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- Title
Cyclic AMP- and calmodulin-dependent phosphorylation of 21 and 26 kDa proteins in axoneme is a prerequisite for SAAF-induced motile activation in ascidian spermatozoa.
- Authors
Nomura, Mamoru; Inaba, Kazuo; Morisawa, Masaaki
- Abstract
Sperm activating and -attracting factor (SAAF), derived from the egg of the ascidian Ciona, activates sperm motility through adenosine 3′:5′-cyclic monophosphate (cAMP)-synthesis. A demembranated preparation of intact immotile sperm without SAAF was shown to require cAMP for reactivation. However, a demembranated preparation of intact motile sperm treated with SAAF did not require cAMP for reactivation, suggesting that cAMP is a prerequisite factor for SAAF-dependent activation of sperm motility. Furthermore, a cAMP-dependent protein kinase (PKA) inhibitor, H-89, was found to inhibit sperm motility. During in vivo or in vitro activation of sperm motility by SAAF or cAMP, a 26 kDa axonemal protein and 21 kDa dynein light chain were phosphorylated, respectively, suggesting the involvement of PKA-dependent phosphorylation of these proteins in sperm activation. The calmodulin antagonist, W-7, and an inhibitor of calmodulin-dependent myosin light chain kinase, ML-7, also inhibited the activation of sperm motility. Inhibition was reversed by the addition of phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Demembranated preparations of immotile sperm in the presence of W-7 or ML-7 were reactivated by cAMP, suggesting that calmodulin participated in sperm activation and that cAMP synthesis was followed by activation of a calmodulin-dependent mechanism.
- Subjects
CIONA; SPERM motility
- Publication
Development, Growth & Differentiation, 2000, Vol 42, Issue 2, p129
- ISSN
0012-1592
- Publication type
Article
- DOI
10.1046/j.1440-169X.2000.00489.x