The Toxins of Nemertean Worms

Abstract

Most ribbon worms (phylum: Nemertea) are found in marine environments, where they act as predators and scavengers. They are characterized by an eversible proboscis that isused to hunt for prey and thick mucus covering their skin. Both proboscis and epidermal mucus mediate toxicity to predators and preys. Research into the chemical nature of the substances that render toxicity has not been extensive, but it has nevertheless led to the identification of several compounds of potential medicinal use or for application in biotechnology. This review provides a complete account of the current status of research into nemertean toxins.

Proteo-Transcriptomic Analysis Identifies Potential Novel Toxins Secreted by the Predatory, Prey-Piercing Ribbon Worm Amphiporus lactifloreus

“…The first and most abundant group comprised proteinases, including metalloproteinase M12 candidates with particularly high expression levels. The second group included actitoxin-like transcripts similar to short cnidarian actitoxins, which feature a cysteine-rich Kunitz-BPTI domain, and larger plancitoxin-like transcripts identified in other nemertean transcriptomes [2,18]. This group also included transcripts related to three clades of the inhibitor cystine knot (ICK)/knottin family, specifically conotoxin-like proteins featuring 4-C scaffolds (putative R-superfamily conotoxins [23] known from Villepin's cone, Conus villepinii), conotoxin-like proteins featuring 8-C scaffolds (similar to xibalbin-1 ICK sequences in remipede and several spider-like venoms [24,25]) and ICK-like calcium channel inhibitors from scorpions.…”

“…Nemertea is a phylum of unsegmented worms (ribbon worms) featuring 1300 mostly marine species. It belongs to the disputed superphylum Lophotrochozoa, which contains one third of all marine animals, including sensu stricto polychaetes, mollusks, brachiopods and phoronids [1][2][3]. Nemertean toxins were first discovered in the epidermal mucus [2] and research has focused on small-molecule components, such as tetrodotoxin and other alkaloids.…”

“…It belongs to the disputed superphylum Lophotrochozoa, which contains one third of all marine animals, including sensu stricto polychaetes, mollusks, brachiopods and phoronids [1][2][3]. Nemertean toxins were first discovered in the epidermal mucus [2] and research has focused on small-molecule components, such as tetrodotoxin and other alkaloids. Few peptide or protein components have been isolated, expressed and characterized in terms of structure and activity [2].…”

“…Comprehensive sequence, structural and pharmacological data are only available for a handful of proteins from three species in the class Pilidiophora: Cerebratulus lacteus (cytotoxin A-III and neurotoxins B-II and B-IV), Parborlasia corrugatus (parbolysin), and Lineus longissimus (nemertides α-1, α-2 and β-1). These toxins have been discussed in a comprehensive review [2].…”

“…These toxins were identified in all nine species, representing all three nemertean classes: Pilidiophora (Cerebratulus marginatus, Lineus lacteus, L. longissimus, and Lineus ruber), Palaeonemertea (Cephalothrix hongkongiensis, Cephalothrix linearis, and Tubulanus polymorphus) and Hoplonemertea (Malacobdella grossa and Paranemertes peregrina). However, the only transcripts Nemertean toxins were first discovered in the epidermal mucus [2] and research has focused on small-molecule components, such as tetrodotoxin and other alkaloids. Few peptide or protein components have been isolated, expressed and characterized in terms of structure and activity [2].…”