Clementi E, Riccio M, Sciorati C, Nisticò G, Meldolesi J
Department of Pharmacology, Faculty of Pharmacy, University of Reggio Calabria, 88021 Catanzaro, Italy.
J Biol Chem. 1996 Jul 26;271(30):17739-45. doi: 10.1074/jbc.271.30.17739.
Of two neurosecretory PC12 cell clones that respond to NO donors and 8-bromo-cGMP with similar increases in cADP-ribose and that possess molecularly similar Ca2+ stores, only one (clone 16A) expresses the type 2 ryanodine receptor, whereas the other (clone 27) is devoid of ryanodine receptors. In PC12-16A cells, activation of the NO/cGMP pathway induced slow [Ca2+]i responses, sustained by release from Ca2+ stores. In contrast, PC12-27 cells were insensitive to NO donors. Likewise, in PC12-16A cells preincubated with NO donors, Ca2+ stores were partially depleted, as revealed by a test with thapsigargin, whereas those in clone 27 were unchanged. The NO-induced Ca2+ release was increased synergistically by caffeine, and the corresponding store depletion was magnified by ryanodine. The specificity for the NO/cGMP pathway was confirmed by the effects of two blockers of cGMP-dependent protein kinase I, while the role of cADP-ribose was demonstrated by the effects of its antagonist, 8-amino-cADP-ribose, administered to permeabilized cells. These results demonstrate in neurosecretory cells a ryanodine receptor activation pathway similar to that known in sea urchin oocytes. The signaling events described here could be of great physiological importance, especially in the nervous system.
在两个对一氧化氮供体和8-溴环鸟苷酸有反应、cADP-核糖含量有相似增加且拥有分子结构相似的钙离子储存库的神经分泌型PC12细胞克隆中，只有一个（克隆16A）表达2型兰尼碱受体，而另一个（克隆27）则没有兰尼碱受体。在PC12-16A细胞中，一氧化氮/环鸟苷酸途径的激活诱导了缓慢的细胞内钙离子浓度（[Ca2+]i）反应，该反应由钙离子储存库的释放维持。相比之下，PC12-27细胞对一氧化氮供体不敏感。同样，在用一氧化氮供体预孵育的PC12-16A细胞中，毒胡萝卜素试验显示钙离子储存库部分耗尽，而克隆27中的储存库则没有变化。咖啡因协同增强了一氧化氮诱导的钙离子释放，而兰尼碱则放大了相应的储存库耗尽。环鸟苷酸依赖性蛋白激酶I的两种抑制剂的作用证实了一氧化氮/环鸟苷酸途径的特异性，而其拮抗剂8-氨基-cADP-核糖对透化细胞的作用则证明了cADP-核糖的作用。这些结果表明，在神经分泌细胞中存在一种类似于海胆卵母细胞中已知的兰尼碱受体激活途径。这里描述的信号事件可能具有重要的生理意义，尤其是在神经系统中。
