Abstract 9054: Cell-Specific Regulation of the GATA-4/6 Transcription Factors by the Metabolic Enzyme PKM2 Provides Insight into a Biologic Function Essential for Cardiac Health and Survival

Abstract

Background: Pyruvate Kinase M2 (PKM2) is a glycolytic enzyme that can translocate to the nucleus and regulate different transcription factors (TF). Although its function has been studied extensively in cancer, its biologic role in the heart, and specifically terminally differentiated adult cardiomyocytes (CM), remains elusive. Hypothesis: Because PKM1 is the more abundant isoform in CM, we speculated that PKM2 would not have a genetically redundant role to PKM1 and may instead be critical in regulating CM-specific TF. Methods: Transverse aortic constriction (TAC) banding model was used to assess the levels and modifications of PKM2 during heart failure (HF). CM-specific PKM2-deficient mice were generated to evaluate the biological role of PKM2 in adult CM. Unbiased RNA sequencing was utilized to assess novel PKM2-induced signaling pathways in adult CM. Induced pluripotent stem cells (iPSCs) were used to translate mechanistic findings to mature human CM. Results: PKM2 levels were lower, but serine-37 phosphorylated PKM2 ( S37 P-PKM2) was higher in terminally differentiated tissues. Cell-specific analysis showed S37 P-PKM2 was preferentially localized in the nucleus of CM, compared to cardiac fibroblasts (CF) (where PKM2 was mainly cytoplasmic). During TAC-induced HF, PKM2 levels increased in CF but correspondingly decreased in CM, in comparison to sham controls. CM-specific PKM2-deficient mice developed age-dependent cardiac dysfunction with decreased survival, compared to their control littermates. Unbiased RNA sequencing revealed a decrease in cardiac energetic, stress response, angiogenesis, repair and regeneration, and survival pathways from PKM2-deficient CM. In keeping, PKM2-deficient hearts had decreased levels of the cardiomyocyte-specific TF GATA4 and GATA6, compared to control hearts. Finally, the E3 ubiquitin-ligase TRIM35, which was induced during TAC-induced heart failure, ubiquitinated and degraded PKM2, along with GATA4 and GATA6 in primary adult mouse or human iPSC-derived CM. Conclusions: This study shows a new and previously unrecognized role for PKM2 in the regulation of cardiomyocyte-specific transcription factors and identifies a novel therapeutic target (TRIM35) in heart failure.