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Published on: September 10, 2015
Phospholamban ablation by RNA interference increases Ca2+ uptake into rat cardiac myocyte sarcoplasmic reticulum
Atai Watanabe1, Masashi Arai, Miki Yamazaki
1Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Gunma 371 8511, Japan.
Abstract:
Phospholamban (PLB) inhibits SR Ca(2+)-ATPase 2 (SERCA2) Ca(2+) uptake and is a potential therapeutic target in the context of heart failure. RNA interference (RNAi) is a technique that produces sequence-specific, post-transcriptional gene silencing through the use of double-stranded RNA directed against the homologous target gene. The goal of the current study was to investigate the efficacy of the RNAi method for ablation of PLB gene expression and restoration of Ca(2+) uptake function in cultured neonatal rat cardiac myocytes in which SERCA2 protein levels were decreased. Myocytes were transfected with 21-nucleotide duplexes of small interfering RNA (siRNA) targeting PLB (30 nmol/l) or with scramble sequence using a haemagglutinating virus of Japan (HVJ) envelope vector. Administration of PLB siRNA resulted in the reduction of PLB mRNA level to approximately 6% of that observed after administration of scramble siRNA group at 12 h after transfection. Further, PLB protein levels in the PLB siRNA groups were 12% of that in cells treated with scramble siRNA on day 2, and the mRNA and protein levels for SERCA2 and calsequestrin were not affected. In addition, Ca(2+) uptake affinity was increased in total homogenates from the PLB siRNA group (a 29% decrease in EC(50) value when compared with scramble siRNA group). Finally, PLB siRNA restored Ca(2+) uptake affinity following hydrogen peroxide-induced decreases in SERCA2 and PLB mRNA expression. These results demonstrate that PLB-targeted RNAi inhibited endogenous PLB expression in neonatal rat myocytes and restored Ca(2+) uptake affinity in cardiac myocytes in which SERCA2 protein levels were decreased. This technique may represent a novel therapeutic strategy for heart failure.
Insights
RNA interference effectively silenced phospholamban (PLB) gene expression in rat heart cells. This approach restored calcium uptake function, offering a potential new therapy for heart failure.
Area of Science:
- Cardiovascular Biology
- Molecular Medicine
- Gene Silencing Technologies
Background:
- Phospholamban (PLB) inhibits sarcoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) activity, impacting cardiac contractility.
- Dysfunctional SERCA2 and altered calcium handling are implicated in heart failure.
- RNA interference (RNAi) offers a method for targeted gene silencing.
Purpose of the Study:
- To evaluate the efficacy of RNA interference (RNAi) for phospholamban (PLB) gene silencing in neonatal rat cardiac myocytes.
- To assess the impact of PLB gene ablation on calcium (Ca2+) uptake function.
- To determine if RNAi-mediated PLB silencing can restore Ca2+ uptake in conditions of decreased SERCA2 levels.
Main Methods:
- Neonatal rat cardiac myocytes were transfected with small interfering RNA (siRNA) targeting PLB using a haemagglutinating virus of Japan (HVJ) envelope vector.
- PLB mRNA and protein levels were quantified post-transfection.
- Calcium (Ca2+) uptake affinity was measured using EC50 values.
- Experiments included conditions with hydrogen peroxide-induced decreases in SERCA2 and PLB.
Main Results:
- PLB siRNA significantly reduced PLB mRNA to ~6% and protein to 12% of control levels within 12 hours and 2 days, respectively.
- SERCA2 and calsequestrin mRNA and protein levels remained unaffected by PLB siRNA.
- Ca2+ uptake affinity increased by 29% (decreased EC50) in PLB siRNA-treated myocytes.
- PLB siRNA restored Ca2+ uptake affinity in myocytes with experimentally reduced SERCA2 and PLB levels.
Conclusions:
- PLB-targeted RNAi effectively inhibits endogenous PLB expression in neonatal rat cardiac myocytes.
- This gene silencing strategy restores Ca2+ uptake affinity, particularly in conditions mimicking heart failure.
- RNAi-mediated PLB suppression presents a promising novel therapeutic avenue for heart failure treatment.
