ATL-derived factor (ADF), an IL-2 receptor/Tac inducer homologous to thioredoxin; possible involvement of dithiol-reduction in the IL-2 receptor induction

Immunohistochemical localization of adult T-cell leukaemia-derived factor, a human thioredoxin homologue, in human fetal tissues

An immunohistochemical study of the expression of adult T-cell leukaemia-derived factor (ADF), a human thioredoxin homologue, was performed using a rabbit antibody against the C-terminal peptides of ADF. Tissues were obtained from human fetuses between 9 and 23 weeks of gestation. It was revealed that ADF was widely distributed in different organs and tissues during the fetal period. The ADF antibody reacted selectively with medullary cells of the thymus, lung epithelium, the epithelium of the digestive tract, hepatocytes, bladder epithelium, peripheral nerve cells, hair follicles, sebaceous glands, osteoblasts and the proximal tubules of the kidney. It also reacted with cells destined to differentiate into ciliated cells in the fallopian tube and efferent ductules of the testis, interstitial cells in the ovary, Leydig cells of the testis, and dendritic cells in the spleen and lymph nodes. This is the first report on the thioredoxin system in human cells during the early fetal period. The selectivity of ADF staining in fetal tissues suggests that, during early fetal life, ADF expression correlates well with the cellular function of certain tissues.

Isolation and characterization of human thioredoxin-encoding genes

Thioredoxin (Trx) has recently been demonstrated to be an essential component of the early pregnancy factor activity of pregnancy serum. Here, we report the structure and sequence of human Trx-encoding genes (Trx) by analysis of genomic clones. The Trx gene extends over 13 kb and consists of five exons encoding a 12-kDa protein. A 700-bp fragment upstream from the start codon functions as a promoter when inserted in front of a human growth hormone-encoding reporter gene in tissue-culture cells. This promoter region is very G + C rich and does not contain a classical TATA or CCAAT box, but has three consensus sequences for high-affinity Sp1 binding. Southern analysis demonstrated the presence of several Trx genes in the human genome. The number includes at least one inactive copy as shown by the isolation and sequencing of an inactive pseudogene.

A genetic tool used to identify thioredoxin as a mediator of a growth inhibitory signal

Loss of sensitivity to growth inhibitory polypeptides is likely to be one of the events that participates in the formation of some tumors and might be caused by inactivation or loss of the genetic elements that transduce these extracellular signals. The isolation of such a gene was achieved by randomly inactivating genes by an anti-sense complementary DNA expression library followed by direct selection for growth in the presence of an inhibitory polypeptide. Thus, a gene whose inactivation conveyed growth resistance to interferon-gamma (IFN-gamma) was isolated. Sequence analysis showed complete identity with human thioredoxin, a dithiol reducing agent, implicated here in the IFN-gamma-mediated growth arrest of HeLa cells.

Hepatocyte growth inhibitory factor derived from HTLV-I(+) T cell lines: effect on the epidermal growth factor-dependent proliferation of rat hepatocytes

A human T cell leukemia virus-I infected T cell line, ATL-2, produces an interleukin-2 receptor inducing factor, adult T cell leukemia (ATL)-derived factor (ADF). In the conditioned medium (CM) of ATL-2, we found an inhibitory activity on the epidermal growth factor (EGF)-dependent proliferation of primary cultured rat hepatocytes, measured by cell number and [3H]thymidine incorporation. ATL-2 CM dose-dependently inhibited hepatocyte proliferation. This activity was fractionated by gel filtration at a molecular size of 15,000 to 40,000 and was tentatively called hepatocyte growth inhibitory factor (HGI). Further fractionation with the ion-exchange column indicated that HGI was separable from ADF. Nevertheless, there was a positive correlation between HGI and ADF production, because the HGI activity was also detected in the CM of another ADF producer cell line (HUT102), while no significant HGI activity was detected in the CM of low ADF producer cell lines, ED and MOLT4.

Vaccinia virus encodes a protein with similarity to glutaredoxins

Recently, we have reported the complete nucleotide sequence of vaccinia virus (Goebel, S. J., Johnson, G. P., Perkus, M. E., Davis, S. W., Winslow, J. P., and Paoletti, E. 1990, Virology 179, 247-266). Approximately 2.2 kbp leftward of the large subunit of ribonucleotide reductase resides a 108-amino acid open reading frame, O2L (nt 62,851-62,528) with significant similarity to known glutaredoxins. The deduced amino acid sequence of open reading frame O2L is 28.7% identical to the yeast and Escherichia coli proteins and greater than 40% identical to various mammalian glutaredoxins. Similar patterns of hydrophobicity as well as alpha-helix and beta-sheet potentials suggest that O2L and the glutaredoxins share a similar secondary structure. Furthermore, a common function is inferred by the presence of a highly conserved redox-active site.

Identification of a thioredoxin-related protein associated with plasma membranes

A low molecular weight membrane associated sulphydryl protein was detected on a wide range of nucleated cells when [14C]-iodoacetamide was used as a probe. This protein was extracted from THP-1 monocytes, purified to homogeneity and its isoelectric point, Mr and N-terminal amino acid sequence determined. These were shown to be almost identical to the corresponding values for both human thioredoxin and a Tac interleukin-2 receptor activator, indicating that the protein may be a member of this family and function as an essential growth factor.

Determination of the sequence of the yeast YCL313 gene localized on chromosome III. Homology with the protein disulfide isomerase (PDI gene product) of other organisms

We have determined the nucleotide sequence of the YCL313 gene as part of the YIp5 A1G clone localized on the left arm of chromosome III. This YCL313 gene encodes a protein of 522 amino acids (MW 58.3 kDa) which has large homologies with the human, mouse, chicken, bovine and rat PDI gene products. In these organisms the PDI gene encodes the protein disulfide isomerase (EC 5.3.4.1) also called S-S rearrangase, an enzyme that catalyses the rearrangements of S-S bonds in proteins. This enzyme is probably involved in protein folding within the lumen of the endoplasmic reticulum. These sequence homologies suggest that YCL313 is the yeast equivalent of the PDI gene. Gene disruption of YCL313 leads to a lethal phenotype indicating that this gene is essential for cell survival.

Role of ATL-derived factor (ADF) in the normal and abnormal cellular activation: involvement of dithiol related reduction

HTLV-I transformed T cells not only express a large number of interleukin-2 receptors (IL-2R/p55(Tac], but also produce an IL-2R/Tac inducer named ATL-derived factor (ADF). We have cloned the ADF cDNA and found that ADF production in human lymphocytes can be enhanced by cellular activators such as mitogens or phorbol esters. Recombinant ADF produced by E. coli was shown to have growth-promoting activity in combination with interleukin-2 or suboptimal mitogenic stimuli on several lymphoid cells including human PBMCs, besides the originally reported IL-2R/Tac inducing activity. Homology analysis revealed an unexpected structural relationship between ADF and dithiol-reducing enzyme, thioredoxin, which had been characterized originally in prokaryotic system. Recombinant ADF also has a reducing activity, suggesting the presence of still unknown features of ADF action in vivo. The requirement of dithiol reduction in the biological activities of ADF, together with the possible involvement of ADF production in the normal and abnormal activation of human cells are discussed.

Macrophages regulate intracellular glutathione levels of lymphocytes. Evidence for an immunoregulatory role of cysteine

Macrophages consume cystine and generate approximately equivalent amounts of acid-soluble thiol. Stimulation of macrophages with bacterial lipopolysaccharide (LPS) or tumor necrosis factor (TNF) strongly augments the amount of thiol released into the culture supernatant. Cysteine constitutes most of the acid-soluble thiol. The intracellular glutathione level and the DNA synthesis activity in mitogenically stimulated lymphocytes are strongly increased by either exogenously added cysteine, or (syngeneic) macrophages. This cysteine dependency is observed even in the presence of relatively high extracellular cystine concentration as they occur in the blood plasma. The extracellular cysteine concentration also has a strong influence on the intracellular glutathione concentration, viability, and DNA synthesis of cycling T cell clones. Moreover, the cysteine concentration in the culture medium on Day 3 and Day 4 of a 5-day allogeneic mixed lymphocyte culture (i.e., in the late phase of incubation) has a strong influence on the generation of cytotoxic T cell activity, indicating that regulatory effects of cysteine are not restricted to the early phase of the blastogenic response. The inhibitory effect of cysteine starvation on the DNA synthesis of the T cell clones and on the activation of cytotoxic T lymphocytes can be explained essentially by the depletion of intracellular glutathione, since similar effects are observed after treatment with buthionine sulfoximine (BSO), a specific inhibitor of the glutathione biosynthesis. BSO has practically no influence, however, on the N alpha-benzyloxycarbonyl Ne-t-butyloxycarbonyl-L-lysine-thiobenzyl-ester (BLT)-esterase activity and hemolytic activity of the cell lysates from cytotoxic T cells against sheep red blood cells (perforin activity). Taken together, our experiments indicate that cysteine has a regulatory role in the immune system analogous to the hormone-like lymphokines and cytokines. It is released by macrophages at a variable and regulated rate and regulates immunologically relevant functions of lymphocytes in the vicinity.

A novel secretory pathway for interleukin-1 beta, a protein lacking a signal sequence

Interleukin 1 (IL-1) is a major soluble mediator of inflammation. Two human IL-1 genes, alpha and beta, have been isolated, which encode polypeptides with only 20-30% amino acid sequence homology. Unlike most secreted proteins, the two cytokines do not have a signal sequence, an unexpected finding in view of their biological role. Here we show that IL-1 beta is actively secreted by activated human monocytes via a pathway of secretion different from the classical endoplasmic reticulum--Golgi route. Drugs which block the intracellular transport of IL-6, of tumour necrosis factor alpha and of other secretory proteins do not inhibit secretion of IL-1 beta. Secretion of IL-1 beta is blocked by methylamine, low temperature or serum free medium, and is increased by raising the culture temperature to 42 degrees C or by the presence of calcium ionophores, brefeldin A, monensin, dinitrophenol or carbonyl cyanide chlorophenylhydrazone. IL-1 beta is contained in part within intracellular vesicles which protect it from protease digestion. In U937 cells large amounts of IL-1 beta are made but none is secreted. In these cells IL-1 beta is not found in the vesicular fraction, and all the protein is accessible to protease digestion. This suggests that intracellular vesicles that contain IL-1 beta are part of the protein secretory pathway. We conclude that IL-1 beta is released by activated monocytes via a novel mechanism of secretion which may involve translocation of intracellular membranes and is increased by stress conditions.

Evidence for a novel thioredoxin-like catalytic property of gonadotropic hormones

It has been proposed that dithiol-disulfide interchange and oxidation-reduction reactions may play a role in hormone-induced receptor activation. Inspection of the sequences of the gonadotropic hormones revealed a homologous tetrapeptide (Cys-Gly-Pro-Cys) between the beta subunit of lutropin (LH) and the active site of thioredoxin (TD). The beta subunit of follitropin (FSH) has a similar sequence (Cys-Gly-Lys-Cys). Thioredoxin is a ubiquitous protein serving as an electron donor for ribonucleotide reductase, but it also exhibits disulfide isomerase activity. The catalytic activity of TD was assayed by its ability to reactivate reduced and denatured ribonuclease. In this assay, the purified ovine FSH and bovine LH preparations tested were approximately 60 and approximately 300 times, respectively, as active as TD on a molar basis. This heretofore unsuspected catalytic property of FSH and LH may be important in understanding their mechanism of receptor activation and signal transduction.

The gene for human thioredoxin maps on the short arm of chromosome 3 at bands 3p11-p12

Thioredoxin, a ubiquitous enzyme possessing an oxidoreductase activity, has recently been cloned in human. Using in situ chromosomal hybridization with a human thioredoxin cDNA probe, we have precisely localized the thioredoxin gene on chromosome 3 at bands 3p11-p12.