Fig. 2. Localization of wt FATP4. (A) Expression of FATP4 in COS cells. Lysozyme-KDEL (green) was cotransfected as an ER marker protein. Staining of the nuclear envelope and the reticular network-like pattern (inset) indicates ER localization. Both proteins clearly label the same structure but there is some microheterogeneity. Inhibition of protein synthesis using cycloheximide did not change the localization pattern of FATP4. Shown is a single confocal plane. Bar, 10 µm. (B) Coexpression of FATP4 and a plasma membrane marker protein (ICAM-1-GFP) in Vero cells. There is no significant overlap, which is especially evident at the edge shown in the magnified inset. Bar, 10 µm. (C) Codistribution of endogenous FATP4 with ER membranes after subcellular fractionation. A postnuclear supernatant was prepared from HeLa cells and analyzed by velocity-controlled density centrifugation on an Optiprep step gradient. Fractions were collected from top to bottom and analyzed by SDS-PAGE and western blotting. Calnexin and Na⁺K⁺-ATPase served as markers for the ER and the plasma membrane, respectively.