Wang Guang Jian, Jackson Joshua G, Thayer Stanley A
Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
J Neurochem. 2003 Oct;87(1):85-94. doi: 10.1046/j.1471-4159.2003.01970.x.
The specificity of Ca2+ signals is conferred in part by limiting changes in cytosolic Ca2+ to subcellular domains. Mitochondria play a major role in regulating Ca2+ in neurons and may participate in its spatial localization. We examined the effects of changes in the distribution of mitochondria on NMDA-induced Ca2+ increases. Hippocampal cultures were treated with the microtubule-destabilizing agent vinblastine, which caused the mitochondria to aggregate and migrate towards one side of the neuron. This treatment did not appear to decrease the energy status of mitochondria, as indicated by a normal membrane potential and pH gradient across the inner membrane. Moreover, electron microscopy showed that vinblastine treatment altered the distribution but not the ultrastructure of mitochondria. NMDA (200 micro m, 1 min) evoked a greater increase in cytosolic Ca2+ in vinblastine-treated cells than in untreated cells. This increase did not result from impaired Ca2+ efflux, enhanced Ca2+ influx, opening of the mitochondrial permeability transition pore or altered function of endoplasmic reticulum Ca2+ stores. Ca2+ uptake into mitochondria was reduced by 53% in vinblastine-treated cells, as reported by mitochondrially targeted aequorin. Thus, the distribution of mitochondria maintained by microtubules is critical for buffering Ca2+ influx. A subset of mitochondria close to a Ca2+ source may preferentially regulate Ca2+ microdomains, set the threshold for Ca2+-induced toxicity and participate in local ATP production.
Ca2+信号的特异性部分是通过将胞质Ca2+的变化限制在亚细胞区域来实现的。线粒体在调节神经元中的Ca2+方面起主要作用，并可能参与其空间定位。我们研究了线粒体分布变化对NMDA诱导的Ca2+增加的影响。用微管破坏剂长春花碱处理海马培养物，这导致线粒体聚集并向神经元的一侧迁移。如跨内膜的正常膜电位和pH梯度所示，这种处理似乎并未降低线粒体的能量状态。此外，电子显微镜显示长春花碱处理改变了线粒体的分布，但未改变其超微结构。与未处理的细胞相比，NMDA（200微摩尔，1分钟）在长春花碱处理的细胞中引起更大的胞质Ca2+增加。这种增加不是由于Ca2+外流受损、Ca2+内流增强、线粒体通透性转换孔开放或内质网Ca2+储存功能改变所致。如线粒体靶向水母发光蛋白所报告的，长春花碱处理的细胞中线粒体对Ca2+的摄取减少了53%。因此，由微管维持的线粒体分布对于缓冲Ca2+内流至关重要。靠近Ca2+源的一部分线粒体可能优先调节Ca2+微区，设定Ca2+诱导毒性的阈值并参与局部ATP的产生。
