The ubiquitously expressed MURR1 protein is absent in canine copper toxicosis.
OBJECTIVE
Copper toxicosis (CT) in Bedlington terriers is an autosomal recessive disorder characterized by massive lysosomal copper accumulation in livers of affected dogs, and a defect in the biliary excretion of this metal. We propose that MURR1, the gene defective in canine CT, has a role in the regulation of copper excretion into bile during copper overload.


METHODS
Polyclonal antibodies raised against full-length recombinant human MURR1 were used for immunoblot analysis and indirect immunofluorescence studies.


RESULTS
Using Western blot analysis, these antibodies abundantly detected MURR1 as a 23 kDa protein in liver extracts of mice and dogs, but MURR1 was undetectable in the livers of affected Bedlington terriers. MURR1 was also detected in different tissues and cell lines; in cell lines the protein was found both in cytosol and membrane preparations. Consistent with this observation, indirect immunofluorescence staining revealed that in some cells MURR1 was associated with a vesicular compartment diffusely localized throughout the cell.


CONCLUSIONS
The genomic deletion in MURR1 results in complete absence of MURR1 protein. Based on the unanticipated subcellular localization, our results suggest a role for MURR1 in the regulation of vesicular copper sequestration during copper overload.
Department of Metabolic and Endocrinic Diseases, University Medical Center Utrecht, room KC02.069.1, Utrecht University, Lundlaan 6, 3584 EA Utrecht, The Netherlands.
Adriana E M
AE
Klomp
Bart
B
van de Sluis
Leo W J
LW
Klomp
Cisca
C
Wijmenga
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins; D002460:Cell Line; D003300:Copper / Q000378:metabolism*; D004283:Dog Diseases / Q000235:genetics* / Q000378:metabolism; D004285:Dogs; D005260:Female; D017353:Gene Deletion; D030342:Genetic Diseases, Inborn / Q000662:veterinary*; D006801:Humans; D007106:Immune Sera; D008099:Liver / Q000378:metabolism*; D051379:Mice; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D007106:Immune Sera; D011506:Proteins; D003300:Copper