Related Experiment Video
Updated: May 5, 2026

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins
Published on: January 18, 2019
Nephrin missense mutations: induction of endoplasmic reticulum stress and cell surface rescue by reduction in
Tetyana Drozdova1, Joan Papillon, Andrey V Cybulsky
1Department of Medicine, McGill University Health Centre, McGill University Montreal, Quebec, Canada.
Abstract:
Nephrin, an important component of the podocyte filtration slit diaphragm, plays a key role in the maintenance of glomerular permselectivity. Mutations in nephrin lead to proteinuria and congenital nephrotic syndrome. Nephrin undergoes posttranslational modifications in the endoplasmic reticulum (ER) prior to export to the plasma membrane. We examined the effects of human nephrin disease-associated missense mutations on nephrin folding in the ER and on cellular trafficking in cultured cells. Compared with wild-type (WT) nephrin, the mutants showed impaired glycosylation and enhanced association with the ER chaperone, calnexin, as well as accumulation in the ER. Nephrin mutants demonstrated enhanced ubiquitination, and they underwent ER-associated degradation. Certain nephrin mutants did not traffic to the plasma membrane. Expression of nephrin mutants resulted in the stimulation of the activating transcription factor-6 pathway of the unfolded protein response, and an increase in the ER chaperone, Grp94. We treated cells with castanospermine (an inhibitor of glucosidase I) in order to decrease the association of nephrin mutants with calnexin. Castanospermine increased plasma membrane expression of nephrin mutants; however, full glycosylation and signaling activity of the mutants were not restored. Modulation of ER quality control mechanisms represents a potential new approach to development of therapies for proteinuric kidney disease, including congenital nephrotic syndrome.
Related Concept Videos
Export of Misfolded Proteins out of the ER
Regulation of the Unfolded Protein Response
Role of ER in the Secretory Pathway
Components of the secretory pathway
About a third of proteins synthesized in the cell are sorted via the secretory route. They shuffle between different compartments in membrane-bound vesicles until they reach their final destination. The main intracellular compartments involved...
Protein Folding Quality Check in the RER
The Unfolded Protein Response
Nephrotic Syndrome I : Introduction

