Jae-Sam Hwang

Structure and Function of Papiliocin with Antimicrobial and Anti-inflammatory Activities Isolated from the Swallowtail Butterfly, Papilio xuthus

Papiliocin is a novel 37-residue cecropin-like peptide isolated recently from the swallowtail butterfly, Papilio xuthus. With the aim of identifying a potent antimicrobial peptide, we tested papiliocin in a variety of biological and biophysical assays, demonstrating that the peptide possesses very low cytotoxicity against mammalian cells and high bacterial cell selectivity, particularly against Gram-negative bacteria as well as high anti-inflammatory activity. Using LPS-stimulated macrophage RAW264.7 cells, we found that papiliocin exerted its anti-inflammatory activities by inhibiting nitric oxide (NO) production and secretion of tumor necrosis factor (TNF)-α and macrophage inflammatory protein (MIP)-2, producing effects comparable with those of the antimicrobial peptide LL-37. We also showed that the innate defense response mechanisms engaged by papiliocin involve Toll-like receptor pathways that culminate in the nuclear translocation of NF-κB. Fluorescent dye leakage experiments showed that papiliocin targets the bacterial cell membrane. To understand structure-activity relationships, we determined the three-dimensional structure of papiliocin in 300 mm dodecylphosphocholine micelles by NMR spectroscopy, showing that papiliocin has an α-helical structure from Lys3 to Lys21 and from Ala25 to Val36, linked by a hinge region. Interactions between the papiliocin and LPS studied using tryptophan blue-shift data, and saturation transfer difference-NMR experiments revealed that Trp2 and Phe5 at the N-terminal helix play an important role in attracting papiliocin to the cell membrane of Gram-negative bacteria. In conclusion, we have demonstrated that papiliocin is a potent peptide antibiotic with both anti-inflammatory and antibacterial activities, and we have laid the groundwork for future studies of its mechanism of action.

Isolation and Characterization of a Defensin-Like Peptide (Coprisin) from the Dung Beetle, Copris tripartitus

The antibacterial activity of immune-related peptides, identified by a differential gene expression analysis, was investigated to suggest novel antibacterial peptides. A cDNA encoding a defensin-like peptide, Coprisin, was isolated from bacteria-immunized dung beetle, Copris tripartitus, by using differential dot blot hybridization. Northern blot analysis showed that Coprisin mRNA was up-regulated from 4 hours after bacteria injection and its expression level was reached a peak at 16 hours. The deduced amino acid sequence of Coprisin was composed of 80 amino acids with a predicted molecular weight of 8.6 kDa and a pI of 8.7. The amino acid sequence of mature Coprisin was found to be 79.1% and 67.4% identical to those of defensin-like peptides of Anomala cuprea and Allomyrina dichotoma, respectively. We also investigated active sequences of Coprisin by using amino acid modification. The result showed that the 9-mer peptide, LLCIALRKK-NH2, exhibited potent antibacterial activities against Escherichia coli and Staphylococcus aureus.

Induction of yeast apoptosis by an antimicrobial peptide, Papiliocin

Papiliocin is a 37-residue peptide isolated from the swallowtail butterfly Papilio xuthus. In this study, we found that Papiliocin induced the accumulation of reactive oxygen species (ROS) and hydroxyl radicals known to be important regulators of apoptosis in Candida albicans. To examine the relationship between the accumulation of ROS and the induction of apoptosis, we investigated the apoptotic effects of Papiliocin using apoptotic markers. Cells treated with Papiliocin showed a series of cellular changes normally seen in cells undergoing apoptosis: plasma membrane translocation of phosphatidylserine from the inner to the outer membrane leaflet, measured by Annexin V staining, dissipation of the mitochondrial membrane potential, observed by DiOC(6)(3) staining; and the presence of active metacaspases, measured using the CaspACE FITC-VAD-FMK, as early apoptotic events. In addition, DNA condensation and fragmentation, which is important marker of late stage apoptosis, was seen by DAPI and TUNEL assay. Therefore, these results suggest that Papiliocin leads to apoptosis in C. albicans via ROS accumulation.

Insight into the antimicrobial activities of coprisin isolated from the dung beetle, Copris tripartitus, revealed by structure-activity relationships

The novel 43-residue, insect defensin-like peptide coprisin, isolated from the dung beetle, Copris tripartitus, is a potent antibiotic with bacterial cell selectivity, exhibiting antimicrobial activities against Gram-positive and Gram-negative bacteria without exerting hemolytic activity against human erythrocytes. Tests against Staphylococcus aureus using fluorescent dye leakage and depolarization measurements showed that coprisin targets the bacterial cell membrane. To understand structure-activity relationships, we determined the three-dimensional structure of coprisin in aqueous solution by nuclear magnetic resonance spectroscopy, which showed that coprisin has an amphipathic α-helical structure from Ala(19) to Arg(28), and β-sheets from Gly(31) to Gln(35) and Val(38) to Arg(42). Coprisin has electropositive regions formed by Arg(28), Lys(29), Lys(30), and Arg(42) and ITC results proved that coprisin and LPS have electrostatically driven interactions. Using measurements of nitric oxide release and inflammatory cytokine production, we provide the first verification of the anti-inflammatory activity and associated mechanism of an insect defensin, demonstrating that the anti-inflammatory actions of the defensin-like peptide, coprisin, are initiated by suppressing the binding of LPS to toll-like receptor 4, and subsequently inhibiting the phosphorylation of p38 mitogen-activated protein kinase and nuclear translocation of NF-kB. In conclusion, we have demonstrated that an amphipathic helix and an electropositive surface in coprisin may play important roles in its effective interaction with bacterial cell membranes and, ultimately, in its high antibacterial activity and potent anti-inflammatory activity. In addition to elucidating the antimicrobial action of coprisin, this work may provide insight into the mechanism of action of insect defense systems.

Bombyx mori transferrin: genomic structure, expression and antimicrobial activity of recombinant protein.

Transferrin (Tf) is a multifunctional, iron binding protein found in both vertebrates and invertebrates. Although transferrin has been suggested to play a role in innate immunity, its immunological function during infection has not been characterized. In this study, we identified and characterized Bombyx mori transferrin (BmTf). The promoter region of BmTf has numerous putative NF-kappaB binding sites, suggesting its possible function in innate immunity. Analysis of BmTf gene expression shows that it is highly inducible in response to a wide variety of pathogens including bacteria, fungus, and viruses. Recombinant BmTf protein produced in a baculovirus system exhibits iron binding capacity and antibacterial activity against various Gram-positive and -negative bacteria. Taken together, our results indicate that BmTf is an inducible immune effector molecule that may play an important role in pathogen clearance of insect innate immunity.

Cloning of the fibroin gene from the oak silkworm, Antheraea yamamai and its complete sequence

The nucleotide sequences containing an entire genomic region and 5′ upstream region of Antheraea yamamai fibroin gene have been determined. The gene consists of an initial exon encoding 14 amino acids, an intron (150 bp), and a long second exon coding for 2641 amino acids. The fibroin coding sequence shows a specialized organization with a highly repetitive region flanked by non repetitive 5′ and 3′ ends. Northern blot analyses confirmed that fibroin gene is actively expressed in the posterior silk gland of the final instar larvae of Antheraea yamamai.

Molecular characterization of a Bombyx mori protein disulfide isomerase (bPDI)

Abstract We have isolated a complementary deoxyribonucleic acid clone that encodes the protein disulfide isomerase of Bombyx mori (bPDI). This protein has a putative open reading frame of 494 amino acids and a predicted size of 55.6 kDa. In addition, 2 thioredoxin active sites, each with a CGHC sequence, and an endoplasmic reticulum (ER) retention signal site with a KDEL motif were found at the C-terminal. Both sites are typically found in members of the PDI family of proteins. The expression of bPDI messenger ribonucleic acid (mRNA) was markedly increased during ER stress induced by stimulation with calcium ionophore A23187, tunicamycin, and dithiothreitol, all of which are known to cause an accumulation of unfolded proteins in the ER. We also examined the tissue distribution of bPDI mRNA and found pronounced expression in the fat body of insects. Hormonal regulation studies showed that juvenile hormone, insulin, and a combination of juvenile hormone and transferrin (although not transferrin alone) affected bPDI mRNA expression. A challenge with exogenous bacteria also affected expression, and the effect peaked 16 hours after infection. These results suggest that bPDI is a member of the ER-stress protein group, that it may play an important role in exogenous bacterial infection of the fat body, and that its expression is hormone regulated.

Design of potent 9-mer antimicrobial peptide analogs of protaetiamycine and investigation of mechanism of antimicrobial action†

Protaetiamycine is an insect defensin, a naturally occurring 43‐amino‐acid‐residue antimicrobial peptide derived from the larvae of the beetle Protaetia brevitarsis. In a previous work that aimed at developing short antibiotic peptides, we designed 9‐mer peptide analogs of protaetiamycine. Among them, RLWLAIGRG‐NH2 showed good antifungal activity against Candida albicans. In this study, we designed four 9‐mer peptide analogs based on the sequence of RLWLAIGRG‐NH2, in which Gly or Ile was substituted with Arg, Lys, or Trp to optimize the balance between the hydrophobicity and cationicity of the peptides and to increase bacterial cell selectivity. We measured their toxicity to bacteria and mammalian cells as well as their ability to permeabilize model phospholipid membranes. Substitution of Arg for Gly9 at the C‐terminus (9Pbw1) resulted in two‐ to fourfold improvement in antibacterial activity. Further substitution of Gly7 with Lys (9Pbw2 and 9Pbw4) caused four‐ to eightfold improvement in the antibacterial activity without increase in cytotoxocity, while substitution of Gly7 with Trp (9Pbw3) increased cytotoxicity as well as antibacterial activity. The peptides 9Pbw2 and 9Pbw4 with the highest bacterial cell selectivity were not effective in depolarizing the membrane of Staphylococcus aureus cytoplasmic membranes and showed almost no leakage of a fluorescent dye entrapped within the vesicles. Gel‐retardation experiments indicated that 9Pbw2 and 9Pbw4 inhibited the migration of DNA at concentrations >20 µM. Three positively charged residues at the C‐terminus in 9Pbw2 and 9Pbw4 may facilitate effective penetration into the negatively charged phospholipid membrane of bacteria. The results obtained in this study suggest that the bactericidal action of our potent antibacterial peptides, namely 9Pbw2 and 9Pbw4, may be attributed to the inhibition of the functions of intracellular components after penetration of the bacterial cell membrane. Copyright

Oleic acid and linoleic acid from Tenebrio molitor larvae inhibit BACE1 activity in vitro: molecular docking studies.

In our ongoing research to find therapeutic compounds for Alzheimers disease (AD) from natural resources, the inhibitory activity of the BACE1 enzyme by Tenebrio molitor larvae and its major compounds were evaluated. The T. molitor larvae extract and its fractions exhibited strong BACE1 suppression. The major components of hexane fraction possessing both high yield and strong BACE1 inhibition were determined by thin layer chromatography, gas chromatography, and nuclear magnetic resonance analysis. A remarkable composition of unsaturated long chain fatty acids, including oleic acid and linoleic acid, were identified. Oleic acid, in particular, noncompetitively attenuated BACE1 activity with a half-maximal inhibitory concentration (IC₅₀) value of 61.31 μM and Ki value of 34.3 μM. Furthermore, the fatty acids were stably interacted with BACE1 at different allosteric sites of the enzyme bound with the OH of CYS319 and the NH₃ of TYR320 for oleic acid and with the C=O group of GLN304 for linoleic acid. Here, we first revealed novel pharmacophore features of oleic acids and linoleic acid to BACE1 by in silico docking studies. The present findings would clearly suggest potential guidelines for designing novel BACE1 selective inhibitors.

Antifungal effect and pore-forming action of lactoferricin B like peptide derived from centipede Scolopendra subspinipes mutilans

The centipede Scolopendra subspinipes mutilans has been a medically important arthropod species by using it as a traditional medicine for the treatment of various diseases. In this study, we derived a novel lactoferricin B like peptide (LBLP) from the whole bodies of adult centipedes, S. s. mutilans, and investigated the antifungal effect of LBLP. LBLP exerted an antifungal and fungicidal activity without hemolysis. To investigate the antifungal mechanism of LBLP, a membrane study with propidium iodide was first conducted against Candida albicans. The result showed that LBLP caused fungal membrane permeabilization. The assays of the three dimensional flow cytometric contour plot and membrane potential further showed cell shrinkage and membrane depolarization by the membrane damage. Finally, we confirmed the membrane-active mechanism of LBLP by synthesizing model membranes, calcein and FITC-dextran loaded large unilamellar vesicles. These results showed that the antifungal effect of LBLP on membrane was due to the formation of pores with radii between 0.74nm and 1.4nm. In conclusion, this study suggests that LBLP exerts a potent antifungal activity by pore formation in the membrane, eventually leading to fungal cell death.