Premium
Reduced expression of ATP7B affected by Wilson disease–causing mutations is rescued by pharmacological folding chaperones 4‐phenylbutyrate and curcumin
Author(s) -
van den Berghe Peter V. E.,
Stapelbroek Janneke M.,
Krieger Elmar,
de Bie Prim,
van de Graaf Stan F. J.,
de Groot Reinoud E. A.,
van Beurden Ellen,
Spijker Ellen,
Houwen Roderick H. J.,
Berger Ruud,
Klomp Leo W. J.
Publication year - 2009
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.23209
Subject(s) - mutant , phenylbutyrate , mutant protein , missense mutation , endoplasmic reticulum , chemical chaperone , chaperone (clinical) , biology , protein folding , er retention , microbiology and biotechnology , biochemistry , gene , chemistry , mutation , medicine , endocrinology , pathology
Abstract Wilson disease (WD) is an autosomal recessive copper overload disorder of the liver and basal ganglia. WD is caused by mutations in the gene encoding ATP7B, a protein localized to the trans ‐Golgi network that primarily facilitates hepatic copper excretion. Current treatment comprises reduction of circulating copper by zinc supplementation or copper chelation. Despite treatment, a significant number of patients have neurological deterioration. The aim of this study was to investigate the possibility that defects arising from some WD mutations are ameliorated by drug treatment aimed at improvement of protein folding and restoration of protein function. This necessitated systematic characterization of the molecular consequences of distinct ATP7B missense mutations associated with WD. With the exception of p.S1363F, all mutations tested (p.G85V, p.R778L, p.H1069Q, p.C1104F, p.V1262F, p.G1343V, and p.S1363F) resulted in reduced ATP7B protein expression, whereas messenger RNA abundance was unaffected. Retention of mutant ATP7B in the endoplasmic reticulum, increased protein expression, and normalization of localization after culturing cells at 30°C, and homology modeling suggested that these proteins were misfolded. Four distinct mutations exhibited residual copper export capacity, whereas other mutations resulted in complete disruption of copper export by ATP7B. Treatment with pharmacological chaperones 4‐phenylbutyrate (4‐PBA) and curcumin, a clinically approved compound, partially restored protein expression of most ATP7B mutants. Conclusion: These findings might enable novel treatment strategies in WD by directly enhancing the protein expression of mutant ATP7B with residual copper export activity. (H EPATOLOGY 2009;50:1783–1795.)