An alternative mitophagy pathway mediated by Rab9 protects the heart against ischemia

Energy stress, such as ischemia, induces mitochondrial damage and death in the heart. Degradation of damaged mitochondria by mitophagy is essential for the maintenance of healthy mitochondria and survival. Here, we show that mitophagy during myocardial ischemia was mediated predominantly through autophagy characterized by Rab9-associated autophagosomes, rather than the well-characterized form of autophagy that is dependent on the autophagy-related 7 (Atg) conjugation system and LC3. This form of mitophagy played an essential role in protecting the heart against ischemia and was mediated by a protein complex consisting of unc-51 like kinase 1 (Ulk1), Rab9, receptor-interacting serine/ thronine protein kinase 1 (Rip1), and dynamin-related protein 1 (Drp1). This complex allowed the recruitment of transGolgi membranes associated with Rab9 to damaged mitochondria through S179 phosphorylation of Rab9 by Ulk1 and S616 phosphorylation of Drp1 by Rip1. Knockin of Rab9 (S179A) abolished mitophagy and exacerbated the injury in response to myocardial ischemia, without affecting conventional autophagy. Mitophagy mediated through the Ulk1/Rab9/Rip1/Drp1 pathway protected the heart against ischemia by maintaining healthy mitochondria

ACBP/DBI protein neutralization confers autophagy-dependent organ protection through inhibition of cell loss, inflammation, and fibrosis

Acyl-coenzyme A (CoA)–binding protein (ACBP), also known as diazepam-binding inhibitor (DBI), is an extracellular feedback regulator of autophagy. Here, we report that injection of a monoclonal antibody neutralizing ACBP/DBI (α-DBI) protects the murine liver against ischemia/reperfusion damage, intoxication by acetaminophen and concanavalin A, and nonalcoholic steatohepatitis caused by methionine/choline-deficient diet as well as against liver fibrosis induced by bile duct ligation or carbon tetrachloride. α-DBI downregulated proinflammatory and profibrotic genes and upregulated antioxidant defenses and fatty acid oxidation in the liver. The hepatoprotective effects of α-DBI were mimicked by the induction of ACBP/DBI-specific autoantibodies, an inducible Acbp/Dbi knockout or a constitutive Gabrg2F77I mutation that abolishes ACBP/DBI binding to the GABAA receptor. Liver-protective α-DBI effects were lost when autophagy was pharmacologically blocked or genetically inhibited by knockout of Atg4b. Of note, α-DBI also reduced myocardium infarction and lung fibrosis, supporting the contention that it mediates broad organ-protective effects against multiple insults.We thank the core facilities of Centre de Recherche des Cordeliers and Gustave Roussy for technical support. G.K. is supported by the Ligue contre le Cancer (equipe labellisee); Agence National de la Recherche (ANR) – Projets blancs; AMMICa US23/CNRS UMS3655; Association pour la Recherche sur le Cancer; Association “Ruban Rose”; Cancerop^ole Ile-de-France; Fondation pour la Recherche Medicale (FRM); a donation by Elior; Equipex Onco-Pheno-Screen; European Joint Programme on Rare Diseases; Gustave Roussy Odyssea, the European Union Horizon 2020 Projects Oncobiome and Crimson (No. 101016923); Fondation Carrefour; Institut National du Cancer; Inserm (Heterogeneite des tumeurs dans leur microenvironnement); Institut Universitaire de France; LabEx Immuno-Oncology (ANR-18- IDEX-0001); the Leducq Foundation; a Cancer Research Accelerating Scientific Platforms and Innovative Research Award from the Mark Foundation;, the Recherche Hospitalo-Universitaire Torino Lumiere; Seerave Foundation; SIRIC Stratified Oncology Cell DNA Repair and Tumor Immune Elimination; and SIRIC Cancer Research and Personalized Medicine. This study contributes to the IdEx Universite de Paris ANR-18-IDEX-0001. G.A. is supported by the FRM. L.S. is supported by Beatriz Galindo senior program of the Spanish Ministry of Universities; Strategic Program “Instituto de Biologıa y Genetica Molecular (IBGM), Junta de Castilla y Leon” (Ref. CCVC8485); and Internationalisation Project of the “Unidad de Excelencia IBGM of Valladolid” (Ref. CL-EI-2021)

The flavonoid 4,4′-dimethoxychalcone promotes autophagy-dependent longevity across species

Ageing constitutes the most important risk factor for all major chronic ailments, including malignant, cardiovascular and neurodegenerative diseases. However, behavioural and pharmacological interventions with feasible potential to promote health upon ageing remain rare. Here we report the identification of the flavonoid 4,4′- dimethoxychalcone (DMC) as a natural compound with anti-ageing properties. External DMC administration extends the lifespan of yeast, worms and flies, decelerates senescence of human cell cultures, and protects mice from prolonged myocardial ischaemia. Concomitantly, DMC induces autophagy, which is essential for its cytoprotective effects from yeast to mice. This pro-autophagic response induces a conserved systemic change in metabolism, operates independently of TORC1 signalling and depends on specific GATA transcription factors. Notably, we identify DMC in the plant Angelica keiskei koidzumi, to which longevity- and health-promoting effects are ascribed in Asian traditional medicine. In summary, we have identified and mechanistically characterised the conserved longevity-promoting effects of a natural anti-ageing drug

Tfeb-Mediated Transcriptional Regulation of Autophagy Induces Autosis during Ischemia/Reperfusion in the Heart

Autosis is a unique form of cell death with characteristic morphological and biochemical features caused by dysregulated autophagy. Autosis is observed in the heart during the late phase of ischemia/reperfusion (I/R), when marked accumulation of autophagosomes is induced. We previously showed that the excessive accumulation of autophagosomes promotes autosis in cardiomyocytes. Although the inhibition of autophagic flux via the upregulation of Rubicon induces the accumulation of autophagosomes during I/R, it appears that additional mechanisms exacerbating autophagosome accumulation are required for the induction of autosis. Here, we show that Tfeb contributes to the induction of autosis during the late phase of I/R in the heart. During myocardial reperfusion, Tfeb is activated and translocated into the nucleus, which in turn upregulates genes involved in autophagy and lysosomal function. The overexpression of Tfeb enhanced cardiomyocyte death induced by a high dose of TAT-Beclin 1, an effect that was inhibited by the downregulation of Atg7. Conversely, the knockdown of Tfeb attenuated high-dose TAT-Beclin1-induced death in cardiomyocytes. Although the downregulation of Tfeb in the heart significantly decreased the number of autophagic vacuoles and inhibited autosis during I/R, the activation of Tfeb activity via 3,4-dimethoxychalcone, an activator of Tfeb, aggravated myocardial injury during I/R. These findings suggest that Tfeb promotes cardiomyocyte autosis during the late phase of reperfusion in the heart

The Role of Alternative Mitophagy in Heart Disease

Autophagy is essential for maintaining cellular homeostasis through bulk degradation of subcellular constituents, including misfolded proteins and dysfunctional organelles. It is generally governed by the proteins Atg5 and Atg7, which are critical regulators of the conventional autophagy pathway. However, recent studies have identified an alternative Atg5/Atg7-independent pathway, i.e., Ulk1- and Rab9-mediated alternative autophagy. More intensive studies have identified its essential role in stress-induced mitochondrial autophagy, also known as mitophagy. Alternative mitophagy plays pathophysiological roles in heart diseases such as myocardial ischemia and pressure overload. Here, this review discusses the established and emerging mechanisms of alternative autophagy/mitophagy that can be applied in therapeutic interventions for heart disorders

Autophagy in Neurodegenerative Diseases: From Mechanism to Therapeutic Approach

Autophagy is a lysosome-dependent intracellular degradation process that allows recycling of cytoplasmic constituents into bioenergetic and biosynthetic materials for maintenance of homeostasis. Since the function of autophagy is particularly important in various stress conditions, perturbation of autophagy can lead to cellular dysfunction and diseases. Accumulation of abnormal protein aggregates, a common cause of neurodegenerative diseases, can be reduced through autophagic degradation. Recent studies have revealed defects in autophagy in most cases of neurodegenerative disorders. Moreover, deregulated excessive autophagy can also cause neurodegeneration. Thus, healthy activation of autophagy is essential for therapeutic approaches in neurodegenerative diseases and many autophagy-regulating compounds are under development for therapeutic purposes. This review describes the overall role of autophagy in neurodegeneration, focusing on various therapeutic strategies for modulating specific stages of autophagy and on the current status of drug development

Tfeb-Mediated Transcriptional Regulation of Autophagy Induces Autosis during Ischemia/Reperfusion in the Heart

Autosis is a unique form of cell death with characteristic morphological and biochemical features caused by dysregulated autophagy. Autosis is observed in the heart during the late phase of ischemia/reperfusion (I/R), when marked accumulation of autophagosomes is induced. We previously showed that the excessive accumulation of autophagosomes promotes autosis in cardiomyocytes. Although the inhibition of autophagic flux via the upregulation of Rubicon induces the accumulation of autophagosomes during I/R, it appears that additional mechanisms exacerbating autophagosome accumulation are required for the induction of autosis. Here, we show that Tfeb contributes to the induction of autosis during the late phase of I/R in the heart. During myocardial reperfusion, Tfeb is activated and translocated into the nucleus, which in turn upregulates genes involved in autophagy and lysosomal function. The overexpression of Tfeb enhanced cardiomyocyte death induced by a high dose of TAT-Beclin 1, an effect that was inhibited by the downregulation of Atg7. Conversely, the knockdown of Tfeb attenuated high-dose TAT-Beclin1-induced death in cardiomyocytes. Although the downregulation of Tfeb in the heart significantly decreased the number of autophagic vacuoles and inhibited autosis during I/R, the activation of Tfeb activity via 3,4-dimethoxychalcone, an activator of Tfeb, aggravated myocardial injury during I/R. These findings suggest that Tfeb promotes cardiomyocyte autosis during the late phase of reperfusion in the heart

Comprehensive autophagy evaluation in cardiac disease models

International audienceAutophagy is a highly conserved recycling mechanism essential for maintaining cellular homeostasis. The pathophysiological role of autophagy has been explored since its discovery 50 years ago, but interest in autophagy has grown exponentially over the last years. Many researchers around the globe have found that autophagy is a critical pathway involved in the pathogenesis of cardiac diseases. Several groups have created novel and powerful tools for gaining deeper insights into the role of autophagy in the aetiology and development of pathologies affecting the heart. Here, we discuss how established and emerging methods to study autophagy can be used to unravel the precise function of this central recycling mechanism in the cardiac system