Multi-Granulin Domain Peptides Bind to Pro-Cathepsin D and Stimulate Its Enzymatic Activity More Effectively Than Progranulin in Vitro
Multi-Granulin Domain Peptides Bind to Pro-Cathepsin D and Stimulate Its Enzymatic Activity More Effectively Than Progranulin in Vitro
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DOI：
10.1021/acs.biochem.9b00275
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发表时间：
2019-06-11
期刊：
影响因子：
2.9
通讯作者：
Kao, Aimee W.
中科院分区：
文献类型：
--
作者：
Butler, Victoria J.;Cortopassi, Wilian A.;Kao, Aimee W.
颗粒体蛋白前体 (PGRN) 是一种进化上保守的糖蛋白，与多种疾病状态相关，包括神经退行性疾病、癌症和自身免疫性疾病。该蛋白最近被认为参与溶酶体功能的调节，由此 PGRN 可能与天冬氨酰蛋白酶组织蛋白酶 D（proCTSD，无活性前体；matCTSD，成熟的酶活性形式）结合并促进其成熟和活性。由于全长 PGRN 蛋白可以裂解成更小的肽（称为颗粒蛋白），因此我们评估了这些颗粒蛋白肽在体外与 proCTSD 结合和刺激 matCTSD 酶活性方面的功能。在这里，我们报告全长 PGRN 和多颗粒蛋白结构域肽以低至亚微摩尔的结合亲和力与 proCTSD 结合。这种结合促进了 proCTSD 的不稳定，多颗粒蛋白结构域肽的不稳定程度大于全长 PGRN。这种不稳定与酸性 pH 下 matCTSD 活性增强相关。在以前的研究中，多颗粒蛋白结构域肽的存在和功能通常被忽视。这项工作首次对它们对 proCTSD 的结合和活性进行了体外定量。我们的研究强调了多颗粒蛋白结构域肽在调节 proCTSD 成熟和酶活性中的重要性，并表明对 PGRN 加工的关注对于未来了解导致 PGRN 功能丧失突变的神经退行性疾病状态的分子机制至关重要。
Progranulin (PGRN) is an evolutionarily conserved glycoprotein associated with several disease states, including neurodegeneration, cancer, and autoimmune disorders. This protein has recently been implicated in the regulation of lysosome function, whereby PGRN may bind to and promote the maturation and activity of the aspartyl protease cathepsin D (proCTSD, inactive precursor; matCTSD, mature, enzymatically active form). As the full-length PGRN protein can be cleaved into smaller peptides, called granulins, we assessed the function of these granulin peptides in binding to proCTSD and stimulating matCTSD enzyme activity in vitro. Here, we report that full-length PGRN and multi-granulin domain peptides bound to proCTSD with low to submicromolar binding affinities. This binding promoted proCTSD destabilization, the magnitude of which was greater for multi-granulin domain peptides than for full-length PGRN. Such destabilization correlated with enhanced matCTSD activity at acidic pH. The presence and function of multi-granulin domain peptides have typically been overlooked in previous studies. This work provides the first in vitro quantification of their binding and activity on proCTSD. Our study highlights the significance of multi-granulin domain peptides in the regulation of proCTSD maturation and enzymatic activity and suggests that attention to PGRN processing will be essential for the future understanding of the molecular mechanisms leading to neurodegenerative disease states with loss-of-function mutations in PGRN.