The novel immunosuppressant Cloxyquin activates hTRESK by allosteric modulation of the selectivity filter

Abstract The TWIK-related spinal cord K+ channel (TRESK) is a K2P channel contributing to the maintenance of membrane potentials in various cells. Recently, physiological TRESK function was identified as a key player in T-cell differentiation rendering the channel a new pharmacological target for treatment of autoimmune diseases. The channel activator cloxyquin represents a promising lead compound for the development of a new class of immunomodulators. Identification of cloxyquin binding site and characterization of the molecular mechanism causing the agonism can foster the future drug development. Here, we identified the cloxyquin binding site at the M2/M4 interface by mutational scan and analyzed the molecular mechanism of action by protein modelling as well as in silico and in vitro electrophysiology using different permeating ion species (K+ / Rb+). In combination with kinetic analyses of channel inactivation, we show that cloxyquin allosterically stabilizes the inner selectivity filter facilitating the conduction process subsequently activating hTRESK.