title: Ostrinia furnacalis serpin-3 regulates melanization cascade by inhibiting a prophenoloxidase-activating protease.
abstract: Serine protease cascade-mediated prophenolxidase activation is a prominent innate immune response in insect defense against the invading pathogens. Serpins regulate this reaction to avoid excessive activation. However, the function of serpins in most insect species, especially in some non-model agriculture insect pests, is largely unknown. We here cloned a full-length cDNA for a serpin, named as serpin-3, from Asian corn borer, Ostrinia furnacalis (Guenée). The open reading frame of serpin-3 encodes 462-amino acid residue protein with a 19-residue signal peptide. It contains a reactive center loop strikingly similar to the proteolytic activation site in prophenoloxidase. Sequence comparison indicates that O. furnacalis serpin-3 is an apparent ortholog of Manduca sexta serpin-3, a defined negative regulator of melanization reaction. Serpin-3 mRNA and protein levels significantly increase after a bacterial or fungal injection. Recombinant serpin-3 efficiently blocks prophenoloxidase activation in larval plasma in a concentration-dependent manner. It forms SDS-stable complexes with serine protease 13 (SP13), and prevents SP13 from cleaving prophenoloxidase. Injection of recombinant serpin-3 into larvae results in decreased fungi-induced melanin synthesis and reduced the expression of attacin, cecropin, gloverin, and peptidoglycan recognition protein-1 genes in the fat body. Altogether, serpin-3 plays important roles in the regulation of prophenoloxidase activation and antimicrobial peptide production in O. furnacalis larvae.
authors.affiliation: Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, 100193, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chu
authors.affiliation: Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, 100193, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhou
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, 100193, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Hong
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
authors.forename: Guirong
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, 100193, China. Electronic address: anchunju@cau.edu.cn.
authors.forename: Chunju
authors.initials: C
authors.lastname: An
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D052982:Beauveria / Q000502:physiology; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004792:Enzyme Precursors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000502:physiology; D006458:Hemolymph / Q000201:enzymology; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D007814:Larva / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D008543:Melanins / Q000378:metabolism*; D016982:Micrococcus luteus / Q000502:physiology; D009036:Moths / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism; D015843:Serpins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004792:Enzyme Precursors; D019476:Insect Proteins; D008543:Melanins; D011994:Recombinant Proteins; D015843:Serpins; C038451:pro-phenoloxidase; D004156:Catechol Oxidase; D012697:Serine Endopeptidases
keywords: Immunity; Melanization; Prophenoloxidase activation; Serpin