衰老过程中tRNA结合蛋白调控周围神经退行性变化的机制研究

The formation of stress granules (SG) is an important cellular mechanism to respond to environmental and physiological stimuli. Aging perturbs SG assembly-disassembly dynamics and thereby limits the stress response in the cell. A number of genetic mutations have been identified to disrupt the SG dynamics, contributing to several neurodegenerative diseases in the peripheral nervous system. Therefore, it is particularly important to understand the regulatory mechanism of SG dynamics in aging and degeneration of peripheral nervous system. Charcot-Marie-Tooth (CMT) diseases are the most common hereditary peripheral neuropathies, for which there are no effective therapies. A subtype of the diseases—CMT2D—is caused by dominant mutations in GARS gene, encoding glycyl-tRNA synthetase (GlyRS). The canonical function of this enzyme is to catalyze the ligation of glycine to the 3’-end of its cognate tRNA as the first step of protein synthesis. Our preliminary findings indicate that GlyRS can interact with several SG-associated proteins; CMT2D-associated mutations cause abnormal GlyRS-SG interaction, contributing to the degeneration of peripheral nerves. In this proposal, we aim to identify the role of GlyRS in regulating SG dynamics and uncover the mechanism underlying CMT2D pathogenesis and age-related neurodegeneration in peripheral nervous system.

形成应激颗粒（Stress granule, SG）是一种重要的细胞应激机制。细胞衰老会影响SG组装-解聚的动态变化，使细胞应对内部或外界刺激的能力变差；而遗传突变导致的SG动态失调已经被证实是引发周围神经退行性变化的一个重要机制。因此，针对SG动态调控机制的研究对于理解周围神经衰老和退行性变化具有特别重要的意义。腓骨肌萎缩症（CMT）是周围神经系统最常见的遗传性疾病之一，其中CMT2D亚型是由编码甘氨酰-tRNA合成酶（GlyRS）的GARS基因上的遗传突变所导致的。本项目的前期研究结果提示：GlyRS蛋白可以与多种SG核心蛋白互作；CMT2D致病突变导致GlyRS与SG互作发生异常，从而引发周围神经提前发生退行性变化。在本项研究中，我们将揭示tRNA结合蛋白GlyRS是调控SG动态变化的重要因子，其在CMT2D发病过程和周围神经衰老向退行性变化的演变过程中都扮演了重要角色。

已知遗传因子与环境应激因子之间的互作在衰老与神经退行性疾病发病过程中扮演了非常重要的角色。本项目的研究发现，在环境应激因子作用下，腓骨肌萎缩症（CMT）致病蛋白GlyRS可以进入应激颗粒（SG），并通过与SG核心蛋白之间的异常互作导致周围神经提前发生退行性病变。我们通过小鼠遗传学、神经病理、活细胞荧光成像、近端标记、蛋白质组学等手段发现：（1）当细胞面临不良环境刺激时，GlyRS致病蛋白会从细胞质中转移到SG中；（2）GlyRS突变蛋白可以与SG中的G3BP蛋白发生异常互作，从而破坏以G3BP为核心的SG蛋白网络，导致运动神经应激易损性增加；（3）通过破坏GlyRS突变蛋白与G3BP之间的异常互作可以消除SG的功能异常，延缓CMT2D小鼠模型中周围神经的退行性病变。本项研究表明GlyRS致病蛋白可以通过影响SG的功能参与CMT发病过程，阐明了SG在周围神经衰老和退行性变化中的重要作用。