The interaction of estrogen receptor α and caveolin-3 regulates connexin43 phosphorylation in metabolic inhibition-treated rat cardiomyocytes

Caveolin-3, the major caveolin isoform in cardiomyocytes, plays an important role in the rapid signaling pathways initiated by stimulation of the membrane-associated molecules. To examine the role of caveolin-3 in regulating estrogen receptor a in cardiomyocytes, we investigate whether the membrane estrogen receptor alpha associates with caveolin-3 and whether this association is linked to the 17 beta-estradiol-mediated signals In control cardiomyocytes, following discontinuous sucrose gradient centrifugation. caveolin-3 was found predominantly in the lipid raft buoyant fractions, whereas it was distributed to both the buoyant and non-lipid raft heavy fractions following metabolic inhibition treatment Confocal microscopy showed that estrogen receptor a co-localized with caveolin-3 on the plasma membrane of neonatal and adult rat cardiomyocytes This membrane labeling of estrogen receptor alpha was not seen following treatment with the cholesterol-depleting agent methyl-beta-cyclodextrin (5 mM), whereas metabolic inhibition had little effect on the membrane distribution of estrogen receptor alpha. Metabolic inhibition induced tyrosine phosphorylation of caveolin-3 and decreased its association with estrogen receptor alpha. both effects being mediated via a Src activation mechanism, since they were inhibited by the selective tyrosine kinase inhibitor PP2. Metabolic inhibition also induced tyrosine phosphorylation of connexin43 and increased its association with c-Src, both effects being prevented by 17 beta-estradiol (200 nM). The effect of 17 beta-estradiol on metabolic inhibition-induced tyrosine phosphorylation of connexin43 was inhibited by the specific estrogen receptor antagonist ICI182780. These data identify cardiac caveolin-3 as juxtamembrane scaffolding for estrogen receptor alpha docking at caveolae, which provide a unique compartment for conveying 17 beta-estradiol-elicited, rapid signaling to regulate connexin43 phosphorylation during ischemia. (C) 2009 Elsevier Ltd All rights reserved.