The ubiquitously expressed MURR1 protein is absent in canine copper toxicosis.
BACKGROUND/AIMS: 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.[1]References
- The ubiquitously expressed MURR1 protein is absent in canine copper toxicosis. Klomp, A.E., van de Sluis, B., Klomp, L.W., Wijmenga, C. J. Hepatol. (2003) [Pubmed]
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