Abstract
Polyunsaturated fatty acid (PUFA) lipids modulate the neuronal and microglial leak potassium channel K(2P)13.1 (THIK1) and other voltage-gated ion channel (VGIC) superfamily members through poorly understood mechanisms. Here we present cryo-electron microscopy structures of human THIK1 and mutants, revealing a unique two-chamber aqueous inner cavity obstructed by a hydrophilic barrier important for gating, the flow restrictor, and a P1-M4 intersubunit interface lipid at a site, the PUFA site, corresponding to the K(2P) small-molecule modulator pocket. This overlap, together with functional studies, indicates that PUFA site lipids are THIK1 cofactors. Comparison with a PUFA-responsive VGIC, K(v)7.1, reveals a shared modulatory role for the pore domain intersubunit interface, providing a framework for understanding PUFA action on the VGIC superfamily. Our findings reveal the distinct THIK1 architecture, highlight the importance of the P1-M4 interface for K(2P) control by natural and synthetic ligands and should aid in the development of THIK subfamily modulators for neuroinflammation and autism.