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

PLoS One. 2013;8(2):e55886. doi: 10.1371/journal.pone.0055886. Epub 2013 Feb 20.

Abstract

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 the first time that oligomeric α-synuclein selectively inhibits human α4β2-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 α-synuclein-induced inhibition of α4β2-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 α-synuclein on α4β2-nAChRs, but not on α4β4- or α7-nAChRs, suggesting nAChR subunit selectivity of oligomeric α-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 α-synuclein aggregates (but not monomeric, small oligomeric or fibrillar α-synuclein aggregates) exhibit the inhibitory effect on human α4β2-nAChRs. Collectively, we have provided direct evidence that α4β2-nAChR is a sensitive target to mediate oligomeric α-synuclein-induced modulation of cholinergic signaling, and our data imply that therapeutic strategies targeted toward α4β2-nAChRs may have potential for developing new treatments for PD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Gel
  • Endocytosis
  • Humans
  • Ion Channel Gating
  • Protein Multimerization*
  • Protein Structure, Quaternary
  • Receptors, Nicotinic / metabolism*
  • alpha-Synuclein / chemistry*
  • alpha-Synuclein / metabolism*

Substances

  • Receptors, Nicotinic
  • SNCA protein, human
  • alpha-Synuclein
  • nicotinic receptor alpha4beta2
  • nicotinic receptor beta2

Grants and funding

This work was supported by grants from the Michael J. Fox Foundation and the Arizona Biomedical Research Commission. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.