CREG1 promotes autophagy and protects the heart against nutritional stress-induced injury and age-associated hypertrophy, fibrosis and diastolic dysfunction
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Background
Cellular repressor of E1A-stimulated genes 1 (CREG1) is an evolutionarily conserved endolysosomal glycoprotein that enhances lysosomal biogenesis and autophagy, suppresses proliferation, and promotes differentiation. A prior gene targeting strategy that produced truncated N-terminal fragments resulted in embryonic lethality, limiting the ability to assess the physiological role of complete CREG1 loss. We hypothesized that CREG1 regulates cardiac autophagy, thereby maintaining cardiac structure and function under both physiological and stress conditions.
Methods
We generated true Creg1 knockout (KO) mice by deleting the entire open reading frame and established a gain-of-function model by inserting human CREG1 into the Rosa26 locus. Cardiac structure and function were assessed in global and cardiomyocyte-specific Creg1 knockout (cm Creg1 KO) and knock-in (cm CREG1 KI) mice. Autophagy was evaluated using biochemical assays, immunofluorescence, electron microscopy, and the CAG-EGFP-RFP-LC3 reporter analysis.
Results
Global Creg1 knockout mice developed progressive cardiac hypertrophy, fibrosis, and diastolic dysfunction at ∼80 weeks of age. At younger ages, CREG1 deficiency increased susceptibility to nutritional stress, resulting in mitochondrial damage and myofiber disruption in cardiomyocytes. cm Creg1 KO mice exhibited dilated cardiomyopathy, left atrial thrombosis, and lethality around 50 weeks of age; however, interpretation of disease severity is confounded by Myh6-Cre –associated cardiotoxicity, which may mask additional pathogenic effects attributable to CREG1 loss. In contrast, cm CREG1 KI mice demonstrated enhanced exercise capacity under nutritional stress. Mechanistically, CREG1 was localized to endolysosomal and autophagosomal compartments. Loss of CREG1 impaired autophagy flux and mitophagy, likely due to defective autophagosome membrane expansion and degradation. In contrast, CREG1 overexpression enhanced autophagy in cardiomyocytes.
Conclusions
CREG1 is a key regulator of cardiac autophagy, protecting the heart against nutritional stress-induced injury and age-associated cardiac hypertrophy, fibrosis, and diastolic dysfunction.
