Stimulation of protein kinase C inhibits bursting in disease-linked mutant human cardiac sodium channels.
BACKGROUND
Mutations in SCN5A, the gene coding for the human cardiac Na+ channel alpha-subunit, are associated with variant 3 of the long-QT syndrome (LQT-3). Several LQT-3 mutations promote a mode of Na+ channel gating in which a fraction of channels fail to inactivate, contributing sustained Na+ channel current (Isus), which can delay repolarization and prolong the QT interval. Here, we investigate the possibility that stimulation of protein kinase C (PKC) may modulate Isus, which is prominent in disease-related Na+ channel mutations.


RESULTS
We measured the effects of PKC stimulation on Na+ currents in human embryonic kidney (HEK 293) cells expressing 3 previously reported disease-associated Na+ channel mutations (Y1795C, Y1795H, and DeltaKPQ). We find that the PKC activator 1-oleoyl-2-acetyl-sn-glycerol (OAG) significantly reduced Isus in the mutant but not wild-type channels. The effect of OAG on Isus was reduced by the PKC inhibitor staurosporine (2.5 micromol/L), ablated by the mutation S1503A, and mimicked by the mutation S1503D. Isus recorded in myocytes isolated from mice expressing DeltaKPQ channels was similarly inhibited by OAG exposure or stimulation of alpha1-adrenergic receptors by phenylephrine. The actions of phenylephrine on Isus were blocked by the PKC inhibitor chelerythrine.


CONCLUSIONS
We conclude that stimulation of PKC inhibits channel bursting in disease-linked mutations via phosphorylation-induced alteration of the charge at residue 1503 of the Na+ channel alpha-subunit. Sympathetic nerve activity may contribute directly to suppression of mutant channel bursting via alpha-adrenergic receptor-mediated stimulation of PKC.
Tateyama
M
M
Department of Pharmacology, College of Physicians and Surgeons of Columbia University, 630 W 168th St, PH 7W 318, New York, NY 10032, USA.
Kurokawa
J
J
Terrenoire
C
C
Rivolta
I
I
Kass
R S
RS
D000818:Animals; D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008133:Long QT Syndrome / Q000235:genetics / Q000503:physiopathology*; D051379:Mice; D008817:Mice, Mutant Strains; D032342:Muscle Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013564:Sympathetic Nervous System / Q000502:physiology; D014162:Transfection
D004075:Diglycerides; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D062554:NAV1.5 Voltage-Gated Sodium Channel; D021122:Protein Subunits; C568320:SCN5A protein, human; C568321:Scn5a protein, mouse; D015222:Sodium Channels; C038237:1-oleoyl-2-acetylglycerol; D012964:Sodium; D011493:Protein Kinase C