ABSTRACT
Aceruloplasminemia is an autosomal recessive neurodegenerative disease characterized by iron accumulation in the brain as well as visceral organs. It is a loss-of-function disorder caused by mutations in the ceruloplasmin gene. Clinically, this disease consists of the triad of adult-onset neurological disease, retinal degeneration and diabetes mellitus. Massive iron accumulation and extensive loss of neurons are observed in the basal ganglia. The elevated iron concentration is associated with increased lipid peroxidation in the brains of aceruloplasminemia patients. Enlarged or deformed astrocytes and spheroid-like globular structures are characteristic neuropathological findings in aceruloplasminemia. Moreover, deformed astrocytes and globular structures react positively to anti-4-hydroxynonenal antibody, suggesting that increased oxidative stress is involved in neuronal cell death in aceruloplasminemia brain. More than 30 aceruloplasminemia-causing mutations in the ceruloplasmin gene have been identified. We examined the biosynthesis of two missense ceruloplasmin proteins that result from a Japanese P177R mutation and a Dutch G631R mutation, using Chinese hamster ovary cell expression system. The P177R mutant protein is retained in the endoplasmic reticulum. The G631R mutant protein, predicted to alter the interactions at a single type I copper-binding site, prevented incorporation of copper into apoceruloplasmin and resulted in the synthesis and secretion only of apoceruloplasmin. Molecular analysis of missense mutations showed different structure-function relationships in ceruloplasmin protein. The investigation of mutant ceruloplasmin reveals new insights into molecular pathogenesis of aceruloplasminemia as well as biosynthesis, trafficking, and function of ceruloplasmin.
Subject(s)
Animals , Cricetinae , Humans , Ceruloplasmin/genetics , Iron Metabolism Disorders/complications , Mutation, Missense/genetics , Neurodegenerative Diseases/etiology , Amino Acid Sequence , Astrocytes/pathology , Brain/metabolism , Brain/pathology , Ceruloplasmin/biosynthesis , Immunohistochemistry , Iron Metabolism Disorders/genetics , Iron Metabolism Disorders/pathology , Lipid Peroxidation , Molecular Sequence Data , Neurodegenerative Diseases/genetics , Neurodegenerative Diseases/pathologyABSTRACT
En 45 recién nacidos a término se encontraron niveles medios de ceruloplasmina, actividad oxidásica y actividad oxidásica específica (actividad por gramo de ceruloplasmina) significativamente menores que en un grupo de 30 adultos (p < 0,001). Se obtuvo una correlación significativa de la ceruloplasmina con la actividad oxidásica tanto en el grupo de adultos (r = 0,934, p < 0,001) como en el de recién nacidos (r = 0,834, p < 0,001). En estos últimos se encontró una correlación significativa de la actividad oxidásica específica con la actividad oxidásica (r = 0,646, p < 0,001). Estos resultados plantean cuestiones de interés sobre la naturaleza de la actividad oxidásica de la ceruloplasmina y el mecanismo de la reacción de oxidación. En los recién nacidos se encontró una correlación negativa de la alfa-fetoproteína con la ceruloplasmina (r = 0,659, p < 0,001) y la actividad oxidásica (r = -0,455, p < 0,005). Se sugiere que en los neonatos la hipoceruloplasminemia sería el resultado de una inmadurez hepática