β-TrCP targets nucleolin and modulates phase separation to restrict ribosome biogenesis in myocardial infarction hearts.

Myocardial infarction (MI) remains a significant global health challenge, as limited long-term efficacy of coronary interventions is largely due to inadequate cardiomyocyte (CM) regeneration. Ribosome biogenesis, a key driver of cell regeneration, and Nucleolin (NCL), a cardioprotective protein, have emerged as crucial factors in post-MI recovery. While liquid-liquid phase separation (LLPS) plays a dynamic role in cellular regulation, its impact on NCL-mediated ribosome biogenesis following MI remains unclear. Using Ribo-Halo, Ribo-disome, and AgNOR staining to map ribosome biogenesis, along with co-immunoprecipitation, molecular docking, FRAP, and confocal imaging to examine NCL ubiquitination and LLPS dynamics, we investigated these mechanisms. In MI mice and hypoxic cells, we identified an inverse correlation between the E3 ubiquitin ligase β-TrCP and NCL levels. Our Co-IP results demonstrate a functional interaction between β-TrCP and NCL in cytoplasm, and hypoxia induced LLPS transition of NCL in nuclear. NCL depletion impaired ribosome biogenesis and CM renewal. Our findings reveal NCL depletion-mediated by β-TrCP and LLPS formation as a key mechanism hindering cardiac repair post-MI. This study provides valuable insights and introduces potential therapeutic target for treating MI.