Henderson_2014_J.Gen.Physiol_143_51

Chronic exposure to nicotine up-regulates high sensitivity nicotinic acetylcholine receptors (nAChRs) in the brain. This up-regulation partially underlies addiction and may also contribute to protection against Parkinson's disease. nAChRs containing the alpha6 subunit (alpha6* nAChRs) are expressed in neurons in several brain regions, but comparatively little is known about the effect of chronic nicotine on these nAChRs. We report here that nicotine up-regulates alpha6* nAChRs in several mouse brain regions (substantia nigra pars compacta, ventral tegmental area, medial habenula, and superior colliculus) and in neuroblastoma 2a cells. We present evidence that a coat protein complex I (COPI)-mediated process mediates this up-regulation of alpha6* or alpha4* nAChRs but does not participate in basal trafficking. We show that alpha6beta2beta3 nAChR up-regulation is prevented by mutating a putative COPI-binding motif in the beta3 subunit or by inhibiting COPI. Similarly, a COPI-dependent process is required for up-regulation of alpha4beta2 nAChRs by chronic nicotine but not for basal trafficking. Mutation of the putative COPI-binding motif or inhibition of COPI also results in reduced normalized Forster resonance energy transfer between alpha6beta2beta3 nAChRs and epsilonCOP subunits. The discovery that nicotine exploits a COPI-dependent process to chaperone high sensitivity nAChRs is novel and suggests that this may be a common mechanism in the up-regulation of nAChRs in response to chronic nicotine.