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M Kubes

Publications and source records attributed to M Kubes.

9 recordsLinked to original sources
PubMed1998

Endothelin induces a calcium-dependent phosphorylation of PEA-15 in intact astrocytes: identification of Ser104 and Ser116 phosphorylated, respectively, by protein kinase C and calcium/calmodulin kinase II in vitro.

PEA-15 (phosphoprotein enriched in astrocytes, Mr = 15,000) is an acidic serine-phosphorylated protein highly expressed in the CNS, where it can play a protective role against cytokine-induced apoptosis. PEA-15 is a major substrate for protein kinase C. Endothelins, which are known to exert pleiotropic effects on astrocytes, were used to analyze further the processes involved in PEA-15 phosphorylation. Endothelin-1 or endothelin-3 (0.1 microM) induced a robust phosphorylation of PEA-15 that was abolished by the removal of extracellular calcium, but only diminished by inhibitors of protein kinase C. Microsequencing of phosphopeptides generated by digestion of PEA-15 following endothelin-1 treatment identified two phosphorylated residues: Ser104, previously recognized as the protein kinase C site, and a novel phosphoserine, Ser116, located in a consensus motif for either protein kinase casein kinase II or calcium/calmodulin-dependent protein kinase II (CaMKII). Partly purified PEA-15 was a substrate in vitro for CaMKII, but not for casein kinase II. Two-dimensional phosphopeptide mapping demonstrated that the site phosphorylated in vitro by CaMKII was also phosphorylated in intact astrocytes in response to endothelin. CaMKII phosphorylated selectively Ser116 and had no effect on Ser104, but in vitro phosphorylation by CaMKII appeared to facilitate further phosphorylation by protein kinase C. Treatment of intact astrocytes with okadaic acid enhanced the phosphorylation of the CaMKII site. These results demonstrate that PEA-15 is phosphorylated in astrocytes by CaMKII (or a related kinase) and by protein kinase C in response to endothelin.

Amino Acid Sequence↗
PubMed1995

Intraneuronal delivery of protein kinase C pseudosubstrate leads to growth cone collapse.

Axonal navigation during development requires that cues present in the extracellular environment be capable of modifying the structure of the cone in a dynamic way. Protein kinase C (PKC) has long been suspected to be one of the multiple molecular relays present in the terminal structure of the developing axon and involved in the transduction of extracellular signals. The latter proposal is, however, based on the use of drugs or of protocols leading to pleiotropic and often nonspecific effects. In the present study, we have taken advantage of the discovery of a peptide capable of translocating across biological membranes and to accumulate in the cytoplasm and nucleus of cells in culture, to internalize a highly specific peptidic inhibitor of PKC. We demonstrate that linking the two peptides (vector and PKC inhibitor) allows the internalization of the latter in live cells, specifically inhibits PKC and provokes a rapid modification of growth cone morphology. This set of data thus establishes that a peptidic inhibitor of PKC activity, once internalized, provokes a change in growth cone morphology, reminiscent of the collapse phenotype. In addition, the present study describes a new efficient and harmless way to introduce pharmacologically active substances in neural cells in culture.

Amino Acid Sequence↗
PubMed1994

Cross-species antiviral and antiproliferative activity of human interferon-omega.

The antiviral and antiproliferative activities of human interferon-omega (IFN-omega) on two human cell lines and on VERO (monkey), MDBK (calf), SPEV (pig), L929 (mouse), BHK-21 (hamster), and MDCK (dog) cell lines were compared with those of human IFN-alpha 1 and IFN-alpha 2. The results are tabulated. Compared with its antiviral titer on human A549 cells, INF-omega was more active on mouse cells and even more active on the pig cells, but had little activity on the hamster cells and virtually none on the dog cells. IFN-omega also inhibited the growth of all these cells to a greater or lesser extent, and there was in general an apparent correlation between its antiviral and antiproliferative activities on the different cells, except that the dog cells were relatively much more sensitive to the antiproliferative effect.

Animals↗
PubMed1994

Salivary gland extracts of partially fed Dermacentor reticulatus ticks decrease natural killer cell activity in vitro.

The salivary glands and saliva of ticks (Arachnida, Acari, Ixodida) play a vital role in blood feeding, including manipulation of the host's immune response to tick infestation. Furthermore, a diverse number of tick-borne pathogens are transmitted to vertebrate hosts via tick saliva. A factor synthesized in the salivary glands of feeding ticks potentiates the transmission of certain tick-borne viruses. We show that salivary gland extracts (SGE) derived from Dermacentor reticulatus female ticks fed for 6 days on laboratory mice (SGED6) induced a decrease in the natural killer (NK) activity of effector cells obtained from 16 healthy blood donors. The decreased activity ranged from 14 to 69% of NK activity observed with the respective untreated effector cells. Such a decrease was not observed after treatment of effector cells with SGE from unfed ticks. Ten-fold dilution of SGED6 significantly reduced the capacity to decrease NK activity and a further 10-fold dilution almost eliminated the effect. After addition of IFN-alpha 2, the SGED6-induced decrease in NK activity was restored to activity levels approaching those of untreated cells. The apparent reversibility of the inhibition indicates that the effect of SGED6 on NK activity was not due to cytotoxicity. The results demonstrate the presence of a factor(s) in the salivary gland products of feeding D. reticulatus female ticks that influences human NK activity in vitro. These data suggest a possible mechanism by which tick SGE potentiates the transmission of some tick-borne viruses through suppression of NK activity.

Animals↗
PubMed1993

Masking of HLA class I molecules expressed on K-562 target cells can restore their susceptibility to NK cell cytolysis.

The aim of our study was to follow whether class I HLA antigens play a role in the susceptibility of K-562 target cells to NK cell lysis as well as in the interaction between NK and target cells. After K-562 cells were treated with rIFN-gamma, HLA class I antigens appeared on their surface. Those HLA class I+, in comparison to HLA class I-, K562 target cells became about 40-50% less susceptible to NK cell cytolysis. This influence of HLA class I antigens was abrogated when class I+ K-562 cells were incubated with anti-HLA class I monoclonal antibodies Bra 23/9. The restoration of susceptibility of these targets to NK cell cytolysis was not caused by ADCC mechanism as determined by F(ab')2 fragments or by mAb CD16. Further, the percentage of conjugates between effector and target cells was not significantly altered neither when HLA class I antigens appeared on the surface of K-562 target cells nor when HLA class I+ K-562 cells were incubated with anti-HLA class I monoclonal antibodies. To study this question, we used a different approach because both expression of HLA class I molecules and their masking with appropriate monoclonal antibody were done by means of the same cell line of target cells.

Cytotoxicity, Immunologic↗
PubMed1993

[Interferons as antineoplastic drugs--direct regulatory effects on tumor cells].

Interferons (IFNs) are a family of pleiotropic cell regulatory molecules and members of the cytokine network. Apart from a central role in the body's first-line defence against infections, they are important in regulation of immune responses and may be involved in control of cell growth and differentiation. Over the past ten years, clinical trials provided unequivocal evidence that IFNs to have anticancer activity, even though this is valid in a restricted range of tumours mainly of haematopoietic origin. We currently suppose three ways in which IFNs could affect tumour growth: 1. Direct regulatory effects on tumour cells. 2. Immunomodulatory effects that enhance or even initiate a host response to the tumour. 3. Regulatory effects on host/tumour interaction not associated with immune responses. We reviewed the direct regulatory effects of IFNs on tumour cells and results of clinical trials of IFNs in cancer therapy. (Tab. 2, Ref. 85.)

Animals↗
PubMed1993

In vitro antiproliferative effect of interferon alpha in solid tumors: a potential predictive test.

An in vitro test for the antiproliferative effect of human leukocyte interferon (IFN-alpha) was performed in primary cultures of tumor cells obtained from 32 patients with either malignant melanoma (13), renal carcinoma (4) or bladder carcinoma (15). Our results demonstrated activity of IFN in all three groups of solid tumors. However, appreciable differences in sensitivity to antiproliferative effect of IFN between individual tumors of the same type were found. The potential of this antiproliferative test for prediction of treatment response in IFN-therapy is discussed.

Adult↗
PubMed1990

Relationship between depression of HBsAg production and DNA synthesis by interferons in human hepatoma cell line.

The influence of different interferons (IFNs) on HBsAg production and DNA synthesis was studied in PLC/PRF/5 cells using 30 I.U./ml of natural HuIFN-alpha, 25 I.U./ml of recombinant HuIFN-alpha 2, and 5 I.U./ml of natural murine IFN-alpha/beta. All three IFN types inhibited significant inhibitory effect on HBsAg production during the second 24 hr-interval following their addition. After 96 hr HBsAg production had returned to normal levels. Natural HuIFN-alpha clearly depressed cellular DNA synthesis 24 hr after IFN addition which returned to normal within the next 24 hr. Recombinant HuIFN-alpha 2 influenced DNA synthesis only slightly and the mouse IFN-alpha/beta showed no effect.

Carcinoma, Hepatocellular↗