CDK5RAP3-Mediated Mitochondrial RQC Alleviates Pathological Cardiac Hypertrophy

BACKGROUND: Recent studies have revealed heterogeneity among ribosomes. Pathological cardiac hypertrophy is characterized by profound alterations in translation. However, how ribosome heterogeneity contributes to this process remains largely unclear. METHODS: We used translating ribosome affinity purification coupled with mass spectrometry to profile ribosome-interacting proteins. Cardiomyocyte-specific gene manipulation was achieved through either genetic knockout or adeno-associated virus-mediated overexpression. Pathological cardiac hypertrophy was induced by transverse aortic constriction surgery in vivo and by phenylephrine stimulation in vitro. RESULTS: The cardiomyocyte-specific ribosome proteomics indicated dynamic alterations in ribosome-interacting proteins during pathological hypertrophy. Notably, multiple proteins associated with ribosome stalling were detected in the ribosome-interactome of hypertrophic hearts. Among these, we verified that CDK5RAP3 (CDK5 regulatory subunit-associated protein 3) exhibited the most specific ribosome binding in hypertrophic hearts. CDK5RAP3 was upregulated and recruited to ribosomes during pathological hypertrophy. It promoted RPL26 (ribosomal protein L26) UFMylation and ribosome-associated quality control on the mitochondrial surface. In vitro, CDK5RAP3 knockdown exacerbated cardiomyocyte hypertrophy induced by phenylephrine, whereas its overexpression attenuated it. In vivo, cardiomyocyte-specific CDK5RAP3 knockout promoted, while adeno-associated virus-mediated overexpression suppressed pathological cardiac hypertrophy induced by transverse aortic constriction. Mechanistically, ribosome stalling on the mitochondrial surface was exacerbated in hypertrophic hearts of both humans and mice, which was associated with impaired mitochondrial protein import. CDK5RAP3 enhanced ribosome-associated quality control, alleviated ribosome stalling, and restored mitochondrial protein import, thereby improving mitochondrial function. Notably, mitochondrial import of PDP1 was maintained by CDK5RAP3-mediated ribosome-associated quality control. Knockdown of PDK (pyruvate dehydrogenase kinase) 1/2, functional antagonists of PDP1, reversed cardiomyocyte hypertrophy caused by CDK5RAP3 deficiency. CONCLUSIONS: This study identifies CDK5RAP3-mediated ribosome-associated quality control on the mitochondrial surface as a critical protective mechanism that preserves protein import and mitochondrial function during pathological cardiac hypertrophy.