Perturbation of copper (Cu) homeostasis and expression of Cu-binding proteins in cadmium-resistant lung fibroblasts.
To probe mechanisms of cadmium (Cd) damage to the lung extracellular matrix (ECM), we developed Cd-resistant (CdR) rat lung fibroblasts (RFL6) by incubation with graded concentrations of Cd. CdR cells downregulated lysyl oxidase (LO), a copper (Cu)-dependent enzyme essential for crosslinking of collagen and elastin in the ECM, in conjunction with upregulation of other Cu-binding proteins including Cu,Zn-superoxide dismutase (SOD1), copper chaperone for SOD1 (CCS1), metallothionein (MT), and Menkes P-type ATPase (ATP7A), a Cu transporter in the membrane of the Golgi apparatus, as well as gamma-glutamylcysteine synthetase (gamma-GCS), an enzyme for glutathione biosynthesis. Reduction and loss of cytoplasmic distribution of LO in CdR cells were accompanied by its dislocation with the Menkes P-type ATPase and the endoplasmic reticulum marker. CdR cells displayed a defect in LO catalytic activity but an enhancement in Cu,Zn-SOD catalytic activity consistent with the protein expression levels of these enzymes. Although long-term Cd exposure of cells enhanced the Menkes P-type ATPase protein expression, actually, it reduced Cu-dependent catalytic activity of this enzyme in parallel with the deficiency of LO. The low level of 64Cu bound to the LO fraction and the high level of 64Cu bound to the MT fraction provide direct evidence for limitation of Cu bioavailability for LO existing in the CdR cells. These results suggest that downregulation of LO is linked with upregulation of other Cu-binding proteins and with alteration in Cu homeostasis in the CdR phenotype.
Chou
Denise K
DK
Department of Biochemistry, Boston University School of Medicine, MA 02118, USA.
Zhao
Yinzhi
Y
Gao
Song
S
Chou
Iih-Nan
IN
Toselli
Paul
P
Stone
Phillip
P
Li
Wande
W
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D027682:Cation Transport Proteins / Q000378:metabolism; D002460:Cell Line; D003300:Copper / Q000378:metabolism*; D000073840:Copper-Transporting ATPases; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004361:Drug Tolerance; D004785:Environmental Pollutants / Q000633:toxicity*; D005109:Extracellular Matrix; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D008168:Lung / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008668:Metallothionein / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D015854:Up-Regulation
D015415:Biomarkers; D027682:Cation Transport Proteins; C491961:Ccs protein, rat; D004785:Environmental Pollutants; D018832:Molecular Chaperones; D002104:Cadmium; D003300:Copper; D008668:Metallothionein; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D008249:Protein-Lysine 6-Oxidase; D000251:Adenosine Triphosphatases; D005721:Glutamate-Cysteine Ligase; C486202:Atp7a protein, rat; D000073840:Copper-Transporting ATPases