Marine organisms are a rich source of molecules that alter mammalian neuroactivity. We carried out a bioactivity-guided screening using mouse behavior and highly sensitive in vitro electrophysiological assays.  An aqueous extract from a Cinachyrella marine sponge potently modified the functional properties of mammalian ionotropic glutamate receptors. Further isolation, functional characterization, and structural resolution yielded a new tetrameric member of the sponge galactose-binding lectin, or galectin, family. The amino acid sequences of the CchGs confirmed that the proteins were distant orthologues of animal prototype galectins.  The crystallographic structure of CchGs at 2.1 � revealed that the lectin monomers associate non-covalently into a toroid-shaped tetramer that has not been observed in previously resolved galectin structures. Purified CchGs potentiated steady-state currents and slowed desensitization of mammalian glutamate receptors expressed in heterologous cells.  This unexpected biological activity suggests that analysis of related mammalian galectin proteins will yield further glycobiological and neurophysiological insights.

Novel tetrameric galectin from a marine sponge potentiates mammalian glutamate receptor function

244th National Meeting (2012)

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