The role of cAMP and calcium-dependent protein phosphorylation in the initiation and maintenance of sperm flagellar motility will be studied. Both cAMP and calcium are known to be involved in the biochemical mechanisms regulating motility in flagella. cAMP is known to stimulate motility in sperm. Calcium has several effects on sperm motility. At low concentrations of calcium (less than 10 to the-6 M) motility is maintained, at intermediate concentrations 10 to the-6 to 10 to the-5 M), it alters the wave form while at 10 to the-4 M or higher it inhibits motility. The only known action of cAMP is activation of cAMP-dependent protein kinase. However, the phosphoprotein substrates for this enzyme and their functional role in motility of flagella remains to be defined. The occurrence and functional role of calcium-dependent phosphoproteins in sperm flagella and their role in motility also remains to be investigated. These questions will be approached by: (1) Determining the occurrence of cAMP- and calcium-dependent protein phosphorylation reactions in isolated sperm flagella and how these reactions are related to motility; (2) Identification and purification of the protein kinases determining the sensitivity of protein phosphorylation to the presence of cAMP or calcium; (3) Identification and purification of cAMP- and calcium-dependent phosphoproteins; (4) Determination of the subcellular and ultrastructural localizations of the protein kinases and phosphoproteins; and (5) Definition of the functional role of the cAMP- and calcium-dependent phosphoproteins in the regulation of motility by a) treatment of motile flagellar models with specific antibodies to the kinases and phosphoproteins, and b) identification and utilization of specific chemical probes to alter motility and protein phosphorylation. To approach these problems a detergent-permiabilized cAMP-and calcium-sensitive model system has been developed which allows motility and protein phosphorylation to be measured under identical experimental conditions. The results obtained should allow a better understanding of the several disease states typified by altered axonemal motility.
NIH ExPorter
NIH ExPorter