Possible participation of calmodulin in the decondensation of nuclei isolated from guinea pig spermatozoa

• Published in: Zygote (Cambridge) 2010-08, Vol.18 (3), p.217-229
• Main Authors: Zepeda-Bastida, Armando, Chiquete-Felix, Natalia, Ocampo-Lopez, Juan, Uribe-Carvajal, Salvador, Mujica, Adela
• Format: Article
• Language: English
• Subjects: Animals; Calmidazolium; Calmodulin - antagonists & inhibitors; Calmodulin - metabolism; Cell Nucleus - metabolism; Guinea Pigs; Heparin; Imidazoles - pharmacology; Male; Myosin–actin complex; Spermatozoa - cytology; Spermatozoa - metabolism; Xenopus laevis
• ISSN: 0967-1994; 1469-8730
• DOI: 10.1017/S0967199409990220

The guinea pig spermatozoid nucleus contains actin, myosin, spectrin and cytokeratin. Also, it has been reported that phalloidin and/or 2,3-butanedione monoxime retard the sperm nuclear decondensation caused by heparin, suggesting a role for F-actin and myosin in nuclear stability. The presence of an F-actin/myosin dynamic system in these nuclei led us to search for proteins usually related to this system. In guinea pig sperm nuclei we detected calmodulin, F-actin, the myosin light chain and an actin-myosin complex. To define whether calmodulin participates in nuclear-dynamics, the effect of the calmodulin antagonists W5, W7 and calmidazolium was tested on the decondensation of nuclei promoted by either heparin or by a Xenopus laevis egg extract. All antagonists inhibited both the heparin- and the X. laevis egg extract-mediated nuclear decondensation. Heparin-mediated decondensation was faster and led to loss of nuclei. The X. laevis egg extract-promoted decondensation was slower and did not result in loss of the decondensed nuclei. It is suggested that in guinea pig sperm calmodulin participates in the nuclear decondensation process.