Fig. 2. Cell surface localization of CEACAM1-L mutants. MDCK cells stably transfected with mouse wild-type CEACAM1-L and CEACAM1-L mutants were grown to confluent, polarized cell layers on permeable filters. Cell layers were fixed, permeabilized, and analyzed by confocal microscopy with antibodies against mouse CEACAM1. A z-reconstruction (top) and an x,y-field between the apical and the basal cell surfaces (bottom) are shown for each CEACAM1-L variant. Lateral cell surface staining is seen in wild-type CEACAM1-L and in the mutants 518, Y488F and V518A, whereas mutants 510, 495, 472, 461, Y515F, Y488,515F, 3K-3A and S503A lack lateral staining for CEACAM1-L. CEACAM1-positive intracellular vesicles are seen in several of the cells.