Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome

Maria Carmen Serrano-Perez, Frances C. Tilley, Fabien Nevo, Christelle Arrondel, Selim Sbissa, Gaëlle Martin, K. Tory, Corinne Antignac, Géraldine Mollet

Research output: Contribution to journalArticle

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Abstract

Podocin is a key component of the slit diaphragm in the glomerular filtration barrier, and mutations in the podocin-encoding gene NPHS2 are a common cause of hereditary steroid-resistant nephrotic syndrome. A mutant allele encoding podocin with a p.R138Q amino acid substitution is the most frequent pathogenic variant in European and North American children, and the corresponding mutant protein is poorly expressed and retained in the endoplasmic reticulum both in vitro and in vivo. To better understand the defective trafficking and degradation of this mutant, we generated human podocyte cell lines stably expressing podocinwt or podocinR138Q. Although it has been proposed that podocin has a hairpin topology, we present evidence for podocinR138QN-glycosylation, suggesting that most of the protein has a transmembrane topology. We find that N-glycosylated podocinR138Q has a longer half-life than non-glycosylated podocinR138Q and that the latter is far more rapidly degraded than podocinwt. Consistent with its rapid degradation, podocinR138Q is exclusively degraded by the proteasome, whereas podocinwt is degraded by both the proteasomal and the lysosomal proteolytic machineries. In addition, we demonstrate an enhanced interaction of podocinR138Q with calnexin as the mechanism of endoplasmic reticulum retention. Calnexin knockdown enriches the podocinR138Q non-glycosylated fraction, whereas preventing exit from the calnexin cycle increases the glycosylated fraction. Altogether, we propose a model in which hairpin podocinR138Q is rapidly degraded by the proteasome, whereas transmembrane podocinR138Q degradation is delayed due to entry into the calnexin cycle.

Original languageEnglish
Pages (from-to)4122-4133
Number of pages12
JournalJournal of Biological Chemistry
Volume293
Issue number11
DOIs
Publication statusPublished - Jan 1 2018

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Calnexin
Proteasome Endopeptidase Complex
Endoplasmic Reticulum
Degradation
Glomerular Filtration Barrier
Topology
Glycosylation
Podocytes
Gene encoding
Nephrotic Syndrome
Mutant Proteins
Amino Acid Substitution
Diaphragms
Diaphragm
Half-Life
Substitution reactions
Alleles
Steroids
Cells
Amino Acids

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Serrano-Perez, M. C., Tilley, F. C., Nevo, F., Arrondel, C., Sbissa, S., Martin, G., ... Mollet, G. (2018). Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome. Journal of Biological Chemistry, 293(11), 4122-4133. https://doi.org/10.1074/jbc.RA117.001159

Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome. / Serrano-Perez, Maria Carmen; Tilley, Frances C.; Nevo, Fabien; Arrondel, Christelle; Sbissa, Selim; Martin, Gaëlle; Tory, K.; Antignac, Corinne; Mollet, Géraldine.

In: Journal of Biological Chemistry, Vol. 293, No. 11, 01.01.2018, p. 4122-4133.

Research output: Contribution to journalArticle

Serrano-Perez, MC, Tilley, FC, Nevo, F, Arrondel, C, Sbissa, S, Martin, G, Tory, K, Antignac, C & Mollet, G 2018, 'Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome', Journal of Biological Chemistry, vol. 293, no. 11, pp. 4122-4133. https://doi.org/10.1074/jbc.RA117.001159
Serrano-Perez MC, Tilley FC, Nevo F, Arrondel C, Sbissa S, Martin G et al. Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome. Journal of Biological Chemistry. 2018 Jan 1;293(11):4122-4133. https://doi.org/10.1074/jbc.RA117.001159
Serrano-Perez, Maria Carmen ; Tilley, Frances C. ; Nevo, Fabien ; Arrondel, Christelle ; Sbissa, Selim ; Martin, Gaëlle ; Tory, K. ; Antignac, Corinne ; Mollet, Géraldine. / Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome. In: Journal of Biological Chemistry. 2018 ; Vol. 293, No. 11. pp. 4122-4133.
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