Figure 1.
The expression levels of APP, PS1, BACE1 and Aβ were elevated in N2a/APPswe and N2a/APPwt cells.
(A) The expression of full length APP was increased in N2a/APPswe and N2a/APPwt cells compared to controls (vector-transfected). (B, C) mRNA and protein levels of PS1 and BACE1 were significantly elevated in N2a/APPswe and N2a/APPwt cells compared with control cells; (D) the downstream expression levels of Aβ1-42 and Aβ1-40 were significantly higher in N2a/APPswe and N2a/APPwt cells than control cells. *: P<0.05, as compared with N2a/APPwt cells, #: P<0.05, as compared with control cells (n = 3).
Figure 2.
H3 in PS1 and BACE1 promoters and cellular H3 were hyperacetylated in N2a/APPswe cells.
(A) the binding of acetylation H3 (Ac-H3) to PS1 and BACE1 promoter regions was markedly higher in N2a/APPswe cells than N2a/APPwt and control cells; (B) the cellular Ac-H3 was increased in N2a/APPswe cells compared with N2a/APPwt and control cells. Ip represents amplification of input DNA from cells; Ac-H3 represents DNA bound to Ac-H3 in the sample; N represents DNA precipitated by normal mouse IgG as negative control. *: P<0.05, as compared with N2a/APPwt cells, #: P<0.05, as compared with control cells (n = 3).
Figure 3.
Endogenous p300 was enhanced in N2a/APPswe cells.
(A) compared to N2a/APPwt and control cells, the p300 expression was dramatically enhanced in N2a/APPswe cells; (B) overexpression of p300 protein in N2a/APPswe cells was further confirmed by immunocytochemistry, Magnification 400-fold, Scale bar: 50 µm. (C) the HATs activity was significantly higher in N2a/APPswe cells compared to N2a/APPwt and control cells; (D) the level of p300 was higher in the promoter regions of PS1 and BACE1 in N2a/APPswe cells but not in N2a/APPwt cells compared with the controls. *: P<0.05, as compared with N2a/APPwt cells, #: P<0.05, as compared with control cells (n = 3).
Figure 4.
Hyperacetylation of PS1 and BACE1 was suppressed by p300 specific inhibitor curcumin in N2a/APPswe cells.
(A) the p300 protein was markedly decreased in N2a/APPswe cells after being treated with curcumin; (B) curcumin dramatically reduced the enhancement effect of p300 in N2a/APPswe cells by immunocytochemistry, Magnification 400-fold, Scale bar: 50 µm; (C) curcumin treatment significantly suppressed the HATs activity in N2a/APPswe cells; (D) the Ac-H3 to PS1 and BACE1 promoter regions was much lower in N2a/APPswe cells after being treated with curcumin compared to DMSO (placebo) group; (E) the cellular Ac-H3 in N2a/APPswe cells was statistically significantly decreased after curcumin treatment; (F) N2a/APPswe cells after being treated with curcumin showed reduced binding of p300 to PS1 and BACE1 in N2a/APPswe cells. (G, H, I) the PS1 and BACE1 expression, followed by their downstream products Aβ1-42 and Aβ1-40, were markedly reduced in N2a/APPswe cells after curcumin treatment. Ip represents amplification of input DNA from cells; Ac-H3 represents DNA bound to Ac-H3 in the sample; N represents DNA precipitated by normal mouse IgG as negative control. #: P<0.05, as compared with DMSO treatment cells (n = 3).
Figure 5.
p300-dependent transcription activation of PS1 and BACE1.
p300 HAT activity facilitates the histone acetylation of the PS1 and BACE1, accompanied by a more open chromatin structure that further facilitates accessibility by transcription factors to DNA-sequence of the genes, which in turn, leads to enhancement of the transcriptional activation. HAT: acetyltransferase activity; TF: transcription factor.