An extracellular serine protease network coordinates key mechanisms of insect defense against microbial infection. Proteolytic activation of prophenoloxidase (PPO) generates phenoloxidase that catalyzes the production of reactive compounds to sequester and kill invading pathogens and parasites. Proteolytic processing of sp?tzle precursor triggers the Toll pathway, which induces the synthesis of antimicrobial peptides and other defense proteins. In insect vectors of human diseases, initiation and regulation of these protease systems may be disrupted by proteins from the intruders. Knowledge of such protein interactions from biochemical model insects such as Manduca sexta will be useful for understanding and manipulating similar systems in arthropod vectors to interfere with disease transmission. We have discovered a branch of the M. sexta protease network that detects Gram-positive bacteria and fungi and mediates PPO activation. In this network, pathogen recognition receptors bind to microbes and initiate protease pathways for PPO and Toll activation. We have identified a new Sushi-domain protease that may participate in a branch of the pathway responsive to Gram-negative bacterial infection. A positive feedback loop in the protease system controls locality and potency of the defense responses. We plan to extend our research on the PPO activation reaction by examining the initiation and regulation of immune protease pathways.
The specific aims of this project are: 1) Characterization of the pathway initiation by Gram-negative bacteria;2) Elucidation of the positive regulatory mechanisms in the protease system;3) Investigation of the structure, function, and activation of M. sexta PPO.

Public Health Relevance

This research will continue to elucidate the function and regulation of a serine protease network during innate immune responses, which produces phenoloxidase and antimicrobial peptides to entrap and kill parasites that cause malaria and filariasis. The acquired knowledge will be useful for disrupting the transmission of human diseases in vector species.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM058634-13
Application #
8135975
Study Section
Vector Biology Study Section (VB)
Program Officer
Gindhart, Joseph G
Project Start
1999-03-01
Project End
2013-08-31
Budget Start
2011-09-01
Budget End
2012-08-31
Support Year
13
Fiscal Year
2011
Total Cost
$221,050
Indirect Cost
Name
Oklahoma State University Stillwater
Department
Other Basic Sciences
Type
Schools of Earth Sciences/Natur
DUNS #
049987720
City
Stillwater
State
OK
Country
United States
Zip Code
74078
He, Xuesong; Cao, Xiaolong; He, Yan et al. (2017) Hemolymph proteins of Anopheles gambiae larvae infected by Escherichia coli. Dev Comp Immunol 74:110-124
Cao, Xiaolong; Jiang, Haobo (2017) An analysis of 67 RNA-seq datasets from various tissues at different stages of a model insect, Manduca sexta. BMC Genomics 18:796
Schrag, Lynn G; Cao, Xiaolong; Herrera, Alvaro I et al. (2017) Solution Structure and Expression Profile of an Insect Cytokine: Manduca sexta Stress Response Peptide-2. Protein Pept Lett 24:3-11
Cao, Xiaolong; Gulati, Mansi; Jiang, Haobo (2017) Serine protease-related proteins in the malaria mosquito, Anopheles gambiae. Insect Biochem Mol Biol 88:48-62
He, Yan; Wang, Yang; Yang, Fan et al. (2017) Manduca sexta hemolymph protease-1, activated by an unconventional non-proteolytic mechanism, mediates immune responses. Insect Biochem Mol Biol 84:23-31
He, Yan; Wang, Yang; Zhao, Picheng et al. (2017) Serpin-9 and -13 regulate hemolymph proteases during immune responses of Manduca sexta. Insect Biochem Mol Biol 90:71-81
Wang, Yang; Jiang, Haobo (2017) Prophenoloxidase activation and antimicrobial peptide expression induced by the recombinant microbe binding protein of Manduca sexta. Insect Biochem Mol Biol 83:35-43
He, Yan; Cao, Xiaolong; Zhang, Shuguang et al. (2016) Changes in the Plasma Proteome of Manduca sexta Larvae in Relation to the Transcriptome Variations after an Immune Challenge: Evidence for High Molecular Weight Immune Complex Formation. Mol Cell Proteomics 15:1176-87
Hu, Yingxia; Wang, Yang; Deng, Junpeng et al. (2016) The structure of a prophenoloxidase (PPO) from Anopheles gambiae provides new insights into the mechanism of PPO activation. BMC Biol 14:2
Kanost, Michael R; Arrese, Estela L; Cao, Xiaolong et al. (2016) Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta. Insect Biochem Mol Biol 76:118-147

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