The author Charles C. Lambert is deceased; June 1, 2011.
Signaling pathways in ascidian oocyte maturation: The roles of cAMP/Epac, intracellular calcium levels, and calmodulin kinase in regulating GVBD†
Article first published online: 19 JUL 2011
Copyright © 2011 Wiley Periodicals, Inc.
Molecular Reproduction and Development
Special Issue: From Sea to Land at The Friday Harbor Laboratories
Volume 78, Issue 10-11, pages 726–733, October - November 2011
How to Cite
Lambert, C. C. (2011), Signaling pathways in ascidian oocyte maturation: The roles of cAMP/Epac, intracellular calcium levels, and calmodulin kinase in regulating GVBD. Mol. Reprod. Dev., 78: 726–733. doi: 10.1002/mrd.21349
- Issue published online: 17 OCT 2011
- Article first published online: 19 JUL 2011
- Accepted manuscript online: 14 JUN 2011 09:27AM EST
- Manuscript Accepted: 7 JUN 2011
- Manuscript Received: 15 FEB 2011
Most mature ascidian oocytes undergo germinal vesicle breakdown (GVBD) when released by the ovary into sea water (SW). Acidic SW blocks this but they can be stimulated by raising the pH, increasing intracellular cAMP levels by cell permeant forms, inhibiting its breakdown or causing synthesis. Boltenia villosa oocytes undergo GVBD in response to these drugs. However, the cAMP receptor protein kinase A (PKA) does not appear to be involved, as oocytes are not affected by the kinase inhibitor H-89. Also, the PKA independent Epac agonist 8CPT-2Me-cAMP stimulates GVBD in acidic SW. GVBD is inhibited in calcium free sea water (CaFSW). The intracellular calcium chelator BAPTA-AM blocks GVBD at 10 µM. GVBD is also inhibited when the ryanodine receptors (RYR) are blocked by tetracaine or ruthenium red but not by the IP3 inhibitor D-609. However, dimethylbenzanthracene (DMBA), a protein kinase activator, stimulates GVBD in BAPTA, tetracaine or ruthenium red blocked oocytes. The calmodulin kinase inhibitor KN-93 blocks GVBD at 10 µM. This and preceding papers support the hypothesis that the maturation inducing substance (MIS) produced by the follicle cells in response to increased pH causes activation of a G protein which triggers cAMP synthesis. The cAMP then activates an Epac molecule, which causes an increase in intracellular calcium from the endoplasmic reticulum ryanodine receptor. The increased intracellular calcium subsequently activates calmodulin kinase, which causes an increase in cdc25 phosphatase activity, activating MPF and the progression of the oocyte into meiosis. Mol. Reprod. Dev. 78:726–733, 2011. © 2011 Wiley Periodicals, Inc.