Effect of 2-fluoropalmitate, cerulenin and tunicamycin on the palmitoylation and intracellular translocation of myelin proteolipid protein

We have investigated the effect of documented protein palmitoylation inhibitors on the fatty acylation and intracellular transport of myelin proteolipid protein (PLP). To this end, brain slices from 20-day-old rats were incubated with either [H-3] palmitate or [H-3] leucine in the presence or absence of various concentrations of 2-fluoropalmitate (FP), cerulenin (CER), or tunicamycin (TM). FP (greater than or equal to 10 muM) decreased the cellular uptake of [H-3] palmitate and consequently reduced the labeling of palmitoyl-CoA, glycerolipids and PLP. CER (greater than or equal to 1 mM) reduced the palmitoylation of PLP with a concomitant decline in protein thiols. Consistent with being a fatty acyl-CoA analogue, TM (greater than or equal to 200 muM) diminished the palmitoylation of PLP and lipids while increasing the amount of [H-3]palmitoyl-CoA. Although both CER and TM decreased protein palmitoylation, only the latter affected the appearance of newly synthesized PLP into myelin. Because TM, but not CER, also reduced the formation of lipids, it is concluded that palmitoylation is not required for intracellular transport. Finally, comparison of the effect of TM in brain slices and in a cell-free system suggests that palmitoylation of PLP in whole cells may be an enzymatic process.