No abstract

Recombinant proteins are commonly expressed in eukaryotic expression systems to ensure the formation of disulfide bridges and proper glycosylation. Although many proteins can be expressed easily, some proteins, sub-domains, and mutant protein versions can cause problems. Here, we investigated expression levels of recombinant extracellular, intracellular as well as transmembrane proteins tethered to different polypeptides in mammalian cell lines. Strikingly, fusion of proteins to the prokaryotic maltose-binding protein (MBP) generally enhanced protein production. MBP fusion proteins consistently exhibited the most robust increase in protein production in comparison to commonly used tags, e.g., the Fc, Glutathione S-transferase (GST), SlyD, and serum albumin (ser alb) tag. Moreover, proteins tethered to MBP revealed reduced numbers of dying cells upon transient transfection. In contrast to the Fc tag, MBP is a stable monomer and does not promote protein aggregation. Therefore, the MBP tag does not induce artificial dimerization of tethered proteins and provides a beneficial fusion tag for binding as well as cell adhesion studies. Using MBP we were able to secret a disease causing laminin β2 mutant protein (congenital nephrotic syndrome), which is normally retained in the endoplasmic reticulum. In summary, this study establishes MBP as a versatile expression tag for protein production in eukaryotic expression systems.

The structural characteristics of mesoionic compounds, which contain distinct regions of positive and negative charges associated with a poly-heteroatomic system, enable them to cross cellular membranes and interact strongly with biomolecules. Potential biological applications have been described for mesoionic compounds. 1,3,4-Thiadiazolium mesoionic compound (MI-D), a new mesoionic compound, has been demonstrated to be extremely cytotoxic to B16-F10 murine melanoma cells when compared to fotemustine and dacarbazine, drugs of reference in melanoma treatment protocols, describing inhibition of tumours grown in vitro and in vivo. We now evaluate the effects of mesoionic compound MI-D on different human melanoma cell lines. The drug decreased the viability and proliferation of MEL-85, SK-MEL, A2058 and MEWO cell lines in vitro, showing a considerable cytotoxic activity on these human cells. Adhesion of MEL-85 cells was evaluated in the presence of the drug using different extracellular matrix (ECM) constituents. MI-D decreased MEL-85 adhesion to laminin, fibronectin and matrigel. The morphology and actin cytoskeleton organisation of MEL-85 cells were also modified on MI-D treatment. These results on human melanoma cell lines indicate that MI-D is a very encouraging drug against melanoma, a tumour that is extremely resistant to chemotherapy.

No abstract

The structural characteristics of mesoionic compounds, which contain distinct regions of positive and negative charges associated with a poly-heteroatomic system, enable them to cross cellular membranes and interact strongly with biomolecules. Potential biological applications have been described for mesoionic compounds. In this study we evaluated the antitumour activity of 4-phenyl-5-(4-nitrocinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride (MI-D), a new mesoionic compound, against the mouse melanoma B16-F10 cell line. In vitro assays showed that MI-D interferes with both cell viability and proliferation. MI-D was cytotoxic to B16-F10 cells; cell viability, which was determined at various time intervals (1-72 h) and in the presence of different concentrations of the drug (2.5-75 micro M), was reduced by approximately 80% following 24 h exposure at 25 micro M. The proliferation rate evaluated over 72 h using varying subcytotoxic and cytotoxic concentrations (2.5-25 micro M) decreased in a dose-dependent manner. The in vivo antitumour activity of the drug was evaluated using a subcutaneous B16-F10 melanoma tumour in C57BL/6 mice. Animals were given MI-D intraperitoneally at a single dose of 57 micro mol/kg, 24 h after cell inoculation. Positive controls were treated with fotemustine and dacarbazine, which have known effects on melanoma cells. On day 17, tumours were excised and their weights were determined. MI-D inhibited tumour growth by 85%. This is a very encouraging result with regard to the possibility of MI-D becoming a new tool for melanoma research and treatment.

A galactomannan (GMPOLY) isolated from lichen Ramalina celastri was complexed with vanadyl ion (IV;VO) forming the complex GMPOLY-VO. Both GMPOLY and GMPOLY-VO diminished the superoxide anion production by macrophages triggered with PMA, the complex giving rise to this effect at concentrations 100 times lower than GMPOLY. Macrophages treated with GMPOLY enhanced the nitric oxide production (40%), this effect not being observed when interferon-gamma (IFN-gamma) or IFN-gamma plus lipopolysaccharide (LPS) were present. No effect on nitric oxide production was observed by treatment of macrophage with GMPOLY-VO. Both GMPOLY and GMPOLY-VO exhibited leishmanicidal effects on the amastigote form of Leishmania amazonesis, but only GMPOLY-VO inhibited the growth of promastigote form.

No abstract

The effect of a series of 4-phenyl-5-(2'-Y, 4'-X or 4'-X-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chlorides was evaluated against B16-F10 murine melanoma cells in vitro and against tumors resulting from implanted B16-F10 cells in C57BL/6 mice. These compounds differ from each other only at the cinnamoyl ring substituent (MI-J, X=OH; MI-2,4diF, X=Y=F; MI-4F, X=F and MI-D, X=NO2). The results were compared with those obtained for MI-D, which has already been shown to be a potent and promising drug against melanoma. On exposure of B16-F10 cells to MI-D, MI-2,4diF and MI-4F, all of them at the same micromolar concentration (50 microM) decreased the cell viability to 8, 50 and 22%, respectively, while MI-J did not show any significant effect under the same conditions. However, low doses such as 10 microM MI-D were sufficient to impair cell growth over 72 h, but for MI-2,4diF and MI-4F the effect on B16-F10 proliferation was only observed at a concentration of 25 microM. Furthermore, MI-4F had a slightly better effect than MI-2,4diF in vitro; its effect on tumor growth in vivo was not significant. MI-D inhibited tumor growth by 77%. The greater effectiveness of MI-D compared with MI-2,4diF, MI-4F and MI-J against B16-F10 melanoma cells is probably due to its stronger electron-withdrawing group (NO2), which increases the positive charge on the mesoionic ring and allows extensive conjugation of the side-chain with the exocyclic moiety. This seems to be important for degree of anti-tumor activity of these compounds.