Identification of a casein kinase activity found elevated in human cytomegalovirus transformed cells

How can a traffic light properly work if it is always green? The paradox of CK2 signaling

CK2 is a constitutively active protein kinase that assuring a constant level of phosphorylation to its numerous substrates supports many of the most important biological functions. Nevertheless, its activity has to be controlled and adjusted in order to cope with the varying needs of a cell, and several examples of a fine-tune regulation of its activity have been described. More importantly, aberrant regulation of this enzyme may have pathological consequences, e.g. in cancer, chronic inflammation, neurodegeneration, and viral infection. Our review aims at summarizing our current knowledge about CK2 regulation. In the first part, we have considered the most important stimuli shown to affect protein kinase CK2 activity/expression. In the second part, we focus on the molecular mechanisms by which CK2 can be regulated, discussing controversial aspects and future perspectives.

Carbazole Derivatives as Antiviral Agents: An Overview

Keywords: carbazole; tetrahydrocarbazole; antiviral agents.

Mayaro virus infection cycle relies on casein kinase 2 activity

Replication of Mayaro virus in Vero cells induces dramatic cytopathic effects and cell death. In this study, we have evaluated the role of casein kinase 2 (CK2) during Mayaro virus infection cycle. We found that CK2 was activated during the initial stages of infection ( approximately 36% after 4h). This activation was further confirmed when the enzyme was partially purified from the cellular lysate either by Mono Q 5/5Hr column or heparin-agarose column. Using this later column, we found that the elution profile of CK2 activity from infected cells was different from that obtained for control cell enzyme, suggesting a structural modification of CK2 after infection. Treatment of infected cells with a cell-permeable inhibitor of CK2, dichloro-1-(beta-D-ribofuranosyl)benzimidazole (DRB), abolished the cytopathic effect in a dose-dependent manner. Together this set of data demonstrates for the first time that CK2 activity in host cells is required in Mayaro virus infection cycle.

The use of heparin for treating human malignancies

There is a substantial amount of data implicating coagulation mechanisms in the pathogenesis of malignancy. Studies in some experimental animal models have shown that the anticoagulant heparin limits tumour growth and metastasis and prolongs survival. Experience with the effects of heparin on human malignancy is limited primarily to settings in which it was given either to prevent or to treat thrombosis in patients who also had cancer. However, these studies have shown noteworthy apparent improvement in cancer outcome with heparin, especially with low-molecular-weight heparin. There are several possible mechanisms by which heparin could potentially alter the natural history of cancer progression because of its ability to modify the cellular and molecular environment of tumour cells. This experience provides the rationale for definitive clinical trials of heparin in patients with cancer and also for further experimentation to define the mechanisms of antineoplastic activity by this familiar class of drugs.

Transformation of leukocytes by Theileria parva and T. annulata

Theileria parva and T. annulata provide intriguing models for the study of parasite-host interactions. Both parasites possess the unique property of being able to transform the cells they infect; T. parva transforms T and B cells, whereas T. annulata affects B cells and monocytes/macrophages. Parasitized cells do not require antigenic stimulation or exogenous growth factors and acquire the ability to proliferate continuously. In vivo, parasitized cells undergo clonal expansion and infiltrate both lymphoid and non-lymphoid tissues of the infected host. Theileria-induced transformation is entirely reversible and is accompanied by the expression of a wide range of different lymphokines and cytokines, some of which may contribute to proliferation or may enhance spread and survival of the parasitized cell in the host. The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways. This, in turn, leads to the activation of transcription factors, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.

Indolocarbazoles: potent, selective inhibitors of human cytomegalovirus replication

In our search for new, safer anti-HCMV agents, we discovered that the natural product Arcyriaflavin A (la) was a potent inhibitor of HCMV replication in cell culture. A series of analogues (symmetrical indolocarbazoles) was synthesised to investigate structure activity relationships in this series against a range of herpes viruses (HCMV, VZV, HSV1, and 2). This identified a number of novel, selective and potent inhibitors of HCMV, 12,13-dihydro-2,10-difluoro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazol e-5,7-(6H)-dione (1d) being the best example (IC50=40 nM, therapeutic index > 1450). Compounds described in this series were generally poor inhibitors of protein kinase C betaII, and no correlation was found between the ability to inhibit HCMV and the enzyme PKC.

Actions of heparin that may affect the malignant process

BACKGROUND

Heparin has many actions that may affect the malignant process, especially metastasis.

METHODS

The author conducted an extensive review of the available medical literature about heparin activity that may apply to important factors involved in the malignant process.

RESULTS

Thrombin is generated by tumors, and the resultant fibrin formation impedes natural killer cell activity. Microthrombi arrest tumor cells in capillaries. Heparin prevents the formation of thrombin and neutralizes its activity. Angiogenesis has an important role in metastasis; heparin minimizes angiogenesis via the inhibition of vascular endothelial growth factor, tissue factor, and platelet activating factor. It decreases tumor cell adhesion to vascular endothelium as it inhibits selectin and chemokine actions, and it also decreases the replication and activity of some oncogenic viruses. Matrix metalloproteinases, serine proteases, and heparanases have an important role in metastasis. Heparin decreases their activation and limits their effects. It competitively inhibits tumor cell attachment to heparan sulfate proteoglycans. It blocks the oncogenic action of ornithine decarboxylase and enhances the antineoplastic effect of transforming growth factor-beta. Heparin inhibits activator protein-1, which is the nuclear target of many oncogenic signal transduction pathways, and it potently inhibits casein kinase II, which has carcinogenic activity. Platelet-derived growth factor, which has oncogenic effects, is also inhibited by heparin, as are reverse transcriptase, telomerase, and topoisomerase prooncogenic actions.

CONCLUSIONS

These various heparin actions justify clinical investigation of its possible beneficial effect on malignant disease.

Identification of signal-induced IkappaB-alpha kinases in human endothelial cells

Activation of the nuclear transcription factor-kappaB is an early event in endothelial activation. NF-kappaB activation is regulated by the inducible phosphorylation and subsequent degradation of the inhibitory subunit IkappaB-alpha. We identified two discrete kinases of approximately 36 and 41 kDa in the cytoplasm of human umbilical vein endothelial cells that specifically bind to and phosphorylate the IkappaB-alpha subunit. IkappaB-alpha kinase activity is transiently elevated following treatment with either tumor necrosis factor alpha, interleukin-1beta, or bacterial lipopolysaccharides and precedes activation of either mitogen-activated kinase or Jun kinase. Furthermore, activation of the IkappaB-alpha kinases precedes both the appearance of hyperphosphorylated IkappaB-alpha and its subsequent degradation, as well as the translocation of NF-kappaB to the nucleus. Deletion mutagenesis of the IkappaB-alpha polypeptide revealed that these kinases bind in or around the ankyrin repeat domains and phosphorylate residues within the C terminus. These kinases, however, were not identical to casein kinase II and displayed a pharmacologic profile distinct from other known kinases. These kinases may represent components of a signal transduction pathway regulating IkappaB-alpha levels in vascular endothelium.