The ciliary trafficking of polycystin-2 requires COPII and an intact Golgi apparatus. (a–h) LLC-PK1 cells were transiently transfected with 8 µg of an expression plasmid for ECFP (a–d) or a fusion protein between ECFP and the dominant-negative Sar1 (H79G) protein (e–h) and with 6 µg of an expression plasmid for HA epitope–tagged polycystin-2 (1–703). 3 d after transfection, the cells were either stained for the HA epitope or double-stained for the HA epitope and acetylated tubulin. Whereas ECFP had no effect on the ciliary location of the truncated polycystin-2 protein, the ECFP-Sar1 (H79G) fusion protein prevented the trafficking of the truncated polycystin-2 into primary cilia. a/b, c/d, e/f, and g/h represent corresponding panels. (i–p) LtA-2,22 cells were stably transfected with expression plasmids for HA epitope–tagged full-length and polycystin-2 (1–703) proteins, and treated with brefeldin A (+BFA; i, k, m, and o) or with the solvent methanol (−BFA; j, l, n, and p). Double staining for the HA epitope and acetylated tubulin revealed that in the presence of brefeldin A the truncated and the full-length polycystin-2 protein no longer reached primary cilia. i/k, j/l, m/o, and n/p represent corresponding panels. Primary cilia are indicated by arrows. Bars: (a–h) 25 µm, (i–p) 10 µm.
