Cardioprotective effects of estradiol include the activation of large-conductance Ca(2+)-activated K(+) channels in cardiac mitochondria.
The molecular components of the large-conductance Ca(2+)-activated K(+) channels that are functionally expressed in mitochondria (mitoK(Ca)) in cardiac myocytes have not been identified. Our experimental results show that the transcript corresponding to the large-conductance Ca(2+)-activated K(+) channel beta1-subunit (BK-beta1) is substantially expressed in mammalian heart. A yeast two-hybrid assay showed the BK-beta1 protein can interact with a mitochondrial protein, cytochrome c oxidase subunit I (Cco1). Results from immunocytochemical experiments also demonstrated that BK-beta1 interacted with Cco1 and colocalized in rat cardiac mitochondria. Furthermore, 17beta-estradiol, which enhances the activity of the BK channel alpha-subunit only in the presence of the beta1-subunit, significantly increased flavoprotein oxidation in rat ventricle myocytes and decreased the rate of cell death under simulated ischemia. Single-channel recordings from mitochondrial inner membrane indicated that the activity of mitoK(Ca), which had a conductance of approximately 270 pS, was enhanced by 17beta-estradiol and blocked by paxilline. In combination, the present study revealed a new mechanism for the cardioprotective effects of 17beta-estradiol, which include the activation of mitoK(Ca) via the interaction with BK-beta1. BK-beta1 may be an important molecular component that functionally couples with both Cco1 and mitoK(Ca) pore-forming alpha-subunit.
Ohya
Susumu
S
Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan.
Kuwata
Yukiko
Y
Sakamoto
Kazuho
K
Muraki
Katsuhiko
K
Imaizumi
Yuji
Y
D000595:Amino Acid Sequence; D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D005420:Flavoproteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008322:Mammals; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D008969:Molecular Sequence Data; D017202:Myocardial Ischemia / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D020798:Two-Hybrid System Techniques; D015003:Yeasts
D005420:Flavoproteins; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D004958:Estradiol