Autophagy has stabilizing functions for cardiomyocytes. Recent studies indicate that an impairment in the autophagy pathway can seriously affect morphology and function, potentially leading to heart failure. However, the role and the underlying mechanism of the endosomal sorting complex required for transport (ESCRT) family protein, in particular the AAA-ATPase vacuolar protein sorting 4a (Vps4a), in regulating myocardial autophagy remains unclear. In the present study, cardiomyocyte-specific Vps4a knockout mice were generated by crossing Vps4aflox/flox (Vps4afl/fl) with Myh6-cre transgenic mice. As a result, we observed a partially dilated left ventricular (LV) chamber, a significant increase in heart weight to body weight ratio (HW/BW), and heart weight to tibial length ratio (HW/TL), hypertrophic cardiomyopathy and early lethality starting at 3 months of age. Hematoxylin-eosin (HE), immunofluorescence assay (IFA), and Western blot (WB) revealed autophagosome accumulation in cardiomyocytes. A transcriptome-based analysis and autophagic flux tracking by AAV-RFP-GFP-LC3 showed that the autophagic flux was blocked in Vps4a knockout cardiomyocytes. In addition, we provided in vitro evidence demonstrating that Vps4a and LC3 were partially co-localized in cardiomyocytes, and the knockdown of Vps4a led to the accumulation of autophagosomes in cardiomyocytes. Similarly, the transfection of cardiomyocytes with adenovirus (Adv) mCherry-GFP-LC3 further indicated that the autophagic flux was blocked in cells with deficient levels of Vps4a. Finally, an electron microscope (EM) showed that the compromised sealing of autophagosome blocked the autophagic flux in Vps4a-depleted cardiomyocytes. These findings revealed that Vps4a contributed to the sealing of autophagosomes in cardiomyocytes. Therefore, we demonstrated that Vps4a deletion could block the autophagic flux, leading to the accumulation of degradation substances and compromised cardiac function. Overall, this study provides insights into a new theoretical basis for which autophagy may represent a therapeutic target for cardiovascular diseases.
Keywords: ESCRT; Vps4a; autophagy; heart; heart failure.