The chaperone protein 14-3-3η interacts with the nicotinic acetylcholine receptor α4 subunit -: Evidence for a dynamic role in subunit stabilization

By using the large cytoplasmic domain of the nicotinic acetylcholine receptor (AChR) alpha4 subunit as a bait in the yeast two-hybrid system, we isolated the first cytosolic protein, 14-3-3-eta, known to interact directly with neuronal AChRs. 14-3-3-eta is a member of a family of proteins that function as regulatory or chaperone/scaffolding/adaptor proteins. 14-3-3-eta interacted with the recombinant alpha4 subunit alone in tsA 201 cells following activation of cAMP-dependent protein kinase by forskolin. The interaction of 14-3-3-eta with recombinant alpha4 subunits was abolished when serine 441 of the alpha4 subunit was mutated to alanine (alpha4(S441A)). The surface levels of recombinant wild-type alpha4 beta2 AChRs were similar to2-fold higher than those of mutant alpha4(S441A)beta2 AChRs. The interaction significantly increased the steady state levels of the alpha4 subunit and alpha4 beta2 AChRs but not that of the mutant alpha4(S441A) subunit or mutant alpha4(S441A)beta2 AChRs. The EC50 values for activation by acetylcholine were not significantly different for alpha4 beta2 AChRs and alpha4(S441A)beta2 AChRs coexpressed with 14-3-3-eta in oocytes following treatment with forskolin. 14-3-3 coimmunopurified with native alpha4 AChRs from brain. These results support a role for 14-3-3 in dynamically regulating the expression levels of alpha4 beta2 AChRs through its interaction with the alpha4 subunit.