The HSP40 chaperone Ydj1 drives amyloid beta 42 toxicity (2022)
Figure 3

Figure 3. Ydj1 is required for Abeta42-induced cell death and drives Abeta42 oligomer formation and translocation to mitochondria.

(A-B) Quantification of cells positive for PI indicating cell death at indicated time points after start of expression of EGFP-A42 (A42) or EGFP empty vector (ev) of wild type (WT) (A) and YDJ1 deleted (Δydj1) cells (B). Mean ± s.d.. n = 5 biologically independent cultures. Comparisons by two-way ANOVA (mixed-design) followed by simple main effects (***, p < 0.001, vs. control).

(C) Immunoblot of whole cell extract (Input) and eluate of FLAG-tagged Ydj1. Immunoprecipitation (IP: FLAG) of YDJ1 deletion strain (Δydj1) cells expressing EGFP-A42 (A42) or EGFP empty vector (ev) and co-overexpressing Ydj1-FLAG using Abeta-specific antibody (6E10) and FLAG antibody (FLAG).

(D) Confocal microscopy of wild type (WT) yeast cells expressing EGFP-A42 (A42) only and co-overexpressing Ydj1-FLAG or with the corresponding vector control after 18 h of expression. Colors indicate fluorescence intensity.

(E) Confocal microscopy of wild type (WT) yeast cells expression of EGFP-A42 (A42) and co-overexpressing Ydj1-FLAG after 18 h of expression. Mitochondria were visualized with MitoTracker Red (magenta). See also Fig EV2J, EV1C.

(F) Immunoblot of total cytoplasmic post-nuclear supernatant (PNS), mitochondrial (Mito.), microsomal (Micro.) and cytosolic (Cyt.) fractions of wild type (WT) and YDJ1 deletion strain (Δydj1) cells after 18 h of expression of EGFP-A42 (A42) and co-overexpressing Ydj1-FLAG or corresponding empty vector controls (ev) using Abeta-specific antibody (Abeta) 6E10 with long (Long exp.) and short time exposure (Short exp.). Tom22-specific antibody is a marker for mitochondria, Sec61 for microsomes and Ssa1 was used to verify cytosolic fraction.

(G-H) Ratio of full length EGFP-A42 in the mitochondrial fraction / cytosolic fraction, using densitometry quantification of the immunoblot representatively shown in Fig 3F and Appendix Fig S1C from three/4 independent experiments. Dot plots show all data points along with the mean (line/bar) ± s.d.. n = 3-4 biologically independent cultures. *, p < 0.05. Unpaired, two-tailed t-test.

(I) Assay for protein degradation using cycloheximide (CH) to stall protein translation. EGFP fluorescence intensity was measured at two time points (t0 and t2, 2 h after CH administration) and normalized to t0 in wild type (WT) and YDJ1 deletion strain (Δydj1) cells after 18 h of expression of EGFP-A42 (A42) and co-overexpressing Ydj1-FLAG or corresponding empty vector controls (ev). Dot plots show all data points along with the mean (bar) ± s.d.. n = 8 biologically independent cultures. ***, p < 0.001. ANOVA with Tukey's post-hoc. See also Appendix Fig S2D.

(J-K) Quantification of the ratio between EGFP-A42 tetramer and monomer in wild type (WT) and YDJ1 deletion strain (Δydj1) expressing EGFP-A42 (J) as well as between WT expressing EGFP-A42 only and co-overexpressing Ydj1-FLAG (K) at indicated time points. Dot plots show all data points along with the mean (bar) ± s.d.. n = 8(J) n=12(K) biologically independent cultures. ***, p < 0.001; **, p < 0.01; *, p < 0.05. ANOVA with Tukey's post-hoc test. See also Appendix Fig S2A-B.