Sponge-derived neurotoxic substances : Structure, Bioactivity, and their cellular localization.

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In the present study, we identified new polyamines from a Okinawan sponge Axinissa aculeate that modulate ligand binding to NMDA type glutamate receptors. These polyamines may also function as a factor involved in silica biomineralization in the sponge. From the same extract, we identified new peptides containing polyamine in the substructure and named aculeines. This novel highly modified peptide showed strong convulsant actions in mice. We also isolated Cribropurine, a new purine from a Micronesian sponge Chribrocharina olemda. Cribroprine elicited a seizure-like spontaneous current in rat hippocampal neuron. A lipophilic extract of the sponge Raspailia sp. contained raspailol as seizure-inducing factor in mice. Okinawan sponge Spongosolites afforded an isolation of protein toxin Soritesidine. A terminal amino acid sequence for sotitesidine was determined We identified a cell where an excitatory amino acid dysiherbaine was localized. The cell was identified to be a cyanobacteria Synechosystis sp based on its 16S rDNA sequence This result suggested that dysiherbaine was a cyanobacterial product This species also contained 6-phospholylated deoxynojirimycin derivatives. Investigation of an aqueous extract that exhibited AMPAKine like activity resulted in separation of bioactive fractions. One of the active fractions was shown to contain lectin based on its hemagglutinating activity. The lectin- containing fraction showed AMPAKine-like activity whereas the fraction containing small molecule was responsible for seizure-induction in mice. The preset study demonstrated that toxic extracts that induce convulsion in mice is a interesting source of neuron active compounds that can be useful tools in neurobiology.