K(2P)2.1(TREK-1):activator complexes reveal a cryptic selectivity filter binding site

Polymodal K(2P) (KCNK) thermo- and mechanosensitive TREK(1) potassium channels, generate ‘leak’ currents that regulate neuronal excitability, respond to lipids, temperature, and mechanical stretch, and influence pain, temperature perception, and anesthetic responses(1–3). These dimeric voltage-gated ion channel (VGIC) superfamily members have a unique topology comprising two pore forming regions per subunit(4–6). Contrasting other potassium channels, K(2P)s use a selectivity filter ‘C-type’ gate(7–10) as the principal gating site. Despite recent advances(3,11,12), K(2P)s suffer from a poor pharmacologic profile limiting mechanistic and biological studies. Here, we describe a new small molecule TREK activator class that directly stimulates the C-type gate by acting as molecular wedges that restrict interdomain interface movement behind the selectivity filter. Structures of K(2P)2.1(TREK-1) alone with two selective K(2P)2.1(TREK-1) and K(2P)10.1(TREK-2) activators, an N-aryl-sulfonamide, ML335, and a thiophene-carboxamide, ML402, define a cryptic binding pocket unlike other ion channel small molecule binding sites and, together with functional studies, identify a cation-π interaction that controls selectivity. Together, our data unveil a previously unknown, druggable K(2P) site that stabilizes the C-type gate ‘leak mode’ and provide direct evidence for K(2P) selectivity filter gating.