👤 Yoon-Ju Kwon

Chronic ethanol consumption causes hepatic steatosis and inflammation, which are associated with liver hypoxia. Monocyte chemoattractant protein-1 (MCP-1) is a hypoxia response factor that determines recruitment and activation of monocytes to the site of tissue injury. The level of MCP-1 is elevated in the serum and liver of patients with alcoholic liver disease (ALD); however, the molecular details regarding the regulation of MCP-1 expression are not yet understood completely. Here, we show the role of liver X receptor α (LXRα) in the regulation of MCP-1 expression during the development of ethanol-induced fatty liver injury, using an antagonist, 22-S-hydroxycholesterol (22-S-HC). First, administration of 22-S-HC attenuated the signs of liver injury with decreased levels of MCP-1 and its receptor CCR2 in ethanol-fed mice. Second, hypoxic conditions or treatment with the LXRα agonist GW3965 significantly induced the expression of MCP-1, which was completely blocked by treatment with 22-S-HC or infection by shLXRα lentivirus in the primary hepatocytes. Third, over-expression of LXRα or GW3965 treatment increased MCP-1 promoter activity by increasing the binding of hypoxia-inducible factor-1α to the hypoxia response elements, together with LXRα. Finally, treatment with recombinant MCP-1 increased the level of expression of LXRα and LXRα-dependent lipid droplet accumulation in both hepatocytes and Kupffer cells. These data show that LXRα and its ligand-induced up-regulation of MCP-1 and MCP-1-induced LXRα-dependent lipogenesis play a key role in the autocrine and paracrine activation of MCP-1 in the pathogenesis of alcoholic fatty liver disease, and that this activation may provide a promising new target for ALD therapy. Show less

Heterochromatin protein 1 (HP1) is an epigenetic modifier of gene regulation and chromatin packing via binding to trimethylated histone H3 lysine 9 (H3K9). HP1 plays an important role in gene activation as well as gene repression in heterochromatin and euchromatin. However, the role of individual HP1 proteins in human diseases remains elusive. Here, we show that HP1β negatively regulates the expression and activation of matrix metallopeptidase (MMP)2, which mediates cancer metastasis by destructing type Ⅳ collagen. Reduced HP1β expression correlates with the increased level of pro- and active-MMP2 in colon cancer cells. Consistently, HP1β knockdown (KD) increased and HP1β overexpression decreased the mRNA level of MMP2 and membrane type 1 metallopeptidase (MT1-MMP). Furthermore, cancer cells overexpressing HP1β showed impaired migratory ability, whereas HP1β‑deleted cancer cells had increased migration. HP1β negatively regulates MMP2 expression in a transcriptional level and prevents MMP2 activation through reducing the expression of MT1‑MMP. These findings shed new light on HP1β as a molecular regulator and an efficient therapeutic target of metastatic cancer. Show less

How cells communicate during development and regeneration is a critical question. One mechanism of intercellular communication is via exosomes, extracellular vesicles that originate by the fusion of multivesicular endosomes with the plasma membrane [1-8]. To model exosome-based intercellular communication, we used Madin-Darby canine kidney (MDCK) cell cysts grown in 3D gels of extracellular matrix, which form tubules in response to hepatocyte growth factor (HGF). We report that GPRC5B, an orphan G protein coupled receptor, is in exosomes produced by HGF-treated cysts and released into the cyst lumen. Exosomal GPRC5B is taken up by nearby cells and together with HGF promotes extracellular signal-regulated kinase 1/2 (ERK1/2) activation and tubulogenesis, even under conditions where tubulogenesis would otherwise not occur. Recovery from injury, such as acute kidney injury (AKI), often recapitulates developmental processes. Here, we show that GPRC5B is elevated in urinary exosomes from patients with AKI. Our results elucidate how GPRC5B is carried by exosomes and augments HGF-induced morphogenesis. The unexpected role of exosomes in transporting GPRC5B between cells during morphogenesis and the ability of GPRC5B to predict the disease state of AKI elucidate a novel mechanism for intercellular communication during development and repair. Show less

Carcinoids are slow-growing neuroendocrine tumors (NETs) that are characterized by hormone overproduction; surgery is currently the only option for treatment. Activation of the Notch pathway has previously been shown to have a role in tumor suppression in NETs. The marine-derived thiodepsipeptide thiocoraline was investigated in vitro in two carcinoid cell lines (BON and H727). Carcinoid cells treated with nanomolar concentrations of thiocoraline resulted in a decrease in cell proliferation and an alteration of malignant phenotype evidenced by decrease of NET markers, achaete-scute complex like-1, chromogranin A and neurospecific enolase. Western blotting analysis demonstrated the activation of Notch1 on the protein level in BON cells. Additionally, thiocoraline activated downstream Notch targets HES1, HES5 and HEY2. Thiocoraline effectively suppressed carcinoid cell growth by promoting cell cycle arrest in BON and H727 cells. An in vivo study demonstrated that thiocoraline, formulated with polymeric micelles, slowed carcinoid tumor progression. Thus the therapeutic potential of thiocoraline, which induced activation of the Notch pathway, in carcinoid tumors was demonstrated. Show less

Myocilin is a secreted glycoprotein that belongs to a family of olfactomedin domain-containing proteins. Although myocilin is detected in several ocular and nonocular tissues, the only reported human pathology related to mutations in the MYOCILIN gene is primary open-angle glaucoma. Functions of myocilin are poorly understood. Here we demonstrate that myocilin is a mediator of oligodendrocyte differentiation and is involved in the myelination of the optic nerve in mice. Myocilin is expressed and secreted by optic nerve astrocytes. Differentiation of optic nerve oligodendrocytes is delayed in Myocilin-null mice. Optic nerves of Myocilin-null mice contain reduced levels of several myelin-associated proteins including myelin basic protein, myelin proteolipid protein, and 2'3'-cyclic nucleotide 3'-phosphodiesterase compared with those of wild-type littermates. This leads to reduced myelin sheath thickness of optic nerve axons in Myocilin-null mice compared with wild-type littermates, and this difference is more pronounced at early postnatal stages compared with adult mice. Myocilin also affects differentiation of oligodendrocyte precursors in vitro. Its addition to primary cultures of differentiating oligodendrocyte precursors increases levels of tested markers of oligodendrocyte differentiation and stimulates elongation of oligodendrocyte processes. Myocilin stimulation of oligodendrocyte differentiation occurs through the NgR1/Lingo-1 receptor complex. Myocilin physically interacts with Lingo-1 and may be considered as a Lingo-1 ligand. Myocilin-induced elongation of oligodendrocyte processes may be mediated by activation of FYN and suppression of RhoA GTPase. Show less

Juvenile neuronal ceroid lipofuscinosis (JNCL; CLN3 disease; Batten disease) is an autosomal recessive neurodegenerative disease of childhood. Symptoms typically present at school age with vision loss followed by progressive cognitive decline, motor dysfunction, seizures, and behavior problems. Studies on sex differences in JNCL have yielded mixed results, but parent anecdotes suggest that females experience a more precipitous disease course. Therefore, we sought to determine if sex-based differences exist in JNCL. We used data from the Unified Batten Disease Rating Scale (UBDRS), the Batten Disease Support and Research Association (BDSRA) database, and the PedsQL quality of life (QoL) survey to evaluate sex-based differences in functional independence and time from symptom onset to death. On average, females had JNCL symptom onset one year later and death one year earlier than did males. Despite a later age at onset, females had lower functional capability, earlier loss of independent function, and lower physical QoL. Future research in sex differences in JNCL may help to further understand the biological mechanisms underpinning the disease course and may point to targeted therapies. Show less

To use the Unified Batten Disease Rating Scale (UBDRS) to measure the rate of decline in physical and functional capability domains in patients with juvenile neuronal ceroid lipofuscinosis (JNCL) or Batten disease, a neurodegenerative lysosomal storage disorder. We have evaluated the UBDRS in subjects with JNCL since 2002; during that time, the scale has been refined to improve reliability and validity. Now that therapies are being proposed to prevent, slow, or reverse the course of JNCL, the UBDRS will play an important role in quantitatively assessing clinical outcomes in research trials. We administered the UBDRS to 82 subjects with JNCL genetically confirmed by CLN3 mutational analysis. Forty-four subjects were seen for more than one annual visit. From these data, the rate of physical impairment over time was quantified using multivariate linear regression and repeated-measures analysis. The UBDRS Physical Impairment subscale shows worsening over time that proceeds at a quantifiable linear rate in the years following initial onset of clinical symptoms. This deterioration correlates with functional capability and is not influenced by CLN3 genotype. The UBDRS is a reliable and valid instrument that measures clinical progression in JNCL. Our data support the use of the UBDRS to quantify the rate of progression of physical impairment in subjects with JNCL in clinical trials. Show less

Batten disease (BD) is the most common form of a group of disorders called neuronal ceroid lipofuscinosis, which are caused by a CLN3 gene mutation. A variety of pathogenic lysosomal storage disorder mechanisms have been suggested such as oxidative stress, endoplasmic reticulum (ER) stress, and altered protein trafficking. Resveratrol, a stilbenoid found in red grape skin, is a potent antioxidant chemical. Recent studies have suggested that resveratrol may have a curative effect in many neurodegenerative diseases. Therefore, we investigated the activities of resveratrol at the levels of oxidative and ER stress and apoptosis factors using normal and BD lymphoblast cells. We report that the BD lymphoblast cells contained low-levels of superoxide dismutase-1 (SOD-1) due to the long-term stress of reactive oxygen species. However, when we treated the cells with resveratrol, SOD-1 increased to levels observed in normal cells. Furthermore, we investigated the expression of glucose-regulated protein 78 as an ER stress marker. BD cells underwent ER stress, but resveratrol treatment resolved the ER stress in a dose-dependent manner. We further demonstrated that the levels of apoptosis markers such as apoptosis induce factor, cytochrome c, and cleavage of poly (ADP)-ribose polymerase decreased following resveratrol treatment. Thus, we propose that resveratrol may have beneficial effects in patients with BD. Show less

Juvenile neuronal ceroid lipofuscinosis (JNCL; CLN3 disease; Batten disease) is an autosomal recessive neurodegenerative disease of childhood that typically presents at school age with vision loss followed by progressive cognitive decline, motor dysfunction, seizures, and behavior problems. No therapy has been shown to slow the progression of disease in JNCL patients, and all current treatments are symptomatic. Flupirtine has been shown in vitro to reduce apoptosis in CLN3 lymphocytes. Based on that preclinical study, several children with JNCL were given flupirtine by their parents. The purpose of this study was to determine if there was evidence of attenuated disease progression in any JNCL symptom domain. We administered a survey to parents of JNCL children to qualitatively assess flupirtine efficacy. We used the Unified Batten Disease Rating Scale (UBDRS) to determine specific aspects of disease progression and investigated three age-related factors: loss of independent ambulation, loss of intelligible speech, and loss of ability to perform independent activities of daily living. The median scores for the UBDRS physical, behavior, and capability subscales were determined in flupirtine-exposed subjects and compared to age-, sex-, and genotype-matched subjects who had never taken flupirtine. Twenty-one percent of survey responders reported administering flupirtine to their JNCL child, and 56% of these families perceived beneficial changes that they attributed to flupirtine. However, our quantitative, prospectively obtained data did not show any change in JNCL disease progression that could be attributed to flupirtine. This study highlights the need for prospective experimental therapeutic research. Show less

The carbohydrate response element binding protein (ChREBP), a basic helix-loop-helix/leucine zipper transcription factor, plays a critical role in the control of lipogenesis in the liver. To identify the direct targets of ChREBP on a genome-wide scale and provide more insight into the mechanism by which ChREBP regulates glucose-responsive gene expression, we performed chromatin immunoprecipitation-sequencing and gene expression analysis. We identified 1153 ChREBP binding sites and 783 target genes using the chromatin from HepG2, a human hepatocellular carcinoma cell line. A motif search revealed a refined consensus sequence (CABGTG-nnCnG-nGnSTG) to better represent critical elements of a functional ChREBP binding sequence. Gene ontology analysis shows that ChREBP target genes are particularly associated with lipid, fatty acid and steroid metabolism. In addition, other functional gene clusters related to transport, development and cell motility are significantly enriched. Gene set enrichment analysis reveals that ChREBP target genes are highly correlated with genes regulated by high glucose, providing a functional relevance to the genome-wide binding study. Furthermore, we have demonstrated that ChREBP may function as a transcriptional repressor as well as an activator. Show less

The primary aim of this investigation was to examine genotype and clinical phenotype differences in individuals with juvenile neuronal ceroid lipofuscinosis (JNCL) who were homozygous for a common disease-causing deletion or compound heterozygous. The secondary aim was to cross-validate the Child Behavior Checklist (CBCL) and the Unified Batten Disease Rating Scale (UBDRS), a disease-specific JNCL rating scale. Sixty individuals (28 males, 32 females; mean age 15y 1mo, SD 4y 9mo, range 5y 8mo--31y 1mo) with JNCL completed the UBDRS. No significant genotype and clinical phenotype differences were identified when comparing individuals homozygous for the deletion with a heterogeneous group of compound heterozygous individuals. There were significant correlations among related behaviour items and scales on the CBCL and UBDRS (Spearman's rho ranging from 0.39 [p<0.05] to 0.72 [p<0.01]). Behaviour and physical function ratings were uncorrelated, supporting divergent validity of these two constructs in JNCL. Previous reports of genotype and clinical phenotype differences were unsupported in this investigation, which did not find differences between individuals homozygous or heterozygous for the CLN3 deletion. The CBCL, an already validated measure of behaviour problems, appears valid for use in JNCL and cross-validates well with the UBDRS. Show less

The gene expression profiles of lysophosphatidic acid (LPA)-treated young and senescent human diploid fibroblasts (HDFs) were examined using cDNA microarray analysis. The expression of some genes, including EGR 1/3 and MRRF, was controlled by LPA similarly in young and senescent cells, showing a typical time-dependent up-and-down expression profile. In contrast, some other genes, including DUSP6, CYR61, and F3, showed sustained upregulation in senescent HDFs later after LPA treatment. These genes might be involved in altered LPA responsiveness during the aging process. Show less

Juvenile Neuronal Ceroid Lipofuscinosis (JNCL), or Batten disease, is a childhood neurodegenerative disease that is characterized clinically by progressive visual loss, seizures, dementia, and motor incoordination. Children affected with this disease tend to develop normally for the first 5 years of life. However, once disease onset occurs, they decline rapidly and die in their late 20s to early 30s. Though this represents the typical disease course, the onset and severity of disease symptoms can vary. This variability is presumed to be the result of both differences in the causative genetic mutation in the CLN3 gene as well as environmental influences. Most cases of JNCL are caused by a 1 kb deletion in the CLN3 gene, resulting in a frameshift mutation predicted to leave the first 153 amino acids of the CLN3 protein intact, followed by the addition of 28 novel amino acids. Here we report the discovery of a novel mutation identified as a G to T transversion at nucleotide 49 (G49T) in exon 2 of CLN3, introducing a premature stop codon (E17X) near the N-terminus. This mutation represents the most 5' mutation described to date. The patient examined in this study was heterozygous for the common 1 kb deletion and E17X. She had classical disease progression, suggesting that this mutation in CLN3 mimics the more prevalent 1 kb deletion and that progression of JNCL is predominantly the result of loss of CLN3 function. Show less

The Delta-Notch signaling pathway is an evolutionarily conserved intercellular signaling mechanism essential for cell fate specification. Mind bomb 1 (Mib1) has been identified as a ubiquitin ligase that promotes the endocytosis of Delta. We now report that mice lacking Mib1 die prior to embryonic day 11.5, with pan-Notch defects in somitogenesis, neurogenesis, vasculogenesis and cardiogenesis. The Mib1-/- embryos exhibit reduced expression of Notch target genes Hes5, Hey1, Hey2 and Heyl, with the loss of N1icd generation. Interestingly, in the Mib1-/- mutants, Dll1 accumulated in the plasma membrane, while it was localized in the cytoplasm near the nucleus in the wild types, indicating that Mib1 is essential for the endocytosis of Notch ligand. In accordance with the pan-Notch defects in Mib1-/- embryos, Mib1 interacts with and regulates all of the Notch ligands, jagged 1 and jagged 2, as well as Dll1, Dll3 and Dll4. Our results show that Mib1 is an essential regulator, but not a potentiator, for generating functional Notch ligands to activate Notch signaling. Show less

A partial C-terminal cDNA sequence of a novel Drosophila mitogen-activated protein kinase phosphatase (MKP), designated DMKP-3, was identified from an epitope expressed sequence tag database, and the missing N-terminal cDNA fragment was cloned from a Drosophila cDNA library. DMKP-3 is a protein of 411 amino acids, with a calculated molecular mass of 45.8 kDa; the deduced amino acid sequence is most similar to that of mammalian MKP-3. Recombinant DMKP-3 produced in Escherichia coli retained intrinsic tyrosine phosphatase activity. In addition, DMKP-3 specifically inhibited extracellular-signal-regulated kinase (ERK) activity, but was without a significant affect on c-Jun N-terminal kinase (JNK) and p38 activities, when it was overexpressed in Schneider cells. DMKP-3 interacted specifically with Drosophila ERK (DERK) via its N-terminal domain. In addition, DMKP-3 specifically inhibited Elk-1-dependent trans-reporter gene expression in mammalian CV1 cells, and dephosphorylated activated mammalian ERK in vitro. DMKP-3 is uniquely localized in the cytoplasm within Schneider cells, and gene expression is tightly regulated during development. Thus DMKP-3 is a Drosophila homologue of mammalian MKP-3, and may play important roles in the regulation of various developmental processes. Show less