Separation and analysis of the soluble trimer of Aβ1-40 and its effects on the rise in intracellular calcium

Alzheimer’s disease (AD) is one of the progressive neurodegenerative diseases associated with protein conformational transition, generally known as protein conformational disorders[1]. The general characteriza- tions of AD are the intracellular fibrillar…

Separation and analysis of the soluble trimer of Aβ1–40 and its effects on the rise in intracellular calcium

The oligomers of Aβ_1–40 peptide in PBS buffer solution were analyzed by SEC and native PAGE, and the trimer of Aβ_1–40 was also isolated by SEC. In addition, the effects of the soluble Aβ_1–40 trimer on intracellular free calcium (Ca²⁺) balance of hippocampal neurons of postnatal rats were investigated by fluorescence microscopy. The experimental results indicated that Aβ_1–40 peptide existed in the form of low molecular weight oligomers in 0.231 mmol/L fresh Aβ_1–40 solution (20 mmol/L sodium phosphate buffer, pH 7.4, 0.02% sodium azide) within 24 h and the soluble trimer was the most abundant species. Both the trimeric and the fibrillar Aβ_1–40 were able to increase the intracellular Ca²⁺ concentration, but the Aβ_1–40 trimer caused a gradual rise and the potential was also stronger than that of the fibrils at the same concentration. In addition there were different response modes for trimeric and fibrillar Aβ_1–40, meaning that there are different mechanisms of increase in intracellular Ca²⁺ caused by Aβ_1–40.