Truncated thioredoxin is a mitogenic cytokine for resting human peripheral blood mononuclear cells and is present in human plasma.
Human thioredoxin (Trx) catalyzes intracellular disulfide reductions but has also co-cytokine activity with interleukins after leaderless secretion. A recombinant truncated form of thioredoxin with the 80 N-terminal residues (Trx80) was purified to homogeneity. We discovered that Trx80 by itself is a potent mitogenic cytokine stimulating growth of resting human peripheral blood mononuclear cells. No effect was seen by Trx, but Trx80 at 50-100 nm induced cell proliferation of human peripheral blood mononuclear cells in serum-free synthetic medium, measured as [(3)H]thymidine incorporation after 72 h, with a maximum effect being comparable with that of 5 units/ml of interleukin-2. Trx80 lacked redox activity, but CD spectra suggested a secondary structure similar to Trx. Reduced Trx80 had an M(r) of 25,000, indicating that it is a dimer in solution. We also developed two different sandwich enzyme-linked immunosorbent assays that distinguish between full-length Trx and Trx80 and determined plasma levels of Trx and Trx80 in blood donors. The levels of Trx80 varied from 2 to 175 ng/ml; in comparison levels of Trx varied from 16 to 55 ng/ml without correlation to Trx80. In conclusion, the naturally occurring Trx80 is a novel mitogenic cytokine for normal resting human blood mononuclear cells.
Pekkari
K
K
Medical Nobel Institute for Biochemistry, Department of Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Gurunath
R
R
Arner
E S
ES
Holmgren
A
A
D002852:Chromatography, Ion Exchange; D002942:Circular Dichroism; D016207:Cytokines / Q000097:blood / Q000302:isolation & purification / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008934:Mitogens / Q000097:blood / Q000302:isolation & purification / Q000502:physiology*; D009000:Monocytes / Q000166:cytology*; D013879:Thioredoxins / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*
D016207:Cytokines; D008934:Mitogens; D013879:Thioredoxins