Alhadidy Mohammed M, Mueller Rebecca L, Lamp Jared, Kanaan Nicholas M
Department of Translational Neuroscience, College of Human Medicine, Michigan State University, Grand Rapids, MI, U.S.A.
Neuroscience Program, Michigan State University, East Lansing, MI, U.S.A.
Biochem J. 2025 Jun 17;482(12):877-99. doi: 10.1042/BCJ20253079.
Tau is subject to a broad range of post-translational modifications (PTMs) that regulate its biological activity in health and disease, including microtubule (MT) dynamics, aggregation, and adoption of pathogenic conformations. The most studied PTMs of tau are phosphorylation and acetylation; however, the salience of other PTMs is not fully explored. Tissue transglutaminase (TG) is an enzyme whose activity is elevated in Alzheimer's disease (AD). TG action on tau may lead to intramolecular and intermolecular cross-linking along with the incorporation of cationic polyamines (e.g., spermidine [SPD]) onto glutamine residues (Q). Even though SPD levels are significantly elevated in AD, the effects of SPD polyamination on tau biology have yet to be examined. In this work, we describe a method to produce recombinant SPD-modified tau where SPD modifications are mainly localized to Q residues within the N-terminus. MT binding and polymerization assays showed that SPD modification does not significantly alter tau's binding to MTs but increases MT polymerization kinetics. In addition, biochemical and biophysical assays showed that SPD polyamination of tau markedly reduces tau polymerization into filamentous and β-sheet-containing aggregates. On the other hand, SPD modification promotes the formation of pathogenic conformations (e.g., oligomerization and misfolding) by tau with or without inducing tau polymerization. Taken together, these data suggest that SPD polyamination of tau enhances its ability to polymerize MTs and favors the adoption of pathogenic tau conformations but not filamentous aggregates in vitro.
Tau蛋白会经历广泛的翻译后修饰（PTM），这些修饰在健康和疾病状态下调节其生物学活性，包括微管（MT）动力学、聚集以及致病构象的形成。对tau蛋白研究最多的PTM是磷酸化和乙酰化；然而，其他PTM的重要性尚未得到充分探索。组织转谷氨酰胺酶（TG）是一种在阿尔茨海默病（AD）中活性升高的酶。TG对tau蛋白的作用可能导致分子内和分子间交联，以及阳离子多胺（如亚精胺[SPD]）掺入谷氨酰胺残基（Q）。尽管AD中亚精胺水平显著升高，但亚精胺多胺化对tau蛋白生物学的影响尚未得到研究。在这项工作中，我们描述了一种生产重组SPD修饰tau蛋白的方法，其中SPD修饰主要定位于N端的Q残基。微管结合和聚合试验表明，SPD修饰不会显著改变tau蛋白与微管的结合，但会增加微管聚合动力学。此外，生化和生物物理试验表明，tau蛋白的SPD多胺化显著降低了tau蛋白聚合成丝状和含β折叠的聚集体。另一方面，SPD修饰促进了有或没有诱导tau蛋白聚合的情况下tau蛋白致病构象（如寡聚化和错误折叠）的形成。综上所述，这些数据表明，tau蛋白的SPD多胺化增强了其聚合微管的能力，有利于致病tau蛋白构象的形成，但在体外不利于丝状聚集体的形成。
