Kyung-Bin Song

RhoB induces apoptosis via direct interaction with TNFAIP1 in HeLa cells.

RhoB, a tumor suppressor, has emerged as an interesting cancer target, and extensive studies aimed at understanding its role in apoptosis have been performed. In our study, we investigated the involvement of RhoB‐interacting molecules in apoptosis. To identify RhoB‐interacting proteins, we performed yeast‐two hybrid screening assays using RhoB as a bait and isolated TNFAIP1, a TNFα‐induced protein containing the BTB/POZ domain. The interaction between RhoB and TNFAIP1 was demonstrated in vivo through coimmunoprecipitation studies and in vitro binding assays. RFP‐TNFAIP1 was found to be partially colocalized with EGFP‐RhoB. The partial colocalization of RhoB and TNFAIP1 in endosomes suggests that RhoB‐TNFAIP1 interactions may have a functional role in apoptosis. TNFAIP1 elicited proapoptotic activity, while simultaneous expression of RhoB and TNFAIP1 resulted in a dramatic increase in apoptosis in HeLa cells. Furthermore, knockdown of RhoB using siRNA clearly rescued cells from apoptosis induced by TNFAIP1. This finding suggests that interactions between RhoB and TNFAIP1 are crucial for induction of apoptosis in HeLa cells. The observation of increased SAPK/JNK phosphorylation in apoptotic cells and the finding that a JNK inhibitor suppressed apoptosis indicates that SAPK/JNK signaling may be involved in apoptosis induced by RhoB‐TNFAIP1 interactions. In conclusion, we found that RhoB interacts with TNFAIP1 to regulate apoptosis via a SAPK/JNK‐mediated signal transduction mechanism.

Reactive oxygen species-mediated activation of the Akt/ASK1/p38 signaling cascade and p21Cip1 downregulation are required for shikonin-induced apoptosis

Shikonin derivatives exert powerful cytotoxic effects, induce apoptosis and escape multidrug resistance in cancer. However, the diverse mechanisms underlying their anticancer activities are not completely understood. Here, we demonstrated that shikonin-induced apoptosis is caused by reactive oxygen species (ROS)-mediated activation of Akt/ASK1/p38 mitogen-activated protein kinase (MAPK) and downregulation of p21Cip1. In the presence of shikonin, inactivation of Akt caused apoptosis signal-regulating kinase 1 (ASK1) dephosphorylation at Ser83, which is associated with ASK1 activation. Shikonin-induced apoptosis was enhanced by inhibition of Akt, whereas overexpression of constitutively active Akt prevented apoptosis through modulating ASK1 phosphorylation. Silencing ASK1 and MKK3/6 by siRNA reduced the activation of MAPK kinases (MKK) 3/6 and p38 MAPK, and apoptosis, respectively. Antioxidant N-acetyl cysteine attenuated ASK1 dephosphorylation and p38 MAPK activation, indicating that shikonin-induced ROS is involved in the activation of Akt/ASK1/p38 pathway. Expression of p21Cip1 was significantly induced in early response, but gradually decreased by prolonged exposure to shikonin. Overexpression of p21Cip1 have kept cells longer in G1 phase and attenuated shikonin-induced apoptosis. Depletion of p21Cip1 facilitated shikonin-induced apoptosis, implying that p21Cip1 delayed shikonin-induced apoptosis via G1 arrest. Immunohistochemistry and in vitro binding assays showed transiently altered localization of p21Cip1 to the cytoplasm by shikonin, which was blocked by Akt inhibition. The cytoplasmic p21Cip1 actually binds to and inhibits the activity of ASK1, regulating the cell cycle progression at G1. These findings suggest that shikonin-induced ROS activated ASK1 by decreasing Ser83 phosphorylation and by dissociation of the negative regulator p21Cip1, leading to p38 MAPK activation, and finally, promoting apoptosis.

Association of Obesity with Serum Leptin, Adiponectin, and Serotonin and Gut Microflora in Beagle Dogs

Background Serotonin (5‐hydroxytryptamine, 5HT) is involved in hypothalamic regulation of energy consumption. Also, the gut microbiome can influence neuronal signaling to the brain through vagal afferent neurons. Therefore, serotonin concentrations in the central nervous system and the composition of the microbiota can be related to obesity. Objective To examine adipokine, and, serotonin concentrations, and the gut microbiota in lean dogs and dogs with experimentally induced obesity. Animals Fourteen healthy Beagle dogs were used in this study. Methods Seven Beagle dogs in the obese group were fed commercial food ad libitum, over a period of 6 months to increase their weight and seven Beagle dogs in lean group were fed a restricted amount of the same diet to maintain optimal body condition over a period of 6 months. Peripheral leptin, adiponectin, 5HT, and cerebrospinal fluid (CSF‐5HT) levels were measured by ELISA. Fecal samples were collected in lean and obese groups 6 months after obesity was induced. Targeted pyrosequencing of the 16S rRNA gene was performed using a Genome Sequencer FLX plus system. Results Leptin concentrations were higher in the obese group (1.98 ± 1.00) compared to those of the lean group (1.12 ± 0.07, P = .025). Adiponectin and 5‐hydroytryptamine of cerebrospinal fluid (CSF‐5HT) concentrations were higher in the lean group (27.1 ± 7.28) than in the obese group (14.4 ± 5.40, P = .018). Analysis of the microbiome revealed that the diversity of the microbial community was lower in the obese group. Microbes from the phylum Firmicutes (85%) were predominant group in the gut microbiota of lean dogs. However, bacteria from the phylum Proteobacteria (76%) were the predominant group in the gut microbiota of dogs in the obese group. Conclusions and Clinical Importance Decreased 5HT levels in obese group might increase the risk of obesity because of increased appetite. Microflora enriched with gram‐negative might be related with chronic inflammation status in obese dogs.

Increase of RhoB in γ-radiation-induced apoptosis is regulated by c-Jun N-terminal kinase in Jurkat T cells

The Ras-related small GTP-binding protein RhoB is known to be a pro-apoptotic protein and immediate-early inducible by genotoxic stresses. In addition, JNK activation is known to function in gamma-radiation-induced apoptosis. However, it is unclear how JNK activation and gamma-radiation-dependent RhoB induction are related. Here we verified the relationship between JNK activation and RhoB induction. RhoB induction by gamma-radiation occurred at the transcriptional level and transcriptional activation of RhoB was concomitant with an increase in RhoB protein. gamma-Radiation-induced RhoB expression was markedly attenuated by pretreatment with a JNK-specific inhibitor, SP600125, but not by a p38 MAPK inhibitor, SB203580. Inhibition of JNK caused a decrease in early apoptotic cell death that correlated with RhoB expression. However, PI3K inhibition had no significant effects, indicating that the AKT survival pathway was not involved. The siRNA knockdown of JNK resulted in a decrease in RhoB expression and the siRNA knockdown of RhoB restored cell growth even in the gamma-irradiated cells. These results suggest that RhoB regulation involves the JNK pathway and contributes to the early apoptotic response of Jurkat T cells to gamma-radiation.

DNA damage-induced apoptosis suppressor (DDIAS), a novel target of NFATc1, is associated with cisplatin resistance in lung cancer

In a previous study, we reported that DNA damage induced apoptosis suppressor (DDIAS; hNoxin), a human homolog of mouse Noxin, functions as an anti-apoptotic protein in response to DNA repair. Here we reveal that DDIAS is a target gene of nuclear factor of activated T cells 2 (NFATc1) and is associated with cisplatin resistance in lung cancer cells. In the DDIAS promoter analysis, we found that NFATc1 activated the transcription of DDIAS through binding to NFAT consensus sequences in the DDIAS promoter. In addition, tissue array immunostaining revealed a correlation between DDIAS and NFATc1 expression in human lung tumors. NFATc1 knockdown or treatment with the NFAT inhibitor cyclosporine A induced apoptosis and led to growth inhibition of lung cancer cells, indicating the functional relevance of both the proteins. In contrast, DDIAS overexpression overcame this NFATc1 knockdown-induced growth inhibition, supporting the cancer-specific role of DDIAS as a target gene of NFATc1. NFATc1 or DDIAS inhibition clearly enhanced apoptosis induced by cisplatin in NCI-H1703 and A549 cells. Conversely, DDIAS overexpression rescued NCI-H1703 cells from cisplatin-mediated cell death and caspase-3/7 activation. These results suggest that NFATc1-induced DDIAS expression contributes to cisplatin resistance, and targeting DDIAS or NFATc1 impairs the mechanism regulating cisplatin resistance in lung cancer cells. Taken together, DDIAS is a target of NFATc1 and is associated with cisplatin resistance in lung cancer cells.

NSC126188, a piperazine alkyl derivative, induces apoptosis via upregulation of RhoB in HeLa cells

SummaryWe describe here a piperazine alkyl derivative, NSC126188, which induced apoptosis of HeLa cells by upregulating RhoB expression. NSC126188 caused multi-septation of fission yeast and hypersensitized a ∆rho3 mutant, which implicates the involvement of functional human homolog RhoB. The treatment of cells with NSC126188 induced apoptosis and a dramatic increase in RhoB expression. In addition, RhoB knockdown using siRNA rescued cells from apoptosis, indicating a crucial role of RhoB in NSC126188-induced apoptosis. In a reporter assay using luciferase and EGFP under control of the RhoB promoter, NSC126188 increased both luciferase activity and the expression of EGFP, implicating transcriptional activation of RhoB by NSC126188. Furthermore, NSC126188 demonstrated in vivo anti-tumor activity, inhibiting tumor growth by 66.8% in a nude mouse xenograft using PC-3 human prostate cancer cells. These results suggest that NSC126188 is a potential lead compound and that upregulation of RhoB is associated with NSC126188-induced apoptosis.

Identification of small molecules inducing apoptosis by cell-based assay using fission yeast deletion mutants.

SummaryThe cell-based assay using yeast deletion mutants has been recognized as an efficient analysis to discover therapeutic compounds and reveal their mode of action. In this study, S. pombe deletion mutants-based HTS screening was carried out to identify potential anti-cancer agents. The NCI chemical library of 5700 compounds was screened using kit strains, which consisted of S. pombe mutants harboring deletions in genes involved in DNA repair and mitotic control. During the screening, we identified 40 compounds conferring growth inhibition of S. pombe. Their anti-tumorigenic properties were examined by phenotypic effect on S. pombe, flow cytometry and apoptosis analysis of human cancer. Here, we report hit compounds inducing apoptosis for development of anti-cancer agents suggesting that S. pombe deletion mutants are useful in identifying potential anti-cancer agents in human cancer therapeutics.

Serological update and molecular characterization of Dirofilaria immitis in dogs, South Korea.

Eighty-one dogs in the Chungnam province were tested for heartworm (Dirofilaria immitis) infection by ELISA (SNAP test, IDEXX Laboratories, Maine, USA). Seventeen (20.9%) of the 81 samples were found to be positive and further analyzed by 16S rRNA sequencing. In this study, all dogs tested lived outdoors. Using the chi(2) test and Fishers exact test, no significant differences in the prevalence of dirofilariasis were observed among different gender and age groups, although the prevalence of this disease among dogs 2-4yrs of age remains highest. Sequence analysis revealed that the species prevalent in Chungnam province were genetically distinct from the type strain of D. immitis based on the nucleotide deletion found at position nt 276 (cytosine) and nucleotide substitution at position 428 (G to A) of the partial 16S rRNA sequence of the type strain. Furthermore, phylogenetic analysis suggests at least 2 groups of D. immitis circulating in the Chungnam area between the year 2007 and 2008.

Generation of expression vectors for high-throughput functional analysis of target genes in Schizosaccharomyces pombe

An immediate challenge in the post-genomic era is to assign a biological functions to proteins unraveled by genome analysis. This report is based on studies conducted using Schizosaccharomyces pombe, a simple model organism, and presents various vector systems as tools for high-throughput functional analysis of human genes. We constructed S. pombe expression vectors for efficient cloning of genes via the Gateway system. We modified the pREP and pSLF series vectors, which are widely used for gene expression in S. pombe. The vectors constructed have a uniform backbone of S. pombe autonomously replicating sequence (ARS) elements with different selective markers, namely, urw4+ and Saccharomyces cerevisiae LEU2 complementing leul. These vectors contain 3 different strengths of the inducible promoter nmtl, which affect the expression levels of the cloned open reading frames (ORFs). Further, target proteins can be fused with an N-terminal or C-terminal tag such as triple hemagglutinin (3× HA), enhanced green fluorescent protein (EGFP), or Discosoma red fluorescent protein (DsRed). We tested the feasibility of the constructed vectors by using 3 human genes, namely, RAB18, SCC-112, and PTEN. Proper expression of tagged RAB18 was confirmed by western blot analysis. Further, localization of RAB18, SCC112, and PTEN was demonstrated. The constructed vectors can be utilized for high-throughput functional analysis of heterologous genes.

Development of episomal vectors carrying a nourseothricin‐resistance marker for use in minimal media for Schizosaccharomyces pombe

In the post‐genomic era, an immediate challenge is to assign biological functions to novel proteins encoded by the genome. This challenge requires the use of a simple organism as a genetic tool and a range of new high‐throughput techniques. Schizosacchromyces pombe is a powerful model organism used to investigate disease‐related genes and provides useful tools for the functional analysis of heterologous genes. To expand the current array of experimental tools, we constructed two series of Sz. pombe expression vectors, i.e. general and Gateway vectors, containing nourseothricin‐resistance markers. Vectors carrying nourseothricin‐resistance markers possess advantages in that they do not limit the parental strains with auxotrophic mutations with respect to availability for use in clone selection and can be used together with vectors carrying nutrient markers in minimal media. We modified the pSLF173, pSLF273 and pSLF373 vectors carrying a triple haemagglutinin epitope (3×HA) and an Ura4 marker. The vectors described here contain the nmt1 promoter with three different episomal expression strengths for proteins fused with 3×HA, EGFP or DsRed at the N‐terminus. These vectors represent an important contribution to the genome‐wide investigation of multiple heterologous genes and for functional and genetic analysis of novel human genes. Copyright