AMPA receptors mediate fast excitatory neurotransmission and are critical for CNS development and function. Calcium-permeable subsets of AMPA receptors are strongly implicated in acute and chronic ...neurological disorders. However, despite the clinical importance, the therapeutic landscape for specifically targeting them, and not the calcium-impermeable AMPA receptors, remains largely undeveloped. To address this problem, we used cryo-electron microscopy and electrophysiology to investigate the mechanisms by which small-molecule blockers selectively inhibit ion channel conductance in calcium-permeable AMPA receptors. We determined the structures of calcium-permeable GluA2 AMPA receptor complexes with the auxiliary subunit stargazin bound to channel blockers, including the orb weaver spider toxin AgTx-636, the spider toxin analog NASPM, and the adamantane derivative IEM-1460. Our structures provide insights into the architecture of the blocker binding site and the mechanism of trapping, which are critical for development of small molecules that specifically target calcium-permeable AMPA receptors.
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•Cryo-EM structures show how toxins and their synthetic analogs block CP-AMPARs•Blockers bind to open CP-AMPAR channel and can be trapped inside when it closes•Blockers’ hydrophobic heads and polyamine tails uniquely match pore electrostatics•Our findings suggest a mechanism of CP-AMPAR block by endogenous polyamines
Calcium-permeable AMPA receptors (CP-AMPARs) are strongly implicated in neurological disorders. Twomey et al. uncover the structural bases of CP-AMPAR channel block by toxins and their synthetic analogs, providing a foundation for the design of new therapeutic agents.
Venoms with oral toxicity towards insects Oparin, Peter B.; Nikodimov, Sergei S.; Vassilevski, Alexander A.
Toxicon (Oxford),
November 2023, 2023-11-00, 20231101, Letnik:
235
Journal Article
Recenzirano
Animal venoms are a promising source of potential bioinsecticides. To find hits with pronounced oral insect toxicity, we screened 82 venoms using Achroia grisella (Lepidoptera) and Tenebrio molitor ...(Coleoptera) larvae, and adult Drosophila melanogaster (Diptera). We also injected the most potent venoms in adult D. melanogaster to compare their efficiency in different routes of administration. 18 venoms from spiders and snakes show high oral toxicity and can be further exploited to isolate new insecticides.
•82 venoms were screened for oral activity against insects from three orders.•18 of these venoms showed high toxicity.•The most potent venoms were obtained from spiders and vipers.
•We describe the major types of labelled toxins.•We discuss the methods of labelled toxins production.•We report examples of labelled toxins application.
Animal toxins are traditional and ...indispensible molecular tools that find application in different fields of biochemistry, neurobiology and pharmacology. These compounds possess several outstanding properties such as high affinity and selectivity with respect to particular molecular targets, most importantly ion channels and neuroreceptors, and stability. In addition to using toxins per se, a wide variety of labelled modifications have been obtained including radioactive and fluorescent derivatives. Here, we discuss the major types of labelled toxins, methods of their production and principal possibilities of application ranging from receptor localization and visualization to development of screening systems and diagnostic tools, and drug discovery.
Old world scorpions produce an abundance of toxins called α-NaTx, which interfere with the fast inactivation of voltage-gated sodium channels. Their selectivity to channels of mammals or insects ...depends on a part of toxin named the specificity module. We report here the spatial structure of a major and broadly active toxin MeuNaTxα-1 from the venom of Mesobuthus eupeus. Notably, its specificity module is markedly different from other α-NaTx with known 3D structure. Close inspection shows that its conformation is a result of an interplay between protein motifs such as the nest and niche, which eventually shape α-NaTx structural diversity.
Apamin is often cited as one of the few substances selectively acting on small-conductance Ca
2+
-activated potassium channels (K
Ca
2). However, published pharmacological and structural data remain ...controversial. Here, we investigated the molecular pharmacology of apamin by two-electrode voltage-clamp in
Xenopus laevis
oocytes and patch-clamp in HEK293, COS7, and CHO cells expressing the studied ion channels, as well as in isolated rat brain neurons. The microtitre broth dilution method was used for antimicrobial activity screening. The spatial structure of apamin in aqueous solution was determined by NMR spectroscopy. We tested apamin against 42 ion channels (K
Ca
, K
V
, Na
V
, nAChR, ASIC, and others) and confirmed its unique selectivity to K
Ca
2 channels. No antimicrobial activity was detected for apamin against Gram-positive or Gram-negative bacteria. The NMR solution structure of apamin was deposited in the Protein Data Bank. The results presented here demonstrate that apamin is a selective nanomolar or even subnanomolar-affinity K
Ca
2 inhibitor with no significant effects on other molecular targets. The spatial structure as well as ample functional data provided here support the use of apamin as a K
Ca
2-selective pharmacological tool and as a template for drug design.
Here, we introduce the third release of Kalium database (http://kaliumdb.org/), a manually curated comprehensive depository that accumulates data on polypeptide ligands of potassium channels. The ...major goal of this amplitudinous update is to summarize findings for natural polypeptide ligands of K+ channels, as well as data for the artificial derivatives of these substances obtained over the decades of exploration. We manually analyzed more than 700 original manuscripts and systematized the information on mutagenesis, production of radio‐ and fluorescently labeled derivatives, and the molecular pharmacology of K+ channel ligands. As a result, data on more than 1200 substances were processed and added enriching the database content fivefold. We also included the electrophysiological data obtained on the understudied and neglected K+ channels including the heteromeric and concatenated channels. We associated target channels in Kalium with corresponding entries in the official database of the International Union of Basic and Clinical Pharmacology. Kalium was supplemented with an adaptive Statistics page, where users are able to obtain actual data output. Several other improvements were introduced, such as a color code to distinguish the range of ligand activity concentrations and advanced tools for filtration and sorting. Kalium is a fully open‐access database, crosslinked to other databases of interest. It can be utilized as a convenient resource containing ample up‐to‐date information about polypeptide ligands of K+ channels.
In the present study, we show that venom of the ant spider Lachesana tarabaevi is unique in terms of molecular composition and toxicity. Whereas venom of most spiders studied is rich in ...disulfide-containing neurotoxic peptides, L. tarabaevi relies on the production of linear (no disulfide bridges) cytolytic polypeptides. We performed full-scale peptidomic examination of L. tarabaevi venom supported by cDNA library analysis. As a result, we identified several dozen components, and a majority (∼80% of total venom protein) exhibited membrane-active properties. In total, 33 membrane-interacting polypeptides (length of 18-79 amino acid residues) comprise five major groups: repetitive polypeptide elements (Rpe), latarcins (Ltc), met-lysines (MLys), cyto-insectotoxins (CIT) and latartoxins (LtTx). Rpe are short (18 residues) amphiphilic molecules that are encoded by the same genes as antimicrobial peptides Ltc 4a and 4b. Isolation of Rpe confirms the validity of the iPQM (inverted processing quadruplet motif) proposed to mark the cleavage sites in spider toxin precursors that are processed into several mature chains. MLys (51 residues) present 'idealized' amphiphilicity when modelled in a helical wheel projection with sharply demarcated sectors of hydrophobic, cationic and anionic residues. Four families of CIT (61-79 residues) are the primary weapon of the spider, accounting for its venom toxicity. Toxins from the CIT 1 and 2 families have a modular structure consisting of two shorter Ltc-like peptides. We demonstrate that in CIT 1a, these two parts act in synergy when they are covalently linked. This finding supports the assumption that CIT have evolved through the joining of two shorter membrane-active peptides into one larger molecule.
Previous studies have identified some key amino acid residues in scorpion toxins blocking potassium channels. In particular, the most numerous toxins belonging to the α-KTx family and affecting ...voltage-gated potassium channels (KV) present a conserved K-C-X-N motif in the C-terminal half of their sequence. Here, we show that the X position of this motif is almost always occupied by either methionine or isoleucine. We compare the activity of three pairs of peptides that differ just by this residue on a panel of KV1 channels and find that toxins bearing methionine affect preferentially KV1.1 and 1.6 isoforms. The refined K-C-M/I-N motif stands out as the principal structural element of α-KTx conferring high affinity and selectivity to KV channels.
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•Most α-KTx contain a conserved K-C-M/I-N motif demonstrating methionine-isoleucine dichotomy.•The activity of three pairs of peptides differing at the M/I position was compared.•Interchange between methionine and isoleucine residues in the motif affects toxin selectivity.
BeKm‐1 is a peptide toxin from scorpion venom that blocks the pore of the potassium channel hERG (Kv11.1) in the human heart. Although individual protein structures have been resolved, the structure ...of the complex between hERG and BeKm‐1 is unknown. Here, we used molecular dynamics and ensemble docking, guided by previous double‐mutant cycle analysis data, to obtain an in silico model of the hERG–BeKm‐1 complex. Adding to the previous mutagenesis study of BeKm‐1, our model uncovers the key role of residue Arg20, which forms three interactions (a salt bridge and hydrogen bonds) with the channel vestibule simultaneously. Replacement of this residue even by lysine weakens the interactions significantly. In accordance, the recombinantly produced BeKm‐1R20K mutant exhibited dramatically decreased activity on hERG. Our model may be useful for future drug design attempts.
Using computational methods, we constructed a model of the cardiac ion channel hERG in complex with BeKm‐1, a scorpion toxin. We identified the crucial role of the toxin residue Arg20 and validated it by in silico and in vitro mutagenesis. The BeKm‐1R20K mutant showed dramatically reduced activity, suggesting the significance of Arg20 for channel binding. Our model aids future drug design attempts.
Latarcins: versatile spider venom peptides Dubovskii, Peter V; Vassilevski, Alexander A; Kozlov, Sergey A ...
Cellular and Molecular Life Sciences,
12/2015, Letnik:
72, Številka:
23
Journal Article, Book Review
Recenzirano
Arthropod venoms feature the presence of cytolytic peptides believed to act synergetically with neurotoxins to paralyze prey or deter aggressors. Many of them are linear, i.e., lack disulfide bonds. ...When isolated from the venom, or obtained by other means, these peptides exhibit common properties. They are cationic; being mostly disordered in aqueous solution, assume amphiphilic α-helical structure in contact with lipid membranes; and exhibit general cytotoxicity, including antifungal, antimicrobial, hemolytic, and anticancer activities. To suit the pharmacological needs, the activity spectrum of these peptides should be modified by rational engineering. As an example, we provide a detailed review on latarcins (Ltc), linear cytolytic peptides from Lachesana tarabaevi spider venom. Diverse experimental and computational techniques were used to investigate the spatial structure of Ltc in membrane-mimicking environments and their effects on model lipid bilayers. The antibacterial activity of Ltc was studied against a panel of Gram-negative and Gram-positive bacteria. In addition, the action of Ltc on erythrocytes and cancer cells was investigated in detail with confocal laser scanning microscopy. In the present review, we give a critical account of the progress in the research of Ltc. We explore the relationship between Ltc structure and their biological activity and derive molecular characteristics, which can be used for optimization of other linear peptides. Current applications of Ltc and prospective use of similar membrane-active peptides are outlined.
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