Regulation of Sea Urchin Sperm Cyclic AMP-Dependent Protein Kinases by an Egg Associated Factor1

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Abstract
Experiments were designed to determine whether the elevation of sea urchin sperm cyclic AMP (cAMP) concentrations results in an activation of sperm cAMP-dependent protein kinases. The protein kinase activity ratio (enzyme activity in the absence of added cAMP/enzyme activity in the presence of 1.8 µM cAMP) varied between 0.1–0.2 under basal conditions, but increased to ∼0.3 in cells treated with 1.5 mM theophylline. A fucose-sulfate rich factor (FS-1) purified from the jelly coat of sea urchin eggs markedly increased sperm cAMP concentrations and increased the protein kinase activity ratio to values >0.8. After addition of FS-1 to the spermatozoa, the protein kinase activity ratio was increased to maximal values within 15 sec, but declined to near basal values within 5 min. The sperm cAMP concentrations followed a similar time course in response to FS-1. In the absence of added Ca2+, FS-1 failed to elevate either sperm cAMP concentrations or the protein kinase activity ratios. Ca2+ transport antagonists such as verapamil and D-600, when added to spermatozoa in the presence of Ca2+, blocked both FS-1-induced elevations of cAMP concentrations and the activation of the cAMP-dependent protein kinase. These data demonstrate that the elevation of sperm cAMP concentrations result in an activation of the sperm cAMP-dependent protein kinase. Since D-600 and verapamil block the elevation of cAMP and the activation of the cAMP-dependent protein kinase in response to FS-1, it appears that Ca2+ may function as the mediator of the effects of FS-1 on sperm cAMP concentrations.

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