A redox o2 sensor modulates the sr ca2+ counter-current through
voltage- and ca2+-dependent cl channels.
Kourie, Joseph I.
Muscle Research Group, Division of Neuroscience, John Curtin School
of Medical Research, Australian National University, P.O. Box 334,
Canberra City, ACT 2601 AUSTRALIA
APStracts 3:0283C, 1996.
The activity of a relatively small Cl (SCl) channel in the
sarcoplasmic reticulum (SR) vesicles of rabbit skeletal muscle was
preserved following their reconstitution into lipid bilayer. Reducing
O2 pressure (pO2) from 150 torr to < 1 torr in the cis
(cytosolic) side reversibly inhibited the channel activity within 2
min. The modulatory effects, deduced from reduction in Cl- current
levels and in kinetic parameters of channel activation, in normoxic
(pO2 150 torr) and hypoxic (low pO2 < 1 torr) solutions were
mimicked by oxidizing and reducing agents, respectively. Cl- current
transitions to the main open conductance state were increased by 100
[mu]M of the specific sulfhydryl-oxidizing agent 4,4'
-dithiodipyridine (4,4'-DTDP) and inhibited by the sulfhydryl-reducing
agent glutathione (GSH) with a Hill coefficient of 8 and Ki value of
3.1 mM. The inhibitory effects of 5 mM [GSH]cis were prevented by
prior addition of 1 mM iodoacetamide, an alkylating agent, to the
cytosolic side of the channel. These findings suggest that an SH
-dependent mechanism (redox couple, e.g. reduced/oxidized glutathione)
could be involved in the gating of the SCl channel in such a way that
SH-oxidation (GSSH) favours the open state of the channel and SH
-reduction (GSH), which mimics the inhibitory action of low pO2,
favours the closed state.
Received 15 May 1996; accepted in final form 30 August 1996
APS Manuscript Number C265-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996