Contribution of Ryanodine Receptor Subtype 3 to Ca 2+ Responses in Ca 2+ -overloaded Cultured Rat Portal Vein Myocytes
Journal of Biological Chemistry. 2001-04-01; 276(14): 11257-11264
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1. J Biol Chem. 2001 Apr 6;276(14):11257-64. Epub 2001 Jan 9.
Contribution of ryanodine receptor subtype 3 to ca2+ responses in Ca2+-overloaded
cultured rat portal vein myocytes.
Mironneau J(1), Coussin F, Jeyakumar LH, Fleischer S, Mironneau C, Macrez N.
(1)Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017,
Université de Bordeaux II, 146 rue Léo Saignat, Bordeaux Cedex 33076, France.
Using an antisense strategy, we have previously shown that in vascular myocytes,
subtypes 1 and 2 of ryanodine receptors (RYRs) are required for Ca(2+) release
during Ca(2+) sparks and global Ca(2+) responses, evoked by activation of
voltage-gated Ca(2+) channels, whereas RYR subtype 3 (RYR3) has no contribution.
Here, we investigated the effects of increased Ca(2+) loading of the sarcoplasmic
reticulum (SR) on the RYR-mediated Ca(2+) responses and the role of the RYR3 by
injecting antisense oligonucleotides targeting the RYR subtypes. RYR3 expression
was demonstrated by immunodetection in both freshly dissociated and cultured rat
portal vein myocytes. Confocal Ca(2+) measurements revealed that the number of
cells showing spontaneous Ca(2+) sparks was strongly increased by superfusing the
vascular myocytes in 10 mm Ca(2+)-containing solution. These Ca(2+) sparks were
blocked after inhibition of RYR1 or RYR2 by treatment with antisense
oligolucleotides but not after inhibition of RYR3. In contrast, inhibition of
RYR3 reduced the global Ca(2+) responses induced by caffeine and phenylephrine,
indicating that RYR3 participated together with RYR1 and RYR2 to these Ca(2+)
responses in Ca(2+)-overloaded myocytes. Ca(2+) transients evoked by photolysis
of caged Ca(2+) with increasing flash intensities were also reduced after
inhibition of RYR3 and revealed that the [Ca(2+)](i) sensitivity of RYR3 would be
similar to that of RYR1 and RYR2. Our results show that, under conditions of
increased SR Ca(2+) loading, the RYR3 becomes activable by caffeine and local
increases in [Ca(2+)](i).
PMID: 11150292 [Indexed for MEDLINE]