Signaling Pathways in Ascidian Oocyte Maturation: The Roles of cAMP/Epac, Intracellular Calcium Levels, and Calmodulin Kinase in Regulating GVBD
Signaling Pathways in Ascidian Oocyte Maturation: The Roles of cAMP/Epac, Intracellular Calcium Levels, and Calmodulin Kinase in Regulating GVBD
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DOI：
10.1002/mrd.21349
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发表时间：
2011-10-01
影响因子：
2.5
通讯作者：
Lambert, Charles C.
中科院分区：
文献类型：
--
作者：
Lambert, Charles C.
大多数成熟的海鞘卵母细胞在被卵巢释放到海水中时经历生殖囊泡破裂（GVBD）。酸性海水阻断了这一点，但卵母细胞可以通过提高pH值，通过细胞渗透形式增加细胞内cAMP水平，抑制其分解或引起其合成来刺激。Boltenia villosa卵母细胞在这些药物的作用下发生GVBD。然而，cAMP受体蛋白激酶A（PKA）似乎并不参与，因为卵母细胞不受激酶抑制剂H-89的影响。此外，PKA非依赖性Epac激动剂8 CPT-2 Me-cAMP在酸性海水中刺激GVBD。GVBD在无钙海水（CaFSW）中被抑制，并通过10 μ M浓度的细胞内钙螯合剂BAPTA-AM。当ryanodine受体（RYR）被丁卡因或钌红阻断时，GVBD也被抑制，但不被IP 3抑制剂D-609阻断。二甲基苯并蒽，一种蛋白激酶激活剂，绕过这一封锁，并刺激GVBD在BAPTA，丁卡因，或钌红阻断卵母细胞。最后，钙调蛋白激酶抑制剂KN-93在10 μ M时阻断GVBD。这篇文章和之前的文章支持这样的假设，即卵泡细胞响应pH值升高而产生的成熟诱导物质激活了G蛋白，从而触发cAMP的合成。cAMP然后激活Epac分子，其引起来自内质网RYR的细胞内钙的增加。增加的细胞内钙随后激活钙调蛋白激酶，导致cdc 25磷酸酶活性增加，激活MPF并使卵母细胞进入减数分裂。
Most mature ascidian oocytes undergo germinal vesicle breakdown (GVBD) when released by the ovary into seawater. Acidic seawater blocks this, but the oocytes can be stimulated by raising the pH, increasing intracellular cAMP levels by cell permeant forms, inhibiting its breakdown or causing its synthesis. Boltenia villosa oocytes undergo GVBD in response to these drugs. The cAMP receptor protein kinase A (PKA), however, 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 seawater. GVBD is inhibited in calcium-free seawater (CaFSW), and by 10 mu M concentrations of the intracellular calcium chelator BAPTA-AM. GVBD is also inhibited when the ryanodine receptors (RYR) are blocked by tetracaine or ruthenium red, but not by the IP3 inhibitor D-609. Dimethylbenzanthracene, a protein kinase activator, bypasses this block and stimulates GVBD in BAPTA-, tetracaine-, or ruthenium red-blocked oocytes. Finally, the calmodulin kinase inhibitor KN-93 blocks GVBD at 10 mu M. This and preceding articles support the hypothesis that the maturation-inducing substance produced by the follicle cells in response to increased pH activates a G protein that triggers cAMP synthesis. The cAMP then activates an Epac molecule, which causes an increase in intracellular calcium from the endoplasmic reticulum RYR. The increased intracellular calcium subsequently activates calmodulin kinase, causing an increase in cdc25 phosphatase activity, activating MPF and the progression of the oocyte into meiosis.