Life cycle of AMPA receptors under acute metabolic stress

AMPA型谷氨酸受体(AMPAR)介导了哺乳动物脑内大部分快速兴奋性神经传递，提供了钠离子进入突触后脊椎的主要途径。钠离子进入脊髓的量和突触后细胞的兴奋性在很大程度上取决于突触后膜上AMPAR的量以及它们的生物物理性质。AMPAR的贩运和门控是由它们的分子组成决定的。AMPAR是由成孔和谷氨酸结合亚基GluA1-4和多种辅助亚基组成的异构体，导致了广泛的门控动力学和亚细胞加工。AMPAR在代谢衰竭的病理生理学中起着重要作用。在新陈代谢应激后的晚期，它们在亚细胞转运行为中表现出亚单位依赖性的改变，导致突触后膜上从含GluA2的钙不通透的AMPAR转变为缺乏钙通透性的AMPAR。这种亚单位转换导致EPSC幅度增加，钙和锌流入突触后神经元，最终导致兴奋性毒性和延迟性细胞死亡。然而，AMPAR在代谢应激后的第一个小时内的作用几乎没有被研究过。在这里，我们打算研究AMPAR的突触后信号对细胞代谢抑制的反应。我们将特别关注AMPAR辅助亚基的调控机制。我们将综合运用生化、细胞和分子生物学及电生理学等多学科方法，以期揭示突触后AMPAR复合体重组的机制以及代谢应激早期对突触后神经元的功能影响。

AMPA-type glutamate receptors (AMPARs) mediate most of the fast excitatory neurotransmission in the mammalian brain providing a major route of sodium influx into the postsynaptic spine. The amount of sodium entering the spine and the excitability of the postsynaptic cell largely depend on the amount of AMPARs in the postsynaptic membrane as well as their biophysical properties. Trafficking and gating of AMPARs is determined by their molecular composition. AMPARs consist as heterotetramers of the pore-forming and glutamate binding subunits GluA1-4 and a variety of auxiliary subunits leading to a wide range of gating kinetics and subcellular processing.AMPARs play an important part in the pathophysiology of metabolic failure. In the late phase following metabolic stress they show subunit-dependent alterations in subcellular trafficking behavior resulting in a switch from GluA2-containing Ca2+-impermeable to GluA2-lacking Ca2+-permeable AMPARs in the postsynaptic membrane. This subunit switch leads to an increase in EPSC amplitudes and to an influx of calcium and zinc into the postsynaptic neuron, finally resulting in excitotoxicity and delayed cell death. However, the role of AMPARs in the first hour following metabolic stress has hardly been investigated.Here, we intend to investigate the postsynaptic signaling of AMPARs in response to inhibition of cellular metabolism. We will particularly focus on the regulatory mechanisms of AMPAR auxiliary subunits. We will apply a multidisciplinary approach combining biochemical, cell and molecular biological and electrophysiological techniques in order to unravel the mechanisms underlying re-organization of postsynaptic AMPAR complexes and the functional consequences for the postsynaptic neuron in the early phase of metabolic stress.