Fig. 8. Inhibition of N-linked glycosylation leads to an increase of mutant opsin ER staining. The colocalisation of WT (WT-opsin) and mutant opsins (P23H-opsin and K296E-opsin) with the ER marker calnexin in untreated cells is shown in the top row (Untreated). Inhibition of protein glycosylation with tunicamycin (0.8 µg/ml for 8 hours) led to an increase in the level of mutant protein retained within the ER. The trafficking of the WT protein (WT-opsin) to the plasma membrane was not affected by the treatment with tunicamycin and showed no increase in ER staining. By contrast, the mutant proteins (P23H-opsin and K296E-opsin) accumulated in the ER as shown by colocalisation with the ER-membrane-bound lectin chaperone calnexin. Bar, 10 µm.