Molecular mechanism and function of neuronal ER-phagy

在神经元网络中，电信号和化学神经递质允许从一个神经元的突触前隔室到另一个神经元的突触后隔室的快速通信。为了支持神经元和突触的完整性，神经元进化出了维持适当的蛋白质平衡和去除受损蛋白质的策略。自噬是细胞质部分被膜吞噬并被送去降解的过程。我们和其他人的工作不仅证明了自噬对神经元功能的重要作用，而且揭示了突触囊泡（SV）循环机制与自噬系统之间的新的分子联系。然而，哪些神经元底物是通过自噬-溶酶体途径转化的，这一途径是如何被控制的，以及它是如何与神经元活动联系在一起的，目前还不完全清楚。为了解决这些关键问题，我们产生了有条件地缺乏必要的自噬蛋白ATG5的敲除小鼠。我们发现，在生理条件下，神经元自噬的丧失导致轴突中管状内质网（ER）的选择性积累，导致内质网储存的钙通过ryanodine受体释放增加，从而导致兴奋性神经传递增加。因此，我们假设神经元自噬控制轴突内质网钙储存，从而调节健康神经元和大脑中的神经传递。该项目的总体目标是了解中枢神经系统神经元（WP1）中哪些特异性接头控制ER吞噬（即通过自噬降解ER）过程，神经元ER吞噬如何受到神经元活动或其他刺激（WP2）的调节，以及ER吞噬在突触后室和突触前室（WP3）中的生理作用。

Within neuronal networks, electrical signals and chemical neurotransmitters allow for rapid communication from the presynaptic compartment of one neuron to a postsynaptic compartment of another neuron. To support neuronal and synaptic integrity, neurons have evolved strategies for maintaining proper proteostasis and removing damaged proteins. Autophagy is a process in which parts of the cytoplasm are engulfed by membrane and sent for degradation. Work from us and others have not only demonstrated that autophagy is important for neuronal function but also revealed novel molecular links between the machineries for synaptic vesicle (SV) recycling and the autophagy system. However, which neuronal substrates are turned over via the autophagy-lysosomal pathway, how this pathway is controlled and how it is linked to neuronal activity is incompletely understood. To address these crucial questions, we generated knockout mice conditionally lacking the essential autophagy protein ATG5. We discovered that loss of neuronal autophagy causes the selective accumulation of tubular Endoplasmic Reticulum (ER) in axons under physiological conditions, resulting in increased excitatory neurotransmission as a consequence of elevated calcium release from ER stores via ryanodine receptors. We therefore hypothesize that neuronal autophagy controls axonal ER calcium stores to regulate neurotransmission in healthy neurons and in the brain. The overall objective of the proposed project is to understand which specific adaptors control the ER-phagy (i.e. ER degradation by autophagy) process in central nervous system neurons (WP1), how neuronal ER-phagy is regulated by neuronal activity or other stimuli (WP2), and what the physiological roles of ER-phagy are in the post- versus the presynaptic compartment (WP3).