In vitro insertion of the myelin proteolipid apoprotein into oligodendrocyte plasma membranes.

Uncoated vesicles (UCV) loaded with the myelin proteolipid apoprotein covalently tagged with fluorescein (PLPF) were found to interact with isolated oligodendrocytes from bovine brain at 4 degrees C as well as at 37 degrees C. After 1.5 hours of incubation, the labeled protein was localized in the cell membranes. After 2.5 hours the fluorescence intensity associated with the oligodendrocytes decreased and completely disappeared at t = 3.5 hours. Addition of KCl or EDTA in the incubation medium significantly hindered the interaction with cells. In contrast, the elimination of membrane proteins from UCV did not perturb cell labeling. A specific role of PLP was suggested since UCV loaded with a soluble protein (BSAF) led to a weak cell labeling.