Expression of mutant dynamin inhibits toxicity and transport of endocytosed ricin to the Golgi apparatus.

Endocytosis and intracellular transport of ricin were studied in stable transfected HeLa cells where overexpression of wild-type (WT) or mutant dynamin is regulated by tetracycline. Overexpression of the temperature-sensitive mutant dynG273D at the nonpermissive temperature or the dynK44A mutant inhibits clathrin-dependent endocytosis (Damke, H., T. Baba, A.M. van der Blieck, and S.L. Schmid. 1995. J. Cell Biol. 131: 69-80; Damke, H., T. Baba, D.E. Warnock, and S.L. Schmid. 1994. J. Cell Biol. 127:915-934). Under these conditions, ricin was endocytosed at a normal level. Surprisingly, overexpression of both mutants made the cells less sensitive to ricin. Butyric acid and trichostatin A treatment enhanced dynamin overexpression and increased the difference in toxin sensitivity between cells with normal and mutant dynamin. Intoxication with ricin seems to require toxin transport to the Golgi apparatus (Sandirg, K., and B. van Deurs. 1996. Physiol. Rev. 76:949-966), and this process was monitored by measuring the incorporation of radioactive sulfate into a modified ricin molecule containing a tyrosine sulfation site. The sulfation of ricin was much greater in cells expressing dynWT than in cells expressing dynK44A. Ultrastructural analysis using a ricin-HRP conjugate confirmed that transport to the Golgi apparatus was severely inhibited in cells expressing dynK44A. In contrast, ricin transport to lysosomes as measured by degradation of 125I-ricin was essentially unchanged in cells expressing dynK44A. These data demonstrate that although ricin is internalized by clathrin-independent endocytosis in cells expressing mutant dynamin, there is a strong and apparently selective inhibition of ricin transport to the Golgi apparatus. Also, in cells with mutant dynamin, there is a redistribution of the mannose-6-phosphate receptor.

Rab27a regulates the peripheral distribution of melanosomes in melanocytes.

Rab GTPases are regulators of intracellular membrane traffic. We report a possible function of Rab27a, a protein implicated in several diseases, including Griscelli syndrome, choroideremia, and the Hermansky-Pudlak syndrome mouse model, gunmetal. We studied endogenous Rab27a and overexpressed enhanced GFP-Rab27a fusion protein in several cultured melanocyte and melanoma-derived cell lines. In pigmented cells, we observed that Rab27a decorates melanosomes, whereas in nonpigmented cells Rab27a colocalizes with melanosome-resident proteins. When dominant interfering Rab27a mutants were expressed in pigmented cells, we observed a redistribution of pigment granules with perinuclear clustering. This phenotype is similar to that observed by others in melanocytes derived from the ashen and dilute mutant mice, which bear mutations in the Rab27a and MyoVa loci, respectively. We also found that myosinVa coimmunoprecipitates with Rab27a in extracts from melanocytes and that both Rab27a and myosinVa colocalize on the cytoplasmic face of peripheral melanosomes in wild-type melanocytes. However, the amount of myosinVa in melanosomes from Rab27a-deficient ashen melanocytes is greatly reduced. These results, together with recent data implicating myosinVa in the peripheral capture of melanosomes, suggest that Rab27a is necessary for the recruitment of myosinVa, so allowing the peripheral retention of melanosomes in melanocytes.

Stimulation of proliferation of a human osteosarcoma cell line by exogenous acidic fibroblast growth factor requires both activation of receptor tyrosine kinase and growth factor internalization.

U2OS Dr1 cells, originating from a human osteosarcoma, are resistant to the intracellular action of diphtheria toxin but contain toxin receptors on their surfaces. These cells do not have detectable amounts of fibroblast growth factor receptors. When these cells were transfected with fibroblast growth factor receptor 4, the addition of acidic fibroblast growth factor to the medium induced tyrosine phosphorylation, DNA synthesis, and cell proliferation. A considerable fraction of the cell-associated growth factor was found in the nuclear fraction. When the growth factor was fused to the diphtheria toxin A fragment, it was still bound to the growth factor receptor and induced tyrosine phosphorylation but did not induce DNA synthesis or cell proliferation, nor was any fusion protein recovered in the nuclear fraction. On the other hand, when the fusion protein was associated with the diphtheria toxin B fragment to allow translocation to the cytosol by the toxin pathway, the fusion protein was targeted to the nucleus and stimulated both DNA synthesis and cell proliferation. In untransfected cells containing toxin receptors but not fibroblast growth factor receptors, the fusion protein was translocated to the cytosol and targeted to the nucleus, but in this case, it stimulated only DNA synthesis. These data indicate that the following two signals are required to stimulate cell proliferation in transfected U2OS Dr1 cells: the tyrosine kinase signal from the activated fibroblast growth factor receptor and translocation of the growth factor into the cell.

A novel canine B-cell leukaemia cell line. Establishment, characterisation and sensitivity to chemotherapeutics.

We established a new B-cell leukaemia cell line CLB70 from a dog with chronic lymphocytic leukaemia. This cell line is positive for CD20, CD45, CD79a, MHC class II, IgG, IgM; weakly positive for CD21; and negative for CD3, CD4, CD5, CD8, CD14, CD34, CD117. PCR for antigen receptor gene rearrangement (PARR) analysis revealed a biclonal immunoglobulin heavy chain (IgH) gene rearrangement and negative result for TCRγ. Western blot analysis of anti- and pro-apoptotic proteins showed increased expression of Bcl-2, Mcl-1, NF-kB, and Ras, and decreased expression of p53. CLB70 cells grow rapidly in vitro and are tumourigenic in nude mice. The CLB70 line is highly sensitive to doxorubicin, less sensitive to etoposide and imatinib, and resistant to piroxicam, celecoxib and dexamethasone. Our results indicate that CLB70 cells are derived from mature B-cells and they may be a useful tool for the development of new therapeutic strategies for both dogs and humans.

Immunophenotypic characterization of canine malignant lymphoma: a retrospective study of cases diagnosed in Poland Lower Silesia, over the period 2011-2013.

Lymphoma is the most frequently diagnosed cancer of the canine haematopoietic system. In this study, the flow cytometry and polymerase chain reaction (PCR) analysis were used to characterize a series of canine lymphomas in detail. The aim of this study was to determine the incidence of B- and T-cell high-grade lymphomas and their immunophenotypic characterization in Lower Silesia, Poland. The results show that the frequency of each type of lymphoma is 71% for B-cell and 17% for T-cell lymphomas. In two cases the PCR techniques confirmed the presence of simultaneous double gene rearrangements of the BCR and TCR receptors.

Effect of mutation of cytoplasmic receptor domain and of genistein on transport of acidic fibroblast growth factor into cells.

Acidic fibroblast growth factor (aFGF) binds to specific transmembrane receptors and is partly transported to a nuclear location. To study this transport we made a kinase-negative mutant of FGF receptor 4 as well as one where the major part of the cytoplasmic receptor domain was deleted, and expressed them in U2OSDr1 cells that lack functional FGF receptors. All receptors mediated endocytic uptake of aFGF. Translocation of the growth factor across cellular membranes was assayed using aFGF with a C-terminal CAAX-motif, which signals addition of a farnesyl group onto the protein once in the cytosol. CAAX-tagged aFGF was farnesylated when incubated with cells containing wild-type or kinase-negative receptors. It was not farnesylated in cells expressing the deleted receptor, or when the incubation was in the presence of genistein. aFGF incubated with cells transfected with wild-type or kinase-negative receptors, but not with the deleted receptor, was partly recovered from the nuclear fraction in the absence, but not in the presence of genistein. The data indicate that the cytoplasmic receptor domain, but not the active kinase, is required for transport of the growth factor into cells, and that genistein inhibits the process.

Detection and assay of some human proteins by immunoconcentration technique.

For detection and semi-quantitative assays of some human proteins by immunoconcentration techniques, specific antibodies covalently bound to nylon microparticles and then captured in the form of small dots on glass microfibre disc, were used. The discs were placed on a water absorbant material in a simple plastic device. For the technique, antibodies labeled with peroxidase were also applied. The use of several chromogenic substrates for peroxidase was checked in the technique.

The use of normal filter paper for "dot-immunobinding assay" of some antibodies.

Normal filter papers were used for specific detection of tiny amounts of antibodies against two penicillin amidase molecular forms from Escherichia coli, monoclonal antibodies of IgG and IgM class against lipopolysaccharide from Citrobacter O36 and IgM antibody against glycoprotein N from human red blood cells. For colour detection of antibodies bound to proper antigens adsorbed on the paper, second antibody-horse radish peroxidase conjugates and hydrogen peroxide with 4-chloronaphthol were applied. The use of filter paper for dot-immunobinding assay of antibodies gave similar results to those obtained with expensive nitrocellulose sheets used by other authors.

The use of antibodies labelled with dyes for fast and simple assay of some human proteins by immunofiltration technique.

Immunofiltration technique with polyclonal and monoclonal antibodies for semi-quantitative assays of human albumin, chorionic gonadotropin, immunoglobulin G and transferrin was elaborated. An amount of antibody was immobolized in the form of 6 radially located small bars on a dry test filter made of glass microfibre sheet. The other amount of antibody, used in solution, was labelled with some dyes like commercial disperse dyes, colloidal elements, formazans and polypyrrole. Number of colour bars appearing on the test filter showed ranged of analyte concentration. Good results were obtained using antibodies labelled with colloidal gold, Disperse Red 11 and formazan from MTT. Assays with monoclonal antibodies were more sensitive than with polyclonal antibodies.

Enzyme-linked immunosorbent assay of basic pancreatic trypsin inhibitor.

Using specific rabbit antibody, one non-competitive (sandwich) and three variants of competitive enzyme-linked immunosorbent assays for basic pancreatic trypsin inhibitor (BPTI) were elaborated. For the assays peroxidase-antibody, two peroxidase-BPTI and beta-galactosidase-BPTI conjugates were applied. The best was competitive assay with peroxidase-BPTI conjugated by two step glutaraldehyde procedure. By this assay we were able to determine 1-10 ng BPTI/ml (0.007-0.07 KIU/ml) and the presence of human blood serum did not affect the assay of the inhibitor.

Effect of pretreatment of wells in polystyrene plates on adsorption of some human serum proteins.

Coating of Immulon polystyrene plates with 0.2% casein in phosphate buffered saline (PBS) completely abolishes adsorption of human serum proteins to these plates. However, pretreatment of such plates with PBS or 0.15 M NaCl in deionized water (10 microS) before coating makes possible adsorption of human immunoglobulins G (HIgG) and M but not serum albumin (HSA) and transferrin (HTrf). Effect of pretreatment with PBS on adsorption of HIgG is long-term and rather stable. Results of experiments with radioiodinated HIgG, mouse IgG, HSA and human chorionic gonadotropin confirm the peculiar effect of pretreatment with PBS on casein coating. Pretreatment with deionized water, instead of PBS, markedly diminish adsorption but tap or commercial spring waters (> 1000 microS), even without 0.15 M NaCl, affect adsorption similarly to PBS in deionized water. Super pure water (0.05 microS) even with NaCl used for pretreatment does not influence adsorption of HIgG to plates coated with casein. Distinct differences in adsorption of HIgG and HTrf was demonstrated using solutions for ELISA prepared from super pure, deionized and tap waters.

Rabbit antibodies to some sequences of human chorionic gonadotropin and their use for immunoassay of the hormone.

Three synthetic peptides corresponding to amino acid sequences of two human chorionic gonadotropin (hCG) subunits were conjugated to thyroglobulin and used for immunization of rabbits. The highest antibody concentration was found in antisera from rabbits immunized with the peptide corresponding to 122-145 sequence of the hormone beta-subunit. Specificity of antisera and immunoaffinity purified rabbit antibodies were studied. Antibody anti-122-145-beta hCG with antibody anti-beta hCG conjugated to peroxidase were suitable for sensitive and specific enzyme immunoassay of hCG and beta hCG. Good correlation was noted between assay of the hormone in sera of patients with trophoblastic diseases or in urine of pregnant women by ELISA with the rabbit antibody pair and by commercial kit or by ELISA with two monoclonal antibodies.

Antigenicity of human and horse myoglobins.

Rabbit antisera against human myoglobin and horse myoglobin cross-reacted with both myoglobins but only one of them recognized human hemoglobin. Two mouse monoclonal antibodies anti-human myoglobin were obtained, but only one of them (No. 49) cross-reacted with horse myoglobin. Antibody No. 49 and rabbit antibodies reacted also with apo-, FITC- and treated with hydrochloric acid or TPCK-trypsin horse myoglobin, but their binding to myoglobin pretreated with NaOH was reduced. Thirteen peptides overlapping sequence of human myoglobin were synthesized on polyethylene pins. Rabbit and mouse polyclonal antibodies reacted with some of these peptides but no reaction was noted with mouse monoclonal antibodies. Two monoclonal antibodies were applied for specific immunoassay of human myoglobin.

The use of acrylic copolymers as antibody carriers for immunoaffinity chromatography.

Among several various acrylic copolymer used as carriers for anti-bovine serum albumin the best are copolymers obtained from acrylonitrile and ethyl or butyl acrylate crosslinked with divinylbenzene which after aminolysis with di- or triamines were activated with glutardialdehyde. The immunoadsorbents thus obtained were successfully used for purification of bovine serum albumin from bovine serum or from crude fraction of the albumin by immunoaffinity chromatography. Electrophoretically pure bovine albumin was eluted from immunoadsorbent column with deionised water and with glycine/HCl buffer, pH 2.5. The albumin was contamined with less than 0.1% of bovine immunoglobulins and with 0.05% of rabbit immunoglobulins. No contamination with rabbit immunoglobulin was observed when immunoadsorbents were pre-treated with sodium borohydride.

Goat antibodies to amino acid sequences of human chorionic gonadotropin (hCG)

Human chorionic gonadotropin, its two subunits and its conjugate with thyroglobulin were used for immunization. The strongest immunogens were demonstrated to be the intact hormone and beta subunit, the weakest was alpha subunit. Using three peptides corresponding to hormone subunits coupled to Sepharose 4B various antibodies were isolated from goat antiserum by immunoaffinity chromatography. Specificity of the purified antibody preparations was studied. It was demonstrated that enzyme linked immunosorbent assay with two goat antibodies--one for coating of microtiter plates and the other one conjugated with peroxidase--is suitable for sensitive assays of both human chorionic gonadotropin and luteinizing hormone. Specific and sensitive assays were performed using combination of goat antibody anti-122-145-beta hCG and monoclonal antibody anti-alpha hCG.

Search for antibodies for immunoenzymatic assay of human lutropin.

Five peptides corresponding to human lutropin (hLH) subunit fragments were synthesized by a solid phase method and their physicochemical characteristics are presented. Antibodies induced in rabbits with 3 peptides of beta hLH fragments coupled to thyrotropin did not bind hLH and human chorionic gonadotropin (hCG). Also 2 synthetic peptides of alpha hLH fragments did not react with rabbit anti-hLH, anti-hCG and anti-alpha hCG antibodies. Using 2 monoclonal anti-alpha hCG and anti-beta hLH antibodies a sensitive sandwich ELISA technique was elaborated. Using this technique stability of hLH was investigated. The ELISA was also applied for assays of urine hLH in normal and ovulation days.

Semiquantitative assay of human chorionic gonadotropin by a simple and fast immunofiltration technique.

An immunofiltration technique for the semiquantitative assay of human chorionic gonadotropin (hCG) was applied in two versions, using different antibodies. One anti-beta hCG subunit was immobilized on a glass microfibre disc in the form of six radially located bars, and the dry disc was placed on a water-absorbing material in a plastic device. A second antibody labelled with horse radish peroxidase conjugate was used in solution. For the colour reaction a solution with tetramethylbenzidine and hydrogen peroxide was used. The number of blue bars appearing on the test disc depended on concentration range of human chorionic gonadotropin. The technique with the monoclonal antibodies, anti-beta hCG and anti-alpha hCG-horse radish peroxidase conjugate, was specific for intact human chorionic gonadotropin, while the technique with the rabbit antibodies, raised against synthetic fragment 122-145-beta hCG and beta hCG-horse radish peroxidase, was useful for both intact human chorionic gonadotropin and its beta-chain. Cross reactions with human lutropin and thyrotropin were negligible. Haemoglobin, urea and various tested drugs did not affect the assay. In the assay of human chorionic gonadotropin in the urine of pregnant women and in sera of patients with trophoblastic diseases, the results from the immunofiltration technique were in accordance with data obtained by classical ELISA and by two commercial kits.

Dependence of ricin toxicity on translocation of the toxin A-chain from the endoplasmic reticulum to the cytosol.

Ricin acts by translocating to the cytosol the enzymatically active toxin A-chain, which inactivates ribosomes. Retrograde intracellular transport and translocation of ricin was studied under conditions that alter the sensitivity of cells to the toxin. For this purpose tyrosine sulfation of mutant A-chain in the Golgi apparatus, glycosylation in the endoplasmic reticulum (ER) and appearance of A-chain in the cytosolic fraction was monitored. Introduction of an ER retrieval signal, a C-terminal KDEL sequence, into the A-chain increased the toxicity and resulted in more efficient glycosylation, indicating enhanced transport from Golgi to ER. Calcium depletion inhibited neither sulfation nor glycosylation but inhibited translocation and toxicity, suggesting that the toxin is translocated to the cytosol by the pathway used by misfolded proteins that are targeted to the proteasomes for degradation. Slightly acidified medium had a similar effect. The proteasome inhibitor, lactacystin, sensitized cells to ricin and increased the amount of ricin A-chain in the cytosol. Anti-Sec61alpha precipitated sulfated and glycosylated ricin A-chain, suggesting that retrograde toxin translocation involves Sec61p. The data indicate that retrograde translocation across the ER membrane is required for intoxication.

Farnesylation of CaaX-tagged diphtheria toxin A-fragment as a measure of transfer to the cytosol.

Diphtheria toxin binds to receptor-positive cells through its B-fragment, the toxin is then endocytosed, and the low pH in endosomes triggers the translocation of the enzymatically active A-fragment to the cytosol. A synchronous release of A-fragments into the cytosol can be induced by exposing cells with surface-bound toxin to low pH. We have used this protein translocation system to develop a novel method to study whether or not a protein is exposed to the cytosol. Protein farnesylation is a cytosolic modification signaled by a C-terminal CaaX motif, and to visualize the translocation process, we added a farnesylation signal to the toxin A-fragment. The A-fragment with an added CaaX motif was farnesylated within 1 h after exposure of cells with surface-bound toxin to low pH, and also A-fragment translocated from endosomes was quantitatively farnesylated. The results indicate that all cell-mediated reduction of the toxin implicates translocation of the A-fragment to the cytosol. The farnesylation was inhibited by lovastatin, the alkylating agent NEM, and the peptidomimetic farnesylation inhibitor B581. Farnesylated A-fragment partitioned preferentially into the detergent phase upon extraction with Triton X-114. Our data suggest that farnesylation of a CaaX tag is generally applicable as a cytosolic marker, and this strategy for monitoring protein transfer to the cytosol may have considerable potential for studying the transport to the cytosol of proteins added externally to cells.