Structures and biological activities of novel phosphonoglycosphingolipids.

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In the present study, chemical structure and histohogical localization of a major phosphonoglycosphingolipid of nerve fibes of Aplysia kurodai, a sea gastropod, were identified.1. Chemical structure of FGL-IIb: The complete structure was determined as 3,4-0-(1-carboxy-ethylidene)Ga1 1 3GalNAc 1 3[Fuc 1 2](2-aminoethylphosphony1 6)Ga1 1 4Glc 1 1-ceramide using GC-MS, NMR and chemical methods including permethylation etc. This is the first pyruvate containing sphingolipid so far reported in the animal. The basic structure of FGL-IIb is the same with that reported by us for the three major phosphonoglycosphingolipids of the skin of Aplysia, namely N-Ac galactosaminyl 1 3lactosy1-1 ceramide. Pyruvate in the molecule may make FGL-IIb more acidic than other phosphonoglycosphingolipids identified by us.2. Tissue distribution of FGL-IIb and immunochemically related glycolipids: Anti FGL-IIb antiserum was raised in the rabbit and this polyclonal antiserum was used for immunochemical and immunohistochemical studies with HRP staining. Narve bundles in the nerve fibers, ganglia and skin were stained. Other components including nerve cell bodies and neuropil were not stained at all. The reactivity of FGL-IIb to the antiserum was abolished by esterification of FGL-IIb and the lost activity was recovered by saponifiction. This indicates that free carboxyl of the pyruvic acid of FGL-IIb is responsible for the antigenicity of FGL-IIb.Besides FGL-IIb, other phosphonoglycosphingolipids identified in the nerve fiber of Aplysia as FGL-I, FGL-IIa, FGL-V and F-9 were also stained with the antiserum on TIC indicating that these glycolipids share the same epitope with FGL-IIb against the antibody. Pretreatment of tissues with chloroform-methanol mixture completely abolished the staining of nerve bundles.These results reveal that only the nerve bundles in Aplysia tissues contain very acidic glycolipids as FGL-IIb, indicating some neurobiological significances of these glycolipids.