Reduced expression of ATP7B affected by Wilson disease-causing mutations is rescued by pharmacological folding chaperones 4-phenylbutyrate and curcumin.
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 degrees 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.


CONCLUSIONS
These findings might enable novel treatment strategies in WD by directly enhancing the protein expression of mutant ATP7B with residual copper export activity. 1795.).
van den Berghe
Peter V E
PV
Department of Metabolic and Endocrine Diseases, University Medical Center Utrecht, and the Netherlands Metabolomics Center, Utrecht, The Netherlands.
Stapelbroek
Janneke M
JM
Krieger
Elmar
E
de Bie
Prim
P
van de Graaf
Stan F J
SF
de Groot
Reinoud E A
RE
van Beurden
Ellen
E
Spijker
Ellen
E
Houwen
Roderick H J
RH
Berger
Ruud
R
Klomp
Leo W J
LW
D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics*; D002352:Carrier Proteins / Q000737:chemistry; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics*; D045744:Cell Line, Tumor; D003300:Copper / Q000378:metabolism; D000079922:Copper Transport Proteins; D000073840:Copper-Transporting ATPases; D003474:Curcumin / Q000494:pharmacology*; D006527:Hepatolenticular Degeneration / Q000188:drug therapy* / Q000235:genetics; D006801:Humans; D056511:Metallochaperones; D018832:Molecular Chaperones / Q000737:chemistry; D009154:Mutation; D010654:Phenylbutyrates / Q000494:pharmacology*; D011487:Protein Conformation; D017510:Protein Folding / Q000187:drug effects*
C474500:ATOX1 protein, human; D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; D056511:Metallochaperones; D018832:Molecular Chaperones; D010654:Phenylbutyrates; D003300:Copper; C075773:4-phenylbutyric acid; D000251:Adenosine Triphosphatases; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases; D003474:Curcumin