Biomedical subjects

Jonathan D Gitlin

Publications and source records attributed to Jonathan D Gitlin.

22 records · Page 2Linked to original sources

PubMed2002

Copper chaperones for cytochrome c oxidase and human disease.

Biological processes in living cells are compartmentalized between lipid membranes. Integral membrane proteins often confer specific functions to these compartments and as such have a critical role in cellular metabolism and function. Cytochrome c oxidase is a macromolecular metalloprotein complex essential for the respiratory function of the cell. Elucidating the mechanisms of assembly of cytochrome c oxidase within the inner mitochondrial membrane represents a unique challenge for understanding metalloprotein biosynthesis. Elegant genetic experiments in yeast have defined several proteins required for copper delivery to cytochrome c oxidase. While the precise role of each of these proteins in copper incorporation remains unclear, recent studies have revealed that inherited mutations in two of these proteins can result in severe pathology in human infants in association with cytochrome c oxidase deficiency. Characterization of the molecular pathogenesis of these disorders offers new insights into the mechanisms of cellular copper metabolism and the role of these cytochrome c oxidase copper chaperones in human disease.

Binding Sites↗

PubMed2002

Mutant SOD1 causes motor neuron disease independent of copper chaperone-mediated copper loading.

Copper-mediated oxidative damage is proposed to play a critical role in the pathogenesis of Cu/Zn superoxide dismutase (SOD1)-linked familial amyotrophic lateral sclerosis (FALS). We tested this hypothesis by ablating the gene encoding the copper chaperone for SOD1 (CCS) in a series of FALS-linked SOD1 mutant mice. Metabolic 64Cu labeling in SOD1-mutant mice lacking the CCS showed that the incorporation of copper into mutant SOD1 was significantly diminished in the absence of CCS. Motor neurons in CCS-/- mice showed increased rate of death after facial nerve axotomy, a response documented for SOD1-/- mice. Thus, CCS is necessary for the efficient incorporation of copper into SOD1 in motor neurons. Although the absence of CCS led to a significant reduction in the amount of copper-loaded mutant SOD1, however, it did not modify the onset and progression of motor neuron disease in SOD1-mutant mice. Hence, CCS-dependent copper loading of mutant SOD1 plays no role in the pathogenesis of motor neuron disease in these mouse models.

Amyotrophic Lateral Sclerosis↗

PubMed2002

The copper-iron connection: hereditary aceruloplasminemia.

Hereditary aceruloplasminemia is an autosomal recessive disorder of iron homeostasis due to loss-of-function mutations in the ceruloplasmin gene. Affected individuals may present in adulthood with evidence of hepatic iron overload, diabetes, peripheral retinal degeneration, dystonia, dementia, or dysarthria. Laboratory studies demonstrate microcytic anemia, elevated serum ferritin, and a complete absence of serum ceruloplasmin ferroxidase activity. Consistent with the observed neurologic findings, magnetic resonance imaging reveals iron accumulation within the basal ganglia. Histologic studies detect abundant iron in hepatocytes, reticuloendothelial cells of the liver and spleen, beta cells of the pancreas, and astrocytes and neurons throughout the central nervous system. Characterization of this disorder reveals an essential role for ceruloplasmin in determining the rate of iron efflux from cells with mobilizable iron stores and provides new insights into the mechanisms of human iron metabolism.

Ceruloplasmin↗

PubMed2001

Biochemical analysis of a missense mutation in aceruloplasminemia.

Aceruloplasminemia is an inherited neurodegenerative disease characterized by parenchymal iron accumulation secondary to loss-of-function mutations in the ceruloplasmin gene. To elucidate the molecular pathogenesis of aceruloplasminemia, the biosynthesis of a missense mutant ceruloplasmin (P177R) occurring in an affected patient was examined. Chinese hamster ovary cells transfected with cDNAs encoding secreted and glycosylphosphatidylinositol (GPI)-linked wild-type or P177R human ceruloplasmin were examined by pulse-chase metabolic labeling. These experiments, as well as immunofluorescent analysis and N-linked glycosylation studies, indicate that both the secreted and GPI-linked forms of the P177R mutant are retained in the endoplasmic reticulum (ER). The P177R mutation resides within a novel motif, which is repeated six times in human ceruloplasmin and is conserved in the homologous proteins hephaestin and factor VIII. Analysis of additional mutations in these motifs suggests a critical role for this region in ceruloplasmin trafficking and indicates that substitution of the arginine residue is critical to the ER retention of the P177R mutant. Metabolic labeling of transfected Chinese hamster ovary cells with (64)Cu indicates that the P177R mutant is retained in the ER as an apoprotein and that copper is incorporated into both secreted and GPI-linked ceruloplasmin as a late event in the secretory pathway. Taken together, these studies reveal new insights into the determinants of holoceruloplasmin biosynthesis and indicate that aceruloplasminemia can result from retention of mutant ceruloplasmin within the early secretory pathway.

Amino Acid Sequence↗