From head to tail - Atomistic mechanism of long-range coupling from the cytosolic sensor domain to the selectivity filter in TREK K2P channels

Abstract

The two-pore domain potassium (K2P) channels TREK-1 and TREK-2 link neuronal excitability to a variety of stimuli including mechanical force, lipids, temperature and phosphorylation. This regulation involves the C-terminus as a polymodal stimulus sensor and the selectivity filter (SF) as channel gate. Using crystallographic up- and down-state structures of TREK-2 as a template for full atomistic molecular dynamics simulations, we reveal that the SF in down-state undergoes inactivation via conformational changes at the S1 ion coordination site, while the up-state structure maintains a stable and conductive SF. This provides an atomistic understanding of the low channel activity previously assigned to the down state, but not evident from the crystal structure. Furthermore, by using (de-)phosphorylation mimics and chemically attaching lipid tethers to the proximal C-terminus (pCt), we confirm the hypothesis that moving the pCt towards the membrane induces the up-state. We also uncover two gating pathways by which movement of the pCt controls the stability (i.e. conductivity) of the filter gate. Together, these findings provide atomistic insights into the SF gating mechanism and the physiological regulation of TREK channels by phosphorylation.