinct melanization pathways in the mosquito Aedes aegypti

Area of Science:

• Entomology
• Immunology
• Biochemistry

Background:

• Serine protease cascades are crucial for blood coagulation and immunity in arthropods, regulating vital processes like melanization for defense and healing.
• The intricate mechanisms governing arthropod melanization pathways remain incompletely understood.
• Mosquitoes, as disease vectors, rely on melanization for immune responses, making pathway elucidation critical.

Purpose of the Study:

• To elucidate the distinct serine protease-driven pathways regulating melanization in the mosquito *Aedes aegypti*.
• To identify the specific serine proteases and serpins involved in immune and tissue melanization.
• To investigate the role of these proteases and serpins in activating the Toll pathway.

Main Methods:

• Protease and serpin identification and characterization in *Aedes aegypti*.
• Analysis of prophenoloxidase cleavage during immune responses.
• Investigation of melanotic tumor formation and Toll pathway activation.

Main Results:

• Identified two distinct melanization pathways mediated by different serine protease and serpin modules.
• Demonstrated that Immune Melanization Proteases (IMP-1, IMP-2) and Serpin-1 control hemolymph prophenoloxidase cleavage for anti-malarial immunity.
• Showed that Tissue Melanization Protease (CLIPB8), IMP-1, and Serpin-2 regulate tissue melanization, including melanotic tumors.
• Revealed roles for CLIPB5 and CLIPB29 in Toll pathway activation, with Serpin-2 implicated in infection-independent activation.

Conclusions:

• Mosquito melanization and Toll pathway activation involve complex, modular serine protease systems.
• Distinct protease-serpin interactions orchestrate both immune defense and tissue repair processes.
• This study provides a foundational understanding of intricate immune regulatory networks in mosquitoes.