Spider venomics: implications for drug discovery

A Lipid-Sensitive Spider Peptide Toxin Exhibits Selective Anti-Leukemia Efficacy through Multimodal Mechanisms

Anti-cancer peptides (ACPs) represent a promising potential for cancer treatment, although their mechanisms need to be further elucidated to improve their application in cancer therapy. Lycosin-I, a linear amphipathic peptide isolated from the venom of Lycosa singorensis, shows significant anticancer potential. Herein, it is found that Lycosin-I, which can self-assemble into a nanosphere structure, has a multimodal mechanism of action involving lipid binding for the selective and effective treatment of leukemia. Mechanistically, Lycosin-I selectively binds to the K562 cell membrane, likely due to its preferential interaction with negatively charged phosphatidylserine, and rapidly triggers membrane lysis, particularly at high concentrations. In addition, Lycosin-I induces apoptosis, cell cycle arrest in the G1 phase and ferroptosis in K562 cells by suppressing the PI3K-AKT-mTOR signaling pathway and activating cell autophagy at low concentrations. Furthermore, intraperitoneal injection of Lycosin-I inhibits tumor growth of K562 cells in a nude mouse xenograft model without causing side effects. Collectively, the multimodal effect of Lycosin-I can provide new insights into the mechanism of ACPs, and Lycosin-I, which is characterized by high potency and specificity, can be a promising lead for the development of anti-leukemia drugs.

Insecticidal toxicity of ω-Atypitoxin-Cs1a and its inhibitory effects on insect voltage-gated calcium channels

BACKGROUND

Excessive use of chemical insecticides raises concerns about insecticide resistance, urging the development of novel insecticides. Peptide neurotoxins from spider venom are an incredibly rich source of ion channel modulators with potent insecticidal activity. A neurotoxin U1-Atypitoxin-Cs1a from the spider Calommata signata was annotated previously. It was of interest to investigate its insecticidal activity and potential molecular targets.

RESULTS

Cs1a was heterologously expressed, purified and pharmacologically characterized here. The recombinant neurotoxin inhibited high-voltage-activated calcium channel currents with an median inhibitory concentration (IC50 ) value of 0.182 ± 0.026 μm on cockroach DUM neurons and thus was designated as ω-Atypitoxin-Cs1a. The recombinant Cs1a was toxic to three insect pests of agricultural importance, Nilaparvata lugens, Spodoptera frugiperda and Plutella xylostella with median lethal concentration (LD50 ) values of 0.121, 0.172 and 0.356 nmol g-1 , respectively, at 24 h postinjection. Cs1a was equivalently toxic to both insecticide-susceptible and -resistant insects. Cs1a exhibited low toxicity to Danio rerio with an LD50 of 2.316 nmol g-1 .

CONCLUSION

Our results suggest that ω-Atypitoxin-Cs1a is a potent CaV channel inhibitor and an attractive candidate reagent for pest control and resistance management. © 2023 Society of Chemical Industry.

Structure-function and rational design of a spider toxin Ssp1a at human voltage-gated sodium channel subtypes

The structure-function and optimization studies of NaV-inhibiting spider toxins have focused on developing selective inhibitors for peripheral pain-sensing NaV1.7. With several NaV subtypes emerging as potential therapeutic targets, structure-function analysis of NaV-inhibiting spider toxins at such subtypes is warranted. Using the recently discovered spider toxin Ssp1a, this study extends the structure-function relationships of NaV-inhibiting spider toxins beyond NaV1.7 to include the epilepsy target NaV1.2 and the pain target NaV1.3. Based on these results and docking studies, we designed analogues for improved potency and/or subtype-selectivity, with S7R-E18K-rSsp1a and N14D-P27R-rSsp1a identified as promising leads. S7R-E18K-rSsp1a increased the rSsp1a potency at these three NaV subtypes, especially at NaV1.3 (∼10-fold), while N14D-P27R-rSsp1a enhanced NaV1.2/1.7 selectivity over NaV1.3. This study highlights the challenge of developing subtype-selective spider toxin inhibitors across multiple NaV subtypes that might offer a more effective therapeutic approach. The findings of this study provide a basis for further rational design of Ssp1a and related NaSpTx1 homologs targeting NaV1.2, NaV1.3 and/or NaV1.7 as research tools and therapeutic leads.

Anti-Toxoplasma gondii Effects of Lipopeptide Derivatives of Lycosin-I

Toxoplasmosis, caused by Toxoplasma gondii (T. gondii), is a serious zoonotic parasitic disease. We previously found that Lycosin-I exhibited anti-T. gondii activity, but its serum stability was not good enough. In this study, we aimed to improve the stability and activity of Lycosin-I through fatty acid chain modification, so as to find a better anti-T. gondii drug candidate. The α/ε-amino residues of different lysine residues of Lycosin-I were covalently coupled with lauric acid to obtain eight lipopeptides, namely L-C12, L-C12-1, L-C12-2, L-C12-3, L-C12-4, L-C12-5, L-C12-6, and L-C12-7. Among these eight lipopeptides, L-C12 showed the best activity against T. gondii in vitro in a trypan blue assay. We then conjugated a shorter length fatty chain, aminocaproic acid, at the same modification site of L-C12, namely L-an. The anti-T. gondii effects of Lycosin-I, L-C12 and L-an were evaluated via an invasion assay, proliferation assay and plaque assay in vitro. A mouse model acutely infected with T. gondii tachyzoites was established to evaluate their efficacy in vivo. The serum stability of L-C12 and L-an was improved, and they showed comparable or even better activity than Lycosin-I did in inhibiting the invasion and proliferation of tachyzoites. L-an effectively prolonged the survival time of mice acutely infected with T. gondii. These results suggest that appropriate fatty acid chain modification can improve serum stability and enhance anti-T. gondii effect of Lycosin-I. The lipopeptide derivatives of Lycosin-I have potential as a novel anti-T. gondii drug candidate.

Functional Profiling of the A-Family of Venom Peptides from the Wolf Spider Lycosa shansia

The venoms of spiders from the RTA (retro-lateral tibia apophysis) clade contain diverse short linear peptides (SLPs) that offer a rich source of therapeutic candidates. Many of these peptides have insecticidal, antimicrobial and/or cytolytic activities, but their biological functions are unclear. Here, we explore the bioactivity of all known members of the A-family of SLPs previously identified in the venom of the Chinese wolf spider (Lycosa shansia). Our broad approach included an in silico analysis of physicochemical properties and bioactivity profiling for cytotoxic, antiviral, insecticidal and antibacterial activities. We found that most members of the A-family can form α-helices and resemble the antibacterial peptides found in frog poison. The peptides we tested showed no cytotoxic, antiviral or insecticidal activities but were able to reduce the growth of bacteria, including clinically relevant strains of Staphylococcus epidermidis and Listeria monocytogenes. The absence of insecticidal activity may suggest that these peptides have no role in prey capture, but their antibacterial activity may help to defend the venom gland against infection.

Antibacterial Potential Analysis of Novel α-Helix Peptides in the Chinese Wolf Spider Lycosa sinensis

The spider Lycosa sinensis represents a burrowing wolf spider (family Lycosidae) widely distributed in the cotton region of northern China, whose venom is rich in various bioactive peptides. In previous study, we used a combination strategy of peptidomic and transcriptomic analyses to systematically screen and identify potential antimicrobial peptides (AMPs) in Lycosa sinensis venom that matched the α-helix structures. In this work, the three peptides (LS-AMP-E1, LS-AMP-F1, and LS-AMP-G1) were subjected to sequence analysis of the physicochemical properties and helical wheel projection, and then six common clinical pathogenic bacteria (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) with multiple drug-resistance were isolated and cultured for the evaluation and analysis of antimicrobial activity of these peptides. The results showed that two peptides (LS-AMP-E1 and LS-AMP-F1) had different inhibitory activity against six clinical drug-resistant bacteria; they can effectively inhibit the formation of biofilm and have no obvious hemolytic effect. Moreover, both LS-AMP-E1 and LS-AMP-F1 exhibited varying degrees of synergistic therapeutic effects with traditional antibiotics (azithromycin, erythromycin, and doxycycline), significantly reducing the working concentration of antibiotics and AMPs. In terms of antimicrobial mechanisms, LS-AMP-E1 and LS-AMP-F1 destroyed the integrity of bacterial cell membranes in a short period of time and completely inhibited bacterial growth within 10 min of action. Meanwhile, high concentrations of Mg²⁺ effectively reduced the antibacterial activity of LS-AMP-E1 and LS-AMP-F1. Together, it suggested that the two peptides interact directly on bacterial cell membranes. Taken together, bioinformatic and functional analyses in the present work sheds light on the structure-function relationships of LS-AMPs, and facilitates the discovery and clinical application of novel AMPs.

Artificial Intelligence in Biological Sciences

Artificial intelligence (AI), currently a cutting-edge concept, has the potential to improve the quality of life of human beings. The fields of AI and biological research are becoming more intertwined, and methods for extracting and applying the information stored in live organisms are constantly being refined. As the field of AI matures with more trained algorithms, the potential of its application in epidemiology, the study of host–pathogen interactions and drug designing widens. AI is now being applied in several fields of drug discovery, customized medicine, gene editing, radiography, image processing and medication management. More precise diagnosis and cost-effective treatment will be possible in the near future due to the application of AI-based technologies. In the field of agriculture, farmers have reduced waste, increased output and decreased the amount of time it takes to bring their goods to market due to the application of advanced AI-based approaches. Moreover, with the use of AI through machine learning (ML) and deep-learning-based smart programs, one can modify the metabolic pathways of living systems to obtain the best possible outputs with the minimal inputs. Such efforts can improve the industrial strains of microbial species to maximize the yield in the bio-based industrial setup. This article summarizes the potentials of AI and their application to several fields of biology, such as medicine, agriculture, and bio-based industry.

Diversity of intestinal protozoa and clinical signs associated in wild-caught Phoneutria nigriventer kept in captivity for the anti-arachnid serum production

The phylum Arthropoda comprises approximately 85% of all described animal species. The class Arachnida includes some invertebrates of great importance as they are either involved in the transmission of diseases or poses a risk of human envenomation. Spiders belonging to the genus Phoneutria sp., are the arachnids exhibiting medical importance. These animals were quarantined and maintained in captivity at the Biotério de Artrópodes of the Instituto Butantan, São Paulo, Brazil, for the production of the anti-arachnid serum. A total 509 feces samples from different Phoneutria nigriventer were analyzed, and 131 (25.73%) samples were found to be positive for flagellates and ciliates. All positive samples were subjected to DNA extraction and amplification of 18S gene. A total of 16 sequences were obtained and analyzed using BLAST. Sequences were identified as Colpoda steiini, one as Colpoda aspera, one to Colpoda sp., and one as "ciliated". Four identified as Parabodo caudatus, two as Urostipulosphaera sp., one as Helkesimastix sp., and one as a Euglena-like. The presence of clinical signs was observed in 16 spiders. The intestinal protozoa that affect armed spiders were identified for the first time as an initial step for understanding the parasitic diseases in these organisms.

Voltage-Gated Sodium Channel Modulation by a New Spider Toxin Ssp1a Isolated From an Australian Theraphosid

Given the important role of voltage-gated sodium (NaV) channel-modulating spider toxins in elucidating the function, pharmacology, and mechanism of action of therapeutically relevant NaV channels, we screened the venom from Australian theraphosid species against the human pain target hNaV1.7. Using assay-guided fractionation, we isolated a 33-residue inhibitor cystine knot (ICK) peptide (Ssp1a) belonging to the NaSpTx1 family. Recombinant Ssp1a (rSsp1a) inhibited neuronal hNaV subtypes with a rank order of potency hNaV1.7 > 1.6 > 1.2 > 1.3 > 1.1. rSsp1a inhibited hNaV1.7, hNaV1.2 and hNaV1.3 without significantly altering the voltage-dependence of activation, inactivation, or delay in recovery from inactivation. However, rSsp1a demonstrated voltage-dependent inhibition at hNaV1.7 and rSsp1a-bound hNaV1.7 opened at extreme depolarizations, suggesting rSsp1a likely interacted with voltage-sensing domain II (VSD II) of hNaV1.7 to trap the channel in its resting state. Nuclear magnetic resonance spectroscopy revealed key structural features of Ssp1a, including an amphipathic surface with hydrophobic and charged patches shown by docking studies to comprise the interacting surface. This study provides the basis for future structure-function studies to guide the development of subtype selective inhibitors.

The biology and evolution of spider venoms

Spiders are diverse, predatory arthropods that have inhabited Earth for around 400 million years. They are well known for their complex venom systems that are used to overpower their prey. Spider venoms contain many proteins and peptides with highly specific and potent activities suitable for biomedical or agrochemical applications, but the key role of venoms as an evolutionary innovation is often overlooked, even though this has enabled spiders to emerge as one of the most successful animal lineages. In this review, we discuss these neglected biological aspects of spider venoms. We focus on the morphology of spider venom systems, their major components, biochemical and chemical plasticity, as well as ecological and evolutionary trends. We argue that the effectiveness of spider venoms is due to their unprecedented complexity, with diverse components working synergistically to increase the overall potency. The analysis of spider venoms is difficult to standardize because they are dynamic systems, fine-tuned and modified by factors such as sex, life-history stage and biological role. Finally, we summarize the mechanisms that drive spider venom evolution and highlight the need for genome-based studies to reconstruct the evolutionary history and physiological networks of spider venom compounds with more certainty.

Utilisation of compounds from venoms in drug discovery

Difficult drug targets are becoming the normal course of business in drug discovery, sometimes due to large interacting surfaces or only small differences in selectivity regions. For these, a different approach is merited: compounds lying somewhere between the small molecule and the large antibody in terms of many properties including stability, biodistribution and pharmacokinetics. Venoms have evolved over millions of years to be complex mixtures of stable molecules derived from other somatic molecules, the stability comes from the pressure to be ready for delivery at a moment's notice. Snakes, spiders, scorpions, jellyfish, wasps, fish and even mammals have evolved independent venom systems with complex mixtures in their chemical arsenal. These venom-derived molecules have been proven to be useful tools, such as for the development of antihypotensive angiotensin converting enzyme (ACE) inhibitors and have also made successful drugs such as Byetta® (Exenatide), Integrilin® (Eptifibatide) and Echistatin. Only a small percentage of the available chemical space from venoms has been investigated so far and this is growing. In a new era of biological therapeutics, venom peptides present opportunities for larger target engagement surface with greater stability than antibodies or human peptides. There are challenges for oral absorption and target engagement, but there are venom structures that overcome these and thus provide substrate for engineering novel molecules that combine all desired properties. Venom researchers are characterising new venoms, species, and functions all the time, these provide great substrate for solving the challenges presented by today's difficult targets.

Immunological Responses to Envenomation

Venoms are complex mixtures of toxic compounds delivered by bite or sting. In humans, the consequences of envenomation range from self-limiting to lethal. Critical host defence against envenomation comprises innate and adaptive immune strategies targeted towards venom detection, neutralisation, detoxification, and symptom resolution. In some instances, venoms mediate immune dysregulation that contributes to symptom severity. This review details the involvement of immune cell subtypes and mediators, particularly of the dermis, in host resistance and venom-induced immunopathology. We further discuss established venom-associated immunopathology, including allergy and systemic inflammation, and investigate Irukandji syndrome as a potential systemic inflammatory response. Finally, this review characterises venom-derived compounds as a source of immune modulating drugs for treatment of disease.

A Novel Insecticidal Spider Peptide that Affects the Mammalian Voltage-Gated Ion Channel hKv1.5

Spider venoms include various peptide toxins that modify the ion currents, mainly of excitable insect cells. Consequently, scientific research on spider venoms has revealed a broad range of peptide toxins with different pharmacological properties, even for mammal species. In this work, thirty animal venoms were screened against hKv1.5, a potential target for atrial fibrillation therapy. The whole venom of the spider Oculicosa supermirabilis, which is also insecticidal to house crickets, caused voltage-gated potassium ion channel modulation in hKv1.5. Therefore, a peptide from the spider O. supermirabilis venom, named Osu1, was identified through HPLC reverse-phase fractionation. Osu1 displayed similar biological properties as the whole venom; so, the primary sequence of Osu1 was elucidated by both of N-terminal degradation and endoproteolytic cleavage. Based on its primary structure, a gene that codifies for Osu1 was constructed de novo from protein to DNA by reverse translation. A recombinant Osu1 was expressed using a pQE30 vector inside the E. coli SHuffle expression system. recombinant Osu1 had voltage-gated potassium ion channel modulation of human hKv1.5, and it was also as insecticidal as the native toxin. Due to its novel primary structure, and hypothesized disulfide pairing motif, Osu1 may represent a new family of spider toxins.

Venom of the Red-Bellied Black Snake Pseudechis porphyriacus Shows Immunosuppressive Potential

Venoms act with remarkable specificity upon a broad diversity of physiological targets. Venoms are composed of proteins, peptides, and small molecules, providing the foundation for the development of novel therapeutics. This study assessed the effect of venom from the red-bellied black snake (Pseudechis porphyriacus) on human primary leukocytes using bead-based flow cytometry, mixed lymphocyte reaction, and cell viability assays. We show that venom treatment had a significant immunosuppressive effect, inhibiting the secretion of interleukin (IL)-2 and tumor necrosis factor (TNF) from purified human T cells by 90% or greater following stimulation with mitogen (phorbol 12-myristate 13-acetate and ionomycin) or via cluster of differentiation (CD) receptors, CD3/CD28. In contrast, venom treatment did not inhibit TNF or IL-6 release from antigen-presenting cells stimulated with lipopolysaccharide. The reduced cytokine release from T cells was not associated with inhibition of T cell proliferation or reduction of cell viability, consistent with an anti-inflammatory mechanism unrelated to the cell cycle. Deconvolution of the venom using reverse-phase HPLC identified four fractions responsible for the observed immunosuppressive activity. These data suggest that compounds from P. porphyriacus venom may be potential drug leads for T cell-associated conditions such as graft versus host disease, rheumatoid arthritis, and inflammatory bowel disease.

Pain modulatory properties of Phoneutria nigriventer crude venom and derived peptides: A double-edged sword

Phoneutria nigriventer venom (PNV) is a complex mixture of toxins exerting multiple pharmacological effects that ultimately result in severe local pain at the site of the bite. It has been proposed that the PNV-induced pain is mediated by both peripheral and central mechanisms. The nociception triggered by PNV is peripherally mediated by the activation of B₂, 5-HT₄, NMDA, AMPA, NK₁, and NK₂ receptors, as well as TTXS-Na⁺, ASIC, and TRPV1 channels. The activation of tachykinin, glutamate and CGRP receptors along with the production of inflammatory mediators are, at least partially, responsible for the central component of pain. Despite its well established pro-nociceptive properties, PNV contains some toxins with antinociceptive activity, which have been studied in the last few years. The toxins ω-CNTX-Pn4a, ω-CNTX-Pn2a, ω-CNTX-Pn3a, κ-CNTX-Pn1a, U₇-CNTX-Pn1a, δ-CNTX-Pn1a, and Γ-CNTX-Pn1a from PNV, as well as the semi-synthetic peptide PnPP-19 have been tested in different experimental models of pain showing consistent antinociceptive properties. This review aims to discuss the pro- and antinociceptive actions of PNV and its toxins, highlighting possible mechanisms involved in these apparently dualistic properties.

Revealing the Venomous Secrets of the Spider's Web

Orb-weaving spiders use a highly strong, sticky and elastic web to catch their prey. These web properties alone would be enough for the entrapment of prey; however, these spiders may be hiding venomous secrets in the web, which current research is revealing. Here, we provide strong proteotranscriptomic evidence for the presence of toxin/neurotoxin-like proteins, defensins, and proteolytic enzymes on the web silk from Nephila clavipes spider. The results from quantitative-based transcriptomic and proteomic approaches showed that silk-producing glands produce an extensive repertoire of toxin/neurotoxin-like proteins, similar to those already reported in spider venoms. Meanwhile, the insect toxicity results demonstrated that these toxic components can be lethal and/or paralytic chemical weapons used for prey capture on the web, and the presence of fatty acids in the web may be a responsible mechanism opening the way to the web toxins for accessing the interior of prey's body, as shown here. Comparative phylogenomic-level evolutionary analyses revealed orthologous genes among two spider groups, Araneomorphae and Mygalomorphae, and the findings showed protein sequences similar to toxins found in the taxa Scorpiones and Hymenoptera in addition to Araneae. Overall, these data represent a valuable resource to further investigate other spider web toxin systems and also suggest that N. clavipes web is not a passive mechanical trap for prey capture, but it exerts an active role in prey paralysis/killing using a series of neurotoxins.

Venom-derived modulators of epilepsy-related ion channels

Epilepsy is characterised by spontaneous recurrent seizures that are caused by an imbalance between neuronal excitability and inhibition. Since ion channels play fundamental roles in the generation and propagation of action potentials as well as neurotransmitter release at a subset of excitatory and inhibitory synapses, their dysfunction has been linked to a wide variety of epilepsies. Indeed, these unique proteins are the major biological targets for antiepileptic drugs. Selective targeting of a specific ion channel subtype remains challenging for small molecules, due to the high level of homology among members of the same channel family. As a consequence, there is a growing trend to target ion channels with biologics. Venoms are the best known natural source of ion channel modulators, and venom peptides are increasingly recognised as potential therapeutics due to their high selectivity and potency gained through millions of years of evolutionary selection pressure. Here we describe the major ion channel families involved in the pathogenesis of various types of epilepsy, including voltage-gated Na⁺, K⁺, Ca²⁺ channels, Cys-loop receptors, ionotropic glutamate receptors and P2X receptors, and currently available venom-derived peptides that target these channel proteins. Although only a small number of venom peptides have successfully progressed to the clinic, there is reason to be optimistic about their development as antiepileptic drugs, notwithstanding the challenges associated with development of any class of peptide drug.

Key amino acid residues involved in mammalian and insecticidal activities of Magi4 and Hv1b, cysteine-rich spider peptides from the δ-atracotoxin family

δ-Atracotoxins, also known as δ-hexatoxins, are spider neurotoxic peptides, lethal to both vertebrates and insects. Their mechanism of action involves the binding to of the S3/S4 loop of the domain IV of the voltage-gated sodium channels (Na_v). Because of the chemical difficulties of synthesizing folded synthetic δ-atracotoxins correctly, here we explore an expression system that is designed to produce biologically active recombinant δ-atracotoxins, and a number of variants, in order to establish certain amino acids implicated in the pharmacophore of this lethal neurotoxin. In order to elucidate and verify which amino acid residues play a key role that is toxic to vertebrates and insects, amino acid substitutes were produced by aligning the primary structures of several lethal δ-atracotoxins with those of δ-atracotoxins-Hv1b; a member of the δ-atracotoxin family that has low impact on vertebrates and is not toxic to insects. Our findings corroborate that the substitutions of the amino acid residue Y22 from δ-atracotoxin-Mg1a (Magi4) to K22 in δ-atracotoxin-Hv1b reduces its mammalian activity. Moreover, the substitutions of the amino acid residues Y22 and N26 from δ-atracotoxin-Mg1a (Magi4) to K22 and N26 in δ-atracotoxin-Hv1b reduces its insecticidal activity. Also, the basic residues K4 and R5 are important for keeping such insecticidal activity. Structural models suggest that such residues are clustered onto two bioactive surfaces, which share similar areas, previously reported as bioactive surfaces for scorpion α-toxins. Furthermore, these bioactive surfaces were also found to be similar to those found in related spider and anemone toxins, which affect the same Na_v receptor, indicating that these motifs are important not only for scorpion but may be also for animal toxins that affect the S3/S4 loop of the domain IV of the Na_v.

Spider Knottin Pharmacology at Voltage-Gated Sodium Channels and Their Potential to Modulate Pain Pathways

Voltage-gated sodium channels (Na_Vs) are a key determinant of neuronal signalling. Neurotoxins from diverse taxa that selectively activate or inhibit Na_V channels have helped unravel the role of Na_V channels in diseases, including chronic pain. Spider venoms contain the most diverse array of inhibitor cystine knot (ICK) toxins (knottins). This review provides an overview on how spider knottins modulate Na_V channels and describes the structural features and molecular determinants that influence their affinity and subtype selectivity. Genetic and functional evidence support a major involvement of Na_V subtypes in various chronic pain conditions. The exquisite inhibitory properties of spider knottins over key Na_V subtypes make them the best lead molecules for the development of novel analgesics to treat chronic pain.

Spider Venom: Components, Modes of Action, and Novel Strategies in Transcriptomic and Proteomic Analyses

This review gives an overview on the development of research on spider venoms with a focus on structure and function of venom components and techniques of analysis. Major venom component groups are small molecular mass compounds, antimicrobial (also called cytolytic, or cationic) peptides (only in some spider families), cysteine-rich (neurotoxic) peptides, and enzymes and proteins. Cysteine-rich peptides are reviewed with respect to various structural motifs, their targets (ion channels, membrane receptors), nomenclature, and molecular binding. We further describe the latest findings concerning the maturation of antimicrobial, and cysteine-rich peptides that are in most known cases expressed as propeptide-containing precursors. Today, venom research, increasingly employs transcriptomic and mass spectrometric techniques. Pros and cons of venom gland transcriptome analysis with Sanger, 454, and Illumina sequencing are discussed and an overview on so far published transcriptome studies is given. In this respect, we also discuss the only recently described cross contamination arising from multiplexing in Illumina sequencing and its possible impacts on venom studies. High throughput mass spectrometric analysis of venom proteomes (bottom-up, top-down) are reviewed.

Venomic, Transcriptomic, and Bioactivity Analyses of Pamphobeteus verdolaga Venom Reveal Complex Disulfide-Rich Peptides That Modulate Calcium Channels

Pamphobeteus verdolaga is a recently described Theraphosidae spider from the Andean region of Colombia. Previous reports partially characterized its venom profile. In this study, we conducted a detailed analysis that includes reversed-phase high-performance liquid chromatography (rp-HPLC), calcium influx assays, tandem mass spectrometry analysis (tMS/MS), and venom-gland transcriptome. rp-HPLC fractions of P. verdolaga venom showed activity on Ca_V2.2, Ca_V3.2, and Na_V1.7 ion channels. Active fractions contained several peptides with molecular masses ranging from 3399.4 to 3839.6 Da. The tMS/MS analysis of active fraction displaying the strongest activity to inhibit calcium channels showed sequence fragments similar to one of the translated transcripts detected in the venom-gland transcriptome. The putative peptide of this translated transcript corresponded to a toxin, here named ω-theraphositoxin-Pv3a, a potential ion channel modulator toxin that is, in addition, very similar to other theraphositoxins affecting calcium channels (i.e., ω-theraphotoxin-Asp1a). Additionally, using this holistic approach, we found that P. verdolaga venom is an important source of disulfide-rich proteins expressing at least eight superfamilies.

Phylogeny-Guided Selection of Priority Groups for Venom Bioprospecting: Harvesting Toxin Sequences in Tarantulas as a Case Study

Animal venoms are promising sources of novel drug leads, but their translational potential is hampered by the low success rate of earlier biodiscovery programs, in part reflecting the narrow selection of targets for investigation. To increase the number of lead candidates, here we discuss a phylogeny-guided approach for the rational selection of venomous taxa, using tarantulas (family Theraphosidae) as a case study. We found that previous biodiscovery programs have prioritized the three subfamilies Ornithoctoninae, Selenocosmiinae, and Theraphosinae, which provide almost all of the toxin sequences currently available in public databases. The remaining subfamilies are poorly represented, if at all. These overlooked subfamilies include several that form entire clades of the theraphosid life tree, such as the subfamilies Eumenophorinae, Harpactirinae, and Stromatopelminae, indicating that biodiversity space has not been covered effectively for venom biodiscovery in Theraphosidae. Focusing on these underrepresented taxa will increase the likelihood that promising candidates with novel structures and mechanisms of action can be identified in future bioprospecting programs.

Toxins from scratch? Diverse, multimodal gene origins in the predatory robber fly Dasypogon diadema indicate a dynamic venom evolution in dipteran insects

BACKGROUND

Venoms and the toxins they contain represent molecular adaptations that have evolved on numerous occasions throughout the animal kingdom. However, the processes that shape venom protein evolution are poorly understood because of the scarcity of whole-genome data available for comparative analyses of venomous species.

RESULTS

We performed a broad comparative toxicogenomic analysis to gain insight into the genomic mechanisms of venom evolution in robber flies (Asilidae). We first sequenced a high-quality draft genome of the hymenopteran hunting robber fly Dasypogon diadema, analysed its venom by a combined proteotranscriptomic approach, and compared our results with recently described robber fly venoms to assess the general composition and major components of asilid venom. We then applied a comparative genomics approach, based on 1 additional asilid genome, 10 high-quality dipteran genomes, and 2 lepidopteran outgroup genomes, to reveal the evolutionary mechanisms and origins of identified venom proteins in robber flies.

CONCLUSIONS

While homologues were identified for 15 of 30 predominant venom protein in the non-asilid genomes, the remaining 15 highly expressed venom proteins appear to be unique to robber flies. Our results reveal that the venom of D. diadema likely evolves in a multimodal fashion comprising (i) neofunctionalization after gene duplication, (ii) expression-dependent co-option of proteins, and (iii) asilid lineage-specific orphan genes with enigmatic origin. The role of such orphan genes is currently being disputed in evolutionary genomics but has not been discussed in the context of toxin evolution. Our results display an unexpected dynamic venom evolution in asilid insects, which contrasts the findings of the only other insect toxicogenomic evolutionary analysis, in parasitoid wasps (Hymenoptera), where toxin evolution is dominated by single gene co-option. These findings underpin the significance of further genomic studies to cover more neglected lineages of venomous taxa and to understand the importance of orphan genes as possible drivers for venom evolution.

Spider venom peptides as potential drug candidates due to their anticancer and antinociceptive activities

Spider venoms are known to contain proteins and polypeptides that perform various functions including antimicrobial, neurotoxic, analgesic, cytotoxic, necrotic, and hemagglutinic activities. Currently, several classes of natural molecules from spider venoms are potential sources of chemotherapeutics against tumor cells. Some of the spider peptide toxins produce lethal effects on tumor cells by regulating the cell cycle, activating caspase pathway or inactivating mitochondria. Some of them also target the various types of ion channels (including voltage-gated calcium channels, voltage-gated sodium channels, and acid-sensing ion channels) among other pain-related targets. Herein we review the structure and pharmacology of spider-venom peptides that are being used as leads for the development of therapeutics against the pathophysiological conditions including cancer and pain.

Transcriptome analysis of the spider Phoneutria pertyi venom glands reveals novel venom components for the genus Phoneutria

Phoneutria nigriventer spider venom has been studied for more than 40 years and several components with pharmacological potential have been described in it. However, studies on venoms from other species of the Phoneutria genus are scarce. In this work, a conventional cDNA library from the species Phoneutria pertyi venom glands was constructed, aiming to identify novel putative cysteine-rich peptide toxins for the genus Phoneutria. 296 unique sequences were identified and 51 sequences corresponded to putative cysteine-rich peptide toxins. Besides cysteine-rich peptide toxins, other putative venom components such as protease inhibitors, defensins and serine proteinases were identified. Furthermore, by manual curation of the sequences with no match at UniProt, we were able to identify glycine-rich proteins (GRP), a class of venom component never described in Phoneutria genus. This work describes the first complete sequences of toxins from the venom of P. pertyi and reveals that, despite most of the retrieved toxins show a high identity to toxins identified in Phoneutria genus, novel putative toxins remains to be described.

The synthetic peptide LyeTxI-b derived from Lycosa erythrognatha spider venom is cytotoxic to U-87 MG glioblastoma cells

Antimicrobial peptides present a broad spectrum of therapeutic applications, including their use as anticancer peptides. These peptides have as target microbial, normal, and cancerous cells. The oncological properties of these peptides may occur by membranolytic mechanisms or non-membranolytics. In this work, we demonstrate for the first time the cytotoxic effects of the cationic alpha-helical antimicrobial peptide LyeTx I-b on glioblastoma lineage U87-MG. The anticancer property of this peptide was associated with a membranolytic mechanism. Loss of membrane integrity occurred after incubation with the peptide for 15 min, as shown by trypan blue uptake, reduction of calcein-AM conversion, and LDH release. Morphological studies using scanning electron microscopy demonstrated disruption of the plasma membrane from cells treated with LyeTx I-b, including the formation of holes or pores. Transmission electron microscopy analyses showed swollen nuclei with mild DNA condensation, cell volume increase with an electron-lucent cytoplasm and organelle vacuolization, but without the rupture of nuclear or plasmatic membranes. Morphometric analyses revealed a high percentage of cells in necroptosis stages, followed by necrosis and apoptosis at lower levels. Necrostatin-1, a known inhibitor of necroptosis, partially protected the cells from the toxicity of the peptide in a concentration-dependent manner. Imaging flow cytometry confirmed that 59% of the cells underwent necroptosis after 3-h incubation with the peptide. It is noteworthy that LyeTx I-b showed only mild cytotoxicity against normal fibroblasts of human and monkey cell lines and low hemolytic activity in human erythrocytes. All data together point out the anticancer potential of this peptide.

Nuclear Magnetic Resonance seq (NMRseq): A New Approach to Peptide Sequence Tags

Structural analysis of peptides with nuclear magnetic resonance (NMR) spectroscopy generally relies on knowledge of the primary sequence to enable assignment of the resonances prior to determination of the three-dimensional structure. Resonance assignment without knowledge of the sequence is complicated by redundancy in amino acid type, making complete de novo sequencing using NMR spectroscopy unlikely to be feasible. Despite this redundancy, we show here that NMR spectroscopy can be used to identify short sequence tags that can be used to elucidate full-length peptide sequences via database searching. In the current study, we have used this approach to identify conotoxins from the venom of the cone snail Conus geographus and determined the three-dimensional structure of a member of the I3 superfamily. This approach is most likely to be useful for the characterization of disulfide-rich peptides, such as those that were chosen for this study, as they generally have well-defined structures, which enhances the quality of the NMR spectra. In contrast to other sequencing methods, the lack of sample manipulation, such as protease digestion, allows for subsequent bioassays to be carried out using the native sample used for sequence identification.

Identifying novel conopepetides from the venom ducts of Conus litteratus through integrating transcriptomics and proteomics

The venom ducts of marine cone snails secrete highly complex mixtures of cysteine-rich active peptides, which are generally known as conotoxins or conopeptides and provide a potential fertile resource for pharmacological neuroscience research and the discovery of new drugs. Previous studies have devoted substantial effort to the identification of novel conopeptides, and the 109 cone snail species have yielded 7000 known conopeptides to date. Here, we used de novo deep transcriptome sequencing analyses combined with traditional Sanger sequencing and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) to identify 30 distinct conopeptide precursors. Twenty of these were previously reported and the other 10 were novel conopeptide precursors. The study provides the first identification of the Con-ikot-ikot, NSF-bt05, O3 and I1 gene superfamilies in C. litteratus. A new putative superfamily was identified. In addition, the following cysteine frameworks were first identified in this study: CC-C-C-C-C-C-C-C-C-C-C-C-CC-C-C-C-C-C and C-C-C-C-C-CC-C. Several isomerases involved in post-translational modification of conopeptides were identified as well. The discovery of new conopeptides in C. litteratus will enhance our understanding of the conopeptide diversity in this particular clade of cone snails. We also found the existence of intraspecific variations in vermivorous species. Finally, the analysis strategy offers a relatively reliable workflow for screening for peptide drug candidates. SIGNIFICANCE: These novel conopeptides provide a potential resource for the development of new channel-targeting drugs. The intraspecific variation in C. litteratus enhance our understanding of the conopeptide diversity in this particular clade of cone snails. The identified three cysteine residues, which might participate in the formation of disulfide bonds, provide a clue to get the connectivity of cysteine frameworks. Finally, the analysis strategy offers a relatively reliable workflow for screening for peptide drug candidates.

Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating

Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian Na_V-channel isoforms, one insect Na_V channel and one arachnid Na_V channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on Na_V1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac Na_V channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

An overview of Phoneutria nigriventer spider venom using combined transcriptomic and proteomic approaches

Phoneutria nigriventer is one of the largest existing true spiders and one of the few considered medically relevant. Its venom contains several neurotoxic peptides that act on different ion channels and chemical receptors of vertebrates and invertebrates. Some of these venom toxins have been shown as promising models for pharmaceutical or biotechnological use. However, the large diversity and the predominance of low molecular weight toxins in this venom have hampered the identification and deep investigation of the less abundant toxins and the proteins with high molecular weight. Here, we combined conventional and next-generation cDNA sequencing with Multidimensional Protein Identification Technology (MudPIT), to obtain an in-depth panorama of the composition of P. nigriventer spider venom. The results from these three approaches showed that cysteine-rich peptide toxins are the most abundant components in this venom and most of them contain the Inhibitor Cysteine Knot (ICK) structural motif. Ninety-eight sequences corresponding to cysteine-rich peptide toxins were identified by the three methodologies and many of them were considered as putative novel toxins, due to the low similarity to previously described toxins. Furthermore, using next-generation sequencing we identified families of several other classes of toxins, including CAPs (Cysteine Rich Secretory Protein-CRiSP, antigen 5 and Pathogenesis-Related 1-PR-1), serine proteinases, TCTPs (translationally controlled tumor proteins), proteinase inhibitors, metalloproteinases and hyaluronidases, which have been poorly described for this venom. This study provides an overview of the molecular diversity of P. nigriventer venom, revealing several novel components and providing a better basis to understand its toxicity and pharmacological activities.

Studying Smaller and Neglected Organisms in Modern Evolutionary Venomics Implementing RNASeq (Transcriptomics)-A Critical Guide

Venoms are evolutionary key adaptations that species employ for defense, predation or competition. However, the processes and forces that drive the evolution of venoms and their toxin components remain in many aspects understudied. In particular, the venoms of many smaller, neglected (mostly invertebrate) organisms are not characterized in detail, especially with modern methods. For the majority of these taxa, even their biology is only vaguely known. Modern evolutionary venomics addresses the question of how venoms evolve by applying a plethora of -omics methods. These recently became so sensitive and enhanced that smaller, neglected organisms are now more easily accessible to comparatively study their venoms. More knowledge about these taxa is essential to better understand venom evolution in general. The methodological core pillars of integrative evolutionary venomics are genomics, transcriptomics and proteomics, which are complemented by functional morphology and the field of protein synthesis and activity tests. This manuscript focuses on transcriptomics (or RNASeq) as one toolbox to describe venom evolution in smaller, neglected taxa. It provides a hands-on guide that discusses a generalized RNASeq workflow, which can be adapted, accordingly, to respective projects. For neglected and small taxa, generalized recommendations are difficult to give and conclusions need to be made individually from case to case. In the context of evolutionary venomics, this overview highlights critical points, but also promises of RNASeq analyses. Methodologically, these concern the impact of read processing, possible improvements by perfoming multiple and merged assemblies, and adequate quantification of expressed transcripts. Readers are guided to reappraise their hypotheses on venom evolution in smaller organisms and how robustly these are testable with the current transcriptomics toolbox. The complementary approach that combines particular proteomics but also genomics with transcriptomics is discussed as well. As recently shown, comparative proteomics is, for example, most important in preventing false positive identifications of possible toxin transcripts. Finally, future directions in transcriptomics, such as applying 3rd generation sequencing strategies to overcome difficulties by short read assemblies, are briefly addressed.

Sodium channels and pain: from toxins to therapies

Voltage-gated sodium channels (NaV channels) are essential for the initiation and propagation of action potentials that critically influence our ability to respond to a diverse range of stimuli. Physiological and pharmacological studies have linked abnormal function of NaV channels to many human disorders, including chronic neuropathic pain. These findings, along with the description of the functional properties and expression pattern of NaV channel subtypes, are helping to uncover subtype specific roles in acute and chronic pain and revealing potential opportunities to target these with selective inhibitors. High-throughput screens and automated electrophysiology platforms have identified natural toxins as a promising group of molecules for the development of target-specific analgesics. In this review, the role of toxins in defining the contribution of NaV channels in acute and chronic pain states and their potential to be used as analgesic therapies are discussed.

LINKED ARTICLES

This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

True Lies: Using Proteomics to Assess the Accuracy of Transcriptome-Based Venomics in Centipedes Uncovers False Positives and Reveals Startling Intraspecific Variation in Scolopendra Subspinipes

Centipede venoms have emerged as a rich source of novel bioactive compounds. However, most centipede species are commonly considered too small for venom extraction and transcriptomics is likely to be an attractive way of probing the molecular diversity of these venoms. Examining the venom composition of Scolopendra subspinipes, we test the accuracy of this approach. We compared the proteomically determined venom profile with four common toxin transcriptomic toxin annotation approaches: BLAST search against toxins in UniProt, lineage-specific toxins, or species-specific toxins and comparative expression analyses of venom and non-venom producing tissues. This demonstrated that even toxin annotation based on lineage-specific homology searches is prone to substantial errors compared to a proteomic approach. However, combined comparative transcriptomics and phylogenetic analysis of putative toxin families substantially improves annotation accuracy. Furthermore, comparison of the venom composition of S. subspinipes with the closely related S. subspinipes mutilans revealed a surprising lack of overlap. This first insight into the intraspecific venom variability of centipedes contrasts the sequence conservation expected from previous findings that centipede toxins evolve under strong negative selection. Our results highlight the importance of proteomic data in studies of even comparably well-characterized venoms and warrants caution when sourcing venom from centipedes of unknown origin.

Animal Toxins as Therapeutic Tools to Treat Neurodegenerative Diseases

Neurodegenerative diseases affect millions of individuals worldwide. So far, no disease-modifying drug is available to treat patients, making the search for effective drugs an urgent need. Neurodegeneration is triggered by the activation of several cellular processes, including oxidative stress, mitochondrial impairment, neuroinflammation, aging, aggregate formation, glutamatergic excitotoxicity, and apoptosis. Therefore, many research groups aim to identify drugs that may inhibit one or more of these events leading to neuronal cell death. Venoms are fruitful natural sources of new molecules, which have been relentlessly enhanced by evolution through natural selection. Several studies indicate that venom components can exhibit selectivity and affinity for a wide variety of targets in mammalian systems. For instance, an expressive number of natural peptides identified in venoms from animals, such as snakes, scorpions, bees, and spiders, were shown to lessen inflammation, regulate glutamate release, modify neurotransmitter levels, block ion channel activation, decrease the number of protein aggregates, and increase the levels of neuroprotective factors. Thus, these venom components hold potential as therapeutic tools to slow or even halt neurodegeneration. However, there are many technological issues to overcome, as venom peptides are hard to obtain and characterize and the amount obtained from natural sources is insufficient to perform all the necessary experiments and tests. Fortunately, technological improvements regarding heterologous protein expression, as well as peptide chemical synthesis will help to provide enough quantities and allow chemical and pharmacological enhancements of these natural occurring compounds. Thus, the main focus of this review is to highlight the most promising studies evaluating animal toxins as therapeutic tools to treat a wide variety of neurodegenerative conditions, including Alzheimer’s disease, Parkinson’s disease, brain ischemia, glaucoma, amyotrophic lateral sclerosis, and multiple sclerosis.

Gomesin peptides prevent proliferation and lead to the cell death of devil facial tumour disease cells

The Tasmanian devil faces extinction due to devil facial tumour disease (DFTD), a highly transmittable clonal form of cancer without available treatment. In this study, we report the cell-autonomous antiproliferative and cytotoxic activities exhibited by the spider peptide gomesin (AgGom) and gomesin-like homologue (HiGom) in DFTD cells. Mechanistically, both peptides caused a significant reduction at G0/G1 phase, in correlation with an augmented expression of the cell cycle inhibitory proteins p53, p27, p21, necrosis, exacerbated generation of reactive oxygen species and diminished mitochondrial membrane potential, all hallmarks of cellular stress. The screening of a novel panel of AgGom-analogues revealed that, unlike changes in the hydrophobicity and electrostatic surface, the cytotoxic potential of the gomesin analogues in DFTD cells lies on specific arginine substitutions in the eight and nine positions and alanine replacement in three, five and 12 positions. In conclusion, the evidence supports gomesin as a potential antiproliferative compound against DFTD disease.

Protein-Based Therapeutic Killing for Cancer Therapies

The treatment of some high-incidence human diseases is based on therapeutic cell killing. In cancer this is mainly achieved by chemical drugs that are systemically administered to reach effective toxic doses. As an innovative alternative, cytotoxic proteins identified in nature can be adapted as precise therapeutic agents. For example, individual toxins and venom components, proapoptotic factors, and antimicrobial peptides from bacteria, animals, plants, and humans have been engineered as highly potent drugs. In addition to the intrinsic cytotoxic activities of these constructs, their biological fabrication by DNA recombination allows the recruitment, in single pharmacological entities, of diverse functions of clinical interest such as specific cell-surface receptor binding, self-activation, and self-assembling as nanoparticulate materials, with wide applicability in cell-targeted oncotherapy and theragnosis.

The Aromatic Head Group of Spider Toxin Polyamines Influences Toxicity to Cancer Cells

Spider venoms constitute incredibly diverse libraries of compounds, many of which are involved in prey capture and defence. Polyamines are often prevalent in the venom and target ionotropic glutamate receptors. Here we show that a novel spider polyamine, PA₃₆₆, containing a hydroxyphenyl-based structure is present in the venom of several species of tarantula, and has selective toxicity against MCF-7 breast cancer cells. By contrast, a polyamine from an Australian funnel-web spider venom, which contains an identical polyamine tail to PA₃₆₆ but an indole-based head-group, is only cytotoxic at high concentrations. Our results suggest that the ring structure plays a role in the cytotoxicity and that modification to the polyamine head group might lead to more potent and selective compounds with potential as novel cancer treatments.

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.'

Proteogenomics from a bioinformatics angle: A growing field

Proteogenomics is a research area that combines areas as proteomics and genomics in a multi-omics setup using both mass spectrometry and high-throughput sequencing technologies. Currently, the main goals of the field are to aid genome annotation or to unravel the proteome complexity. Mass spectrometry based identifications of matching or homologues peptides can further refine gene models. Also, the identification of novel proteoforms is also made possible based on detection of novel translation initiation sites (cognate or near-cognate), novel transcript isoforms, sequence variation or novel (small) open reading frames in intergenic or un-translated genic regions by analyzing high-throughput sequencing data from RNAseq or ribosome profiling experiments. Other proteogenomics studies using a combination of proteomics and genomics techniques focus on antibody sequencing, the identification of immunogenic peptides or venom peptides. Over the years, a growing amount of bioinformatics tools and databases became available to help streamlining these cross-omics studies. Some of these solutions only help in specific steps of the proteogenomics studies, e.g. building custom sequence databases (based on next generation sequencing output) for mass spectrometry fragmentation spectrum matching. Over the last few years a handful integrative tools also became available that can execute complete proteogenomics analyses. Some of these are presented as stand-alone solutions, whereas others are implemented in a web-based framework such as Galaxy. In this review we aimed at sketching a comprehensive overview of all the bioinformatics solutions that are available for this growing research area. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:584-599, 2017.

Insect-Active Toxins with Promiscuous Pharmacology from the African Theraphosid Spider Monocentropus balfouri

Many chemical insecticides are becoming less efficacious due to rising resistance in pest species, which has created much interest in the development of new, eco-friendly bioinsecticides. Since insects are the primary prey of most spiders, their venoms are a rich source of insect-active peptides that can be used as leads for new bioinsecticides or as tools to study molecular receptors that are insecticidal targets. In the present study, we isolated two insecticidal peptides, µ/ω-TRTX-Mb1a and -Mb1b, from venom of the African tarantula Monocentropus balfouri. Recombinant µ/ω-TRTX-Mb1a and -Mb1b paralyzed both Lucilia cuprina (Australian sheep blowfly) and Musca domestica (housefly), but neither peptide affected larvae of Helicoverpa armigera (cotton bollworms). Both peptides inhibited currents mediated by voltage-gated sodium (Na_V) and calcium channels in Periplaneta americana (American cockroach) dorsal unpaired median neurons, and they also inhibited the cloned Blattella germanica (German cockroach) Na_V channel (BgNa_V1). An additional effect seen only with Mb1a on BgNa_V1 was a delay in fast inactivation. Comparison of the Na_V channel sequences of the tested insect species revealed that variations in the S1–S2 loops in the voltage sensor domains might underlie the differences in activity between different phyla.

New Disulfide-Stabilized Fold Provides Sea Anemone Peptide to Exhibit Both Antimicrobial and TRPA1 Potentiating Properties

A novel bioactive peptide named τ-AnmTx Ueq 12-1 (short name Ueq 12-1) was isolated and characterized from the sea anemone Urticina eques. Ueq 12-1 is unique among the variety of known sea anemone peptides in terms of its primary and spatial structure. It consists of 45 amino acids including 10 cysteine residues with an unusual distribution and represents a new group of sea anemone peptides. The 3D structure of Ueq 12-1, determined by NMR spectroscopy, represents a new disulfide-stabilized fold partly similar to the defensin-like fold. Ueq 12-1 showed the dual activity of both a moderate antibacterial activity against Gram-positive bacteria and a potentiating activity on the transient receptor potential ankyrin 1 (TRPA1). Ueq 12-1 is a unique peptide potentiator of the TRPA1 receptor that produces analgesic and anti-inflammatory effects in vivo. The antinociceptive properties allow us to consider Ueq 12-1 as a potential analgesic drug lead with antibacterial properties.

Progress and challenges in the optimization of toxin peptides for development as pain therapeutics

The number of new toxin peptide discoveries has been rapidly growing in the past few decades. Because of progress in proteomics, sequencing technologies, and high throughput bioassays, the search for new toxin peptides from venom collections and potency optimization has become manageable. However, to date, only six toxin peptide-derived therapeutics have been approved by the USFDA, with only one, ziconotide, for a pain indication. The challenge of venom-derived peptide therapeutic development remains in improving selectivity to the target and more importantly, in delivery of these peptides to the sites of action in the central and peripheral nervous system. In this review, we highlight peptide toxins that target major therapeutic targets for pain and discuss the challenges of developing toxin peptides as potential therapeutics.

Pharmacological screening technologies for venom peptide discovery

Venomous animals occupy one of the most successful evolutionary niches and occur on nearly every continent. They deliver venoms via biting and stinging apparatuses with the aim to rapidly incapacitate prey and deter predators. This has led to the evolution of venom components that act at a number of biological targets - including ion channels, G-protein coupled receptors, transporters and enzymes - with exquisite selectivity and potency, making venom-derived components attractive pharmacological tool compounds and drug leads. In recent years, plate-based pharmacological screening approaches have been introduced to accelerate venom-derived drug discovery. A range of assays are amenable to this purpose, including high-throughput electrophysiology, fluorescence-based functional and binding assays. However, despite these technological advances, the traditional activity-guided fractionation approach is time-consuming and resource-intensive. The combination of screening techniques suitable for miniaturization with sequence-based discovery approaches - supported by advanced proteomics, mass spectrometry, chromatography as well as synthesis and expression techniques - promises to further improve venom peptide discovery. Here, we discuss practical aspects of establishing a pipeline for venom peptide drug discovery with a particular emphasis on pharmacology and pharmacological screening approaches. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'