Loss of cardiomyocyte eukaryotic elongation factor 1 A2 in adult mice triggers cardiomyopathy due to defective proteostasis

Eukaryotic elongation factor 1A (eEF1A) delivers aminoacyl-tRNAs to ribosomes but also has additional, non-canonical functions. Mammals express two paralogs: eEF1A1 is ubiquitous, whereas eEF1A2 is confined to adult cardiomyocytes, skeletal myocytes, and neurons. Mutations in EEF1A2 cause cardiomyopathy, but underlying mechanisms remain unclear. Using adult, cardiomyocyte-specific Eef1a2 knock-out (Eef1a2-cKO) and Eef1a1/Eef1a2 double knock-out mice, we show that Eef1a2-cKO animals develop cardiomyopathy with increased mortality, systolic dysfunction, and fibrosis, despite unchanged global protein synthesis, while double knock-out mice die early in a sudden manner. Multi-omics analyses reveal post-transcriptional upregulation of ribosomal proteins and translational regulators in both models. Eef1a2-cKO hearts accumulate autophagosomes and protein aggregates, indicating defective autophagy. Mechanistically, we found that eEF1A2 functions as a chaperone supporting protein folding and proteostasis in cardiomyocytes. Early Rapamycin treatment (mTORC1 inhibition) normalizes systolic heart function and survival in Eef1a2-cKO mice and clears autophagosomes and protein aggregates. Thus, eEF1A2 maintains cardiac proteostasis, and mTORC1 inhibition may represent a therapeutic strategy for patients with EEF1A2 mutations.