23] Inhibition of dynamic protein palmitoylation in intact cells with tunicamycin

Abstract

This chapter discusses the inhibition of dynamic protein palmitoylation in intact cells with tunicamycin (TM). Biological roles of protein palmitoylation are investigated principally through mutational analysis of individual protein substrates. The only documented inhibitor of protein palmitoylation in intact cells is the antibiotic cerulenin. The fatty acid containing nucleoside antibiotic TM can inhibit palmitoylation of some proteins that are resistant to cerulenin. Tunicamycin is also known to inhibit protein glycosylation. The experimental criteria for distinguishing the effects of TM on intact cells that can be attributed specifically to its ability to inhibit posttranslational protein palmitoylation are also described. The conceptual bases for distinguishing the effects of TM on protein glycosylation and palmitoylation arise from differences in the mechanisms of TM inhibition of the two protein modifications and the degree of dependence on protein synthesis. Tunicamycin inhibits N-linked glycosylation by acting as a transition-state analog for the enzyme UDP-GlcNAc:dolichylphosphate GlcNAc-1-phosphate transferase. Protein synthesis inhibitors can be used to disrupt N-linked glycosylation and the cotranslational component of palmitoylation without directly affecting the more dynamic posttranslational protein palmitoylation.