Novel inhibitory action of tunicamycin homologues suggests a role for dynamic protein fatty acylation in growth cone-mediated neurite extension

Abstract

Abstract. In neuronal growth cones, the advancing tips of elongating axons and dendrites, specific protein substrates appear to undergo cycles of posttranslational modification by covalent attachment and removal of long-chain fatty acids. We show here that ongoing fatty acylation can be inhibited selectively by longchain homologues of the antibiotic tunicamycin, a known inhibitor of N-linked glycosylation. Tunicamycin directly inhibits transfer of palmitate to protein in a cell-free system, indicating that tunicamycin inhibition of protein palmitoylation reflects an action of the drug separate from its previously established effects on glycosylation. Tunicamycin treatment of differentiated PC12 cells or dissociated rat sensory neurons, under conditions in which protein palmitoylation is inhibited, produces a prompt cessation of neurite elongation and induces a collapse of neuronal growth cones. These growth cone responses are rapidly reversed by washout of the antibiotic, even in the absence of protein synthesis, or by addition of serum. Two additional lines of evidence suggest that the effects of tunicamycin on growth cones arise from its ability to inhibit protein long-chain acylation, rather than its previously established effects on protein glycosylation and synthesis. The tunicamycin-induced impairment of growth cone function can be reversed by the addition of excess exogenous fatty acid, which reverses the inhibition of protein palmitoylation but has no effect on the inhibition of protein glycosylation. These results suggest an important role for dynamic protein acylation in growth cone-mediated extension of neuronal processes.

Identification of a Novel Repressive Element That Contributes to Neuron-Specific Gene Expression

“…Lysates were harvested from cells cultured under the same conditions as for the transfection assays, and equal amounts of total cellular protein were run in each lane. The slightly slower mobility for the CAD cell GAP-43 (compared with GAP-43 from cortical neuronal cultures) could be attributed to post-translational differences, because GAP-43 can be reversibly palmitoylated (Skene and Virag, 1989;Patterson and Skene, 1994) or phosphorylated (Spencer et al, 1992).…”

Characterization of the tunicamycin gene cluster unveiling unique steps involved in its biosynthesis

“…The capabilities of inhibiting the posttranslational glycosylation of proteins make tunicamycin a useful tool in the study of protein glycosylation (Winn et al, 2010). Moreover, tunicamycins have also been shown to block N-palmitoylation of acyl-proteins by inhibiting palmitoyltransferase (Patterson and Skene, 1994;Liang et al, 2002;Price and Tsvetanova, 2007). Recent investigations performed with isotope feeding experiments have proposed a tentative pathway for tunicamycin biosynthesis (Tsvetanova et al, 2002).…”

Cerulenin, an inhibitor of protein acylation, selectively attenuates nutrient stimulation of insulin release: a study in rat pancreatic islets.

“…Following up on this hypothesis, we examined the effects of cerulenin, a fungal antibiotic that inhibits protein acylation H. YAJIMA AND ASSOCIATES (17,18), on insulin release. We were interested in this drug because covalent protein acylation by LC-CoA is involved in vesicle translocation, membrane trafficking, and exocytosis in antigen-presenting cells, pituitary cells, and neuronal cells (19)(20)(21)(22), and because acylation could be responsible for the augmentation of insulin release via the K ATP channel-independent pathways. Accordingly, our expectation was that cerulenin, if it inhibits protein acylation in pancreatic ␤-cells as it does in other cells, would attenuate glucose augmentation of insulin release.…”