SYNTHESIS AND CHARACTERIZATION OF ANTAGONISTS OF CYCLIC-ADP-RIBOSE-INDUCED CA2+ RELEASE
SYNTHESIS AND CHARACTERIZATION OF ANTAGONISTS OF CYCLIC-ADP-RIBOSE-INDUCED CA2+ RELEASE
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DOI：
10.1016/0167-4889(93)90199-y
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发表时间：
1993-09-13
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：
WALSETH, TF;LEE, HC
环adp核糖（cADPR）是NAD+的天然代谢物，在动员细胞内Ca2+方面与肌醇三磷酸一样有效。合成了一系列在腺嘌呤基团8位修饰的类似物，以研究代谢产物的结构与其Ca2+动员活性之间的关系。与腺嘌呤环8位的氨基取代产生拮抗剂。8-氨基-cADPR的h -1核磁共振谱显示了cADPR的特征，证实了8-质子的替换。8-氨基-cADPR （150 nM）本身不诱导海胆蛋匀浆中Ca2+的释放，但完全阻断了cADPR （135 nM）的释放。这种效应是可逆的，因为高浓度的cADPR可以克服这种抑制作用。在cadpr诱导的Ca2+释放期间，将8-氨基- cadpr添加到鸡蛋匀浆中，立即阻断了Ca2+释放，证明了拮抗剂的有效性。对[P-32]cADPR与其微粒体结合位点结合的测量表明，8-氨基-cADPR在竞争结合位点方面与cADPR本身一样有效。除了阻断cADPR释放Ca2+外，8-氨基-cADPR还抑制cADPR增强二价阳离子或咖啡因诱导的Ca2+释放。另外两个8-取代类似物也被合成。8-Br-和8-叠氮- cadpr也是拮抗剂，但效力低于8-氨基- cadpr。这些结果表明，腺嘌呤基团8位的改变不会抑制cADPR与其受体的结合，但确实消除了代谢产物激活Ca2+释放机制的能力。
Cyclic ADP-ribose (cADPR) is a naturally-occurring metabolite of NAD+ that is as effective as inositol trisphosphate in mobilizing intracellular Ca2+. A series of analogs modified at the 8-position of the adenine group were synthesized for the investigation of the relationship between the structure of the metabolite and its Ca2+-mobilizing activity. Substitution with an amino group at the 8-position of the adenine ring produced an antagonist. The H-1-NMR spectrum of 8-amino-cADPR showed characteristics of that of cADPR and confirmed the replacement of the 8-proton. By itself, 8-amino-cADPR (150 nM) did not induce Ca2+ release from sea-urchin-egg homogenates but totally blocked cADPR (135 nM) from doing so. The effect was reversible, since high concentrations of cADPR could overcome the inhibition. Addition of 8-amino-cADPR to egg homogenates during the cADPR-induced Ca2+ release blocked the release immediately, demonstrating the effectiveness of the antagonist. Measurements of [P-32]cADPR binding to its microsomal binding site showed that 8-amino-cADPR was as effective as cADPR itself in competing for the binding site. In addition to blocking cADPR from releasing Ca2+, 8-amino-cADPR also inhibited cADPR from potentiating Ca2+-release induced by either divalent cations or by caffeine. Two other 8-substituted analogs were also synthesized. Both 8-Br- and 8-azido-cADPR were also antagonists, although with less potency than 8-amino-cADPR. These results show that alterations at the 8-position of the adenine group do not inhibit cADPR from binding to its receptor but do eliminate the ability of the metabolite to activate the Ca2+-release mechanism.