Bachelor of Science, Handong Global University (2005)
Doctor of Philosophy, University of Science and Technology (2010)
Zijie Sun, Postdoctoral Faculty Sponsor
ZMIZ2, also named ZIMP7, is a protein inhibitor of activated STAT (PIAS)-like protein and a transcriptional coactivator. In this study, we investigated the interaction between ZMIZ2 and β-catenin, a key regulator of the Wnt signaling pathway. We demonstrated that the expression of exogenous ZMIZ2 augments TCF (T cell factor) and β-catenin-mediated transcription. In contrast, shRNA knockdown of ZMIZ2 expression specifically represses the enhancement of TCF/β-catenin-mediated transcription by ZMIZ2. Using Wnt3a-conditioned medium, we demonstrated that ZMIZ2 can enhance Wnt ligand-induced TCF/β-catenin-mediated transcription. We also showed a promotional role of ZMIZ2 in enhancing β-catenin downstream target gene expression in human cells and in Zmiz2 null (Zmiz2(-/-)) mouse embryonic fibroblasts (MEFs). The regulatory role of Zmiz2 in Wnt-induced TCF/β-catenin-mediated transcription can be restored in Zmiz2(-/-) MEFs that were infected with adenoviral expression vectors for Zmiz2. Moreover, enhancement of Zmiz2 on TCF/β-catenin-mediated transcription was further demonstrated in Zmiz2 knockout and Axin2 reporter compound mice. Furthermore, the protein-protein interaction between ZMIZ2 and β-catenin was identified by co-immunoprecipitation and in vitro protein pulldown assays. We also observed recruitment of endogenous ZMIZ2 onto the promoter region of the Axin 2 gene, a β-catenin downstream target promoter, in a Wnt ligand-inducible manner. Finally, a promotional role of ZMIZ2 on cell growth was demonstrated in human cell lines and Zmiz2 knockout MEFs. Our findings demonstrate a novel interaction between ZMIZ2 and β-catenin and elucidate a novel mechanism for PIAS-like proteins in regulating Wnt signaling pathways.
View details for DOI 10.1074/jbc.M113.529727
View details for PubMedID 24174533
Using an Lzts2 knock-out mouse model, we characterized the biological role of Lzts2 in tumorigenesis. Both heterozygous and homozygous deletion of the Lzts2-targeted allele in mice shows an increased incidence in spontaneous tumor development, although Lzts2 homozygous knock-out mice show significantly higher incidences than heterozygous mice. Treatment of Lzts2-deficient mice with a carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine, increases the susceptibility to N-butyl-N-(4-hydroxybutyl) nitrosamine-induced bladder carcinoma development. Examination of human prostate cancer tissue specimens shows a reduction of LZTS2 protein expression in prostate cancer cells. Further analyses of mouse embryonic fibroblasts isolated from Lzts2 knock-out embryos show that loss of Lzts2 enhances cell growth. These data provide the first line of evidence demonstrating that deletion of Lzts2 increases susceptibility to spontaneous and carcinogen-induced tumor development.
View details for DOI 10.1074/jbc.M112.417568
View details for Web of Science ID 000314845000005
View details for PubMedID 23275340
The PTEN tumor suppressor gene is frequently inactivated in human prostate cancer. Using Osr1 (odd skipped related 1)-Cre mice, we generated a novel conditional Pten knockout mouse strain, Pten(LoxP):Osr1-Cre. Conditional biallelic and monoallelic Pten knockout mice were viable. Deletion of Pten expression was detected in the prostate of Pten(LoxP/LoxP):Osr1-Cre mice as early as 2 weeks of age. Intriguingly, Pten(LoxP/LoxP):Osr1-Cre mice develop high-grade prostatic intraepithelial neoplasms (PINs) with high penetrance as early as one-month of age, and locally invasive prostatic tumors after 12-months of age. Pten(LoxP/+):Osr1-Cre mice show only mild oncogenic changes after 8-weeks of age. Castration of Pten(LoxP/LoxP):Osr1-Cre mice shows no significant regression of prostate tumors, although a shift of androgen receptor (AR) staining from the nuclei to cytoplasm is observed in Pten null tumor cells of castrated mice. Enhanced Akt activity is observed in Pten null tumor cells of castrated Pten(LoxP/LoxP):Osr1-Cre. This study provides a novel mouse model that can be used to investigate a primary role of Pten in initiating oncogenic transformation in the prostate and to examine other genetic and epigenetic changes that are required for tumor progression in the mouse prostate.
View details for DOI 10.1371/journal.pone.0053476
View details for Web of Science ID 000313429800053
View details for PubMedID 23308230
Vitamin-D3 upregulated protein-1 (VDUP1) is a stress response protein. Pseudomonas aeruginosa (P. aeruginosa) infection is a leading cause of death. Mice infected with live P. aeruginosa exhibit significantly decreased VDUP1 expression. However, the function of VDUP1 during P. aeruginosa-induced mouse bacteremic shock is unknown. To address the function of VDUP1 in P. aeruginosa-infected mice, we constructed a bacteremic shock model wherein both wild-type and VDUP1-deficient mice were infected intra-peritoneally with live P. aeruginosa. We found that VDUP1-deficient mice were more resistant to P. aeruginosa-induced bacteremic shock than wild-type mice, as shown by the increased survival, accelerated bacterial clearance and suppression of cytokine overproduction of the VDUP1-deficient mice. VDUP1 promoted the recruitment of neutrophils into the peritoneal cavities of infected mice. VDUP1 impeded the phagocytosis of non-opsonized P. aeruginosa via phosphatidylinositide 3-kinase (PI3K) pathway in macrophages. P. aeruginosa infection induced the generation of reactive oxygen species (ROS), and the increased production of ROS by the peritoneal cells of VDUP1-deficient mice was advantageous in clearing the bacteria. Overall, VDUP1 aggravates bacteremic shock; thus, VDUP1 can be considered a target molecule for the inhibition of P. aeruginosa-induced bacteremic shock.
View details for DOI 10.1016/j.cellimm.2012.11.003
View details for Web of Science ID 000315133100001
View details for PubMedID 23246829
The IL-22 NKp46(+) innate lymphoid cells, NCR22 cells, are very important for the early host defense against microbial pathogens. We show here that NCR22 cells were differentiated from Lin(-)CD127(+)CD117(+) cells that were derived from hematopoietic precursor cells (HPCs) of mouse bone marrow cells. The combination of low concentrations of IL-23 and IL-15 induced differentiation of NCR22 cells from Lin(-)CD127(+)CD117(+) cells. NCR22 cells expressed a large amount of IL-22 and ROR?t, and they had poor cytolytic activity and produced little IFN-?. Lin(-)CD127(+)CD117(+) cells were very similar to intestinal lamina propria LTi-like cells; both cells dominantly expressed ROR?t and IL-22. Meanwhile, Lin(-)CD127(-)CD117(+) cells that were also derived from HPCs did not express ROR?t and IL-22, and they developed into conventional NK cells, not into NCR22 cells. These findings revealed that NCR22 cells can be differentiated from Lin(-)CD127(+)CD117(+) cells which are derived from HPCs.
View details for DOI 10.1016/j.imlet.2011.07.007
View details for Web of Science ID 000297871700008
View details for PubMedID 21835206
Perforin (Prf1) and granzyme B (GzmB) are essential effector molecules for natural killer (NK)-cell cytotoxicity, but how Prf1 and GzmB expression is regulated during arming of NK cells is poorly defined. We show that human microRNA (miR)-27a* is a negative regulator of NK-cell cytotoxicity by silencing Prf1 and GzmB expression. Human miR-27a* specifically bound to the 3' untranslated regions of Prf1 and GzmB, down-regulating expression in both resting and activated NK cells, and it functioned as a fine-tuner for homeostasis of the net amount of the effector proteins. Consistent with miR-27a* having an inhibitory role, knockdown of miR-27a* in NK cells dramatically increased cytotoxicity in vitro and decreased tumor growth in a human tumor xenograft model. Thus, NK-cell cytotoxicity is regulated, in part, by microRNA, and modulating endogenous miR-27a* levels in NK cells represents a potential immunotherapeutic strategy.
View details for DOI 10.1182/blood-2011-04-347526
View details for Web of Science ID 000297265400018
View details for PubMedID 21960590
Interleukin 10 (IL-10) is a multifunctional cytokine that regulates diverse functions of immune cells. Natural killer (NK) cells express the IL-10 and IL-10 receptor, but little is known about the function of IL-10 on NK cell activation. In this study, we show the expression and role of IL-10 in human NK cells. Among the cytokines tested, IL-15 was the most potent inducer of IL-10, with a maximal peak expression at 5 h after treatment. Furthermore, IL-10 receptor was shown to be expressed in NK cells. IL-10 alone had a significant effect on NK cytotoxicity which additively increased NK cell cytotoxicity in the presence of IL-15. Neutralizing IL-10 with anti-IL-10 antibody suppressed the inductive effect of IL-10 on NK cell cytotoxicity; however, IL-10 had no effect on IFN-? or TNF-? production or NK cell activatory receptor expression. STAT signals are implicated as a key mediator of IL-10/IL-15 cytotoxicity response. Thus, the effect of IL-10 on NK cells is particularly interesting with regard to the STAT3 signal that was enhanced by IL-10 or IL-15.
View details for DOI 10.1007/s10059-011-1057-8
View details for Web of Science ID 000297627300008
View details for PubMedID 21809216
Natural killer (NK) cells are differentiated from hematopoietic stem cells (HSCs) which are located at the lowest end of an oxygen gradient within the bone marrow (BM). In this report, we investigated whether oxygen tension could affect NK cell differentiation from hematopoietic cells in vitro. We found that hypoxia led to an inhibition of differentiation in NK cells, and increased oxygen supply alleviated this inhibition and restored NK cell differentiation under hypoxic condition. Hypoxia-treated cells demonstrated reduced mRNA expression of transcription factors (TFs) that have important roles in NK cell differentiation, such as EOMES, T-bet, GATA-3 and ETS-1. Moreover, hypoxia-pretreated cells recovered mRNA expression of TFs when the oxygen tension was changed to normoxia. Our findings suggest that oxygen tension modulates in vitro differentiation of NK cells through the regulation of TF expression.
View details for DOI 10.1016/j.imlet.2011.02.020
View details for Web of Science ID 000290189800009
View details for PubMedID 21354208
Natural killer (NK) cells act important roles in innate immunity and adaptive immunity. However, the mechanisms governing NK cell development have not been clearly elucidated. Previous studies have shown that an HMG (high-mobility group) protein, TOX, is important for regulating the differentiation program of developing T cells in mice. In this study, we examined the role of TOX in differentiation of human NK cells. Knockdown of TOX in differentiating cells decreased the NK cell population identified by expression of NK surface markers and receptors. In addition, over-expression of TOX enhanced the differentiation of NK cells which give rise to a population showing effector functions of mature NK cells. Moreover, TOX influenced expression of T-bet (T-box expressed in T cells, also as known as Tbx21) during NK cell development. Overall, these results suggest that TOX is required for IL-15-mediated NK cell differentiation and affected expression of T-bet that plays critical roles in NK differentiation and maturation.
View details for DOI 10.1016/j.imlet.2010.11.008
View details for Web of Science ID 000289134400004
View details for PubMedID 21126536
NK cells are capable of killing virus-infected or tumor cells and producing IFN-gamma. Resting NK cells, however, have only minimal cytolytic activity and secrete a low level of IFN-gamma. The cytokine IL-15 can promote the expression of effector functions by resting NK cells. In this study, we demonstrate that suppressor of cytokine signaling 2 (SOCS2) has a novel role in IL-15-primed human NK cell function. SOCS2 expression was upregulated in NK cells following stimulation with IL-15. During IL-15-mediated NK cell priming, SOCS2 interacted with phosphorylated proline-rich tyrosine kinase 2 (Pyk2) at tyrosine 402 (p-Pyk2(Tyr402)) and induced the proteasome-mediated degradation of p-Pyk2(Tyr402) via ubiquitination. Knockdown of SOCS2 resulted in the accumulation of p-Pyk2(Tyr402) and blocked NK cell effector functions. In addition, NK cell cytolytic activity and IFN-gamma production were inhibited by overexpression of the wild-type of Pyk2 but not by the overexpression of tyrosine 402 mutant of Pyk2. These results suggest that SOCS2 regulates human NK cell effector functions via control of phosphorylated Pyk2 depending on IL-15 existence.
View details for DOI 10.4049/jimmunol.1000784
View details for Web of Science ID 000279675200019
View details for PubMedID 20543098
The detailed mechanism driving the germinal center (GC) reaction to B cell lymphomagenesis has not been clarified. Thioredoxin interacting protein (TXNIP), also known as vitamin D3 up-regulated protein 1 which is an important tumor repressor, is involved in stress responses, redox regulation, and cellular proliferation. Here, we report that TXNIP has a potential role in the formation of GC in peripheral lymphoid organs where B lymphocytes divide rapidly. First, we compared changes in GC from wild type mice and Txnip(-/-) mice. After immunization, Txnip(-/-) mice exhibited higher expression level of BCL-6 and larger percentage of GC B cells with the reduction in antibody production and plasma cell numbers. In addition, Txnip(-/-) spleens had a much larger population which expressed Ki-67, a marker of cell proliferation, in the red pulp border than WT spleens. Furthermore, the expression of BCL-6 was decreased in TXNIP overexpressing cells and elevated in TXNIP deficient cells. Taken together, we conclude that TXNIP may contribute to the formation of GCs after immunization. During this process, TXNIP suppresses BCL-6 expression.
View details for DOI 10.1016/j.imlet.2010.02.002
View details for Web of Science ID 000277061900004
View details for PubMedID 20156484
NK cells play crucial roles in innate immunity and adaptive immunity. The detailed mechanisms, however, governing NK cell development remains unclear. In this study, we report that YC-1 significantly enhances NK cell populations differentiated from human umbilical cord blood hematopoietic stem cells (HSCs). NK cells increased by YC-1 display both phenotypic and functional features of fully mature NK (mNK) cells, but YC-1 does not affect the activation of mNK cells. YC-1 did not affect cGMP production and phosphorylation of STAT-5 which is essential for IL-15R signaling. On the other hand, YC-1 increased p38 MAPK phosphorylation during NK cell differentiation. Furthermore, p38 inhibitor SB203580 inhibited the differentiation of NK cells enhanced by YC-1. Taken together, these data suggest that YC-1 enhances NK cell differentiation through the activation of p38 MAPK which is involved in NK cell differentiation.
View details for DOI 10.1016/j.intimp.2010.01.009
View details for Web of Science ID 000277062500015
View details for PubMedID 20116458
Cross-linking of NK activating receptors activates phospholipase-gamma and subsequently induces diacylglycerol and Ca(2+) as second messengers of signal transduction. Previous studies reported that Ras guanyl nucleotide-releasing protein (RasGRP) 1, which is activated by diacylglycerol and Ca(2+), is crucial for TCR-mediated Ras-ERK activation. We now report that RasGRP1, which can also be detected in human NK cells, plays an essential role in NK cell effector functions. To examine the role of RasGRP1 in NK cell functions, the expression of RasGRP1 was suppressed using RNA interference. Knockdown of RasGRP1 significantly blocked ITAM-dependent cytokine production as well as NK cytotoxicity. Biochemically, RasGRP1-knockdown NK cells showed markedly decreased ability to activate Ras, ERK, and JNK. Activation of the Ras-MAPK pathway was independently shown to be indispensable for NK cell effector functions via the use of specific pharmacological inhibitors. Our results reveal that RasGRP1 is required for the activation of the Ras-MAPK pathway leading to NK cell effector functions. Moreover, our data suggest that RasGRP1 might act as an important bridge between phospholipase-gamma activation and NK cell effector functions via the Ras-MAPK pathway.
View details for DOI 10.4049/jimmunol.0902012
View details for Web of Science ID 000272861300037
View details for PubMedID 19933860
The differentiation of natural killer (NK) cells is regulated by various factors including soluble growth factors and transcription factors. Here, we have demonstrated that tumor necrosis factor-alpha (TNF-alpha) is a positive regulator of NK cell differentiation. TNF-alpha augmented the IL-15-induced expression of NK1.1 and CD122 in mature NK cells, and TNF-alpha alone also induced NK cell maturation as well as IL-15. TNF-alpha also increased IFN-gamma production in NK cells in the presence of IL-15. Meanwhile, mRNA expression of several transcription factors, including T-bet and GATA-3, was increased by the addition of TNF-alpha and IL-15. In addition, TNF-alpha increased nuclear factor-kappa B (NF-kappaB) activity in NK cells and inhibition of NF-kappaB impeded TNF-alpha-enhanced NK cell maturation. Overall, these data suggest that TNF-alpha significantly increased IL-15-driven NK cell differentiation by increasing the expression of transcription factors that play crucial roles in NK cell maturation and inducing the NF-kappaB activity.
View details for DOI 10.1016/j.bbrc.2009.06.120
View details for Web of Science ID 000268462100033
View details for PubMedID 19559672
Hematopoietic stem cells (HSCs) are maintained in a quiescent state in bone marrow (BM) niches by intrinsic and extrinsic signals. The mechanisms regulating the quiescence and mobilization of HSCs, however, remain unclear. In this study, we report that the expression of thioredoxin-interacting protein (TXNIP) is decreased during HSC activation. In Txnip(-/-) mice, the long-term reconstituting HSC population is decreased and exhausted, and its capacity to repopulate is rapidly lost. These effects are associated with hyperactive Wnt signaling, an active cell cycle, and reduced p21 expression under conditions of stress. TXNIP deficiency reduced the CXCL12- and osteopontin-mediated interaction between HSCs and the bone marrow, and impaired homing and retention in the osteoblastic niche, resulting in mobilized HSCs. Therefore, we propose that TXNIP is essential for maintaining HSC quiescence and the interaction between HSCs and the BM niche.
View details for DOI 10.4049/jimmunol.0804221
View details for Web of Science ID 000268906500036
View details for PubMedID 19625652
Pseudomonas aeruginosa (PA) is an opportunistic pathogen that causes the relapse of illness in immunocompromised patients, leading to prolonged hospitalization, increased medical expense, and death. In this report, we show that PA invades natural killer (NK) cells and induces phagocytosis-induced cell death (PICD) of lymphocytes. In vivo tumor metastasis was augmented by PA infection, with a significant reduction in NK cell number. Adoptive transfer of NK cells mitigated PA-induced metastasis. Internalization of PA into NK cells was observed by transmission electron microscopy. In addition, PA invaded NK cells via phosphoinositide 3-kinase (PI3K) activation, and the phagocytic event led to caspase 9-dependent apoptosis of NK cells. PA-mediated NK cell apoptosis was dependent on activation of mitogen-activated protein (MAP) kinase and the generation of reactive oxygen species (ROS). These data suggest that the phagocytosis of PA by NK cells is a critical event that affects the relapse of diseases in immunocompromised patients, such as those with cancer, and provides important insights into the interactions between PA and NK cells.
View details for DOI 10.1371/journal.ppat.1000561
View details for Web of Science ID 000270804500004
View details for PubMedID 19714221