Point mutations affecting the oligomeric structure of Nm23-H1 abrogates its inhibitory activity on colonization and invasion of prostate cancer cells

In order to identify Nm23-H1's structural motifs influencing its metastasis-inhibitory activity, we transfected DU 145 human prostate carcinoma cells with the expression vector encoding the Nm23-H1 protein with mutations at the following amino acids: serine-44, a phosphorylation site; proline-96, a site corresponding to the k-pn mutation that causes developmental defects in Drosophila; and serine-120, a site of mutation in human neuroblastoma and phosphorylation. Significant decrease in colonization in soft agar and invasiveness of DU 145 cells was observed in the wild type nm23-H1 transfectants, and also in the serine-44 and serine-120 to alanine mutant nm23-H1-transfected cell lines. However, the k-pn type proline-96 to serine (P96S) and neuroblastoma type serine-120 to glycine (S120G) mutations of Nm23-H1 abrogated its inhibitory activity on colonization and invasion. Meanwhile, all of the recombinant mutant Nm23-H1 proteins produced in Escherichia coli exhibited NDP kinase activity levels at the wild type protein, although the P96S and S120G mutant proteins exhibited decreased histidine protein kinase activity and autophosphorylation level, respectively. Interestingly, only two of the mutant recombinant Nm23-H1 proteins examined, P96S and S120G, exhibited reduced hexameric and increased dimeric oligomerization relative to the wild type. These correlative data suggest that the metastasis-suppressing activity of Nm23-H1 may depend on its oligomeric structure, but not on its NDP kinase activity.     

The role of cell membrane in the antiviral effect of interferon

The mechanism of interferon action in human fibroblasts has been studied by use of both antisera to human fibroblast interferon and the antisera to the surface of human fibroblast cell. The anti-interferon serum completely neutralized the antiviral effect of human fibroblast interferon. Interferon antiserum prevented the intracellular antiviral state from developing when added to the medium of the cells in which interferon synthesis had already been induced by poly (I · C). This suggests that development of the antiviral state involves interferon interaction with the external part of the producing cell. Treatment with the serum directed against the surface of human fibroblast cells failed to inhibit the antiviral activity of human interferon in these cells. In addition, the effect of gangliosides on the antiviral activity of human interferon was studied and it was found that human interferon binds to gangliosides and that this interaction leads to inactivation of the antiviral effect of interferon. Pretreatment of human fibroblasts with gangliosides had no effect on the sensitivity of these cells to exogenous interferon.     

Binding of human fibroblast interferon to concanavalin A-agarose. Involvement of carbohydrate recognition and hydrophobic interaction.

Human fibroblast interferon binds to a concanavalin A-agarose (Con A-Sepharose) equilibrated with methyl alpha-D-mannopyranoside, or levan; in contrast, it is only partially retarded on a similar column equilibrated with ethylene glycol. Interferon does not bind, however, to a lectin column equilibrated with both methyl alpha-D-mannopyranoside and ethylene glycol. Thus, a hydrophobic interaction between fibroblast interferon and the immobilized lectin seems to account for a large portion of the binding forces involved. Other hydrophobic solutes, such as dioxane, 1, 2-propanediol, and tetraethylammonium chloride, were found equally or more efficient than ethylene glycol in displacing interferon from the lectin column. The elution pattern of interferon from a concanavalin A-agarose (Con A-Sepharose) column, at a constant ehtylene glycol concentration and with an increasing mannoside concentration, reveals the existence of four distinct interferon components. The selective adsorption to and elution from a concanavalin A-agarose (Con A-Sepharose) column resulted in about a 3000-fold purification of human fibroblast interferon and complete recovery of activity. The specific activity of the partially purified interferon preparation is about 5 X 10(7) units per mg of protein. The chromatographic behavior of human leukocyte interferon is remarkable in that it does not bind to concanavalin A-agarose at all indicating the absence of carbohydrate moieties recognizable by the lectin, or if present, their masked status. When concanavalin A was coupled to an agarose matrix (cyanogen bromide activated) at pH 8.0 and 6.0 human fibroblast interferon bound to both lectin-agarose adsorbents and could be recovered with methyl alpha-D-mannopyranoside. Concanavalin A, immobilized directly on agarose matrix at pH 8.0 and 6.0, thus displays only carbohydrate recognition toward interferon. By contrast, unless a hydrophobic solute was included in the solvent containing methyl mannoside, human fibroblast interferon could not be recovered from concanavalin A-agarose coupled at pH 9.0. When concanavalin A was immobilized via molecular arms, in tetrameric as well as dimeric forms, the binding of interferon again occurred exclusively through carbohydrate recognition. Thus, the hydrophobic interaction can be eliminated by appropriate immobilization of the lectin, and then adsorbed glycoproteins, as exemplified here by interferon, can be recovered readily with methyl mannoside alone.     

Binding of 125I-labeled recombinant beta interferon (IFN-beta Ser17) to human cells.

We investigated the binding of 125I-labeled beta interferon (IFN-beta Ser17), a nonglycosylated recombinant human fibroblast interferon in which cysteine at position 17 is replaced by serine by site-specific mutagenesis. An optimized chloramine T radiolabeling method produced a highly labeled, fully active 125I-IFN suitable for these studies. Unlike the case with the chloramine T method, incorporation of a single mole of Bolton-Hunter reagent into a mole of IFN-beta Ser17 led to nearly complete loss of biological activity. 125I-IFN-beta Ser17, prepared by the chloramine T method, bound specifically to human lymphoblastoid cells (Daudi) with a dissociation constant of 0.24 nM. The number of binding sites per cell was 4,000. In competition assays, unlabeled beta interferons (native, recombinant IFN-beta Cys17, and various preparations of IFN-beta Ser17) equally displaced labeled IFN-beta Ser17 on Daudi cells. Recombinant IFN-alpha-1 displaced 125I-IFN-beta binding to Daudi cells less efficiently than did unlabeled native or recombinant beta interferon. However, at the concentrations tested, native gamma interferon showed no competition with 125I-IFN. Our results indicate that IFN-beta Ser17 and native IFN-beta posses similar binding properties.     

Monoclonal antibodies against human fibroblast interferon

A stable hybridoma clone derived by infusion of mouse myeloma cells (cell line Fo) and spleen cells of immunized mice has been isolated which secretes monoclonal antibodies against human fibroblast interferon (interferon-beta). The antibody inhibits the antiviral activity of human fibroblast interferon in an antiviral assay using human FS4 fibroblast, reacts immunologically with interferon-beta separated by sodium dodecylsulfate/polyacrylamide gel electrophoresis and subsequent transfer to nitrocellulose and absorbs interferon-beta immunologically when bound to CNBr-activated Sepharose. It also inhibits the antiviral activity of human fibroblast interferon-beta from which the sugar moiety has been cleaved off by enzymatic treatment. The antibody is therefore probably directed against the protein moiety of the interferon molecules.     

Inducible high level synthesis of mature human fibroblast interferon in Escherichia coli.

We have obtained high level synthesis in Escherichia coli of mature human fibroblast interferon using a plasmid vector that was designed to allow easy coupling of a DNA coding region to the initiator AUG of the replicase gene of the RNA phage MS2 cloned downstream of phage lambda's leftward promoter. The activity of the promoter can be regulated by temperature. Induced cells accumulated the interferon up to 4% of the total cellular protein. The biological activity of the product amounted to 4 X 10(9) international units per litre of culture. The synthesis of human fibroblast interferon was shown to drastically inhibit the growth rate of the bacterial host.     

Increased nitroblue tetrazolium dye reduction by human neutrophils stimulated by interferon in vitro

Human leukocyte interferon enhanced nitroblue tetrazolium dye (NBT) reduction by human neutrophils (PMNs). Increase in NBT reduction paralleled increase in interferon dose. When human leukocyte interferon was heated to 60 C or 80 C for 30 min, both the antiviral activity and the effect on NBT reduction decreased. Human leukocyte interferon neutralized with anti-human leukocyte interferon serum showed no effect on NBT reduction. A human fibroblast interferon preparation also enhanced NBT reduction. The species dependency of interferon was shown in NBT reduction as well as in antiviral activity.     

Isolation and properties of genetic engineered human leukocyte interferons alphaI1 and alphaN

Using controlled pore glass chromatography and immunoaffinity chromatography on monoclonal antibodies NK-2 immobilized on Sepharose 4B, the electrophoretically homogeneous interferons alpha N and alpha I1 were isolated from the biomass of gene-engineered Pseudomonas sp. strains. In terms of specific activity on human fibroblast diploid cells, interferon alpha I1 does not differ from interferon alpha A, whereas the specific antiviral activity of interferon alpha N is as low as 2.10(7) JU/mg. The procedures for immunometric assay of interferons alpha N and alpha I1 have been elaborated. Various monoclonal antibodies to interferon alpha A and to natural leucocyte interferon were analyzed; among those the antibodies specifically interacting with interferons alpha N and alpha I1 (but not with interferon alpha A) were identified.     

Human interferon enhances gunaylate cyclase activity

Partially purified human leukocyte interferons, partially purified human lymphoblastoid interferon, and human fibroblast interferon enhanced rat liver, kidney, and splenic guanylate cyclase {E.C.4.6.1.2.} activity 2–4 fold at 5 μIU concentration. Dose-response relationships revealed that the human leukocyte interferons enhanced splenic guanylate cyclase activity at concentrations as low as 0.01 μIU while a concentration of 1 μIU for partially purified human lymphoblastoid interferon and 10 μIU concentration for human fibroblast interferon were necessary to see any effect on guanylate cyclase activity.     

Enzymatic modifications of human fibroblast and leukocyte interferons

The sensitivity of highly purified human fibroblast interferon and partially purified human leukocyte interferon to several proteolytic and glycolytic enzymes was determined with respect to antiviral activity, isoelectric point, molecular weight, and thermal stability. Leucine aminopeptidase altered the distribution of isoelectric points for both interferons but produced little change in molecular weights; this enzyme somewhat reduced the activity of only leukocyte interferon. Treatment of fibroblast interferon with carboxypeptidases A and B did not greatly decrease antiviral activity, but it did slightly reduce the molecular weight of the interferon and substantially altered the distribution of isoelectric point values; similar treatment of leukocyte interferon caused some loss in activity, especially of the 17,000-molecular-weight species. Both interferons were inactivated rapidly by treatment with the endoproteases trypsin, pepsin, bromelain, and subtilisin. Chymotrypsin shifted the isoelectric points of both interferons, but only leukocyte interferon was significantly inactivated. Treatment with neuraminidase and beta-galactosidase changed the isoelectric point distribution but did not affect the activity or thermal stability of either interferon; such a treatment reduced the molecular weight of fibroblast interferon and the size heterogeneity of leukocyte interferon. Treatment with neuraminidase and then leucine aminopeptidase greatly reduced the activity of both interferons, especially leukocyte interferon. The data indicate that biologically active forms of fibroblast and leukocyte interferons can be distinguished by their relative sensitivity to certain proteases.     

Synthesis of human fibroblast interferon by E. coli

A cDNA library was constructed using mRNA from human fibroblasts induced with poly(I):poly(C). A bacterial clone containing fibroblast interferon cDNA sequences was identified by hybridization to a cDNA probe synthesized using deoxyoligonucleotide primers which hybridize to fibroblast interferon mRNA specifically. Expression plasmids were constructed which permitted the synthesis in E. coli of 8 x 10(7) units of human fibroblast interferon per liter of culture. The bacterially produced fibroblast interferon is indistinguishable from authentic human fibroblast interferon by several criteria.     

Molecular structure of human fibroblast and leukocyte interferons: probe by lectin and hydrophobic chromatography.

Structural differences between human leukocyte virus-induced interferon and human fibroblast polyinosinic-polycytidylic acid (rIn-rCn)-induced interferon have been noted in previous studies. This study reports the behavior of human leukocyte and fibroblast interferon, induced by virus and by rIn-rCn, in several lectin and hydrophobic chromatographic systems. Differences in both glycosylation and in hydrophobicity of human leukocyte and fibroblast interferons are documented. Human fibroblast interferon is a glycoprotein, whereas our evidence suggests that human leukocyte interferon probably is not. Also, fibroblast interferon is more hydrophobic than leukocyte interferon, as probed on several hydrophobic adsorbents. The possible relationships of these differences to each other and to antigenic variations are discussed. Generally, the differences appear to be attributable to the cell type in which the interferon was induced. However, our results suggest that at least subtle differences in the processing of the induction signal (virus or rIn-rCn) within the same cell type may occur, slightly altering some structural features.     

Induction of interferon in HeLa cells of a protein kinase activated by double-stranded RNA

Treatment of HeLa cells with human fibroblast interferon results in increased levels of latent protein kinase activity that can be activated by double-stranded RNA (dsRNA). The protein kinase activity in extracts of interferon-treated cells is assayed by two methods: (a) inhibition of protein synthesis in rabbit reticulocyte lysates and (b) phosphorylation of two polypeptides of Mr 72000 (P1) and 38000 (the eIF-2 alpha subunit of initiation factor 2). When extracts of interferon-treated cells are fractionated by centrifugation at 150000 x g, the protein kinase activity is found in the pellet fraction. The kinase is maximally activated by 0.1 micrograms/ml poly(I) . poly(C). An increase in protein kinase activity is detected after 8 h of treatment with 100 units interferon/ml or after a 17-h treatment with 12.5 units/ml or greater interferon concentrations. Therefore, the kinase activity increases as a function of both time of treatment and interferon concentration. Addition of actinomycin D to cells during interferon treatment prevents this increase. The protein kinase activity decreases gradually over three days when interferon-treated cells are subsequently grown in the absence of interferon.     

Molecularly imprinted cryogels for human interferon‐alpha purification from human gingival fibroblast culture

Interferons are important proteins for the immune system because of their antiviral, anti‐proliferating and immunomodulatory activities. Therapeutic value of these proteins against certain types of tumors caused interest and investigations aimed to obtain highly purified interferons. Molecular imprinting is an efficient method for purification with high selectivity, specificity and good reproducibility. In this study, we utilized advantages of molecular imprinting technique for the purification of interferon from human gingival fibroblast culture. For this purpose, interferon α‐2b imprinted poly(hydroxyethyl methacrylate) cryogel (hIFN‐α‐MIP) was prepared. Optimum adsorption conditions were determined, and maximum adsorption capacity of hIFN‐α‐MIP cryogel was found as 254.8 × 10⁴ IU/g from aqueous solution. All interferon measurements are expressed as International Unit (IU), which is a unit measurement used to quantify biologically active substances like interferon based on their biological activity or effect. Selectivity experiments were performed using competitive proteins and repeated adsorption–desorption studies showed that the adsorption capacity maintained almost at a constant value after ten cycles. For the purification of interferon from human gingival fibroblast culture, fast protein liquid chromatography was used and the specific activity of the purified interferon α‐2b on HeLa cell line was found between the values 3.45 × 10⁸ IU/mg and 3.75 × 10⁸ IU/mg. The results are promising, and the molecular imprinting technique is effective for the purification of interferon α‐2b. Copyright © 2013 John Wiley & Sons, Ltd.     

Alveolar macrophage lipoxygenase products of arachidonic acid: isolation and recognition as the predominant constituents of the neutrophil chemotactic activity elaborated by alveolar macrophages

Human immune interferon preparations have anticellular activity on human cell lines (WISH and HEp-2). This anticellular activity copurified with the human immune interferon and appears to be a function of the immune interferon molecule. On the basis of a unit of antiviral activity, purified human immune interferon had about 20 and 100 times more anticellular activity than purified fibroblast or leukocyte interferon, respectively. The possible implications of this finding in the treatment of human neoplasia are discussed.     

Separation of human leukocyte interferon components by concanavalin A-agarose affinity chromatography and their characterization.

Human leukocyte interferon (HL-IF), produced by mixed leukocytes infected with Newcastle disease virus, was resolved into three distinct fractions when chromatographed on concanavalin A-agarose. The major portion (70--75%) of interferon appeared in the breakthrough (BT fraction). The bound interferon (25--30%) was displaced from the column as two peaks: the first was eluted with 0.01 M methyl alpha-D-mannoside, yielding 15-20% of the interferon activity (alpha-MM fraction), and the second by including ethylene glycol (70%) in the eluant, yielding the remaining 5--15% of the interferon (EG fraction). No interferon was retained when HL-IF produced in the presence of glycosylation inhibitors (tunicamycin or 2-deoxy-D-glucose) was chromatographed on concanavalin A-agarose, suggesting that the fraction of interferon retained by this lectin is glycosylated. The three fractions of interferon (BT, alpha-MM, and EG) were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, cross-species antiviral activity, and neutralization by specific antisera. The BT fraction contains exclusively the 16 000 molecular weight component of human leukocyte interferon. The majority of the alpha-MM fraction (90%) is the 21 000 molecular weight component. However, the EG fraction contains the 16 000 and 21 000--23 000 molecular weight components in essentially equal proportions. On the basis of cross-species antiviral activity and neutralization by specific antisera, the BT and alpha-MM fractions are leukocyte-type interferon and the EG fraction seems to be primarily of fibroblast type.     

Improved large scale purification procedure of natural human fibroblast interferon

Human fibroblast interferon, produced in tissue culture by a superinduction procedure, was purified 10,000-fold by chromatography to ca 50% purity as judged by SDS-PAGE. The specific activity of the interferon preparation is 2 X 10(8) and the yield is 70%. The interferon preparation is suitable for clinical use.     

Large scale purification of human fibroblast interferon

Human fibroblast interferon was partially purified, about 4,000-fold, on a chromatographic tandem of columns: concanavalin A-agarose leads to phenyl-agarose, to a specific activity of ca 4 x 10(7). The overall recovery of interferon activity was ca 60%.     

Reversible inhibition by interferon of the maturation of human peripheral blood monocytes to macrophages

We demonstrated that interferon delays the maturation of human monocytes to macrophages in vitro as assessed by morphologic, histochemical, and biochemical parameters. After exposure to interferon, monocytes were slightly smaller, less stretched out, and had a delayed loss of granules with peroxidase positive reactivity, as compared with control, noninterferon-treated cells. Also, interferon prevented the increase of the specific activity of three lysosomal enzymes (β-galactosidase, β-glucuronidase, and β-N-acetylglucosaminidase) in the monocytes, and enzyme activities were 30–40% of that observed in untreated cells. Both human leukocyte and human fibroblast interferons were effective in delaying the maturation process. The effects of the interferon were species specific and reversible and were neutralized by antiinterferon serum. These studies describe a new nonantiviral effect of interferon, unique in that it involves the delay of maturation of cells in a system which is not associated with cell proliferation. Thus interferon could potentially effect host defense mechanisms and aspects of the immune response which are dependent on the maturation of monocytes to macrophages.