Regulation of Kv7.2/Kv7.3 channels by cholesterol: Relevance of an optimum plasma membrane cholesterol content.

Kv7.2/Kv7.3 channels are the molecular correlate of the M-current, which stabilizes the membrane potential and controls neuronal excitability. Previous studies have shown the relevance of plasma membrane lipids on both M-currents and Kv7.2/Kv7.3 channels. Here, we report the sensitive modulation of Kv7.2/Kv7.3 channels by membrane cholesterol level. Kv7.2/Kv7.3 channels transiently expressed in HEK-293 cells were significantly inhibited by decreasing the cholesterol level in the plasma membrane by three different pharmacological strategies: methyl-β-cyclodextrin (MβCD), Filipin III, and cholesterol oxidase treatment. Surprisingly, Kv7.2/Kv7.3 channels were also inhibited by membrane cholesterol loading with the MβCD/cholesterol complex. Depletion or enrichment of plasma membrane cholesterol differentially affected the biophysical parameters of the macroscopic Kv7.2/Kv7.3 currents. These results indicate a complex mechanism of Kv7.2/Kv7.3 channels modulation by membrane cholesterol. We propose that inhibition of Kv7.2/Kv7.3 channels by membrane cholesterol depletion involves a loss of a direct cholesterol-channel interaction. However, the inhibition of Kv7.2/Kv7.3 channels by membrane cholesterol enrichment could include an additional direct cholesterol-channel interaction, or changes in the physical properties of the plasma membrane. In summary, our results indicate that an optimum cholesterol level in the plasma membrane is required for the proper functioning of Kv7.2/Kv7.3 channels.