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 (PIP2). 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 Ca2+ was clamped or Ca2+ 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 PIP2 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 microM), suggesting that PIP2 re-synthesis is required for current recovery. High-performance liquid chromatographic analysis of anionic phospholipids in CHO cells stably expressing AT1 receptors revealed that PIP2 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.
Zaika
Oleg
O
Department of Physiology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
Lara
Lucienne S
LS
Gamper
Nikita
N
Hilgemann
Donald W
DW
Jaffe
David B
DB
Shapiro
Mark S
MS
D000200:Action Potentials; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015640:Ion Channel Gating; D051658:KCNQ2 Potassium Channel / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051659:KCNQ3 Potassium Channel / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008959:Models, Neurological; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010742:Phospholipid Ethers / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000187:drug effects* / Q000378:metabolism; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; D019269:Phosphatidylinositol 4,5-Diphosphate; D010742:Phospholipid Ethers; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; C026659:edelfosine; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D010738:Type C Phospholipases