Is a Modified Actin the Key to Toxin Resistance in the Nudibranch Chromodoris? A Biochemical and Molecular Approach

Five Chromodoris species from North Sulawesi, Indonesia, were investigated for their sequestration of marine natural products. The cytotoxic 2-thiazolidinone macrolide latrunculin A (LatA) was the major metabolite in all examined species, as well one associated sponges Cacospongia mycofijiensis (Kakou, Crews & Bakus, 1987), supporting a dietary origin LatA. Furthermore, LatA secreted with mucus trail, suggesting possible use short-range chemical communication. MALDI MS-Imaging revealed an accumulation throughout mantle tissue, glands, and especially vacuoles dermal formations (MDFs). Cytotoxicity isolated tested HEK-293 cells, confirming that targets actin cytoskeleton. In vivo toxicity experiments sacoglossan Elysia viridis (Montagu, 1804) showed 100% mortality, but survival specimens, demonstrating resistance to novel isoform detected two amino acid substitutions at ‘nucleotide binding’ cleft, binding site These are suggested cause insensitivity against LatA, thus enabling storage toxin within body slugs’ own defense.