Incorporation of intrastriatally injected [³H]fucose into electrophoretically separated synaptosomal glycoproteins. I. Turnover and molecular weight estimations

The radioactivity profiles of electrophoresed neostriatal P₂ fraction glycoproteins were examined at a series of times (2.5, 3 and 4 h; 1, 5 and 10 days) following intracranial injections of [³H]fucose into the neostriatum. Ten major fucosylglycoprotein peaks were discerned in these profiles and certain aspects of their metabolism were characterized. The half-life of fucosylglycoproteins in the P₂ fraction was estimated to be 9.7 days. The half-lives of the individual glycoprotein peaks ranged from 4.9 to 17.9 days. The apparent molecular weights of the glycoprotein peaks obtained by our procedures ranged from 32,000 to 180,000 daltons. One peak (peak VIII) incorporated radioactivity primarily at short intervals following the injection. The time course of[³H] fucose incorporation into this peak suggests involvement in the transport, activation and/or incorporation of fucose in brain. Since intracranial injections of [³H]fucose are incorporated into proteins in the cell body, synaptosomal fractions from caudate neurons alone are labeled by this technique. This may be useful in separating pre- and postsynaptic glycoprotein biochemistry. Finally, we tentatively propose that the glycoprotein peaks observed in neostriatum may be identical to previously isolated glycoproteins of known function or subcellular location.