Investigating potential modifier genes of chronic PKA activation in heart failure

Abstract

The cAMP-dependent protein kinase (PKA) is a major downstream effector of β-adrenergic signaling responsible for the positive inotropic effect of catecholamines. The PKA holoenzyme is a heterotetramer composed of two catalytic (C) and two regulatory (R) subunits. Three C subunits (Cα, Cβ and Cγ) are coded by three genes and four R subunits (RIα, RIβ, RIIα and RIIβ) are encoded by four genes but the heart expresses predominantly Cα, RIα and RIIα. We have shown that conditional knock-out of RIα in cardiomyocytes from adult mice (RIα-icKO) have constitutive PKA activation and spontaneously develop heart failure with reduced ejection fraction (HFrEF) upon aging, resulting in 50% mortality after 1 year (Bedioune et al. submitted). In this work, we aimed to better characterize the HF phenotype of RIα-icKO mice. We performed echocardiography, RT-qPCR, western blot and bulk RNA sequencing in RIα-icKO mice and control littermates at 1 year of age. We show that the HF phenotype of the surviving RIα-icKO mice at 1 year is heterogeneous: among 51 mice analyzed by echocardiography and gravimetry, 23 (45%) showed clear signs of HF (EF < 50%, cardiac hypertrophy and dilatation, lung congestion, named HFKO), whereas 18 (35%) had none (named NFKO) and 10 had an intermediary phenotype (20%). RIα residual expression and PKA activity appeared similar in HFKO (n = 6–9) and NFKO (n = 6–10) Transcriptomic analysis revealed dysregulation of typical HF marker genes in NFKO that was generally exacerbated in HFKO. Gene ontology analysis also showed TOP 10 up-regulated and down-regulated pathways classically associated with HF that were similar in HFKO and NFKO. A total of 542 genes were differentially expressed (fc 1.5, P < 0.05) between HFKO and NFKO. Cross-referencing with a list of 821 genes containing genes associated with HF from NCBI and components of β-AR signaling yielded 35 differentially expressed genes, among which 9 were selected as potential modifiers of the phenotype based on the literature. Our results suggest that NFKO represent a compensated stage of HF development. Comparison with HFKO identified new genes that could modulate the impact of chronic PKA activation on HF development. Further studies are required to identify other potential candidates and validate them in neonatal cardiomyocytes with chronic PKA activation.