Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610064, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2012 Dec;98:199-206. doi: 10.1016/j.saa.2012.07.105. Epub 2012 Aug 31.
Pin1 is closely associated with the pathogenesis of cancers and Alzheimer's disease (AD). Previously, we have shown the characteristics of the thermal denaturation of Pin1. Herein, the acid-induced denaturation of Pin1 was determined by means of fluorescence emission, synchronous fluorescence, far-UV CD, ANS fluorescence and RLS spectroscopies. The fluorescence emission spectra and the synchronous fluorescence spectra suggested the partially reversible unfolding (approximately from pH 7.0 to 4.0) and refolding (approximately from pH 4.0 to 1.0) of the structures around the chromophores in Pin1, apparently with an intermediate state at about pH 4.0-4.5. The far-UV CD spectra indicated that acidic pH (below pH 4.0) induced the structural transition from α-helix and random coils to β-sheet in Pin1. The ANS fluorescence and the RLS spectra further suggested the exposure of the hydrophobic side-chains of Pin1 and the aggregation of it especially below pH 2.3, and the aggregation possibly resulted in the formation of extra intermolecular β-sheet. The present work primarily shows that acidic pH can induce kinds of irreversible structural changes in Pin1, such as the exposure of the hydrophobic side-chains, the transition from α-helix to β-sheet and the aggregation of Pin1, and also explains why Pin1 loses most of its activity below pH 5.0. The results emphasize the important role of decreased pH in the pathogenesis of some Pin1-related diseases, and support the therapeutic approach for them by targeting acidosis and modifying the intracellular pH gradients.
Pin1 与癌症和阿尔茨海默病（AD）的发病机制密切相关。之前，我们已经展示了 Pin1 的热变性特征。在此，通过荧光发射、同步荧光、远紫外 CD、ANS 荧光和 RLS 光谱学来确定 Pin1 的酸诱导变性。荧光发射光谱和同步荧光光谱表明，Pin1 中发色团周围结构的部分可逆展开（约从 pH 7.0 到 4.0）和重折叠（约从 pH 4.0 到 1.0），显然在 pH 4.0-4.5 左右有一个中间状态。远紫外 CD 光谱表明，酸性 pH（低于 pH 4.0）诱导 Pin1 从α-螺旋和无规卷曲到β-折叠的结构转变。ANS 荧光和 RLS 光谱进一步表明 Pin1 的疏水性侧链暴露和聚集，特别是在 pH 低于 2.3 时，而且聚集可能导致额外的分子间β-折叠的形成。本工作主要表明，酸性 pH 可以诱导 Pin1 发生多种不可逆的结构变化，如疏水性侧链的暴露、从α-螺旋到β-折叠的转变以及 Pin1 的聚集，也解释了为什么 Pin1 在 pH 低于 5.0 时失去大部分活性。结果强调了 pH 值降低在某些与 Pin1 相关疾病发病机制中的重要作用，并支持通过靶向酸中毒和改变细胞内 pH 梯度来治疗这些疾病的方法。
