Pharmacological Characterisation of Nicotinic Acetylcholine Receptors Expressed in Human iPSC-Derived Neurons

Neurons derived from human induced pluripotent stem cells (iPSCs) represent a potentially valuable tool for the characterisation of neuronal receptors and ion channels. Previous studies on iPSC-derived neuronal cells have reported the functional characterisation of a variety of receptors and ion channels, including glutamate receptors, gamma-aminobutyric acid (GABA) receptors and several voltage-gated ion channels. In the present study we have examined the expression and functional properties of nicotinic acetylcholine receptors (nAChRs) in human iPSC-derived neurons. Gene expression analysis indicated the presence of transcripts encoding several nAChR subunits, with highest levels detected for alpha 3-alpha 7, beta 1, beta 2 and beta 4 subunits (encoded by CHRNA3-CHRNA7, CHRNB1, CHRNB2 and CHRNB4 genes). In addition, similarly high transcript levels were detected for the truncated dupa7 subunit transcript, encoded by the partially duplicated gene CHRFAM7A, which has been associated with psychiatric disorders such as schizophrenia. The functional properties of these nAChRs have been examined by calcium fluorescence and by patch-clamp recordings. The data obtained suggest that the majority of functional nAChRs expressed in these cells have pharmacological properties typical of alpha 7 receptors. Large responses were induced by a selective alpha 7 agonist (compound B), in the presence of the alpha 7-selective positive allosteric modulator (PAM) PNU-120596, which were blocked by the alpha 7-selective antagonist methyllycaconitine (MLA). In addition, a small proportion of the neurons express nAChRs with properties typical of heteromeric (non-alpha 7 containing) nAChR subtypes. These cells therefore represent a great tool to advance our understanding of the properties of native human nAChRs, alpha 7 in particular.