A central role for TOR signalling in a yeast model for juvenile CLN3 disease

Bond, Michael; Brown, Rachel E.; Rallis, Charalampos; Bähler, Jürg; Mole, Sara

doi:10.15698/mic2015.12.241

Cited by 14 publications

(14 citation statements)

References 76 publications

(117 reference statements)

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“…Noteworthy, in the brain of Drosophila spin mutants an NCL-like phenotype, characterized by storage of lipofuscin, accumulation of ceramides, age-dependent synaptic dysfunction and progressive neurodegeneration, was reported ( 47 , 48 ), suggesting that impaired ALR and mTORC1 reactivation may contribute to lysosomal/autolysosomal dysfunction in other NCLs. In agreement, downregulation of mTOR signalling and dysfunction in the mTORC1 pathways have been reported in mouse and yeast models of juvenile CLN3 disease, respectively ( 23 , 49 ).…”

Section: Discussionsupporting

confidence: 78%

Loss of CLN7 results in depletion of soluble lysosomal proteins and impaired mTOR reactivation

Danyukova

Ariunbat

Thelen

et al. 2018

Human Molecular Genetics

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Defects in the MFSD8 gene encoding the lysosomal membrane protein CLN7 lead to CLN7 disease, a neurodegenerative lysosomal storage disorder belonging to the group of neuronal ceroid lipofuscinoses. Here, we have performed a SILAC-based quantitative analysis of the lysosomal proteome using Cln7-deficient mouse embryonic fibroblasts (MEFs) from a Cln7 knockout (ko) mouse model. From 3335 different proteins identified, we detected 56 soluble lysosomal proteins and 29 highly abundant lysosomal membrane proteins. Quantification revealed that the amounts of 12 different soluble lysosomal proteins were significantly reduced in Cln7 ko MEFs compared with wild-type controls. One of the most significantly depleted lysosomal proteins was Cln5 protein that underlies another distinct neuronal ceroid lipofuscinosis disorder. Expression analyses showed that the mRNA expression, biosynthesis, intracellular sorting and proteolytic processing of Cln5 were not affected, whereas the depletion of mature Cln5 protein was due to increased proteolytic degradation by cysteine proteases in Cln7 ko lysosomes. Considering the similar phenotypes of CLN5 and CLN7 patients, our data suggest that depletion of CLN5 may play an important part in the pathogenesis of CLN7 disease. In addition, we found a defect in the ability of Cln7 ko MEFs to adapt to starvation conditions as shown by impaired mammalian target of rapamycin complex 1 reactivation, reduced autolysosome tubulation and increased perinuclear accumulation of autolysosomes compared with controls. In summary, depletion of multiple soluble lysosomal proteins suggest a critical role of CLN7 for lysosomal function, which may contribute to the pathogenesis and progression of CLN7 disease.

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Section: Discussionsupporting

confidence: 78%

Loss of CLN7 results in depletion of soluble lysosomal proteins and impaired mTOR reactivation

Danyukova

Ariunbat

Thelen

et al. 2018

Human Molecular Genetics

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“…It is also noteworthy that, like in the other studies on enhanced autophagic flux in models of CLN3 disease, the validated hit compounds identified here are also thought to mediate the promotion of autophagy through mTOR-independent mechanisms, involving IP 3 levels and the regulation of calpain activity [49,59]. However, genetic modifiers of phenotypes in a CLN3 disease yeast model have been reported to strongly converge on Tor signaling, which the authors suggest may be dysfunctional in the absence of the CLN3 protein [60]. Given the important role of the lysosome in regulating mTOR signaling [61][62][63], further studies are warranted to fully delineate the role of mTOR and other pathways affected by loss of CLN3 function and how targeting these pathways will impact CLN3 disease.…”

Section: Discussionsupporting

confidence: 70%

An Autophagy Modifier Screen Identifies Small Molecules Capable of Reducing Autophagosome Accumulation in a Model of CLN3-Mediated Neurodegeneration

Petcherski

Chandrachud

Butz

et al. 2019

Cells

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Alterations in the autophagosomal–lysosomal pathway are a major pathophysiological feature of CLN3 disease, which is the most common form of childhood-onset neurodegeneration. Accumulating autofluorescent lysosomal storage material in CLN3 disease, consisting of dolichols, lipids, biometals, and a protein that normally resides in the mitochondria, subunit c of the mitochondrial ATPase, provides evidence that autophagosomal–lysosomal turnover of cellular components is disrupted upon loss of CLN3 protein function. Using a murine neuronal cell model of the disease, which accurately mimics the major gene defect and the hallmark features of CLN3 disease, we conducted an unbiased search for modifiers of autophagy, extending previous work by further optimizing a GFP-LC3 based assay and performing a high-content screen on a library of ~2000 bioactive compounds. Here we corroborate our earlier screening results and identify expanded, independent sets of autophagy modifiers that increase or decrease the accumulation of autophagosomes in the CLN3 disease cells, highlighting several pathways of interest, including the regulation of calcium signaling, microtubule dynamics, and the mevalonate pathway. Follow-up analysis on fluspirilene, nicardipine, and verapamil, in particular, confirmed activity in reducing GFP-LC3 vesicle burden, while also demonstrating activity in normalizing lysosomal positioning and, for verapamil, in promoting storage material clearance in CLN3 disease neuronal cells. This study demonstrates the potential for cell-based screening studies to identify candidate molecules and pathways for further work to understand CLN3 disease pathogenesis and in drug development efforts.

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“…Wild type yeast cells respond to a variety of stresses via interconnected signalling pathways restoring cell homeostasis and integrity. In contrast, cells lacking btn1 are unable to respond to the applied stresses, although the pathways themselves are still functional [102]. Thus, for CLN3 disease at least, neuronal cell death could be triggered by the inability of key signalling pathways to be activated, such as a dysfunctional mTORC1 pathway causing apoptosis through suppression of Akt and consequent induction of the IRE1–JNK pathway [103].…”

Section: Discussionmentioning

confidence: 99%

NCLs and ER: A stressful relationship

Marotta¹,

Tinelli²,

Mole³

2017

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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The Neuronal Ceroid Lipofuscinoses (NCLs, Batten disease) are a group of inherited neurodegenerative disorders with variable age of onset, characterized by the lysosomal accumulation of autofluorescent ceroid lipopigments. The endoplasmic reticulum (ER) is a critical organelle for normal cell function. Alteration of ER homeostasis leads to accumulation of misfolded protein in the ER and to activation of the unfolded protein response. ER stress and the UPR have recently been linked to the NCLs. In this review, we will discuss the evidence for UPR activation in the NCLs, and address its connection to disease pathogenesis. Further understanding of ER-stress response involvement in the NCLs may encourage development of novel therapeutical agents targeting these pathogenic pathways.

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A central role for TOR signalling in a yeast model for juvenile CLN3 disease

Cited by 14 publications

References 76 publications

Loss of CLN7 results in depletion of soluble lysosomal proteins and impaired mTOR reactivation

Loss of CLN7 results in depletion of soluble lysosomal proteins and impaired mTOR reactivation

An Autophagy Modifier Screen Identifies Small Molecules Capable of Reducing Autophagosome Accumulation in a Model of CLN3-Mediated Neurodegeneration

NCLs and ER: A stressful relationship

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