Abstract
Recent studies have linked compound heterozygous mutations in ASNA1 to progressive dilated cardiomyopathy and early infantile mortality in humans. However, the specific role of ASNA1 in cardiomyocytes and the molecular mechanisms underlying ASNA1-related cardiomyopathy remain poorly understood. Tail-anchored (TA) proteins, characterized by a single C-terminal transmembrane domain (TMD), require post-translational targeting to intracellular membranes, a process primarily mediated by the evolutionarily conserved Guided Entry of Tail-anchored proteins (GET) pathway in yeast and the Transmembrane Recognition Complex (TRC) pathway in mammals. ASNA1 (also known as TRC40 or GET3) serves as the central ATP-dependent chaperone delivering TA proteins to the endoplasmic reticulum (ER) membrane. To address ASNA1's role in the heart, we generated constitutive and inducible cardiomyocyte-specific Asna1 knockout mouse models. Constitutive Asna1 deletion during embryogenesis caused perinatal lethality with marked ventricular myocardial thinning by embryonic day 16.5, whereas inducible deletion in adult cardiomyocytes led to rapid ventricular dilation, impaired cardiac function, pathological remodeling, and early mortality. Mechanistically, ASNA1 deficiency destabilized the pre-targeting complex and reduced the expression of multiple TA protein substrates, impairing membrane trafficking and protein transport. Transcriptomic analyses revealed compensatory upregulation of genes involved in protein trafficking and Golgi-to-ER transport, reflecting maladaptive responses to disrupted vesicular transport. Collectively, our findings identify ASNA1 as a critical regulator of TA protein stability and vesicular trafficking in cardiomyocytes, whose loss disrupts cardiac proteostasis and contributes to the cardiomyopathy pathogenesis. Our work provides mechanistic insights into ASNA1-related cardiac disease and highlights potential therapeutic targets.