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Serpin-5 regulates prophenoloxidase activation and antimicrobial peptide pathways in the silkworm, Bombyx mori

Junlan Li1, Li Ma1, Zhe Lin2

  • 1Department of Entomology, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China.

Insect Biochemistry and Molecular Biology
|April 17, 2016
PubMed

Insights

Silkworm serpin-5 (BmSpn-5) regulates key immune pathways by inhibiting serine proteases involved in prophenoloxidase (PPO) activation and antimicrobial peptide production, crucial for insect defense.

Area of Science:

  • Insect immunology
  • Biochemistry
  • Molecular biology

Background:

  • The prophenoloxidase (PPO) and Toll pathways are vital insect immune responses to microbial infections.
  • Extracellular serine protease cascades mediate these pathways, with serpins acting as negative regulators.

Purpose of the Study:

  • To characterize silkworm serpin-5 (BmSpn-5) and its role in insect immunity.
  • To elucidate the regulatory mechanisms of PPO activation and Toll pathway signaling.

Main Methods:

  • Quantitative analysis of BmSpn-5 mRNA abundance post-infection.
  • Assessing the impact of recombinant BmSpn-5 on antimicrobial peptides (AMPs) and melanization.
  • Immunoaffinity purification and mass spectrometry to identify BmSpn-5 interacting proteins.

Main Results:

  • BmSpn-5 mRNA levels significantly increased in silkworm fat bodies after bacterial infection.
  • Recombinant BmSpn-5 reduced AMP expression and inhibited PPO activation and melanization.
  • BmSpn-5 forms complexes with silkworm clip domain serine proteases BmHP6 and BmSP21.

Conclusions:

  • BmSpn-5 acts as a crucial negative regulator in insect immune serine protease cascades.
  • BmHP6 and BmSP21 are identified as cognate proteases of BmSpn-5, essential for Toll and PPO pathway activation.
  • This study enhances understanding of PPO activation pathways and serpin-mediated regulation in insects.
Keywords:
Antimicrobial peptideProphenoloxidaseSerpinSilkworm

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