Overexpression of N141I PS2 increases γ-secretase activity through up-regulation of Presenilin and Pen-2 in brain mitochondria of NSE/hPS2m transgenic mice

Alzheimer's disease (AD) is known to induce alterations of mitochondrial function such as elevation of oxidative stress and activation of apopotosis. The aim of this study was to investigate the effects of human Presenilin 2 mutant (hPS2m) overexpression on the γ-secretase complex in the mitochondrial fraction. To achieve this, alterations of γ-secretase complex expression and activity were detected in the mitochondrial fraction derived from brains of NSE/hPS2m Tg mice and Non-Tg mice. Herein, the following were observed: i) overexpression of the hPS2m gene significantly up-regulated the deposition of Aβ-42 peptides in the hippocampus and cortex of brain, ii) overexpression of hPS2m protein induced alterations of γ-secretase components such as main component protein and activator protein but not stabilization-related proteins, iii) changes in γ-secretase components induced by overexpression of hPS2m protein up-regulated γ-secretase activity in the mitochondrial fraction, and iv) elevation of γ-secretase activity induced production of Aβ-42 peptides in the mitochondrial fraction. Based on these observations, these results indicate that alteration of γ-secretase activity in cells upon overexpression of hPS2m is tightly linked to mitochondrial dysfunction under the specific physiological and pathological conditions of AD.