Age- and stress-associated C. elegans granulins impair lysosomal function and induce a compensatory HLH-30/TFEB transcriptional response
Age- and stress-associated C. elegans granulins impair lysosomal function and induce a compensatory HLH-30/TFEB transcriptional response
复制标题
DOI：
10.1371/journal.pgen.1008295
复制
发表时间：
2019-08-01
期刊：
影响因子：
4.5
通讯作者：
Kao, Aimee W.
中科院分区：
文献类型：
--
作者：
Butler, Victoria J.;Gao, Fuying;Kao, Aimee W.
蛋白质稳态的进行性失效是衰老的标志，也是神经退行性疾病的共同特征。作为执行自噬最后阶段的酶，溶酶体蛋白酶是随年龄维持蛋白质稳态的关键因素。我们之前报道了神经退行性疾病蛋白前颗粒蛋白的裂解产物颗粒蛋白肽的表达，增强了秀丽隐杆线虫（C. elegans）中TAR DNA结合蛋白43 （TDP-43）的积累和毒性。在这项研究中，我们表明秀丽隐杆线虫颗粒是在年龄和压力依赖的方式产生的。颗粒蛋白定位于溶酶体腔室，在那里它们损害溶酶体蛋白酶的表达和活性。因此，蛋白质稳态被破坏，促进溶酶体转录因子HLH-30/TFEB的核易位，并促使细胞激活代偿性转录程序。在我们的实验中，三种秀丽隐杆线虫颗粒蛋白肽表现出不同但重叠的功能效应，这可能是由于氨基酸组成导致不同的静电和疏水性谱。我们的研究结果支持一个模型，即颗粒蛋白的产生调节了正常的蛋白酶活性生理调节和溶酶体功能损伤之间的关键转变，溶酶体功能损伤可能随着年龄和疾病而发生。蛋白质稳态维持的逐渐下降显然有助于神经退行性疾病的发展，但这种下降的分子基础尚不清楚。在这里，我们利用在模式生物秀丽隐杆线虫中可用的分子遗传学技术来研究由前颗粒蛋白基因突变引起的神经退行性疾病的机制。我们发现，年龄，基因突变和生理应激导致溶酶体颗粒蛋白（前颗粒蛋白的裂解产物）的积累，从而破坏细胞蛋白质稳态。颗粒蛋白的表达会损害动物的适应性、抗应激性和神经元功能，并刺激溶酶体应激反应，试图上调溶酶体基因并恢复正常功能。我们的发现特别重要，因为它们为神经退行性疾病的治疗提出了一个新的、合理的靶点——抑制颗粒蛋白前裂解成颗粒蛋白。
The progressive failure of protein homeostasis is a hallmark of aging and a common feature in neurodegenerative disease. As the enzymes executing the final stages of autophagy, lysosomal proteases are key contributors to the maintenance of protein homeostasis with age. We previously reported that expression of granulin peptides, the cleavage products of the neurodegenerative disease protein progranulin, enhance the accumulation and toxicity of TAR DNA binding protein 43 (TDP-43) in Caenorhabditis elegans (C. elegans). In this study we show that C. elegans granulins are produced in an age- and stress-dependent manner. Granulins localize to the endolysosomal compartment where they impair lysosomal protease expression and activity. Consequently, protein homeostasis is disrupted, promoting the nuclear translocation of the lysosomal transcription factor HLH-30/TFEB, and prompting cells to activate a compensatory transcriptional program. The three C. elegans granulin peptides exhibited distinct but overlapping functional effects in our assays, which may be due to amino acid composition that results in distinct electrostatic and hydrophobicity profiles. Our results support a model in which granulin production modulates a critical transition between the normal, physiological regulation of protease activity and the impairment of lysosomal function that can occur with age and disease.Author summary Progressive decline in maintenance of protein homeostasis clearly contributes to the development of neurodegenerative disorders, yet the molecular basis of this decline is poorly understood. Here, we take advantage of molecular genetic techniques available in the model organism C. elegans to investigate the mechanism underlying neurodegenerative disease due to mutations in the progranulin gene. We find that age, gene mutation and physiological stress lead to the accumulation of lysosomal granulins (the cleavage products of the progranulin protein) thereby disrupting cellular protein homeostasis. Granulin expression impairs animal fitness, resistance to stress and neuronal function, and stimulates a lysosomal stress response in an attempt to up-regulate lysosomal genes and restore normal function. Our findings are particularly important because they suggest a new, rational target-inhibition of progranulin cleavage into granulins-for neurodegenerative disease therapy.