Role of A_2AR-D2R Dimerization and D₂R-Biased Signaling in PDE10A-Mediated Cardiac Hypertrophy

Pathological cardiomyocyte (CM) hypertrophy is a hallmark of dilated cardiomyopathy and heart failure, driven by mechanical or neurohumoral stress. Although we previously demonstrated PDE10A (phosphodiesterase 10A) as a critical contributor and potential therapeutic target in pathological cardiac remodeling and dysfunction, the underlying mechanisms remain unclear. Here, we investigated the specific signaling pathways and sources of cyclic nucleotides modulated by PDE10A in CM hypertrophy.

CM hypertrophy was induced by angiotensin II in isolated adult mouse CMs, with hypertrophy assessed by cell surface area and protein synthesis. PDE10A inactivation was achieved through PDE10A knockout or inhibition with TP-10. Various pharmacological agonists/antagonists, genetic mutants, and knockout models of D₂R (dopamine receptor D2) and A_2AR (adenosine A_2A receptor) were used to study the role of A_2AR-D₂R heterodimer and downstream signaling in CM hypertrophy in vitro and in vivo. Viral vectors were used to manipulate protein or small hairpin RNA expression targeting key signaling molecules.

We demonstrated that the antihypertrophic effect of PDE10A inactivation is specifically dependent on cAMP/PKA (protein kinase A) signaling. Importantly, we discovered an A_2AR-D₂R heterodimer and its association with PDE10A in CMs. The A_2AR-D₂R heterodimer mediates the βarr2 (beta-arrestin 2)-biased D₂R signaling, and activating D₂R-biased signaling antagonizes cardiac hypertrophy and dysfunction. PDE10A deficiency or inhibition enhanced A_2AR-D₂R heterodimerization, promoting βarr2-biased D₂R signaling and downstream PP2A (protein phosphatase 2A)-B56δ activation through increased A_2AR/cAMP/PKA-mediated D₂R phosphorylation. PDE10A inactivation inhibits stress signal-induced HDAC5 (histone deacetylase 5) nuclear export and phosphorylation, which are dependent on PP2A. Genetic and pharmacological approaches in animal models confirmed the critical roles of A_2AR-D₂R heterodimerization, D₂R phosphorylation, and biased D₂R signaling in vivo. Furthermore, combining PDE10A inhibition with A_2AR or D₂R-biased agonism produced synergistic antihypertrophic effects, highlighting their novel therapeutic potential.

Our findings reveal A_2AR-D₂R dimerization and βarr2-biased D₂R signaling as novel and critical mechanisms for counteracting pathological CM hypertrophy and cardiac dysfunction. PDE10A acts as a pivotal negative regulator of this signaling axis. Targeting PDE10A, A_2AR-D₂R/βarr2 signaling, or both offers potentially novel therapeutic strategies for combating pathological cardiac remodeling and cardiac dysfunction.