Scorziello Antonella, Savoia Claudia, Sisalli Maria Josè, Adornetto Annagrazia, Secondo Agnese, Boscia Francesca, Esposito Alba, Polishchuk Elena V, Polishchuk Roman S, Molinaro Pasquale, Carlucci Annalisa, Lignitto Luca, Di Renzo Gianfranco, Feliciello Antonio, Annunziato Lucio
Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples-National Institute of Neuroscience, Italy.
J Cell Sci. 2013 Dec 15;126(Pt 24):5566-77. doi: 10.1242/jcs.129668. Epub 2013 Oct 7.
The mitochondrial influx and efflux of Ca(2+) play a relevant role in cytosolic and mitochondrial Ca(2+) homeostasis, and contribute to the regulation of mitochondrial functions in neurons. The mitochondrial Na(+)/Ca(2+) exchanger, which was first postulated in 1974, has been primarily investigated only from a functional point of view, and its identity and localization in the mitochondria have been a matter of debate over the past three decades. Recently, a Li(+)-dependent Na(+)/Ca(2+) exchanger extruding Ca(2+) from the matrix has been found in the inner mitochondrial membrane of neuronal cells. However, evidence has been provided that the outer membrane is impermeable to Ca(2+) efflux into the cytoplasm. In this study, we demonstrate for the first time that the nuclear-encoded NCX3 isoform (1) is located on the outer mitochondrial membrane (OMM) of neurons; (2) colocalizes and immunoprecipitates with AKAP121 (also known as AKAP1), a member of the protein kinase A anchoring proteins (AKAPs) present on the outer membrane; (3) extrudes Ca(2+) from mitochondria through AKAP121 interaction in a PKA-mediated manner, both under normoxia and hypoxia; and (4) improves cell survival when it works in the Ca(2+) efflux mode at the level of the OMM. Collectively, these results suggest that, in neurons, NCX3 regulates mitochondrial Ca(2+) handling from the OMM through an AKAP121-anchored signaling complex, thus promoting cell survival during hypoxia.
线粒体Ca(2+)的流入和流出在细胞质和线粒体Ca(2+)稳态中发挥着重要作用，并有助于调节神经元中的线粒体功能。线粒体Na(+)/Ca(2+)交换体于1974年首次被提出，过去主要仅从功能角度进行研究，其在 mitochondria 中的身份和定位在过去三十年一直存在争议。最近，在神经元细胞的线粒体内膜中发现了一种依赖Li(+)的从基质中挤出Ca(2+)的Na(+)/Ca(2+)交换体。然而，已有证据表明外膜对Ca(2+)流入细胞质是不可渗透的。在本研究中，我们首次证明核编码的NCX3亚型(1)位于神经元的线粒体外膜(OMM)上；(2)与存在于外膜上的蛋白激酶A锚定蛋白(AKAPs)成员AKAP121(也称为AKAP1)共定位并免疫沉淀；(3)在常氧和低氧条件下，通过AKAP121相互作用以PKA介导的方式从线粒体中挤出Ca(2+)；(4)当它在OMM水平以Ca(2+)流出模式起作用时可提高细胞存活率。总的来说，这些结果表明，在神经元中，NCX3通过AKAP121锚定的信号复合物从OMM调节线粒体Ca(2+)的处理，从而在缺氧期间促进细胞存活。
