非酶糖基化对α-synuclein分子构象的影响

Nonenzymatic Glycation of α-Synuclein and Changes in Its Conformation

将纯化后的α-synuclein分别与果糖和葡萄糖孵育,通过内源荧光、非酶糖基化衍生物特征荧光、圆二色光谱以及电子显微镜等技术进行检测发现:α-synuclein与还原糖共同孵育后,308nm内源荧光强度明显降低,同时在447nm产生一个非酶糖基化衍生物特征荧光.与果糖孵育的蛋白质样品其非酶糖基化特征荧光的出现速度快于葡萄糖孵育样品.内源荧光与非酶糖基化特征荧光之间存在能量传递现象,提示Tyr残基与非酶糖基化特征荧光发色团在空间距离上彼此接近.圆二色光谱测定结果显示,α-synuclein与果糖孵育后,其α-螺旋含量增加.非酶糖基化的α-synuclein在电子显微镜下表现为短纤维状.非酶糖基化可以诱导α-synuclein蛋白分子聚集,且果糖较葡萄糖更容易使α-synuclein发生非酶糖基化.以上结果提示,非酶糖基化似乎可以导致α-synuclein在细胞内的错误折叠和分子聚集.

During the incubation of purified α-synuclein with fructose or glucose, it was observed that the protein intrinsic fluorescence at 308 nm decreased while the fluorescence of glycated derivant at 447 nm increased. This fluorescence representing nonenzymatic glycation of α-synuclein was more rapidly formed in the presence of fructose than that of glucose. Interestingly, an energy transfer could be observed from the intrinsic fluorescence to the nonenzymatic glycating fluorescence, suggesting a near distance between Tyr residues and the nonenzymatic glycated derivant. Experiments using circular dichroism showed that the content of α-helix of nonenzymatic glycated α-synuclein was increased during the nonenzymatic glycation, especially incubated with fructose. The nonenzymatic glycated α-synuclein was in some rod-like filaments under the electronic microscope. That is to say, nonenzymatic glycation induces the conformational changes of α-synuclein which is more vulnerable to the nonenzymatic glycation of fructose. It appears that nonenzymatic glycation induces α-synuclein misfolding and probably aggregation in cell.