Document Detail

Endoplasmic reticulum polymers impair luminal protein mobility and sensitize to cellular stress in alpha1-antitrypsin deficiency.
MedLine Citation:
PMID:  23197448     Owner:  NLM     Status:  MEDLINE    
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.
Adriana Ordóñez; Erik L Snapp; Lu Tan; Elena Miranda; Stefan J Marciniak; David A Lomas
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-03-14
Journal Detail:
Title:  Hepatology (Baltimore, Md.)     Volume:  57     ISSN:  1527-3350     ISO Abbreviation:  Hepatology     Publication Date:  2013 May 
Date Detail:
Created Date:  2013-04-23     Completed Date:  2013-07-05     Revised Date:  2014-03-19    
Medline Journal Info:
Nlm Unique ID:  8302946     Medline TA:  Hepatology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2049-60     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 American Association for the Study of Liver Diseases.
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MeSH Terms
Cell Line
Endoplasmic Reticulum Stress / physiology*
Inclusion Bodies / physiology
Models, Animal
Mutation / genetics
Polymers / metabolism*
Proteins / metabolism*
Stress, Physiological / physiology*
Unfolded Protein Response / physiology
alpha 1-Antitrypsin / genetics,  metabolism
alpha 1-Antitrypsin Deficiency / genetics,  metabolism,  physiopathology*
Grant Support
100140//Wellcome Trust; G0601840//Medical Research Council; G0901786//Medical Research Council; GGP11057//Telethon; R01 GM086530/GM/NIGMS NIH HHS; R01GM086530-01/GM/NIGMS NIH HHS
Reg. No./Substance:
0/Polymers; 0/Proteins; 0/alpha 1-Antitrypsin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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