Calcium signaling by cyclic ADP-ribose, NAADP, and inositol trisphosphate are involved in distinct functions in ascidian oocytes
Calcium signaling by cyclic ADP-ribose, NAADP, and inositol trisphosphate are involved in distinct functions in ascidian oocytes
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DOI：
10.1074/jbc.273.23.14566
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发表时间：
1998-06-05
影响因子：
4.8
通讯作者：
Villaz, M
中科院分区：
文献类型：
--
作者：
Albrieux, M;Lee, HC;Villaz, M
ADP-核糖基环化酶催化两种结构和功能不同的 Ca2+ 释放分子的合成，即来自 β-NAD 的环状 ADP-核糖 (cADPR) 和来自 β-NADP 的烟酸腺嘌呤二核苷酸磷酸 (NAADP)。它们在海鞘卵母细胞中的 Ca2+ 动员作用与 肌醇 1,4,5-三磷酸 (InsP(3))。卵母细胞的受精伴随着卵母细胞 Ca2+ 电流的减少和由于细胞表面添加膜而导致的膜电容的增加。这两种电变化都可以通过通过贴片吸管将纳摩尔浓度的 cADPR 或其前体 β-NAD 灌注到未受精的卵母细胞中来诱导。 β-NAD 诱导的变化表现出明显的延迟，与其酶促转化为 cADPR 一致。通过在卵母细胞中预载 Ca2+ 螯合剂可以抑制 cADPR 诱导的变化，表明这种效应是由于 cADPR 诱导的 Ca2+ 释放所致。一致地，兰尼定（高浓度）或 8-氨基-cADPR（一种 cADPR 的特异性拮抗剂）（但不是肝素）抑制 cADPR 诱导的变化。两种抑制剂同样阻断通常在受精时发生的膜插入，这与兰尼碱受体介导的膜插入一致。 NAADP 的作用与 cADPR 的作用不同，尽管 NAADP 引起了类似的 Ca2+ 电流降低，但没有发生膜插入。此外，用 NAADP 预处理卵母细胞可抑制受精后 Ca2+ 振荡，而 cADPR 则不会。通过向卵母细胞灌注高浓度的InsP(3)可以人工诱导类似的Ca2+振荡，并且NAADP同样可以抑制这种InsP(3)诱导的振荡。这项工作表明，卵母细胞中存在三个独立的 Ca2+ 信号通路，并且每个通路都参与介导与受精相关的不同变化。结果与卵母细胞中 Ca2+ 储存的分层组织一致。
ADP-ribosyl cyclase catalyzes the synthesis of two structurally and functionally different Ca2+ releasing molecules, cyclic ADP-ribose (cADPR) from beta-NAD and nicotinic acid-adenine dinucleotide phosphate (NAADP) from beta-NADP, Their Ca2+-mobilizing effects in ascidian oocytes were characterized ire connection with that induced by inositol 1,4,5-trisphosphate (InsP(3)). Fertilization of the oocyte is accompanied by a decrease in the oocyte Ca2+ current and an increase in membrane capacitance due to the addition of membrane to the cell surface, Both of these electrical changes could be induced by perfusion, through a patch pipette, of nanomolar concentrations of cADPR or its precursor, beta-NAD, into unfertilized oocytes. The changes induced by beta-NAD showed a distinctive delay consistent with its enzymatic conversion to cADPR. The cADPR-induced changes were inhibited by preloading the oocytes with a Ca2+ chelator, indicating the effects were due to Ca2+ release induced by cADPR. Consistently, ryanodine (at high concentration) or 8-amino-cADPR, a specific antagonist of cADPR, but not heparin, inhibited the cADPR induced changes. Both inhibitors likewise blocked the membrane insertion that normally occurred at fertilization consistent with it being mediated by a ryanodine receptor. The effects of NAADP were different from those of cADPR, Although NAADP induced a similar decrease in the Ca2+ current, no membrane insertion occurred. Moreover, pretreatment of the oocytes with NAADP inhibited the post-fertilization Ca2+ oscillation while cADPR did not. A similar Ca2+ oscillation could be artificially induced by perfusing into the oocytes a high concentration of InsP(3) and NAADP could likewise inhibit such an InsP(3)-induced oscillation. This work shows that three independent Ca2+ signaling pathways are present in the oocytes and that each is involved in mediating distinct changes associated with fertilization. The results are consistent with a hierarchical organization of Ca2+ stores in the oocyte.