Figure 4. Rpgrip1l deficiency causes impaired proteasomal activity at primary cilia. (A–F and I–L) MEFs were isolated from E12.5 WT and Rpgrip1l−/− embryos. (A and B) Western blot analysis of WT and Rpgrip1l−/− MEF lysates (n = 4 embryos, respectively). (C) Western blot analysis of WT and Rpgrip1l−/− MEF lysates (n = 3 embryos, respectively). (A–C) Actin serves as a loading control. (A) Phospho-(S33/37/T41)-β-Catenin is significantly increased in serum-starved Rpgrip1l−/− MEF lysates (82% of all cells had cilia; in serum-starved Rpgrip1l+/+ MEF lysates, 88.67% of all cells possessed cilia) but not in non–serum-starved Rpgrip1l−/− MEF lysates (4% of all cells displayed cilia; in non–serum-starved Rpgrip1l+/+ MEF lysates, 6.67% of all cells carried cilia; C). (B) Non–phospho-(S33/37/T41)-β-Catenin is unaltered in serum-starved Rpgrip1l−/− MEF lysates. Black lines indicate that intervening lanes have been spliced out. (D–F, I, and L) Immunofluorescence on MEFs of E12.5 WT and Rpgrip1l−/− embryos (both genotypes: p-β-Catenin: n = 5; p-β-Catenin (3D-SIM, n = 3; Ubiquitin, n = 4; Gli3-190, n = 6; ZsProSensor-1, n = 3; n refers to the number of embryos, respectively). Per embryo, 15 cilia were quantified for p-β-Catenin, 10 cilia were quantified for p-β-Catenin (3D-SIM) and for Ubiquitin, and 20 cilia were quantified for Gli3-190. (G and H) Immunofluorescence on limbs of E12.5 WT and Rpgrip1l−/− embryos (n = 3 embryos, respectively). Per embryo, 20 cilia were quantified for p-β-Catenin and Ubiquitin. All quantified proteins are shown in red (D–J), the ciliary axoneme is marked by acetylated α-tubulin (green; D–J), and the BB is marked by γ-tubulin (blue; D–F, H, and I) or by Pcnt2 (blue; G). (J and K) Immunofluorescence on MEFs of WT embryos (n = 4). 25 cilia per embryo were used for phospho-(S33/37/T41)-β-Catenin and cilia length quantification. (L) Proteasome activity assay on WT and Rpgrip1l−/− MEFs. Cilia are marked by acetylated α-tubulin (α-Tub), and centrosomes/basal bodies are marked by γ-tubulin. Colored squares mark cilia with basal bodies (yellow squares) as well as centrosomes (red squares), which are presented magnified. The green ZsProSensor-1 protein signal is exclusively detected at the ciliary base in Rpgrip1l−/− MEFs. Error bars show standard error of the mean. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Bars, 1 µm.
Figure 4.

Rpgrip1l deficiency causes impaired proteasomal activity at primary cilia. (A–F and I–L) MEFs were isolated from E12.5 WT and Rpgrip1l−/− embryos. (A and B) Western blot analysis of WT and Rpgrip1l−/− MEF lysates (n = 4 embryos, respectively). (C) Western blot analysis of WT and Rpgrip1l−/− MEF lysates (n = 3 embryos, respectively). (A–C) Actin serves as a loading control. (A) Phospho-(S33/37/T41)-β-Catenin is significantly increased in serum-starved Rpgrip1l−/− MEF lysates (82% of all cells had cilia; in serum-starved Rpgrip1l+/+ MEF lysates, 88.67% of all cells possessed cilia) but not in non–serum-starved Rpgrip1l−/− MEF lysates (4% of all cells displayed cilia; in non–serum-starved Rpgrip1l+/+ MEF lysates, 6.67% of all cells carried cilia; C). (B) Non–phospho-(S33/37/T41)-β-Catenin is unaltered in serum-starved Rpgrip1l−/− MEF lysates. Black lines indicate that intervening lanes have been spliced out. (D–F, I, and L) Immunofluorescence on MEFs of E12.5 WT and Rpgrip1l−/− embryos (both genotypes: p-β-Catenin: n = 5; p-β-Catenin (3D-SIM, n = 3; Ubiquitin, n = 4; Gli3-190, n = 6; ZsProSensor-1, n = 3; n refers to the number of embryos, respectively). Per embryo, 15 cilia were quantified for p-β-Catenin, 10 cilia were quantified for p-β-Catenin (3D-SIM) and for Ubiquitin, and 20 cilia were quantified for Gli3-190. (G and H) Immunofluorescence on limbs of E12.5 WT and Rpgrip1l−/− embryos (n = 3 embryos, respectively). Per embryo, 20 cilia were quantified for p-β-Catenin and Ubiquitin. All quantified proteins are shown in red (D–J), the ciliary axoneme is marked by acetylated α-tubulin (green; D–J), and the BB is marked by γ-tubulin (blue; D–F, H, and I) or by Pcnt2 (blue; G). (J and K) Immunofluorescence on MEFs of WT embryos (n = 4). 25 cilia per embryo were used for phospho-(S33/37/T41)-β-Catenin and cilia length quantification. (L) Proteasome activity assay on WT and Rpgrip1l−/− MEFs. Cilia are marked by acetylated α-tubulin (α-Tub), and centrosomes/basal bodies are marked by γ-tubulin. Colored squares mark cilia with basal bodies (yellow squares) as well as centrosomes (red squares), which are presented magnified. The green ZsProSensor-1 protein signal is exclusively detected at the ciliary base in Rpgrip1l−/− MEFs. Error bars show standard error of the mean. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Bars, 1 µm.

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