Rab35 controls cilium length, function and membrane composition (2019)
Figure 5

Figure 5. Rab35 regulates Arl13b levels at the ciliary membrane

A, B hTERT-RPE1 cells and hTERT-RPE1 cells stably expressing siRNA-resistant GFP-RAB35 transfected with non-targeting siRNA control (Neg) or Rab35 siRNA, were serum-starved for 48 h and stained for ARL13B, GFP, polyglutamylated tubulin (polyglu. tub.) and DNA. Representative images are shown in (A). Regions within white boxes shown at higher magnifications to the right. Scale bars; 10 µm. (B) Box-and-whisker plots show quantification of ciliary ARL13B intensity in arbitrary units (a. u.). Horizontal lines show 25, 50 and 75th percentiles; whiskers extend to minimum and maximum values. One representative experiment out of three is shown (n > 25 cilia per experimental condition). Statistical significance according to Kruskal-Wallis followed by Dunn's post-hoc test (** P < 0.01, *** P < 0.001, n.s.: non-significant; P-values: hTERT-RPE1-Neg vs. hTERT-RPE1-RAB35-1 P < 0.0001, hTERT-RPE1-Neg vs. hTERT-RPE1-RAB35-1 P = 0.0001, hTERT-RPE1-RAB35-1 vs. GFP-RAB35-RAB35-1 P = 0.0014, hTERT-RPE1-RAB35-2 vs. GFP-RAB35-RAB35-2 P = 0.0081).

C Immunoblot analysis of total ARL13B protein levels in control and RAB35-depleted cells. β-tubulin served as a loading control. The graph shows ARL13B protein levels normalized (norm.) to β-tubulin. Data are mean ± S.E.M. of 4 independent experiments.

D,E NIH3T3 wild type (WT) and Rab35 knockout (KO) cell lines were serum-starved for 24h and stained for Arl13b, acetylated tubulin (acetyl. tub.) and DNA. Representative images are shown in (D). Higher magnifications of regions within white boxes shown at the bottom. Scale bars; 10 µm. (E) Box-and-whisker plots show quantification of ciliary Arl13b intensity in arbitrary units (a. u.). Horizontal lines show 25, 50 and 75th percentiles; whiskers extend to minimum and maximum values. One representative experiment out of three is shown (n > 25 cilia per experimental condition). Statistical significance according to Kruskal-Wallis followed by Dunn's post-hoc test (* P < 0.05; P-values: NIH3T3 WT vs. Rab35 KO#1 P = 0.0118, NIH3T3 WT vs. Rab35 KO#2 P = 0.0111).

F Immunoblot analysis of total ARL13B protein levels in serum-starved NIH3T3 WT and Rab35 KO cell lines. β-tubulin served as a loading control.

G, H Quantification of ciliary ARL13B intensity in hTERT-RPE1 cells depleted of GEF (G) and GAP (H) regulators of RAB35. Cells transfected with indicated siRNAs were serum-starved for 48 h and stained for ARL13B, acetylated tubulin and DNA. Representative images are shown in (Fig EV4C and D). Horizontal lines show 25, 50 and 75th percentiles; whiskers extend to minimum and maximum values. One representative experiment out of three is shown (n > 30 cilia per experimental condition). Statistical significance according ANOVA followed by Bonferroni post-hoc test (*** P < 0.001; P-values: (G) P = 0.0005, (H) P < 0.0001).

I, J Ciliary ARL13B intensity quantification of hTERT-RPE1 cells transiently overexpressing GFP or GFP-RAB35. Cells were serum-starved for 24 h and stained for ARL13B, acetylated tubulin (acetyl. tub.) and DNA. Representative images are shown in (I). Higher magnification images of the cilia region are shown at the bottom. Scale bars; 5 µm. Cells with (RAB35+ cilia) and without (RAB35- cilia) GFP-RAB35 ciliary localisation are compared in (J). Horizontal lines show 25, 50 and 75th percentiles; whiskers extend to minimum and maximum values. One representative experiment out of three is shown (n > 25 cilia per experimental condition). Statistical significance according to Kruskal-Wallis followed by Dunn's post-hoc test (*** P =0.0004).