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Papers by Andrea Baier

Research paper thumbnail of Yeast Protein Asf1 Possesses Modulating Activity towards Protein Kinase CK2

International Journal of Molecular Sciences

Protein kinase CK2 plays an important role in cell survival and protects regulatory proteins from... more Protein kinase CK2 plays an important role in cell survival and protects regulatory proteins from caspase-mediated degradation during apoptosis. The consensus sequence of proteins phosphorylated by CK2 contains a cluster of acidic amino acids around the phosphorylation site. The poly-acidic sequence in yeast protein Asf1 is similar to the acidic loop in CK2β, which possesses a regulatory function. We observed that the overexpression of Asf1 in yeast cells influences cell growth. Experiments performed in vitro and in vivo indicate that yeast protein Asf1 inhibits protein kinase CK2. Our data suggest that each CK2 isoform might be regulated in a different way. Deletion of the amino or carboxyl end of Asf1 reveals that the acidic cluster close to the C-terminus is responsible for the activation or inhibition of CK2 activity.

Research paper thumbnail of CK2 and protein kinases of the CK1 superfamily as targets for neurodegenerative disorders

Frontiers in Molecular Biosciences

Casein kinases are involved in a variety of signaling pathways, and also in inflammation, cancer,... more Casein kinases are involved in a variety of signaling pathways, and also in inflammation, cancer, and neurological diseases. Therefore, they are regarded as potential therapeutic targets for drug design. Recent studies have highlighted the importance of the casein kinase 1 superfamily as well as protein kinase CK2 in the development of several neurodegenerative pathologies, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. CK1 kinases and their closely related tau tubulin kinases as well as CK2 are found to be overexpressed in the mammalian brain. Numerous substrates have been detected which play crucial roles in neuronal and synaptic network functions and activities. The development of new substances for the treatment of these pathologies is in high demand. The impact of these kinases in the progress of neurodegenerative disorders, their bona fide substrates, and numerous natural and synthetic compounds which are able to inhi...

Research paper thumbnail of Metabolic and Proteomic Analysis of Chlorella sorokiniana, Chloroidium saccharofilum, and Chlorella vulgaris Cells Cultured in Autotrophic, Photoheterotrophic, and Mixotrophic Cultivation Modes

Molecules, Jul 27, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Directed evolution

Contemporary Chemical Approaches for Green and Sustainable Drugs

Research paper thumbnail of Organofluorine Hydrazone Derivatives as Multifunctional Anti‐Alzheimer's Agents with CK2 Inhibitory and Antioxidant Features

ChemMedChem, 2021

A set of novel hydrazone derivatives were synthesized and analyzed for their biological activitie... more A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4‐N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical‐scavenging assays and possess nanomolar IC50 values in the kinase assays.

Research paper thumbnail of Mechanism of inhibition of the protein kinase C by nonstructure protein 3 of hepatitis C virus

Cellular & Molecular Biology Letters, 2005

Research paper thumbnail of Synthesis and evaluation of ATP-binding site directed potential inhibitors of nucleoside triphosphatases/helicases and polymerases of hepatitis C and other selected Flaviviridae viruses

Antiviral chemistry & chemotherapy, 2004

5'-O-(4-fluorosulphonylbenzoyl)-esters of ribavirin (FSBR), adenosine (FSBA), guanosine (FSBG... more 5'-O-(4-fluorosulphonylbenzoyl)-esters of ribavirin (FSBR), adenosine (FSBA), guanosine (FSBG) and inosine (FSBI) were obtained by acylation of the 5'-OH of adenosine, guanosine, inosine, and ribavirin with 4-fluorosulphonylbenzoyl chloride (FSBCI) in HMPA. The above derivatives were tested as inhibitors of nucleoside triphosphatase (NTPase)/helicase activities of Flaviviridae: hepatitis C virus (HCV), West Nile virus (WNV), Japanese encephalitis virus (JEV) and dengue virus (DENV) and polymerase activity of HCV and WNV. When the unwinding activity of viral NTPase/helicases was tested under standard conditions, only weak inhibition was obtained with FSBI (IC50 > or = 120 microM) and in the case of FSBG even an activation was seen. The preincubation of the NTPase/helicases with the 5'-O-FSB derivatives increased the inhibitory effect. Screening of the 5'-O-FSB derivatives on inhibition of the WNV and HCV RNA polymerases employing GTP or UTP substrates revealed rath...

Research paper thumbnail of Inhibitors of the NTPase/helicases of hepatitis C and related Flaviviridae viruses

Acta poloniae pharmaceutica, 2004

Abstract: In the search for inhibitors of the non-structural protein 3 (NS3)-associated NTPase/he... more Abstract: In the search for inhibitors of the non-structural protein 3 (NS3)-associated NTPase/helicase activities of the hepatitis C virus (HCV), and of the related West Nile Virus (WNV), and Japanese Encephalitis Virus (JEV), random screening of a broad range of unrelated low-molecular weight compounds revealed that 4,5,6,7-tetrabromo-1H-benzotriazole (TBBT) is a good inhibitor of the helicase activity of HCV and WNV NTPase/helicases (IC50 > 20 mM and 1.7 mM with a DNA substrate), but a very weak inhibitor of the JEV enzyme (IC50 > 200 mM). The synthesis of new TBBT derivatives was undertaken and their inhibitory activities against HCV, WNV, and JEV NTPase/helicases and cytotoxicities were examined. The N-alkyl derivatives showed good activity and lower cytotoxicity than TBBT.

Research paper thumbnail of Tropolone and its derivatives as inhibitors of the helicase activity of hepatitis C virus nucleotide triphosphatase/helicase

Antiviral chemistry & chemotherapy, 2007

In this report, we demonstrate the interaction of the non-structural protein 3 (NS3) of hepatitis... more In this report, we demonstrate the interaction of the non-structural protein 3 (NS3) of hepatitis C virus (HCV) with alkaloide tropolone (2-hydroxy-2,4,6-heptatriene-1-one) and its derivatives. The compounds were biochemically screened separately against the ATPase and helicase activities of HCV NS3. In the investigations presented, alkaIoide tropolone and its derivatives significantly inhibited the helicase activity of the viral protein when using a DNA substrate, with 50% inhibitory concentration values within a low micromolar range. The results using the RNA substrate were unexpected--none of the tropolone derivatives excerted any modulating influence towards the unwinding activity. Surprisingly, no influence of the nucleoside triphosphatase (NTPase) turnover was observed. Evidence is presented confirming that these compounds do not act by blocking the NTP-binding site, but by occupying an additional allosteric regulatory site. Further mechanisms of action, particularly of some o...

Research paper thumbnail of Synthesis and biological activity of 1H-benzotriazole and 1H-benzimidazole analogues--inhibitors of the NTpase/helicase of HCV and of some related Flaviviridae

Antiviral chemistry & chemotherapy, 2005

To improve anti-helical activity of analogues of 1H-benzotriazole and 1H-benzimidazole their N-al... more To improve anti-helical activity of analogues of 1H-benzotriazole and 1H-benzimidazole their N-alkyl derivatives were synthesized and tested for antihelicase activity against enzymes of selected Flaviviridae including hepatitis C virus (HCV), West Nile virus (WNV), Dengue virus (DENV) and Japanese encephalitis virus (JEV). 1- and 2-alkyl derivatives of 4,5,6,7-tetrabromo-1H-benzotriazole were obtained by direct alkylation of 4,5,6,7-tetrabromo-1H-benzotriazole with the use of respective alkyl halides in the presence of KOH in methanol, to give a mixture of 1- and 2- isomers, which was separated by flash column chromatography in good yield. The proportion of isomers strongly depended on the reaction time and temperature. 1- and 2-hydroxyethyl and 1- and 2-chloroethyl derivatives of the tetrabromobenzo-triazole were synthesized with the use of 2-bromoethanol and 1-bromo-2-chloroethane respectively as alkylating agents. N-alkylation of this benzotriazole compound enhanced inhibitory ac...

Research paper thumbnail of Compounds from Natural Sources as Protein Kinase Inhibitors

Biomolecules

The advantage of natural compounds is their lower number of side-effects when compared to most sy... more The advantage of natural compounds is their lower number of side-effects when compared to most synthetic substances. Therefore, over the past several decades, the interest in naturally occurring compounds is increasing in the search for new potent drugs. Natural compounds are playing an important role as a starting point when developing new selective compounds against different diseases. Protein kinases play a huge role in several diseases, like cancers, neurodegenerative diseases, microbial infections, or inflammations. In this review, we give a comprehensive view of natural compounds, which are/were the parent compounds in the development of more potent substances using computational analysis and SAR studies.

Research paper thumbnail of Inhibitory influence of natural flavonoids on human protein kinase CK2 isoforms: effect of the regulatory subunit

Molecular and Cellular Biochemistry

CK2 is a pleiotropic, constitutively active protein kinase responsible for the phosphorylation of... more CK2 is a pleiotropic, constitutively active protein kinase responsible for the phosphorylation of more than 300 physiological substrates. Typically, this enzyme is found in tetrameric form consisting of two regulatory subunits CK2β and two catalytic subunits CK2α or CK2α′. Several natural occurring flavonoids were tested for their ability to inhibit both CK2 holoenzymes, CK2α 2 β 2 and CK2α′ 2 β 2. We identified few substances selectively inhibiting only the α′ subunit. Other compounds showed similar effect towards all four isoforms. In some cases, like chrysoeriol, pedalitin, apigenin, and luteolin, the α 2 β 2 holoenzyme was at least six times better inhibited than the free α subunit. Otherwise, we have found a luteolin derivative decreased the kinase activity of CK2α′ with an IC 50 value of 0.8 μM, but the holoenzyme only with 9.5 µM.

Research paper thumbnail of Selected flavonoid compounds as promising inhibitors of protein kinase CK2α and CK2α′, the catalytic subunits of CK2

Phytochemistry, 2017

CK2 is a ubiquitous protein kinase involved in many cell functions. During the last years it beca... more CK2 is a ubiquitous protein kinase involved in many cell functions. During the last years it became an interesting target in cancer research. A series of flavonoid compounds was tested as inhibitors of protein kinase CK2. Several substances were found to be highly active against both catalytic subunits with IC50 values below 1 μM in case of CK2α'. The most promising inhibitor we identified is chrysoeriol with IC50 values of 250 and 34 nM for CK2α and CK2α', respectively.

Research paper thumbnail of Metalloproteinases of the extracellular matrix and their inhibitors

BioTechnologia, 2016

The dynamic equilibrium between the synthesis and degradation of the extracellular matrix is to a... more The dynamic equilibrium between the synthesis and degradation of the extracellular matrix is to a large extent mediated by matrix metalloproteinase (MMP) enzymes, which are antagonized by tissue inhibitors of metalloproteinases (TIMPs). Tissue-degrading enzymes of the metalloproteinase family have been implicated in the pathogenesis of several conditions involving the extracellular matrix. MMPs are a family of zinc-dependent endopeptidases capable of degrading practically all components of the extracellular matrix. Recent insights suggest that MMPs may also have a broader spectrum of functions, including regulation of the inflammatory response and cytokine signaling. MMPs have been subdivided according to their main degradation activity and the continuously growing list of known substrates. Metalloproteinases are promising drug targets, and they are subjected to pharmacological inhibition by clinically available drugs such as tetracyclines and bisphosphonates. Interest in MMPs has recently increased, because their expression is frequently related to tumor progression. As such, metalloproteinases have diagnostic potential as markers to predict the outcome of disease processes. This review introduces the members of the MMP family and discusses their domain structure and function, their significance in physiology and pathology and the mechanism of inhibition by TIMPs.

Research paper thumbnail of Sensitivity of Protein Kinase CK2 to ATP/GTP and Specific Inhibitors Depends on Complexity of Interacting Proteins

Protein Kinase CK2 Cellular Function in Normal and Disease States, 2015

Research paper thumbnail of Flaviviral Infections and Potential Targets for Antiviral Therapy

Flavivirus Encephalitis, 2011

The family Flaviviridae includes human and animal pathogenic viruses of global importance, e.g. t... more The family Flaviviridae includes human and animal pathogenic viruses of global importance, e.g. the human flaviviruses West-Nile virus (WNV), dengue virus (DENV), Japanese encephalitis virus (JEV), tick-borne encephalitis virus (TBEV) and yellow fever virus (JEV) as well as hepacivirus hepatitis C virus (HCV). This virus family was named after the jaundice occurring in course of YFV infection, the first identified virus of the Flaviviridae (Monath, 1987; Halstead, 1992). In humans infections with Flaviviridae may lead to fulminant, hemorrhagic diseaes [YFV, DENV and omsk hemorrhagic fever virus (OHFV)], viral encephalitis [JEV, TBEV, WNV, St. Louis encephalitis virus (SLEV)] or chronic hepatitis C, formerly referred to as non-A, non-B hepatitis (HCV) (Monath & Heinz, 1996; Rice, 1996). Viruses belonging to the third genus, pestivirus, infect only animals, leading to severe disease of the host, usually followed by death [bovine viral diarrhea virus (BVDV), classical swine fever virus (CSFV) and border disease virus (BDV)] (Nettelton & Entrican, 1995). The genus flavivirus consists of more than 70 species that are, on the basis of phylogenetic analyses, divided into 14 classes which in turn are grouped into three clusters: the mosquitoborne cluster, the tick-borne cluster and the non-vector cluster. All flaviviruses of human importance are mosquito-or tick-borne viruses. They enter through the skin by the bite of an infected arthropod, proliferating locally and spreading through the blood circulation and cross the blood-brain barrier and finally entering the central nervous system. This fact is important for further pathogenesis and unfavorable clinical outcome of the infection (King et al., 2007). Most pathogenic flaviviruses are associated with neurological diseases. The mosquito-borne encephalitic flaviviruses are grouped phylogenetically in the Japanese encephalitis serocomplex. Most tick-borne flaviviruses cause encephalitis and are mainly spread through Europe and Asia. Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae family are registered annually. Up to date, there is no effective antiviral therapy directed against Flaviviridae viruses. Members of the family of Flaviviridae are small (40 to 50 nm), spheric, enveloped RNA viruses of similar structure. The genome of the viruses consists of one single-stranded, positive-sense RNA with a length of 9100 to 11000 bases [e.g. 10862 for YFV (strain 17D), 10477 for Russian spring-summer encephalitis virus (RSSEV) and approx. 9100 for HCV].

Research paper thumbnail of The NTPase/helicase domain of hepatitis C virus nonstructural protein 3 inhibits protein kinase C independently of its NTPase activity

Cellular & Molecular Biology Letters, 2013

Helicase motif VI is a short arginine-rich motif within the NTPase/helicase domain of the non-str... more Helicase motif VI is a short arginine-rich motif within the NTPase/helicase domain of the non-structural protein 3 (NS3) of the hepatitis C virus (HCV). We previously demonstrated that it reduces the catalytic activity and intracellular shuttling of protein kinase C (PKC). Thus, NS3-mediated PKC inhibition may be involved in HCV-associated hepatocellular carcinoma (HCC). In this study, we expand on our earlier results, which were obtained in experiments with short fragments of NS3, to show for the first time that the catalytically active, longer C-terminal NTPase/helicase of NS3 acts as a potent PKC inhibitor in vitro. PKC inhibition assays with the NTPase-inactive mutant NS3h-D1316A revealed a mixed type kinetic inhibition pattern. A broad range of 11 PKC isotypes was tested and all of the PKC isotypes were inhibited with IC50-values in the low micromolar range. These findings were confirmed for the wild-type NTPase/helicase domain in a non-radiometric PKC inhibition assay with ATP...

Research paper thumbnail of Yeast Asf1 Protein as Modulator of Protein Kinase CK2 Activity

Protein Kinase CK2 Cellular Function in Normal and Disease States, 2015

Research paper thumbnail of Inhibition of Flaviviridae Replication Complex: Assays to Investigate the Modulating Effect of Potential Compounds

Current Enzyme Inhibition, 2009

Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae fam... more Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae family, like hepatitis C virus (HCV), West-Nile virus (WNV), dengue virus (DENV) and Japanese encephalitis virus (JEV) are registered annually.

Research paper thumbnail of Viral NS3 helicase activity is inhibited by peptides reproducing the Arg-rich conserved motif of the enzyme (motif VI)

Biochemical Pharmacology, 2008

The NTPase/helicase of Flaviviridae viruses is one of the essential components of their replicati... more The NTPase/helicase of Flaviviridae viruses is one of the essential components of their replication complex. The enzyme is defined by the presence of seven highly conserved amino acid motifs. Random screening of numerous hepatitis C virus (HCV) derived peptides, revealed a basic amino acid stretch corresponding to motif VI of the HCV NTPase/helicase (amino acids 1487-1500 of the HCV polyprotein). This peptide inhibited the unwinding activity of the enzyme with an IC(50)=0.2 microM. Peptides corresponding to motif VI of HCV, West Nile virus (WNV) and Japanese encephalitis virus (JEV) were synthesized and tested as inhibitors of NTPase and unwinding reactions mediated by the viral enzymes. Peptides distinguished in regard to their length and structure. Between the peptides tested HCV(1487-1500) reproducing the sequence of motif VI was the most potent inhibitor of helicase activities of investigated enzymes. Other respective peptides were rather modest inhibitors. The examined peptides inhibited the Flaviviridae helicases in the following order of potency: HCV(1487-1500)>WNV(1959-1572)>JEV(1962-1975). Interestingly, the susceptibility of the helicase activity to the inhibition by the peptides was similar and in the row: HCV>WNV>JEV. The inhibition results from binding and blockade of the active site of the enzyme lyes beyond the NTP-binding and hydrolyzing site. The kinetic analyses indicated that the binding of the peptides do not interfere with the NTPase activity of the enzymes. The peptide may serve as effective and selective tool to reduce the virus propagation.

Research paper thumbnail of Yeast Protein Asf1 Possesses Modulating Activity towards Protein Kinase CK2

International Journal of Molecular Sciences

Protein kinase CK2 plays an important role in cell survival and protects regulatory proteins from... more Protein kinase CK2 plays an important role in cell survival and protects regulatory proteins from caspase-mediated degradation during apoptosis. The consensus sequence of proteins phosphorylated by CK2 contains a cluster of acidic amino acids around the phosphorylation site. The poly-acidic sequence in yeast protein Asf1 is similar to the acidic loop in CK2β, which possesses a regulatory function. We observed that the overexpression of Asf1 in yeast cells influences cell growth. Experiments performed in vitro and in vivo indicate that yeast protein Asf1 inhibits protein kinase CK2. Our data suggest that each CK2 isoform might be regulated in a different way. Deletion of the amino or carboxyl end of Asf1 reveals that the acidic cluster close to the C-terminus is responsible for the activation or inhibition of CK2 activity.

Research paper thumbnail of CK2 and protein kinases of the CK1 superfamily as targets for neurodegenerative disorders

Frontiers in Molecular Biosciences

Casein kinases are involved in a variety of signaling pathways, and also in inflammation, cancer,... more Casein kinases are involved in a variety of signaling pathways, and also in inflammation, cancer, and neurological diseases. Therefore, they are regarded as potential therapeutic targets for drug design. Recent studies have highlighted the importance of the casein kinase 1 superfamily as well as protein kinase CK2 in the development of several neurodegenerative pathologies, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. CK1 kinases and their closely related tau tubulin kinases as well as CK2 are found to be overexpressed in the mammalian brain. Numerous substrates have been detected which play crucial roles in neuronal and synaptic network functions and activities. The development of new substances for the treatment of these pathologies is in high demand. The impact of these kinases in the progress of neurodegenerative disorders, their bona fide substrates, and numerous natural and synthetic compounds which are able to inhi...

Research paper thumbnail of Metabolic and Proteomic Analysis of Chlorella sorokiniana, Chloroidium saccharofilum, and Chlorella vulgaris Cells Cultured in Autotrophic, Photoheterotrophic, and Mixotrophic Cultivation Modes

Molecules, Jul 27, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Directed evolution

Contemporary Chemical Approaches for Green and Sustainable Drugs

Research paper thumbnail of Organofluorine Hydrazone Derivatives as Multifunctional Anti‐Alzheimer's Agents with CK2 Inhibitory and Antioxidant Features

ChemMedChem, 2021

A set of novel hydrazone derivatives were synthesized and analyzed for their biological activitie... more A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4‐N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical‐scavenging assays and possess nanomolar IC50 values in the kinase assays.

Research paper thumbnail of Mechanism of inhibition of the protein kinase C by nonstructure protein 3 of hepatitis C virus

Cellular & Molecular Biology Letters, 2005

Research paper thumbnail of Synthesis and evaluation of ATP-binding site directed potential inhibitors of nucleoside triphosphatases/helicases and polymerases of hepatitis C and other selected Flaviviridae viruses

Antiviral chemistry & chemotherapy, 2004

5'-O-(4-fluorosulphonylbenzoyl)-esters of ribavirin (FSBR), adenosine (FSBA), guanosine (FSBG... more 5'-O-(4-fluorosulphonylbenzoyl)-esters of ribavirin (FSBR), adenosine (FSBA), guanosine (FSBG) and inosine (FSBI) were obtained by acylation of the 5'-OH of adenosine, guanosine, inosine, and ribavirin with 4-fluorosulphonylbenzoyl chloride (FSBCI) in HMPA. The above derivatives were tested as inhibitors of nucleoside triphosphatase (NTPase)/helicase activities of Flaviviridae: hepatitis C virus (HCV), West Nile virus (WNV), Japanese encephalitis virus (JEV) and dengue virus (DENV) and polymerase activity of HCV and WNV. When the unwinding activity of viral NTPase/helicases was tested under standard conditions, only weak inhibition was obtained with FSBI (IC50 > or = 120 microM) and in the case of FSBG even an activation was seen. The preincubation of the NTPase/helicases with the 5'-O-FSB derivatives increased the inhibitory effect. Screening of the 5'-O-FSB derivatives on inhibition of the WNV and HCV RNA polymerases employing GTP or UTP substrates revealed rath...

Research paper thumbnail of Inhibitors of the NTPase/helicases of hepatitis C and related Flaviviridae viruses

Acta poloniae pharmaceutica, 2004

Abstract: In the search for inhibitors of the non-structural protein 3 (NS3)-associated NTPase/he... more Abstract: In the search for inhibitors of the non-structural protein 3 (NS3)-associated NTPase/helicase activities of the hepatitis C virus (HCV), and of the related West Nile Virus (WNV), and Japanese Encephalitis Virus (JEV), random screening of a broad range of unrelated low-molecular weight compounds revealed that 4,5,6,7-tetrabromo-1H-benzotriazole (TBBT) is a good inhibitor of the helicase activity of HCV and WNV NTPase/helicases (IC50 > 20 mM and 1.7 mM with a DNA substrate), but a very weak inhibitor of the JEV enzyme (IC50 > 200 mM). The synthesis of new TBBT derivatives was undertaken and their inhibitory activities against HCV, WNV, and JEV NTPase/helicases and cytotoxicities were examined. The N-alkyl derivatives showed good activity and lower cytotoxicity than TBBT.

Research paper thumbnail of Tropolone and its derivatives as inhibitors of the helicase activity of hepatitis C virus nucleotide triphosphatase/helicase

Antiviral chemistry & chemotherapy, 2007

In this report, we demonstrate the interaction of the non-structural protein 3 (NS3) of hepatitis... more In this report, we demonstrate the interaction of the non-structural protein 3 (NS3) of hepatitis C virus (HCV) with alkaloide tropolone (2-hydroxy-2,4,6-heptatriene-1-one) and its derivatives. The compounds were biochemically screened separately against the ATPase and helicase activities of HCV NS3. In the investigations presented, alkaIoide tropolone and its derivatives significantly inhibited the helicase activity of the viral protein when using a DNA substrate, with 50% inhibitory concentration values within a low micromolar range. The results using the RNA substrate were unexpected--none of the tropolone derivatives excerted any modulating influence towards the unwinding activity. Surprisingly, no influence of the nucleoside triphosphatase (NTPase) turnover was observed. Evidence is presented confirming that these compounds do not act by blocking the NTP-binding site, but by occupying an additional allosteric regulatory site. Further mechanisms of action, particularly of some o...

Research paper thumbnail of Synthesis and biological activity of 1H-benzotriazole and 1H-benzimidazole analogues--inhibitors of the NTpase/helicase of HCV and of some related Flaviviridae

Antiviral chemistry & chemotherapy, 2005

To improve anti-helical activity of analogues of 1H-benzotriazole and 1H-benzimidazole their N-al... more To improve anti-helical activity of analogues of 1H-benzotriazole and 1H-benzimidazole their N-alkyl derivatives were synthesized and tested for antihelicase activity against enzymes of selected Flaviviridae including hepatitis C virus (HCV), West Nile virus (WNV), Dengue virus (DENV) and Japanese encephalitis virus (JEV). 1- and 2-alkyl derivatives of 4,5,6,7-tetrabromo-1H-benzotriazole were obtained by direct alkylation of 4,5,6,7-tetrabromo-1H-benzotriazole with the use of respective alkyl halides in the presence of KOH in methanol, to give a mixture of 1- and 2- isomers, which was separated by flash column chromatography in good yield. The proportion of isomers strongly depended on the reaction time and temperature. 1- and 2-hydroxyethyl and 1- and 2-chloroethyl derivatives of the tetrabromobenzo-triazole were synthesized with the use of 2-bromoethanol and 1-bromo-2-chloroethane respectively as alkylating agents. N-alkylation of this benzotriazole compound enhanced inhibitory ac...

Research paper thumbnail of Compounds from Natural Sources as Protein Kinase Inhibitors

Biomolecules

The advantage of natural compounds is their lower number of side-effects when compared to most sy... more The advantage of natural compounds is their lower number of side-effects when compared to most synthetic substances. Therefore, over the past several decades, the interest in naturally occurring compounds is increasing in the search for new potent drugs. Natural compounds are playing an important role as a starting point when developing new selective compounds against different diseases. Protein kinases play a huge role in several diseases, like cancers, neurodegenerative diseases, microbial infections, or inflammations. In this review, we give a comprehensive view of natural compounds, which are/were the parent compounds in the development of more potent substances using computational analysis and SAR studies.

Research paper thumbnail of Inhibitory influence of natural flavonoids on human protein kinase CK2 isoforms: effect of the regulatory subunit

Molecular and Cellular Biochemistry

CK2 is a pleiotropic, constitutively active protein kinase responsible for the phosphorylation of... more CK2 is a pleiotropic, constitutively active protein kinase responsible for the phosphorylation of more than 300 physiological substrates. Typically, this enzyme is found in tetrameric form consisting of two regulatory subunits CK2β and two catalytic subunits CK2α or CK2α′. Several natural occurring flavonoids were tested for their ability to inhibit both CK2 holoenzymes, CK2α 2 β 2 and CK2α′ 2 β 2. We identified few substances selectively inhibiting only the α′ subunit. Other compounds showed similar effect towards all four isoforms. In some cases, like chrysoeriol, pedalitin, apigenin, and luteolin, the α 2 β 2 holoenzyme was at least six times better inhibited than the free α subunit. Otherwise, we have found a luteolin derivative decreased the kinase activity of CK2α′ with an IC 50 value of 0.8 μM, but the holoenzyme only with 9.5 µM.

Research paper thumbnail of Selected flavonoid compounds as promising inhibitors of protein kinase CK2α and CK2α′, the catalytic subunits of CK2

Phytochemistry, 2017

CK2 is a ubiquitous protein kinase involved in many cell functions. During the last years it beca... more CK2 is a ubiquitous protein kinase involved in many cell functions. During the last years it became an interesting target in cancer research. A series of flavonoid compounds was tested as inhibitors of protein kinase CK2. Several substances were found to be highly active against both catalytic subunits with IC50 values below 1 μM in case of CK2α'. The most promising inhibitor we identified is chrysoeriol with IC50 values of 250 and 34 nM for CK2α and CK2α', respectively.

Research paper thumbnail of Metalloproteinases of the extracellular matrix and their inhibitors

BioTechnologia, 2016

The dynamic equilibrium between the synthesis and degradation of the extracellular matrix is to a... more The dynamic equilibrium between the synthesis and degradation of the extracellular matrix is to a large extent mediated by matrix metalloproteinase (MMP) enzymes, which are antagonized by tissue inhibitors of metalloproteinases (TIMPs). Tissue-degrading enzymes of the metalloproteinase family have been implicated in the pathogenesis of several conditions involving the extracellular matrix. MMPs are a family of zinc-dependent endopeptidases capable of degrading practically all components of the extracellular matrix. Recent insights suggest that MMPs may also have a broader spectrum of functions, including regulation of the inflammatory response and cytokine signaling. MMPs have been subdivided according to their main degradation activity and the continuously growing list of known substrates. Metalloproteinases are promising drug targets, and they are subjected to pharmacological inhibition by clinically available drugs such as tetracyclines and bisphosphonates. Interest in MMPs has recently increased, because their expression is frequently related to tumor progression. As such, metalloproteinases have diagnostic potential as markers to predict the outcome of disease processes. This review introduces the members of the MMP family and discusses their domain structure and function, their significance in physiology and pathology and the mechanism of inhibition by TIMPs.

Research paper thumbnail of Sensitivity of Protein Kinase CK2 to ATP/GTP and Specific Inhibitors Depends on Complexity of Interacting Proteins

Protein Kinase CK2 Cellular Function in Normal and Disease States, 2015

Research paper thumbnail of Flaviviral Infections and Potential Targets for Antiviral Therapy

Flavivirus Encephalitis, 2011

The family Flaviviridae includes human and animal pathogenic viruses of global importance, e.g. t... more The family Flaviviridae includes human and animal pathogenic viruses of global importance, e.g. the human flaviviruses West-Nile virus (WNV), dengue virus (DENV), Japanese encephalitis virus (JEV), tick-borne encephalitis virus (TBEV) and yellow fever virus (JEV) as well as hepacivirus hepatitis C virus (HCV). This virus family was named after the jaundice occurring in course of YFV infection, the first identified virus of the Flaviviridae (Monath, 1987; Halstead, 1992). In humans infections with Flaviviridae may lead to fulminant, hemorrhagic diseaes [YFV, DENV and omsk hemorrhagic fever virus (OHFV)], viral encephalitis [JEV, TBEV, WNV, St. Louis encephalitis virus (SLEV)] or chronic hepatitis C, formerly referred to as non-A, non-B hepatitis (HCV) (Monath & Heinz, 1996; Rice, 1996). Viruses belonging to the third genus, pestivirus, infect only animals, leading to severe disease of the host, usually followed by death [bovine viral diarrhea virus (BVDV), classical swine fever virus (CSFV) and border disease virus (BDV)] (Nettelton & Entrican, 1995). The genus flavivirus consists of more than 70 species that are, on the basis of phylogenetic analyses, divided into 14 classes which in turn are grouped into three clusters: the mosquitoborne cluster, the tick-borne cluster and the non-vector cluster. All flaviviruses of human importance are mosquito-or tick-borne viruses. They enter through the skin by the bite of an infected arthropod, proliferating locally and spreading through the blood circulation and cross the blood-brain barrier and finally entering the central nervous system. This fact is important for further pathogenesis and unfavorable clinical outcome of the infection (King et al., 2007). Most pathogenic flaviviruses are associated with neurological diseases. The mosquito-borne encephalitic flaviviruses are grouped phylogenetically in the Japanese encephalitis serocomplex. Most tick-borne flaviviruses cause encephalitis and are mainly spread through Europe and Asia. Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae family are registered annually. Up to date, there is no effective antiviral therapy directed against Flaviviridae viruses. Members of the family of Flaviviridae are small (40 to 50 nm), spheric, enveloped RNA viruses of similar structure. The genome of the viruses consists of one single-stranded, positive-sense RNA with a length of 9100 to 11000 bases [e.g. 10862 for YFV (strain 17D), 10477 for Russian spring-summer encephalitis virus (RSSEV) and approx. 9100 for HCV].

Research paper thumbnail of The NTPase/helicase domain of hepatitis C virus nonstructural protein 3 inhibits protein kinase C independently of its NTPase activity

Cellular & Molecular Biology Letters, 2013

Helicase motif VI is a short arginine-rich motif within the NTPase/helicase domain of the non-str... more Helicase motif VI is a short arginine-rich motif within the NTPase/helicase domain of the non-structural protein 3 (NS3) of the hepatitis C virus (HCV). We previously demonstrated that it reduces the catalytic activity and intracellular shuttling of protein kinase C (PKC). Thus, NS3-mediated PKC inhibition may be involved in HCV-associated hepatocellular carcinoma (HCC). In this study, we expand on our earlier results, which were obtained in experiments with short fragments of NS3, to show for the first time that the catalytically active, longer C-terminal NTPase/helicase of NS3 acts as a potent PKC inhibitor in vitro. PKC inhibition assays with the NTPase-inactive mutant NS3h-D1316A revealed a mixed type kinetic inhibition pattern. A broad range of 11 PKC isotypes was tested and all of the PKC isotypes were inhibited with IC50-values in the low micromolar range. These findings were confirmed for the wild-type NTPase/helicase domain in a non-radiometric PKC inhibition assay with ATP...

Research paper thumbnail of Yeast Asf1 Protein as Modulator of Protein Kinase CK2 Activity

Protein Kinase CK2 Cellular Function in Normal and Disease States, 2015

Research paper thumbnail of Inhibition of Flaviviridae Replication Complex: Assays to Investigate the Modulating Effect of Potential Compounds

Current Enzyme Inhibition, 2009

Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae fam... more Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae family, like hepatitis C virus (HCV), West-Nile virus (WNV), dengue virus (DENV) and Japanese encephalitis virus (JEV) are registered annually.

Research paper thumbnail of Viral NS3 helicase activity is inhibited by peptides reproducing the Arg-rich conserved motif of the enzyme (motif VI)

Biochemical Pharmacology, 2008

The NTPase/helicase of Flaviviridae viruses is one of the essential components of their replicati... more The NTPase/helicase of Flaviviridae viruses is one of the essential components of their replication complex. The enzyme is defined by the presence of seven highly conserved amino acid motifs. Random screening of numerous hepatitis C virus (HCV) derived peptides, revealed a basic amino acid stretch corresponding to motif VI of the HCV NTPase/helicase (amino acids 1487-1500 of the HCV polyprotein). This peptide inhibited the unwinding activity of the enzyme with an IC(50)=0.2 microM. Peptides corresponding to motif VI of HCV, West Nile virus (WNV) and Japanese encephalitis virus (JEV) were synthesized and tested as inhibitors of NTPase and unwinding reactions mediated by the viral enzymes. Peptides distinguished in regard to their length and structure. Between the peptides tested HCV(1487-1500) reproducing the sequence of motif VI was the most potent inhibitor of helicase activities of investigated enzymes. Other respective peptides were rather modest inhibitors. The examined peptides inhibited the Flaviviridae helicases in the following order of potency: HCV(1487-1500)>WNV(1959-1572)>JEV(1962-1975). Interestingly, the susceptibility of the helicase activity to the inhibition by the peptides was similar and in the row: HCV>WNV>JEV. The inhibition results from binding and blockade of the active site of the enzyme lyes beyond the NTP-binding and hydrolyzing site. The kinetic analyses indicated that the binding of the peptides do not interfere with the NTPase activity of the enzymes. The peptide may serve as effective and selective tool to reduce the virus propagation.