Insufficiency of ciliary cholesterol in hereditary Zellweger syndrome (2020)
Figure 7

Figure 7 The Rabin8-Rab10-KIFC3 complex is implicated in the peroxisome-mediated supply of cholesterol into the ciliary membrane

(A) Whole-cell lysates from HEK293T cells expressing AcGFP1 or AcGFP1-tagged PEX14 and 3×FLAG-tagged KIFC3 were immunoprecipitated with anti-FLAG antibody and immunoblotted with anti-GFP or anti-FLAG antibody.

(B) Whole-cell lysates from HEK293T cells expressing AcGFP1-tagged KIFC3 and 3×FLAG-tagged Rab10 or Rab10-Q68L were immunoprecipitated with anti-FLAG antibody and immunoblotted with anti-GFP or anti-FLAG antibody.

(C) Whole-cell lysates from HEK293T cells expressing AcGFP1-tagged Pex14 and 3×FLAG-tagged Rab10 or Rab10-Q68L were immunoprecipitated with anti-FLAG antibody and immunoblotted with anti-GFP or anti-FLAG antibody.

(D) Western blot analysis of the ciliary cholesterol trafficking-associated components in Pex1+/+ and Pex1−/− hTERT-RPE1 cells. Total cell lysates were separated to crude peroxisomal (Crude Pex), lysosomal and mitochondrial (Lyso/Mito), and peroxisomal (PEX) fractions. CYPOR, a lysosomal and mitochondrial protein, served as a positive control for the Lyso/Mito fractionation. Total cell lysates were gradually injected at 20 µg and 5 µg into a gel for SDS-PAGE, while equal amounts (5 µg) of protein from each fraction were loaded. Rabin8, Rab10, and KIFC3 were concentrated in the PEX fraction in Pex1+/+ hTERT-RPE1 cells. CYPOR (cytochrome P450 reductase) is a mitochondrial protein.

(E) Quiescent G0-phase hTERT-RPE1 cells transfected with 3×FLAG-tagged KIFC3 were immunostained with anti-FLAG (green), anti-PEX14 (red), and anti-α-tubulin (white) antibodies. Magnified 3D-constituted images of the boxed regions showing peroxisomes are located on the microtubule arrays via KIFC3 (arrows). The scale bars indicate 5 μm.

(F) Western blot analysis showing depletion of KIFC3 in the KIFC3−/− hTERT-RPE1 cell clones. GAPDH served as a loading control.

(G) KIFC3+/+ and KIFC3−/− 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.

(H) Quantification of (G) indicating that KIFC3−/− hTERT-RPE1 cells significantly reduced the ciliary accumulation of 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.

(I) Quiescent G0-phase KIFC3+/+ and KIFC3−/− hTERT-RPE1 cells were immunostained with anti-ARL13B (blue), anti-phospho-S473-Akt (red), anti-ninein (green), and anti-PMP70 (white) antibodies. Arrows represent the peroxisomes contacting the ciliary pocket. Scale bar, 5 μm.

(J) Quantification of (I) showing that disruption of the KIFC3 gene significantly interfered with the contact 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).

(K) KIFC3−/− hTERT-RPE1 cells were transfected with AcGFP1, AcGFP1-tagged KIFC3, rod domain-deleted KIFC3 mutant (ΔRod), or motor domain-deleted KIFC3 mutant (ΔMotor) and cultured without serum for 24 h before Filipin-III (green)-mediated cholesterol staining and immunostaining with anti-GFP (red), anti-pericentrin (white), and anti-acetylated-tubulin (blue) antibodies. Arrows represent ciliary localization of cholesterol. The scale bars indicate 5 μm.

(L) Quantification of the Filipin III intensity at primary cilia from (K). AcGFP1-tagged KIFC3 deletion mutants did not restore the ciliary cholesterol insufficiency in the KIFC3−/− hTERT-RPE1 cells (mean +/- s.d.: ***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.