Electrophysiological characteristics of skeletal and cardiac muscle
sodium channels expressed in a human cell line.
Chahine, M., I. Deschene, L. Q. Chen, and R. G. Kallen.
Laval Hospital, Research Center, 2725, Chemin St.-Foy, St.-Foy,
Qu[acute]ebec, Canada G1V 4G5 and Department of Biochemistry and
Biophysics, University of Pennsylvania School of Medicine,
Philadelphia, PA 19104-6059
APStracts 3:0030H, 1996.
The [alpha]-subunit encoding for voltage-gated sodium channels, rSkM1
(rat skeletal muscle subtype 1) and hH1 (human heart subtype 1) have
been cloned and expressed by various groups under various conditions
in Xenopus oocytes and the tsA201 (HEK293) mammalian cell line
derived from human embryonic kidney cells. In this study we have
expressed hH1 and rSkM1 in tsA201 cells for comparison under the same
conditions using patch-clamp methods. Our results show significant
differences in the I-V relationship, kinetics of current decay,
voltage-dependence of steady-state inactivation and in the time
constant for recovery from inactivation. We studied several rSkM1/hH1
chimeric sodium channels to identify the structural regions
responsible for the different biophysical behavior of the two channel
subtypes. Exchanging the interdomain (ID3-4) loops, thought to
contain the inactivation particle, between rSkM1 and hH1 had no
effect on the electrophysiological behaviors, including inactivation,
indicating that the differences in channel subtype characteristics
are determined by parts of the channel other than the ID3-4 segment.
The data on a chimeric channel in which D1 and D4 are derived from
hH1 while D2 and D3 and the ID1-2, ID2-3 and ID3-4 loops are from
rSkM1 show that D1 and/or D4 seem to be responsible for the slower
kinetics of inactivation of hH1 while D2 and/or D3 appear to contain
the determinants for the differences in the I-V relationship,
h[lambda] curve and the kinetics of the recovery from inactivation.
Received 16 June 1995; accepted in final form 5 January 1996.
APS Manuscript Number H549-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96