Extracellular modulation of TREK-2 activity with nanobodies provides insights into the mechanism of K2P channel regulation

Potassium channels of the Two-Pore Domain (K2P) subfamily, KCNK1-KCNK18, play crucial roles in controlling the electrical activity of many different cell types and represent attractive therapeutic targets. However, the identification of highly selective small molecule drugs against these channels has been challenging due to the high degree of structural and functional conservation that exists not only between K2P channels, but across the whole K+ channel superfamily. To address the issue of selectivity, we generated camelid antibody fragments (nanobodies) against the TREK-2 (KCNK10) K2P K+ channel and identified selective binders including several that directly modulate channel activity. Crystal structures of these nanobodies in complex with TREK-2 also reveal insights into their mechanisms of activation and inhibition via binding to the extracellular loops and Cap domain, as well as their suitability for immunodetection. These tools therefore provide important insights into TREK channel gating and a more selective approach to the modulation of K2P channel activity via their extracellular domains. ### Competing Interest Statement The authors have declared no competing interest.