ER stress does not contribute to loss of peroxisomes in UBXD8 null cells. (A) HeLa cells were transfected with control or two different HRD1 siRNAs and stained for catalase. (B) Quantification of the number of peroxisomes per cell, at least 100 cells were analyzed in N = 3 independent experiments. The violin plot shows median and 95% confidence intervals. ns: not significant, ****P < 0.0001. One-way ANOVA with Dunnett’s multiple comparisons test. (C) Immunoblot showing depletion of Hrd1. (D) HEK293T WT cells and GP78 KO cells stained for catalase. (E) Quantification of peroxisome per cell in C. At least 100 cells were analyzed in N = 3 independent experiments. The violin plot shows median and 95% confidence intervals. ****P < 0.0001, unpaired t test. (F) Immunoblot of GP78. (G) HeLa WT and UBXD2 KO cells stained for peroxisomes using catalase. (H) Quantification of peroxisomes per cell from C. At least 100 cells were analyzed in N = 3 independent experiments. The violin plot shows median and 95% confidence intervals. ns: not significant, unpaired t test. (I and J) Immunoblots of HeLa WT (untreated or treated with DTT) and UBXD8 KO cells for ER stress markers BiP and ATF4. N = 3. (J) RT-qPCR of xbp1 total and xbp1 spliced (xbp1s) mRNA transcripts in WT and UBXD8 KO cells treated with 1.5 mM DTT for 4 h. N = 3. ns: not significant, *P < 0.01, ****P < 0.0001, two-way ANOVA with Dunnett’s post hoc analysis. The scale bar is 10 μM. Source data are available for this figure: SourceData F3.