AMPKγ2 Deacetylation Drives Nuclear Translocation and Doxorubicin-Induced Cardiomyopathy via Nucleolar Stress Signaling
Doxorubicin (Dox)-induced cardiomyopathy (DIC), characterized by cardiomyocyte apoptosis, remains a major clinical challenge in chemotherapy. The regulatory {gamma}2 subunit of AMP-activated protein kinase (AMPK{gamma}2) plays a key role in cardiovascular diseases, but its function in DIC is poorly understood. Here, we report that Dox induces isoform-specific deacetylation and nuclear accumulation of {gamma}2, triggering nucleolar stress and p53-mediated apoptosis. Mechanistically, HDAC3 and TIP60 interact with {gamma}2 and modulate the acetylation of multiple lysine residues within its nuclear localization signal (NLS), controlling its nucleocytoplasmic shuttling. Dox enhances HDAC3-mediated {gamma}2 deacetylation, thereby driving nuclear accumulation of the {gamma}2-containing AMPK ({gamma}2-AMPK) while suppressing the cytosolic AMPK activity. Nuclear {gamma}2-AMPK phosphorylates and inactivates TIF-IA, a key RNA polymerase I-specific transcription initiation factor, leading to nucleolar stress through inhibition of rRNA transcription. rRNA deficit triggers release of free ribosomal proteins (RPs), which bind to and inhibit the E3 ubiquitin ligase MDM2, resulting in p53 stabilization and activation of apoptotic signaling. Using genetically engineered cardiomyocytes and a DIC mouse model, we found that a deacetyl-mimetic {gamma}2 mutant (6KR) exacerbated DIC, whereas an acetyl-mimetic mutant (6KQ) was cardioprotective. Collectively, our findings establish acetylation-driven nuclear translocation of {gamma}2 as a critical node linking Dox-induced nucleolar stress to p53-dependent apoptosis and suggest a promising cardio-oncology strategy that combines HDAC inhibitors with Dox to mitigate DIC. Significance statementDoxorubicin is an effective cancer drug, but its use is limited by cardiomyopathy. Our study reveals that doxorubicin drives HDAC3-mediated deacetylation of AMPK{gamma}2, exposing its nuclear localization signal and redirecting {gamma}2-containing AMPK from the cytoplasm to the nucleus. Nuclear AMPK{gamma}2 phosphorylates TIF-IA, suppresses ribosomal RNA synthesis, and activates a nucleolar stress pathway that stabilizes p53 and promotes cardiomyocyte apoptosis. In mice, a deacetylation-mimetic AMPK{gamma}2 mutant worsens doxorubicin-induced cardiomyopathy, whereas an acetylation-mimetic mutant is protective. These findings uncover an acetylation-controlled spatial switch in AMPK signaling and identify the AMPK{gamma}2 deacetylation-nucleolar stress axis as a potential target for reducing chemotherapy-associated cardiac injury.