Stimulation of phospholipid turnover in isolated sea urchin sperm heads by the fucose-sulfate glycoconjugate that induces an acrosome reaction.

The fucose-sulfate glycoconjugate (FSG) component of sea urchin egg jelly that induces an acrosome reaction in spermatozoa-stimulated multiple Ca2+-dependent phospholipid changes in the sperm cell head and flagellum. When cells were radiolabeled with myo-[3H]inositol, FSG treatment decreased radioactivity in phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate within 30 s. In addition, FSG treatment elevated concentrations of phosphatidic acid in spermatozoa. The Ca2+-channel antagonist, verapamil, inhibited the effects of FSG on [3H]polyphosphoinositides and phosphatidic acid. To investigate the possible compartmentalization of phospholipid turnover, isolated heads and flagella were prepared. Treatment of sperm heads with FSG or the monovalent cation ionophore, gramicidin S, caused increased [3H]inositol phosphate and phosphatidic acid accumulation and induction of an acrosome reaction. Effects of FSG and gramicidin S on phosphatidic acid elevations in sperm heads and intact cells were inhibited by verapamil. FSG failed to cause detectable changes in [3H]inositol phosphate or phosphatidic acid concentrations in isolated flagellar preparations. However, when cells were treated with FSG and the flagella were isolated subsequently, phosphatidic acid concentrations in the flagellar preparations were increased.