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Morejon B, Michel K. The expanded immunoregulatory protease network in mosquitoes is governed by gene co-expression. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.18.599423. [PMID: 38948760 PMCID: PMC11212970 DOI: 10.1101/2024.06.18.599423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Serine protease cascades regulate key innate immune responses. In mosquitoes, these cascades involve clip-domain serine proteases and their non-catalytic homologs (CLIPs), forming a complex network whose make-up and structural organization is not fully understood. This study assessed the impact of 85 CLIPs on humoral immunity in Anopheles gambiae. By coupling RNAi with assays measuring antimicrobial activity and melanization, we identified 27 CLIPs as immunoregulators that together form two distinct subnetworks. CLIPs regulating antimicrobial activity were found to control infection resistance, as knockdowns reduced bacterial load and improved survival. Furthermore, our analysis of CLIP gene expression unveiled a novel immunoregulatory mechanism reliant on protease baseline co-expression rather than infection-induced upregulation. These findings underscore that despite its complexity mosquito immune regulation may be targeted for malaria interventions.
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Affiliation(s)
- Bianca Morejon
- Division of Biology, Kansas State University; Manhattan, KS, 66502, USA
| | - Kristin Michel
- Division of Biology, Kansas State University; Manhattan, KS, 66502, USA
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Zhang X, Zhang S, Kuang J, Sellens KA, Morejon B, Saab SA, Li M, Metto EC, An C, Culbertson CT, Osta MA, Scoglio C, Michel K. CLIPB4 is a central node in the protease network that regulates humoral immunity in Anopheles gambiae mosquitoes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.07.545904. [PMID: 37461554 PMCID: PMC10350057 DOI: 10.1101/2023.07.07.545904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Insect humoral immune responses are regulated in part by protease cascades, whose components circulate as zymogens in the hemolymph. In mosquitoes, these cascades consist of clip domain serine proteases (cSPs) and/or their non-catalytic homologs (cSPHs), which form a complex network, whose molecular make-up is not fully understood. Using a systems biology approach, based on a co-expression network of gene family members that function in melanization and co-immunoprecipitation using the serine protease inhibitor (SRPN)2, a key negative regulator of the melanization response in mosquitoes, we identify the cSP CLIPB4 from the African malaria mosquito Anopheles gambiae as a central node in this protease network. CLIPB4 is tightly co-expressed with SRPN2 and forms protein complexes with SRPN2 in the hemolymph of immune-challenged female mosquitoes. Genetic and biochemical approaches validate our network analysis and show that CLIPB4 is required for melanization and antibacterial immunity, acting as a prophenoloxidase (proPO)-activating protease, which is inhibited by SRPN2. In addition, we provide novel insight into the structural organization of the cSP network in An. gambiae, by demonstrating that CLIPB4 is able to activate proCLIPB8, a cSP upstream of the proPO-activating protease CLIPB9. These data provide the first evidence that, in mosquitoes, cSPs provide branching points in immune protease networks and deliver positive reinforcement in proPO activation cascades.
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Affiliation(s)
- Xiufeng Zhang
- Division of Biology, Kansas State University, Manhattan, KS, USA
| | - Shasha Zhang
- Division of Biology, Kansas State University, Manhattan, KS, USA
- Department of Entomology, College of Plant Protection, China Agricultural University, Beijing, China
| | - Junyao Kuang
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA
| | | | - Bianca Morejon
- Division of Biology, Kansas State University, Manhattan, KS, USA
| | - Sally A. Saab
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Miao Li
- Division of Biology, Kansas State University, Manhattan, KS, USA
| | - Eve C. Metto
- Department of Chemistry, Kansas State University, Manhattan, KS, USA
| | - Chunju An
- Department of Entomology, College of Plant Protection, China Agricultural University, Beijing, China
| | | | - Mike A. Osta
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Caterina Scoglio
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA
| | - Kristin Michel
- Division of Biology, Kansas State University, Manhattan, KS, USA
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