Dataset Information

Human ?4?2 nicotinic acetylcholine receptor as a novel target of oligomeric ?-synuclein.

ABSTRACT: Cigarette smoking is associated with a decreased incidence of Parkinson disease (PD) through unknown mechanisms. Interestingly, a decrease in the numbers of ?4?2 nicotinic acetylcholine receptors (?4?2-nAChRs) in PD patients suggests an ?4?2-nAChR-mediated cholinergic deficit in PD. Although oligomeric forms of ?-synuclein have been recognized to be toxic and involved in the pathogenesis of PD, their direct effects on nAChR-mediated cholinergic signaling remains undefined. Here, we report for the first time that oligomeric ?-synuclein selectively inhibits human ?4?2-nAChR-mediated currents in a dose-dependent, non-competitive and use-independent manner. We show that pre-loading cells with guanyl-5'-yl thiophosphate fails to prevent this inhibition, suggesting that the ?-synuclein-induced inhibition of ?4?2-nAChR function is not mediated by nAChR internalization. By using a pharmacological approach and cultures expressing transfected human nAChRs, we have shown a clear effect of oligomeric ?-synuclein on ?4?2-nAChRs, but not on ?4?4- or ?7-nAChRs, suggesting nAChR subunit selectivity of oligomeric ?-synuclein-induced inhibition. In addition, by combining the size exclusion chromatography and atomic force microscopy (AFM) analyses, we find that only large (>4 nm) oligomeric ?-synuclein aggregates (but not monomeric, small oligomeric or fibrillar ?-synuclein aggregates) exhibit the inhibitory effect on human ?4?2-nAChRs. Collectively, we have provided direct evidence that ?4?2-nAChR is a sensitive target to mediate oligomeric ?-synuclein-induced modulation of cholinergic signaling, and our data imply that therapeutic strategies targeted toward ?4?2-nAChRs may have potential for developing new treatments for PD.

SUBMITTER: Liu Q

PROVIDER: S-EPMC3577813 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Human α4β2 nicotinic acetylcholine receptor as a novel target of oligomeric α-synuclein.

Liu Qiang Q Emadi Sharareh S Shen Jian-Xin JX Sierks Michael R MR Wu Jie J

PloS one 20130220 2

Cigarette smoking is associated with a decreased incidence of Parkinson disease (PD) through unknown mechanisms. Interestingly, a decrease in the numbers of α4β2 nicotinic acetylcholine receptors (α4β2-nAChRs) in PD patients suggests an α4β2-nAChR-mediated cholinergic deficit in PD. Although oligomeric forms of α-synuclein have been recognized to be toxic and involved in the pathogenesis of PD, their direct effects on nAChR-mediated cholinergic signaling remains undefined. Here, we report for th ...[more]

PMID: 23437071

Similar Datasets

Project description:The neuronal alpha4beta2 nicotinic acetylcholine receptor (nAChR) is one of the most widely expressed nAChR subtypes in the brain. Its subunits have high sequence identity (54 and 46% for alpha4 and beta2, respectively) with alpha and beta subunits in Torpedo nAChR. Using the known structure of the Torpedo nAChR as a template, the closed-channel structure of the alpha4beta2 nAChR was constructed through homology modeling. Normal-mode analysis was performed on this closed structure and the resulting lowest frequency mode was applied to it for a "twist-to-open" motion, which increased the minimum pore radius from 2.7 to 3.4 A and generated an open-channel model. Nicotine could bind to the predicted agonist binding sites in the open-channel model but not in the closed one. Both models were subsequently equilibrated in a ternary lipid mixture via extensive molecular dynamics (MD) simulations. Over the course of 11 ns MD simulations, the open channel remained open with filled water, but the closed channel showed a much lower water density at its hydrophobic gate comprised of residues alpha4-V259 and alpha4-L263 and their homologous residues in the beta2 subunits. Brownian dynamics simulations of Na+ permeation through the open channel demonstrated a current-voltage relationship that was consistent with experimental data on the conducting state of alpha4beta2 nAChR. Besides establishment of the well-equilibrated closed- and open-channel alpha4beta2 structural models, the MD simulations on these models provided valuable insights into critical factors that potentially modulate channel gating. Rotation and tilting of TM2 helices led to changes in orientations of pore-lining residue side chains. Without concerted movement, the reorientation of one or two hydrophobic side chains could be enough for channel opening. The closed- and open-channel structures exhibited distinct patterns of electrostatic interactions at the interface of extracellular and transmembrane domains that might regulate the signal propagation of agonist binding to channel opening. A potential prominent role of the beta2 subunit in channel gating was also elucidated in the study.

Project description:We and others have shown that one of the mechanisms of growth regulation of small cell lung cancer cell lines and cultured pulmonary neuroendocrine cells is by the binding of agonists to the alpha7 neuronal nicotinic acetylcholine receptor. In addition, we have shown that the nicotine-derived carcinogenic nitrosamine, 4(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is a high affinity agonist for the alpha7 nicotinic acetylcholine receptor. In the present study, our goal was to determine the extent of alpha7 mRNA and protein expression in the human lung.Experiments were done using reverse transcription polymerase chain reaction (RT-PCR), a nuclease protection assay and western blotting using membrane proteins.We detected mRNA for the neuronal nicotinic acetylcholine receptor alpha7 receptor in seven small cell lung cancer (SCLC) cell lines, in two pulmonary adenocarcinoma cell lines, in cultured normal human small airway epithelial cells (SAEC), one carcinoid cell line, three squamous cell lines and tissue samples from nine patients with various types of lung cancer. A nuclease protection assay showed prominent levels of alpha7 in the NCI-H82 SCLC cell line while alpha7 was not detected in SAEC, suggesting that alpha7 mRNA levels may be higher in SCLC compared to normal cells. Using a specific antibody to the alpha7 nicotinic receptor, protein expression of alpha7 was determined. All SCLC cell lines except NCI-H187 expressed protein for the alpha7 receptor. In the non-SCLC cells and normal cells that express the alpha7 nAChR mRNA, only in SAEC, A549 and NCI-H226 was expression of the alpha7 nicotinic receptor protein shown. When NCI-H69 SCLC cell line was exposed to 100 pm NNK, protein expression of the alpha7 receptor was increased at 60 and 150 min.Expression of mRNA for the neuronal nicotinic acetylcholine receptor alpha7 seems to be ubiquitously expressed in all human lung cancer cell lines tested (except for NCI-H441) as well as normal lung cells. The alpha7 nicotinic receptor protein is expressed in fewer cell lines, and the tobacco carcinogen NNK increases alpha7 nicotinic receptor protein levels.

Dataset Information

Human ?4?2 nicotinic acetylcholine receptor as a novel target of oligomeric ?-synuclein.

Publications

Human α4β2 nicotinic acetylcholine receptor as a novel target of oligomeric α-synuclein.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets