A Novel C1q Domain-Containing Protein Isolated from the Mollusk Modiolus kurilensis Recognizing Glycans Enriched with Acidic Galactans and Mannans

C1q domain-containing (C1qDC) proteins are a group of biopolymers involved in immune response as pattern recognition receptors (PRRs) in a lectin-like manner. A new protein MkC1qDC from the hemolymph plasma of Modiolus kurilensis bivalve mollusk widespread in the Northwest Pacific was purified. The isolation procedure included ammonium sulfate precipitation followed by affinity chromatography on pectin-Sepharose. The full-length MkC1qDC sequence was assembled using de novo mass-spectrometry peptide sequencing complemented with N-terminal Edman’s degradation, and included 176 amino acid residues with molecular mass of 19 kDa displaying high homology to bivalve C1qDC proteins. MkC1qDC demonstrated antibacterial properties against Gram-negative and Gram-positive strains. MkC1qDC binds to a number of saccharides in Ca2+-dependent manner which characterized by structural meta-similarity in acidic group enrichment of galactose and mannose derivatives incorporated in diversified molecular species of glycans. Alginate, κ-carrageenan, fucoidan, and pectin were found to be highly effective inhibitors of MkC1qDC activity. Yeast mannan, lipopolysaccharide (LPS), peptidoglycan (PGN) and mucin showed an inhibitory effect at concentrations three orders of magnitude greater than for the most effective saccharides. MkC1qDC localized to the mussel hemal system and interstitial compartment. Intriguingly, MkC1qDC was found to suppress proliferation of human adenocarcinoma HeLa cells in a dose-dependent manner, indicating to the biomedical potential of MkC1qDC protein.

Resources and structure of horsemussel Modiolus kurilensis settlements in Peter the Great Bay (the Sea of Japan)

Modiolus kurilensis F. R. Bernard, 1983 (Mollusca, Bivalvia) can be found in Peter the Great Bay (the Sea of Japan) both on soft and hard substrates, often together with the mussel Crenomytilus grayanus (Dunker, 1853); it is a promising commercial species. This mollusc is a by-catch when catching C. grayanus. The aim of the work was to assess M. kurilensis resources and settlement structure in Peter the Great Bay. The research was carried out in 2007–2018 by scuba-diving methods of hydrobiological research at the depths of down to 20 m. In total, the data were analyzed for 2,409 stations; M. kurilensis was found at 308 stations. Sampled molluscs were measured and weighed. The material was processed statistically and cartographically; the mean biomass and distribution density of M. kurilensis settlements were calculated. In total, 870 horsemussels were analyzed for studying the settlement structure. The following indicators were estimated: index of settling (ratio of the abundance of juvenile molluscs with a shell length of 1–30 mm (spat, yearlings) to the abundance of adults with a shell length of > 50 mm); index of maturation (ratio of the abundance of pre-reproductive molluscs with a shell length of 35–50 mm to the abundance of adults with a shell length of > 50 mm); index of replenishment of the commercial stock (ratio of the abundance of molluscs with a shell length of 95–100 mm (recruits) to the abundance of molluscs of commercial length of > 100 mm). The state of M. kurilensis population in Peter the Great Bay is stable: the ratio of molluscs of non-commercial length varies 52 to 86 % in most settlements, which indicates active natural reproduction and regular replenishment of the benthic part over many years. Replenishment of settlements with settling of both spat and yearlings depends on the presence of pelagic larvae in the plankton, while replenishment of the mature molluscs depends on favorable conditions for juvenile survival. In 2007–2018, the mean values of the indices of settling and maturation in M. kurilensis settlements in Peter the Great Bay were of (0.18 ± 0.07) and (0.05 ± 0.01), respectively. M. kurilensis resources are estimated at 27.1 thousand tons, and the commercial stock – at 16.4 thousand tons. The annual replenishment of the commercial stock of M. kurilensis in Peter the Great Bay is possible in a volume of more than 3 thousand tons. The mean value of the index of replenishment of the commercial stock is of (0.21 ± 0.03).

A NOVEL C1Q DOMAIN-CONTAINING PROTEIN ISOLATED FROM THE MOLLUSK MODIOLUS KURILENSIS RECOGNIZING GLYCANS ENRICHED WITH ACIDIC GALACTANS AND MANNANS IS VERY PROSPECTIVE FOR BIOMEDICAL PURPOSES

A novel C1qDC bivalve protein from the bivalve Modiolus kurilensis (MkC1qDC-1) was identified, isolated and characterized. MkC1qDC-1 demonstrated the inhibition of HeLa cell proliferation and recognition of some cancer cell phenotypes in comparative analysis on several cell lines, suggesting biomedical potential of this protein.