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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
Author(s) -
Nomura Mamoru,
Inaba Kazuo,
Morisawa Masaaki
Publication year - 2000
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1046/j.1440-169x.2000.00489.x
Subject(s) - calmodulin , sperm motility , sperm , motility , protein kinase a , cyclic adenosine monophosphate , microbiology and biotechnology , biology , phosphorylation , chemistry , biochemistry , enzyme , receptor , genetics
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.