Angiotensin II regulates neuronal excitability via phosphatidylinositol 4,5‐bisphosphate‐dependent modulation of Kv7 (M‐type) K + channels

Voltage‐gated Kv7 (KCNQ) channels underlie important K + currents in many different types of cells, including the neuronal M current, which is thought to be modulated by muscarinic stimulation via depletion of membrane phosphatidylinositol 4,5‐bisphosphate (PIP 2 ). We studied the role of modulation by angiotensin II (angioII) of M current in controlling discharge properties of superior cervical ganglion (SCG) sympathetic neurons and the mechanism of action of angioII on cloned Kv7 channels in a heterologous expression system. In SCG neurons, which endogenously express angioII AT1 receptors, application of angioII for 2 min produced an increase in neuronal excitability and a decrease in spike‐frequency adaptation that partially returned to control values after 10 min of angioII exposure. The increase in excitability could be simulated in a computational model by varying only the amount of M current. Using Chinese hamster ovary (CHO) cells expressing cloned Kv7.2 + 7.3 heteromultimers and AT1 receptors studied under perforated patch clamp, angioII induced a strong suppression of the Kv7.2/7.3 current that returned to near baseline within 10 min of stimulation. The suppression was blocked by the phospholipase C inhibitor edelfosine. Under whole‐cell clamp, angioII moderately suppressed the Kv7.2/7.3 current whether or not intracellular Ca 2+ was clamped or Ca 2+ stores depleted. Co‐expression of PI(4)5‐kinase in these cells sharply reduced angioII inhibition, but did not augment current amplitudes, whereas co‐expression of a PIP 2 5′‐phosphatase sharply reduced current amplitudes, and also blunted the inhibition. The rebound of the current seen in perforated‐patch recordings was blocked by the PI4‐kinase inhibitor, wortmannin (50 μ m ), suggesting that PIP 2 re‐synthesis is required for current recovery. High‐performance liquid chromatographic analysis of anionic phospholipids in CHO cells stably expressing AT1 receptors revealed that PIP 2 and phosphatidylinositol 4‐phosphate levels are to be strongly depleted after 2 min of stimulation with angioII, with a partial rebound after 10 min. The results of this study establish how angioII modulates M channels, which in turn affects the integrative properties of SCG neurons.