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Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient's history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future. [ABSTRACT FROM AUTHOR]

The regulation of neuronal excitability is complex, as ion channels and neurotransmitter receptors are underlying a large variety of modulating effects. Alterations in the expression patterns of receptors or channel subunits as well as differential splicing contribute to the regulation of neuronal excitability. RNA editing is another and more recently explored mechanism to increase protein diversity, as the genomic recoding leads to new gene products with novel functional and pharmacological properties. In humans A-to-I RNA editing targets several neuronal receptors and channels, including GluR2/5/6 subunits, the Kv1.1 channel, and the 5-HT receptor. Our review summarizes that RNA editing of these proteins does not only change protein function, but also the pharmacology and presumably the drug therapy in human diseases. [ABSTRACT FROM AUTHOR]

Abstract: The wolf spider Lycosa singoriensis is a hunting spider with a widespread distribution in northwest China. The venom gland of spiders, which is a very specialized secretory tissue, can secrete abundant and complex toxin components. To extensively examine the transcripts expressed in the venom glands of L. singoriensis, we generated 833 expressed sequence tags (ESTs) from a directional cDNA library. Toxin-like sequences account for 69.1% of these ESTs, 17.3% are similar to cellular transcripts and 13.6% have no significant similarity to any known sequences. Here, we identified 223 novel toxin-like sequences, which can be classified into six different superfamilies; that means a novel potential source of ligands for varied ion channels was discovered. With the aid of Gene Ontology terms and homology to eukaryotic orthologous groups, the annotation of cellular transcripts revealed some cellular processes important for the toxin secretion of venom glands including protein synthesis, protein folding, tuned post-translational processing and trafficking, etc. [Copyright &y& Elsevier]

Abstract: The voltage-gated sodium (Nav) channel is a target for a number of drugs, insecticides and neurotoxins. These bind to at least seven identified neurotoxin binding sites and either block conductance or modulate Nav channel gating. A number of peptide neurotoxins from the venoms of araneomorph and mygalomorph spiders have been isolated and characterized and determined to interact with several of these sites. These all conform to an ‘inhibitor cystine-knot’ motif with structural, but not sequence homology, to a variety of other spider and marine snail toxins. Of these, spider toxins several show phyla-specificity and are being considered as lead compounds for the development of biopesticides. Hainantoxin-I appears to target site-1 to block Nav channel conductance. Magi 2 and Tx4(6-1) slow Nav channel inactivation via an interaction with site-3. The δ-palutoxins, and most likely μ-agatoxins and curtatoxins, target site-4. However, their action is complex with the μ-agatoxins causing a hyperpolarizing shift in the voltage-dependence of activation, an action analogous to scorpion β-toxins, but with both δ-palutoxins and μ-agatoxins slowing Nav channel inactivation, a site-3-like action. In addition, several other spider neurotoxins, such as δ-atracotoxins, are known to target both insect and vertebrate Nav channels most likely as a result of the conserved structures within domains of voltage-gated ion channels across phyla. These toxins may provide tools to establish the molecular determinants of invertebrate selectivity. These studies are being greatly assisted by the determination of the pharmacophore of these toxins, but without precise identification of their binding site and mode of action their potential in the above areas remains underdeveloped. [Copyright &y& Elsevier]

Arthropods are one of the most diverse animal groups on the Earth. Spiders belong to this phylum and they are ancient animals with a history going back some three hundred million years. They are abundant, widespread, and natural controllers of insect populations. They use their venom to capture prey or to fight against predators. This venom is constituted of various peptides and enzymes with different activities. Among these proteins, toxic peptides are responsible for the macroscopic effect of the venom. Most of the toxins are known to interact with ion channels (mainly potassium channels, sodium channels, and calcium channels). These transmembrane molecules are ubiquitous in the cells. They underlie a broad range of the most basic biological processes, from excitation and signaling to secretion and absorption. Like enzymes they are diverse and ubiquitous macromolecular catalysts with high substrate specificity and subject to strong regulation. Animal toxins and, more specifically, spider toxins are effectors of these channels. Depending on the peptide, they have ability to block the channel by plugging into its pore of conduction, or by modifying the opening and closing capacity of the channels, binding on a few specific sites along the structure of the channel. Most of these peptides fold according to the overall same pattern, the inhibitor cystine knot (ICK) scaffold. Basically, it consists of a ring formed by a part of the backbone of the peptide and two disulfide bridges, penetrated by a third disulfide bridge. An additional disulfide bridge might be found in some toxins. Another fold has been found in a few toxins and has been described as the DDH scaffold. This motif lacks the knot and comprises an antiparallel β -hairpin stabilized by two conserved disulfide bridges. This paper will try to summarize the structural characteristics of the spider toxins for which the fold has been described in the literature. [ABSTRACT FROM AUTHOR]

PnTx3-1 is a peptide isolated from the venom of the spider Phoneutria nigriventer that specifically inhibits A-type K+ currents (IA) in GH3 cells. Here we used a bacterial expression system to produce an NH2-extended mutant of PnTx3-1 (ISEF-PnTx3-1) and tested whether the toxin is functional. The recombinant toxin was purified from bacterial extracts by a combination of affinity and ion-exchange chromatography. The recombinant toxin blocked A-type K+ currents in GH3 cells in a fashion similar to that observed with the wild-type toxin purified from the spider venom. These results suggest that recombinant cDNA methods provide a novel source for the production of functional Phoneutria toxins. The recombinant ISEF-PnTx3-1 should be useful for further understanding of the role of A-type K+ currents in biological processes. [Copyright &y& Elsevier]