Cyclin-dependent Protein Kinase 2 Research Articles

In Vitro, Molecular Docking and In Silico ADME/Tox Studies of Emodin and Chrysophanol against Human Colorectal and Cervical Carcinoma.

Anthraquinones (AQs) are present in foods, dietary supplements, pharmaceuticals, and traditional treatments and have a wide spectrum of pharmacological activities. In the search for anti-cancer drugs, AQ derivatives are an important class. In this study, anthraquinone aglycons chrysophanol (Chr), emodin (EM) and FDA-approved anticancer drug fluorouracil were analyzed by molecular docking studies against receptor molecules caspase-3, apoptosis regulator Bcl-2, TRAF2 and NCK-interacting protein kinase (TNIK) and cyclin-dependent protein kinase 2 (CDK2) as novel candidates for future anticancer therapeutic development. The ADMET SAR database was used to predict the toxicity profile and pharmacokinetics of the Chr and EM. Furthermore, in silico results were validated by the in vitro anticancer activity against HCT-116 and HeLa cell lines to determine the anticancer effect. According to the docking studies simulated by the docking program AutoDock Vina 4.0, Chr and EM had good binding energies against the target proteins. It has been observed that Chr and EM show stronger molecular interaction than that of the FDA-approved anticancer drug fluorouracil. In the in vitro results, Chr and EM demonstrated promising anticancer activity in HCT-116 and HeLa cells. These findings lay the groundwork for the potential use of Chr and EM in the treatment of human colorectal and cervical carcinomas.

Synthesis, Characterization and Docking Study of Novel Pyrimidine Derivatives as Anticancer Agents

New compounds 5 and 9 using DNA bases e.g. Adenine 1 and Guanine 6 derivatives have been synthesized. The use of simple methods to synthesize compounds 5 and 9 were done using pyrimidine as an alternative DNA base ring. Another design to synthesize new simple pyrimidine rings utilizing thiourea and ethylcyano acetate to afford 6-amino-2-thiouracil was adopted. The reaction of thiouracil 10 with chloro cyano or chloro ester and ketone, resulted in the formation of adduct compounds 18-21, rather than the formation of compound 17. All the synthesized compounds were subjected to docking study, in order to gain insights into their binding modes against cyclin-dependent protein kinase 2 (CDK-2) that is involved heavily in cell cycle regulation and receptor protein B-cell lymphoma 2 (BCL-2) which is involved in cell apoptosis. These targets were selected based on their key roles in cancer progression via the regulation of the cell cycle and DNA replication. Molecular-docking analyses showed that compound 14e was the best docked ligand against both targets, as it displayed the lowest binding energy, critical hydrogen bonds and hydrophobic interactions with the targets.

Computational and pharmacological investigation of novel 1,5-diaryl-1,4-pentadien-3-one derivatives for analgesic, anti-inflammatory and anticancer potential.

Objective(s):The novel 1,5-diaryl-1,4-pentadien-3-one derivatives were studied for analgesic, anti-inflammatory and anticancer potential to establish their role in pain, inflammatory disorders and cancer.Materials and Methods:Two 1,5- diaryl-1,4-pentadien-3-one derivatives: (1E,4E)- 5-(4-fluoro phenyl)-1-(4-methoxyphenyl)- 2-methylpenta-1,4-dien-3-one (A2K2A17) and (1E,4E)-5-(4-nitrophenyl)-1-(4-nitrophenyl)-2-ethylhexa-1,4-dien-3-one (A11K3A11) were synthesized and characterized via 1H NMR and 13C NMR techniques. Molecular docking, anti-inflammatory, analgesic and anticancer activities were performed using Auto Doc Vina, carrageenan mediated paw edema and formalin induced chronic inflammation, acetic acid induced writhings and hotplate assay and brine-shrimp lethality assay. Results:A2K2A17 and A11K3A11 showed high computational affinities (binding energy > -9.0 Kcal/mol) against COX-1, kappa receptor and braf kinase domain. A2K2A17 and A11K3A11 exhibited moderate docking affinities (binding energy > -8.0 Kcal/mol) against COX-2, human capsaicin receptor, tumor necrosis factor, lipoxygenase, colony stimulating factor, delta receptor, cyclin dependent protein kinase-2, mitogen activated kinase, mu receptor and kit kinase domain. A2K2A17 and A11K3A11 possess low docking affinities (binding energy > -7.0 Kcal/mol) against purinoceptor, platelets-derived growth Factor-1 and vascular-endothelial growth factor. In analgesic activity, A2K2A17 (1-30 mg/kg) and A11K3A11 (1-10 mg/kg) decreased acetic acid induced writhes and prolonged the latency time (P<0.01, P<0.001 vs saline group) respectively. A2K2A17 (10-30 mg/kg) and A11K3A11 (1-10 mg/kg) reduced carrageenan as well as formalin mediated edema (P<0.01, P<0.001). A2K2A17 found effective for cytotoxicity assay with LC50 value 1.5 µg/ml. Conclusion:The in silico, in vitro and in vivo studies on A2K2A17 and A11K3A11 reports their computational binding affinities against targets as well as the analgesic, anti-inflammatory and the anticancer effects.

Docking study on anticancer activity of chromone derivatives

Several phenyl substituted chromones (also called flavonoids) have been reported to possess substantial anticancer properties; however, their modes of action have not been clearly defined. To preliminarily investigate the potential anticancer activity and mode of action of some synthetic chromone derivatives, the docking was performed using different enzymes and receptor proteins involved with cancer cell cycle, cell growth, and DNA replication, i.e., cyclin-dependent protein kinase-2 (CDK-2), CDK-6, DNA topoisomerases I and II, B-cell lymphoma-2 (Bcl-2), vascular endothelial growth factor receptor-2 (VEGFR-2), and the telomere: G-quadruplexes. The docking results revealed that chromone 32 exhibited better binding interactions to CDK-2 and Bcl-2 than the known CDK-2 and Bcl-2 inhibitors. Chromone 39 was found to bind to CDK-6 with tighter interaction than several reported CDK-6 inhibitors. Chromone 47 was best bound to both DNA topoisomerases I and II. Chromones 24 and 15 showed good binding interaction with VEGFR-2 and telomere: G-quadruplex, respectively. The inhibition constants (Ki) of each chromone compound against each target molecule were calculated. These Ki values could be used as a preliminary tool for screening specific inhibitors before performing experimental activity assay.

Molecular mechanical study of halogen bonding in drug discovery

A halogen bond is a noncovalent bond between a halogen atom (X) and a Lewis base (Y). This type of bond is attributed to the anisotropic distribution of the charge density on the halogen atom, resulting in the formation of a positive cap (called the σ-hole) centered on the A-X axis. The current research is the first reported molecular mechanical study of halogen bonding, the positive region centered on the halogen atom was represented by an extra-point (EP) of charge. The correlation between the X-EP distance and the X…Y bond length was explored to determine the optimal position of the EP. A test set of 27 halogen-containing molecules complexed to various Lewis bases was studied using molecular mechanical potentials. The molecular mechanical minimized halogen bond lengths and binding energies were in good agreement with the corresponding quantum mechanical values. The EP inclusion on the halogen atom resulted in an improvement in the accuracy of the electrostatic-potential derived charges. The solvation free energies of halobenzene molecules relative to benzene were calculated with and without EP inclusion to assess the accuracy of the developed approach. Molecular mechanical study of halo derivatives of benzotriazole complexed to cyclin-dependent protein kinase 2 (CDK2) was performed, and MM-PB(GB)SA binding energies were calculated as a case study in finding potent halogenated inhibitors that can serve as antitumor drugs.

BMP-4 Induction of Arrest and Differentiation of Osteoblast-Like Cells via p21CIP1and p27KIP1Regulation

Cell cycle regulation by differentiation signals is critical for eukaryote development. We investigated the roles of bone morphogenetic protein (BMP)-4, an important stimulator of osteoblast differentiation and bone formation, in regulating cell cycle distribution in four osteoblast-like cell lines and mouse primary osteoblasts, and the underlying mechanisms. In all cells used, BMP-4 induced G(0)/G(1) arrest. The molecular basis of the BMP-4 effect was analyzed, and the presentation on molecular mechanism is focused on human MG63 cells. BMP-4 induced p21(CIP1) and p27(KIP1) expressions and hence cell differentiation but had no effects on the expressions of cyclins A, B1, D1, and E, cyclin-dependent protein kinase-2, -4, and -6. Using specific small interfering RNA (siRNA), we found that BMP-4-induced G(0)/G(1) arrest, and p21(CIP1) and p27(KIP1) expressions were mediated by BMP receptor type IA (BMPRIA)-specific Sma- and Mad-related protein (Smad)1/5. BMP-4 induced transient phosphorylations of ERK; transfection of MG63 cells with ERK2, but not ERK1, -specific siRNA inhibited the BMP-4-induced responses in MG63 cells. Pretreatment of MG63 cells with Arg-Gly-Asp-Ser, which blocks the cell-extracellular matrix interaction, or transfection with beta(3) integrin-specific siRNA inhibited BMP-4-induced ERK and Smad1/5 phosphorylations. BMP-4 induced transient increases in associations of beta(3)-integrin with focal adhesion kinase and Shc, the dominant-negative mutants of which inhibited BMP-4-induced ERK and Smad1/5 phosphorylations. Our results indicate that BMP-4 induces G(0)/G(1) arrest and hence differentiation in osteoblast-like cells through increased expressions of p21(CIP1) and p27(KIP1), which are mediated by BMPRIA-specific Smad1/5. The extracellular matrix/beta(3) integrin/ focal adhesion kinase/Shc/ERK2 signaling pathway is involved in these BMP-4-induced responses in osteoblast-like cells.

Molecular docking study on anticancer activity of plant-derived natural products

A variety of compounds from plant sources have been reported to possess substantial anticancer properties; however, their modes of action have not been clearly defined. Selected plant-derived compounds that exhibit anticancer activity were subjected to docking simulations using AutoDock 3.0.5. To preliminarily investigate the potential molecular targets and to confirm the experimental activity testing for these anticancer compounds, the docking was performed using different enzymes and receptor proteins involved with cell cycle, cell growth, and DNA replication, i.e., cyclin-dependent protein kinase 2 (CDK-2), CDK-6, DNA topoisomerases I and II, B-cell lymphoma 2 (Bcl-2), vascular endothelial growth factor receptor 2 (VEGFR-2), and the telomere: G-quadruplexes. The docking results revealed that lupeol exhibited better binding interaction to CDK-2 and Bcl-2 than the known CDK-2 and Bcl-2 inhibitors. Epigallocatechin gallate (EGCG) was found to bind to CDK-6 with tighter interaction than several reported CDK-6 inhibitors. Flavopiridol, a synthetic flavonoid, was best bound to DNA topoisomerase I. Green tea catechin was best docked with topoisomerase II and VEGFR-2 and quercetin showed very good binding interaction with telomere: G-quadruplex. The experimental-derived inhibition constant (Ki) against Bcl-2 and Ki calculated from docking energy were well correlated. Therefore, the calculated Ki could be used as a preliminary tool for screening of Bcl-2 inhibitors before performing experimental activity assay.

Dopamine regulates cell cycle regulatory proteins via cAMP, Ca2+/PKC, MAPKs, and NF‐κB in mouse embryonic stem cells

This study examined the effect of dopamine on DNA synthesis and its related signal cascades in mouse embryonic stem (ES) cells. Dopamine inhibited DNA synthesis in both a dose- and time-dependent manner. Dopamine, SKF 38393 (D1 receptor agonist), and quinpirole (D2 receptor agonist) decreased the level of [(3)H]-thymidine incorporation. The level of cyclic adenosine 3, 5-monophosphate (cAMP) was increased by SKF 38393 but not by quinpirole. The protein kinase C (PKC) protein was translocated from the cytosolic fraction to the membrane compartment by dopamine. Dopamine also increased [Ca(2+)](i), which was blocked by EGTA (an extracellular Ca(2+) chelator), BAPTA-AM (an intracellular Ca(2+) chelator), nifedipine (a L-type Ca(2+) channel blocker), SQ 22536 [an adenylyl cyclase (AC) inhibitor] and neomycin [a phospholipase C (PLC) inhibitor]. Dopamine, SKF 38393, and quinpirole increased the level of p44/42 mitogen-activated protein kinases (MAPKs), p38 MAPK, and stress-activated protein kinase/Jun-N-terminal kinase (SAPK/JNK) phosphorylation. Dopamine also increased level of H(2)O(2) formation and activated the transcription factor family NF-kappaB. Moreover, SKF 38393, quinpirole, and dopamine inhibited cell cycle regulatory proteins, which is consistent with the change in the level of [(3)H]-thymidine incorporation observed. The dopamine-induced decrease in cyclin E, cyclin-dependent protein kinase-2 (CDK-2), and cyclin D1, CDK-4 were blocked by pertussis toxin (G protein inhibitor), SQ 22536, neomycin, bisindolylmaleimide I (PKC inhibitor), SB 203580 (p38 MAPK inhibitor), PD 98059 (p44/42 inhibitor), and SP 600125 (SAPK/JNK inhibitor). In conclusion, dopamine inhibits DNA synthesis in mouse ES cells via the cAMP, Ca(2+)/PKC, MAPKs, and NF-kappaB signaling pathways.

Phosphorylation of Progesterone Receptor Serine 400 Mediates Ligand-Independent Transcriptional Activity in Response to Activation of Cyclin-Dependent Protein Kinase 2

Human progesterone receptors (PR) are phosphorylated by cyclin-dependent protein kinase 2 (CDK2) at multiple sites, including Ser400. Herein, we have addressed the significance of phosphorylation of this residue. PR phospho-Ser400-specific antibodies revealed regulated phosphorylation of Ser400 in response to progestins and mitogens, and this correlated with increased CDK2 levels and activity. Expression of cyclin E elevated CDK2 activity and downregulated PR independently of ligand. Similarly, overexpression of activated mutant CDK2 increased PR transcriptional activity in the absence and presence of progestin. Mutation of PR Ser400 to alanine (S400A) blocked CDK2-induced PR activity in the absence, but not in the presence, of progestin. PR was unresponsive to activated CDK2 in breast cancer cells with elevated p27, and RNA interference knock-down of p27 partially restored CDK2-induced ligand-independent PR activation. Similarly, in p27(-/-) mouse embryonic fibroblasts, elevated CDK2 activity increased wild-type (wt) but not S400A PR transcriptional activity in the absence of progestin. CDK2 induced nuclear localization of unliganded wt but not S400A PR; liganded S400A PR exhibited delayed nuclear accumulation. These studies demonstrate that CDK2 regulates PR in the absence of progestins via phosphorylation of Ser400, thus revealing a novel mechanism for upregulated PR transcriptional activity in human breast cancer cells expressing altered cell cycle regulatory molecules.

Specificity determinants of recruitment peptides bound to phospho-CDK2/cyclin A.

Progression through S phase of the eukaryotic cell cycle is regulated by the action of the cyclin dependent protein kinase 2 (CDK2) in association with cyclin A. CDK2/cyclin A phosphorylates numerous substrates. Substrate specificity often employs a dual recognition strategy in which the sequence flanking the phospho-acceptor site (Ser.Pro.X.Arg/Lys) is recognized by CDK2, while the cyclin A component of the complex contains a hydrophobic site that binds Arg/Lys.X.Leu ("RXL" or "KXL") substrate recruitment motifs. To determine additional sequence specificity motifs around the RXL sequence, we have performed X-ray crystallographic studies at 2.3 A resolution and isothermal calorimetry measurements on complexes of phospho-CDK2/cyclin A with a recruitment peptide derived from E2F1 and with shorter 11-mer peptides from p53, pRb, p27, E2F1, and p107. The results show that the cyclin recruitment site accommodates a second hydrophobic residue either immediately C-terminal or next adjacent to the leucine of the "RXL" motif and that this site makes important contributions to the recruitment peptide recognition. The arginine of the RXL motif contacts a glutamate, Glu220, on the cyclin. In those substrates that contain a KXL motif, no ionic interactions are observed with the lysine. The sequences N-terminal to the "RXL" motif of the individual peptides show no conservation, but nevertheless make common contacts to the cyclin through main chain interactions. Thus, the recruitment site is able to recognize diverse but conformationally constrained target sequences. The observations have implications for the further identification of physiological substrates of CDK2/cyclin A and the design of specific inhibitors.

Effects of Phosphorylation of Threonine 160 on Cyclin-dependent Kinase 2 Structure and Activity

We have prepared phosphorylated cyclin-dependent protein kinase 2 (CDK2) for crystallization using the CDK-activating kinase 1 (CAK1) from Saccharomyces cerevisiae and have grown crystals using microseeding techniques. Phosphorylation of monomeric human CDK2 by CAK1 is more efficient than phosphorylation of the binary CDK2-cyclin A complex. Phosphorylated CDK2 exhibits histone H1 kinase activity corresponding to approximately 0.3% of that observed with the fully activated phosphorylated CDK2-cyclin A complex. Fluorescence measurements have shown that Thr160 phosphorylation increases the affinity of CDK2 for both histone substrate and ATP and decreases its affinity for ADP. By contrast, phosphorylation of CDK2 has a negligible effect on the affinity for cyclin A. The crystal structures of the ATP-bound forms of phosphorylated CDK2 and unphosphorylated CDK2 have been solved at 2.1-A resolution. The structures are similar, with the major difference occurring in the activation segment, which is disordered in phosphorylated CDK2. The greater mobility of the activation segment in phosphorylated CDK2 and the absence of spontaneous crystallization suggest that phosphorylated CDK2 may adopt several different mobile states. The majority of these states are likely to correspond to inactive conformations, but a small fraction of phosphorylated CDK2 may be in an active conformation and hence explain the basal activity observed.