Synergistic interplay of Gβγ and phosphatidylinositol 4,5-bisphosphate dictates Kv7.4 channel activity

Kv7.4 channels are key determinants of arterial contractility and cochlear mechanosensation that, like all Kv7 channels, have an obligatory requirement for phosphatidylinositol 4,5-bisphosphate (PIP2). beta gamma G proteins (G beta gamma) have been identified as novel positive regulators of Kv7.4. The present study ascertained whether G beta gamma increased Kv7.4 open probability through an increased sensitivity to PIP2. In HEK cells stably expressing Kv7.4, PIP2 or G beta gamma increased open probability in a concentration dependent manner. Depleting PIP2 prevented any G beta gamma-mediated stimulation whilst an array of G beta gamma inhibitors prohibited any PIP2-induced current enhancement. A combination of PIP2 and G beta gamma at sub-efficacious concentrations increased channel open probability considerably. The stimulatory effects of three Kv7.2-7.5 channel activators were also lost by PIP2 depletion or G beta gamma inhibitors. This study alters substantially our understanding of the fundamental processes that dictate Kv7.4 activity, revealing a more complex and subtle paradigm where the reliance on local phosphoinositide is dictated by interaction with G beta gamma.