A bumblebee (Bombus ignitus) venom serine protease inhibitor that acts as a microbial serine protease inhibitor

Dual function of a bumblebee (Bombus ignitus) serine protease inhibitor that acts as a microbicidal peptide and anti-fibrinolytic venom toxin

In bee venoms, low-molecular-weight peptides, including serine protease inhibitors (SPIs), exhibit multifunctional activities. Although SPIs in bee venoms are relatively well known, those that function in both the body and secreted venom of bees are not well-characterized. In this study, we identified a bumblebee (Bombus ignitus) SPI (BiSPI) that displays microbicidal and anti-fibrinolytic activities. BiSPI was found to consist of a trypsin inhibitor-like domain containing a P1 site and ten cysteine residues. We observed that the BiSPI gene was ubiquitously transcribed in the body, including the venom glands. In correlation, the BiSPI protein was detected both in the body and secreted venom by using an antibody against a recombinant BiSPI peptide produced in baculovirus-infected insect cells. Recombinant BiSPI exhibited inhibitory activity against trypsin but not chymotrypsin and inhibited microbial serine proteases and plasmin but not elastase or thrombin. Moreover, recombinant BiSPI recognized carbohydrates and bound to fungi and gram-negative and gram-positive bacteria. Consistent with these properties, recombinant BiSPI exhibited microbicidal activities against bacteria and fungi through induction of structural damage by binding to the microbial surfaces. Additionally, recombinant BiSPI inhibited the plasmin-mediated degradation of human fibrin and was thus concluded to exhibit anti-fibrinolytic activity. Moreover, the peptide showed no effect on hemolysis. These findings demonstrate the dual function of BiSPI, which acts as a microbicidal peptide and anti-fibrinolytic venom toxin.

A serpin (CvT-serpin15) of teratocytes contributes to microbial-resistance in Plutella xylostella during Cotesia vestalis parasitism

BACKGROUND

Parasitic wasps are an important group of entomophagous insects for pest control. As parasitic wasps often lay eggs on or into their associated hosts, parasitoids evolve to utilize several factors including venom, polydnavirus (PDV) to alter host physiology for successful parasitism. Some taxa of endoparasitoids produce teratocytes, which are a type of cell that is released into host insects when wasp eggs hatch. Teratocytes display multifunction in parasitism such as host nutritional exploration, immune and developmental regulation, by secreting plenty of proteins into host hemocoel.

RESULTS

A serpin (CvT-serpin15) secreted by teratocytes was characterized. QPCR results showed the expressional level of CvT-serpin15 was upregulated following bacterial challenges. Enzyme activity experiment indicated the recombinant CvT-serpin15 protein could interfere with the growth of Gram-positive bacteria Staphylococcus aureus. The survival rate assay demonstrated CvT-serpin15 increased survival rate of Plutella xylostella infected by S. aureus.

CONCLUSION

CvT-serpin15 secreted by teratocytes would boost the host immune system when pathogens invade host hemocoel during parasitism, and ultimately protect the development of wasp larva from bacterial infection. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Anti-fibrinolytic activity of a metalloprotease inhibitor from bumblebee (Bombus ignitus) venom

Bee venom is a mixture of bioactive components that include proteases and protease inhibitors. A metalloprotease inhibitor has been predicted to be a bumblebee-specific toxin in the venom proteome of Bombus terrestris; however, the identification and functional roles of bee venom metalloprotease inhibitors have not been previously determined. In this study, we identified a bumblebee (B. ignitus) venom metalloprotease inhibitor (BiVMPI) that exhibits anti-fibrinolytic activity. BiVMPI contains a trypsin inhibitor-like cysteine-rich domain that exhibits similarity to inducible metalloprotease inhibitor. Using an anti-BiVMPI antibody raised against a recombinant BiVMPI protein produced in baculovirus-infected insect cells, the presence of BiVMPI in the venom gland and secreted venom of B. ignitus worker bees was confirmed. The recombinant BiVMPI protein demonstrated inhibitory activity against a metalloprotease, trypsin, chymotrypsin, protease K, and plasmin, but not subtilisin A, elastase, or thrombin. Additionally, the recombinant BiVMPI bound to plasmin and inhibited the plasmin-mediated degradation of fibrin, demonstrating an anti-fibrinolytic role for BiVMPI as a bee venom metalloprotease inhibitor. Our results provide the first evidence for the identification and anti-fibrinolytic activity of a metalloprotease inhibitor from bee venom.

Kunitz-type serine protease inhibitor is a novel participator in anti-bacterial and anti-inflammatory responses in Japanese flounder (Paralichthys olivaceus)

Kunitz-type serine protease inhibitor (KSPI) interacts with serine protease (SP) to regulate cascade reactions in vivo and plays essential roles in innate immunity. Theoretical considerations support various functions of kspi, but further studies are required for full characterization of these functions. In this study, a KSPI molecule was identified from Japanese flounder (Paralichthys olivaceus), and was named Pokspi. The full-length cDNA sequence of Pokspi was 2810 nt, containing an open reading frame of 1527 nt, which encoded a polypeptide of 509 amino acid residues. PoKspi protein contained five conversed domains, namely, MANEC, PKD, LDLa and two Kunitz domains. Homology analysis revealed that Pokspi shared the highest similarity (83%) with its homolog in Cynoglossus semilaevis. Phylogenetic analysis indicated that Pokspi clustered with the homologs in other fishes. The mRNA transcripts of Pokspi were detected in all tested tissues, with the highest expression level in gill, followed by kidney and intestine. Its elevated expression in response to the application of Edwardsiella tarda (in vivo) and pathogen-associated molecular pattern (in vitro) suggested the involvement of Pokspi in the essential immune defense against various pathogens. Recombinant PoKspi (rPoKspi) purified from Escherichia coli exhibited not only serine protease inhibitor activities but also a broad spectrum of anti-microbial effect in a manner that was independent of any host factors. In addition, the recombinant PoKspi protein could cause the down-regulation of pro-inflammatory factors TNF-α and IL-1β. In conclusion, Pokspi is a biologically active serine protease inhibitor endowed with anti-bacterial and anti-inflammatory property. This study provides strong evidences for understanding the innate immune defense in Japanese flounder.

Proteomic Characterization of the Venom of Five Bombus (Thoracobombus) Species

Venomous animals use venom, a complex biofluid composed of unique mixtures of proteins and peptides, to act on vital systems of the prey or predator. In bees, venom is solely used for defense against predators. However, the venom composition of bumble bees (Bombus sp.) is largely unknown. The Thoracobombus subgenus of Bombus sp. is a diverse subgenus represented by 14 members across Turkey. In this study, we sought out to proteomically characterize the venom of five Thoracobombus species by using bottom-up proteomic techniques. We have obtained two-dimensional polyacrylamide gel (2D-PAGE) images of each species’ venom sample. We have subsequently identified the protein spots by using matrix assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF MS). We have identified 47 proteins for Bombus humilis, 32 for B. pascuorum, 60 for B. ruderarius, 39 for B. sylvarum, and 35 for B. zonatus. Moreover, we illustrated that intensities of 2DE protein spots corresponding to putative venom toxins vary in a species-specific manner. Our analyses provide the primary proteomic characterization of five bumble bee species’ venom composition.

Antimicrobial peptides (AMPs): The quintessential 'offense and defense' molecules are more than antimicrobials

Antimicrobial peptides (AMPs) are cationic amphiphilic molecules with α-helix or β-sheet linear motifs and linear or cyclic configurations. For their role in 'defense and offense', they are present in all living organisms. AMPs are named so, as they inhibit a wide array of microbes by membrane pore formation and subsequent perturbation of mitochondrial membrane ionic balance. However, their functional repertoire is expanding with validated roles in cytotoxicity, wound healing, angiogenesis, apoptosis, and chemotaxis [1]. A number of endogenous AMPs have been characterized in human body such as defensins, cathelicidins, histatins etc. They mediate critical functions, but when homeostasis is broken, they turn hostile and initiate inflammatory diseases. This review discusses the sources of therapeutic AMPs; auto-immunity risks of endogenous AMPs, and their dermatological applications; normally overlooked risks of the peptides; and scopes ahead. This holistic work is expected to be a valuable reference for further research in this field.

Anti-fibrinolytic and anti-microbial activities of a serine protease inhibitor from honeybee (Apis cerana) venom

Bee venom contains a variety of peptide constituents, including low-molecular-weight protease inhibitors. While the putative low-molecular-weight serine protease inhibitor Api m 6 containing a trypsin inhibitor-like cysteine-rich domain was identified from honeybee (Apis mellifera) venom, no anti-fibrinolytic or anti-microbial roles for this inhibitor have been elucidated. In this study, we identified an Asiatic honeybee (A. cerana) venom serine protease inhibitor (AcVSPI) that was shown to act as a microbial serine protease inhibitor and plasmin inhibitor. AcVSPI was found to consist of a trypsin inhibitor-like domain that displays ten cysteine residues. Interestingly, the AcVSPI peptide sequence exhibited high similarity to the putative low-molecular-weight serine protease inhibitor Api m 6, which suggests that AcVSPI is an allergen Api m 6-like peptide. Recombinant AcVSPI was expressed in baculovirus-infected insect cells, and it demonstrated inhibitory activity against trypsin, but not chymotrypsin. Additionally, AcVSPI has inhibitory effects against plasmin and microbial serine proteases; however, it does not have any detectable inhibitory effects on thrombin or elastase. Consistent with these inhibitory effects, AcVSPI inhibited the plasmin-mediated degradation of fibrin to fibrin degradation products. AcVSPI also bound to bacterial and fungal surfaces and exhibited anti-microbial activity against fungi as well as gram-positive and gram-negative bacteria. These findings demonstrate the anti-fibrinolytic and anti-microbial roles of AcVSPI as a serine protease inhibitor.

Anti-aging effect and gene expression profiling of dung beetle glycosaminoglycan in aged rats

BACKGROUND

This study aimed to evaluate the anti-aging effect of a newly prepared insect-derived compound, dung beetle glycosaminoglycan (GAG), given intraperitoneally to old SD rats as part of their diet for 1 month. Insect GAG administration was found to be related to a reduction in oxidative damage, hepato-cellular biomarker levels, protein carbonyl content, and malondialdehyde concentration. The anti-aging-related molecular genetic mechanisms of dung beetle GAG are not yet fully elucidated.

RESULTS

Catharsius molossus (a type of dung beetle) GAG (CaG) possessed anti-aging activities; it reduced the serum level of creatinine kinase, had aortic vasorelaxant activities and cardioprotective actions, and maintained a normal glucose level in treated rats. Microarray analysis was performed with a rat 30 K cDNA clone set array to identify the gene-expression profiles of 14-month-old SD rats treated with dung beetle glycosaminoglycan 5 mg/kg (CaG5) over a 1-month period, which was done to investigate its anti-aging effect as compared to that of either Bombus ignitus (a type of bumblebee) queen GAG 5 mg/kg (IQG5) or chondroitin sulfate 10 mg/kg. CaG5 and IQG5 had marked anti-inflammatory effects, bringing about inhibition of free fatty acid, uric acid, sGPT, IL-1 beta, and CK values. In addition, anticoagulant and antithrombotic effects were seen: the concentration of factor 1 (fibrinogen) was increased in CaG- treated rat plasma. The CaG5-treated rat group, compared to the control, displayed upregulation of 131 genes, including lipocalin 2 (Lbp) and a serine peptidase inhibitor, Kaszal type3 (Spink3), and 64 downregulated genes, including lysyl oxidase (Lox), serine dehydratase (sds), and retinol saturase (Retsat).

CONCLUSION

Our data suggest that dung beetle glycosaminoglycan may be a helpful treatment for aged rats, which indicates its potential as a therapeutic biomaterial for aging.

Secapin, a bee venom peptide, exhibits anti-fibrinolytic, anti-elastolytic, and anti-microbial activities

Bee venom contains a variety of peptide constituents that have various biological, toxicological, and pharmacological actions. However, the biological actions of secapin, a venom peptide in bee venom, remain largely unknown. Here, we provide the evidence that Asiatic honeybee (Apis cerana) secapin (AcSecapin-1) exhibits anti-fibrinolytic, anti-elastolytic, and anti-microbial activities. The recombinant mature AcSecapin-1 peptide was expressed in baculovirus-infected insect cells. AcSecapin-1 functions as a serine protease inhibitor-like peptide that has inhibitory effects against plasmin, elastases, microbial serine proteases, trypsin, and chymotrypsin. Consistent with these functions, AcSecapin-1 inhibited the plasmin-mediated degradation of fibrin to fibrin degradation products, thus indicating the role of AcSecapin-1 as an anti-fibrinolytic agent. AcSecapin-1 also inhibited both human neutrophil and porcine pancreatic elastases. Furthermore, AcSecapin-1 bound to bacterial and fungal surfaces and exhibited anti-microbial activity against fungi and gram-positive and gram-negative bacteria. Taken together, our data demonstrated that the bee venom peptide secapin has multifunctional roles as an anti-fibrinolytic agent during fibrinolysis and an anti-microbial agent in the innate immune response.