Influence of the l-type ca-channel [alpha]2/[delta] subunit on
ionic and gating current in transiently-transfected hek 293
cells.
Bangalore, R., G. Mehrke, K. Gingrich, F. Hofmann, and R. S. Kass.
Department of Physiology, University of Rochester School of
Medicine, Rochester, NY 14642, and Institut f[umlaut]ur Pharmakologie
und Toxikologie, Technische Universit[umlaut]at M[umlaut]unchen,
Biedersteinerstr. 29, 80802 M[umlaut]unchen, Germany
APStracts 2:0502H, 1995.
We have measured ionic and gating currents in human embryonic kidney
(HEK 293) cells transiently transfected with cDNAs encoding subunits
of the cardiac voltage-gated L-type Ca2+ channel. Robust recombinant
ionic current and associated non-linear charge movement could be
measured over a broad voltage range without contamination by
endogenous channel activity. Coexpression of the [alpha]2/d subunit
along with [alpha]1 and [beta]2 subunits speeded activation and
deactivation kinetics, and significantly increased the maximal
conductance of ionic current. Charge movement was measured at
voltages negative to the threshold for activation of ionic current,
and gating charge could be immobilized at positive holding potentials
that did not inactivate ionic current. The ratio of maximal ionic
conductance to maximal charge moved remained the same in the absence
or presence of the [alpha]2/[delta] subunit. However, the maximal
amount of charge moved was increased about twofold in the presence of
the [alpha]2/[delta] subunit. These results suggest that co
-expression of the [alpha]2/[delta] subunit enhances the expression of
functional L-type channels and, in addition, provide evidence that
most of the L-type channel-associated non-linear charge movement is
caused by transitions between non-conducting states of the channel
protein that precede both the open and inactivated states.
Received 21 June 1995; accepted in final form 17 October 1995.
APS Manuscript Number H563-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95