TRIM35-mediated degradation of nuclear PKM2 destabilizes GATA4/6 and induces P53 in cardiomyocytes to promote heart failure

Abstract

Pyruvate kinase M2 (PKM2) is a glycolytic enzyme that translocates to the nucleus to regulate transcription factors in different tissues or pathologic states. Although studied extensively in cancer, its biological role in the heart remains unresolved. PKM1 is more abundant than the PKM2 isoform in cardiomyocytes, and thus, we speculated that PKM2 is not genetically redundant to PKM1 and may be critical in regulating cardiomyocyte-specific transcription factors important for cardiac survival. Here, we showed that nuclear PKM2 ( ^S37 P-PKM2) in cardiomyocytes interacts with prosurvival and proapoptotic transcription factors, including GATA4, GATA6, and P53. Cardiomyocyte-specific PKM2-deficient mice ( Pkm2 Mut Cre ⁺ ) developed age-dependent dilated cardiac dysfunction and had decreased amounts of GATA4 and GATA6 (GATA4/6) but increased amounts of P53 compared to Control Cre ⁺  hearts. Nuclear PKM2 prevented caspase-1–dependent cleavage and degradation of GATA4/6 while also providing a molecular platform for MDM2-mediated reduction of P53. In a preclinical heart failure mouse model, nuclear PKM2 and GATA4/6 were decreased, whereas P53 was increased in cardiomyocytes. Loss of nuclear PKM2 was ubiquitination dependent and associated with the induction of the E3 ubiquitin ligase TRIM35. In mice, cardiomyocyte-specific TRIM35 overexpression resulted in decreased ^S37 P-PKM2 and GATA4/6 along with increased P53 in cardiomyocytes compared to littermate controls and similar cardiac dysfunction to Pkm2 Mut Cre ⁺  mice. In patients with dilated left ventricles, increase in TRIM35 was associated with decreased ^S37 P-PKM2 and GATA4/6 and increased P53. This study supports a previously unrecognized role for PKM2 as a molecular platform that mediates cell signaling events essential for cardiac survival.

Abstract

TRIM35-mediated degradation of nuclear PKM2 in cardiomyocytes induces a molecular reprogramming sufficient to induce heart failure.

Factors in heart failure

During heart failure, transcription factors involved in cardiomyocyte survival are repressed. Here, Lorenzana-Carrillo et al. studied the role of pyruvate kinase M2 (PKM2), a glycolytic enzyme, in regulating the transcription factors GATA4/6 and P53. Mice lacking PKM2 in cardiomyocytes had decreased GATA4/6 but increased P53 and developed dilated cardiomyopathy. In adult cardiomyocytes, they observed direct interaction between nuclear PKM2 and the transcription factors, where PKM2 prevented cleavage and degradation of GATA4/6 but promoted P53 degradation. The E3 ubiquitin ligase TRIM35 was found to degrade nuclear PKM2, resulting in cardiac dysfunction when overexpressed in cardiomyocytes in mice, and TRIM35 was up-regulated in human heart failure tissue samples. Results help identify the role of PKM2 in cardiomyocyte survival in heart failure.