Retigabine, A Novel Anti-Convulsant, Enhances Activation of KCNQ2/Q3 Potassium Channels

Abstract

Retigabine [N-(2-amino-4-[fluorobenzylamino]-phenyl) carbamic acid; D-23129] is a novel anticonvulsant, unrelated to currently available antiepileptic agents, with activity in a broad range of seizure models. In the present study, we sought to determine whether retigabine could enhance current through M-like currents in PC12 cells and KCNQ2/Q3 K(+) channels expressed in Chinese hamster ovary cells (CHO-KCNQ2/Q3). In differentiated PC12 cells, retigabine enhanced a linopirdine-sensitive current. The effect of retigabine was associated with a slowing of M-like tail current deactivation in these cells. Retigabine (0.1 to 10 microM) induced a potassium current and hyperpolarized CHO cells expressing KCNQ2/Q3 cells but not in wild-type cells. Retigabine-induced currents in CHO-KCNQ2/Q3 cells were inhibited by 60.6 +/- 11% (n = 4) by the KCNQ2/Q3 blocker, linopirdine (10 microM), and 82.7 +/- 5.4% (n = 4) by BaCl(2) (10 mM). The mechanism by which retigabine enhanced KCNQ2/Q3 currents involved large, drug-induced, leftward shifts in the voltage dependence of channel activation (-33.1 +/- 2.6 mV, n = 4, by 10 microM retigabine). Retigabine shifted the voltage dependence of channel activation with an EC(50) value of 1.6 +/- 0.3 microM (slope factor was 1.2 +/- 0.1, n = 4 to 5 cells per concentration). Retigabine (0.1 to 10 microM) also slowed the rate of channel deactivation, predominantly by increasing the contribution of a slowly deactivating tail current component. Our findings identify KCNQ2/Q3 channels as a molecular target for retigabine and suggest that activation of KCNQ2/Q3 channels may be responsible for at least some of the anticonvulsant activity of this agent.

Atypical Gating Of M-Type Potassium Channels Conferred by Mutations in Uncharged Residues in the S4Region of KCNQ2 Causing Benign Familial Neonatal Convulsions

“…Individuals affected by BFNC typically display normal psychomotor development, although a higher incidence of various epileptic manifestations later in life has been reported (Ronen et al, 1993). In addition to its pathophysiological role in BFNC, I KM is emerging as a novel therapeutic target for CNS diseases; in fact, I KM activators such as retigabine and flupirtine (Main et al, 2000;Rundfeldt and Netzer, 2000;Wickenden et al, 2000;Martire et al, 2004) appear as promising therapeutic tools against epilepsy (Rostock et al, 1996), pain (Blackburn-Munro and Jensen, 2003; Passmore et al, 2003), anxiety (Korsgaard et al, 2005), dystonia (Richter et al, 2006), and neurodegenerative disorders (Otto et al, 2004;Boscia et al, 2006).…”

Ion Channels as Drug Targets in Central Nervous System Disorders

“…Retigabine, at concentration 0.1 -10 M, affected CHO cells expressing K V 7.2/K V 7.3 heteromeric channel (CHO-KNCQ2/Q3) resulting in increasing M-like potassium currents and hyperpolarization of the cell membrane. Moreover, it shifted the voltage dependence of channel activation with an EC 50 value of 1.6±0.3 M [103]. The compound also significantly influenced properties of Xenopus oocytes membrane expressing recombinant human K V 7.2/K V 7.3, as well as channel itself.…”

Targeted Resequencing of Epilepsy Genes: A Pharmaco-Therapeutic Perspective

“…Although retigabine can enhance GABAergic transmission and GABA-induced chloride currents, it mainly acts as enhancer of the neuronal M-type potassium current mediated by Kv7.2-Kv7.3 channels [124]. Probably by destabilization of channels closed conformation and enhancement of open channels probability, retigabine reduces and accelerates the threshold for activation of M-current, thus increasing the current amplitude at negative potentials [124][125][126].…”