PDK1–AKT signaling pathway regulates the expression and function of cardiac hyperpolarization-activated cyclic nucleotide-modulated channels
Introduction
The protein kinase A, protein kinase G, and protein kinase C (AGC) family regulates multiple cellular functions and physiological processes [1]. 3-Phosphoinositide-dependent protein kinase-1 (PDK1) [2] and phosphatidylinositol 3-kinase (PI3K) [3] are important signaling molecules in heart failure (HF) processing, pathologic heart remodeling; and the functioning of ion channels including sodium [4], potassium, and calcium currents in cardiomyocytes [5]. Similarly, AKT, is also important in many cardiovascular pathological processes [6]. Mice with PDK1 knockout presented with HF and sudden death within 11 weeks [7]. Sodium current downregulation and atrioventricular block might be causes of sudden cardiac death [4]. In clinical, the inhibition of PI3K–PDK1–AKT signaling represents an underexplored target for cancer therapy [8,9]. However, the cardiovascular toxic effects, including HF and arrhythmia, of targeted cancer therapies have attracted increasing attention [10]. For arrhythmia, the incidence rates of QT prolongation and torsades de pointes are on the rise due to the drugs used in cancer management [8]. For example, ibrutinib, a potent tyrosine kinase inhibitor, was associated with a higher risk of atrial fibrillation (AF) [11]. Further, patients with germline mutations of certain AGC family genes, such as PTEN [12] or CYP27A1 [13], are plagued by a cancer-predisposition syndrome and a higher risk of cardiovascular diseases.
A variety of experimental and clinical studies have found that HF, coronary artery disease, and arrhythmia are linked with an elevated heart rate [14]. An increased heart rate is one of the independent predictors of cardiovascular diseases, especially HF [15]. The hyperpolarization-activated cyclic nucleotide-modulated channel (HCN), which is regulated by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] on the membrane constitutive component [16], generates spontaneous electrical activity in the heart [17], and it is suggested that increased atrial or ventricular expression of HCNs in hypertrophied and failing hearts leads to arrhythmia [18]. Thus, the inhibition of HCN with ivabradine is considered to reduce the heart rate and improve the prognosis of HF [19]. Recent research results have also supported that HCN2/4 RNA and protein expression were significantly increased in atrial myocytes of animals with atrial fibrillation [20], and ivabradine has also been found to inhibit HCNs via AKT-endothelial nitric oxide synthase signaling [21] and decrease the induction rate of AF [22]. These results suggest that changes in regional HCN expression patterns were associated with the onset and maintenance of AF [23]. It is understood that HCNs are modulated by cyclic nucleotides in cardiac nodal cells and subsidiary pacemakers [24], but whether HCNs are regulated by the AGC protein kinase family remains unclear.
Given their similar cardiovascular toxic or side effects and the inhibition of AGC protein kinases in certain antitumor drugs, electrical remodeling of HCNs has previously been associated with the onset and maintenance of HF and AF. We sought to investigate the correlation between the two mechanisms by considering the hypothesis that the PDK1–AKT signaling pathway of AGC family protein kinases is involved in the regulation of HCNs in an effort to better understand the mechanism of the cardiovascular toxicity of cancer therapies.
Section snippets
Model of conditional PDK1 knockout mice
To establish the heart-specific “knockout” mouse model, the Cre/Loxp system was used to delete PDK1 in the myocardium. PDK1-floxed (PDK1F/F) and α-myosin heavy chain Cre (αMHC-Cre) mice were kindly provided by Dr. Zhongzhou Yang (Ministry of Education Key Laboratory of Model Animal for Disease Study, Nanjing University, China). In brief, the PDK1F/F mice were crossed with αMHC-Cre mice to delete PDK1 in cardiomyocytes. The knockout methods and verification of the heart-specific “knockout” mouse
Protein expression and current of HCNs in atrial myocytes of PDK1-knockout mice
In Fig. 1A and B, western blot experiments showed that the protein expression of PDK1 was decreased by 78% after PDK1 knockout, whereas AKT phosphorylation at the Thr308 site was decreased by 43% (p < 0.05). For HCNs, the expression level of HCN1 was decreased by 30.10% (p < 0.05) (Fig. 1C), that of HCN2 showed a 2.79-fold increase (p < 0.05) (Fig. 1D), and that of HCN4 showed a 1.62-fold increase (p < 0.05) (Fig. 1E). In patch-clamp experiments, we found that the peak value of HCN currents
Discussion
In clinical practice, arrhythmia was a common complication in patients with HF. In particular, ventricular arrhythmias are one important factor in palpitations and cardiac arrest [25], whereas chronic AF is a common cause of the deterioration of cardiac function [26]. Recent research has suggested that HF and arrhythmia are also common cardiac side effects in patients receiving targeted cancer therapies [10], such as tyrosine kinase inhibitors. Meanwhile, heart rate is a prognostic marker and
Conclusion
Our study suggested that the expression and function of HCN ion channels were regulated by the PDK1–AKT signaling pathway, which may be one of the possible mechanisms of arrhythmia induced by HF or tyrosine kinase-related drugs, and also provided a mechanism for the occurrence and therapeutic effects of HCN-related arrhythmias in the study.
Funding
This work was supported by the National Natural Science Foundation of China (grant number 81600267).
Declaration of competing interest
The authors declare that there are no conflicts of interest.
Acknowledgments
None.
References (52)
- et al.
PDK1, the master regulator of AGC kinase signal transduction
Semin. Cell Dev. Biol.
(2004) - et al.
Reduced phosphoinositide 3-kinase (p110alpha) activation increases the susceptibility to atrial fibrillation
Am. J. Pathol.
(2009) - et al.
The critical role of Akt in cardiovascular function
Vasc. Pharmacol.
(2015) - et al.
Ibrutinib increases the risk of atrial fibrillation, potentially through inhibition of cardiac PI3K-Akt signaling
Blood.
(2014) - et al.
Ibrutinib-associated atrial fibrillation
JACC. Clin. Electrophysiol.
(2018) - et al.
Ivabradine and outcomes in chronic heart failure (SHIFT): a randomised placebo-controlled study
Lancet.
(2010) - et al.
A population-based study of the long-term risks associated with atrial fibrillation: 20-year follow-up of the Renfrew/Paisley study
Am. J. Med.
(2002) - et al.
Heart rate as a prognostic marker and therapeutic target in acute and chronic heart failure
Int. J. Cardiol.
(2018) - et al.
Inhibition of I(f) in the atrioventricular node as a mechanism for dronedarone’s reduction in ventricular rate during atrial fibrillation
Heart Rhythm.
(2013) - et al.
Genetic and pharmacological inhibition of Rheb1-mTORC1 signaling exerts cardioprotection against adverse cardiac remodeling in mice
Am. J. Pathol.
(2013)
mTOR.RICTOR is the Ser473 kinase for Akt/protein kinase B in 3T3-L1 adipocytes
J. Biol. Chem.
Roles of phospho-GSK-3beta in myocardial protection afforded by activation of the mitochondrial K ATP channel
J. Mol. Cell. Cardiol.
The serum- and glucocorticoid-inducible kinases SGK1 and SGK3 regulate hERG channel expression via ubiquitin ligase Nedd4-2 and GTPase Rab11
J. Biol. Chem.
PDE2 at the crossway between cAMP and cGMP signalling in the heart
Cell. Signal.
Dual loss of PI3Kalpha and PI3Kgamma signaling leads to an age-dependent cardiomyopathy
J. Mol. Cell. Cardiol.
Novel insights into the distribution of cardiac HCN channels: an expression study in the mouse heart
J. Mol. Cell. Cardiol.
Imbalance of HCN1 and HCN2 expression in hippocampal CA1 area impairs spatial learning and memory in rats with chronic morphine exposure
Prog. Neuro-Psychopharmacol. Biol. Psychiatry
PDK1 coordinates survival pathways and beta-adrenergic response in the heart
Proc. Natl. Acad. Sci. U. S. A.
Deletion of PDK1 causes cardiac sodium current reduction in mice
PLoS One
Control of cardiac repolarization by phosphoinositide 3-kinase signaling to ion channels
Circ. Res.
Deficiency of PDK1 in cardiac muscle results in heart failure and increased sensitivity to hypoxia
EMBO J.
Necessity to evaluate PI3K/Akt signalling pathway in proarrhythmia
Open Heart.
Cardiovascular toxic effects of targeted cancer therapies
N. Engl. J. Med.
PTEN mutations as a cause of constitutive insulin sensitivity and obesity
N. Engl. J. Med.
27-Hydroxycholesterol links hypercholesterolemia and breast cancer pathophysiology
Science.
If channel as an emerging therapeutic target for cardiovascular diseases: a review of current evidence and controversies
Front. Pharmacol.
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