Phosphorylation of IP3R1 and the regulation of [Ca2+]i responses at fertilization:: a role for the MAP kinase pathway
Phosphorylation of IP3R1 and the regulation of [Ca2+]i responses at fertilization:: a role for the MAP kinase pathway
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DOI：
10.1242/dev.02624
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发表时间：
2006-11-01
期刊：
影响因子：
4.6
通讯作者：
Fissore, Rafael A.
中科院分区：
文献类型：
--
作者：
Lee, Bora;Vermassen, Elke;Fissore, Rafael A.
迄今为止研究的大多数物种中，精子诱导的细胞内 Ca2+ 信号 ([Ca2+](i)) 是胚胎发育启动的基础。哺乳动物中的肌醇 1,4,5 三磷酸受体 1 型 (IP(3)R1) 或其在其他物种中的同源物被认为介导了大部分 Ca2+ 释放。 IP(3)R1 介导的 Ca2+ 释放在卵母细胞成熟过程中受到调节，使其在受精时达到最大效果，在哺乳动物卵中，受精发生在第二次减数分裂 (MII) 的中期。与此一致的是，这些物种中与受精相关的 [Ca2+]i 振荡在 MII 阶段最为显着。在这项研究中，我们研究了鸡蛋中 IP(3)R1 功能的分子基础。使用小鼠和非洲爪蟾卵，我们发现 IP(3)R1 在成熟和第一个细胞周期期间在 MPM2 可检测表位处被磷酸化，已知该表位是控制细胞周期的激酶的靶标。体外磷酸化研究表明，M 期激酶之一 MAPK/ERK2 在至少一个高度保守的位点磷酸化 IP(3)R1，并且其突变消除了该结构域中的 IP(3)R1 磷酸化。我们的研究还发现，在小鼠卵中观察到的 IP(3)R1 MPM2 反应性需要激活 MAPK/ERK 通路，并且在成熟过程中被剥夺 MAPK/ERK 通路的卵无法响应激动剂而启动正常的 [Ca2+](i) 振荡，并显示出 IP(3)R1 功能受损。这些发现将 M 相激酶的 IP(3)R1 磷酸化确定为卵子中 IP(3)R1 功能的调节机制，可优化受精时的 [Ca2+](i) 释放。
A sperm-induced intracellular Ca2+ signal ([Ca2+](i)) underlies the initiation of embryo development in most species studied to date. The inositol 1,4,5 trisphosphate receptor type 1 (IP(3)R1) in mammals, or its homologue in other species, is thought to mediate the majority of this Ca2+ release. IP(3)R1-mediated Ca2+ release is regulated during oocyte maturation such that it reaches maximal effectiveness at the time of fertilization, which, in mammalian eggs, occurs at the metaphase stage of the second meiosis (MII). Consistent with this, the [Ca2+] i oscillations associated with fertilization in these species occur most prominently during the MII stage. In this study, we have examined the molecular underpinnings of IP(3)R1 function in eggs. Using mouse and Xenopus eggs, we show that IP(3)R1 is phosphorylated during both maturation and the first cell cycle at a MPM2-detectable epitope(s), which is known to be a target of kinases controlling the cell cycle. In vitro phosphorylation studies reveal that MAPK/ERK2, one of the M-phase kinases, phosphorylates IP(3)R1 at at least one highly conserved site, and that its mutation abrogates IP(3)R1 phosphorylation in this domain. Our studies also found that activation of the MAPK/ERK pathway is required for the IP(3)R1 MPM2 reactivity observed in mouse eggs, and that eggs deprived of the MAPK/ERK pathway during maturation fail to mount normal [Ca2+](i) oscillations in response to agonists and show compromised IP(3)R1 function. These findings identify IP(3)R1 phosphorylation by M-phase kinases as a regulatory mechanism of IP(3)R1 function in eggs that serves to optimize [Ca2+](i) release at fertilization.