Regulation of the two-pore domain potassium channel, THIK-1 and THIK-2, by G protein coupled receptors

Abstract

A member of THIK (two pore domain halothane-inhibited K+) channels, THIK-1, was reported as a target of Gi/o-coupled receptors (Gi/o-Rs) in neurons and microglia. We confirmed that in HEK293T cells the THIK-1 channel is activated by Gi/o-Rs and found that Gq-coupled receptors (Gq-Rs) also activates the channel. The effects of Gi/o-Rs and Gq-Rs were inhibited by the Gi/o inhibitor pertussis toxin and phospholipase C (PLC) inhibitor, respectively. The effects of Gi/o-Rs were attenuated when consensus Gβγ binding motif at the C-tail of the THIK-1 channel was mutated, suggesting that Gβγ serves as a THIK-1 channel activator upon the stimulation of Gi/o-Rs. As to the effects of Gq-Rs on the THIK-1 channel, a protein kinase C inhibitor and calcium chelators failed to inhibit the effect of a Gq coupled muscarinic M1R. Neither the hydrolysis of phosphatidyl inositol bisphosphate induced by voltage sensitive phosphatase nor the application of a diacylglycerol analogue, OAG, increased the channel current. The mediator of Gq-dependent activation of the THIK-1 channel remained unsolved. The effects of Gi/o- and Gq-Rs on the THIK-2 channel were also investigated, by using a THIK-2 mutant channel whose N-terminal domain is deleted to improve the surface membrane expression. We observed that Gi/o- and Gq-Rs activate the mutated THIK-2 channel, similarly to the THIK-1 channel. Interestingly, heterodimeric channels of THIK-1 and THIK-2 responded to Gi/o-R and Gq-R stimulation. Taken together, Gi/o- or Gq-Rs activates the THIK-1 and THIK-2 channels in a Gβγ or PLC dependent manner, respectively.

Higher-order thalamocortical projections selectively control excitability via NMDAR and mGluRI-mediated mechanisms

“…Second, activation of mGluRs in neocortex and hippocampus is known to modulate various K + channels [76][77][78][79][80][81] , although Ca 2+ and other channels can also be affected 82 . Third, signaling pathways from mGluRs to K2P channels have been identified using reduced expression systems 83,84 and in cerebellum granule cells 47,48,85 . K2P channels are responsible for leak and background currents, which are largely voltage-independent 86,87 .…”

CryoEM Structure of the human THIK-1 K2P K+Channel Reveals a Lower ‘Y-gate’ Regulated by Lipids and Anaesthetics

“…Recent studies have demonstrated that THIK-1 can be transiently activated by both G i/o and G q -coupled receptor pathways 16 , and can also be directly activated by anionic lipids such as PIP 2 and oleoyl-CoA 17 . In addition, THIK-1 exhibits direct inhibition by the phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthine (IBMX) 18 as well as several small molecule inhibitors currently being developed as therapeutics 10,12 .…”