Parathymosin alpha: a peptide from rat tissues with structural homology to prothymosin alpha.

Abstract

A peptide, parathymosin a, containing %105 amino acid residues, has been isolated from rat thymus, and the sequence of the first 30 residues at the NH2 terminus has been determined. In this region, it shows 43% structural identity with thymosin a, and prothymosin a. The common sequences do not include residues 2-9, which accounts for the poor reactivity of parathymosin a with an antibody directed against this epitope in thymosin a1. Parathymosin a appears to modulate the action of prothymosin a in protecting sensitive strains of mice against opportunistic infection with Candida albicans.We have recently reported (1) a procedure for the isolation from rat thymus of three previously identified peptides, thymosin 834 (2), thymosin 6310 (3), and prothymosin a (4, 5). Prothymosin a, identified as a larger polypeptide containing the thymosin a1 sequence (6) at its NH2 terminus, was shown to account for most, if not all, of the immunoreactivity detected with an antibody directed against the NH2-terminal sequence in thymosin a1 (4).In this paper, we report that the isolation procedure also yields a fourth peptide, named parathymosin a because it shows some structural homology to prothymosin a and because it has a similar size and amino acid composition. Parathymosin a can also be isolated from other rat tissues, and in some tissues, such as liver, kidney, and brain, the concentrations of parathymosin a are much higher than the concentrations of prothymosin a. Preliminary results suggest that parathymosin a may act to modulate the immunoenhancing activity exhibited by prothymosin a.EXPERIMENTAL PROCEDURES Materials. Unless otherwise indicated, materials used were as described (1, 4, 5).Methods. The procedures for processing and extracting tissues and separating peptides from the extracts were as described (4, 5). Briefly, fresh rat thymuses were frozen in liquid N2 and pulverized in the frozen state. The powdered frozen tissue was quickly brought to 95°C-100°C in a relatively large volume of boiling 0.1 M sodium phosphate buffer (pH 7.0) and, after cooling, the suspension was homogenized with a Polytron homogenizer (Brinkmann) and the soluble fraction was collected. The clear extracts were desalted on Sep-Pak C-18 cartridges (Waters Associates), and the peptides were eluted with 1 M HCOOH/0.2 M pyridine, separated by chromatography on a column of Sephacryl S-200, and purified by reversed-phase HPLC (1, 4).Amino acid analyses, automated sequencing of peptides, and isoelectric focusing were carried out as described (4). (10 /11) were dried, hydrolyzed with alkali, and analyzed with fluorescamine (4). For subsequent purification by HPLC, the fractions corresponding to peak a, as indicated by the bar, were pooled and combined with similar fractions from three other gel filtration separations.

Characterization of two thymosins as immune-related genes in common carp (Cyprinus carpio L.)

“…It was reported that the expression of ProTα was higher in proliferative cells than that in quiescent cells. And in adults, the more proliferative tissues exhibited higher levels of ProTα (Haritos et al, 1985). All these studies suggest that carp ProTα may exhibit similar function in carp liver as that in mammals, which needs to be further studied.…”

“…The expression of ProTα b during infection was significantly up-regulated in spleen which was the main peripheral immune organ in carp, followed in kidney, intestine and peripheral blood which were all immune-related organs. Since 1994, ProTα has been reported to inhibit the replication of virus and the reproduction of cancer cells by inducing immune cells (Baxevanis et al, 1994(Baxevanis et al, , 1995Haritos et al, 1985;Romani et al, 2004). Thymosin α1, corresponding to the first 28 amino acid residues of ProTα, was reported to increase the expression of MHC I which presented endogenous peptides to cytotoxic T cells to kill the virally infected cells as well as some cancer cells (Giuliani et al, 2000).…”

“…Tβ isoforms have also been identified from several fishes including trout (Salmo gairdneri) (thymosin β11 and thymosin β12), perch (Perca fluviatilis ) (thymosin β12) and paradise fish (Macropodus opercularis) (β-thymosin) (Anathy et al, 2003;Erickson-Viitanen and Horecker, 1984;Low et al, 1992). ProTα was reported to inhibit the replication of virus, and it increased the expression of MHC I which presented endogenous peptides to cytotoxic T cells to kill the virally infected cells and some cancer cells (Baxevanis et al, 1994(Baxevanis et al, , 1995Haritos et al, 1985;Romani et al, 2004). A study reported one of the Tβs, Tβ4, was a key activator of NK cell cytotoxicity (Lee et al, 2009).…”

Retrovirus-mediated transfer of prothymosin gene inhibits tumor growth and prolongs survival in murine bladder cancer

“…Furthermore, ProT has been reported to be more effective than thymosin α1 in the protection of mice infected with Candida albicans, suggesting that the biological activity of ProT is not solely determined by its N-terminal region that includes the thymosin α1 fragment. 3 Bladder cancer, especially presenting as superficial disease, is responsive to immunotherapeutic agents, such as BCG, and may represent a good candidate for immunological intervention. Indeed, in the murine MBT-2 bladder tumor model, irradiated, interleukin-2 or granulocyte-macrophage colony-stimulating factor genemodified MBT-2 cells were capable of curing about half of the mice bearing wild-type MBT-2 tumors and engendered protective immunological memory in the cured mice.…”

Macromolecular Translocation Inhibitor II (Zn2+-binding Protein, Parathymosin) Interacts with the Glucocorticoid Receptor and Enhances Transcription in Vivo

“…Haritos et al (10,14) initially isolated MTI-II from rat thymus as parathymosin, a homolog of the protein prothymosin ␣ (PT␣). MTI-II/ parathymosin shares 46% identity with PT␣ (14), but the two proteins show a reciprocal tissue distribution in rats (10,12).…”