- Abstract: DNA damage during the cell division cycle can activate ATM/ATR and their downstream kinases that are involved in the checkpoint pathway, and cell growth is halted until damage is repaired. As a result of DNA damage induced in mitotic cells by doxorubicin treatment, cells accumulate in a G2-like phase, not in mitosis. Under these conditions, two mitosis-specific kinases, Cdk1 and Plk1, are inhibited by inhibitory phosphorylation and dephosphorylation, respectively. G2-specific phosphorylation... Show More
- Abstract: Polo-like kinase-1 (Plk1) is phosphorylated on Thr210 for activation during mitosis. Here, we investigated the question of which kinase(s) is the specific upstream kinase of mitotic Plk1. Upstream kinases of Plk1 were purified from mitotic cell extracts through column chromatography procedures, and identified by mass spectrometry. Candidates for Plk1 kinase included p21-activated kinase, aurora A, and mammalian Ste20-like kinases. Immunoprecipitates of these proteins from mitotic cell... Show More
- Abstract: Polo-like kinase-1 (Plk1) is essential for progression of mitosis and localizes to centrosomes, central spindles, midbody, and kinetochore. Ran, a small GTPase of the Ras superfamily, plays a role in microtubule dynamics and chromosome segregation during mitosis. Although Ran-binding protein-1 (RanBP1) has been reported as a regulator of RanGTPase for its mitotic functions, the action mechanism between Ran and RanBP1 during mitosis is still unknown. Here, we demonstrated in vitro and in vivo... Show More
- Abstract: Polo-like kinase-1 (Plk1) belongs to a family of serine-threonine kinases and plays a critical role in mitotic progression. Plk1 involves in initiation of mitosis, centrosome maturation, bipolar spindle formation, and cytokinesis, which are well-reported as traditional functions of Plk1. In this review, we discuss the role of Plk1 during DNA damage response beyond the functions in mitotsis. When DNA damage is occurred in cells under various stress conditions, the checkpoint mechanism is... Show More
- Abstract: Although the primary cell cultures from dental pulp and other oral tissue are frequently used to study osteogenic potential and stem cell responses, few systematic and comparative studies on stemness for the dentinogenic differentiation of these cells have been conducted. In the present study, to investigate the stemness of oral primary cells during extended culture, human adult dental pulp cells (hDPCs), periodontal ligament stem cells (hPDLSCs) and gingival fibroblasts (hGFs) were obtained... Show More
- Abstract: Dental pulp is a soft tissue located inside the hard part of a tooth, and it contains a stem cell population that can regenerate damaged dentin and/or pulp itself. Dental pulp stem cells (hDPSCs) are multipotent adult stem cells that have the potential to be differentiated into a variety of cell types. Although cells cultured primarily from pulp tissue show heterogeneous phenotypes and variable efficiency in their dentinogenic differentiation, proper selection markers, which are specific to... Show More
- Abstract: Human adult dental pulp tissue is a source of adult stem cells that have a potential to differentiate into various tissues, although the primary cell suspensions cultured from pulp tissue are mixture of both stem cell and non-stem cell populations with heterogeneous phenotypes and various differentiation efficiencies. Therefore, cell-surface protein markers on dental pulp stem cells are critical for detection and purification of stem cell populations. Yet, little is known about the... Show More
Publications citing this author (66)
[Show abstract] [Hide abstract] ABSTRACT: Polo-like kinase 1 (Plk1) is a conserved serine/threonine protein kinase that plays pivotal roles during the cell cycle and cell proliferation. Although a number of important targets have been identified, the mechanism of Plk1-regulated pathways and the bulk of the Plk1 interactome are largely unknown. Here, we demonstrate that Plk1 interacts with the DExH/D RNA helicase, UAP56. The protein levels of UAP56 and Plk1 are inversely correlated during the cell cycle. We also show that Plk1 phosphorylates UAP56 in vitro and in vivo and that Plk1-dependent phosphorylation of UAP56 triggers ubiquitination and degradation of UAP56 through proteasomes. This result suggests that Plk1-mediated phosphorylation of UAP56 regulates the stability of UAP56. Our results will be helpful in further understanding mRNA metabolism, cell cycle progression, and the link between mRNA metabolism and cellular function.
- In addition, inhibition of Plk1 activity by various approaches causes growth arrest and apoptosis of transformed cells, suggesting that Plk1 is a potential target for drug development against cancers [13, 14]. Although a number of targets important for Plk1 have been identified151617, the mechanism of Plk1-regulated pathways and the bulk of the Plk1 interactome are largely unknown. In an effort to more comprehensively identify the substrates and interacting proteins of Plk1, we pursued a yeast two-hybrid approach to identify Plk1-interacting proteins from an embryonic stem cell cDNA library.
[Show abstract] [Hide abstract] ABSTRACT: Oral epithelial-mesenchymal interactions play a key role in tooth development and assist differentiation of dental pulp. Many epithelial and mesenchymal factors in the microenvironment influence dental pulp stem cells to differentiate and regenerate. To investigate the interaction between oral cells during differentiation, we designed a microfluidic device system for indirect co-culture. The system has several advantages, such as consumption of low reagent volume, high-throughput treatment of reagents, and faster mineralization analysis. In this study, stem cells from human exfoliated deciduous teeth were treated with media cultured with human gingival fibroblasts or periodontal ligament stem cells. When human exfoliated deciduous teeth was incubated in media cultured in human gingival fibroblasts and human periodontal ligament stem cells under the concentration gradient constructed by the microfluidic system, no remarkable change in human exfoliated deciduous teeth mineralization efficiency was detected. However, osteoblast gene expression levels in human exfoliated deciduous teeth incubated with human gingival fibroblasts media decreased compared to those in human exfoliated deciduous teeth treated with human periodontal ligament stem cells media, suggesting that indirect co-culture of human exfoliated deciduous with human gingival fibroblasts may inhibit osteogenic cytodifferentiation. This microfluidic culture device allows a co-culture system set-up for sequential treatment with co-culture media and differentiation additives and facilitated the mineralization assay in a micro-culture scale.
- Cell suspension was obtained by passing through a 70-µM strainer, and incubated in α-MEM containing 20% fetal bovine serum (Hyclone, GE Healthcare, Buckinghamshire, UK) and antibiotics at 37°C in 5% CO2. For differentiation and mineralization, cells were incubated in α-MEM containing 10% fetal bovine serum, 5 mM β-glycerophosphate, 500 nM dexamethasone, and 100 µM ascorbic acid for 15 days[33,34].
[Show abstract] [Hide abstract] ABSTRACT: Background Preinvasive squamous cell cancer (PSCC) are local transformations of bronchial epithelia that are frequently observed in current or former smokers. Their different grades and sizes suggest a continuum of dysplastic change with increasing severity, which may culminate in invasive squamous cell carcinoma (ISCC). As a consequence of the difficulty in isolating cancerous cells from biopsies, the molecular pathology that underlies their histological variability remains largely unknown. Method To address this issue, we have employed microdissection to isolate normal bronchial epithelia and cancerous cells from low- and high-grade PSCC and ISCC, from paraffin embedded (FFPE) biopsies and determined gene expression using Affymetric Human Exon 1.0 ST arrays. Tests for differential gene expression were performed using the Bioconductor package limma followed by functional analyses of differentially expressed genes in IPA. Results Examination of differential gene expression showed small differences between low- and high-grade PSCC but substantial changes between PSCC and ISCC samples (184 vs 1200 p-value <0.05, fc ±1.75). However, the majority of the differentially expressed PSCC genes (142 genes: 77%) were shared with those in ISCC samples. Pathway analysis showed that these shared genes are associated with DNA damage response, DNA/RNA metabolism and inflammation as major biological themes. Cluster analysis identified 12 distinct patterns of gene expression including progressive up or down-regulation across PSCC and ISCC. Pathway analysis of incrementally up-regulated genes revealed again significant enrichment of terms related to DNA damage response, DNA/RNA metabolism, inflammation, survival and proliferation. Altered expression of selected genes was confirmed using RT-PCR, as well as immunohistochemistry in an independent set of 45 ISCCs. Conclusions Gene expression profiles in PSCC and ISCC differ greatly in terms of numbers of genes with altered transcriptional activity. However, altered gene expression in PSCC affects canonical pathways and cellular and biological processes, such as inflammation and DNA damage response, which are highly consistent with hallmarks of cancer. Electronic supplementary material The online version of this article (doi:10.1186/s12931-016-0496-3) contains supplementary material, which is available to authorized users.
- The pathways identified by IPA for genes gradually up regulated across PSCC and ISCC encompass changes to biological functions that are reminiscent of malignant cells. 'G2/M cell cycle checkpoint regulation' , 'p53 signaling' , 'GADD signaling' or 'Polo-like kinase signaling' can be associated with DNA damage and stress reactions in response to a chronic exposure to tobacco fumes or other volatile carcinogens [25, 27,. The observed activations of 'ERK/MAPK Signaling' (z-score: 2.236) or 'PI3K/AKT Signaling' (z-score: 2.449) are common in many different cancers and may gradually enhance survival and proliferation of preinvasive and invasive cells in the included samples .
[Show abstract] [Hide abstract] ABSTRACT: Over the last two decades, the small GTPase Ran has emerged as a central regulator of both mitosis and meiosis, particularly in the generation, maintenance, and regulation of the microtubule (MT)-based bipolar spindle. Ran-regulated pathways in mitosis bear many similarities to the well-characterized functions of Ran in nuclear transport and, as with transport, the majority of these mitotic effects are mediated through affecting the physical interaction between karyopherins and Spindle Assembly Factors (SAFs)—a loose term describing proteins or protein complexes involved in spindle assembly through promoting nucleation, stabilization, and/or depolymerization of MTs, through anchoring MTs to specific structures such as centrosomes, chromatin or kinetochores, or through sliding MTs along each other to generate the force required to achieve bipolarity. As such, the Ran-mediated pathway represents a crucial functional module within the wider spindle assembly landscape. Research into mitosis using the model organism Drosophila melanogaster has contributed substantially to our understanding of centrosome and spindle function. However, in comparison to mammalian systems, very little is known about the contribution of Ran-mediated pathways in Drosophila mitosis. This article sets out to summarize our understanding of the roles of the Ran pathway components in Drosophila mitosis, focusing on the syncytial blastoderm embryo, arguing that it can provide important insights into the conserved functions on Ran during spindle formation.
- During mitosis, Plk1 phosphorylates Ran, and while the precise functional significance of this is unknown, a Plk1 phospho-mimetic mutation in Ran results in abnormal spindle morphology (Feng et al., 2006). Plk1 also phosphorylates RanBP1 (Hwang et al., 2011), and this phosphorylation is crucial for proper spatial regulation of the Ran.GTP gradient (Zhang et al., 2014). Together, this suggests that Plk1 functions upstream of Ran-dependent mitotic pathways.
[Show abstract] [Hide abstract] ABSTRACT: Despite multimodal therapy with radiation and the DNA alkylating agent temozolomide (TMZ), malignant gliomas remain incurable. Up to 90% of grades II-III gliomas contain a single mutant isocitrate dehydrogenase 1 (IDH1) allele. IDH1 mutant-mediated transformation is associated with TMZ resistance; however, there is no clinically available means of sensitizing IDH1 mutant tumors to TMZ. In this study we sought to identify a targetable mechanism of TMZ resistance in IDH1 mutant tumors to enhance TMZ efficacy. IDH1 mutant astrocytes rapidly bypassed the G2 checkpoint with unrepaired DNA damage following TMZ treatment. Checkpoint adaptation was accompanied by PLK1 activation and IDH1 mutant astrocytes were more sensitive to treatment with BI2536 and TMZ in combination (<20% clonogenic survival) than either TMZ (~60%) or BI2536 (~75%) as single agents. In vivo, TMZ or BI2536 alone had little effect on tumor size. Combination treatment caused marked tumor shrinkage in all mice and complete tumor regression in 5 of 8 mice. Mutant IDH1 promotes checkpoint adaptation which can be exploited therapeutically with the combination of TMZ and a PLK1 inhibitor, indicating PLK1 inhibitors may be clinically valuable in the treatment of IDH1 mutant gliomas.
- PLK1 can inactivate the DNA damage checkpoint by inactivating or facilitating degradation of target proteins such as Claspin, a mediator of CHK1 activation and G2 checkpoint maintenance [34, 35]. CHK1 and PLK1 act antagonistically as PLK1 can be inactivated in a CHK1 activity-dependent manner [31, 32]. Consistent with this model, our data confirm that CHK1 is inactivated and PLK1 is activated in IDH1 mutant cells following TMZ exposure.
Eidō, Chungcheongbuk-do, South Korea
- Department of NanoBioMedical Sciences