Peroxiredoxin I regulates the component expression of γ-secretase complex causing the Alzheimer's disease

Abstract

Peroxiredoxin I (Prx I) is a member of the peroxiredoxins (Prxs) family, which are antioxidant enzymes that regulate various cellular process via intracellular oxidative signal pathways. In order to investigate the correlation between Prx I and the γ-secretase complex, which causes Alzheimer's disease (AD), the expression level of Prx I was firstly evaluated in an animal model for AD. NSE/hPen-2 transgenic (Tg) mice, which were used as animal model in this study, showed a high level of Pen-2 expression and accumulation of Aβ-42 peptides in the hippocampus of brain. The expression level of Prx I was significantly higher on the mRNA and protein level in the brain of this model, while not change in Prx VI expression was observed. Furthermore, to verify the effect of Prx I on the γ-secretase components in vitro, the expression level of these components was analyzed in the Prx I transfectants. Of the components of the γ-secretase complex, the expression of PS-2 and Pen-2 was lower in the transfectants overexpressing Prx I compared to the vector transfectants. However, the expression of APP, NCT and APH-1 did not change in Prx I transfectants. Therefore, these results suggested that the expression of Prx I may be induced by the accumulation of Aβ-42 peptides and the overexpression of Prx I in neuroblastoma cells may regulate the expression of γ-secretase components.

Keywords: Alzheimer's disease; Aβ-42 peptides; Peroxiredoxin I; γ-secretase complex.

Figure 1

Pen-2 expression and accumulation of Aβ-42 peptides in the brain of CMV/hPen-2 Tg mice. (A) Brain specific expression of the hPen-2 transgenes in the Tg mice by RT-PCR. The β-actin signal was used as the control, and the transcript (640-bp) indicates RNA loading. In addition, the RT-PCR products for hPen-2 (284-bp) are indicated. The density of the amplified transcripts was quantified. (B) Immunostaining analysis of the Aβ-42 peptides. The brains were taken from NSE/hPen-2 Tg mice and Non-Tg mice after perfusion. The level of the Aβ-42 peptide was detected in the immunostaining analysis using an Aβ-42 specific antibody. A high intensity was observed in the hippocampus of the NSE/hPen-2 Tg mice when compared with the Non-Tg mice at 200× magnification. The data represents the mean±SD from three replicates. ^*P<0.05; significant difference between NSE/hPen-2 Tg and Non-Tg mice.

Figure 2

Expression of Prx I and VI mRNA and protein in the brain of NSE/hPen-2 Tg and Non-Tg mice. (A and B) Total RNA was purified from the whole brain of both mice, and the gene expression of the Prx I and VI were detected by RT-PCR. The β-actin signal was used as the control, and the transcript (640-bp) indicates the RNA loading. (C and D) Total tissue lysates were prepared from the brain tissue of NSE/hPen-2 Tg and Non-Tg mice as described in the Materials and Methods sections. Fifty micrograms of protein per sample were immunoblotted using antibodies for each protein. Three samples were assayed in triplicate via Western blotting. The values are expressed as the means±SD. ^*P<0.05; significant difference between NSE/hPen-2 Tg and Non-Tg mice.

Figure 3

Effects of the overexpression of Prx I on the component expression of γ-secretase complex in SH-SY5Y cells. (A) Construction of CMV/hPrx I plasmid. The pCMV/hPrx I harbors the cDNA encoding hPrx I under the control of the CMV gene promoter. (B and C) Total cell lysates were prepared from SH-SY5Y cells transfected with CMV control vector and CMV/hPrx I vector as described in the Materials and Methods section. Fifty micrograms of protein per sample were immunoblotted using antibodies for each protein. Three samples were assayed in triplicate via Western blotting. The values were expressed as means±SD. ^*P<0.05 is the significance level compared to the vehicle-treated group.