Oligomerization of a membrane protein correlates with its retention in the Golgi complex

Brefeldin A (5 /tg/ml final concentration) was diluted into serum-free medium from a 5 mg/ml stock in ethanol immediately before use. Colehicine (25 mM) was prepared in DMSO, diluted 1:10 into serum-free, methionine-free medium, and added to cells (50 ~tM final concentration) starting 1 h before metabolic labeling. Cytochalasin D (0.1 M in DMSO) was added to cells (100/~M final concentration) 2 h after infection and ineluded in subsequent changes of medium. An equal volume of DMSO was added to control cells. In experiments involving cell treatment with CCCP, ceils were starved in glucose-, methionine-, and cysteine-free medium for 15 rain before metabolic labeling in the same medium for 5 win. CCCP (0.1 M stock in DMSO) was added at the beginning of the chase in glucosefree medium to a final concentration of 300 #M.