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Autism-associated R451C mutation in neuroligin3 leads to activation of the unfolded protein response in a PC12 Tet-On inducible system.

Published version
Peer-reviewed

Repository DOI


Change log

Authors

Ulbrich, Lisa 
Favaloro, Flores Lietta 
Trobiani, Laura 
Marchetti, Valentina 
Patel, Vruti 

Abstract

Several forms of monogenic heritable autism spectrum disorders are associated with mutations in the neuroligin genes. The autism-linked substitution R451C in neuroligin3 induces local misfolding of its extracellular domain, causing partial retention in the ER (endoplasmic reticulum) of expressing cells. We have generated a PC12 Tet-On cell model system with inducible expression of wild-type or R451C neuroligin3 to investigate whether there is activation of the UPR (unfolded protein response) as a result of misfolded protein retention. As a positive control for protein misfolding, we also expressed the mutant G221R neuroligin3, which is known to be completely retained within the ER. Our data show that overexpression of either R451C or G221R mutant proteins leads to the activation of all three signalling branches of the UPR downstream of the stress sensors ATF6 (activating transcription factor 6), IRE1 (inositol-requiring enzyme 1) and PERK [PKR (dsRNA-dependent protein kinase)-like endoplasmic reticulum kinase]. Each branch displayed different activation profiles that partially correlated with the degree of misfolding caused by each mutation. We also show that up-regulation of BiP (immunoglobulin heavy-chain-binding protein) and CHOP [C/EBP (CCAAT/enhancer-binding protein)-homologous protein] was induced by both mutant proteins but not by wild-type neuroligin3, both in proliferative cells and cells differentiated to a neuron-like phenotype. Collectively, our data show that mutant R451C neuroligin3 activates the UPR in a novel cell model system, suggesting that this cellular response may have a role in monogenic forms of autism characterized by misfolding mutations.

Description

Keywords

ER stress, autism, molecular chaperones, neuroligin, protein misfolding, unfolded protein response, Amino Acid Sequence, Animals, Autistic Disorder, Cell Adhesion Molecules, Neuronal, Endoplasmic Reticulum, Eukaryotic Initiation Factor-2, Humans, Membrane Proteins, Mutation, Nerve Tissue Proteins, PC12 Cells, Phosphorylation, Rats, Sequence Homology, Amino Acid, Transcription, Genetic, Unfolded Protein Response, Up-Regulation

Journal Title

Biochem J

Conference Name

Journal ISSN

0264-6021
1470-8728

Volume Title

473

Publisher

Portland Press Ltd.
Sponsorship
Medical Research Council (G1002610)
Alpha One Foundation (unknown)
Medical Research Council (G0601840)
This work was supported by: Compagnia San Paolo, Sapienza University of Rome and Pasteur Institute - Cenci Bolognetti Foundation grants to ADJ. SJM is a MRC Senior Clinical Research Fellow [MRC Ref G1002610]. This work was also supported by National Institutes of Health grants (MH092906), from the Robert Wood Johnson Foundation to the Child Health Institute of New Jersey [grant #67038] and to the Governor's Council for Medical Research and Treatment of Autism [CAUT14APL028] to D.C.