Key result
The E119G mutation in the KV7.2 channel shifted steady-state activation curves, reducing relative current amplitudes by about 45% at -50 mV compared to wild-type channels.
The E119G mutation in KV7.2 alters voltage-dependent activation at subthreshold voltages, explaining its role in benign familial neonatal convulsions.
The voltage-gated potassium channels KV7.2 and KV7.3 (genes KCNQ2 and KCNQ3) constitute a major component of the M-current controlling the firing rate in many neurons. Mutations within these two channel subunits cause benign familial neonatal convulsions (BFNC). Here we identified a novel BFNC-causing mutation (E119G) in the S1-S2 region of KV7.2. Electrophysiological investigations in Xenopus oocytes using two-microelectrode voltage clamping revealed that the steady-state activation curves for E119G alone and its coexpressions with KV7.2 and/or KV7.3 wild-type (WT) channels were significantly shifted in the depolarizing direction compared to KV7.2 or KV7.2/KV7.3. These shifts reduced the relative current amplitudes for mutant channels particularly in the subthreshold range of an action potential (about 45% reduction at --50 mV for E119G compared to KV7.2, and 33% for E119G/KV7.3 compared to KV7.2/KV7.3 channels). Activation kinetics were significantly slowed for mutant channels. Our results indicate that small changes in channel gating at subthreshold voltages are sufficient to cause neonatal seizures and demonstrate the importance of the M-current for this voltage range. This was confirmed by a computer model predicting an increased burst duration for the mutation. On a molecular level, these results reveal a critical role in voltage sensing of the negatively charged E119 in S1-S2 of KV7.2, a region that-- according to molecular modelling - might interact with a positive charge in the S4 segment.
No takes yet. Share an insight, caveat, or question.
Wuttke et al. (2007) studied Benign familial neonatal convulsions (BFNC). E119G mutation in KV7.2 vs. KV7.2 or KV7.2/KV7.3 wild-type channels was evaluated on Relative current amplitudes at -50 mV (45% reduction). The E119G mutation in the KV7.2 channel shifted steady-state activation curves, reducing relative current amplitudes by about 45% at -50 mV compared to wild-type channels.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: