Abstract
Late Na(+) current (I(NaL)) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) are both increased in the diseased heart. Recently, CaMKII was found to phosphorylate the Na(+) channel 1.5 (Na(v)1.5), resulting in enhanced I(NaL). Conversely, an increase of I(NaL) would be expected to cause elevation of intracellular Ca(2+) and activation of CaMKII. However, a relationship between enhancement of I(NaL) and activation of CaMKII has yet to be demonstrated. We investigated whether Na(+) influx via Na(v)1.5 leads to CaMKII activation and explored the functional significance of this pathway. In neonatal rat ventricular myocytes (NRVM), treatment with the I(NaL) activators anemone toxin II (ATX-II) or veratridine increased CaMKII autophosphorylation and increased phosphorylation of CaMKII substrates phospholamban and ryanodine receptor 2. Knockdown of Na(v)1.5 (but not Na(v)1.1 or Na(v)1.2) prevented ATX-II-induced CaMKII phosphorylation, providing evidence for a specific role of Na(v)1.5 in CaMKII activation. In support of this view, CaMKII activity was also increased in hearts of transgenic mice overexpressing a gain-of-function Na(v)1.5 mutant (N(1325)S). The effects of both ATX-II and the N(1325)S mutation were reversed by either I(NaL) inhibition (with ranolazine or tetrodotoxin) or CaMKII inhibition (with KN93 or autocamtide 2-related inhibitory peptide). Furthermore, ATX-II treatment also induced CaMKII-Na(v)1.5 coimmunoprecipitation. The same association between CaMKII and Na(v)1.5 was also found in N(1325)S mice, suggesting a direct protein-protein interaction. Pharmacological inhibitions of either CaMKII or I(NaL) also prevented ATX-II-induced cell death in NRVM and reduced the incidence of polymorphic ventricular tachycardia induced by ATX-II in rat perfused hearts. Taken together, these results suggest that a Na(v)1.5-dependent increase in Na(+) influx leads to activation of CaMKII, which in turn phosphorylates Na(v)1.5, further promoting Na(+) influx. Pharmacological inhibition of either CaMKII or Na(v)1.5 can ameliorate cardiac dysfunction caused by excessive Na(+) influx.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetanilides / pharmacology
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Acetanilides / therapeutic use
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Amino Acid Substitution / physiology*
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Animals
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Animals, Newborn
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Calcium / metabolism
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Calcium Signaling / drug effects
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Calcium Signaling / physiology
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Calcium-Binding Proteins / metabolism
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / antagonists & inhibitors
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism*
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Caspase 3 / metabolism
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Cell Death / drug effects
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Cell Survival / drug effects
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Cnidarian Venoms / pharmacology
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Dose-Response Relationship, Drug
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Electrophysiological Phenomena / drug effects
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Electrophysiological Phenomena / physiology
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Female
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Gene Expression / drug effects
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Heart Ventricles / cytology
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Heart Ventricles / drug effects
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Heart Ventricles / metabolism*
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Humans
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Mice
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Mice, Inbred Strains
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Mice, Transgenic
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Myocytes, Cardiac / drug effects
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Myocytes, Cardiac / metabolism*
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NAV1.5 Voltage-Gated Sodium Channel
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Peptides / pharmacology
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Peptides / therapeutic use
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Perfusion
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Phosphorylation / drug effects
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Piperazines / pharmacology
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Piperazines / therapeutic use
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Protein Binding / drug effects
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Protein Binding / physiology
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RNA, Small Interfering / genetics
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Rabbits
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Ranolazine
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Rats
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Rats, Sprague-Dawley
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Ryanodine Receptor Calcium Release Channel / metabolism
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Sodium / metabolism*
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Sodium Channels / genetics
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Sodium Channels / metabolism*
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Sodium-Calcium Exchanger / antagonists & inhibitors
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Sodium-Calcium Exchanger / metabolism
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Tachycardia, Ventricular / chemically induced
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Tachycardia, Ventricular / prevention & control
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Tetrodotoxin / pharmacology
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Veratridine / pharmacology
Substances
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Acetanilides
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Calcium-Binding Proteins
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Cnidarian Venoms
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NAV1.5 Voltage-Gated Sodium Channel
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Peptides
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Piperazines
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RNA, Small Interfering
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Ryanodine Receptor Calcium Release Channel
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SCN5A protein, human
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Scn5a protein, mouse
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Scn5a protein, rat
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Sodium Channels
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Sodium-Calcium Exchanger
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autocamptide-2-related inhibitory peptide II
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phospholamban
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sodium-calcium exchanger 1
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Tetrodotoxin
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toxin II (Anemonia sulcata)
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Veratridine
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Sodium
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Ranolazine
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Calcium-Calmodulin-Dependent Protein Kinase Type 2
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Casp3 protein, rat
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Caspase 3
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Calcium