Roles of Id1/HIF-1 and CDK5/HIF-1 in cell cycle reentry induced by amyloid-beta peptide in post-mitotic cortical neuron

One neurotoxic mechanism of amyloid-beta peptide (Aβ), the major component of senile plaques in the brains of Alzheimer's disease (AD) patients, is to trigger cell cycle reentry in fully differentiated neurons. However, the detailed underlying mechanisms remain unclear. Using Aβ25-35–treated primary rat cortical neurons as the experimental system, in the present study we tested whether Aβ-induced inhibitor of differentiation-1 (Id1)/hypoxia-inducible factor-1alpha (HIF-1α) and cyclin-dependent kinase-5 (CDK5) contribute to cell cycle reentry in fully differentiated post-mitotic neurons. We found that Id1-induced HIF-1α mediated Aβ25-35–dependent expression of the cell cycle markers cyclin D1 and proliferating cell nuclear antigen (PCNA), both colocalized with microtubule-associated protein-2 (MAP-2) ⁺ cells, indicative of cell cycle reentry in the mature neurons. Aβ25-35 also enhanced p35 cleavage to p25 without affecting CDK5 expression. The CDK5 inhibitor roscovitine and the siRNA targeting CDK5 both suppressed Aβ25-35–dependent HIF-1α expression and cell cycle reentry. Intriguingly, Aβ25-35–induced Id1 repressed p25 production while CDK5/p25 reciprocally inhibited Id1 expression, despite the observation that both Id1 and CDK5/p25 acted upstream of HIF-1α. These results demonstrated that both Id1/HIF-1 and CDK5/HIF-1 contribute to Aβ-induced cell cycle reentry in post-mitotic neurons; furthermore, Id1 and CDK5/p25 reciprocally suppress expression of each other.     

Synthesis of eudistomin D analogues and its effects on adenosine receptors

Six analogues (1-6) of eudistomin D, a beta-carboline alkaloid from a marine tunicate Eudistoma olivaceum, were synthesized, and their affinity and selectivity for adenosine receptors A(1), A(2A), and A(3) were examined. All the synthetic compounds 1-6 did not show affinity to the adenosine A(1) receptor. Delta-carboline 3 exhibited the most potent affinity to the adenosine receptor A(3) among compounds 1-6. Delta-carbolines 3 and 4 showed better affinity than the corresponding beta-carbolines 1 and 2, respectively, while N-methylation (2, 4, and 6, respectively) of the pyrrole ring in 1, 3, and 5 resulted in the reduced affinity to the adenosine A(3) receptor. On the other hand, an eudistomin D derivative, BED, exhibited modest affinity to all the receptors A(1), A(2A), and A(3) but no selectivity.     

Long non-coding RNA OIP5-AS1 promotes pancreatic cancer cell growth through sponging miR-342-3p via AKT/ERK signaling pathway

Opa-interacting protein 5 antisense RNA 1 (OIP5-AS1), a long non-coding RNA (lncRNA), has been reported to link with the progression of some cancers. However, its biological functions and underlying molecular mechanisms in pancreatic cancer are largely unknown. The aim of this study was to investigate the role of lncRNA OIP5-AS1 in pancreatic cancer. Quantitative real-time PCR analysis revealed that OIP5-AS1 is highly expressed in pancreatic cancer tissues versus adjacent non-tumor tissues. In vitro functional assays showed that downregulation of OIP5-AS1 or overexpression of miR-342-3p inhibited the proliferation, decreased Ki67 expression, and induced cell cycle arrest in pancreatic cancer cells. The expression of cyclinD1, CDK4, and CDK6 was decreased by knockdown of OIP5-AS1. Moreover, we found that OIP5-AS1 acted as a miR-342-3p sponge to suppress its expression and function. Dual-luciferase assay confirmed the interaction of OIP5-AS1 and miR-342-3p and verified anterior gradient 2 (AGR2) as a direct target of miR-342-3p. Results showed that depletion of miR-342-3p abolished the inhibitory effects of OIP5-AS1 knockdown on pancreatic cancer cell growth. The expression of Ki67, AGR2, cyclinD1, CDK4, CDK6, p-AKT, and p-ERK1/2 was reversed by silencing of miR-342-3p in pancreatic cancer cells with OIP5-AS1 knockdown. Further, knockdown of OIP5-AS1 suppressed tumor growth in a xenograft mouse model of pancreatic cancer. OIP5-AS1 induced pancreatic cancer progression via activation of AKT and ERK signaling pathways. Therefore, we demonstrate that OIP5-AS1 functions as oncogene in pancreatic cancer and its downregulation inhibits pancreatic cancer growth by sponging miR-342-3p via targeting AGR2 through inhibiting AKT/ERK signaling pathway.

     

The dynamic mobility of histone H1 is regulated by cyclin/CDK phosphorylation

The linker histone H1 is involved in maintaining higher-order chromatin structures and displays dynamic nuclear mobility, which may be regulated by posttranslational modifications. To analyze the effect of H1 tail phosphorylation on the modulation of the histone's nuclear dynamics, we generated a mutant histone H1, referred to as M1-5, in which the five cyclin-dependent kinase phosphorylation consensus sites were mutated from serine or threonine residues into alanines. Cyclin E/CDK2 or cyclin A/CDK2 cannot phosphorylate the mutant in vitro. Using the technique of fluorescence recovery after photobleaching, we observed that the mobility of a green fluorescent protein (GFP)-M1-5 fusion protein is decreased compared to that of a GFP-wild-type H1 fusion protein. In addition, recovery of H1 correlated with CDK2 activity, as GFP-H1 mobility was decreased in cells with low CDK2 activity. Blocking the activity of CDK2 by p21 expression decreased the mobility of GFP-H1 but not that of GFP-M1-5. Finally, the level and rate of recovery of cyan fluorescent protein (CFP)-M1-5 were lower than those of CFP-H1 specifically in heterochromatic regions. These data suggest that CDK2 phosphorylates histone H1 in vivo, resulting in a more open chromatin structure by destabilizing H1-chromatin interactions.     

Discovery of cyclin-dependent kinase inhibitor, CR229, using structurebased drug screening

To generate new scaffold candidates as highly selective and potent cyclin-dependent kinase (CDK) inhibitors, structure-based drug screening was performed utilizing 3D pharmacophore conformations of known potent inhibitors. As a result, CR229 (6-bromo-2,3,4,9-tetrahydro-carbolin-1-one) was generated as the hit-compound. A computational docking study using the X-ray crystallographic structure of CDK2 in complex with CR229 was evaluated. This predicted binding mode study of CR229 with CDK2 demonstrated that CR229 interacted effectively with the Leu83 and Glu81 residues in the ATP-binding pocket of CDK2 for the possible hydrogen bond formation. Furthermore, biochemical studies on inhibitory effects of CR229 on various kinases in the human cervical cancer HeLa cells demonstrated that CR229 was a potent inhibitor of CDK2 (IC50: 3 microM), CDK1 (IC50: 4.9 microM), and CDK4 (IC50: 3 microM), yet had much less inhibitory effect (IC50: >20 microM) on other kinases, such as casein kinase 2-1 (CK2- alpha1), protein kinase A (PKA), and protein kinase C (PKC). Accordingly, these data demonstrate that CR229 is a potent CDK inhibitor with anticancer efficacy.     

猪miR-331-3p过表达载体的构建及其对细胞增殖的影响

本研究旨在阐明猪miR-331-3p对细胞增殖的影响,探讨其对细胞增殖的作用机制首先构建了miR-331-3p的过表达载体pcDNA 3.1 (+)-miR-331-3p,并将将PK15细胞分为4组,分别为实验组、实验组对照组、抑制剂组和抑制剂对照组。实验组和对照组分别转染pcDNA 3.1(+)-miR-331-3p和pcDNA 3.1(+)。抑制剂组和抑制剂对照组分别转染miR-331-3p Inhibitor和miR-331-3p阴性对照(miR-331-3p NC)。通过在各组添加CCK-8试剂绘制细胞增殖曲线,并使用PI染色检测细胞所处周期比例。同时,利用实时荧光定量PCR(Quantitative real-time PCR,qPCR)检测生长抑制蛋白家族成员5 (Inhibitor of growth family member 5,ING5)、细胞周期蛋白依赖性激酶2 (Cyclin dependent kinase 2,CDK2)、细胞周期蛋白依赖性激酶3 (Cyclin dependent kinase 3,CDK3)、细胞周期蛋白依赖性激酶4 (Cyclin dependent kinase 4,CDK4)、细胞周期蛋白B (Cyclin B)和细胞周期蛋白依赖性激酶抑制剂1A(Cyclindependentkinaseinhibitor1A,CDKN1A)的表达变化。结果表明,实验组miR-331-3p表达量显著升高,细胞增殖曲线表明48 h和72 h时细胞数目均呈现出实验组实验对照组和抑制剂对照组抑制剂组的趋势(P0.05)。与实验对照组相比,实验组处于G0/G1期的细胞比例下调,S期和G2/M细胞的比例上调,抑制剂对照组趋势与之相反;同时,实验组中与促进增殖的基因CDK2、CDK3、CDK4和CyclinB的mRNA表达水平均显著升高,而抑制增殖的基因ING5和CDKN1A均表现出显著下降的趋势。本研究成功构建了miR-331-3p过表达载体,且发现miR-331-3p具有促进猪肾上皮细胞增殖的能力,研究结果为深入研究miR-331-3p在猪生长发育中的作用机制奠定了基础。     

Synthesis of acridinyl-thiazolino derivatives and their evaluation for anti-inflammatory, analgesic and kinase inhibition activities

Variety of N-(4-phenyl-3-(2',3',4'(un)substituted phenyl)thiazol-2(3H)-ylidene)-2,4(un)substituted acridin-9-amine (4a-o) and 1-[(2,4-(un)substituted acridin-9-yl)-3-(4-phenyl-3-(2',3',4'(un)substituted phenyl)thiazol-2(3H)-ylidene)]isothiourea (5a-h) derivatives have been synthesized by condensation of 4-phenyl-3-(2',3',4'(un)substituted phenyl)thiazol-2(3H)-imine (3a-g) with 9-chloro-2,4-(un)substituted acridine (1a-c) and 9-isothiocyanato-2,4-(un)substituted acridine (2a-d), respectively. All these compounds were characterized by correct 1H NMR, FT-IR, MS and elemental analyses. These compounds were screened for anti-inflammatory, analgesic and kinase (CDK1, CDK5 and GSK3) inhibition activities. Some compounds exhibited good anti-inflammatory (25-32%) and potent analgesic (50-75%) activities, at 50 mg/kg p.o. A compound, 4o (R1 = H, R2 = OCH3, R3 = CH3, R4 = CH3, R5 = H) exhibited moderate CDK1 (IC50 = 8.5 microM) inhibition activity.     

Peroxisome proliferator-activated receptor gamma ligands, 15-deoxy-Delta12,14-prostaglandin J2, and ciglitazone, induce growth inhibition and cell cycle arrest in hepatic oval cells

There is growing evidence to show that hepatic oval cells contribute to liver regeneration, dysplastic nodule formation, and hepato-carcinogenesis. Peroxisome proliferator-activated receptors (PPARs) and their ligands play an important role in cell growth, inflammatory responses, and liver pathogenesis including fibrosis and cancer. However, little is known about the role of PPARgamma/its ligands in the growth and differentiation of hepatic oval cells. In this study, we found that OC15-5, a rat hepatic oval cell line, expressed PPARgamma at mRNA and protein levels, and a natural ligand for PPARgamma, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), and a synthetic ligand, ciglitazone, inhibited growth of OC15-5 cells by arresting at G1-S in a dose-dependent manner. Apoptosis was also induced in OC15-5 cells by 15d-PGJ2 treatment. In OC15-5 cells treated with 15d-PGJ2, the expression of CDK inhibitor, p27(Kip1), was up-regulated, while that of p21(WAF1/Cip1), p18(INK4C) CDK2, CDK4, and cyclin E was unchanged. In addition, delayed up-regulation of AFP expression was observed in OC15-5 cells after 15d-PGJ2 or ciglitazone treatment. This is the first report to show that the PPARgamma ligand was involved in the growth, cell cycle, and differentiation of hepatic oval cells, raising the possibility that the PPARgamma ligands may regulate liver regeneration and hepato-carcinogenesis.     

Different mechanisms of CDK5 and CDK2 activation as revealed by CDK5/p25 and CDK2/cyclin A dynamics

A detailed analysis is presented of the dynamics of human CDK5 in complexes with the protein activator p25 and the purine-like inhibitor roscovitine. These and other findings related to the activation of CDK5 are critically reviewed from a molecular perspective. In addition, the results obtained on the behavior of CDK5 are compared with data on CDK2 to assess the differences and similarities between the two kinases in terms of (i) roscovitine binding, (ii) regulatory subunit association, (iii) conformational changes in the T-loop following CDK/regulatory subunit complex formation, and (iv) specificity in CDK/regulatory subunit recognition. An energy decomposition analysis, used for these purposes, revealed why the binding of p25 alone is sufficient to stabilize the extended active T-loop conformation of CDK5, whereas the equivalent conformational change in CDK2 requires both the binding of cyclin A and phosphorylation of the Thr(160) residue. The interaction energy of the CDK5 T-loop with p25 is about 26 kcal.mol(-1) greater than that of the CDK2 T-loop with cyclin A. The binding pattern between CDK5 and p25 was compared with that of CDK2/cyclin A to find specific regions involved in CDK/regulatory subunit recognition. The analyses performed revealed that the alphaNT-helix of cyclin A interacts with the alpha6-alpha7 loop and the alpha7 helix of CDK2, but these regions do not interact in the CDK5/p25 complex. Further differences between the CDK5/p25 and CDK2/cyclin A systems studied are discussed with respect to their specific functionality.     

Induction of Apoptosis in Human Leukemia Cells by the CDK1 Inhibitor

We have examined the effects of the CDK1 inhibitor CGP74514A on cell cycle- and apoptosis-related events in human leukemia cells. An 18-hr exposure to 5 mM CGP74514A induced mitochondrial damage (i.e., loss of Dym) and apoptosis in multiple human leukemia cell lines (e.g., U937, HL-60, KG-1, CCRF-CEM, Raji, and THP; range 30-95%). In U937 cells, CGP74514A- induced apoptosis (5 mM) became apparent within 4 hr and approached 100% by 24 hr. The pan- caspase inhibitor Boc-fmk and the caspase-8 inhibitor IETD-fmk opposed CGP74514A-induced caspase-9 activation and PARP degradation, but not cytochrome c or Smac/DIABLO release. CGP74514A-mediated apoptosis was substantially blocked by ectopic expression of full-length Bcl- 2, a loop-deleted mutant Bcl-2, and Bcl-xL. CGP74514A treatment (5 mM; 18 hr) resulted in increased p21CIP1 expression, p27KIP1 degradation, diminished E2F1 expression, and dephosphorylation of p34cdc2. It also induced early (i.e., within 2 hr) inhibition of CDK1 activity and dephosphorylation of pRb, followed by pRb degradation, but did not block pRb phosphorylation at CDK2- and CDK4- specific sites. These findings indicate that the selective CDK1 inhibitor, CGP74514A, induces complex changes in cell cycle-related proteins in human leukemia cells accompanied by extensive mitochondrial damage, caspase activation, and apoptosis.

Key Words:

Leukemia, CDK1 Inhibitor, Apoptosis, CGP74514A     

Molecular model of cyclin-dependent kinase 5 complexed with roscovitine

Here is described a structural model for the binary complex CDK5-roscovitine. Roscovitine has been shown to potently inhibit cyclin-dependent kinases 1, 2 and 5 (CDK1, 2, and 5), and the structure of CDK2 complexed with roscovitine has been reported; however, no structural data are available for complexes of CDK5 with inhibitors. The structural model indicates that roscovitine strongly binds to the ATP-binding pocket of CDK5 and structural comparison of the CDK2-roscovitine complex correlates the structural differences with differences in inhibition of these CDKs by this inhibitor. This structure opens the possibility of testing new inhibitor families, in addition to new substituents for the already known lead structures of adenine derivatives.     

Conformationally constrained N1-arylsulfonyltryptamine derivatives as 5-HT6 receptor antagonists

Several series of conformationally constrained N1-arylsulfonyltryptamine derivatives were prepared and tested for 5-HT6 receptor binding affinity and ability to modulate cAMP production in a cyclase assay. The 3-piperidin-3-yl-, 3-(1-methylpyrrolidin-2-ylmethyl)-, and 3-pyrrolidin-3-yl-1H-indole arrays (8-13) appear to be able to adopt a conformation that allows high affinity 5-HT6 receptor binding, while the beta-carboline array 14 binds with a significantly weaker (10- to 100-fold) affinity. N1-Benzenesulfonyl-3-piperidin-3-yl-1H-indole 9a is a high affinity full agonist with EC50 = 24 nM. Several of the N1-arylsulfonyl-3-(1-methylpyrrolidin-2-ylmethyl)-1H-indole derivatives behave as very potent antagonists ((S)-11r, (S)-11t; IC50 = 0.8, 1.0 nM).     

Key role for cyclin-dependent kinases in the first and second meiotic divisions of rat spermatocytes

In all systems examined so far, the G2/M phase transition is controlled by the M-phase promoting factor (MPF), a complex of cdc2 (CDK1) and cyclin B1. Histone H1 kinase activity and MPF components are present in pachytene spermatocytes (PS). However, it has not been demonstrated yet that direct inhibition of MPF activity prevents the G2/M transition in these cells. When roscovitine, a potent inhibitor of CDK1, CDK2, and CDK5 activities, was added to cocultures of PS with Sertoli cells, the number of both secondary spermatocytes and round spermatids formed were lower than in control cultures, despite similar cell viability. This effect of roscovitine was reversible, did not involve the Sertoli cells, and was dependent on the concentration of the inhibitor. Roscovitine did not modify the amount of MPF in these germ cells but inhibited the CDK1- or CDK2-associated histone H1 kinase activity of PS. Hence a functional relationship between cyclin-dependent kinase activity and the spontaneous processing of the first meiotic division and, for the first time, of the second meiotic division of male germ cells is shown.     

Design and synthesis of 4-(2,3-dihydro-1H-benzo[d]pyrrolo[1,2-a]imidazol-7-yl)-N-(5-(piperazin-1-ylmethyl)pyridine-2-yl)pyrimidin-2-amine as a highly potent and selective cyclin-dependent kinases 4 and 6 inhibitors and the discovery of structure-activity relationships

Cyclin-dependent kinases 4/6 play an important role in regulation of cell cycle, and overexpress in a variety of cancers. Up to now, new CDK inhibitors still need to be developed due to its poor selectivity. Herein we report a novel series of 4-(2,3-dihydro-1H-benzo[d]pyrrolo[1,2-a]imidazole-7-yl)-N-(5-(piperazin-1-ylmethyl)pyridine-2-yl)pyrimidin-2-amine anologues as potent CDK 4/6 inhibitors based on LY2835219 (Abemaciclib). Compound 10d, which exhibits approximate potency on CDK4/6 (IC₅₀?=?7.4/0.9?nM), has both good pharmacokinetic characters and high selectivity on CDK1 compared with LY2835219. Overall, compound 10d could be a promising candidate and a good starting point as anticancer drugs.     

Cloning and Spatio-Temporal Expression of Porcine CDK5 and CDK5R1(p35) Genes

Cyclin-dependent kinase 5 (CDK5) is a serine/threonine kinase homologue attributed to the mitotic cyclin-dependent kinase family. Both the kinase activity and the biological effects of CDK5 in central nervous system are mainly dependent on association with its regulatory subunit 1 known as CDK5R1 (p35). In the present study, the full-length coding regions of CDK5 and CDK5R1 were cloned from pigs. Radiation hybrid mapping localized porcine CDK5 to chromosome 18q12-13, whereas CDK5R1 was electro-localized to chromosome 12q12. Real-time quantitative RT-PCR (qRT-PCR) showed that CDK5 mRNA is ubiquitously present in all porcine tissues examined, with relatively high levels in cerebral cortex, cerebellum, testicle and lung. We also examined the expression profile of porcine CDK5/CDK5R1 in various tissues at different developmental stages. The results indicated that CDK5 mRNA reaches the highest level in cerebral cortex at two months of age and in cerebellum and liver at 4 months of age, respectively, whereas the peak level of CDK5R1 was observed in both cerebral cortex and cerebellum at two months of age, indicating the pivotal role of CDK5/CDK5R1 during the development of porcine brain.     

Induction of apoptosis in human leukemia cells by the CDK1 inhibitor CGP74514A

We have examined the effects of the CDK1 inhibitor CGP74514A on cell cycle- and apoptosis-related events in human leukemia cells. An 18-hr exposure to 5 microM CGP74514A induced mitochondrial damage (i.e., loss of Delta psi(m)) and apoptosis in multiple human leukemia cell lines (e.g., U937, HL-60, KG-1, CCRF-CEM, Raji, and THP; range 30-95%). In U937 cells, CGP74514A- induced apoptosis (5 microM) became apparent within 4 hr and approached 100% by 24 hr. The pan- caspase inhibitor Boc-fmk and the caspase-8 inhibitor lETD-fmk opposed CGP74514A-induced caspase-9 activation and PARP degradation, but not cytochrome c or Smac/DIABLO release. CGP74514A-mediated apoptosis was substantially blocked by ectopic expression of full-length Bel- 2, a loop-deleted mutant Bcl-2, and Bcl-x(L). CGP74514A treatment (5 microM; 18 hr) resulted in increased p21(CIP1) expression, p27(KIP1) degradation, diminished E2F1 expression, and dephosphorylation of p34(CDC2). It also induced early (i.e., within 2 hr) inhibition of CDK1 activity and dephosphorylation of pRb, followed by pRb degradation, but did not block pRb phosphorylation at CDK2- and CDK4- specific sites. These findings indicate that the selective CDK1 inhibitor, CGP74514A, induces complex changes in cell cycle-related proteins in human leukemia cells accompanied by extensive mitochondrial damage, caspase activation, and apoptosis.