Tick-Derived Peptide Blocks Potassium Channel TREK-1.

Ticks transmit a variety of pathogens, including rickettsia and viruses, when they feed on blood, afflicting humans and other animals. Bioactive components acting on inflammation, coagulation, and the immune system were reported to facilitate ticks' ability to suck blood and transmit tick-borne diseases. In this study, a novel peptide, IstTx, from an Ixodes scapularis cDNA library was analyzed. The peptide IstTx, obtained by recombinant expression and purification, selectively inhibited a potassium channel, TREK-1, in a dose-dependent manner, with an IC50 of 23.46 ± 0.22 µM. The peptide IstTx exhibited different characteristics from fluoxetine, and the possible interaction of the peptide IstTx binding to the channel was explored by molecular docking. Notably, extracellular acidification raised its inhibitory efficacy on the TREK-1 channel. Our results found that the tick-derived peptide IstTx blocked the TREK-1 channel and provided a novel tool acting on the potassium channel.

An insecticidal toxin from Nephila clavata spider venom.

Spiders are the most successful insect predators given that they use their venom containing insecticidal peptides as biochemical weapons for preying. Due to the high specificity and potency of peptidic toxins, discoveries of insecticidal toxins from spider venom have provided an opportunity to obtain natural compounds for agricultural applications without affecting human health. In this study, a novel insecticidal toxin (µ-NPTX-Nc1a) was identified and characterized from the venom of Nephila clavata. Its primary sequence is GCNPDCTGIQCGWPRCPGGQNPVMDKCVSCCPFCPPKSAQG which was determined by automated Edman degradation, cDNA cloning, and MS/MS analysis. BLAST search indicated that Nc1a shows no similarity with known peptides or proteins, indicating that Nc1a belongs to a novel family of insecticidal peptide. Nc1a displayed inhibitory effects on NaV and KV channels in cockroach dorsal unpaired median neurons. The median lethal dose (LD50) of Nc1a on cockroach was 573 ng/g. Herein, a study that identifies a novel insecticidal toxin, which can be a potential candidate and/or template for the development of bioinsecticides, is presented.

A novel antimicrobial peptide from skin secretions of the tree frog Theloderma kwangsiensis.

Most of amphibians belonging to family Rhacophoridae live in arboreal habitats. A large number of antimicrobial peptides (AMPs) have been identified from amphibian skins. No antimicrobial peptide from Rhacophoridae amphibians has been reported. In this study, we purified and characterized a novel antimicrobial peptide, pleurain-a1-thel from skin secretions of the tree frog, Theloderma kwangsiensis. Its amino acid sequence was determined as RILTMTKRVKMPQLYKQIVCRLFKTC by Edman degradation, mass spectrometry analysis and cDNA cloning. There are two cysteines, which form an intra-molecular disulfide bridge, in the sequence of pleurain-a1-thel. Pleurain-a1-thel exerted potential antimicrobial activities against wide spectrum of microorganisms, including Gram-negative and -positive bacteria and fungi. It exerted little hemolytic activity in human or rabbit red cells. To the best of our knowledge, this is the first report of antimicrobial peptide from Rhacophoridae amphibians.

Comparison of Fecal Antimicrobial Resistance Genes in Captive and Wild Asian Elephants.

The Asian elephant (Elephas maximus) is a flagship species of tropical rainforests, and it has generated much concern. In this case, the gut bacterial communities of captive and wild Asian elephants are particularly noteworthy. We aim to compare the differences in bacterial diversity and antibiotic resistance gene (ARG) subtypes in fecal samples of Asian elephants from different habitats, which may affect host health. Analyses reveal that differences in the dominant species of gut bacteria between captive and wild Asian elephants may result in significant differences in ARGs. Network analysis of bacterial communities in captive Asian elephants has identified potentially pathogenic species. Many negative correlations in network analysis suggest that different food sources may lead to differences in bacterial communities and ARGs. Results also indicate that the ARG levels in local captive breeding of Asian elephants are close to those of the wild type. However, we found that local captive elephants carry fewer ARG types than their wild counterparts. This study reveals the profile and relationship between bacterial communities and ARGs in different sources of Asian elephant feces, providing primary data for captive breeding and rescuing wild Asian elephants.

Characterization of a novel LTA/LPS-binding antimicrobial and anti-inflammatory temporin peptide from the skin of Fejervary limnocharis (Anura: Ranidae).

Septic shock caused by Gram-positive bacteria continues to be a major cause of morbidity and mortality in intensive care units globally. Most Temporins are excellent growth inhibitors of gram-positive bacteria and candidates for developing antimicrobial treatments due to their biological action and small molecular weight. In this study, a novel Temporin peptide from the skin of Fejervarya limnocharis frog, named as Temporin-FL, was characterized. Temporin-FL was found to adopt typical α-helical conformation in SDS solution and to exhibit selective antibacterial activity against Gram-positive bacteria through a membrane destruction mechanism. Accordingly, Temporin-FL showed protective effects against Staphylococcus aureus-induced sepsis in mice. Finally, Temporin-FL was demonstrated to exert anti-inflammatory effects by neutralizing the action of LPS/LTA and by inhibiting MAPK pathway activation. Therefore, Temporin-FL represents a novel candidate for moleculartherapy of Gram-positive bacterial sepsis.

Multiple Mechanistic Action of Brevinin-1FL Peptide against Oxidative Stress Effects in an Acute Inflammatory Model of Carrageenan-Induced Damage.

Amphibian skin is acknowledged to contain an antioxidant system composed of various gene-encoded antioxidant peptides, which exert significant effects on host defense. Nevertheless, recognition of such peptides is in its infancy so far. Here, we reported the antioxidant properties and underlying mechanism of a new antioxidant peptide, brevinin-1FL, identified from Fejervarya limnocharis frog skin. The cDNA sequence encoding brevinin-1FL was successfully cloned from the total cDNA of F. limnocharis and showed to contain 222 bp. The deduced mature peptide sequence of brevinin-1FL was FWERCSRWLLN. Functional analysis revealed that brevinin-1FL could concentration-dependently scavenge ABTS+, DPPH, NO, and hydroxyl radicals and alleviate iron oxidation. Besides, brevinin-1FL was found to show neuroprotective activity by reducing contents of MDA and ROS plus mitochondrial membrane potential, increasing endogenous antioxidant enzyme activity, and suppressing H2O2-induced death, apoptosis, and cycle arrest in PC12 cells which were associated with its regulation of AKT/MAPK/NF-κB signal pathways. Moreover, brevinin-1FL relieved paw edema, decreased the levels of TNF-α, IL-1ß, IL-6, MPO, and malondialdehyde (MDA), and restored catalase (CAT) and superoxide dismutase (SOD) activity plus glutathione (GSH) contents in the mouse injected by carrageenan. Together, these findings indicate that brevinin-1FL as an antioxidant has potent therapeutic potential for the diseases induced by oxidative damage. Meanwhile, this study will help us further comprehend the biological functions of amphibian skin and the mechanism by which antioxidants protect cells from oxidative stress.

Defensing role of novel piscidins from largemouth bass (Micropterus salmoides) with evidence of bactericidal activities and inducible expressional delineation.

Micropterus salmoides is an economical important species of freshwater-cultured fish, the in-depth knowledge of its immune system is in urgent development to cope with serious infectious diseases. Piscidin is an important antimicrobial peptide (AMP) family existing in almost all teleosts. However, no piscidin has been reported in largemouth bass. In this study, three novel piscidins (MSPiscidin-1, -2, and -3) were firstly identified and characterized from the largemouth bass. The predicted mature peptides of MSPiscidin-1, -2, and -3 (consists of 24, 27, 25 amino acid residues, respectively) all adopted an amphipathic α-helical conformation representative of cationic AMPs that are important for membrane permeabilization and antibacterial activity. MSPiscidin-2 and -3 indeed displayed strong, broad-spectrum, and highly efficient antimicrobial activities in vitro against aquatic pathogens, but MSPiscidin-1 didn't show direct antimicrobial activity. MSPiscidin-2 and -3 killed bacteria mainly by inducing membrane permeabilization, in addition, they also can interact with bacterial genomic DNA, which might influence the DNA replication and transcription. Besides, MSPiscidin-2 and -3 could effectively inhibit the formation of the bacterial biofilm and eliminate the preformed biofilms. In vivo, MSPiscidin-1-3 genes showed an inducible expression pattern in the tested tissues upon Vibrio harveyi infection, which further indicated the key roles of piscidins in innate immunity in largemouth bass. Overall, this study will supplement the understanding of M. salmoides innate immune system and provide candidates for the design of novel peptide antibacterial agents used in aquaculture.

Structures of a deltacoronavirus spike protein bound to porcine and human receptors.

Porcine deltacoronavirus (PDCoV) can experimentally infect a variety of animals. Human infection by PDCoV has also been reported. Consistently, PDCoV can use aminopeptidase N (APN) from different host species as receptors to enter cells. To understand this broad receptor usage and interspecies transmission of PDCoV, we determined the crystal structures of the receptor binding domain (RBD) of PDCoV spike protein bound to human APN (hAPN) and porcine APN (pAPN), respectively. The structures of the two complexes exhibit high similarity. PDCoV RBD binds to common regions on hAPN and pAPN, which are different from the sites engaged by two alphacoronaviruses: HCoV-229E and porcine respiratory coronavirus (PRCoV). Based on structure guided mutagenesis, we identified conserved residues on hAPN and pAPN that are essential for PDCoV binding and infection. We report the detailed mechanism for how a deltacoronavirus recognizes homologous receptors and provide insights into the cross-species transmission of PDCoV.

Snake Cathelicidin Derived Peptide Inhibits Zika Virus Infection.

Zika virus (ZIKV) is a mosquito-borne virus belonging to the genus Flavivirus and has reemerged in recent years with epidemic potential. ZIKV infection may result in severe syndromes such as neurological complications and microcephaly in newborns. Therefore, ZIKV has become a global public health threat and currently there is no approved specific drug for its treatment. Animal venoms are important resources of novel drugs. Cathelicidin-BF (BF-30) is a defensive peptide identified from Bungarus fasciatus snake venom and has been shown to be an excellent template for applicable peptide design. In this study, we found that ZY13, one of the peptidic analogs of BF-30, inhibits ZIKV infection in vitro and in vivo. Mechanistic studies revealed that ZY13 can directly inactivate ZIKV and reduce the production of infectious virions. Further studies also indicated that administration of ZY13 strengthen the host antiviral immunity via AXL-SOCS (suppressor of cytokine signaling protein) pathway. Additionally, the results of mouse experiment suggest that ZY13 efficiently restrict ZIKV infection and improve the growth defects of ZIKV-infected mouse pups. Together, our findings not only demonstrate that ZY13 might be a candidate for anti-ZIKV drug, but also indicated the importance of animal venom peptides as templates for antivirals development.

In Vitro and In Vivo Antimalarial Activity of LZ1, a Peptide Derived from Snake Cathelicidin.

Antimalarial drug resistance is an enormous global threat. Recently, antimicrobial peptides (AMPs) are emerging as a new source of antimalarials. In this study, an AMP LZ1 derived from snake cathelicidin was identified with antimalarial activity. In the in vitro antiplasmodial assay, LZ1 showed strong suppression of blood stage Plasmodium falciparum (P. falciparum) with an IC50 value of 3.045 µM. In the in vivo antiplasmodial assay, LZ1 exerted a significant antimalarial activity against Plasmodium berghei (P. berghei) in a dose- and a time- dependent manner. In addition, LZ1 exhibited anti-inflammatory effects and attenuated liver-function impairment during P. berghei infection. Furthermore, by employing inhibitors against glycolysis and oxidative phosphorylation in erythrocytes, LZ1 specifically inhibited adenosine triphosphate (ATP) production in parasite-infected erythrocyte by selectively inhibiting the pyruvate kinase activity. In conclusion, the present study demonstrates that LZ1 is a potential candidate for novel antimalarials development.

Centipede KCNQ Inhibitor SsTx Also Targets KV1.3.

It was recently discovered that Ssm Spooky Toxin (SsTx) with 53 residues serves as a key killer factor in red-headed centipede's venom arsenal, due to its potent blockage of the widely expressed KCNQ channels to simultaneously and efficiently disrupt cardiovascular, respiratory, muscular, and nervous systems, suggesting that SsTx is a basic compound for centipedes' defense and predation. Here, we show that SsTx also inhibits KV1.3 channel, which would amplify the broad-spectrum disruptive effect of blocking KV7 channels. Interestingly, residue R12 in SsTx extends into the selectivity filter to block KV7.4, however, residue K11 in SsTx replaces this ploy when toxin binds on KV1.3. Both SsTx and its mutant SsTx_R12A inhibit cytokines production in T cells without affecting the level of KV1.3 expression. The results further suggest that SsTx is a key molecule for defense and predation in the centipedes' venoms and it evolves efficient strategy to disturb multiple physiological targets.

An Antiviral Peptide from Alopecosa nagpag Spider Targets NS2B-NS3 Protease of Flaviviruses.

Flaviviruses are single-stranded RNA viruses predominantly transmitted by the widely distributed Aedes mosquitoes in nature. As important human pathogens, the geographic reach of Flaviviruses and their threats to public health are increasing, but there is currently no approved specific drug for treatment. In recent years, the development of peptide antivirals has gained much attention. Natural host defense peptides which uniquely evolved to protect the hosts have been shown to have antiviral properties. In this study, we firstly collected the venom of the Alopecosa nagpag spider from Shangri-La County, Yunnan Province. A defense peptide named Av-LCTX-An1a (Antiviral-Lycotoxin-An1a) was identified from the spider venom, and its anti-dengue serotype-2 virus (DENV2) activity was verified in vitro. Moreover, a real-time fluorescence-based protease inhibition assay showed that An1a functions as a DENV2 NS2B-NS3 protease inhibitor. Furthermore, we also found that An1a restricts zika virus (ZIKV) infection by inhibiting the ZIKV NS2B-NS3 protease. Together, our findings not only demonstrate that An1a might be a candidate for anti-flavivirus drug but also indicate that spider venom is a potential resource library rich in antiviral precursor molecules.

Joannsin, a novel Kunitz-type FXa inhibitor from the venom of Prospirobolus joannsi.

The repugnatorial glands of millipedes release various defensive chemical secretions. Although varieties of such defensive secretions have been studied, none of them is protein or peptide. Herein, a novel factor Xa (FXa) inhibitor named joannsin was identified and characterised from repugnatorial glands of Prospirobolus joannsi. Joannsin is composed of 72 amino acid residues including six cysteines, which form three intra-molecular disulfide bridges. It is a member of Kunitz-type protease inhibitor family, members of which are also found in the secretory glands of other arthropods. Recombinant joannsin exhibited remarkable inhibitory activity against trypsin and FXa with a Ki of 182.7 ± 14.6 and 29.5 ± 4.7 nM, respectively. Joannsin showed strong anti-thrombosis functions in vitro and in vivo. Joannsin is the first peptide component in millipede repugnatorial glands to be identified and is a potential candidate and/or template for the development of anti-thrombotic agents. These results also indicated that there is Kunitz-type protease inhibitor toxin in millipede repugnatorial glands as in other arthropods secretory glands.

An Immunosuppressant Peptide from the Hard Tick Amblyomma variegatum.

Ixodid ticks are well known for spreading transmitted tick-borne pathogens while being attached to their hosts for almost 1-2 weeks to obtain blood meals. Thus, they must secrete many immunosuppressant factors to combat the hosts' immune system. In the present work, we investigated an immunosuppressant peptide of the hard tick Amblyomma variegatum. This peptide, named amregulin, is composed of 40 residues with an amino acid sequence of HLHMHGNGATQVFKPRLVLKCPNAAQLIQPGKLQRQLLLQ. A cDNA of the precursor peptide was obtained from the National Center for Biotechnology Information (NCBI, Bethesda, MD, USA). In rat splenocytes, amregulin exerts significant anti-inflammatory effects by inhibiting the secretion of inflammatory factors in vitro, such as tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), interleukin-8 (IL-8) and interferon-gamma (IFN-γ). In rat splenocytes, treated with amregulin, compared to lipopolysaccharide (LPS) alone, the inhibition of the above inflammatory factors was significant at all tested concentrations (2, 4 and 8 µg/mL). Amregulin shows strong free radical scavenging and antioxidant activities (5, 10 and 20 µg/mL) in vitro. Amregulin also significantly inhibits adjuvant-induced paw inflammation in mouse models in vivo. This peptide may facilitate the ticks' successful blood feeding and may lead to host immunotolerance of the tick. These findings have important implications for the understanding of tick-host interactions and the co-evolution between ticks and the viruses that they bear.

Peptidomics combined with cDNA library unravel the diversity of centipede venom.

Centipedes are one of the oldest venomous arthropods using toxin as their weapon to capture prey. But little attention was focused on them and only few centipede toxins were demonstrated with activity on ion channels. Therefore, more deep works are needed to understand the diversity of centipede venom. In the present study, we use peptidomics combined with cDNA library to uncover the diversity of centipede Scolopendra subspinipes mutilans L. Koch. 192 peptides were identified by LC-MS/MS and 79 precursors were deduced by cDNA library. Surprisingly, the signal peptides of centipede toxins were more complicated than any other animal toxins and even exhibited large differences in homologues. Meanwhile, a large number of variants generated by alternative cleavage sites were detected by mass spectra. Odd number of cystein (3, 5, 7) found in the mature peptides were seldom seen in peptide toxins. In additional, two novel cysteine frameworks (C-C-C-CCC, C-C-C-C-CC-CC) were identified from 16 different cysteine frameworks from centipede peptides. Only 29 precursors have clear targets, while others may provide a potential diversity function for centipede. These findings highlight the extensive diversity of centipede toxins and provide powerful tools to understand the capture and defense weapon of centipede. BIOLOGICAL SIGNIFICANCE: Peptide toxins from venomous animal have attracted increasing attentions due to their extraordinary chemical and pharmacological diversity. Centipedes are one of the most used Chinese traditional medicines, but little was known about the active components. The venom of Scolopendra subspinipes mutilans L. Koch is first deeply analyzed in this work and most of peptides were never discovered before. Interestingly, the number and arrangement of cysteine showed a larger different to known peptide toxins such spider or scorpion toxins. Moreover, only 29 peptides from this centipede venom were identified with known function. It suggested that our work not only important to understand the composition of centipede venom, but also provide many valuable peptides for potential biological functions.

A novel 26RFa peptide containing both analgesic and anti-inflammatory functions from Chinese tree shrew.

26RFa is one of neuroendocrine peptide groups in the RFamide peptide family containing conserved Arg-Phe/Tyr-NH2 motif at their C-terminus. They exert multiple biological functions in vertebrates. A novel 26RFa peptide (TC26RFa) with unique structure is identified from the tree shrew of Tupaia belangeri chinensis in the present study. In structure, different from other 26RFa peptides containing conserved Phe-Arg-Phe-NH2 motif at their C-terminus, there is a Phe-Arg-Tyr-NH2 C-terminus in TC26RFa. It has been found that TC26RFa of intraperitoneal injection exerts strong analgesic activities in several mice models including acetic acid-induced abdominal writhing, formalin-induced paw licking, and thermal pain-induced tail withdrawal. It shows comparable analgesic ability with morphine. In addition, this peptide has been found to inhibit inflammatory factor secretion (including tumor necrosis factor-α, interleukin-6, and interleukin-1ß) induced by lipopolysaccharides (LPS). Furthermore, it stimulates secretion of the anti-inflammatory factor, interleukin-10. In addition to the identification of a novel 26RFa peptide from tree shrew, a new type of function (anti-inflammation) involved in 26RFa peptide is discovered.

A novel neurotoxin from venom of the spider, Brachypelma albopilosum.

Spiders have evolved highly selective toxins for insects. There are many insecticidal neurotoxins in spider venoms. Although a large amount of work has been done to focus on neurotoxicity of spider components, little information, which is related with effects of spider toxins on tumor cell proliferation and cytotoxicity, is available for Brachypelma albopilosum venom. In this work, a novel spider neurotoxin (brachyin) was identified and characterized from venoms of the spider, Brachypelma albopilosum. Brachyin is composed of 41 amino acid residues with the sequence of CLGENVPCDKDRPNCCSRYECLEPTGYGWWYASYYCYKKRS. There are six cysteines in this sequence, which form three disulfided bridges. The serine residue at the C-terminus is amidated. Brachyin showed strong lethal effects on American cockroaches (Periplaneta americana) and Tenebrio molitor (common mealbeetle). This neurotoxin also showed significant analgesic effects in mice models including abdominal writhing induced by acetic acid and formalin-induced paw licking tests. It was interesting that brachyin exerted marked inhibition on tumor cell proliferation.

A Novel Insulinotropic Peptide from the Skin Secretions of Amolops loloensis Frog.

Various kinds of biologically active peptides have previously been isolated from the skin secretions of Amolops loloensis frog, such as antimicrobial peptides, bradykinin-like peptides and algesic peptides. A novel insulinotropic peptide named amolopin was identified in A. loloensis frog's skin secretion. Its primary structure sequence was determined by Edman degradation as: FLPIVGKSLSGLSGKL-NH2. BLAST search indicates that the amino acid sequence of amolopin is quite different from other known insulin secretagogues, including mastoparan, exendins and α-latrotoxin, nor does it like incretins (e.g. glucagons like peptide-1 and glucose-dependent insulinotropic ploypeptide) either. However, amolopin shows certain structural similarity with amphibian antimicrobial temporins and vespid chemotactic peptides isolated from Vespa magnifica. Amolopin can stimulate insulin release in INS-1 cells in a dose-dependent manner. Primary investigation on its action mechanisms reveals that amolopin does not increase the influx of Ca(2+). In conclusion, a novel 16-amino acid peptide with insulin-releasing activity is initially discovered from the skin secretion of A. loloensis frog. Further work is necessary to evaluate its potential as novel anti-diabetic candidate.

[Functional identification and application of horsefly as a representative form of traditional Chinese medicine].

As important traditional Chinese medicine materials, medicinal animals have been highly appreciated due to their strong bioactivities. Among these, medicinal insects have been thought to be significant, especially in preventing and treating modern diseases and tumors. Some of the most famous medicinal insects, such as horseflies, blister beetles and American cockroaches (Periplaneta americana) have been well known due to their reported effects in anti-thrombosis and fighting cancer. In general, identifying the medicinal functions and active components of medicinal insects has been a gradual processes. Originally, these medicinal insects were collected from open fields and usually their whole bodies were adopted. But, currently, most medicinal insects are under large-scale artificial propagations and only their purified active components are in use. In this article, we reviewed the historical process of the application of the horsefly in traditional Chinese medicine and tried to provide useful references for the modernization of traditional Chinese medicines via discussing the interrelationship between traditional Chinese medicine and western medicine.