Downregulation of LAPTM4B Contributes to the Impairment of the Autophagic Flux via Unopposed Activation of mTORC1 Signaling During Myocardial Ischemia/Reperfusion Injury.
Circ Res
; 127(7): e148-e165, 2020 09 11.
Article
en En
| MEDLINE
| ID: mdl-32693673
ABSTRACT
RATIONALE Impaired autophagic flux contributes to ischemia/reperfusion (I/R)-induced cardiomyocyte death, but the underlying molecular mechanisms remain largely unexplored. OBJECTIVE:
To determine the role of LAPTM4B (lysosomal-associated transmembrane protein 4B) in the regulation of autophagic flux and myocardial I/R injury. METHODS ANDRESULTS:
LAPTM4B was expressed in murine hearts but downregulated in hearts with I/R (30 minutes/2 hours) injury and neonatal rat cardiomyocytes with hypoxia/reoxygenation (6 hours/2 hours) injury. During myocardial reperfusion, LAPTM4B-knockout (LAPTM4B-/-) mice had a significantly increased infarct size and lactate dehydrogenase release, whereas adenovirus-mediated LAPTM4B-overexpression was cardioprotective. Concomitantly, LAPTM4B-/- mice showed higher accumulation of the autophagy markers LC3-II (microtubule-associated protein 1A/1B-light chain 3), but not P62, in the I/R heart, whereas they did not alter chloroquine-induced further increases of LC3-II and P62 in both sham and I/R hearts. Conversely, LAPTM4B-overexpression had opposite effects. The hypoxia/reoxygenation-reduced viability of neonatal rat cardiomyocytes, ratio of autolysosomes/autophagosomes, and function of lysosomes were further decreased by LAPTM4B-knockdown but reversed by LAPTM4B-overexpression. Moreover, the LAPTM4B-overexpression-mediated benefits were abolished by knockdown of lysosome-associated membrane protein-2 (an autophagosome-lysosome fusion protein) in vivo and by the autophagy inhibitor bafilomycin A1 in vivo. In contrast, rapamycin (Rapa) successfully restored the impaired autophagic flux in LAPTM4B-/- mice and the subsequent myocardial I/R injury. Mechanistically, LAPTM4B regulated the activity of mTORC1 (mammalian target of rapamycin complex 1) via interacting with mTOR through its EC3 (extracelluar) domain. Thus, mTORC1 was overactivated in LAPTM4B-/- mice, leading to the repression of TFEB (transcription factor EB), a master regulator of lysosomal and autophagic genes, during myocardial I/R. The mTORC1 inhibition or TFEB-overexpression rescued the LAPTM4B-/--induced impairment in autophagic flux and I/R injury, whereas TFEB-knockdown abolished the LAPTM4B-overexpression-mediated recovery of autophagic flux and cardioprotection.CONCLUSIONS:
The downregulation of LAPTM4B contributes to myocardial I/R-induced impairment of autophagic flux via modulation of the mTORC1/TFEB pathway. Graphic Abstract A graphic abstract is available for this article.Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Autofagia
/
Daño por Reperfusión Miocárdica
/
Miocitos Cardíacos
/
Autofagosomas
/
Diana Mecanicista del Complejo 1 de la Rapamicina
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Lisosomas
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Infarto del Miocardio
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
Circ Res
Año:
2020
Tipo del documento:
Article