Bioactive Peptides and Proteins from Centipede Venoms

Venoms are a complex cocktail of biologically active molecules, including peptides, proteins, polyamide, and enzymes widely produced by venomous organisms. Through long-term evolution, venomous animals have evolved highly specific and diversified peptides and proteins targeting key physiological elements, including the nervous, blood, and muscular systems. Centipedes are typical venomous arthropods that rely on their toxins primarily for predation and defense. Although centipede bites are frequently reported, the composition and effect of centipede venoms are far from known. With the development of molecular biology and structural biology, the research on centipede venoms, especially peptides and proteins, has been deepened. Therefore, we summarize partial progress on the exploration of the bioactive peptides and proteins in centipede venoms and their potential value in pharmacological research and new drug development.

Centipede Venom: A Potential Source of Ion Channel Modulators

Centipedes are one of the most ancient and successful living venomous animals. They have evolved spooky venoms to deter predators or hunt prey, and are widely distributed throughout the world besides Antarctica. Neurotoxins are the most important virulence factor affecting the function of the nervous system. Ion channels and receptors expressed in the nervous system, including Na_V, K_V, Ca_V, and TRP families, are the major targets of peptide neurotoxins. Insight into the mechanism of neurotoxins acting on ion channels contributes to our understanding of the function of both channels and centipede venoms. Meanwhile, the novel structure and selective activities give them the enormous potential to be modified and exploited as research tools and biological drugs. Here, we review the centipede venom peptides that act on ion channels.

A novel ω-conotoxin Bu8 inhibiting N-type voltage-gated calcium channels displays potent analgesic activity

ω-Conotoxins inhibit N-type voltage-gated calcium (Ca_V2.2) channels and exhibit efficacy in attenuating neuropathic pain but have a low therapeutic index. Here, we synthesized and characterized a novel ω-conotoxin, Bu8 from Conus bullatus, which consists of 25 amino acid residues and three disulfide bridges. Bu8 selectively and potently inhibits depolarization-activated Ba²⁺ currents mediated by rat Ca_V2.2 expressed in HEK293T cells (IC₅₀ = 89 nmol/L). Bu8 is two-fold more potent than ω-conotoxin MVIIA, a ω-conotoxin currently used for the treatment of severe chronic pain. It also displays potent analgesic activity in animal pain models of hot plate and acetic acid writhing but has fewer side effects on mouse motor function and lower toxicity in goldfish. Its lower side effects may be attributed to its faster binding rate and higher recovery ratios. The NMR structure demonstrates that Bu8 contains a small irregular triple β-strand. The structure-activity relationships of Bu8 Ala mutants and Bu8/MVIIA hybrid mutants demonstrate that the binding mode of Ca_V2.2 with the amino acid residues in loop 1 and loop 2 of Bu8 is different from that of MVIIA. This study characterizes a novel, more potent ω-conotoxin and provides new insights for designing Ca_V2.2 antagonists.

Uncovering the mechanisms of leech and centipede granules in the treatment of diabetes mellitus-induced erectile dysfunction utilising network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus-induced erectile dysfunction (DMED) is one of the most common complications of diabetes mellitus. Leech and centipede granules (LCG) have traditionally been used as blood-activating agents in various ethnomedicinal systems of East Asia, especially in China. It is often used to regulate bodily functions and considered as adjuvant therapy for promoting blood circulation, alleviating blood coagulation, activating meridians, and relieving stasis.

AIM OF THE STUDY

This study aimed to identify potential genes and mechanisms of LCG on DMED from the network pharmacological perspective.

MATERIALS AND METHODS

The active components of LCG were identified by UHPLC-Q-TOF-MS, TCMID, and the BATMAN-TCM databases, and the disease targets of DMED were obtained from the DisGeNET, CooLGeN, GeneCards databases. After identifying DMED targets of LCG, a protein-protein interaction (PPI) network was constructed. Hub genes and significant modules were identified via the MCODE plug-in of Cytoscape software. Then, significant signaling pathways of the modules were identified using the Metascape database. The probable interaction mode of compounds-hub genes is examined using Molecular Operating Environment (MOE) docking software. Besides, we investigated the effects and mechanisms of LCG on improving erectile function in the streptozotocin (STZ)-induced diabetic rats model.

RESULTS

Combined UHPLC-Q-TOF-MS analysis with network pharmacology study, 18 active compounds were selected for target prediction. There are 97 common target genes between LCG and DMED. Enrichment of the KEGG pathway mainly involves in the calcium signaling pathway, NF-kappa B signaling pathway, cGMP-PKG signaling pathway, HIF-1 signaling pathway, PI3K-Akt signaling pathway, and mTOR signaling pathway. Nine hub genes were regulated by LCG in DMED, including CXCL8, NOS3, CRH, TH, BDNF, DRD4, ACE, CNR1, and HTR1A. The results of molecular docking analysis showed that the tyrosin, ursolic acid, and L-Histidine has a relatively stable interaction with corresponding hub genes via generating hydrogen bonds, H-π, and π-π interactions. Significantly, the results in docking predicted a higher affinity of vardenafil to the hub genes compared to the tyrosin, ursolic acid, and L-Histidine. Furthermore, LCG increased the testosterone, erection frequency, the ratio of ICP and MAP, SOD, cGMP, cAMP as well as decreased the MDA, and AGEs expression levels. And, LCG ameliorated the histological change of penile tissues in DMED rats. Hence, LCG attenuates oxidative stress, increases NO production; For the mechanism exploration, LCG could significantly upregulate the mRNA and protein expression of CNR1, NOS3, CRH, TH, BDNF, and DRD4, whereas CXCL8, ACE, and HTR1A levels were significantly higher than those in the DMED group. Moreover, LCG activates the NO/cGMP/PKG pathway, PI3K/Akt/nNOS pathway, cAMP/PKA pathway, and inhibits the HIF-1α/mTOR pathway to improve erectile function.

CONCLUSIONS

Our results suggest that LCG maybe offer a new therapeutic basis for the treatment of DMED via altering the gene expression of involved metabolic pathways.

Application for proteomics analysis technology in studying animal-derived traditional Chinese medicine: A review

Different therapeutically active ingredients, from plants, animals, and mineral sources, are prescribed as traditional Chinese medicines (TCM). TCMs, from animal sources, are rich in proteins and peptides. Different advanced proteomics technologies, such as two-dimensional gel electrophoresis (2-DE), multi-dimensional liquid chromatography (MDLC), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), and isobaric tags for relative and absolute quantitation (iTRAQ), have been applied to analyze TCMs, from animal sources. This paper reviews the common proteomic techniques for analyzing animal - derived TCMs. Various scientific studies have reported the application of proteomics for locating drug targets, identifying active components, and elucidating the mechanisms of action of animal - derived TCMs. However, these researches are still at the preliminary stage. This review has also discussed the existing challenges and future directions in this field of research.

Comparative analysis of diverse toxins from a new pharmaceutical centipede, Scolopendra mojiangica

As the oldest venomous animals, centipedes use their venom as a weapon to attack prey and for protection. Centipede venom, which contains many bioactive and pharmacologically active compounds, has been used for centuries in Chinese medicine, as shown by ancient records. Based on comparative analysis, we revealed the diversity of and differences in centipede toxin-like molecules between Scolopendra mojiangica, a substitute pharmaceutical material used in China, and S. subspinipes mutilans. More than 6 000 peptides isolated from the venom were identified by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and inferred from the transcriptome. As a result, in the proteome of S. mojiangica, 246 unique proteins were identified: one in five were toxin-like proteins or putative toxins with unknown function, accounting for a lower percentage of total proteins than that in S. mutilans. Transcriptome mining identified approximately 10 times more toxin-like proteins, which can characterize the precursor structures of mature toxin-like peptides. However, the constitution and quantity of the toxin transcripts in these two centipedes were similar. In toxicity assays, the crude venom showed strong insecticidal and hemolytic activity. These findings highlight the extensive diversity of toxin-like proteins in S. mojiangica and provide a new foundation for the medical-pharmaceutical use of centipede toxin-like proteins.

The complete mitochondrial genome sequence of Scolopendra mutilans L. Koch, 1878 (Scolopendromorpha, Scolopendridae), with a comparative analysis of other centipede genomes

Scolopendramutilans L. Koch, 1878 is an important Chinese animal with thousands of years of medicinal history. However, the genomic information of this species is limited, which hinders its further application. Here, the complete mitochondrial genome (mitogenome) of S.mutilans was sequenced and assembled by next-generation sequencing. The genome is 15,011 bp in length, consisting of 13 protein-coding genes (PCGs), 14 tRNA genes, and two rRNA genes. Most PCGs start with the ATN initiation codon, and all PCGs have the conventional stop codons TAA and TAG. The S.mutilans mitogenome revealed nine simple sequence repeats (SSRs), and an obviously lower GC content compared with other seven centipede mitogenomes previously sequenced. After analysis of homologous regions between the eight centipede mitogenomes, the S.mutilans mitogenome further showed clear genomic rearrangements. The phylogenetic analysis of eight centipedes using 13 conserved PCG genes was finally performed. The phylogenetic reconstructions showed Scutigeromorpha as a separate group, and Scolopendromorpha in a sister-group relationship with Lithobiomorpha and Geophilomorpha. Collectively, the S.mutilans mitogenome provided new genomic resources, which will improve its medicinal research and applications in the future.

Centipede Venom Peptides Acting on Ion Channels

Centipedes are among the oldest venomous arthropods that use their venom to subdue the prey. The major components of centipede venom are a variety of low-molecular-weight peptide toxins that have evolved to target voltage-gated ion channels to interfere with the central system of prey and produce pain or paralysis for efficient hunting. Peptide toxins usually contain several intramolecular disulfide bonds, which confer chemical, thermal and biological stability. In addition, centipede peptides generally have novel structures and high potency and specificity and therefore hold great promise both as diagnostic tools and in the treatment of human disease. Here, we review the centipede peptide toxins with reported effects on ion channels, including Nav, Kv, Cav and the nonselective cation channel polymodal transient receptor potential vanilloid 1 (TRPV1).

Couplet medicines of leech and centipede granules improve erectile dysfunction via inactivation of the CaSR/PLC/PKC signaling in streptozotocin-induced diabetic rats

Erectile dysfunction (ED) is one of the significant complications of diabetes mellitus (DM), and CASR plays an important role in cellular antiapoptosis and NO production in the vascular endothelium by activating PKC. The present study was aimed to investigate the efficacy of Leech and Centipede Granules (LCG) through the CaSR/PLC/PKC signaling. Fifty male Sprague-Dawley rats were treated with streptozotocin to induce the DM model. After 10 weeks, an apomorphine test was used to confirm DMED. Rats with DMED were administrated with LCG and U73122 for 4 weeks. Fasting blood glucose, body weight, insulin and glucagon levels were measured. Erectile function in rats was assessed by apomorphine. Serums were measured using enzyme-linked immunosorbent assay and flow cytometry, and penile tissues were harvested for histologic and the expression of related targets analyses. After treatment, fasting blood glucose, body weight, insulin, glucagon levels, and erectile function were significantly ameliorated in the LCG groups. The LOX-1, NOX, and EMPs concentrations were significantly decreased with LCG treatment. LCG also continuously increased NO and decreased ET-1 content in penile tissues. LCG and U73122 administration also improved penile fibrosis by significantly decreasing VCAM-1, ICAM-1, and CD62P. The data also showed that LCG reduced the apoptosis level in the penis. Furthermore, the inhibited activation of the CaSR/PLC/PKC pathway was observed in DMED rats with LCG treatment. Collectively, LCG significantly ameliorated erectile function of DMED rats via increased NO generation, inhibiting endothelial cells apoptosis and penile fibrosis, which might benefit from the suppression of CaSR/PLC/PKC pathway in DMED rats.

Parallel Evolution of Complex Centipede Venoms Revealed by Comparative Proteotranscriptomic Analyses

Centipedes are among the most ancient groups of venomous predatory arthropods. Extant species belong to five orders, but our understanding of the composition and evolution of centipede venoms is based almost exclusively on one order, Scolopendromorpha. To gain a broader and less biased understanding we performed a comparative proteotranscriptomic analysis of centipede venoms from all five orders, including the first venom profiles for the orders Lithobiomorpha, Craterostigmomorpha, and Geophilomorpha. Our results reveal an astonishing structural diversity of venom components, with 93 phylogenetically distinct protein and peptide families. Proteomically-annotated gene trees of these putative toxin families show that centipede venom composition is highly dynamic across macroevolutionary timescales, with numerous gene duplications as well as functional recruitments and losses of toxin gene families. Strikingly, not a single family is found in the venoms of representatives of all five orders, with 67 families being unique for single orders. Ancestral state reconstructions reveal that centipede venom originated as a simple cocktail comprising just four toxin families, with very little compositional evolution happening during the approximately 50 My before the living orders had diverged. Venom complexity then increased in parallel within the orders, with scolopendromorphs evolving particularly complex venoms. Our results show that even venoms composed of toxins evolving under the strong constraint of negative selection can have striking evolutionary plasticity on the compositional level. We show that the functional recruitments and losses of toxin families that shape centipede venom arsenals are not concentrated early in their evolutionary history, but happen frequently throughout.

Inhibition of Kv2.1 Potassium Channels by MiDCA1, A Pre-Synaptically Active PLA2-Type Toxin from Micrurus dumerilii carinicauda Coral Snake Venom

MiDCA1, a phospholipase A2 (PLA2) neurotoxin isolated from Micrurus dumerilii carinicauda coral snake venom, inhibited a major component of voltage-activated potassium (Kv) currents (41 ± 3% inhibition with 1 μM toxin) in mouse cultured dorsal root ganglion (DRG) neurons. In addition, the selective Kv2.1 channel blocker guangxitoxin (GxTx-1E) and MiDCA1 competitively inhibited the outward potassium current in DRG neurons. MiDCA1 (1 µM) reversibly inhibited the Kv2.1 current by 55 ± 8.9% in a Xenopus oocyte heterologous system. The toxin showed selectivity for Kv2.1 channels over all the other Kv channels tested in this study. We propose that Kv2.1 channel blockade by MiDCA1 underlies the toxin's action on acetylcholine release at mammalian neuromuscular junctions.

KV channels and the regulation of vascular smooth muscle tone

VSMCs in resistance arteries and arterioles express a diverse array of K_V channels with members of the K_V 1, K_V 2 and K_V 7 families being particularly important. Members of the K_V channel family: (i) are highly expressed in VSMCs; (ii) are active at the resting membrane potential of VSMCs in vivo (-45 to -30 mV); (iii) contribute to the negative feedback regulation of VSMC membrane potential and myogenic tone; (iv) are activated by cAMP-related vasodilators, hydrogen sulfide and hydrogen peroxide; (v) are inhibited by increases in intracellular Ca²⁺ and vasoconstrictors that signal through G_q -coupled receptors; (vi) are involved in the proliferative phenotype of VSMCs; and (vii) are modulated by diseases such as hypertension, obesity, the metabolic syndrome and diabetes. Thus, K_V channels participate in every aspect of the regulation of VSMC function in both health and disease.

Proteotranscriptomic Analysis and Discovery of the Profile and Diversity of Toxin-like Proteins in Centipede

Centipedes are one of the oldest venomous animals and use their venoms as weapons to attack prey or protect themselves. Their venoms contain various components with different biomedical and pharmacological properties. However, little attention has been paid to the profiles and diversity of their toxin-like proteins/peptides. In this study, we used a proteotranscriptomic approach to uncover the diversity of centipede toxin-like proteins in Scolopendra subspinipes mutilans Nine hundred twenty-three and 6,736 peptides, which were separately isolated from venom and torso tissues, respectively, were identified by ESI-MS/MS and deduced from their transcriptomes. Finally, 1369 unique proteins were identified in the proteome, including 100 proteins that exhibited overlapping expression in venom and torso tissues. Of these proteins, at least 40 proteins were identified as venom toxin-like proteins. Meanwhile, transcriptome mining identified ∼10-fold more toxin-like proteins and enabled the characterization of the precursor architecture of mature toxin-like peptides. Importantly, combined with proteomic and transcriptomic analyses, 25 toxin-like proteins/peptides (neurotoxins accounted for 50%) were expressed outside the venom gland and involved in gene recruitment processes. These findings highlight the extensive diversity of centipede toxin-like proteins and provide a new foundation for the medical-pharmaceutical use of centipede toxin-like proteins. Moreover, we are the first group to report the gene recruitment activity of venom toxin-like proteins in centipede, similar to snakes.

Animal Toxins Providing Insights into TRPV1 Activation Mechanism

Beyond providing evolutionary advantages, venoms offer unique research tools, as they were developed to target functionally important proteins and pathways. As a key pain receptor in the nociceptive pathway, transient receptor potential vanilloid 1 (TRPV1) of the TRP superfamily has been shown to be a target for several toxins, as a way of producing pain to deter predators. Importantly, TRPV1 is involved in thermoregulation, inflammation, and acute nociception. As such, toxins provide tools to understand TRPV1 activation and modulation, a critical step in advancing pain research and the development of novel analgesics. Indeed, the phytotoxin capsaicin, which is the spicy chemical in chili peppers, was invaluable in the original cloning and characterization of TRPV1. The unique properties of each subsequently characterized toxin have continued to advance our understanding of functional, structural, and biophysical characteristics of TRPV1. By building on previous reviews, this work aims to provide a comprehensive summary of the advancements made in TRPV1 research in recent years by employing animal toxins, in particular DkTx, RhTx, BmP01, Echis coloratus toxins, APHCs and HCRG21. We examine each toxin’s functional aspects, behavioral effects, and structural features, all of which have contributed to our current knowledge of TRPV1. We additionally discuss the key features of TRPV1’s outer pore domain, which proves to be the target of the currently discussed toxins.

Arthropod toxins acting on neuronal potassium channels

Arthropod venoms are a rich mixture of biologically active compounds exerting different physiological actions across diverse phyla and affecting multiple organ systems including the central nervous system. Venom compounds can inhibit or activate ion channels, receptors and transporters with high specificity and affinity providing essential insights into ion channel function. In this review, we focus on arthropod toxins (scorpions, spiders, bees and centipedes) acting on neuronal potassium channels. A brief description of the K⁺ channels classification and structure is included and a compendium of neuronal K⁺ channels and the arthropod toxins that modify them have been listed. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

A New 1,5-Dihydroxy-4-methoxyisoquinoline from Scolopendra subspinipes mutilans

A new isoquinoline, 1,5-dihydroxy-4-methoxyisoquinoline (1), was obtained from Scolopendra subspinipes mutilans. Compound 1 showed moderate cytotoxicity on tumour cells with IC₅₀ values ranging from 13 to 26 μm against five esophageal squamous cancer cells whereas low cytotoxicity against normal human esophageal epithelial cells. Isoquinoline ring oxidized at C(1), C(4), and C(5) can enhance its cytotoxicity. In addition, compound 1 showed potent inhibitory effect (inhibition rate > 50% at 13 μm) on cell migration in human umbilical vein endothelial cells. This article mainly studies the structure and activity of 1, and more modification of 1 as a potential anticancer agent.

Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles

Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.

Centipede venom peptide SsmTX-I with two intramolecular disulfide bonds shows analgesic activities in animal models

Pain is a major symptom of many diseases and results in enormous pressures on human body or society. Currently, clinically used analgesic drugs, including opioids and nonsteroidal anti-inflammatory drugs, have adverse reactions, and thus, the development of new types of analgesic drug candidates is urgently needed. Animal venom peptides have proven to have potential as new types of analgesic medicine. In this research, we describe the isolation and characterization of an analgesic peptide from the crude venom of centipede, Scolopendra subspinipes mutilans. The amino acid sequence of this peptide was identical with SsmTX-I that was previously reported as a specific Kv2.1 ion channel blocker. Our results revealed that SsmTX-I was produced by posttranslational processing of a 73-residue prepropeptide. The intramolecular disulfide bridge motifs of SsmTX-I was Cys1-Cys3 and Cys2-Cys4. Functional assay revealed that SsmTX-I showed potential analgesic activities in formalin-induced paw licking, thermal pain, and acetic acid-induced abdominal writhing mice models. Our research provides the first report of cDNA sequences, disulfide motif, successful synthesis, and analgesic potential of SsmTX-I for the development of pain-killing drugs. It indicates that centipede peptide toxins could be a treasure trove for the search of novel analgesic drug candidates. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Centipede venoms as a source of drug leads

INTRODUCTION

Centipedes are one of the oldest and most successful lineages of venomous terrestrial predators. Despite their use for centuries in traditional medicine, centipede venoms remain poorly studied. However, recent work indicates that centipede venoms are highly complex chemical arsenals that are rich in disulfide-constrained peptides that have novel pharmacology and three-dimensional structure. Areas covered: This review summarizes what is currently known about centipede venom proteins, with a focus on disulfide-rich peptides that have novel or unexpected pharmacology that might be useful from a therapeutic perspective. The authors also highlight the remarkable diversity of constrained three-dimensional peptide scaffolds present in these venoms that might be useful for bioengineering of drug leads. Expert opinion: Like most arthropod predators, centipede venoms are rich in peptides that target neuronal ion channels and receptors, but it is also becoming increasingly apparent that many of these peptides have novel or unexpected pharmacological properties with potential applications in drug discovery and development.

Clinical consequences of centipede bite: Is it neurotoxic?

The primary purpose of this article was to review the current literature regarding the clinical consequences of centipede envenomation in humans, in order to determine whether the bite of these arthropods is neurotoxic to humans or not. A thorough search of the literature regarding the clinical consequences of centipede bites in humans was applied, with great respect to neurological symptoms potentially caused by such bites. Centipede bite commonly causes only local reactions, which usually resolve within a few days without sequelae. The patients in the majority of centipede envenomations describe a painful but benign syndrome. However, mild constitutional symptoms are relatively frequent. Remarkably, centipedes can rarely cause severe systematic reactions such as anaphylaxis or even hypotension and myocardial ischemia. Factors such as patient age, comorbidity, anatomic site of envenomation, and size/species of centipede should be considered when evaluating a centipede envenomation victim. According to the current literature, the centipede bite does not seem to be neurotoxic to humans. However, it commonly causes symptoms mediated by the nervous system. These include local and generalized symptoms, with the first dominated by sensory disturbances and the second by non-specific symptoms such as headache, anxiety and presyncope. Based on our results, the answer to our study’s question is negative. The centipede bite is not neurotoxic to humans. However, it commonly causes symptoms mediated by the nervous system, which include primarily local pain and sensory disturbances, as well as generalized non-specific symptoms such as headache, anxiety and vagotonia.

SP6616 as a new Kv2.1 channel inhibitor efficiently promotes β-cell survival involving both PKC/Erk1/2 and CaM/PI3K/Akt signaling pathways

Kv2.1 as a voltage-gated potassium (Kv) channel subunit has a pivotal role in the regulation of glucose-stimulated insulin secretion (GSIS) and pancreatic β-cell apoptosis, and is believed to be a promising target for anti-diabetic drug discovery, although the mechanism underlying the Kv2.1-mediated β-cell apoptosis is obscure. Here, the small molecular compound, ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate (SP6616) was discovered to be a new Kv2.1 inhibitor. It was effective in both promoting GSIS and protecting β cells from apoptosis. Evaluation of SP6616 on either high-fat diet combined with streptozocin-induced type 2 diabetic mice or db/db mice further verified its efficacy in the amelioration of β-cell dysfunction and glucose homeostasis. SP6616 treatment efficiently increased serum insulin level, restored β-cell mass, decreased fasting blood glucose and glycated hemoglobin levels, and improved oral glucose tolerance. Mechanism study indicated that the promotion of SP6616 on β-cell survival was tightly linked to its regulation against both protein kinases C (PKC)/extracellular-regulated protein kinases 1/2 (Erk1/2) and calmodulin(CaM)/phosphatidylinositol 3-kinase(PI3K)/serine/threonine-specific protein kinase (Akt) signaling pathways. To our knowledge, this may be the first report on the underlying pathway responsible for the Kv2.1-mediated β-cell protection. In addition, our study has also highlighted the potential of SP6616 in the treatment of type 2 diabetes.

Centipede venoms and their components: resources for potential therapeutic applications

Venomous animals have evolved with sophisticated bio-chemical strategies to arrest prey and defend themselves from natural predators. In recent years, peptide toxins from venomous animals have drawn considerable attention from researchers due to their surprising chemical, biochemical, and pharmacological diversity. Similar to other venomous animals, centipedes are one of the crucial venomous arthropods that have been used in traditional medicine for hundreds of years in China. Despite signifying pharmacological importance, very little is known about the active components of centipede venoms. More than 500 peptide sequences have been reported in centipede venomous glands by transcriptome analysis, but only a small number of peptide toxins from centipede has been functionally described. Like other venomous animals such as snakes, scorpions, and spiders, the venom of centipedes could be an excellent source of peptides for developing drugs for treatments as well as bio-insecticides for agrochemical applications. Although centipede venoms are yet to be adequately studied, the venom of centipedes as well as their components described to date, should be compiled to help further research. Therefore, based on previous reports, this review focusses on findings and possible therapeutic applications of centipede venoms as well as their components.

A pain-inducing centipede toxin targets the heat activation machinery of nociceptor TRPV1

The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's heat activation machinery to cause powerful heat activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 heat activation, therefore providing crucial new structural information on the heat activation machinery.

Proteomic characterization of the venom and transcriptomic analysis of the venomous gland from the Mexican centipede Scolopendra viridis

This communication reports the results of proteomic, transcriptomic, biochemical and electrophysiological analysis of the soluble venom and venom glands of the Mexican centipede Scolopendra viridis Say (here thereafter abbreviated S. viridis). Separation of the soluble venom permitted to obtain 54 different fractions, from which a mass finger printing analysis permitted the identification of at least 86 components, where 70% of the molecules have low molecular masses. Two-dimensional electrophoretic separation of this venom revealed the presence of about forty proteins with molecular weights ranging from 17 to 58kDa. The novo sequencing of 149 peptides obtained by LC-MS/MS from the 2D-gels showed the presence of proteins with amino acid sequences similar to several enzymes and venom allergens type 3. Furthermore, a total of 180 sequences were obtained from a cDNA library prepared with two venomous glands. From this, 155 sequences correspond to complete genes containing more than 200 base pairs each. Comparative sequence analyses of these sequences indicated the presence of different types of enzymes and toxin-like genes. Two proteins with molecular weights around 37,000 and 42,000Da were shown to contain hyaluronidase activity. Electrophysiological assays performed with soluble venom show that it decreases mammalian sodium channel currents.

BIOLOGICAL SIGNIFICANCE

Animal venoms of Scolopendra species have been scarcely studied, although they have been reported to contain several bioactive compounds, some of which with potential therapeutic interest. The Mexican centipede S. viridis contains a powerful venom, capable of inflicting immediate effects on their preys. This communication is focused on the identification and description of a proteomic and transcriptomic analysis of the protein components of this venom. Several amino acid sequences similar to reported enzymes are the principal components in the S. viridis venom, but also a low number of toxins were identified. This knowledge should contribute to the understanding of the pharmacological effects caused by bites of this centipede species.