Verrucotoxin inhibits KATP channels in cardiac myocytes through a muscarinic M3 receptor-PKC pathway.
Verrucotoxin is the major component of venom from the stonefish (Synanceia verrucosa). Stings from the dorsal spines of the stonefish produce intensive pain, convulsions, hypotension, paralysis, respiratory weakness and collapse of the cardiovascular system, occasionally leading to death. It has been reported that verrucotoxin might modulate ATP-sensitive K+ (KATP) current in frog atrial fibers. However, the mechanism by which verrucotoxin acts on KATP current remains unclear. In this study, we examined whether verrucotoxin inhibited KATP current in guinea pig ventricular myocytes, using the patch clamp method. Verrucotoxin suppressed KATP current induced by pinacidil (KATP channel opener) in a concentration-dependent manner, with a half maximum concentration of 16.3 microg/ml. The effect of verrucotoxin on KATP current was suppressed by atropine (1 microM), a muscarinic receptor antagonist, or by 4-diphenylacetoxy-N-methylpiperidine (100 nM), a muscarinic M3 receptor antagonist. Furthermore, the effect of verrucotoxin on KATP current was attenuated by the protein kinase C (PKC) inhibitor chelerythrine (10 microM) and calphostin C (10 microM), yet not by the cAMP-dependent protein kinase (PKA) inhibitor H-89 (0.5 microM). These results suggest that verrucotoxin inhibits KATP current through the muscarinic M3 receptor-PKC pathway. These findings enhance our understanding of the toxic effects of verrucotoxin from the stonefish.
Wang
Jian-Wu
JW
Department of Physiology II, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
Yazawa
Kazuto
K
Hao
Li-Ying
LY
Onoue
Yoshio
Y
Kameyama
Masaki
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D053119:Benzophenanthridines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005397:Fish Venoms / Q000494:pharmacology*; D006023:Glycoproteins / Q000494:pharmacology*; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D018727:Muscarinic Antagonists / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D020110:Pinacidil / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D043587:Receptor, Muscarinic M3 / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
D000470:Alkaloids; D053119:Benzophenanthridines; D005397:Fish Venoms; D006023:Glycoproteins; D018727:Muscarinic Antagonists; D010880:Piperidines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D047428:Protein Kinase Inhibitors; D043587:Receptor, Muscarinic M3; C094408:verrucotoxin protein, Synanceia verrucosa; D020110:Pinacidil; D001285:Atropine; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D000255:Adenosine Triphosphate; C016299:chelerythrine; D011493:Protein Kinase C