Mitochondrial Calcium Cycling in Neuronal Function

描述(申请人提供)：除了它们的生物能量功能，线粒体也是神经元中钙信号的关键调节器。线粒体有效地缓冲了兴奋过程中的钙内流，限制了胞浆内钙浓度([Ca~(2+)]i)升高的幅度。线粒体快速摄取Ca~(2+)后缓慢释放Ca~(2+)，完成刺激诱导的线粒体Ca~(2+)循环。线粒体通过影响[Ca~(2+)]_i的反应，调节许多钙依赖的神经元功能。同时，线粒体钙转运障碍是导致卒中和一些神经退行性疾病神经元损伤的关键因素。尽管取得了很大的进展，但关于神经元线粒体钙循环的时空组织、功能和调控，特别是调控从生理学向病理生理学转变的机制，仍然存在许多问题。我们的总体假设是，线粒体钙循环控制着不同的神经元功能，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。我们首先将重点放在两个生理过程，即递质释放(目标1)和转录激活(目标2)，通过分别研究时空组织和线粒体钙转运在两个形态和功能不同的细胞亚室，突触前突触和细胞体，分别。然后，我们将研究蛋白激酶A和蛋白磷酸酶2A如何调节线粒体钙信号和钙依赖过程，如神经传递、转录激活和兴奋毒性(目标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，并被预测为不同地影响线粒体依赖的功能。这些研究将促进我们对线粒体钙离子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的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.