Activation of the Ca(2+)-activated nonselective cation channel by diacylglycerol analogues in rat cardiomyocytes.
BACKGROUND
Cardiac hypertrophy is associated with changes in electrophysiologic properties due to ionic channel modifications and increases in protein kinase C (PKC) activity and diacylglycerol (DAG) content. These changes may contribute to an increased propensity for arrhythmia. Similar electrophysiologic modifications have been reported in adult rat cardiomyocytes undergoing dedifferentiation in primary culture.


RESULTS
Single-channel measurements on such cells identified the appearance of a Ca(2+)-activated nonselective cation channel (NSC(Ca)) during the dedifferentiation process. The current study investigated the sensitivity of this channel to PKC and DAG analogues. In the cell-attached configuration, channel conductance was 20.2 pS under physiologic conditions. Perfusion with the DAG analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG, 0.1 mM) or the PKC activator phorbol 12-myristate 13-acetate (PMA, 0.5 microM) increased the channel normalized open probability (nPo), whereas in the presence of the PKC inhibitor calphostin C (1 microM), only OAG retained this effect. In the inside-out configuration, perfusion of both DAG analogues OAG (0.1 mM) and 1-stearoyl-2-arachidonoyl-sn-glycerol (SAG, 10 microM) on the inside of the membrane increased nPo. These results indicate that DAG regulates the NSC(Ca) channel via both the PKC pathway and by a direct interaction.


CONCLUSIONS
DAG content, PKC activity, and channel expression increased during hypertrophy. This indicates that the NSC(Ca) channel exhibits high activity in this condition and, therefore, is a candidate for the genesis of arrhythmias in ventricular cardiomyocytes. In addition, regulation of the channel by DAG and PKC contributes to current understanding of the physiologic role of this channel, which shares properties with the cloned TRPM4b channel.
Guinamard
Romain
R
Laboratoire des Biomembranes et Signalisation Cellulaire, CNRS UMR 6558, Université de Poitiers, Poitiers, France. romain.guinamard@univ-poitiers.fr
Chatelier
Aurélien
A
Lenfant
Jacques
J
Bois
Patrick
P
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism*; D002273:Carcinogens / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004075:Diglycerides / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D023421:Models, Animal; D008955:Models, Cardiovascular; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013223:Statistics as Topic; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015220:Calcium Channels; D002273:Carcinogens; D004075:Diglycerides; D024681:Potassium Channels, Calcium-Activated; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate