THIK-1, a two-pore domain K⁺ (K2P) channel, plays important roles in microglia and macrophages. While previous reports have indicated that steroids, including cholesterol, estradiol, and progesterone, modulate several K⁺ channels, the effect of steroids on THIK-1 channels remained unknown. Working under the hypothesis that steroids might regulate THIK-1 channel function, the research group investigated this possibility.

In this study, researchers demonstrated that 17β-estradiol (10 μM) —a key female sex hormone—inhibits mouse THIK-1 by approximately 40%. Using docking simulations and target mutagenesis, the team identified possible estradiol-binding sites in THIK-1, which were subsequently tested by introducing alanine substitutions at residues located within or near these sites. The F142A, V269A, and Y273A mutations reduced estradiol-mediated inhibition. These residues lie in the upper cavity above the Y-gate of THIK-1, named as the pond, suggesting that the conformation of this region is critical for inhibition by estradiol.
 
Furthermore, when evaluating a human THIK-1 variant, the researchers observed that it was inhibited even at a low, physiological concentration of estradiol (10 nM).
 
In summary, the researchers revealed that estradiol-mediated inhibition of THIK-1 depends on residues in the pond region and may have physiological or pathological relevance for THIK-1 variants.