PP2Acα regulates the Hippo-YAP signaling axis to promote cardiac regeneration and alleviate myocardial infarction.

Limited proliferative capacity of cardiomyocytes (CMs) underlies persistent CMs loss and cardiac dysfunction after myocardial infarction (MI). Although neonatal mammalian hearts retain transient regenerative potential, the molecular mechanisms governing this process remain incompletely understood. Protein phosphatase 2A (PP2A) has been implicated in cardiac protection; however, its role in CMs proliferation and heart regeneration is unclear. Here, using neonatal mouse MI models, cardiomyocyte-specific PP2Acα knockdown mice, pharmacological inhibition with LB-100, adenoviral mediated gain and loss of function approaches, and transcriptomic analysis, we investigated the functional significance and molecular mechanism of PP2Acα in cardiac regeneration. We found that PP2Acα was highly expressed in neonatal hearts, declined with postnatal maturation, and was reinduced following neonatal MI. Cardiomyocyte-specific PP2Acα knockdown markedly reduced CMs proliferation, impaired neonatal heart regeneration, exacerbated post MI cardiac dysfunction, and increased fibrosis, while pharmacological inhibition of PP2A similarly suppressed CMs proliferation both in vivo and in vitro. In contrast, PP2Acα overexpression significantly enhanced mitotic activity in neonatal mouse cardiomyocytes. Mechanistically, co-immunoprecipitation and molecular docking analyses revealed that PP2Acα directly interacted with Yes-associated protein (YAP) and reduced its phosphorylation, thereby promoting YAP nuclear translocation and activation of cell cycle-related gene transcription. YAP knockdown abolishes PP2Acα-induced cardiomyocyte proliferation. Conversely, LB-100 increased YAP phosphorylation without altering its mRNA expression, indicating regulation dependent on phosphatase activity. Collectively, these findings identify PP2Acα as a critical phosphatase that promotes neonatal cardiac regeneration by directly dephosphorylating YAP and activating the Hippo-YAP signaling axis, uncovering a previously unrecognized regulatory mechanism controlling cardiomyocyte proliferation and highlighting a potential therapeutic target for cardiac repair.