Oxidative modification of M-type K+ channels as a mechanism of cytoprotective neuronal silencing

Abstract

Voltage-gated K þ channels of the Kv7 family underlie the neuronal M current that regulates action potential firing. Suppression of M current increases excitability and its enhancement can silence neurons. We here show that three of five Kv7 channels undergo strong enhancement of their activity by oxidative modification induced by physiological concentrations of hydrogen peroxide. A triple cysteine pocket in the channel S2-S3 linker is critical for this effect. Oxidation-induced enhancement of M current produced a hyperpolarization and a dramatic reduction of action potential firing frequency in rat sympathetic neurons. As hydrogen peroxide is robustly produced during hypoxia-induced oxidative stress, we used an oxygen/glucose deprivation neurodegeneration model that showed neuronal death to be severely accelerated by M current blockade. Such blockade had no effect on survival of normoxic neurons. This work describes a novel pathway of M-channel regulation and suggests a role for M channels in protective neuronal silencing during oxidative stress.

GABAB receptors inhibit low-voltage activated and high-voltage activated Ca2+ channels in sensory neurons via distinct mechanisms

“…Thus, we have shown, that acting via a PTX-sensitive mechanism, NK1 receptors stimulated release of reactive oxygen species (ROS) from mitochondria of DRG neurons and these ROS induced oxidative modification of the Kv7 channels thus potentiating their activity [26]. Indeed, Kv7 channels are highly sensitive to oxidation by ROS due to the specific cysteine pocket in the intracellular S2-S3 linker of the channel [27,28]. Interestingly, T-type Ca 2+ channels are also sensitive to redox modulation, albeit in contrast to Kv7 channels, oxidizing compounds and ROS do not activate but inhibit T-type channel activity [21,29,30].…”

“…Since ROS generation by NK1 receptor triggering was sensitive to PTX [26] we hypothesized that unconventional signaling cascade causing inhibition of LVA current in DRG neurons by baclofen may also be mediated by a ROSdependent mechanism. Reducing agent DTT has been used to reverse oxidative modification of Kv7 channels [26,27]. Therefore we tested if DTT can also reverse baclofen-induced inhibition of LVA VGCC in DRG neurons.…”

Protective Role of Kv7 Channels in Oxygen and Glucose Deprivation-Induced Damage in Rat Caudate Brain Slices

“…Previous studies have shown that retigabine was neuroprotective in hippocampal slices, possibly because of its antioxidant activity. 15,16 Although different brain regions have been investigated, the efficacy of ICA27243, as well as the reversal of retigabine effects by linopirdine, suggests a neuroprotection mediated by M-current activation. The neuroprotective effects of retigabine are further corroborated by the results of our experiments using a different trigger for brain damage.…”

Reactive oxygen species are second messengers of neurokinin signaling in peripheral sensory neurons

“…These data suggest that M-current augmentation produced by SP is mediated by a mechanism similar to that produced by external application of H 2 O 2 . Oxidation of Kv7.2/7.3 channels overexpressed in CHO cells with H 2 O 2 was shown to produce an acceleration of channel activation and a modest slowing of deactivation kinetics (24,25). In DRG neurons the kinetics of M current was difficult to analyze because of contamination with other voltage-gated conductances.…”

“…H 2 O 2 oxidizes a triplet of cysteines in the cytosolic S2-S3 linker of Kv7 channels, an effect reversed by the reducing agent DTT (24). We therefore tested if DTT (1 mM) would reverse the M-current augmentation by SP, and indeed it did so ( Fig.…”