Novel Class of Spider Toxin

Abstract

Venom of the yellow sac spider Cheiracanthium punctorium (Miturgidae) was found unique in terms of molecular composition. Its principal toxic component CpTx 1 (15.1 kDa) was purified, and its full amino acid sequence (134 residues) was established by protein chemistry and mass spectrometry techniques. CpTx 1 represents a novel class of spider toxin with modular architecture. It consists of two different yet homologous domains (modules) each containing a putative inhibitor cystine knot motif, characteristic of the widespread single domain spider neurotoxins. Venom gland cDNA sequencing provided precursor protein (prepropeptide) structures of three CpTx 1 isoforms (a-c) that differ by single residue substitutions. The toxin possesses potent insecticidal (paralytic and lethal), cytotoxic, and membrane-damaging activities. In both fly and frog neuromuscular preparations, it causes stable and irreversible depolarization of muscle fibers leading to contracture. This effect appears to be receptor-independent and is inhibited by high concentrations of divalent cations. CpTx 1 lyses cell membranes, as visualized by confocal microscopy, and destabilizes artificial membranes in a manner reminiscent of other membrane-active peptides by causing numerous defects of variable conductance and leading to bilayer rupture. The newly discovered class of modular polypeptides enhances our knowledge of the toxin universe.With over 40,000 species described to date (1), spiders represent one of the most diverse and successful groups of living organisms. Initial studies of spider venoms focused on those few dangerous to human health or threatening domestic animals (2). These include the widow spiders from the genus Latrodectus (Theridiidae) (3), the recluse spiders from the genus Loxosceles (Sicariidae) (4), the wandering spiders from the genus Phoneutria (Ctenidae) (5), and the Australian funnelweb spiders from the genera Atrax and Hadronyche (Hexathelidae) (6). Today, however, spider venoms attract more research because they represent vast evolutionary-edited natural pharmacopoeias (7). These can be sources of indispensable tools for fundamental studies. For instance, -agatoxins from Agelenopsis aperta and hanatoxins from Grammostola rosea are used ubiquitously as specific ligands of voltage-gated calcium and potassium channels, respectively (8, 9). At the very same time, spider toxins that specifically recognize different targets may serve as leads for drug and insecticide discovery and thus find application in medicine and green biotechnology (10 -13).Spider venoms are complex mixtures of compounds of diverse chemical nature varying from inorganic salts to high molecular weight proteins (7,14). However, preference is usually given to a certain chemical framework, and the major active constituents of spider venoms currently known can be allocated into four large structural groups. (a) Acylpolyamine toxins that block ionotropic receptors and ion channels with average low specificity are produced by several families of spiders, most nota...

Venomics of Remipede Crustaceans Reveals Novel Peptide Diversity and Illuminates the Venom’s Biological Role

“…However, in addition to the previously reported xibalbin 1 and the extremely highly expressed xibalbin 2, we also identified a highly unusual family of double ICK domain (dICK) peptides, xibalbin 3. In stark contrast to the ubiquity of single ICK domain peptides, dICKs have previously only been described from venoms from the mygalomorph spiders Haplopelma schmidtii (tau-TRTX-Hs1a, henceforth Hs1a) [ 73 ] and Hadronyche infensa (pi-HXTX-Hi1a, henceforth Hi1a) [ 74 ] as well as the araneomorph spider Cheiracanthium punctorium (delta-MGTX-Cp1, henceforth Cp1) [ 75 ]. In the cases of the mygalomorph toxins Hi1a and Hs1a, this unique double neurotoxin domain architecture allows the toxins to act as bivalent ligands that bind virtually irreversibly to their molecular target [ 73 , 74 ].…”

“…The dICK architecture of the cytolytic peptide Cp1 also likely enables a bivalent mechanism of action. Cp1s are the primary insecticidal peptides in the venom of C. punctorium and have LD 50 values that are up to several orders of magnitude more potent than what is typical for cytolytic toxins [ 75 ]. The presence of two homologous domains may lend Cp1 a targeted cytolytic activity that results in increased potency as a paralytic and lethal insecticidal toxin.…”

Neurotoxin Merging: A Strategy Deployed by the Venom of the Spider Cupiennius salei to Potentiate Toxicity on Insects

“…Among spiders, the "retrotibial apophysis clade" (RTA clade or family group) is considered to represent one of the highest evolved spider groups [24]. Modular toxins composed of two ICK motifs in cheiracanthiids [25] or two α-helical motifs in zodariids [26] are reported. Within ctenids, lycosids, oxyopids [13,16], and Cupiennius [6], modular toxins composed first of an ICK-motif followed by an α-helical motif, or vice versa, have been identified.…”

Secreted Cysteine-Rich Repeat Proteins “SCREPs”: A Novel Multi-Domain Architecture

“…Even greater evidence supporting this notion was discovered after investigation of CpTx-1; a double-ICK peptide from the venom of the spider Cheiracanthium punctorium. This two-domain toxin had an observed effect on the resting membrane potential and a positive shift in α-helical structure composition in bicelle suspension ( Vassilevski et al, 2010 ). These intriguing results indicate a possible interaction between CpTx-1 and both ion channels and the surrounding lipid membrane environment, a mechanism that has been shown to be important in many other toxins ( Zhang et al, 2018 ).…”