Akbari Vali, Mohammadi Soheila, Mehrabi Masomeh, Ghobadi Sirous, Farrokhi Alireza, Khodarahmi Reza
Department of Biology, Faculty of Sciences, Razi University, Kermanshah, Iran; Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences (KUMS), Kermanshah, Iran.
Nano Drug Delivery Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran.
Int J Biol Macromol. 2022 Oct 31;219:1100-1111. doi: 10.1016/j.ijbiomac.2022.08.160. Epub 2022 Aug 29.
Disease-related tau protein in Alzheimer's disease is hyperphosphorylated and aggregates into neurofibrillary tangles. The cis-proline isomer of the pSer/Thr-Pro sequence has been proposed to act as a precursor of aggregation ('Cistauosis' hypothesis), but this aggregation scheme is not yet entirely accepted. Hence to investigate isomer-specific-aggregation of tau, proline residues at the RTPPK motif were replaced by alanine residues (with permanent trans configuration) employing genetic engineering methods. RTPAK, RTAPK, and RTAAK mutant variants of tau were generated, and their in vitro aggregation propensity was investigated using multi-spectroscopic techniques. Besides, the cell toxicity of oligomers/fibrils was analyzed and compared to those of the wild-type (WT) tau. Analyses of mutant variants have shown to be in agreement (to some degree) to the theory of the 'cistauosis' hypothesis. The results showed that the trans isomer in the 232-rd residue (P232A mutant rather than P233A) had reduced aggregation propensity. However, this study did not illustrate any statistically significant difference between the wild and the mutant protein aggregations concerning cell toxicity.
阿尔茨海默病中与疾病相关的tau蛋白发生过度磷酸化并聚集成神经原纤维缠结。pSer/Thr-Pro序列的顺式脯氨酸异构体被认为是聚集的前体（“Cistauosis”假说），但这种聚集机制尚未被完全接受。因此，为了研究tau的异构体特异性聚集，利用基因工程方法将RTPPK基序处的脯氨酸残基替换为丙氨酸残基（具有永久反式构型）。生成了tau的RTPAK、RTAPK和RTAAK突变变体，并使用多光谱技术研究了它们的体外聚集倾向。此外，分析了寡聚体/原纤维的细胞毒性，并与野生型（WT）tau的细胞毒性进行了比较。突变变体的分析结果（在某种程度上）与“Cistauosis”假说理论一致。结果表明，第232位残基处的反式异构体（P232A突变体而非P233A）的聚集倾向降低。然而，这项研究并未说明野生型和突变型蛋白聚集在细胞毒性方面有任何统计学上的显著差异。
