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Receptor-mediated modulation of rat KV1.2 in Xenopus oocytes
H Murakoshi1, K Ishii, K Nunoki
1Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan.
Abstract:
To investigate mechanisms for the receptor-mediated inhibition of a rat cardiac K+ channel clone (KV1.2), we coexpressed KV1.2 with a subtype of endothelin receptors (ETA) in Xenopus oocytes. Effects of endothelin ETA receptor stimulation were mimicked by application of PMA (4-beta-phorbol 12-myristate 13-acetate; 0.1 microM) or intracellular injection of CaCl2 (estimated concentration of 1 microM). These effects diminished in the presence of staurosporine (1 microM) or EGTA (estimated concentration of 5 mM). These results suggest that both activation of protein kinase C and an increase in intracellular Ca2+ contribute to the suppression.
Insights
Endothelin receptor stimulation inhibits rat cardiac potassium channels (KV1.2) via protein kinase C and increased intracellular calcium. These pathways are crucial for regulating cardiac electrophysiology.
Area of Science:
- Cardiovascular Physiology
- Molecular Biology
- Ion Channel Function
Background:
- Cardiac K+ channels are critical for heart rhythm.
- Receptor-mediated regulation of ion channels influences cardiac function.
- Endothelin receptors play a role in cardiovascular regulation.
Purpose of the Study:
- To elucidate the mechanisms underlying receptor-mediated inhibition of the rat cardiac K+ channel KV1.2.
- To investigate the involvement of endothelin ETA receptors in modulating KV1.2 activity.
- To identify intracellular signaling pathways mediating channel suppression.
Main Methods:
- Coexpression of rat KV1.2 and endothelin ETA receptors in Xenopus oocytes.
- Stimulation of ETA receptors using endothelin.
- Application of protein kinase C activator (PMA) and intracellular calcium.
- Assessment of channel inhibition using specific inhibitors (staurosporine, EGTA).
Main Results:
- Endothelin ETA receptor stimulation mimicked the effects of PMA and increased intracellular CaCl2.
- Inhibition of KV1.2 by ETA receptor stimulation was attenuated by staurosporine and EGTA.
- These findings indicate a role for protein kinase C and Ca2+ in channel suppression.
Conclusions:
- Receptor-mediated inhibition of rat cardiac KV1.2 involves both protein kinase C activation and increased intracellular Ca2+.
- These signaling pathways are key mediators of endothelin's effects on cardiac K+ channels.
- Understanding these mechanisms is vital for comprehending cardiac electrophysiology and potential therapeutic targets.