Bidirectional interplay of HSF1 degradation and UPR activation promotes tau hyperphosphorylation
Fig 2
Chronic UPR activation and aberrantly hyperphosphorylated tau aggregation in the hippocampus of aged HSF1 haploinsufficient mouse.
(A, B, and D) Western blot assays to examine protein expression levels of total tau (Tau46), p-Tau (at Ser202/Thr205 and Thr212/Ser214) and UPR marker proteins (p-PERK, p-eIF2α, eIF2α, and CHOP) in the hippocampus of WT (HSF1+/+) and HSF1+/- at 2 months of age (A) and hippocampus of WT and HSF1+/- at 9 months of age (B, D). (B) Increased p-PERK (Thr980) and CHOP protein expression in the hippocampus of 9 month-old HSF1 heterozygous knock-out mice (HSF1+/-). Relative protein levels of CHOP and p-PERK (Thr980) normalized to β-actin in WT and HSF1 +/- at ~9 months of age are presented in the graph (right, means ± SEM, **P < 0.01, ***P < 0.001, n = 6). Western blots of RIPA-soluble tau (A and D) and sarkosyl-insoluble tau aggregates (D) in the mouse hippocampus. #: 72~80 kDa tau isoform, *: ~ 68 kDa tau isoform, arrow head indicates ~64 kDa tau isoform, **: ~110 kDa high molecular weight tau isoform. (C) Representative confocal images of immunohistochemistry on the hippocampus of HSF1 +/- and WT at 13 months of age. co-immunostaining of p-Tau (Ser202/Thr205, red), p-PERK (Thr980) (green), and DAPI (blue) in HSF1+/-. Arrow heads indicate co-localization of p-PERK and p-Tau (Ser202/Thr205) in the middle panels, enlarged images of top panels. Five repeated experiments performed. Scale bars: 5 μM. (E) A graph shows quantitative measurement of the relative tau phosphorylation normalized to total tau (Tau46) in the hippocampus of WT and HSF1+/- at 2, 6, and 9 months of age. Two distinct p-Tau antibodies (AT8 (Ser202/Thr205) and AT100 (Thr212/Ser214)) used. (means ± SEM, *P < 0.05, **P < 0.01, n = 3 (2 months), n = 4 (6 months) n = 6 (9 months)). (F) Double staining with thioflavin S (green, a) and Tau46 antibody (red, b) in the hippocampus of 13 month-old HSF1 +/-. Merged images of the hippocampus of HSF1+/- (c). Globose-type NFTs and diffuse plaques containing tau aggregates in the cortical areas adjacent to the hippocampus of HSF1+/- (d-i). Scale bar: 1 mm.