Mitochondrial Calcium Cycling in Neuronal Function

描述（由申请人提供）：线粒体除了具有生物能量功能外，还是神经元中钙信号的关键调节因子。线粒体在兴奋期间有效缓冲Ca2+内流，并限制细胞质Ca2+浓度（[Ca2+]i）增加的幅度。快速的Ca2+摄取随后是较慢的钙从线粒体释放，完成刺激诱导的线粒体Ca2+循环。通过塑造[Ca2+]i反应，线粒体可以调节许多Ca2+依赖的神经元功能。与此同时，线粒体Ca2+运输的损伤是导致中风和许多神经退行性疾病中神经元损伤的关键因素。尽管取得了重大进展，但关于神经元中线粒体Ca2+循环的时空组织、功能和调节，特别是关于从生理到病理生理转变的调节机制，仍存在许多问题。我们的总体假设是线粒体Ca2+循环控制着多种神经元功能，生理和病理结果之间的决定受到线粒体蛋白可逆磷酸化的影响。我们将首先关注两个生理过程，递质释放（Aim 1）和转录激活（Aim 2），通过研究时空组织和线粒体Ca2+运输在两个形态和功能不同的细胞室，突触前扣和细胞体中的作用。然后，我们将研究蛋白激酶A和蛋白磷酸酶2A如何调节线粒体Ca2+信号和Ca2+依赖过程，如神经传递、转录激活和兴奋毒性（Aim 3）。这两种酶都针对线粒体外膜（OMM），但对细胞存活表现出相反的作用，并且预计对线粒体依赖功能的影响不同。提出的研究将促进我们对线粒体Ca2+转运体如何与神经元中的蛋白激酶和磷酸酶相互作用以触发特定生理或病理反应的理解。

DESCRIPTION (provided by applicant): In addition to their bioenergetic function, mitochondria are critical regulators of Ca signaling in neurons. Mitochondria efficiently buffer Ca2+ influx during excitation and limit the amplitude of the cytosolic Ca2+ concentration ([Ca2+]i) increase. Rapid Ca2+ uptake is followed by a slower Ca release from mitochondria, completing stimulus-induced mitochondrial Ca2+ cycle. By shaping [Ca2+]i response, mitochondria can modulate numerous Ca2+-dependent neuronal functions. At the same time, impairment of mitochondrial Ca2+ transport is the key factor leading to neuronal damage in stroke and in a number of neurodegenerative disorders. Despite significant progress, many questions remain about the spatiotemporal organization, function and modulation of mitochondrial Ca2+ cycling in neurons and, specifically, about the mechanisms regulating the transition from physiology to pathophysiology. Our overall hypothesis is that mitochondrial Ca2+ cycling controls diverse neuronal functions and that the decision between physiological and pathological outcomes is influenced by reversible phosphorylation of mitochondrial proteins. We will initially focus on two physiological processes, transmitter release (Aim 1) and activation of transcription (Aim 2), by studying spatiotemporal organization and the role of mitochondrial Ca2+ transport in two morphologically and functionally distinct cellular compartments, presynaptic boutons and the cell soma, respectively. We will then investigate how protein kinase A and protein phosphatase 2A modulate mitochondrial Ca2+ signaling and Ca2+-dependent processes, such as neurotransmission, transcription activation and excitotoxicity (Aim 3). Both enzymes are targeted to the outer mitochondrial membrane (OMM), but exhibit opposite effects on cell survival, and are predicted to differentially influence mitochondria-dependent functions. The proposed studies will advance our understanding of how mitochondrial Ca2+ transporters interplay with protein kinases and phosphatases in neurons to trigger a specific physiological or pathological response.