UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Endoplasmic reticulum polymers impair luminal protein mobility and sensitize to cellular stress in alpha1-antitrypsin deficiency.

Ordóñez, A; Snapp, EL; Tan, L; Miranda, E; Marciniak, SJ; Lomas, DA; (2013) Endoplasmic reticulum polymers impair luminal protein mobility and sensitize to cellular stress in alpha1-antitrypsin deficiency. Hepatology , 57 (5) 2049 - 2060. 10.1002/hep.26173. Green open access

[thumbnail of 26173_ftp.pdf]
Preview
PDF
26173_ftp.pdf

Download (2MB)

Abstract

Point mutants of alpha1 -antitrypsin (α1AT) form ordered polymers that are retained as inclusions within the endoplasmic reticulum (ER) of hepatocytes in association with neonatal hepatitis, cirrhosis, and hepatocellular carcinoma. These inclusions cause cell damage and predispose to ER stress in the absence of the classical unfolded protein response (UPR). The pathophysiology underlying this ER stress was explored by generating cell models that conditionally express wild-type (WT) α1AT, two mutants that cause polymer-mediated inclusions and liver disease (E342K [the Z allele] and H334D) and a truncated mutant (Null Hong Kong; NHK) that induces classical ER stress and is removed by ER-associated degradation. Expression of the polymeric mutants resulted in gross changes in the ER luminal environment that recapitulated the changes observed in liver sections from individuals with PI*ZZ α1AT deficiency. In contrast, expression of NHK α1AT caused electron lucent dilatation and expansion of the ER throughout the cell. Photobleaching microscopy in live cells demonstrated a decrease in the mobility of soluble luminal proteins in cells that express E342K and H334D α1AT, when compared to those that express WT and NHK α1AT (0.34 ± 0.05, 0.22 ± 0.03, 2.83 ± 0.30, and 2.84 ± 0.55 μm(2) /s, respectively). There was no effect on protein mobility within ER membranes, indicating that cisternal connectivity was not disrupted. Polymer expression alone was insufficient to induce the UPR, but the resulting protein overload rendered cells hypersensitive to ER stress induced by either tunicamycin or glucose depletion. Conclusion: Changes in protein diffusion provide an explanation for the cellular consequences of ER protein overload in mutants that cause inclusion body formation and α1AT deficiency.

Type: Article
Title: Endoplasmic reticulum polymers impair luminal protein mobility and sensitize to cellular stress in alpha1-antitrypsin deficiency.
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/hep.26173
Publisher version: http://dx.doi.org/10.1002/hep.26173
Language: English
Additional information: © 2012 American Association for the Study of Liver Diseases. Full text made available to UCL Discovery by kind permission of Wiley. PMCID: PMC3871212
Keywords: Animals, Cell Line, Cricetinae, Cricetulus, Endoplasmic Reticulum Stress, Female, Inclusion Bodies, Models, Animal, Mutation, Polymers, Proteins, Stress, Physiological, Unfolded Protein Response, alpha 1-Antitrypsin, alpha 1-Antitrypsin Deficiency
UCL classification: UCL
UCL > Provost and Vice Provost Offices > VP: Health
URI: https://discovery.ucl.ac.uk/id/eprint/1382018
Downloads since deposit
146Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item