An Intracellular Allosteric Modulator Binding Pocket in SK2 Ion Channels Is Shared by Multiple Chemotypes.Cho, L.T., Alexandrou, A.J., Torella, R., Knafels, J., Hobbs, J., Taylor, T., Loucif, A., Konopacka, A., Bell, S., Stevens, E.B., Pandit, J., Horst, R., Withka, J.M., Pryde, D.C., Liu, S., Young, G.T.
(2018) Structure 26: 533-544.e3
- PubMed: 29576321
- DOI: https://doi.org/10.1016/j.str.2018.02.017
- Primary Citation of Related Structures:
- PubMed Abstract:
Small conductance potassium (SK) ion channels define neuronal firing rates by conducting the after-hyperpolarization current. They are key targets in developing therapies where neuronal firing rates are dysfunctional, such as in epilepsy, Parkinson's, and amyotrophic lateral sclerosis (ALS). Here, we characterize a binding pocket situated at the intracellular interface of SK2 and calmodulin, which we show to be shared by multiple small-molecule chemotypes. Crystallization of this complex revealed that riluzole (approved for ALS) and an analog of the anti-ataxic agent (4-chloro-phenyl)-[2-(3,5-dimethyl-pyrazol-1-yl)-pyrimidin-4-yl]-amine (CyPPA) bind to and allosterically modulate via this site. Solution-state nuclear magnetic resonance demonstrates that riluzole, NS309, and CyPPA analogs bind at this bipartite pocket. We demonstrate, by patch-clamp electrophysiology, that both classes of ligand interact with overlapping but distinct residues within this pocket. These data define a clinically important site, laying the foundations for further studies of the mechanism of action of riluzole and related molecules.
Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK.