Baron Kyle T, Wang Guang Jian, Padua Rodolfo A, Campbell Colin, Thayer Stanley A
Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455-0217, USA.
Brain Res. 2003 Dec 12;993(1-2):124-32. doi: 10.1016/j.brainres.2003.09.022.
Activation of NMDA receptors produces large increases in cytosolic Ca(2+) that are taken up into mitochondria. We used recombinant aequorin targeted to mitochondria to report changes in matrix Ca(2+) in rat hippocampal neurons in culture. Upon binding Ca(2+), aequorin emits a photon in a one-shot reaction that consumes the indicator. Here we show that stimulation with NMDA produced a mitochondrial Ca(2+) response that rapidly inactivated. However, following a 30-min recovery period the response was restored, suggesting the presence of a pool of indicator that was not exposed to high Ca(2+) during the initial stimulus. We speculate that aequorin distant from the Ca(2+) source was protected from microdomains of high Ca(2+) near the plasmalemma and that this aequorin moved, either by movement of individual mitochondria or via the mitochondrial tubular network, to replenish consumed indicator during the recovery time. A large Ca(2+) increase in a subset of mitochondria could produce local changes in energy metabolism, regional Ca(2+) buffering, and foci that initiate neurotoxic processes.
NMDA 受体的激活会使细胞质中的 Ca(2+)大幅增加，这些 Ca(2+)会被摄取到线粒体中。我们使用靶向线粒体的重组水母发光蛋白来报告培养的大鼠海马神经元中基质 Ca(2+)的变化。结合 Ca(2+)后，水母发光蛋白在一次性反应中发射光子，该反应会消耗指示剂。在此我们表明，用 NMDA 刺激会产生线粒体 Ca(2+)反应，该反应会迅速失活。然而，经过 30 分钟的恢复期后，反应得以恢复，这表明存在一组指示剂，在初始刺激期间未暴露于高 Ca(2+)环境。我们推测，远离 Ca(2+)源的水母发光蛋白受到质膜附近高 Ca(2+)微区的保护，并且这种水母发光蛋白通过单个线粒体的移动或通过线粒体管状网络移动，在恢复期间补充消耗的指示剂。线粒体亚群中 Ca(2+)的大幅增加可能会导致能量代谢、区域 Ca(2+)缓冲以及引发神经毒性过程的病灶发生局部变化。
