Dysregulation of the Expression of Asparagine-Linked Glycosylation 13 Short Isoform 2 Affects Nephrin Function by Altering Its N-Linked Glycosylation

Teresa Esposito, Giovanni De Stefano, Mafalda Giovanna Reccia, Ilaria Di Lorenzo, Filomena Napolitano, Francesco Scalabrì, Alessia Lombardi, Moin A Saleem, Lyn R Griffiths, Fernando Gianfrancesco

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Abstract

BACKGROUND: N-linked glycosylation, which is a post-translational modification process, plays an important role in protein folding, intracellular trafficking and membrane targeting, as well as in regulating the protein function. Recently, we identified a missense variant (p.T141L) in the short isoform 2 of the X-linked gene asparagine-linked glycosylation 13 (ALG13-is2), which segregated with focal segmental glomerulosclerosis and PCCD in a large Australian pedigree; however, any evidence of its pathogenicity was demonstrated. ALG13 gene encodes, through alternative splicing, 2 glycosyltransferase isoforms, which catalyse the second sugar addition of the highly conserved oligosaccharide precursor in the endoplasmic reticulum (ER). Mutations in the long isoform 1 were associated with epilepsy.

METHODS AND RESULTS: Here, we show a different expression of the 2 isoforms depending on the tissue. Specifically, the long isoform is highly expressed in lungs, ovaries, testes, cerebellum, cortex, retina, pituitary gland, and olfactory bulbs, while the short isoform is highly expressed in mouse podocytes and in human podocyte cell lines, at both mRNA and protein levels. The silencing of ALG13-is2 by specific siRNAs induces an altered N-linked glycosylation pattern of nephrin, as demonstrated by the presence of an additional immunostaining band of about 130 kD. In knock-down cells, immunofluorescence analysis shows perturbed organization of the cytoskeleton and altered localization of nephrin on the cellular membrane. We also demonstrated that the altered pattern of N-linked glycosylation induces an over-expression of binding immunoglobulin protein and calreticulin, suggesting ER stress.

CONCLUSIONS: These results provide preliminary evidence that ALG13-is2 could be an important modifier of renal filtration defects.

Original languageEnglish
Pages (from-to)143-150
Number of pages8
JournalNephron Physiology
Volume136
Early online date9 Feb 2017
DOIs
Publication statusPublished - Jun 2017

Keywords

  • Journal Article

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    Esposito, T., De Stefano, G., Reccia, M. G., Di Lorenzo, I., Napolitano, F., Scalabrì, F., Lombardi, A., Saleem, M. A., Griffiths, L. R., & Gianfrancesco, F. (2017). Dysregulation of the Expression of Asparagine-Linked Glycosylation 13 Short Isoform 2 Affects Nephrin Function by Altering Its N-Linked Glycosylation. Nephron Physiology, 136, 143-150. https://doi.org/10.1159/000455129