Serpins regulate various physiological reactions in humans and insects, including certain immune responses, primarily through inhibition of serine proteases. Six serpins have previously been identified and characterized in the tobacco hornworm Manduca sexta. In this study, we obtained a full-length cDNA sequence of another Manduca serpin, named serpin-7. The open reading frame of serpin-7 encodes a polypeptide of 400 amino acid residues with a predicted signal peptide of the first 15 residues. Multiple protein sequence alignment of the reactive center loop region of the M. sexta serpins indicated that serpin-7 contains Arg-Ile at the position of the predicted scissile bond cleaved by protease in the serpin inhibition mechanism. The same residues occur in the scissile bond of the reactive center loop in M. sexta serpin-4 and serpin-5, which are protease inhibitors that can block prophenoloxidase activation in plasma. Serpin-7 transcript was detected in hemocytes and fat body, and its expression increased in fat body after injection of larvae with Micrococcus luteus. Recombinant serpin-7 added to larval plasma inhibited spontaneous melanization and decreased prophenoloxidase activation stimulated by bacteria. Serpin-7 inhibited prophenoloxidase-activating protease-3 (PAP3), forming a stable serpin-protease complex. Considering that serpin-3 and serpin-6 are also efficient inhibitors of PAP3, it appears that multiple serpins present in plasma may have redundant or overlapping functions. We conclude that serpin-7 has serine protease inhibitory activity and is likely involved in regulation of proPO activation or other protease-mediated aspects of innate immunity in M. sexta.
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http://dx.doi.org/10.1016/j.ibmb.2013.03.015 | DOI Listing |
Insect Biochem Mol Biol
January 2025
Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:
Insect prophenoloxidases (proPO) are activated during immune responses by a proPO activating protease (PAP) in the presence of a high molecular weight cofactor assembled from serine protease homologs (SPH) that lack proteolytic activity. PAPs and the SPHs have a similar architecture, with an amino-terminal clip domain and a carboxyl-terminal protease domain. The SPHs belong to CLIPA subfamily of SP-related proteins.
View Article and Find Full Text PDFCells
January 2025
Innate Immunity Group, Institute of Genetics, HUN-REN Biological Research Centre, 6726 Szeged, Hungary.
Parasitoid elimination in involves special hemocytes, called lamellocytes, which encapsulate the eggs or larvae of the parasitoid wasps. The capsules are melanized, and metabolites of the melanization reaction may play a potential role in parasitoid killing. We have observed a variation in the melanization capacity of different, commonly used strains, such as Canton-S, Oregon-R, and BL5905, BL6326.
View Article and Find Full Text PDFAntioxidants (Basel)
November 2024
Department of Ocean Integrated Science, Chonnam National University, Yeosu 59626, Republic of Korea.
Endocrine-disrupting chemicals (EDCs) significantly damage biological systems related to reproductive, neurological, and metabolic functions. Approximately 1000 chemicals are known to possess endocrine-acting properties, including bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP). This study primarily focuses on the potential effects of EDCs on the transcriptional levels of innate immune prophenoloxidase (proPO) system-related genes under oxidative stress in the gonads and stomach of the mud crab , an indicator species for assessing coastal benthic environments, when exposed to 1 µg L, 10 µg L, and 30 µg L BPA or DEHP.
View Article and Find Full Text PDFJ Agric Food Chem
January 2025
MOE Key Laboratory of Bio-Intelligent Manufacturing, School of Bioengineering, Dalian University of Technology, Dalian 116024, China.
Plant natural products are crucial in defending against herbivorous insects and are widely used in pest control, yet their mechanisms remain complex and insufficiently studied. This study employed a reverse strategy to investigate the mechanism of camptothecin (CPT), a botanical pesticide. By using a CPT-based chemical probe coupled with proteomic analysis, immune-related proteins, including those involved in prophenoloxidase (PPO) activation and antimicrobial peptide (AMP) synthesis, were identified in the Asian corn borer, .
View Article and Find Full Text PDFComp Biochem Physiol Part D Genomics Proteomics
December 2024
School for the Environment, University of Massachusetts Boston, Boston, MA 02125, USA; Presidents Office, Ursinus College, Collegeville, PA 19426, USA.
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