Submitted February 11, 2008
Returned for revision March 5, 2008
Accepted April 8, 2008
Gamete Biology
Molecular Mechanisms Determining Sperm Motility Initiation in Two Sparids (Sparus aurata and Lithognathus mormyrus)
Loredana Zilli ,
Roberta Schiavone ,
Carlo Storelli ,
and
Sebastiano Vilella *
* To whom correspondence should be addressed. E-mail: sebastiano.vilella{at}unile.it.
Abstract
Molecular mechanisms involved in sperm motility initiation in two sparids (Sparus aurata and Lythognathus mormyrus) have been studied. Our comparative study demonstrates that osmolality is the key signal in sperm motility activation in both species whereas K+ and Ca2+ do not have any role. However the straight-line velocity (VSL) resulted significantly different when measured in sperm activated with non-ionic and/or calcium-free solutions with respect to that measured in seawater-activated sperm. In both species motility initiation depends on cAMP-dependent protein phosphorylation. The phosphorylation/dephosphorylation pattern in gilthead and striped sea bream resulted quite different. In gilthead sea bream the phosphorylated proteins have MWs of 174, 147, 138, 70 and 15-9 kDa, while those dephosphorylated 76, 57 and 33 kDa. In striped sea bream phosphorylation after sperm motility activation occurred on proteins with 174, 147, 103, 96, 61, 57 and 28 kDa, while only one protein of 70 kDa resulted dephosporylated. MALDI-TOF analyses allowed the identification of the following proteins: a) in gilthead sea bream the 15-9 kDa proteins that were phosphorylated after motility activation include an A kinase anchor protein (AKAP), an acetyl-CoA synthetase and a protein phosphatase inhibitor; b) in striped sea bream 103 and 61 kDa proteins that were phosphorylated after motility activation were identified as a phosphatase (myotubularin related protein 1) and a kinase (DYRK3), respectively.
Key words:
Signal transduction •
Sperm •
Sperm motility and transport
