Efforts to develop safe and effective methods to regulate human reproduction, both infertility and contraception, would be greatly enhanced by a more complete understanding of the regulatory mechanisms which control sperm functions. The long term goal of this proposal is to develop a sperm targeted contraceptive based on the interruption of sperm specific signaling pathway. There is ample evidence that cAMP and the cAMP-dependent protein kinase (PKA) are involved in the regulation of sperm motility. PKA is a multi-functional enzyme with a broad substrate specificity. Recent studies show that subcellular targeting of PKA is an important, if not essential, requirement for cAMP action. This targeting of PKA is mediated by binding of the regulatory subunits (R) with A-kinase anchoring proteins (AKAPs). If localized PKA action is important in somatic cells, such a mechanism is likely to be even more critical in the highly compartmentalized sperm cell. We and others have shown that the type II alpha (RIIalpha) isoform is detected exclusively in the flagellum suggesting an involvement in sperm motility regulation. On the other hand, the type I isoforms are associated mostly with the apical and equatorial segments of the sperm head, suggesting their involvement in acrosome reaction and/or sperm-egg fusion. This specific PKA localization to distinct subcellular regions are likely to be mediated by AKAPs. Bovine, mouse, monkey and human sperm all contain one predominant RIIalpha binding AKAP with Mr of approximately 110,000. Purification and partial amino acid sequences show that sperm AKAP 110 is a novel protein. We have also shown that membrane permeable peptides, designed to disrupt the interaction of RIIalpha with sperm AKAPs, arrest sperm motility. We hypothesize that PKA anchoring is essential for sperm motility and fertilization. The overall goal of this proposal is to define the role of PKA anchoring in sperm function. Specifically, we will determine the structure and function of AKAP 110, document the subcellular location of PKA regulatory subunits and their AKAPs and define the key biochemical mechanisms regulated by PKA/AKAP110 interaction. Studies outlined in this proposal will facilitate the design new and highly specific pharmacological reagents for inhibiting sperm function in vivo. Knowledge gained from these studies may also be useful for the diagnosis and treatment of patients with defects in sperm movement and fertility.
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