scholarly journals TSC2 regulates lysosome biogenesis via a non-canonical RAGC and TFEB-dependent mechanism

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nicola Alesi ◽  
Elie W. Akl ◽  
Damir Khabibullin ◽  
Heng-Jia Liu ◽  
Anna S. Nidhiry ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Tuberous Sclerosis Complex ◽  
Renal Tumors ◽  
Gtpase Activating Protein ◽  
Mechanistic Target Of Rapamycin ◽  
Lysosome Biogenesis ◽  
Pulmonary Lymphangioleiomyomatosis ◽  
Transcription Factor Eb ◽  
Rag Gtpase ◽  
Dependent Mechanism

AbstractTuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1). Transcription factor EB (TFEB), a master regulator of lysosome biogenesis, is negatively regulated by mTORC1 through a RAG GTPase-dependent phosphorylation. Here we show that lysosomal biogenesis is increased in TSC-associated renal tumors, pulmonary lymphangioleiomyomatosis, kidneys from Tsc2+/− mice, and TSC1/2-deficient cells via a TFEB-dependent mechanism. Interestingly, in TSC1/2-deficient cells, TFEB is hypo-phosphorylated at mTORC1-dependent sites, indicating that mTORC1 is unable to phosphorylate TFEB in the absence of the TSC1/2 complex. Importantly, overexpression of folliculin (FLCN), a GTPase activating protein for RAGC, increases TFEB phosphorylation at the mTORC1 sites in TSC2-deficient cells. Overexpression of constitutively active RAGC is sufficient to relocalize TFEB to the cytoplasm. These findings establish the TSC proteins as critical regulators of lysosomal biogenesis via TFEB and RAGC and identify TFEB as a driver of the proliferation of TSC2-deficient cells.

scholarly journals The Transcription Factor EB Reduces the Intraneuronal Accumulation of the Beta-Secretase-Derived APP Fragment C99 in Cellular and Mouse AD Models

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1204
Author(s):  
Anaïs Bécot ◽  
Raphaëlle Pardossi-Piquard ◽  
Alexandre Bourgeois ◽  
Eric Duplan ◽  
Qingli Xiao ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mouse Model ◽  
Early Stage ◽  
Amyloid Β ◽  
Newborn Mice ◽  
Cellular Models ◽  
In Vivo Experiments ◽  
Lysosome Biogenesis ◽  
Transcription Factor Eb

: Brains that are affected by Alzheimer’s disease (AD) are characterized by the overload of extracellular amyloid β (Aβ) peptides, but recent data from cellular and animal models propose that Aβ deposition is preceded by intraneuronal accumulation of the direct precursor of Aβ, C99. These studies indicate that C99 accumulation firstly occurs within endosomal and lysosomal compartments and that it contributes to early-stage AD-related endosomal-lysosomal-autophagic defects. Our previous work also suggests that C99 accumulation itself could be a consequence of defective lysosomal-autophagic degradation. Thus, in the present study, we analyzed the influence of the overexpression of the transcription factor EB (TFEB), a master regulator of autophagy and lysosome biogenesis, on C99 accumulation occurring in both AD cellular models and in the triple-transgenic mouse model (3xTgAD). In the in vivo experiments, TFEB overexpression was induced via adeno-associated viruses (AAVs), which were injected either into the cerebral ventricles of newborn mice or administrated at later stages (3 months of age) by stereotaxic injection into the subiculum. In both cells and the 3xTgAD mouse model, exogenous TFEB strongly reduced C99 load and concomitantly increased the levels of many lysosomal and autophagic proteins, including cathepsins, key proteases involved in C99 degradation. Our data indicate that TFEB activation is a relevant strategy to prevent the accumulation of this early neurotoxic catabolite.

scholarly journals PtdIns3P controls mTORC1 signaling through lysosomal positioning

2017 ◽  
Vol 216 (12) ◽  
pp. 4217-4233 ◽  
Author(s):  
Zhi Hong ◽  
Nina Marie Pedersen ◽  
Ling Wang ◽  
Maria Lyngaas Torgersen ◽  
Harald Stenmark ◽  
...  
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Amino Acid ◽  
Cell Periphery ◽  
Lipid Kinase ◽  
Mechanistic Target Of Rapamycin ◽  
Mtorc1 Signaling ◽  
Transcription Factor Eb ◽  
Mtorc1 Activation

The mechanistic target of rapamycin complex 1 (mTORC1) is a protein kinase complex that localizes to lysosomes to up-regulate anabolic processes and down-regulate autophagy. Although mTORC1 is known to be activated by lysosome positioning and by amino acid–stimulated production of phosphatidylinositol 3-phosphate (PtdIns3P) by the lipid kinase VPS34/PIK3C3, the mechanisms have been elusive. Here we present results that connect these seemingly unrelated pathways for mTORC1 activation. Amino acids stimulate recruitment of the PtdIns3P-binding protein FYCO1 to lysosomes and promote contacts between FYCO1 lysosomes and endoplasmic reticulum that contain the PtdIns3P effector Protrudin. Upon overexpression of Protrudin and FYCO1, mTORC1–positive lysosomes translocate to the cell periphery, thereby facilitating mTORC1 activation. This requires the ability of Protrudin to bind PtdIns3P. Conversely, upon VPS34 inhibition, or depletion of Protrudin or FYCO1, mTORC1-positive lysosomes cluster perinuclearly, accompanied by reduced mTORC1 activity under nutrient-rich conditions. Consequently, the transcription factor EB enters the nucleus, and autophagy is up-regulated. We conclude that PtdIns3P-dependent lysosome translocation to the cell periphery promotes mTORC1 activation.

scholarly journals A Curcumin Derivative Activates TFEB and Protects Against Parkinsonian Neurotoxicity in Vitro

2020 ◽  
Vol 21 (4) ◽  
pp. 1515 ◽  
Author(s):  
Ziying Wang ◽  
Chuanbin Yang ◽  
Jia Liu ◽  
Benjamin Chun-Kit Tong ◽  
Zhou Zhu ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Animal Models ◽  
Small Molecule ◽  
Therapeutic Target ◽  
Cell Models ◽  
Neuroprotective Effects ◽  
Lysosome Biogenesis ◽  
Transcription Factor Eb ◽  
Curcumin Derivative

TFEB (transcription factor EB), which is a master regulator of autophagy and lysosome biogenesis, is considered to be a new therapeutic target for Parkinson’s disease (PD). However, only several small-molecule TFEB activators have been discovered and their neuroprotective effects in PD are unclear. In this study, a curcumin derivative, named E4, was identified as a potent TFEB activator. Compound E4 promoted the translocation of TFEB from cytoplasm into nucleus, accompanied by enhanced autophagy and lysosomal biogenesis. Moreover, TFEB knockdown effectively attenuated E4-induced autophagy and lysosomal biogenesis. Mechanistically, E4-induced TFEB activation is mainly through AKT-MTORC1 inhibition. In the PD cell models, E4 promoted the degradation of α-synuclein and protected against the cytotoxicity of MPP+ (1-methyl-4-phenylpyridinium ion) in neuronal cells. Overall, the TFEB activator E4 deserves further study in animal models of neurodegenerative diseases, including PD.

scholarly journals Transcription Factor EB Is Selectively Reduced in the Nuclear Fractions of Alzheimer’s and Amyotrophic Lateral Sclerosis Brains

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Hongjie Wang ◽  
Ruizhi Wang ◽  
Shaohua Xu ◽  
Madepalli K. Lakshmana
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Transcription Factor ◽  
Normal Control ◽  
Stage Iv ◽  
Braak Stage ◽  
Master Regulator ◽  
Protein Levels ◽  
Lysosome Biogenesis ◽  
Transcription Factor Eb ◽  
Lateral Sclerosis

Multiple studies suggest that autophagy is strongly dysregulated in Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS), as evidenced by accumulation of numerous autophagosomes, lysosomes with discontinuous membranes, and aggregated proteins in the patients’ brains. Transcription factor EB (TFEB) was recently discovered to be a master regulator of lysosome biogenesis and autophagy. To examine whether aberrant autophagy in AD and ALS is due to alterations in TFEB expression, we systematically quantified the levels of TFEB in these brains by immunoblotting. Interestingly, cytoplasmic fractions of AD brains showed increased levels of normalized (to tubulin) TFEB only at Braak stage IV (61%, p<0.01). Most importantly, normalized (to lamin) TFEB levels in the nuclear fractions were consistently reduced starting from Braak stage IV (52%, p<0.01), stage V (67%, p<0.01), and stage VI (85%, p<0.01) when compared to normal control (NC) brains. In the ALS brains also, nuclear TFEB levels were reduced by 62% (p<0.001). These data suggest that nuclear TFEB is selectively lost in ALS as well as AD brains, in which TFEB reduction was Braak-stage-dependent. Taken together, the observed reductions in TFEB protein levels may be responsible for the widely reported autophagy defects in these disorders.

scholarly journals Structural mechanism of a Rag GTPase activation checkpoint by the lysosomal folliculin complex

Science ◽  
2019 ◽  
Vol 366 (6468) ◽  
pp. 971-977 ◽  
Author(s):  
Rosalie E. Lawrence ◽  
Simon A. Fromm ◽  
Yangxue Fu ◽  
Adam L. Yokom ◽  
Do Jin Kim ◽  
...  
Keyword(s):  
Gtpase Activating Protein ◽  
Interacting Protein ◽  
Lysosomal Function ◽  
Structural Mechanism ◽  
Mechanistic Target Of Rapamycin ◽  
Cryo Electron Microscopy ◽  
Mtorc1 Signaling ◽  
Gtpase Activation ◽  
Guanosine Triphosphatase ◽  
Rag Gtpase

The tumor suppressor folliculin (FLCN) enables nutrient-dependent activation of the mechanistic target of rapamycin complex 1 (mTORC1) protein kinase via its guanosine triphosphatase (GTPase) activating protein (GAP) activity toward the GTPase RagC. Concomitant with mTORC1 inactivation by starvation, FLCN relocalizes from the cytosol to lysosomes. To determine the lysosomal function of FLCN, we reconstituted the human lysosomal FLCN complex (LFC) containing FLCN, its partner FLCN-interacting protein 2 (FNIP2), and the RagAGDP:RagCGTP GTPases as they exist in the starved state with their lysosomal anchor Ragulator complex and determined its cryo–electron microscopy structure to 3.6 angstroms. The RagC-GAP activity of FLCN was inhibited within the LFC, owing to displacement of a catalytically required arginine in FLCN from the RagC nucleotide. Disassembly of the LFC and release of the RagC-GAP activity of FLCN enabled mTORC1-dependent regulation of the master regulator of lysosomal biogenesis, transcription factor E3, implicating the LFC as a checkpoint in mTORC1 signaling.

scholarly journals mTORC1-independent TFEB activation via Akt inhibition promotes cellular clearance in neurodegenerative storage diseases

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Michela Palmieri ◽  
Rituraj Pal ◽  
Hemanth R. Nelvagal ◽  
Parisa Lotfi ◽  
Gary R. Stinnett ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mouse Model ◽  
Neurodegenerative Diseases ◽  
Nuclear Translocation ◽  
Batten Disease ◽  
Storage Diseases ◽  
Mechanistic Target Of Rapamycin ◽  
Lysosomal Diseases ◽  
Transcription Factor Eb ◽  
Cellular Components

Abstract Neurodegenerative diseases characterized by aberrant accumulation of undigested cellular components represent unmet medical conditions for which the identification of actionable targets is urgently needed. Here we identify a pharmacologically actionable pathway that controls cellular clearance via Akt modulation of transcription factor EB (TFEB), a master regulator of lysosomal pathways. We show that Akt phosphorylates TFEB at Ser467 and represses TFEB nuclear translocation independently of mechanistic target of rapamycin complex 1 (mTORC1), a known TFEB inhibitor. The autophagy enhancer trehalose activates TFEB by diminishing Akt activity. Administration of trehalose to a mouse model of Batten disease, a prototypical neurodegenerative disease presenting with intralysosomal storage, enhances clearance of proteolipid aggregates, reduces neuropathology and prolongs survival of diseased mice. Pharmacological inhibition of Akt promotes cellular clearance in cells from patients with a variety of lysosomal diseases, thus suggesting broad applicability of this approach. These findings open new perspectives for the clinical translation of TFEB-mediated enhancement of cellular clearance in neurodegenerative storage diseases.

scholarly journals Regulation of the Transcription Factor EB-PGC1α Axis by Beclin-1 Controls Mitochondrial Quality and Cardiomyocyte Death under Stress

2015 ◽  
Vol 35 (6) ◽  
pp. 956-976 ◽  
Author(s):  
Xiucui Ma ◽  
Haiyan Liu ◽  
John T. Murphy ◽  
Sarah R. Foyil ◽  
Rebecca J. Godar ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Critical Role ◽  
Beclin 1 ◽  
Ros Generation ◽  
Mtor Inhibition ◽  
Lysosome Biogenesis ◽  
Transcription Factor Eb ◽  
Inducible Protein

In cardiac ischemia-reperfusion injury, reactive oxygen species (ROS) generation and upregulation of the hypoxia-inducible protein BNIP3 result in mitochondrial permeabilization, but impairment in autophagic removal of damaged mitochondria provokes programmed cardiomyocyte death. BNIP3 expression and ROS generation result in upregulation of beclin-1, a protein associated with transcriptional suppression of autophagy-lysosome proteins and reduced activation of transcription factor EB (TFEB), a master regulator of the autophagy-lysosome machinery. Partial beclin-1 knockdown transcriptionally stimulates lysosome biogenesis and autophagy via mTOR inhibition and activation of TFEB, enhancing removal of depolarized mitochondria. TFEB activation concomitantly stimulates mitochondrial biogenesis via PGC1α induction to restore normally polarized mitochondria and attenuate BNIP3- and hypoxia-reoxygenation-induced cell death. Conversely, overexpression of beclin-1 activates mTOR to inhibit TFEB, resulting in declines in lysosome numbers and suppression of PGC1α transcription. Importantly, knockdown of endogenous TFEB or PGC1α results in a complete or partial loss, respectively, of the cytoprotective effects of partial beclin-1 knockdown, indicating a critical role for both mitochondrial autophagy and biogenesis in ensuring cellular viability. These studies uncover a transcriptional feedback loop for beclin-1-mediated regulation of TFEB activation and implicate a central role for TFEB in coordinating mitochondrial autophagy with biogenesis to restore normally polarized mitochondria and prevent ischemia-reperfusion-induced cardiomyocyte death.

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