Acetylcholine receptors (AChRs) are members of a superfamily of proteins called pentameric ligand-gated ion channels, which are found in almost all forms of life and thus have a rich evolutionary history. Muscle-type AChRs are heteropentameric complexes assembled from four related subunits (α, β, δ, and ɛ). Here we reconstruct the amino acid sequence of a β subunit ancestor shared by humans and cartilaginous fishes (i.e., Torpedo). Then, by resurrecting this ancestral β subunit and co-expressing it with human α, δ, and ɛ subunits, we show that despite 132 substitutions, the ancestral subunit is capable of forming human/ancestral hybrid AChRs. Whole-cell currents demonstrate that the agonist acetylcholine has reduced potency for hybrid receptors, while single-channel recordings reveal that hybrid receptors display reduced conductance and open probability. Our results outline a promising strategy for studies of AChR evolution aimed at identifying the amino acid origins of AChR structure and function.

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Recently, a couple of giga-seal automated patch clamp (APC) platforms in a standard 384-well plate format have been introduced. These APC instruments can deliver higher throughput measurements with high-quality data for ion channel drug discovery. In this study, we developed an automated electrophysiology assay for the voltage-gated potassium channel, Kv1.3 as a test case on the Nanion SyncroPatch 384PE, one of the latest APC platforms. We achieved a high cell-catch rate (98% wells/plate, defined by membrane resistance >16 MU/cell) by screening plate types (number of holes and resistance), and obtained a stable seal (87% wells/plate, defined by initial/final seal resistance >500 MU/cell) by optimizing recording solutions. We generated data at an overall success rate (defined by initial peak current >300 pA/cell, initial/final seal resistance >500 MU/cell, and current stability <57% change/min) of 79% on average. Using the same platform, we validated a dose-response assay using clotrimazole, a potent Kv1.3 inhibitor. The assay was robust with Z' factor 0.52 and the success rate 75%. Altogether, our results demonstrated that the SyncroPatch represents a reliable platform for voltage-gated potassium channel assays.