INHIBITION OF SEA-URCHIN FERTILIZATION BY JASPISIN, A SPECIFIC INHIBITOR OF MATRIX METALLOENDOPROTEINASE

Jaspisin, originally isolated from a marine sponge as an inhibitor of the hatching of the sea urchin (Hemicentrotus pulcherrimus) embryo, ca uses inhibition of sea urchin fertilization. Electron microscopic exam ination revealed that the acrosome reaction was induced in jaspisin-tr eated sperm when they were incubated with an intact egg. The acrosome- reacted sperm bound to the vitelline layer by the acrosomal material s urrounding the acrosomal process. However, fusion of the acrosomal pro cess and the egg plasma membrane failed to take place. Membrane potent ial changes were monitored using eggs preloaded with a membrane potent ial-sensitive fluorochrome, di-8-ANEPPS. Depolarization of the membran e potential, normally observed in the fertilized egg was not observed in the egg inseminated in the presence of jaspisin, indicating the abs ence of electrical continuity between the jaspisin-treated egg and spe rm. Jaspisin inhibited the activities of matrix metallo-endoproteinase members but not of other types of proteinases. These results provide strong, albeit indirect, evidence that a matrix metallo-endoproteinase (s) is involved in the process of gamete fusion during sea urchin fert ilization.