Insufficiency of ciliary cholesterol in hereditary Zellweger syndrome (2020)
Figure 6

Figure 6 Rabin8 cooperates with Rab10 to control the peroxisome-mediated supply of cholesterol to the ciliary membrane

(A) Rabin8+/+ and Rabin8−/− hTERT-RPE1 cells incubated for 24 h without serum were immunostained with anti-pericentrin (red) and anti-acetylated tubulin (blue) antibodies. Cholesterol was stained with Filipin III (green). Scale bar, 5 μm.

(B) Quantification of the Filipin III intensity at primary cilia from (A). Rabin8−/− hTERT-RPE1 cells exhibited a significant reduction of ciliary cholesterol (***p<0.001: one-way ANOVA with Tukey's HSD, n=3: 40-50 cells per experiment). In the boxplot, medians, 25th/75th percentile and min/max were represented by the central lines, the box limits, and the whiskers/error bars, representatively.

(C) Quiescent G0-phase Rabin8+/+ and Rabin8−/− hTERT-RPE1 cells were immunostained with anti-ARL13B (blue), anti-phospho-S473-Akt (red), anti-ninein (green), and anti-PMP70 (white) antibodies. Arrow indicates the peroxisomes contacting the ciliary pocket. Scale bar, 5 μm.

(D) Quantification of (C) indicating that disruption of the Rabin8 gene significantly inhibited the spatial interaction between peroxisomes and primary cilia (mean ± s.d.: ***p<0.001: one-way ANOVA with Tukey's HSD, n=3: 45-50 cells per experiment).

(E) Schematic representation of the rapamycin-inducible peroxisome targeting to the ciliary pocket system.

(F) Quiescent G0-phase hTERT-RPE1 cells transiently expressing PEX3-GFP-FRB (green) and tdTomato-BicD2-FKBP (red) treated with rapamycin were imaged live for 10 min by confocal microscopy (Movie EV10). Scale bar, 5 μm.

(G) Quiescent G0-phase Rabin8+/+ and Rabin8−/− hTERT-RPE1 cells transfected with PEX3-GFP-FRB (red) and tdTomato-BicD2-FKBP (white) were treated with or without 100 μM rapamycin for 30 min, and then immunostained with anti-acetylated-tubulin (blue) antibody. Cholesterol was stained with Filipin III (Green). Arrows indicate the enrichment of ciliary cholesterol. The scale bars represent 5 μm.

(H) Quantification of the Filipin III intensity at primary cilia from (G). Rapamycin-induced peroxisome targeting to the ciliary pocket restored the reduction of ciliary cholesterol in the Rabin8−/− hTERT-RPE1 cells (***p<0.001: one-way ANOVA with Tukey's HSD, n=3: 40-50 cells per experiment). In the boxplot, medians, 25th/75th percentile and min/max were represented by the central lines, the box limits, and the whiskers/error bars, representatively.

(I) Rabin8−/− hTERT-RPE1 cells were transfected with AcGFP1-tagged Rabin8, GFP-tagged Rab8A, GFP-tagged Rab8A-Q67L (constitutively active form), GFP-Rab8B, GFP-Rab8B-Q67L (constitutively active form), AcGFP1-tagged Rab10, or AcGFP1-tagged Rab10-Q68L (constitutively active form), and then immunostained with anti-GFP (red), anti-acetylated-tubulin (blue), and anti-ninein (white) antibodies. Cholesterol was stained with Filipin III (Green). Arrows indicate the enrichment of ciliary cholesterol. The scale bars represent 5 μm.

(J) Quantification of (I) showing that AcGFP1-tagged Rabin8 and AcGFP1-tagged Rab10-Q68L effectively restored the defect in ciliary enrichment of cholesterol in Rabin8−/− hTERT-RPE1 cells (***p<0.001: one-way ANOVA with Tukey's HSD, n=3: 35-40 cells per experiment). In the boxplot, medians, 25th/75th percentile and min/max were represented by the central lines, the box limits, and the whiskers/error bars, representatively.