Overexpression of enzymatically active human cytosolic and mitochondrial thioredoxin reductase in HEK-293 cells. Effect on cell growth and differentiation.
The mammalian thioredoxin reductases (TrxR) are selenoproteins containing a catalytically active selenocysteine residue (Sec) and are important enzymes in cellular redox control. The cotranslational incorporation of Sec, necessary for activity, is governed by a stem-loop structure in the 3'-untranslated region of the mRNA and demands adequate selenium availability. The complicated translation machinery required for Sec incorporation is a major obstacle in isolating mammalian cell lines stably overexpressing selenoproteins. In this work we report on the development and characterization of stably transfected human embryonic kidney 293 cells that overexpress enzymatically active selenocysteine-containing cytosolic TrxR1 or mitochondrial TrxR2. We demonstrate that the overexpression of selenium-containing TrxR1 results in lower expression and activity of the endogenous selenoprotein glutathione peroxidase and that the activity of overexpressed TrxRs, rather than the protein amount, can be increased by selenium supplementation in the cell growth media. We also found that the TrxR-overexpressing cells grew slower over a wide range of selenium concentrations, which was an effect apparently not related to increased apoptosis nor to fatally altered intracellular levels of reactive oxygen species. Most surprisingly, the TrxR1- or TrxR2-overexpressing cells also induced novel expression of the epithelial markers CK18, CK-Cam5.2, and BerEP4, suggestive of a stimulation of cellular differentiation.
Nalvarte
Ivan
I
Department of Biosciences at Novum, Center for Biotechnology, Karolinska Institutet, SE-141 57 Huddinge, Sweden.
Damdimopoulos
Anastasios E
AE
Nystöm
Christina
C
Nordman
Tomas
T
Miranda-Vizuete
Antonio
A
Olsson
Jerker M
JM
Eriksson
Lennart
L
Björnstedt
Mikael
M
Arnér
Elias S J
ES
Spyrou
Giannis
G
D017209:Apoptosis; D001665:Binding Sites; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D015870:Gene Expression / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000378:metabolism; D006801:Humans; D007668:Kidney; D008928:Mitochondria / Q000201:enzymology; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species; D012643:Selenium / Q000008:administration & dosage; D017279:Selenocysteine / Q000737:chemistry / Q000378:metabolism; D054481:Thioredoxin Reductase 1; D054482:Thioredoxin Reductase 2; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D014162:Transfection
D017382:Reactive Oxygen Species; D017279:Selenocysteine; D005979:Glutathione Peroxidase; C516124:TXNRD1 protein, human; C516127:TXNRD2 protein, human; D054481:Thioredoxin Reductase 1; D054482:Thioredoxin Reductase 2; D013880:Thioredoxin-Disulfide Reductase; D012643:Selenium