COMPARISON OF CA-2+ MOBILIZING ACTIVITIES OF CYCLIC ADP-RIBOSE AND INOSITOL TRISPHOSPHATE
COMPARISON OF CA-2+ MOBILIZING ACTIVITIES OF CYCLIC ADP-RIBOSE AND INOSITOL TRISPHOSPHATE
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DOI：
10.1091/mbc.1.3.279
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发表时间：
1990-02-01
期刊：
影响因子：
--
通讯作者：
LEE, HC
中科院分区：
文献类型：
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作者：
DARGIE, PJ;AGRE, MC;LEE, HC
我们之前已经证明，由海胆卵和哺乳动物组织中存在的酶产生的NAD+代谢物可以动员卵中的细胞内Ca2+。结构测定确定其为环化adp核糖，并命名为环化adp核糖（cyclic adp核糖，cADPR）。在这项研究中，用Ca2+指示剂和Ca2+特异性电极监测了cADPR和肌醇三磷酸（IP3）在海胆蛋匀浆中诱导的Ca2+动员。两种方法都表明，cADPR可以从鸡蛋匀浆中释放Ca2+。有证据表明，它不作为非特异性Ca2+离子载体或作为微粒体Ca2+运输的阻滞剂；相反，它很可能是通过一个特定的受体系统起作用的。其半最大有效浓度为18 nM，比IP3低7倍。cADPR的受体似乎与IP3的受体不同，因为肝素（一种IP3结合抑制剂）对cADPR的作用没有影响。cADPR和IP3诱导的Ca2+释放不是相加性的，而是呈反比关系，表明重叠储存被动员起来了。将cADPR微量注射到完整的卵子中，可诱导短暂的细胞内Ca2+变化并激活皮质反应。cADPR的体内有效性与IP3直接相当，两者都不需要外部Ca2+。此外，两者都能有效地激活卵子进行多次核循环和DNA合成。这些结果表明，cADPR可能是海胆卵中的第二信使。
We have previously shown that a metabolite of NAD+ generated by an enzyme present in sea urchin eggs and mammalian tissues can mobilize intracellular Ca2+ in the eggs. Structural determination established it to be a cyclized ADP-ribose, and the name cyclic ADP-ribose (cADPR) has been proposed. In this study, Ca2+ mobilizations induced by cADPR and inositol trisphosphate (IP3) in sea urchin egg homogenates were monitored with Ca2+ indicators and Ca2+-specific electrodes. Both methods showed that cADPR can release Ca2+ from egg homogenates. Evidence indicated that it did not act as a nonspecific Ca2+-ionophore or as a blocker of the microsomal Ca2+-transport; instead, it was likely to be operating through a specific receptor system. This was supported by its half-maximal effective concentration of 18 nM, which was 7 times lower than that of IP3. The receptor for cADPR appeared to be different from that of IP3 because heparin, an inhibitor of IP3 binding, had no effect on the cADPR action. The Ca2+ releases induced by cADPR and IP3 were not additive and had an inverse relationship, indicating overlapping stores were mobilized. Microinjection of cADPR into intact eggs induced transient intracellular Ca2+ changes and activated the cortical reaction. The in vivo effectiveness of cADPR was directly comparable with IP3 and neither required external Ca2+. In addition, both were effective in activating the eggs to undergo multiple nuclear cycles and DNA synthesis. These results suggest that cADPR could function as a second messenger in sea urchin eggs.