Fosfatase Cdc25B: Interações transientes intramoleculares e complexação com pequenos ligantes / Cdc25B phosphatase: Transient intramolecular interactions and small molecules complexation

Proteínas tirosina-fosfatase (PTPs) possuem papel fundamental na regulação da transdução de sinais e estão envolvidas em diversos processos fundamentais do ciclo celular. As Cdc25 (Cell Division Cycle 25) são fosfatases duais encontradas em todos os organismos eucarióticos e atuam em checkpoints do ciclo celular, permitindo ou inibindo o prosseguimento deste. Este grupo de proteínas pertence à classe de PTPs com atividade baseada em cisteína, apresenta domínio catalítico altamente conservado assim como o motivo catalítico, P-loop. Devido sua função, as Cdc25 são consideradas possíveis alvos terapêuticos para tratamento de câncer e sua interação com pequenas moléculas e inibidores tem sido investigada de forma que análises estruturais e de ligação das Cdc25 com inibidores podem elucidar aspectos importantes do mecanismo de ação destes além de direcionar para o desenho racional de fármacos. Interações cátion-π são interações intra ou intermoleculares não-covalentes que ocorrem entre uma espécie química catiônica, como o grupo guanidino de argininas, e uma das faces de um sistema π rico em elétrons, como dos anéis indólicos de triptofanos. Apesar de pouco discutidas na literatura, quando em comparação às interações não-covalentes mais convencionais, do ponto de vista energético as interações cátion-π são tão importantes na estruturação de proteínas quanto às ligações de hidrogênio ou pontes salinas. De fato estas interações são observadas com frequência em estruturas proteicas resolvidas. O domínio catalítico da Cdc25B possui diversas argininas expostas em sua superfície e um único resíduo de triptofano localizado na região C-terminal flexível, muito próximo do sítio catalítico da proteína. A flexibilidade de proteínas ou de regiões proteicas apresenta importante papel no reconhecimento entre biomoléculas participantes de vias de sinalização e tem sido muito estudada atualmente. Aqui, simulações de dinâmica molecular, experimentos de 1H-15N HSQC RMN, ensaios de cinética de inibição e de ancoragem molecular, evidenciam a existência de contatos cátion-π transientes na superfície de um importante membro da família das Cdc25, a Cdc25B, e de sítios de interação entre inibidores testados e a proteína com destaque a sítios na proximidades do P-loop, região próxima ao C-terminal desordenado, onde se demonstra estabilidade da interação com os pequenos ligantes

Protein tyrosine phosphatase (PTPs) play a fundamental role in the regulation of signal transduction and are involved in several fundamental processes of the cell cycle. Cdc25 (Cell Division Cycle 25) are dual phosphatases found in all eukaryotic organisms and act at checkpoints of the cell cycle, allowing or inhibiting its progression. This group of proteins belongs to the class of PTPs with cysteine-based activity, presenting a highly conserved catalytic domain as well as the catalytic motif, P-loop. Due to their function, Cdc25 are considered possible therapeutic targets for cancer treatment and their interaction with small molecules and inhibitors has been investigated so that structural and binding analyzes of Cdc25 with inhibitors can elucidate important aspects of their mechanism of action besides directing to rational drug design. Cation-π interactions are non-covalent intra- or intermolecular interactions that occur between a cationic chemical species, such as the guanidino group of arginines, and one of the faces of an electron-rich system, such as the indole rings of tryptophans. Although little discussed in the literature, when compared to more conventional non-covalent interactions, from the energetic point of view, cation-π interactions are as important in the structuring of proteins as hydrogen bonds or salt bridges. In fact, these interactions are frequently observed in solved protein structures. The catalytic domain of Cdc25B has several arginines exposed on its surface and a single tryptophan residue located in the flexible C-terminal region, very close to the catalytic site of the protein. The flexibility of proteins or protein regions plays an important role in the recognition between biomolecules participating in signaling pathways and has been extensively studied today. Here, molecular dynamics simulations, 1H-15N HSQC NMR experiments, inhibition kinetics and molecular anchoring assays, evidence the existence of transient cation-π contacts on the surface of an important member of the Cdc25 family, Cdc25B, and of sites of interaction between tested inhibitors and the protein, with emphasis on sites in the vicinity of the P-loop, a region close to the disordered C-terminus, where stability of the interaction with the small ligands is demonstrated

Biological evaluation of 2,3-dioxoindolin-N-phenylacetamide derivatives as potent CDC25B and PTP1B phosphatase inhibitors

A series of 2,3-dioxoindolin-N-phenylacetamide derivatives was evaluated for inhibitory activity against CDC25B and PTP1B enzymes. Most of the derivatives showed inhibitory activity against CDC25B (IC50 = 3.2-23.2 µg/mL) and PTP1B (IC50 = 2.9-21.4 µg/mL). Compound 2h showed the most inhibitory activity in vitro with IC50 values of 3.2 and 2.9 µg/mL against CDC25B and PTP1B, respectively, compared with the reference drugs Na3VO4 (IC50 = 2.7 µg/mL) and oleanolic acid (IC50 = 2.3 µg/mL). The results of selectivity experiments showed that the 2,3-dioxoindolin-N-phenylacetamide derivatives were selective inhibitors against CDC25B and PTP1B. Enzyme kinetic experiments demonstrated that compound 2h was a specific inhibitor with the typical characteristics of a mixed inhibitor. In cytotoxic activity assays compound 2h had potent activity against A549, HeLa, and HCT116 cell lines. In addition, compound 2h showed potent tumor inhibitory activity in a colo205 xenograft model in vivo.

Development of a Novel Nonradioisotopic Assay and Cdc25B Overexpression Cell Lines for Use in Screening for Cdc25B Inhibitors

PURPOSE: The cyclin-dependent kinase 1 (Cdk1) and cyclin B complex performs important roles in the transition from the G2 to M phase in the cell cycle through removal of inhibitory phosphates on Cdk1, and Cdc25B, which is a dual-specific phosphatase, mediates these dephosphorylation events. However, measuring Cdc25B activity by existing methods is hampered by inadequate nonspecific substrates and the need to use a radiolabeled isotope. The present study aimed to develop an improved method with which to properly measure Cdc25B activity using a novel nonradioisotopic assay and Cdc25B overexpression cell lines. MATERIALS AND METHODS: A nonradioisotopic Cdk1 kinase assay, based on Western blotting for retinoblastoma protein and histone H1, was used to analyze Cdc25B activity. Also, stable Cdc25B2 and Cdc25B3 overexpression HeLa cell lines were constructed using the tetracycline-regulated expression system and were applied as a tool for screening for inhibitors of Cdc25B. RESULTS: The present study developed and optimized a nonradioisotopic assay method to properly measure Cdc25B activity. Furthermore, we constructed stable Cdc25B2 and Cdc25B3 overexpression HeLa cell lines for the establishment of a strong assay system with which to evaluate the specificity of Cdc25B inhibitors under conditions similar to the intracellular environment. These methods were confirmed as useful tools for measuring Cdc25B activity. CONCLUSION: The nonradioisotopic Cdk1 kinase assay and Cdc25B overexpression cell lines developed in this study can be conveniently used as tools for screening inhibitors of Cdc25B phosphatase as anticancer drugs.

A Novel Derivative of Panax Notoginseng Sapogenin and Its Antitumor Activity / 昆明医科大学学报

Objective To research the derivatives of panax notoginseng sapogenins and their anti-tumor activities. Methods The ginsenosides Rg1 was treated with Smith degradation. The products were separated and purified by silica gel column chromatography. The structures of the products were determined by NMR spectra. The activity of anti-tumor cells of compound (1) and 1'-hydroxyethanedioxy PT was detected with CDC25B activity assay and fluorescence technique. Results 1'-hydroxyethanedioxy PT , 20 (s)-protopanaxatriol (PT), and 24, 25 - en-3β, 6 α-dihydroxy-12, 20-(1', 2'-isopropylidenedioxy) propanedioxy-dammarane (1) were isolated and identified. Conclusion Compound (1), named 1',2'-isopropylidenedioxy-propanedioxy-pro-panedioxy , is a novel derivative of panax notoginseng sapogenin with better inhibitory activity against CDC25B.

Effect of 14-3-3ε protein on localization of Cdc25B during meiotic resumption of mouse oocytes / 吉林大学学报(医学版)

Objective:To explore the effect of 14-3-3εprotein on the localization of Cdc25B protein during the meiotic resumption of mouse oocytes,and to pay foundation for the further study on the molecular mechanism of 14-3-3εprotein in regulating the development of mouse oocytes.Methods:The Kunming genealology female mice aged 3 weeks were used to obtain the germinal vesicle (GV)-stage oocytes after superovulation.The GV-stage oocytes were divided into non-injection group,control siRNA injection group and 14-3-3εsiRNA injection group. The pmax-FP-Red-HA-14-3-3εexpression vector was constructed.Indirect immunofluorescence was used to observe the colocalization of 14-3-3εprotein and Cdc25B protein in the mouse oocytes;direct immunofluorescence was used to observe the subcellular localization of 14-3-3εprotein and Cdc25B protein in the mouse oocytes;14-3-3εsiRNA was microinj ected into the GV-stage oocytes;the morphology was observed under phase-contrast microscope;the germinal vesicle breakdown (GVDB)rates of the mouse oocytes were calculated;the expression level of 14-3-3εprotein and the relative expression level of Cdc2-pTyr15 protein were observed by Western blotting method;the matuation-promoting factor (MPF)activity in the oocytes was measured by autoradiography.Results:The indirect immunofluorescence and direct immunofluorescence results showed that the 14-3-3εprotein and wild Cdc25B protein were co-localized in the cytoplasm;Cdc25B was translocated from the cytoplasm to the nucleus shortly before GVBD.When the Ser321 of Cdc25B protein turned into Ala,the expression level of 14-3-3εprotein was decreased. None of the oocytes in non-injection group and control siRNA injection group were able to undergo GVBD until at least 24 h after injection,there was no significant differences in the rate of GVBD between non-injection group and control siRNA injection group (P>0.05);the GVBD rates of oocytes in 14-3-3εsiRNA injection group at 22 and 24 h after injection were significantly higher than those in non-injection group and control siRNA injection group (P<0.01);the rate of oocytes progressed to metaphaseⅡ (MII)in 14-3-3εsiRNA injection group at 24 h after injection was significantly higher than those in non-injection group and control siRNA injection group (P<0.01). Conclusion:Ser321 might be involved in the process of regulating the subcellular localization of Cdc25B by 14-3-3εprotein in the meiotic resumption of mouse oocytes.

Role of 1 4-3-3εand Cdc25B in GV-stage arrest of mouse oocytes / 吉林大学学报(医学版)

Objective:To study the role of 14-3-3εand Cdc25B in germinal vesicle (GV)-stage arrest of mouse oocytes,and to pay foundation for further study on the molecular mechanism of PKA/Cdc25B/14-3-3εpathway in GV-stage arrest of mouse oocytes.Methods:The eukaryotic expression vectors of pcDNA3.1-ZEO-HA-14-3-3ε, pcDNA3.1-MYC-Cdc25B-WT, pcDNA3.1-MYC-Cdc25B-S321A, and pcDNA3.1-MYC-Cdc25B-S321D were transcribed into mRNA invitro.The mouse GV-stage oocytes were collected after superovulation and divided into no injection group,TE buffer microinjection group,14-3-3εmRNA injection group,14-3-3εmRNAs + Cdc25B-WT mRNA injection group,and 14-3-3εmRNA + Cdc25B-S321A mRNA injection group,14-3-3εmRNA+Cdc25B-S321D mRNA injection group.The protein expression levels of HA-14-3-3εand MYC-Cdc25B and the phosphorylation status of Cdc2-pTyr15 were observed by Western blotting method.The morphological changes and germinal vesicle breakdown (GVDB)rates of mouse oocytes were observed under phase-contrast microscope. Results:None of the oocytes in no injection group, TE buffer microinjection group, 14-3-3εmRNA injection group,14-3-3εmRNA + Cdc25B-WT mRNAs injection group and 14-3-3εmRNA + Cdc25B-S321D mRNA were able to undergo GVBD until at least 20 h after injection (P>0.05 );the GVBD rates of oocytes in 14-3-3εmRNA+Cdc25B-S321A mRNA group at 1 h (5.00%±0.68%),2 h (62.00%±3.56%)and 3 h (100.00%± 0.00%)after injection were significantly higher than those in no injection group and TE buffer injection group (P<0.01);the oocytes in 14-3-3εmRNA+ Cdc25B-Ser321A mRNA group at 20 h (79.00%±2.80%)after injection progressed to MII (P<0.01).Conclusion:14-3-3εcan regulate the transition from GV to GVBD of mouse oocytes by means of phosphorylation and dephosphorylation of S321-Cdc25B.

Expression of Cdc25A, Cdc25B and Cdc25C in cervical carcinoma / 대한산부인과학회지

OBJECTIVE: This study was undertaken to quantitatively detect Cdc25A, Cdc25B and Cdc25C in cervical carcinoma and determine the relationship between the expression of mRNA and protein of cell division cycle (Cdc)25 phosphatase and various clinicopathologic prognostic factors of cervical carcinoma. METHODS: 39 patients diagnosed with cervical carcinoma between February 2000 to March 2005 and 10 patients with benign gynecologic disease were enrolled in this study. A reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis were used to analyze the expression of Cdc25 phosphatase mRNA and protein in fresh invasive cervical cancer tissue and normal cervix tissue. RESULTS: The mRNA expressions of Cdc25A, Cdc25B and Cdc25C in the cancer tissues were significantly greater than in the control (p=0.02, 0.01, 0.02), respectively. A Western blot analysis yielded same results (p=0.01, 0.02, 0.01). There were also significant relationships between the age and the Cdc25B mRNA expression (p=0.03), between the cell type and the Cdc25C mRNA expression (p=0.04). However, other clinicopathologic prognostic factors including stage, subtype, SCC Ag level, DNA flow cytometry, lymph node metastasis, lymphovascular space invasion and HPV positivity were not statistically significant. CONCLUSION: Our results show that Cdc25A, Cdc25B and Cdc25C expression levels were significantly greater in cervical cancer patient group than in those of control group. Thus Cdc25 phosphatase might play an important role in carcinogenesis of cervical carcinoma. Further studies based on the correlation between Cdc25 phosphatase and survival rate would be need to support Cdc25 phosphatase as a prognostic factor of cervical carcinoma.

THE EXPRESSION OF CDC25B IN COLORECTAL CANCER AND ADENOMA AND ITS CLINICAL SIGNIFICANCE / 解放军医学杂志

To explore the role of CDC25B in pathogenesis and development of colorectal cancer and to investigate the relation between the expression of CDC25B and the clinical pathological character of colorectal cancer and the prognosis of patients. The expression of CDC25B in 168 patients with colorectal cancer and 25 patients with adenoma, and normal colorectal mucosa from 20 individuals was assayed by immunohistochemistry (S-P method). The expression of CDC25B was not detected in adenoma and normal colorectal mucosa. The expression rate of CDC25B in colorectal cancer was 71.4%(120/168). The expression of CDC25B had a positive correlation with distant metastasis and the increase of CEA,while it had no relationship with the tumor stage, grade, lymph node metastases, gender, age or the size of tumor . The patients in whom expression of CDC25B was detected had a markedly low 5-year survival rate. The results suggested that expression of CDC25B in colorectal cancer might accelerate the transformation of cell cycle,which promoted metastasis to distant organ, indicating that the expression of CDC25B might play a role in the development of colorectal cancer. The expression of CDC25B was a risk factor of poor prognosis.

The influence of 149 serine on the localization of cdc25b protein in mouse oocytes / 中国免疫学杂志

Objective:To study the mechanism of 149 serine in the abrogation of cdc25b as a meiosis inducer in mouse oocytes.Methods: Immunofluorescence analysis was used to observe the distribution of cdc25b protein in GV stage and G2/M transition oocytes;Fused plasmids of pEGFP-cdc25b-wt,pEGFP-cdc25b-s149a and vector pEGFP-C3 were microinjected into GV mouse oocytes.After culturing for a certain time,the subcellular localization of protein was observed.Results:cdc25b-wt was distributed mainly in cytoplasm in GV stage oocytes and accumulation of protein was observed during G2/M transition while green fluoresent signal of cdc25b-s149a was observed in nuclear and cytoplasm.Conclusion:The results suggest that there existed a shuffling between nuclear and cytoplasm of cdc25b in GV stage oocytes although they seem to be quilt,the phosphorylation of 149 serine could maintain proper distribution of protein by balancing the speed of protein nuclear export and nuclear import.