Fig. 4. PS deficiency affects the subcellular localization of endogenous nicastrin. Wild-type (top panel) and PS-deficient (bottom panel) MEFs were grown on coverslips at 37°C, then fixed and processed for double immunofluorescence staining using antibodies against the ER chaperone BIP (left) and nicastrin (middle). Detection was carried out with Alexa-488 and -555 conjugated secondary antibodies, respectively. In wild-type MEFs, little overlap is seen between BIP and nicastrin. By contrast, PS deficiency clearly results in increased localization of nicastrin in the ER (compare merged pictures and insets). Bar, 10 µm.