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Pharmacological and functional comparisons of α6/α3β2β3-nAChRs and α4β2-nAChRs heterologously expressed in the human epithelial SH-EP1 cell line

Acta Pharmacologica Sinicavolume 39pages15711581 (2018) | Download Citation

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Abstract

Neuronal nicotinic acetylcholine receptors containing α6 subunits (α6*-nAChRs) show highly restricted distribution in midbrain neurons associated with pleasure, reward, and mood control, suggesting an important impact of α6*-nAChRs in modulating mesolimbic functions. However, the function and pharmacology of α6*-nAChRs remain poorly understood because of the lack of selective agonists for α6*-nAChRs and the challenging heterologous expression of functional α6*-nAChRs in mammalian cell lines. In particular, the α6 subunit is commonly co-expressed with α4*-nAChRs in the midbrain, which masks α6*-nAChR (without α4) function and pharmacology. In this study, we systematically profiled the pharmacology and function of α6*-nAChRs and compared these properties with those of α4β2 nAChRs expressed in the same cell line. Heterologously expressed human α6/α3 chimeric subunits (α6 N-terminal domain joined with α3 trans-membrane domains and intracellular loops) with β2 and β3 subunits in the human SH-EP1 cell line (α6*-nAChRs) were used. Patch-clamp whole-cell recordings were performed to measure these receptor-mediated currents. Functionally, the heterologously expressed α6*-nAChRs exhibited excellent function and showed distinct nicotine-induced current responses, such as kinetics, inward rectification and recovery from desensitization, compared with α4β2-nAChRs. Pharmacologically, α6*-nAChR was highly sensitive to the α6 subunit-selective antagonist α-conotoxin MII but had lower sensitivity to mecamylamine and dihydro-β-erythroidine. Nicotine and acetylcholine were found to be full agonists for α6*-nAChRs, whereas epibatidine and cytisine were determined to be partial agonists. Heterologously expressed α6*-nAChRs exhibited pharmacology and function distinct from those of α4β2-nAChRs, suggesting that α6*-nAChRs may mediate different cholinergic signals. Our α6*-nAChR expression system can be used as an excellent cell model for future investigations of α6*-nAChR function and pharmacology.

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Work toward this project was supported by NIH R01 DA035958, NIH R21 DA026627, NIH R01 GM103801, P01 GM48677, R01 DA042749, Barrow Neuroscience Foundation, Philips Morris External Research Grant, and Special Innovation Project of Education Department of Guangdong Province. Production of the α6/3β2β3-nAChR cell line was sponsored by Targacept.

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Author notes

  1. These authors contributed equally to this work.

Affiliations

  1. Department of Neurology, Yunfu People’s Hospital, Yunfu, 527300, China

    • De-jie Chen
    • , Yuan-bing Huang
    • , Quang-xi Su
    •  & Jie Wu
  2. Department of Neurobiology, Barrow Neurological Institute, St Joseph’s Hospital and Medical Center, Phoenix, AZ, 85013, USA

    • De-jie Chen
    • , Fen-fei Gao
    • , Xiao-kuang Ma
    • , Yuan-bing Huang
    • , Ming Gao
    • , Turner Dharshaun
    • , Jason Brek Eaton
    • , Yong-chang Chang
    • , Ronald J Lukas
    • , Paul Whiteaker
    •  & Jie Wu
  3. Department of Pharmacology, Shantou University Medical College, Shantou, 515063, China

    • Fen-fei Gao
    • , Xiao-kuang Ma
    • , Gang-gang Shi
    •  & Jie Wu
  4. Departments of Psychology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA

    • Sterling Sudweeks
  5. George E Wahlen Veterans Affairs Medical Center, Salt Lake City, UT, 84108, USA

    • J Michael Mcintosh
  6. Departments of Psychiatry and Biology, University of Utah, Salt Lake City, UT, 84112, USA

    • J Michael Mcintosh
  7. Department of Physiology and Neuroscience, Brigham Young University, Provo, UT, 84602, USA

    • Scott C Steffensen

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Correspondence to Jie Wu.

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https://doi.org/10.1038/aps.2017.209