Extracellular glutathione peroxidase mRNA and protein in human cell lines.
Extracellular glutathione peroxidase (E-GPx) and cellular glutathione peroxidase (C-GPx) are selenoenzymes encoded by two distinct genes. Using specific immunoprecipitations of [75Se]selenium metabolically labeled human cell lines in culture, it was found that Caco-2, Hep3B, Hep G2, and Caki-2 synthesize C-GPx and E-GPx and secrete E-GPx. HBL-100, BT-20, and MCF-7 synthesize only C-GPx. The relationship between Se status (as determined by C-GPx activity) and E-GPx and C-GPx mRNA steady-state levels was investigated in Hep G2, Caco-2, and Caki-2. The most Se-deficient Hep G2, Caco-2, and Caki-2 cells had 8.7 +/- 2.6, 11.2 +/- 4.9, and 9.4 +/- 5.0%, respectively, of C-GPx activity of the replete cells. The steady-state levels of mRNA were measured by Northern and slot blot hybridization analysis. By Northern analysis, a single band was present at 1.0 and 1.80 kb for C-GPx and E-GPx mRNA, respectively, in all three cell lines. Scanning densitometry of the blots revealed that the most Se-deficient cells had 30-50% C-GPx mRNA and 60-80% E-GPx mRNA of the replete cells. It is concluded that, in addition to previously examined human cell lines, Hep3B and Caco-2 make and secrete E-GPx while HBL-100 and BT-20 do not. The slightly reduced levels of G-GPx and E-GPx mRNA in Se-deficient human cell lines can only partially account for the decreased C-GPx activity in Se-deficient human cell lines.
Avissar
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N
Department of Pediatrics, University of Rochester Medical Center, New York 14642.
Kerl
E A
EA
Baker
S S
SS
Cohen
H J
HJ
D015152:Blotting, Northern; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D005110:Extracellular Space / Q000201:enzymology*; D005979:Glutathione Peroxidase / Q000235:genetics* / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D006801:Humans; D007163:Immunosorbent Techniques; D012333:RNA, Messenger / Q000378:metabolism*; D012643:Selenium / Q000378:metabolism; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D005979:Glutathione Peroxidase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D012643:Selenium