# Function and regulation of two key serine proteases in insect immunity

> **NIH NIH R01** · OKLAHOMA STATE UNIVERSITY STILLWATER · 2022 · $345,504

## Abstract

Project Summary
Extracellular serine proteases and their non-catalytic homologs coordinate key defense mechanisms
in insects. This includes responses of mosquitoes against pathogens and parasites that cause
serious human diseases. Proteolytic cleavage generates active phenoloxidases (POs), thioester
proteins (TEPs), Spätzle and other cytokines. PO catalyzes the production of reactive chemicals to
sequester and kill the invading organisms. TEPs opsonize parasites, targeting them for destruction.
Spätzle and other cytokines trigger intracellular signaling pathways to induce the expression of
antimicrobial peptides and other defense proteins. In insect vectors of human diseases, the protease
networks may be evaded or disrupted by proteins from the intruders. Knowledge of the system
components and their interactions from biochemical model insects such as Manduca sexta is useful
for gaining detailed molecular understanding of fundamental aspects of insect innate immunity,
including these protease cascades and provides basic knowledge that can guide studies of similar
systems in insect disease vectors. We have elucidated a part of the M. sexta protease network that
activates proPO in response to bacteria and fungi. In this network, recognition proteins bind to
microbes and activate the proteases in a cascade mode. We have annotated 193 genes encoding
serine proteases and their homologs, identified 36 of the proteins in larval hemolymph, and acquired
data indicating that some of them play critical roles in immune signal transduction. Based on the
molecular probes, purified proteins and working experience, we propose to investigate two critical
steps of the protease network, which are conserved in dipteran species, by combining hemolymph
fractionation, recombinant protein production and processing, sequence and expression information,
and state-of-the-art mass spectrometry. The specific aims of this project are to: 1) characterize the
system initiation by examining interactions of peptidoglycans, two recognition proteins, and
hemolymph protease-14 precursor (proHP14) at the domain level; 2) identify 1−2 proHP6-activating
proteases and elucidate their activation mechanisms. New knowledge gained in this project will
improve understanding of insect immunity at a biochemical level and stimulate related research in
vector species.

## Key facts

- **NIH application ID:** 10246410
- **Project number:** 5R01GM058634-18
- **Recipient organization:** OKLAHOMA STATE UNIVERSITY STILLWATER
- **Principal Investigator:** HAOBO JIANG
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $345,504
- **Award type:** 5
- **Project period:** 1999-03-01 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10246410

## Citation

> US National Institutes of Health, RePORTER application 10246410, Function and regulation of two key serine proteases in insect immunity (5R01GM058634-18). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10246410. Licensed CC0.

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