β-Amyloid-evoked Apoptotic Cell Death is Mediated Through MKK6–p66shc Pathway
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We have previously shown the involvement of p66shc in mediating apoptosis. Here, we demonstrate the novel mechanism of β-Amyloid-induced toxicity in the mammalian cells. β-Amyloid leads to the phosphorylation of p66shc at the serine 36 residue and activates MKK6, by mediating the phosphorylation at serine 207 residue. Treatment of cells with antioxidants blocks β-Amyloid-induced serine phosphorylation of MKK6, reactive oxygen species (ROS) generation, and hence protected cells against β-Amyloid-induced cell death. Our results indicate that serine phosphorylation of p66shc is carried out by active MKK6. MKK6 knock-down resulted in decreased serine 36 phosphorylation of p66shc. Co-immunoprecipitation results demonstrate a direct physical association between p66shc and WT MKK6, but not with its mutants. Increase in β-Amyloid-induced ROS production was observed in the presence of MKK6 and p66shc, when compared to triple mutant of MKK6 (inactive) and S36 mutant of p66shc. ROS scavengers and knock-down against p66shc, and MKK6 significantly decreased the endogenous level of active p66shc, ROS production, and cell death. Finally, we show that the MKK6–p66shc complex mediates β-Amyloid-evoked apoptotic cell death.
Keywordsβ-Amyloid P66shc MKK6 Reactive oxygen species (ROS) Phosphorylation Cell death
This work was supported in part by the Department of Science and Technology, Govt. of India, No: SR/SO/BB-09/2009 and by the University Grants Commission No F. 17-82/98(SA-I). Work was also supported by FIST (SR/FST/LSI-384/2008) and SAP (F.3-26/2011 (SAP-II) grants awarded to the department by the Department of Science & Technology, Govt. of India, and University Grants Commission, Govt. of India, respectively. We are grateful to Kaikobad Irani, Associate Professor at UPMC, USA, for providing ShRNA of p66shc and SS Andrabi, Fellow at Harvard University, USA, for providing WT p66shc and WT MKK6 plasmids.
Conflict of interest
The authors declare no conflict of interest.
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