Ostrinia furnacalis serpin-3 regulates melanization cascade by inhibiting a prophenoloxidase-activating protease. (June 2015)

• Record Type: Journal Article
• Authors: Chu, Yuan; Zhou, Fan; Liu, Yang; Hong, Fang; Wang, Guirong; An, Chunju
• Is Part Of: Insect biochemistry and molecular biology. Volume 61(2015:Jun.)
• Page Start: 53
• Page End: 61
• Publication Date: 2015-06
• Subjects: Serpin -- Prophenoloxidase activation -- Melanization -- Immunity; BSA bovine serum albumin -- PO and proPO phenoloxidase and its precursor -- PAP proPO activating proteinase -- qRT-PCR quantitative reverse transcript (qRT)-PCR -- SDS-PAGE SDS-polyacrylamide gel electrophoresis -- Serpin serine proteinase inhibitor; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2015.03.007
• Languages: English
• ISSNs: 0965-1748

Abstract

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. Graphical abstract: Highlights: We cloned the full-length cDNA for a serpin in Ostrinia furnacalis, named as serpin-3. The expression of serpin-3 gene is induced upon a microbial challenge. Serpin-3 efficiently blocks prophenoloxidase activation in larval plasma. Serpin-3 forms covalent complexes with SP13, and prevents SP13 from cleaving proPO. Injection of serpin-3 into larvae results in decreased melanin synthesis.