A Modular Heat-Sensing Domain Activates K2P2.1 through a Heat-Insensitive Gate

Abstract

Ion channels often have modular structure with dedicated gating and sensory domains. Ligand binding to a localized site in the sensory domain usually affects channel function through allosteric effects on the gate. It is not clear whether this paradigm is applicable to ion channels regulated by temperature. Indeed, temperature may have an effect on the whole channel structure and thus, bypass the need for a dedicated heat-sensing domain. Heat leads to activation of the ‘leak’ two-pore (K2P) potassium channel K2P2.1 (KCNK2/TREK-1) through opening of a selectivity filter-based outer gate in the extracellular pore domain. We sought to investigate whether the pore plays a role in sensing heat or whether it only functions as a gate that responds to the commands from the temperature-sensing elements located elsewhere in the channel. We found that the incorporation of mutations designed to prevent allosteric communication between the intracellular C-terminal domain and the pore domain of K2P2.1 resulted in channels that remain functional but fail to respond to temperature. These results indicate that the gating mechanism of the pore lacks intrinsic temperature sensitivity and that the heat-sensing elements of K2P2.1 are confined within its C-terminus. Our data provide experimental support for the general notion of the existence of modular temperature sensing domains and highlight functional distinction between gating and sensory elements in heat-sensitive ion channels.