Abstract
In heart cells, several plasma membrane ion channels are targets for
phosphorylation. However, it is not known whether sarcoplasmic reticulum
(SR) ion channels, which are also essential in the regulation of
cardiac function, are regulated by second-messenger systems. Here,
we show that a Cl$^-$ channel in the cardiac SR membrane is activated
by the catalytic subunit of protein kinase A (PKA). Purified cardiac
heavy SR vesicles were incorporated into planar lipid bilayers. This
channel spontaneously inactivated within a few minutes after the
channel was incorporated into the bilayer. Mg-ATP (2-5 mM), but not
the nonhydrolyzable ATP analogue 5'-adenylylimidodiphosphate, added
to the cis solution prevented this spontaneous channel inactivation.
After the inactivation process occurred, the catalytic subunit of
PKA (with 0.05 mM Mg-ATP) reactivated this channel. These effects
of Mg-ATP and PKA on the Cl$^-$ channel were prevented by an
inhibitor of PKA. Thus, these results suggest that this SR Cl$^-$
channel is a novel target of PKA-dependent phosphorylation in cardiac
muscle regulation.
- 1323433
- adenosine
- animals,
- bilayers,
- channels,
- chloride
- gov't,
- hear,
- in
- inhibitors,
- kinase
- kinases,
- lipid
- membrane
- myocardium,
- non-u.s.
- protein
- proteins,
- research
- reticulum,
- sarcoplasmic
- support,
- swine,
- t,
- triphosphate,
- vitro,
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