Abstract
Differentiation is critical for cell fate decisions, but the signals involved remain unclear. The kidney proximal tubule (PT) cells reabsorb disulphide-rich proteins through endocytosis, generating cystine via lysosomal proteolysis. Here we report that defective cystine mobilization from lysosomes through cystinosin (CTNS), which is mutated in cystinosis, diverts PT cells towards growth and proliferation, disrupting their functions. Mechanistically, cystine storage stimulates Ragulator-Rag GTPase-dependent recruitment of mechanistic target of rapamycin complex 1 (mTORC1) and its constitutive activation. Re-introduction of CTNS restores nutrient-dependent regulation of mTORC1 in knockout cells, whereas cell-permeant analogues of L-cystine, accumulating within lysosomes, render wild-type cells resistant to nutrient withdrawal. Therapeutic mTORC1 inhibition corrects lysosome and differentiation downstream of cystine storage, and phenotypes in preclinical models of cystinosis. Thus, cystine serves as a lysosomal signal that tailors mTORC1 and metabolism to direct epithelial cell fate decisions. These results identify mechanisms and therapeutic targets for dysregulated homeostasis in cystinosis.
| Original language | English |
|---|---|
| Article number | 3994 |
| Number of pages | 21 |
| Journal | Nature communications |
| Volume | 14 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 14 Jul 2023 |
| Externally published | Yes |
Bibliographical note
Funding Information:We thank Nadine Nägele and Aleksandra Kokanovic for technical help, Alessio Cremonesi and Benjamin Klormann for cystine measurements, and the Center for Microscopy and Image Analysis at the University of Zurich for providing equipment and confocal microscopy assistance, as well as the Functional Genomics Center at the University of Zurich for providing equipment and assistance with sample preparation and mass spectrometry-based analyses. We thank V. Berno, M. Stagi, R. Zoncu, C.W. Li, P. Nanni, S. Streb, and A. Othman for their advice and constructive suggestions, and A. Hall and I. Sakhi for providing the LysoTracker dye. We also acknowledge Euro-BioImaging ( www.eurobioimaging.eu ) for providing access to imaging technologies and services via the Italian Node (ALEMBIC, Milan, Italy). We are grateful to the Cystinosis Research Foundation [Irvine, CA, USA; project grants CRFS-2017-007 (O.D. and A.L.), CRFS-2020-005 (O.D. and A.L.) and CRFS 2022-003 (O.D. and M.B.)], the Swiss National Science Foundation (project grant 310030_189044 to O.D. and project grant 310030_215715 to A.L.), the University Research Priority Program of the University of Zurich (URPP) ITINERARE—Innovative Therapies in Rare Diseases (O.D. and A.L.) and TrainCKDis funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 860977 (O.D.).
Publisher Copyright:
© 2023, The Author(s).