RESUMO
It was shown that His3 of human copper transporter 1 (hCtr1) prompts the ATCUN-like Cu(II) coordination for model peptides of the hCtr1 N-terminus. Its high Cu(II) affinity is a potential driving force for the transfer of Cu(II) from extracellular Cu(II) carriers to hCtr1. Having a sequence similar to that of hCtr1, hCtr2 has been proposed as another human copper transporter. However, the N-terminal domain of hCtr2 is much shorter than that of hCtr1, with different copper binding motifs at its N-terminus. Employing a model peptide of the hCtr2 N-terminus, MAMHF-am, we demonstrated that His4 provides a unique pattern of Cu(II) complexes, involving Met sulfurs in their Cu(II) coordination sphere. The affinity of Cu(II) for MAMHF-am is a few orders of magnitude lower than that reported for the hCtr1 model peptides at the extracellular pH of 7.4, suggesting a maximal complementary role of Cu(II) binding to hCtr2 in the import of copper from the extracellular space to the cytoplasm. On the other hand, the ability of the hCtr2 model peptide to capture Cu(II) from amino acids and short peptides (potential degradation products of proteins) at pH 5.0 and the known predominant lysosomal localization of hCtr2 support an important potential role of the Cu(II)-hCtr2 interaction in the recovery of copper from lysosomes.
Assuntos
Proteínas de Transporte de Cátions/química , Cobre/metabolismo , Espaço Extracelular/química , Lisossomos/química , Fragmentos de Peptídeos/metabolismo , Sequência de Aminoácidos , Espaço Extracelular/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Lisossomos/metabolismo , Modelos Moleculares , Fragmentos de Peptídeos/química , Ligação Proteica , Conformação Proteica , Proteínas SLC31RESUMO
The copper transporters
Assuntos
Proteínas de Transporte de Cátions/genética , ATPases Transportadoras de Cobre/genética , Resistencia a Medicamentos Antineoplásicos/genética , Neoplasias Epiteliais e Glandulares/genética , Compostos Organoplatínicos/uso terapêutico , Neoplasias Ovarianas/genética , Polimorfismo de Nucleotídeo Único/genética , Adulto , Idoso , Antineoplásicos/uso terapêutico , Carcinoma Epitelial do Ovário , Transportador de Cobre 1 , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Epiteliais e Glandulares/tratamento farmacológico , Neoplasias Ovarianas/tratamento farmacológico , Proteínas SLC31RESUMO
Ctr1 (copper transporter 1) mediates high-affinity copper uptake. Ctr2 (copper transporter 2) shares sequence similarity with Ctr1, yet its function in mammalian cells is poorly understood. In African green monkey kidney COS-7 cells and rat tissues, Ctr2 migrated as a predominant band of approximately 70 kDa and was most abundantly expressed in placenta and heart. A transiently expressed hCtr2-GFP (human Ctr2-green fluorescent protein) fusion protein and the endogenous Ctr2 in COS-7 cells were mainly localized to the outer membrane of cytoplasmic vesicles, but were also detected at the plasma membrane. Biotinylation of Ctr2 with the membrane-impermeant reagent sulfo-NHS-SS-biotin [sulfosuccinimidyl-2-(biotinamido)ethyl-1,3-dithiopropionate] confirmed localization at the cell surface. Cells expressing hCtr2-GFP hyperaccumulated copper when incubated in medium supplemented with 10 microM CuSO(4), whereas cells depleted of endogenous Ctr2 by siRNAs (small interfering RNAs) accumulated lower levels of copper. hCtr2-GFP expression did not affect copper efflux, suggesting that hCtr2-GFP increased cellular copper concentrations by promoting uptake at the cell surface. Kinetic analyses showed that hCtr2-GFP stimulated saturable copper uptake with a K(m) of 11.0+/-2.5 microM and a K(0.5) of 6.9+/-0.7 microM when data were fitted to a rectangular hyperbola or Hill equation respectively. Competition experiments revealed that silver completely inhibited hCtr2-GFP-dependent copper uptake, whereas zinc, iron and manganese had no effect on uptake. Furthermore, increased copper concentrations in hCtr2-GFP-expressing cells were inversely correlated with copper chaperone for Cu/Zn superoxide dismutase protein expression. Collectively, these results suggest that Ctr2 promotes copper uptake at the plasma membrane and plays a role in regulating copper levels in COS-7 cells.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Membrana Celular/metabolismo , Cobre/metabolismo , Animais , Células COS , Proteínas de Transporte de Cátions/genética , Chlorocebus aethiops , Regulação da Expressão Gênica , Genes Reporter/genética , Humanos , Especificidade de Órgãos , Ratos , Proteínas SLC31RESUMO
To further exploit yeast as a model for cellular aging we have modified the replicative life span assay to force respiration, by replacing glucose with the non-fermentable carbon source glycerol. The growth rates of several different strains varied greatly, with doubling times ranging from 2.7 to 7 h. Life spans of all strains were lower on media containing glycerol than on media containing glucose. However, supplementation of glycerol-containing media with copper resulted in increases in life span of between 17 and 72%; life spans equivalent to or beyond those obtained on glucose media. Addition of copper to glucose medium had no effect on life span. Microarray analysis showed that genes responsible for high affinity import of copper display reduced expression upon addition of copper, while most genes showed no change in expression. No differences in growth rate, oxygen uptake, or the levels of subunit II of the copper-containing cytochrome c oxidase were found between cultures of yeast grown with or without copper supplementation. Copper supplementation greatly extended the life span of sod1 and sod2 strains, suggesting that addition of copper may reduce the generation of superoxide. Forcing yeast to respire places an emphasis on mitochondrial function and may aid in the identification of factors involved in aging in other respiratory-dependent organisms.