Mitochondrial turnover is required for proper cellular function. Both mitochondrial biogenesis an... more Mitochondrial turnover is required for proper cellular function. Both mitochondrial biogenesis and mitophagy are impaired in several degenerative and age-related diseases. The search for mitophagy activators recently emerged as a new therapeutical approach; however, there is a lack in suitable tools to follow mitochondrial turnover in a high-throughput manner. We demonstrate that the fluorescent protein, MitoTimer, is a reliable and robust probe to follow mitochondrial turnover. The screening of 15 000 small molecules led us to two chemically-related benzothiophenes that stimulate basal mitophagy in the beta-cell line, INS1. Enhancing basal mitophagy was associated with improved mitochondrial function, higher Complex I activity and Complex II and III expressions in INS1 cells, as well as better insulin secretion performance in mouse islets. The possibility of further enhancing mitophagy in the absence of mitochondrial stressors points to the existence of a ‘basal mitophagy spare cap...
A sharp increase in mitochondrial Ca2+ marks the activation of the brown adipose tissue (BAT) the... more A sharp increase in mitochondrial Ca2+ marks the activation of the brown adipose tissue (BAT) thermogenesis, yet the mechanisms preventing Ca2+ deleterious effects are poorly understood. Here, we show that adrenergic stimulation of BAT activates a PKA-dependent mitochondrial Ca2+ extrusion via the mitochondrial Na+/Ca2+ exchanger, NCLX. Adrenergic stimulation of NCLX-ablated brown adipocytes (BA) induces a profound mitochondrial Ca2+ overload and impaired uncoupled respiration. Core body temperature, PET imaging and VO2 measurements confirm a BAT specific thermogenic defect in NCLX-null mice. We show that mitochondrial Ca2+ overload induced by adrenergic stimulation of NCLX-null BAT, triggers the opening of the mitochondrial permeability transition pore (mPTP), leading to remarkable mitochondrial swelling, Cytochrome c release and cell death in BAT. However, treatment with mPTP inhibitors rescue mitochondrial respiratory function and thermogenesis in NCLX-null BA, in vitro and in vi...
In pancreatic β-cells, liver hepatocytes, and cardiomyocytes, chronic exposure to high levels of ... more In pancreatic β-cells, liver hepatocytes, and cardiomyocytes, chronic exposure to high levels of fatty acids (lipotoxicity) inhibits autophagic flux and concomitantly decreases lysosomal acidity. Whether impaired lysosomal acidification is causally inhibiting autophagic flux and cellular functions could not, up to the present, be determined because of the lack of an approach to modify lysosomal acidity. To address this question, lysosome-localizing nanoparticles are described that, upon UV photoactivation, enable controlled acidification of impaired lysosomes. The photoactivatable, acidifying nanoparticles (paNPs) demonstrate lysosomal uptake in INS1 and mouse β-cells. Photoactivation of paNPs in fatty acid-treated INS1 cells enhances lysosomal acidity and function while decreasing p62 and LC3-II levels, indicating rescue of autophagic flux upon acute lysosomal acidification. Furthermore, paNPs improve glucose-stimulated insulin secretion that is reduced under lipotoxicity in INS1 c...
Mesenchymal stem cells (MSC) are capable of protecting cells harboring mitochondrial damage. This... more Mesenchymal stem cells (MSC) are capable of protecting cells harboring mitochondrial damage. This protection is associated with the transfer of mitochondria through tunneling nanotubes (TNT) from MSC to the injured cells. In this issue of The EMBO Journal, the group of Anurag Agrawal shows that mitochondrial transfer is dependent on the levels of Miro1, a mitochondrial Rho-GTPase that regulates intercellular mitochondrial movement. Miro1 is the first protein shown to accelerate mitochondrial transfer. Amplifying the mitochondrial transfer phenomenon may allow for the study of the mechanisms that regulate it and contribute to our understanding of its role in disease and aging.
Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative dam... more Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative damage and development of diabetes. To determine the source and fate of depolarized mitochondria, individual mitochondria were photolabeled and tracked through fusion and fission. Mitochondria were found to go through frequent cycles of fusion and fission in a 'kiss and run' pattern. Fission events often generated uneven daughter units: one daughter exhibited increased membrane potential (delta psi(m)) and a high probability of subsequent fusion, while the other had decreased membrane potential and a reduced probability for a fusion event. Together, this pattern generated a subpopulation of non-fusing mitochondria that were found to have reduced delta psi(m) and decreased levels of the fusion protein OPA1. Inhibition of the fission machinery through DRP1(K38A) or FIS1 RNAi decreased mitochondrial autophagy and resulted in the accumulation of oxidized mitochondrial proteins, reduce...
Mitochondrial turnover is required for proper cellular function. Both mitochondrial biogenesis an... more Mitochondrial turnover is required for proper cellular function. Both mitochondrial biogenesis and mitophagy are impaired in several degenerative and age-related diseases. The search for mitophagy activators recently emerged as a new therapeutical approach; however, there is a lack in suitable tools to follow mitochondrial turnover in a high-throughput manner. We demonstrate that the fluorescent protein, MitoTimer, is a reliable and robust probe to follow mitochondrial turnover. The screening of 15 000 small molecules led us to two chemically-related benzothiophenes that stimulate basal mitophagy in the beta-cell line, INS1. Enhancing basal mitophagy was associated with improved mitochondrial function, higher Complex I activity and Complex II and III expressions in INS1 cells, as well as better insulin secretion performance in mouse islets. The possibility of further enhancing mitophagy in the absence of mitochondrial stressors points to the existence of a ‘basal mitophagy spare cap...
A sharp increase in mitochondrial Ca2+ marks the activation of the brown adipose tissue (BAT) the... more A sharp increase in mitochondrial Ca2+ marks the activation of the brown adipose tissue (BAT) thermogenesis, yet the mechanisms preventing Ca2+ deleterious effects are poorly understood. Here, we show that adrenergic stimulation of BAT activates a PKA-dependent mitochondrial Ca2+ extrusion via the mitochondrial Na+/Ca2+ exchanger, NCLX. Adrenergic stimulation of NCLX-ablated brown adipocytes (BA) induces a profound mitochondrial Ca2+ overload and impaired uncoupled respiration. Core body temperature, PET imaging and VO2 measurements confirm a BAT specific thermogenic defect in NCLX-null mice. We show that mitochondrial Ca2+ overload induced by adrenergic stimulation of NCLX-null BAT, triggers the opening of the mitochondrial permeability transition pore (mPTP), leading to remarkable mitochondrial swelling, Cytochrome c release and cell death in BAT. However, treatment with mPTP inhibitors rescue mitochondrial respiratory function and thermogenesis in NCLX-null BA, in vitro and in vi...
In pancreatic β-cells, liver hepatocytes, and cardiomyocytes, chronic exposure to high levels of ... more In pancreatic β-cells, liver hepatocytes, and cardiomyocytes, chronic exposure to high levels of fatty acids (lipotoxicity) inhibits autophagic flux and concomitantly decreases lysosomal acidity. Whether impaired lysosomal acidification is causally inhibiting autophagic flux and cellular functions could not, up to the present, be determined because of the lack of an approach to modify lysosomal acidity. To address this question, lysosome-localizing nanoparticles are described that, upon UV photoactivation, enable controlled acidification of impaired lysosomes. The photoactivatable, acidifying nanoparticles (paNPs) demonstrate lysosomal uptake in INS1 and mouse β-cells. Photoactivation of paNPs in fatty acid-treated INS1 cells enhances lysosomal acidity and function while decreasing p62 and LC3-II levels, indicating rescue of autophagic flux upon acute lysosomal acidification. Furthermore, paNPs improve glucose-stimulated insulin secretion that is reduced under lipotoxicity in INS1 c...
Mesenchymal stem cells (MSC) are capable of protecting cells harboring mitochondrial damage. This... more Mesenchymal stem cells (MSC) are capable of protecting cells harboring mitochondrial damage. This protection is associated with the transfer of mitochondria through tunneling nanotubes (TNT) from MSC to the injured cells. In this issue of The EMBO Journal, the group of Anurag Agrawal shows that mitochondrial transfer is dependent on the levels of Miro1, a mitochondrial Rho-GTPase that regulates intercellular mitochondrial movement. Miro1 is the first protein shown to accelerate mitochondrial transfer. Amplifying the mitochondrial transfer phenomenon may allow for the study of the mechanisms that regulate it and contribute to our understanding of its role in disease and aging.
Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative dam... more Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative damage and development of diabetes. To determine the source and fate of depolarized mitochondria, individual mitochondria were photolabeled and tracked through fusion and fission. Mitochondria were found to go through frequent cycles of fusion and fission in a 'kiss and run' pattern. Fission events often generated uneven daughter units: one daughter exhibited increased membrane potential (delta psi(m)) and a high probability of subsequent fusion, while the other had decreased membrane potential and a reduced probability for a fusion event. Together, this pattern generated a subpopulation of non-fusing mitochondria that were found to have reduced delta psi(m) and decreased levels of the fusion protein OPA1. Inhibition of the fission machinery through DRP1(K38A) or FIS1 RNAi decreased mitochondrial autophagy and resulted in the accumulation of oxidized mitochondrial proteins, reduce...
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Papers by Guy Las