# Understanding the Functional Roles of Newly Identified Serine ‘Orphan’ Proteases and Two Chymotrypsins in the Aedes aegypti Midgut

> **NIH NIH SC3** · SAN JOSE STATE UNIVERSITY · 2023 · $109,875

## Abstract

Understanding the Functional Roles of Newly Identified Serine `Orphan' Proteases and Two
Chymotrypsins in the Aedes aegypti Midgut
Project Summary/Abstract
The female Aedes aegypti mosquito completely relies on human blood as its main source of nutrients. A single
female Ae. aegypti mosquito can lay up to 200 eggs from a single blood meal, and the digestion process is
highly dependent on midgut proteolytic enzymes. In vivo studies of four abundant midgut proteases have
revealed the importance of only three on maximal fecundity. However, RNAi knockdown studies of all three at
once did not have an overall synergistic effect indicating the involvement of other midgut proteases. Indeed,
mRNA transcripts of five new serine 'orphan' proteases have been identified, but their physiological roles in this
process have not been studied in vivo or in vitro making it unknown how much they contribute to overall
fecundity. In addition, the exact role in digestion and overall fecundity of two chymotrypsin-like proteases
remains unclear. We hypothesize that the orphan proteolytic and the chymotrypsin-like enzymes play important
functional roles in the blood meal digestion process. Because the functions of these proteases are novel in
mosquitoes, they will bear broadly on the study of a crucial model organism in vector biology. This proposal will
focus on elucidating the physiological roles of these serine proteases using RNAi technology, in vivo and in
vitro midgut proteolytic activity assays, fecundity studies (Aim 1), recombinant protein expression and
purification for in vitro kinetic and substrate specificity assays, as well as mutational and structural
determination using crystallography (Aim 2). Overall, the work will lead to complete understanding of the role
and specificity of all known mosquito midgut proteases in the blood meal digestion process and may lead to
the development of a potential novel mosquito (vector) control strategy. This is crucial because the mosquito is
able to transmit several viral pathogens during blood feeding, and if blood meal digestion is interrupted, the
mosquito will not lay eggs minimizing the mosquito population, and in turn minimize pathogen transmission.
Furthermore, the information gained from this work may be applied to other vector mosquito species and other
blood feeding insect vectors that heavily rely on midgut proteolytic enzymes for digestion.

## Key facts

- **NIH application ID:** 10598048
- **Project number:** 5SC3GM116681-08
- **Recipient organization:** SAN JOSE STATE UNIVERSITY
- **Principal Investigator:** ALBERTO A RASCON
- **Activity code:** SC3 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $109,875
- **Award type:** 5
- **Project period:** 2016-02-22 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10598048

## Citation

> US National Institutes of Health, RePORTER application 10598048, Understanding the Functional Roles of Newly Identified Serine ‘Orphan’ Proteases and Two Chymotrypsins in the Aedes aegypti Midgut (5SC3GM116681-08). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10598048. Licensed CC0.

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