Figure 4: Induction of all three UPR branches by Htt96Q seems to correlate with insoluble aggregate formation. | Nature Communications

Figure 4: Induction of all three UPR branches by Htt96Q seems to correlate with insoluble aggregate formation.

From: Soluble forms of polyQ-expanded huntingtin rather than large aggregates cause endoplasmic reticulum stress

Figure 4

(a,b) Increase in phosphorylated eIF2α, GADD34 (a, PERK branch of the UPR) and ATF6 fragment levels (b) correlate with the accumulation of Htt96Q insoluble aggregates (P, pellet) over time, and not with its soluble fraction (SN, supernatant) in HEK 293 cells. (c) Spliced XBP1 mRNA levels (XBP1-s, IRE1 branch of the UPR) measured by RT–PCR analysis of parallel samples of the experiment in b also increase with Htt96Q aggregation. Tunicamycin (Tun, 5 μg ml−1) was used as a positive control for UPR induction. Values were corrected by GAPDH protein (a,b) or RT–PCR (c) as the loading control. (d) Splicing of XBP1-venus apparently correlates with the presence of large Htt96Q aggregates. XBP1-venus reporter protein, lacking its DNA-binding domain, was expressed together with myc-tagged Htt20Q or Htt96Q in STHdhQ7/7 cells. Cells were fixed and stained with anti-myc. Splicing of XBP1-venus mRNA brings venus into its correct open reading frame, producing a fluorescent protein. The fluorescence appears in Htt96Q- but not in Htt20Q-expressing cells. Scale bar, 10 μm.

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