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Toxins modulating NaV channels are the most abundant and studied peptide components of sea anemone venom. Three type-II toxins, δ-SHTX-Hcr1f (= RpII), RTX-III, and RTX-VI, were isolated from the sea anemone Heteractis crispa. RTX-VI has been found to be an unusual analog of RTX-III. The electrophysiological effects of Heteractis toxins on nine NaV subtypes were investigated for the first time. Heteractis toxins mainly affect the inactivation of the mammalian NaV channels expressed in the central nervous system (NaV1.1–NaV1.3, NaV1.6) as well as insect and arachnid channels (BgNaV1, VdNaV1). The absence of Arg13 in the RTX-VI structure does not prevent toxin binding with the channel but it has changed its pharmacological profile and potency. According to computer modeling data, the δ-SHTX-Hcr1f binds within the extracellular region of the rNaV1.2 voltage-sensing domain IV and pore-forming domain I through a network of strong interactions, and an additional fixation of the toxin at the channel binding site is carried out through the phospholipid environment. Our data suggest that Heteractis toxins could be used as molecular tools for NaV channel studies or insecticides rather than as pharmacological agents.

the Kunitz/Bpti-type peptides are ubiquitous in numerous organisms including marine venomous animals. the peptides demonstrate various biological activities and therefore they are the subject of a number of investigations. We have discovered a new HciQ subfamily belonging to recently described multigene HcGS family of Heteractis crispa Kunitz-peptides. the uniqueness of this subfamily is that the HciQ precursors contain a propeptide terminating in Lys-Arg (endopeptidase cleavage site) the same as in the neuro-and cytotoxin ones. Moreover, the HCIQ genes contain two introns in contrast to HCGS genes with one intron. As a result of Sanger and amplicon deep sequencings, 24 HCIQ isoforms were revealed. The recombinant peptides for the most prevalent isoform (HCIQ2c1) and for the isoform with the rare substitution Gly17Glu (HCIQ4c7) were obtained. They can inhibit trypsin with K i 5.2 × 10 −8 M and K i 1.9 × 10 −7 M, respectively, and interact with some serine proteinases including inflammatory ones according to the SPR method. For the first time, Kunitz-peptides have shown to significantly increase neuroblastoma cell viability in an in vitro 6-OHDA-induced neurotoxicity model being a consequence of an effective decrease of ROS level in the cells. Kunitz-type proteinase inhibitors are present in various living organisms and in viruses. They are widely distributed and well-characterized in animals including marine invertebrates, snakes, spiders, ticks, flies and mammals 1. In spider, snake, scorpion, cone snail and sea anemone venoms Kunitz-peptides may exist in multiple isoforms possessing conserved BPTI-like fold but exhibit different biological activities 2-9. This phenomenon is associated with gene duplication and their diversification throughout adaptive evolution leading to the formation of families of evolutionarily related but functionally distinct genes 10. Among sea anemone transcriptomes, such multigene families have been discovered in Anemonia viridis 11 , Stichodactyla haddoni 12 , and Heteractis crispa 5. HCGS multigene family of H. crispa has been found to be divided in four distinct subfamilies (GS, RG, GG, and GN) forming the combinatory library of Kunitz/BPTI peptides 5. The group of HCGN peptides was presented by one sequence, different from other sequences that are characterized by a propeptide insertion containing the cleavage site Lys-Arg, and additional residues Ile-Gln at the N-terminus of a mature peptide. Its full-length homolog HMIQ3c1, containing a mature peptide with the same residues at N-terminus, was derived from the cDNA of the sea anemone Heteractis magnifica 13. The most abundant HCGS and HCRG peptides are being actively studied nowadays 14-17. The main targets of Kunitz-peptides are serine proteinases, such as trypsin and α-chymotrypsin.

Sea anemones produce pore-forming toxins, actinoporins, which are interesting as tools for cytoplasmic membranes study, as well as being potential therapeutic agents for cancer therapy. This investigation is devoted to structural and functional study of the Heteractis crispa actinoporins diversity. Here, we described a multigene family consisting of 47 representatives expressed in the sea anemone tentacles as prepropeptide-coding transcripts. The phylogenetic analysis revealed that actinoporin clustering is consistent with the division of sea anemones into superfamilies and families. The transcriptomes of both H. crispa and Heteractis magnifica appear to contain a large repertoire of similar genes representing a rapid expansion of the actinoporin family due to gene duplication and sequence divergence. The presence of the most abundant specific group of actinoporins in H. crispa is the major difference between these species. The functional analysis of six recombinant actinoporins revealed that H. crispa actinoporin grouping was consistent with the different hemolytic activity of their representatives. According to molecular modeling data, we assume that the direction of the N-terminal dipole moment tightly reflects the actinoporins’ ability to possess hemolytic activity.