Cystinosin, the small GTPase Rab11, and the Rab7 effector RILP regulate intracellular trafficking of the chaperone-mediated autophagy receptor LAMP2A.

Abstract

The lysosomal storage disease cystinosis, caused by cystinosin deficiency, is characterized by cell malfunction, tissue failure, and progressive renal injury despite cystine-depletion therapies. Cystinosis is associated with defects in chaperone-mediated autophagy (CMA), but the molecular mechanisms are incompletely understood. Here, we show CMA substrate accumulation in cystinotic kidney proximal tubule cells. We also found mislocalization of the CMA lysosomal receptor LAMP2A and impaired substrate translocation into the lysosome caused by defective CMA in cystinosis. The impaired LAMP2A trafficking and localization were rescued either by the expression of wild-type cystinosin or by the disease-associated point mutant CTNS-K280R, which has no cystine transporter activity. Defective LAMP2A trafficking in cystinosis was found to associate with decreased expression of the small GTPase Rab11 and the Rab7 effector RILP. Defective Rab11 trafficking in cystinosis was rescued by treatment with small-molecule CMA activators. RILP expression was restored by up-regulation of the transcription factor EB (TFEB), which was down-regulated in cystinosis. Although LAMP2A expression is independent of TFEB, TFEB up-regulation corrected lysosome distribution and lysosomal LAMP2A localization in Ctns-/- cells but not Rab11 defects. The up-regulation of Rab11, Rab7, or RILP, but not its truncated form RILP-C33, rescued LAMP2A-defective trafficking in cystinosis, whereas dominant-negative Rab11 or Rab7 impaired LAMP2A trafficking. Treatment of cystinotic cells with a CMA activator increased LAMP2A localization at the lysosome and increased cell survival. Altogether, we show that LAMP2A trafficking is regulated by cystinosin, Rab11, and RILP and that CMA up-regulation is a potential clinically relevant mechanism to increase cell survival in cystinosis.

• Authors: Jinzhong Zhang, Jennifer L Johnson, Jing He, Gennaro Napolitano, Mahalakshmi Ramadass, Celine Rocca, William B Kiosses, Cecilia Bucci, Qisheng Xin, Evripidis Gavathiotis, Ana María Cuervo, Stephanie Cherqui, Sergio D Catz
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 292 Issue 25 Pg. 10328-10346 (06 23 2017) ISSN: 1083-351X [Electronic] United States
• PMID: 28465352 (Publication Type: Journal Article)
• Copyright: © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Adaptor Proteins, Signal Transducing
• Amino Acid Transport Systems, Neutral
• Enzyme Activators
• Lysosomal-Associated Membrane Protein 2
• Rilp protein, mouse
• cystinosin protein, mouse
• rab7 GTP-Binding Proteins
• rab7 GTP-binding proteins, mouse
• rab11 protein
• rab GTP-Binding Proteins

Topics

• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Amino Acid Substitution
• Amino Acid Transport Systems, Neutral (genetics, metabolism)
• Animals
• Cystinosis (genetics, metabolism, pathology)
• Enzyme Activators (pharmacology)
• Gene Expression Regulation, Enzymologic (drug effects, genetics)
• Lysosomal-Associated Membrane Protein 2 (genetics, metabolism)
• Lysosomes (genetics, metabolism)
• Mice
• Mice, Knockout
• Point Mutation
• Protein Transport (genetics)
• rab GTP-Binding Proteins (biosynthesis, genetics, metabolism)
• rab7 GTP-Binding Proteins