Cone snail

Abstract: Conopeptides are a diverse group of recently evolved venom peptides used for prey capture and/or defense. Each species of cone snails produces in excess of 1000 conopeptides, with those pharmacologically characterized (≈ 0.1%) targeting a diverse range of membrane proteins typically with high potency and specificity. The majority of conopeptides inhibit voltage- or ligand-gated ion channels, providing valuable research tools for the dissection of the role played by specific ion channels in excitable cells. It is noteworthy that many of these targets are found to be expressed in pain pathways, with several conopeptides having entered the clinic as potential treatments for pain [e.g., pyroglutamate1-MrIA (Xen2174)] and one now marketed for intrathecal treatment of severe pain [ziconotide (Prialt)]. This review discusses the diversity, pharmacology, structure-activity relationships, and therapeutic potential of cone snail venom peptide families acting at voltage-gated ion channels (ω-, μ-, μO-, δ-, ι-, and κ-conotoxins), ligand-gated ion channels (α-conotoxins, σ-conotoxin, ikot-ikot, and conantokins), G-protein-coupled receptors (ρ-conopeptides, conopressins, and contulakins), and neurotransmitter transporters (χ-conopeptides), with expanded discussion on the clinical potential of sodium and calcium channel inhibitors and α-conotoxins. Expanding the discovery of new bioactives using proteomic/transcriptomic approaches combined with high-throughput platforms and better defining conopeptide structure-activity relationships using relevant membrane protein crystal structures are expected to grow the already significant impact conopeptides have had as both research probes and leads to new therapies.

Abstract: The predatory cone snails (Conus) are among the most successful living marine animals (∼500 living species). Each Conus species is a specialist in neuropharmacology, and uses venom to capture prey, to escape from and defend against predators and possibly to deter competitors. An individual cone snail’s venom contains a diverse mixture of pharmacological agents, mostly small, structurally constrained peptides (conotoxins). Individual peptides are selectively targeted to a specific isoform of receptor or ion channel. A variety of such targets have been identified, including many voltage-gated and ligand-gated ion channel subtypes, as well as G protein-linked receptors. Although there are only a few widely shared structural motifs in conotoxins (the majority of the >25,000 peptides in these venoms probably belong to only half a dozen gene superfamilies), the sequences of peptides are remarkably divergent from one Conus species to another. We suggest that cone snails undergoing speciation have, in effect, a mutator phenotype which acts specifically on the gene segment encoding the mature toxin region. In their 50 million years of evolution, cone snails anticipated many features of the modern drug industry: disposable hypodermic needles, combination drug therapy, and combinatorial strategies for drug discovery. Recent results indicate that the Conus peptide system may provide a novel paradigm for designing ligands that discriminate between closely related members of large families of receptors and ion channels. Many Conus peptides may be “Janus-ligands,” with two distinct recognition faces oriented in different directions, a design which should make far greater target specificity possible.

Abstract: Venomous animals are thought to inject the same combination of toxins for both predation and defence, presumably exploiting conserved target pharmacology across prey and predators Remarkably, cone snails can rapidly switch between distinct venoms in response to predatory or defensive stimuli Here, we show that the defence-evoked venom of Conus geographus contains high levels of paralytic toxins that potently block neuromuscular receptors, consistent with its lethal effects on humans In contrast, C geographus predation-evoked venom contains prey-specific toxins mostly inactive at human targets Predation- and defence-evoked venoms originate from the distal and proximal regions of the venom duct, respectively, explaining how different stimuli can generate two distinct venoms A specialized defensive envenomation strategy is widely evolved across worm, mollusk and fish-hunting cone snails We propose that defensive toxins, originally evolved in ancestral worm-hunting cone snails to protect against cephalopod and fish predation, have been repurposed in predatory venoms to facilitate diversification to fish and mollusk diets

Abstract: Peptide therapeutics are acclaimed as a promising addition to the pharmaceutical arena, and they continue to attract interest due to their high potency, bioavailability, and fewer concerns with toxicity, drug to drug cross-reactions, and tissue accumulation. Around 700 species of marine snails of the genus Conus are distributed throughout tropical and subtropical waters. As different species preferentially hunt fish, worms, or molluscs they are categorized as piscivorous, vermivorous, or molluscivorous, respectively, although some cone snail species can feed on more than one prey type. These slow-moving creatures evolved into predators through incorporation of a specialized envenomation apparatus that enables them to quickly subdue their fast-moving prey. Conotoxins target a wide range of receptors and ion channels with unparalleled potency and selectivity. They have consequently become the subject of intense research in light of their immense diagnostic and therapeutic potential and are the focus of this review.