Affiliations: MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, China
Correspondence:
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Correspondence to: Prof. Da Xing, Director, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China. Tel.: +86 20 85210089; Fax: +86 20 8521 6052; E-mail: xingda@scnu.edu.cn.
Abstract: Increasing evidence supports that amyloid plaques, comprised of amyloid-β (Aβ), are a key feature of Alzheimer's disease (AD). But the mechanism of Aβ in AD is not yet fully understood. Previous studies have demonstrated that in Aβ-induced apoptosis of nerve cells, differentiated rat pheochromocytoma (PC12) cells, and microglia, nucleus factor kappa B (NF-κB) is activated. Meanwhile, focal adhesion kinase (FAK) is also activated. However, the relationship between NF-κB and FAK remains unclear. Using differentiated PC12 cells, we investigated this relationship in Aβ25-35-induced apoptosis. The results showed that FAK phosphorylation increased at 6–9 hours after Aβ treatment, slightly shorter than the activation of NF-κB (6–12 hours). In this process, both extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38MAPK) phosphorylation levels were increased. After FAK expression was inhibited by its siRNA, the activities of ERK1/2, p38MAPK, and NF-κB were all suppressed. When ERK1/2 and p38MAPK expressions were inhibited by their siRNAs respectively, NF-κB activity was also suppressed. But FAK phosphorylation was not affected. When NF-κB expression was inhibited, all of the phosphorylation levels of FAK, ERK1/2, and p38MAPK were not affected. These phenomena indicated that FAK is upstream of ERK1/2, p38MAPK, and NF-κB, and meanwhile both of ERK1/2 and p38MAPK are upstream of NF-κB. Co-immunoprecipitation results demonstrated that it is ERK1/2, but not p38MAPK, which directly interacts with IκB kinase. Taken together, our results suggest that FAK activates NF-κB via ERK1/2 and p38MAPK pathways in Aβ25-35-induced apoptosis of differentiated PC12 cells.
