Browsing by Author "Lee, Ki-Young"
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Item Open Access A Novel Collapsing Response Mediator Protein 2 Binding Domain for Kinesin Light Chain 3(2016) Faghfor Maghrebi, Mohammad Amin; van der Hoorn, Franciscus A.; Dobrinski, Ina; Thundathil, Jacob Chacko; Lee, Ki-YoungSignificant similarity exists between primary cilia and sperm flagella. Both contain an axoneme and both require presence of ODF2. Therefore, primary cilia can be used as a partial model to study the assembly of sperm flagella. Recently, we have shown that Collapsin Response Mediator Protein 2 is required for ciliogenesis, localizes to the basal body, and can be transported into the primary cilium, however, the involved mechanism is not clear, but was proposed to involve kinesin proteins. KLC3 is the only known kinesin light chain expressed in elongating spermatids that develop the flagellum. In this study, we investigated the expression of CRMP2 in mouse testis and we studied if CRMP2 and KLC3 interact. We observed CRMP2 mRNA expression in testis, along with expression of the other family members CRMP1, CRMP3 and CRMP4. CRMP2 protein localized in elongating spermatids to the neck region containing the centrioles, structures that also form the basal body. We show interaction of KLC3 and CRMP2 in cell culture and discovered that the interaction requires a sequence of CRMP2 different from that which is known to bind KLC1. We also show that KLC3 expression can change the localization of CRMP2 from one associated with microtubules to one associated with complexes of KLC3 and mitochondria. Our study suggests a role for CRMP2 in the elongating spermatid.Item Open Access A novel role for cdk5 in the cell cycle(2008) Yang, Songhua; Lee, Ki-Young; Syed, Naweed I.Item Open Access A Novel Role of Cdk5 in the Cell Cycle(2014-01-24) Law, Vincent; Lee, Ki-YoungCyclin-dependent kinase 5 (Cdk5) is a small 33 kDa serine/threonine kinase belonging to the cdk family. It was originally identified based on the structural similarity to Cdk1 (Cdc2) and Cdk2, key regulators of eukaryotic cell cycle progression. Unlike other members of the Cdk family however, Cdk5 is not activated by cyclins, but rather by non- cyclin proteins p35 and p39. The majority of reports regarding Cdk5 relate to neuronal development, particularly in the brain, and so whether Cdk5 functions in cell division has remained a mystery. Further studies by various groups revealed additional roles of Cdk5 outside the neuronal context, including functions in cancer progression. Recently, Cdk5 was shown to play a role in modulating the cell cycle. Here in this study, we further explore the potential function of Cdk5 in cell cycle progression, particularly in non- neuronal cells. Using both siRNA and genetic approaches, we found that the absence of Cdk5 enhances cell proliferation. The loss of Cdk5 causes an upregulation of Cyclin D1 expression, while levels of the cyclin-depdent kinase inhibitor proteins p21 and p27 are reduced. Furthermore, based on flow cytometry analysis, cells lacking Cdk5 results in cells moving from G1 to S faster than normal cells, indicating a potential function in the G1/S transition. Ionizing radiation (IR) studies also reveal that the absence of Cdk5 reduces p53 phosphorylation, and maintains the presence of γH2AX foci, indicating a disruption in DNA repair process, which may cause genomic instability. Collectively, these results support the idea that Cdk5 may play an important role in regulating the cell cycle of non-neuronal cells, particularly at the G1/S transition.Item Open Access Integration of a bacterial gene sequence into a chronic eosinophilic leukemia patient’s genome as part of a fusion gene linker(2017-06-05) Sidhoo, Saveen; Rosales, Jesusa L; Lee, Ki-YoungAbstract Analysis of databases from the human genome project (HGP), the 1000 Genomes Project (1KGP), and The Cancer Genome Atlas (TCGA) revealed bacterial DNA integration into the human somatic genome, particularly in tumor tissues. Fusion genes have also been associated with tumorigenesis and 34 PDGFR fusion genes are linked to hematological malignancies. Here, we determined that a 17-bp homologous sequence in Marinobacter sp. Hb8, Rhodococcus fascians D188, Rhodococcus sp. PBTS2, Micrococcus luteus strain trpE16 and M. luteus NCTC 2665 integrates into the genome of a chronic eosinophilic leukemia patient as part of the linker for the novel CDK5RAP2-PDGFRα fusion gene. The resulting fusion protein that has CDK5RAP2’s self-activating domain and PDGFRa’s tyrosine kinase domain but lacks PDGFRa’s membrane-binding and ligand-dependent activation properties may act together with the integrated bacterial sequence to readily phosphorylate downstream targets, amplify proliferation signals and promote leukemic cancer progression.Item Open Access Investigation of the role of Cyclin-dependent Kinase 5 in mediating bortezomib sensitivity in multiple myeloma.(2014-05-26) Levacque, Zachary; Lee, Ki-YoungCyclin-dependent kinase 5 (Cdk5) was previously shown to mediate sensitivity of multiple myeloma cells to the proteasome inhibitor bortezomib. The mechanism by which this occurs was investigated. The idea that Cdk5 could promote the expression of the target of bortezomib PSMB5 via the transcription factor Nrf2 was first examined. However, contrary to published results, I did not find that PSMB5 expression is reduced following Cdk5 knockdown, and Nrf2 activity was also unchanged. Next, a synthetic lethal DNA repair defect from combined Cdk5 knockdown and bortezomib was explored. Both treatments produce an impaired DNA damage response. I show that Cdk5 can affect BRCA1 localization, Further investigation is required to fully characterize the role of Cdk5 in the DNA damage response. Bioinformatics supports the importance of Cdk5 in myeloma as we show that Patients with the highest expression of Cdk5 experience poorer survival following bortezomib treatment. Also, Cdk5 is upregulated in over 50% of all cancers.Item Open Access Regulation and function of cdk5(2011) Tariq, Hassan; Lee, Ki-YoungItem Open Access Regulation of Breast Cancer Cell Proliferation by APRIL(2016) Matook, Wejdan; Lee, Ki-Young; Riabowol, Karl; Brockton, NigelBreast cancer is the most common cause of death from cancer among women. “A proliferation-inducing ligand” (APRIL) is seen in the stroma of approximately 38% of breast cancer patients. APRIL is a tumor necrosis factor superfamily member that is implicated in lymphoid cell survival, proliferation and apoptosis. APRIL studies initially focused on lymphoid cells as known APRIL receptors are exclusive to these cells. However, I found that APRIL promotes breast cancer cell proliferation, and an APRIL-specific blocking peptide inhibits APRIL-induced proliferation. Therefore, I sought to identify APRIL targets in breast cancer cells. Among those identified, colony-stimulating factor 2 receptor beta (CSF2RB) is interesting. CSF2RB-APRIL interaction is direct, and the CSF2RB ligand, CSF2, has 41% amino acid sequence similarity to APRIL. CSF2RB-linked Akt and STAT3 signaling are activated in APRIL-mediated breast cancer cell proliferation. Thus, my findings raise the possibility that CSF2RB is a novel APRIL receptor in non-lymphoid cells.Item Open Access Role of cyclin-dependent kinase 5 (Cdk5) in mitochondrial permeability transition pore (mPTP) opening and intracellular Ca2+ dynamics(2020-06-25) Navaneetha Krishnan, Saranya; Lee, Ki-Young; Riabowol, Karl T.; Lees-Miller, Susan P.; Shutt, Timothy; Braun, Andrew P.; Eitzen, Gary A.Cyclin-dependent kinase 5 (Cdk5), which plays a role in the development and progression of many human cancers, localizes in the mitochondria, a key determinant of apoptotic cell death. Cdk5 is upregulated in breast cancer cells and Cdk5 loss increases cancer cell sensitivity to chemotherapeutic drugs. However, the molecular mechanism by which Cdk5 loss promotes cell death remains unclear. I hypothesized that Cdk5 loss activates the intrinsic apoptotic pathway in breast cancer cells. I demonstrated that Cdk5-deficient breast cancer cells exhibit increased mitochondrial depolarization, mitochondrial reactive oxygen species (mtROS) levels, and mitochondrial fragmentation that is associated with an increase in both intracellular Ca2+ level and calcineurin activity, and dynamin related protein 1 (DRP1) Ser637 dephosphorylation. To define mitochondria-mediated apoptotic pathway, I utilized various inhibitors of mitochondrial function. Apoptosis is completely prevented by mitochondrial permeability transition pore (mPTP) inhibition, almost fully inhibited by blocking ROS and unaffected by inhibition of mitochondrial fission, suggesting that apoptosis in breast cancer cells due to Cdk5 loss occurs via a novel mPTP-dependent mechanism that acts primarily through ROS increase. Since calcium is the major regulator of mPTP opening, I hypothesized that Cdk5 regulates intracellular calcium homeostasis. Using primary mouse embryonic fibroblasts (MEFs) isolated from Cdk5?/? mouse embryos, I showed that loss of Cdk5 increases inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca2+ release from internal stores. Cdk5 associates with and phosphorylates the IP3R1 Ca2+ channel at Ser421 and such phosphorylation controls IP3R1-mediated Ca2+ release as loss of Cdk5, and thus loss of IP3R1 Ser421 phosphorylation, triggers an increase in IP3R1-mediated Ca2+ release in Cdk5?/? MEFs. Analysis of subcellular fractions of MEFs demonstrates that Cdk5 localizes in the mitochondria-associated endoplasmic reticulum membrane (MAM) and Cdk5 loss causes increased ER-mitochondria tethering, a process required for Ca2+ transfer from the ER to the mitochondria. Inhibition of ER Ca2+ release or mitochondrial Ca2+ uptake in Cdk5?/? MEFs prevents mPTP opening, indicating that mPTP opening in Cdk5?/? MEFs is due to increased Ca2+ transfer from the ER to the mitochondria. Altogether, our findings suggest that Cdk5 regulates IP3R1-mediated calcium release and mitochondrial Ca2+ homeostasis that are disturbed upon Cdk5 loss, which lead to mPTP opening.Item Open Access ROS-Mediated Cancer Cell Killing through Dietary Phytochemicals(2019-05-14) NavaneethaKrishnan, Saranya; Rosales, Jesusa L.; Lee, Ki-YoungReactive oxygen species (ROS) promote carcinogenesis by inducing genetic mutations, activating oncogenes, and raising oxidative stress, which all influence cell proliferation, survival, and apoptosis. Cancer cells display redox imbalance due to increased ROS level compared to normal cells. This unique feature in cancer cells may, therefore, be exploited for targeted therapy. Over the past few decades, natural compounds have attracted attention as potential cancer therapies because of their ability to maintain cellular redox homeostasis with minimal toxicity. Preclinical studies show that bioactive dietary polyphenols exert antitumor effects by inducing ROS-mediated cytotoxicity in cancer cells. These bioactive compounds also regulate cell proliferation, survival, and apoptotic and antiapoptotic signalling pathways. In this review, we discuss (i) how ROS is generated and (ii) regulated and (iii) the cell signalling pathways affected by ROS. We also discuss (iv) the various dietary phytochemicals that have been implicated to have cancer therapeutic effects through their ROS-related functions.Item Open Access Thrombin-mediated signaling pathways in neurite extension and retraction(2008) Mufti, Rania; Lee, Ki-Young; Syed, Naweed I.