Effect of KN-62, a selective inhibitor of calmodulin-dependent kinase II, on mouse oocyte activation.

PURPOSE

Our purpose was to determine the association of calmodulin-dependent protein kinase II (CaMKII) with oocyte activation and to explore the network of protein kinases during mammalian fertilization.

METHODS

Mouse M-II oocytes were collected after superovulation induced by PMSG-hCG injection. The oocytes were inseminated or artificially activated by Ca ionophore (A23187) or 12-O-tetradecanoyl phorbol 13-acetate (TPA). The effects of KN-62, a specific and selective inhibitor of calmodulin-dependent protein kinase II, on second polar body emission (2PBE), pronuclear formation (PF), and cortical granule exocytosis (CGE) during fertilization or after artificial oocyte activation were investigated.

RESULTS

KN-62 inhibited 2PBE and PF after sperm or Ca ionophore inducing activation. Additionally, PF was inhibited by KN-62 after TPA activation, whereas KN-62 did not inhibit CGE in any case. KN-04, an inactive form of KN-62, did not inhibit significantly 2PBE, CGE, or PF. When oocytes were exposed to KN-62 after Ca ionophore or TPA activation, no inhibitory effects on 2PBE or PF were observed.

CONCLUSIONS

The CaMKII activation that occurs after fertilization or artificial activation of mouse oocytes is presumably secondary to increases in the intracellular free calcium concentration. As determined by the use of inhibitor, CaMKII activity is associated with 2PBE and PF but not with CGE.