Modelling the interactions between animal venom peptides and membrane proteins

Spider and scorpion knottins targeting voltage-gated sodium ion channels in pain signaling

In sensory neurons that transmit pain signals, whether acute or chronic, voltage-gated sodium channels (VGSCs) are crucial for regulating excitability. NaV1.1, NaV1.3, NaV1.6, NaV1.7, NaV1.8, and NaV1.9 have been demonstrated and defined their functional roles in pain signaling based on their biophysical properties and distinct patterns of expression in each subtype of sensory neurons. Scorpions and spiders are traditional Chinese medicinal materials, belonging to the arachnid class. Most of the studied species of them have evolved venom peptides that exhibit a wide variety of knottins specifically targeting VGSCs with subtype selectivity and conformational specificity. This review provides an overview on the exquisite knottins from scorpion and spider venoms targeting pain-related NaV channels, describing the sequences and the structural features as well as molecular determinants that influence their selectivity on special subtype and at particular conformation, with an aim for the development of novel research tools on NaV channels and analgesics with minimal adverse effects.

Effect of animal venom toxins on the main links of the homeostasis of mammals (Review)

The human body is affected by environmental factors. The dynamic balance between the organism and its environment results from the influence of natural, anthropogenic and social aspects. The factors of exogenous origin determine development of adaptive changes. The present article summarises the mechanisms of animal venom toxins and homeostasis disruption in the body of mammals. The mechanisms underlying pathological changes are associated with shifts in biochemical reactions. Components of the immune, nervous and endocrine systems are key in the host defense and adaptation processes in response to venom by triggering signalling pathways (PI3kinase pathway, arachidonic acid cascade). Animal venom toxins initiate the development of inflammatory processes, the synthesis of pro-inflammatory mediators (cytokines), ROS, proteolytic enzymes, activate the migration of leukocytes and macrophages. Keratinocytes and endothelial cells act as protective barriers under the action of animal venom toxins on the body of mammals. In addition, the formation of pores in cell membranes, structural changes in cell ion channels are characteristic of the action of animal venom toxins.

Bibliometric Review of the Literature on Cone Snail Peptide Toxins from 2000 to 2022

The venom of marine cone snails is mainly composed of peptide toxins called conopeptides, among which conotoxins represent those that are disulfide-rich. Publications on conopeptides frequently state that conopeptides attract considerable interest for their potent and selective activity, but there has been no analysis yet that formally quantifies the popularity of the field. We fill this gap here by providing a bibliometric analysis of the literature on cone snail toxins from 2000 to 2022. Our analysis of 3028 research articles and 393 reviews revealed that research in the conopeptide field is indeed prolific, with an average of 130 research articles per year. The data show that the research is typically carried out collaboratively and worldwide, and that discoveries are truly a community-based effort. An analysis of the keywords provided with each article revealed research trends, their evolution over the studied period, and important milestones. The most employed keywords are related to pharmacology and medicinal chemistry. In 2004, the trend in keywords changed, with the pivotal event of that year being the approval by the FDA of the first peptide toxin drug, ziconotide, a conopeptide, for the treatment of intractable pain. The corresponding research article is among the top ten most cited articles in the conopeptide literature. From the time of that article, medicinal chemistry aiming at engineering conopeptides to treat neuropathic pain ramped up, as seen by an increased focus on topological modifications (e.g., cyclization), electrophysiology, and structural biology.

Structural modeling of peptide toxin-ion channel interactions using RosettaDock

Voltage-gated ion channels play essential physiological roles in action potential generation and propagation. Peptidic toxins from animal venoms target ion channels and provide useful scaffolds for the rational design of novel channel modulators with enhanced potency and subtype selectivity. Despite recent progress in obtaining experimental structures of peptide toxin-ion channel complexes, structural determination of peptide toxins bound to ion channels in physiologically important states remains challenging. Here we describe an application of RosettaDock approach to the structural modeling of peptide toxins interactions with ion channels. We tested this approach on 10 structures of peptide toxin-ion channel complexes and demonstrated that it can sample near-native structures in all tested cases. Our approach will be useful for improving the understanding of the molecular mechanism of natural peptide toxin modulation of ion channel gating and for the structural modeling of novel peptide-based ion channel modulators.

Insight on the interaction between the scorpion toxin blocker Discrepin on potassium voltage-gated channel Kv4.3 by molecular dynamics simulations

Discrepin is a 38-residue α-toxin extracted from the venom of the Venezuelan scorpion Tityus discrepans, which inhibits ionic transit in the voltage-dependent potassium channels (Kv) of A-type current. The effect of specific residues on the IC₅₀ between Discrepine and Kv4.3, the main component of A-type currents, is known; however, the molecular details of the toxin-channel interaction are not known. In this work, we present interaction models between Discrepin (wt) and two peptide variants (V6K/D20K and K13A) on the pore-forming domain of the Kv4.3 channel obtained from homology, docking, and molecular dynamics modeling techniques. The free energy calculations in these models correspond to the order of the experimentally determined IC₅₀ values. Our studies shed light on the role of the K13 residue as responsible for occluding the Kv4.3 selectivity filter and the importance of the V6K mutation in the approach and stabilization of toxin-channel complex interactions.Communicated by Ramaswamy H. Sarma.

Purification and characterization of peptides Ap2, Ap3 and Ap5 (ω-toxins) from the venom of the Brazilian tarantula Acanthoscurria paulensis

Peptides isolated from spider venoms are of pharmacological interest due to their neurotoxic activity, acting on voltage-dependent ion channels present in different types of human body tissues. Three peptide toxins titled as Ap2, Ap3 and Ap5 were purified by RP-HPLC from Acanthoscurria paulensis venom. They were partially sequenced by MALDI In-source Decay method and their sequences were completed and confirmed by transcriptome analysis of the venom gland. The Ap2, Ap3 and Ap5 peptides have, respectively, 42, 41 and 46 amino acid residues, and experimental molecular masses of 4886.3, 4883.7 and 5454.7 Da, with the Ap2 peptide presenting an amidated C-terminus. Amongst the assayed channels - NaV1.1, NaV1.5, NaV1.7, CaV1.2, CaV2.1 and CaV2.2 - Ap2, Ap3 and Ap5 inhibited 20-30 % of CaV2.1 current at 1 μM concentration. Ap3 also inhibited sodium current in NaV1.1, Nav1.5 and Nav1.7 channels by 6.6 ± 1.91 % (p = 0.0276), 4.2 ± 1.09 % (p = 0.0185) and 16.05 ± 2.75 % (p = 0.0282), respectively. Considering that Ap2, Ap3 and Ap5 belong to the 'U'-unknown family of spider toxins, which has few descriptions of biological activity, the present work contributes to the knowledge of these peptides and demonstrates this potential as channel modulators.

Neuropolybin: A new antiseizure peptide obtained from wasp venom

Epilepsy accounts for one of the most serious neurological disorders, and its treatment remains a challenge, due to high cost and harmful side effects. Bioactive molecules extracted from arthropod venoms are considered a promising therapy since these compounds are known for their highly selective and potent profiles. The purpose of this study was to identify and characterize the potential antiseizure effect of the peptide Ppnp7, extracted from the venom of the social wasp Polybia paulista, and also the effect of the bioinspired peptide, named Neuropolybin, in the same parameters. Additionally, we also evaluated the electroencephalographic (EEG) profile in the PTZ-induced acute seizures in animals treated with Neuropolybin, and potential adverse effects of both peptides in general spontaneous activity (Open Field analysis). Interestingly, Ppnp7 and Neuropolybin showed a noteworthy antiseizure effect in rats and mice, respectively. Curves of protection against the maximum seizure were obtained for both peptides, and EEG records demonstrated that Neuropolybin protected 80% of animals from tonic-clonic seizures when applied with a dose of 3 nmol (an approximate Ppnp7 ED₅₀ found in rats). Neuropolybin and Ppnp7 did not cause changes in the general spontaneous activity of the animals in any of the doses evaluated. Therefore, this study demonstrated how compounds isolated from wasps' venom may be essential resources in the search for new drugs, and can also be considered valuable therapeutic and biotechnological tools for the study and future treatment of epileptic disorders.

Beyond hemostasis: a snake venom serine protease with potassium channel blocking and potential antitumor activities

Snake venom serine proteases (SVSPs) are complex and multifunctional enzymes, acting primarily on hemostasis. In this work, we report the hitherto unknown inhibitory effect of a SVSP, named collinein-1, isolated from the venom of Crotalus durissus collilineatus, on a cancer-relevant voltage-gated potassium channel (hEAG1). Among 12 voltage-gated ion channels tested, collinein-1 selectively inhibited hEAG1 currents, with a mechanism independent of its enzymatic activity. Corroboratively, we demonstrated that collinein-1 reduced the viability of human breast cancer cell line MCF7 (high expression of hEAG1), but does not affect the liver carcinoma and the non-tumorigenic epithelial breast cell lines (HepG2 and MCF10A, respectively), which present low expression of hEAG1. In order to obtain both functional and structural validation of this unexpected discovery, where an unusually large ligand acts as an inhibitor of an ion channel, a recombinant and catalytically inactive mutant of collinein-1 (His43Arg) was produced and found to preserve its capability to inhibit hEAG1. A molecular docking model was proposed in which Arg79 of the SVSP 99-loop interacts directly with the potassium selectivity filter of the hEAG1 channel.

Apitoxin and Its Components against Cancer, Neurodegeneration and Rheumatoid Arthritis: Limitations and Possibilities

Natural products represent important sources for the discovery and design of novel drugs. Bee venom and its isolated components have been intensively studied with respect to their potential to counteract or ameliorate diverse human diseases. Despite extensive research and significant advances in recent years, multifactorial diseases such as cancer, rheumatoid arthritis and neurodegenerative diseases remain major healthcare issues at present. Although pure bee venom, apitoxin, is mostly described to mediate anti-inflammatory, anti-arthritic and neuroprotective effects, its primary component melittin may represent an anticancer therapeutic. In this review, we approach the possibilities and limitations of apitoxin and its components in the treatment of these multifactorial diseases. We further discuss the observed unspecific cytotoxicity of melittin that strongly restricts its therapeutic use and review interesting possibilities of a beneficial use by selectively targeting melittin to cancer cells.

In Silico Modeling of the α7 Nicotinic Acetylcholine Receptor: New Pharmacological Challenges Associated with Multiple Modes of Signaling

The α7 nicotinic acetylcholine receptor is a homopentameric ion-channel of the Cys-loop superfamily characterized by its low probability of opening, high calcium permeability, and rapid desensitization. The α7 receptor has been targeted for the treatment of the cognitive symptoms of schizophrenia, depression, and Alzheimer's disease, but it is also involved in inflammatory modulation as a part of the cholinergic anti-inflammatory pathway. Despite its functional importance, in silico studies of the α7 receptor cannot produce a general model explaining the structural features of receptor activation, nor predict the mode of action for various ligand classes. Two particular problems in modeling the α7 nAChR are the absence of a high-resolution structure and the presence of five potentially nonequivalent orthosteric ligand binding sites. There is wide variability regarding the templates used for homology modeling, types of ligands investigated, simulation methods, and simulation times. However, a systematic survey focusing on the methodological similarities and differences in modeling α7 has not been done. In this work, we make a critical analysis of the modeling literature of α7 nAChR by comparing the findings of computational studies with each other and with experimental studies under the main topics of structural studies, ligand binding studies, and comparisons with other nAChR. In light of our findings, we also summarize current problems in the field and make suggestions for future studies concerning modeling of the α7 receptor.

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.

Animal venoms: therapeutic tools for tackling Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative pathology of the central nervous system, mainly involving the selective and progressive loss of dopaminergic neurons from the substantia nigra, resulting in motor and non-motor symptoms. PD remains an incurable ailment; thus, treatments are limited to symptom alleviation. With long-term use, conventional treatments can become inefficient, often triggering possible side effects. Considering these drawbacks, drug discovery constantly turns to nature as a source of efficient therapeutics. Thus, this review explores animal venoms as a rich source of bioactive compounds with potent neuropharmacological profiles for the development of effective adjuvant treatments with fewer side effects, ultimately aiming for the neuroprotection of dopaminergic neurons and the symptomatic relief of PD.