Chronic intermittent autophagy inhibition ameliorates Bag3-dependent cardiomyopathy

ABSTRACT: Mutations in the Hsp70 co-chaperone Bcl2-associated athanogene 3 (Bag3) result in myofibrillar myopathy and pediatric hypertrophic cardiomyopathy (pHCM) in human patients, but the pathological mechanisms underlying Bag3 dysfunction in the developing heart have remained unclear. Here we show that conditional ablation of Bag3 in cardiomyocytes (CMs) results in progressive cardiomyopathy accompanied by increased autophagic flux and autophagosome accumulation in the early post-natal period. Autophagy inhibition via acute administration of chloroquine (CQ) results in transient accumulation of cardiac proteins in the detergent-insoluble fraction, implying a role for autophagy in the degradation of unfolded proteins in the absence of Bag3 co-chaperone activity. Exacerbated autophagy in Bag3 deficient CMs leads to decreased soluble levels of proteins involved in cardiac contraction and conduction, including the gap junction protein connexin 43 (Cx43). Importantly, chronic CQ treatment during the early post-natal period results in a significant amelioration of the pathological phenotype, with recovered contractile performances and restoration of soluble levels of autophagy-targeted proteins. We therefore conclude that loss of Bag3 in CMs leads to autophagic flux exacerbation and that CQ treatment is relevant to therapeutic strategies for Bag3-dependent pHCM patients.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Heart

SUBMITTER: Johannes Graumann  

LAB HEAD: Johnny Kim

PROVIDER: PXD016095 | Pride | 2024-06-05

REPOSITORIES: Pride