Phosphatidic acid modulation of Kv channel voltage sensor function

Membrane phospholipids can function as potent regulators of ion channel function. This study uncovers and investigates the effect of phosphatidic acid on Kv channel gating. Using the method of reconstitution into planar lipid bilayers, in which all protein and lipid components are defined and controlled, we characterize two distinct effects of phosphatidic acid. The first is a non-specific electrostatic influence on the midpoint of the gating activation curve mediated by electric charge density on the extracellular and intracellular membrane surfaces. The second effect is specific to the presence of a primary phosphate group and acts only through the intracellular membrane leaflet. The specific effect depends on the presence of a particular arginine residue in the voltage sensor. Phosphatidic acid at the intracellular surface accounts for a nearly 50 mV shift in the midpoint of the activation curve in a direction consistent with stabilization of the voltage sensor's closed conformation. These findings support a novel mechanism of voltage sensor regulation by the signaling lipid phosphatidic acid.