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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 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Liu HW, Wang LL, Meng Z, Tang X, Li YS, Xia QY, Zhao P. A clip domain serine protease involved in moulting in the silkworm, Bombyx mori: cloning, characterization, expression patterns and functional analysis. Insect Mol Biol 2017; 26:507-521. [PMID: 28597953 DOI: 10.1111/imb.12312] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Clip domain serine proteases (CLIPs), characterized by one or more conserved clip domains, are essential components of extracellular signalling cascades in various biological processes, especially in innate immunity and the embryonic development of insects. Additionally, CLIPs may have additional non-immune functions in insect development. In the present study, the clip domain serine protease gene Bombyx mori serine protease 95 (BmSP95), which encodes a 527-residue protein, was cloned from the integument of B. mori. Bioinformatics analysis indicated that BmSP95 is a typical CLIP of the subfamily D and possesses a clip domain at the N terminus, a trypsin-like serine protease (tryp_spc) domain at the C terminus and a conserved proline-rich motif between these two domains. At the transcriptional level, BmSP95 is expressed in the integument during moulting and metamorphosis, and the expression pattern is consistent with the fluctuating 20-hydroxyecdysone (20E) titre in B. mori. At the translational level, BmSP95 protein is synthesized in the epidermal cells, secreted as a zymogen and activated in the moulting fluid. Immunofluorescence revealed that BmSP95 is distributed into the old endocuticle in the moulting stage. The expression of BmSP95 was upregulated by 20E. Moreover, expression of BmSP95 was downregulated by pathogen infection. RNA interference-mediated silencing of BmSP95 led to delayed moulting from pupa to moth. These results suggest that BmSP95 is involved in integument remodelling during moulting and metamorphosis.
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Affiliation(s)
- H-W Liu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - L-L Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Z Meng
- College of Biotechnology, Southwest University, Chongqing, China
| | - X Tang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Y-S Li
- Vitamin D Research Institute, Shaanxi University of Technology, Hanzhong, Shaanxi, China
| | - Q-Y Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - P Zhao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
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Nakhleh J, Christophides GK, Osta MA. The serine protease homolog CLIPA14 modulates the intensity of the immune response in the mosquito Anopheles gambiae. J Biol Chem 2017; 292:18217-18226. [PMID: 28928218 PMCID: PMC5672044 DOI: 10.1074/jbc.m117.797787] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 09/13/2017] [Indexed: 11/06/2022] Open
Abstract
Clip domain serine protease homologs (SPHs) are positive and negative regulators of Anopheles gambiae immune responses mediated by the complement-like protein TEP1 against Plasmodium malaria parasites and other microbial infections. We have previously reported that the SPH CLIPA2 is a negative regulator of the TEP1-mediated response by showing that CLIPA2 knockdown (kd) enhances mosquito resistance to infections with fungi, bacteria, and Plasmodium parasites. Here, we identify another SPH, CLIPA14, as a novel regulator of mosquito immunity. We found that CLIPA14 is a hemolymph protein that is rapidly cleaved following a systemic infection. CLIPA14 kd mosquitoes elicited a potent melanization response against Plasmodium berghei ookinetes and exhibited significantly increased resistance to Plasmodium infections as well as to systemic and oral bacterial infections. The activity of the enzyme phenoloxidase, which initiates melanin biosynthesis, dramatically increased in the hemolymph of CLIPA14 kd mosquitoes in response to systemic bacterial infections. Ookinete melanization and hemolymph phenoloxidase activity were further increased after cosilencing CLIPA14 and CLIPA2, suggesting that these two SPHs act in concert to control the melanization response. Interestingly, CLIPA14 RNAi phenotypes and its infection-induced cleavage were abolished in a TEP1 loss-of-function background. Our results suggest that a complex network of SPHs functions downstream of TEP1 to regulate the melanization reaction.
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Affiliation(s)
- Johnny Nakhleh
- From the Department of Biology, American University of Beirut, Beirut 1107 2020, Lebanon and
| | | | - Mike A Osta
- From the Department of Biology, American University of Beirut, Beirut 1107 2020, Lebanon and
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