Facilitation of Autophagosome-Lysosome Fusion by LAPTM4A: A Novel Strategy for Attenuating Myocardial Ischemia-Reperfusion Injury

BACKGROUND: Myocardial ischemia-reperfusion (MIR) injury compromises therapeutic effects of revascularization and leads to functional impairment and exacerbation of structural damage in the heart. Limiting the damage caused by MIR is crucial but is still an unmet clinical need because of the complexity of the underlying mechanisms. Increasing evidence suggests that lysosomal autophagy plays a significant regulatory role in MIR injury. The specific mechanisms involved remain to be fully understood. METHODS: We here systematically analyzed the murine MIR model database to screen the potentially protective lysosome-localized proteins against MIR injury. The positive hits were further functionally screened and validated for their capability on autophagy and hypoxia/reoxygenation insults of cardiomyocytes. After exploring the detailed molecular mechanism underlying the protective effects of the target protein, we generated target gene cardiac-specific knockout mice and overexpression mice to verify its function in mouse MIR injury models. RESULTS: LAPTM4A (lysosome-associated protein transmembrane 4 alpha) stood out as a significant protective lysosome-localized protein from the screening. LAPTM4A deficiency significantly heightened the inflammatory response and cell death both in primary cardiomyocytes and in a MIR-induced mouse model. Conversely, LAPTM4A overexpression exerted protective effects on cell viability and myocardial damage. Mechanistically, LAPTM4A interacts with Rubicon (Run domain Beclin1-interacting and cysteine-rich domain-containing protein), hindering its engagement within the Beclin1 complex, resulting in a robust augmentation of autophagic flux and thereby mitigating cardiac damage during reperfusion. It is important to note that Rubicon knockdown markedly reversed the aggravated injury induced by LAPTM4A knockdown, further verifying the effects of LAPTM4A depend on Rubicon. CONCLUSIONS: Our findings screened out and validated that LAPTM4A is a lysosome-localized protein exerting protective effects against MIR injury by facilitating autophagic flux. Targeting LAPTM4A represents a promising therapeutic strategy for mitigating MIR injury.