HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) 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 Mitrovic, N Articles by Lehmann-Horn, F Search for Related Content PubMed PubMed Citation Articles by Mitrovic, N Articles by Lehmann-Horn, F

N Mitrovi, A L George, Jr, H Lerche, S Wagner, C Fahlke and F Lehmann-Horn

Department of Applied Physiology, University of Ulm, Germany.

1. Three mutations at the same site in the inactivation gate of the alpha-subunit of the human muscle Na+ channel, G1306E, G1306V and G1306A, cause three phenotypes of K(+)-aggravated myotonia: G1306E as the most severe and G1306A as the most benign form. 2. Recombinant wildtype (WT) and mutant (G1306E, G1306V and G1306A) human Na+ channels were expressed in human embryonic kidney cells (HEK293). G1306E and G1306V channels showed a distinct increase in the time constants of inactivation (tau h1 and tau h2) and in the ratios of steady-state to peak currents (Iss/Ipeak) (e.g. at 0 mV, G1306E vs. WT; tau h1, 1.29 +/- 0.10 vs. 0.52 +/- 0.01 ms; Iss/Ipeak, 2.90 +/- 0.40 vs. 0.93 +/- 0.19%). G1306A channels showed only an increase in tau h1 (0.74 +/- 0.07 ms). For G1306E and G1306V channels, the steady-state inactivation curves, as well as the voltage dependence of the rate of recovery from inactivation, were shifted by +15 mV. For G1306A the h infinity curve was shifted by only +5 mV. 3. G1306E and G1306V channels showed prolonged current rise times and later first openings suggesting slowing of activation. For G1306E channels only, the steady-state activation curve was shifted by -7 mV. For all mutants the deactivation time constants were increased. 4. We conclude that (i) the combination of alterations in inactivation and activation produces the slowing of the current decay, (ii) the slowed inactivation is most responsible for myotonia, and (iii) the shift of the steady-state activation curve, seen only with G1306E channels, may explain the severity of this phenotype. 5. The results suggest that two of the mutations in the Na+ channel inactivation gate also alter channel activation and deactivation.

This article has been cited by other articles:

				C. Zona, M. Pieri, and I. Carunchio Voltage-Dependent Sodium Channels in Spinal Cord Motor Neurons Display Rapid Recovery From Fast Inactivation in a Mouse Model of Amyotrophic Lateral Sclerosis J Neurophysiol, December 1, 2006; 96(6): 3314 - 3322. [Abstract] [Full Text] [PDF]