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This Article Full Text Full Text (PDF) All Versions of this Article: 586/2/545    most recent jphysiol.2007.143826v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wuttke, T. V. Articles by Jurkat-Rott, K. Search for Related Content PubMed PubMed Citation Articles by Wuttke, T. V. Articles by Jurkat-Rott, K. Related Collections Neuroscience

¹ Neurological Clinic, University of Ulm, Germany
² Institute of Anatomy, University of Ulm, Germany
³ Pediatric Hospital, Klinikum Augsburg, Germany
⁴ Institute of Applied Physiology, University of Ulm, Germany
⁵ Institute of Physiology I, University of Tübingen, Germany

The voltage-gated potassium channels K_V7.2 and K_V7.3 (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 K_V7.2. Electrophysiological investigations in Xenopus oocytes using two-microelectrode voltage clamping revealed that the steady-state activation curves for E119G alone and its coexpressions with K_V7.2 and/or K_V7.3 wild-type (WT) channels were significantly shifted in the depolarizing direction compared to K_V7.2 or K_V7.2/K_V7.3. 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 K_V7.2, and 33% for E119G/K_V7.3 compared to K_V7.2/K_V7.3 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 K_V7.2, a region that – according to molecular modelling – might interact with a positive charge in the S4 segment.

(Received 26 August 2007; accepted after revision 13 November 2007; first published online 15 November 2007)
Corresponding author K. Jurkat-Rott: Institute of Applied Physiology, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany. Email: karin.jurkat-rott{at}uni-ulm.de

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				S. Maljevic, T. V. Wuttke, and H. Lerche Nervous system KV7 disorders: breakdown of a subthreshold brake J. Physiol., April 1, 2008; 586(7): 1791 - 1801. [Abstract] [Full Text] [PDF]