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Protection of Cystinotic Mice by Kidney-Specific Megalin Ablation Supports an Endocytosis-Based Mechanism for Nephropathic Cystinosis Progression.


ABSTRACT: BACKGROUND:Deletions or inactivating mutations of the cystinosin gene CTNS lead to cystine accumulation and crystals at acidic pH in patients with nephropathic cystinosis, a rare lysosomal storage disease and the main cause of hereditary renal Fanconi syndrome. Early use of oral cysteamine to prevent cystine accumulation slows progression of nephropathic cystinosis but it is a demanding treatment and not a cure. The source of cystine accumulating in kidney proximal tubular cells and cystine's role in disease progression are unknown. METHODS:To investigate whether receptor-mediated endocytosis by the megalin/LRP2 pathway of ultrafiltrated, disulfide-rich plasma proteins could be a source of cystine in proximal tubular cells, we used a mouse model of cystinosis in which conditional excision of floxed megalin/LRP2 alleles in proximal tubular cells of cystinotic mice was achieved by a Cre-LoxP strategy using Wnt4-CRE. We evaluated mice aged 6-9 months for kidney cystine levels and crystals; histopathology, with emphasis on swan-neck lesions and proximal-tubular-cell apoptosis and proliferation (turnover); and proximal-tubular-cell expression of the major apical transporters sodium-phosphate cotransporter 2A (NaPi-IIa) and sodium-glucose cotransporter-2 (SGLT-2). RESULTS:Wnt4-CRE-driven megalin/LRP2 ablation in cystinotic mice efficiently blocked kidney cystine accumulation, thereby preventing lysosomal deformations and crystal deposition in proximal tubular cells. Swan-neck lesions were largely prevented and proximal-tubular-cell turnover was normalized. Apical expression of the two cotransporters was also preserved. CONCLUSIONS:These observations support a key role of the megalin/LRP2 pathway in the progression of nephropathic cystinosis and provide a proof of concept for the pathway as a therapeutic target.

SUBMITTER: Janssens V 

PROVIDER: S-EPMC6830792 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Protection of Cystinotic Mice by Kidney-Specific Megalin Ablation Supports an Endocytosis-Based Mechanism for Nephropathic Cystinosis Progression.

Janssens Virginie V   Gaide Chevronnay Héloïse P HP   Marie Sandrine S   Vincent Marie-Françoise MF   Van Der Smissen Patrick P   Nevo Nathalie N   Vainio Seppo S   Nielsen Rikke R   Christensen Erik I EI   Jouret François F   Antignac Corinne C   Pierreux Christophe E CE   Courtoy Pierre J PJ  

Journal of the American Society of Nephrology : JASN 20190923 11


<h4>Background</h4>Deletions or inactivating mutations of the cystinosin gene <i>CTNS</i> lead to cystine accumulation and crystals at acidic pH in patients with nephropathic cystinosis, a rare lysosomal storage disease and the main cause of hereditary renal Fanconi syndrome. Early use of oral cysteamine to prevent cystine accumulation slows progression of nephropathic cystinosis but it is a demanding treatment and not a cure. The source of cystine accumulating in kidney proximal tubular cells a  ...[more]

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