Thermosensitivity of TREK K2P channels is controlled by a PKA switch and depends on the microtubular network

Abstract

Temperature sensing is an essential component of animal perception and enables individuals to avoid painful or lethal temperatures. Many temperature sensors in central and peripheral neurons are ion channels. Here, we focus on the thermosensitive TREK/TRAAK subfamily of K2P channels - the only known K+ selective thermosensitive channels. The C-terminal domain is essential for the temperature activation of TREK channels, but the mechanism of temperature sensation and the nature of the temperature sensor are unknown. We studied the thermosensitivity of representatives of all K2P channel subfamilies and identified TREK-1 and TREK-2 as the only thermosensitive K2P channels, while TRAAK, the third member of the mechano-gated subfamily, showed no temperature dependence. We transferred the thermosensitivity of TREK-1 to TRAAK channels by exchanging the C-termini, demonstrating that the C-terminal domain is sufficient to confer thermosensitivity. By gradually truncating the C-terminus, we isolated a specific temperature responsive element (TRE) consisting of 18 amino acids that constitutes a unique feature in mammalian thermosensitive channels. Within this TRE lie both the binding domain for microtubule associated protein 2 (MAP2) and the PKA phosphorylation site. Pharmacological disruption of the microtubular network as well as the loss of the MAP2 binding site suppressed the temperature response, and PKA activation completely abolished temperature sensitivity. Thus, the connection to the microtubular network enables the thermosensitivity of TREK channels, which is not intrinsic to the channel itself, while the PKA-mediated phosphorylation status acts as a switch that determines if TREK channels are thermosensitive at all.