The Role of Palmitoylation in Functional Expression of Nicotinic α7 Receptors

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Abstract
Neuronal α-bungarotoxin receptors (BgtRs) are nicotinic receptors that require as yet unidentified post-translational modifications to achieve functional expression. In this study, we examined the role of protein palmitoylation in BgtR expression. BgtR α7 subunits are highly palmitoylated in neurons from brain and other cells capable of BgtR expression, such as pheochromocytoma 12 (PC12) cells. In PC12 cells, α7 subunits are palmitoylated with a stoichiometry of approximately one palmitate per subunit, and inhibition of palmitoylation blocks BgtR expression. In cells incapable of BgtR expression, such as human embryonic kidney cells, α7 subunits are not significantly palmitoylated. However, in these same cells, chimeric subunits with the N-terminal half of α7 fused to the C-terminal half of serotonin-3A receptor (α7/5-HT3A) subunits form functional BgtRs that are palmitoylated to an extent similar to that of BgtRα7 subunits in PC12 cells. Palmitoylation of PC12 and α7/5-HT3ABgtRs occurred during assembly in the endoplasmic reticulum (ER). In conclusion, our data indicate a function for protein palmitoylation in which palmitoylation of assembling α7 subunits in the ER has a role in the formation of functional BgtRs.