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.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Vector Biology Study Section (VB)
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Gindhart, Joseph G
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Oklahoma State University Stillwater
Other Basic Sciences
Schools of Earth Sciences/Natur
United States
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Cao, Xiaolong; Jiang, Haobo (2018) Building a platform for predicting functions of serine protease-related proteins in Drosophila melanogaster and other insects. Insect Biochem Mol Biol 103:53-69
Yang, Fan; Wang, Yang; Sumathipala, Niranji et al. (2018) Manduca sexta serpin-12 controls the prophenoloxidase activation system in larval hemolymph. Insect Biochem Mol Biol 99:27-36
Feng, Congjing; Zhao, Ya; Chen, Kangkang et al. (2018) Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenée to defend against bacterial infection. Dev Comp Immunol 87:204-215
Li, Miao; Christen, Jayne M; Dittmer, Neal T et al. (2018) The Manduca sexta serpinome: Analysis of serpin genes and proteins in the tobacco hornworm. Insect Biochem Mol Biol 102:21-30
He, Yan; Wang, Yang; Hu, Yingxia et al. (2018) Manduca sexta hemolymph protease-2 (HP2) activated by HP14 generates prophenoloxidase-activating protease-2 (PAP2) in wandering larvae and pupae. Insect Biochem Mol Biol 101:57-65
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, Xuesong; Cao, Xiaolong; He, Yan et al. (2017) Hemolymph proteins of Anopheles gambiae larvae infected by Escherichia coli. Dev Comp Immunol 74:110-124
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
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
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

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