Abstract
Lysosomes play a central role in regulating autophagy via activation of mammalian target of rapamycin complex 1 (mTORC1). We examined mTORC1 signalling in the lysosomal storage disease nephropathic cystinosis (MIM 219800), in which accumulation of autophagy markers has been previously demonstrated. Cystinosis is caused by mutations in the lysosomal cystine transporter cystinosin and initially affects kidney proximal tubules causing renal Fanconi syndrome, followed by a gradual development of end-stage renal disease and extrarenal complications. Using proximal tubular kidney cells obtained from healthy donors and from cystinotic patients, we demonstrate that cystinosin deficiency is associated with a perturbed mTORC1 signalling, delayed reactivation of mTORC1 after starvation and abnormal lysosomal retention of mTOR during starvation. These effects could not be reversed by treatment with cystine-depleting drug cysteamine. Altered mTORC1 signalling can contribute to the development of proximal tubular dysfunction in cystinosis and points to new possibilities in therapeutic intervention through modulation of mTORC-dependent signalling cascades.
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Acknowledgments
This work was sponsored by the Cystinosis Research Foundation. The authors would like to thank Cell Imaging Core at KU Leuven for providing the equipment for microscopy studies. Elena N. Levtchenko is supported by the Research Foundation - Flanders (FWO Vlaanderen), grant 1801110 N.
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All authors were involved in the conception, design, and performance, or analysis and interpretation of data. EAI drafted the manuscript, and all authors critically revised it for intellectual content and agreed to its submission to JIMD.
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This work was sponsored by the Cystinosis Research Foundation. Elena N. Levtchenko is supported by the Research Foundation - Flanders (FWO Vlaanderen), grant 1801110 N. The authors confirm independence from the sponsors; the content of the article has not been influenced by the sponsors.
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The current study is in accordance with the institutional ethical guidelines for obtaining human cell lines for research and was approved by the corresponding ethical committee at University Hospitals Leuven.
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Communicated by: Eva Morava
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Supplementary Figure 1
Effect of cyteamine treatment on cystine concentrations and viability of ciPTEC cells. A) Cystine measurements (nmol/mg protein) in the studied cystinotic ciPTEC cell lines without and with the addition of 100 μM of cysteamine for 24 h. B) Cell viability of cysteamine treated ciPTEC cystinotic and control cell lines expressed as percentage of average absorbance of the corresponding cell lines without cysteamine traetment. (TIF 172 kb)
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Ivanova, E.A., van den Heuvel, L.P., Elmonem, M.A. et al. Altered mTOR signalling in nephropathic cystinosis. J Inherit Metab Dis 39, 457–464 (2016). https://doi.org/10.1007/s10545-016-9919-z
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DOI: https://doi.org/10.1007/s10545-016-9919-z