Rapizzi Elena, Pinton Paolo, Szabadkai Gyorgy, Wieckowski Mariusz R, Vandecasteele Gregoire, Baird Geoff, Tuft Richard A, Fogarty Kevin E, Rizzuto Rosario
Department of Experimental and Diagnostic Medicine, Section of General Pathology, Telethon Center for Cell Imaging and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Via Borsari 46, I-44100 Ferrara, Italy.
J Cell Biol. 2002 Nov 25;159(4):613-24. doi: 10.1083/jcb.200205091. Epub 2002 Nov 18.
Although the physiological relevance of mitochondrial Ca2+ homeostasis is widely accepted, no information is yet available on the molecular identity of the proteins involved in this process. Here we analyzed the role of the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane in the transmission of Ca2+ signals between the ER and mitochondria by measuring cytosolic and organelle [Ca2+] with targeted aequorins and Ca2+-sensitive GFPs. In HeLa cells and skeletal myotubes, the transient expression of VDAC enhanced the amplitude of the agonist-dependent increases in mitochondrial matrix Ca2+ concentration by allowing the fast diffusion of Ca2+ from ER release sites to the inner mitochondrial membrane. Indeed, high speed imaging of mitochondrial and cytosolic [Ca2+] changes showed that the delay between the rises occurring in the two compartments is significantly shorter in VDAC-overexpressing cells. As to the functional consequences, VDAC-overexpressing cells are more susceptible to ceramide-induced cell death, thus confirming that mitochondrial Ca2+ uptake plays a key role in the process of apoptosis. These results reveal a novel function for the widely expressed VDAC channel, identifying it as a molecular component of the routes for Ca2+ transport across the mitochondrial membranes.
尽管线粒体钙稳态的生理相关性已被广泛认可，但目前尚无关于参与此过程的蛋白质分子身份的信息。在此，我们通过使用靶向水母发光蛋白和钙敏感绿色荧光蛋白测量细胞质和细胞器中的[Ca2+]，分析了线粒体外膜电压依赖性阴离子通道（VDAC）在ER和线粒体之间钙信号传递中的作用。在HeLa细胞和骨骼肌管中，VDAC的瞬时表达通过允许Ca2+从ER释放位点快速扩散到线粒体内膜，增强了激动剂依赖性线粒体基质钙浓度增加的幅度。事实上，线粒体和细胞质[Ca2+]变化的高速成像显示，在过表达VDAC的细胞中，两个区室中钙升高之间的延迟明显缩短。至于功能后果，过表达VDAC的细胞对神经酰胺诱导的细胞死亡更敏感，从而证实线粒体钙摄取在细胞凋亡过程中起关键作用。这些结果揭示了广泛表达的VDAC通道的新功能，将其确定为钙跨线粒体膜运输途径的分子成分。
