• Journal of Life Science
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• v.28 no.2
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• pp.162-169
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• 2018

Many cytoplasmic proteins are targeted to the cytoplasmic membrane of the trans-Golgi network (TGN) via an N-terminal short helix. We previously showed that the 20 N-terminal amino acids of Aplysia phosphodiesterase 4 (ApPDE4) long form are sufficient for its targeting to the plasma membrane and the TGN. The N-terminus of the ApPDE4 long form binds to PI4P and sulfatide in vitro. Therefore, in order to decipher the roles of sulfatide in Golgi complex targeting, we examined the cellular localization of sulfatide-binding peptides. In this study, we found that enhanced green fluorescent protein (EGFP) fused to the C-terminus of modified sulfatide- and heparin-binding peptides (mHSBP-EGFP) was localized to the TGN. On the other hand, its mutant, in which tryptophan was replaced with an alanine, leading to the impairment of heparin and sulfatide binding, was localized to cytosol. We also found that the TGN targeting of mHSBP-EGFP is impaired by the treatment of antimycin A, phenylarsine oxide (PAO), and adenosine but not a high concentration of wortmannin. These results suggest that PAO and adenosine-sensitive kinases, including phosphatidylinositol 4-kinase II, may play key roles in the recruitment of mHSBP-EGFP.

• Journal of Life Science
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• v.28 no.7
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• pp.778-785
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• 2018

Autophagy is a complex signaling process and has been implicated in tumor suppression and anticancer therapy resistance. Autophagy can produce tumor-suppressive effect by inducing autophagic cell death, either in collaboration with apoptosis. In this current study, we found that celecoxib (CCB), a nonsteroidal anti-inflammatory drug (NSAID) with multifaceted effects, induced autophagy including enhanced LC3 conversion (LC3-I to LC3-II) and reduced autophagy substrate protein p62 level in multidrug-resistant (MDR) cancer cells. CCB sensitized human multidrug resistant (MDR) cancer cells to the ansamycin-based HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG), a benzoquinoid ansamycin, which causes the degradation of several oncogenic and signaling proteins, by inducing autophagic cell death and apoptosis. CCB significantly augmented 17-AAG-mediated level of LC3-II/LC-I, indicating the combined effect of 17-AAG and CCB on the induction of autophagy. Autophagic degradation of mutant p53 (mutp53) and activation of caspase-3 in 17-AAG-treated MDR cells were accelerated by CCB. Inhibition of caspase-3-mediated apoptotic pathway by Z-DEVD-FMK, a caspase-3 inhibitor, did not completely block CCB-induced cell death in MCF7-MDR cells. In addition, treatment of MDR cells with Z-DEVD-FMK failed to prevent activation of autophagy by combined treatment with 17-AAG and CCB. Based on our findings, the ability of clinically used drug CCB to induce autophagy has important implications for its development as a sensitizing agent in combination with Hsp90 inhibitor of MDR cancer.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.6
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• pp.460-465
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• 2010

Introduction: A cleft palate is a common birth defect in humans with an incidence of 1/500 to 1/1,000 births. It appears to be caused by multiple genetic and environmental factors during palatogenesis. Many molecules are involved in palate formation but the biological mechanisms underlying the normal palate formation and cleft palate are unclear. Accumulating evidence suggests that transforming growth factor $\beta$/bone morphogenetic proteins (TGF-$\beta$/BMP) family members mediate the epithelial-mesenchymal interactions during palate formation. However, their roles in palatal morphogenesis are not completely understood. Materials and Methods: To understand the roles of TGF-$\beta$/BMP signaling in vivo during palatogenesis, mice with a palatal mesenchyme- specific deletion of Smad4, a key intracellular mediator of TGF-$\beta$/BMP signaling, were generated and analyzed using the Osr2Ires-Cre mice. Results: The mutant mice were alive at the time of birth with open eyelids and complete cleft palate but died within 24 hours after birth. In skeletal preparation, the horizontal processes of the palatine bones in mutants were not formed and resulted in a complete cleft palate. At E13.5, the palatal shelves of the mutants were growing as normally as those of theirwild type littermates. However, the palatal shelves of the mutants were not elevated at E14.5 in contrast to the elevated palatal shelves of the wild type mice. At E15.5, the palatal shelves of the mutants were elevated over the tongue but did not come in contact with each other, resulting in a cleft palate. Conclusion: These results suggest that mesenchymal Smad4 mediated signaling is essential for the growth of palatal processes and suggests that TGF-$\beta$/BMP family members are essential regulators during palate development.

• Molecules and Cells
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• v.43 no.5
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• pp.469-478
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• 2020

Hepatitis C virus (HCV) propagation is highly dependent on cellular proteins. To identify the host factors involved in HCV propagation, we previously performed protein microarray assays and identified the LIM and SH3 domain protein 1 (LASP-1) as an HCV NS5A-interacting partner. LASP-1 plays an important role in the regulation of cell proliferation, migration, and protein-protein interactions. Alteration of LASP-1 expression has been implicated in hepatocellular carcinoma. However, the functional involvement of LASP-1 in HCV propagation and HCV-induced pathogenesis has not been elucidated. Here, we first verified the protein interaction of NS5A and LASP-1 by both in vitro pulldown and coimmunoprecipitation assays. We further showed that NS5A and LASP-1 were colocalized in the cytoplasm of HCV infected cells. NS5A interacted with LASP-1 through the proline motif in domain I of NS5A and the tryptophan residue in the SH3 domain of LASP-1. Knockdown of LASP1 increased HCV replication in both HCV-infected cells and HCV subgenomic replicon cells. LASP-1 negatively regulated viral propagation and thereby overexpression of LASP-1 decreased HCV replication. Moreover, HCV propagation was decreased by wild-type LASP-1 but not by an NS5A binding-defective mutant of LASP-1. We further demonstrated that LASP-1 was involved in the replication stage of the HCV life cycle. Importantly, LASP-1 expression levels were increased in persistently infected cells with HCV. These data suggest that HCV modulates LASP-1 via NS5A in order to regulate virion levels and maintain a persistent infection.

• Nutrition Research and Practice
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• v.11 no.3
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• pp.190-197
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• 2017

BACKGROUND/OBJECTIVES: Gallus gallus domesticus (GD) is a natural mutant breed of chicken in Korea with an atypical characterization of melanin in its tissue. This study investigated the effects of melanin extracts of GD on osteoblast differentiation and inhibition of osteoclast formation. MATERIALS/METHODS: The effects of the melanin extract of GD on human osteoblast MG-63 cell differentiation were examined by evaluating cell viability, osteoblast differentiation, and expression of osteoblast-specific transcription factors such as bone morphogenetic protein 2 (BMP-2), small mothers against decapentaplegic homologs 5 (SMAD5), runt-related transcription factor 2 (RUNX2), osteocalcin and type 1 collagen (COL-1) by reverse transcription-polymerase chain reaction and western blotting analysis. We investigated the inhibitory effect of melanin on the osteoclasts formation through tartrate-resistant acid phosphatase (TRAP) activity and TRAP stains in Raw 264.7 cell. RESULTS: The melanin extract of GD was not cytotoxic to MG-63 cells at concentrations of $50-250{\mu}g/mL$. Alkaline phosphatase (ALP) activity and bone mineralization of melanin extract-treated cells increased in a dose-dependent manner from 50 to $250{\mu}g/mL$ and were 149% and 129% at $250{\mu}g/mL$ concentration, respectively (P < 0.05). The levels of BMP-2, osteocalcin, and COL-1 gene expression were significantly upregulated by 1.72-, 4.44-, and 2.12-fold in melanin-treated cells than in the control cells (P < 0.05). The levels of RUNX2 and SMAD5 proteins were higher in melanin-treated cells than in control vehicle-treated cells. The melanin extract attenuated the formation of receptor activator of nuclear factor kappa-B ligand-induced TRAP-positive multinucleated RAW 264.7 cells by 22%, and was 77% cytotoxic to RAW 264.7 macrophages at a concentration of $500{\mu}g/mL$. CONCLUSIONS: This study provides evidence that the melanin extract promoted osteoblast differentiation by activating BMP/SMADs/RUNX2 signaling and regulating transcription of osteogenic genes such as ALP, type I collagen, and osteocalcin. These results suggest that the effective osteoblastic differentiation induced by melanin extract from GD makes it potentially useful in maintaining bone health.

• Microbiology and Biotechnology Letters
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• v.31 no.2
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• pp.140-144
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• 2003

Type Ⅰ signal peptidase is an integral membrane protein that functions to cleave signal peptides from secreted and membrane proteins. The enzyme serves as a potential target for the development of novel antibacterial agents due to its unique physiological properties. Despite being one of the best characterized enzymes, the catalysis of Type Ⅰ signal peptidase still remains controversy over the catalytic serine/lysine dyad mechanism. It appears that the dyad proteases are generally less efficient than the prototypical serine/histidine/aspartic acid triad found in most enzymes, although Type Ⅰ signal peptidase is an exception to this rule. In this paper, we have proposed that Type Ⅰ signal peptidase may act as the serine/lysine/aspartic acid triad cataltytic mechanism. Therefore, the aspartic acid 99 residue in the E. coli signal peptidase was chosen and mutated to an alanine to see if there is any possible role of the aspartic acid in the catalytic function. Type Ⅰ signal peptidase D99A protein was inactive in vitro assay using the procoat synthesized by in vitro transcription translation. However, the mutant was active using a highly sensitive in vivo assay. Pulse-chase experiments show that the replacement of aspartic acid 99 with alanine results in a very unstable signal peptidase molecule. Therefore, we conclude that it is unlikely that the residue is directly involved in catalysis, but rather plays an important role in stabilizing the protein structure.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.301-310
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• 2010

Bacillus subtilis strains produce a broad spectrum of bioactive peptides. The lipopeptide surfactin belongs to one well-known class, which includes amphiphilic membrane-active biosurfactants and peptide antibiotics. Both the srfA promoter and the ComP-ComA signal transduction system are an important part of the factor that results in the production of surfactin. Bs-M49, obtained by means of low-energy ion implantation in wild-type Bs-916, produced significantly lower levels of surfactin, and had no obvious effects against R. solani. Occasionally, we found strain Bs-M49 decreased spore formation and the development of competence. Blast comparison of the sequences from Bs-916 and M49 indicate that there is no difference in the srfA operon promoter PsrfA, but there are differences in the coding sequence of the comA gene. These differences result in three missense mutations within the M49 ComA protein. RT-PCR analyses results showed that the expression levels of selected genes involved in competence and sporulation in both the wild-type Bs-916 and mutant M49 strains were significantly different. When we integrated the comA ORF into the chromosome of M49 at the amyE locus, M49 restored hemolytic activity and antifungal activity. Then, HPLC analyses results also showed the comA-complemented strain had a similar ability to produce surf actin with wild-type strain Bs-916. These data suggested that the mutation of three key amino acids in ComA greatly affected the biological activity of Bacillus subtilis. ComA protein 3D structure prediction and motif search prediction indicated that ComA has two obvious motifs common to response regulator proteins, which are the N-terminal response regulator receiver motif and the C-terminal helix-turn-helix motif. The three residues in the ComA N-terminal portion may be involved in phosphorylation activation mechanism. These structural prediction results implicate that three mutated residues in the ComA protein may play an important role in the formation of a salt-bridge to the phosphoryl group keeping active conformation to subsequent regulation of the expression of downstream genes.

• Journal of Microbiology and Biotechnology
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• v.27 no.8
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• pp.1461-1471
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• 2017

Escherichia coli heat-labile enterotoxin (LT) and its non-toxic mutant (LTm) are well-known powerful mucosal adjuvants and immunogens. However, the yields of these adjuvants from genetically engineered strains remain at extremely low levels, thereby hindering their extensive application in fundamental and clinical research. Therefore, efficient production of these adjuvant proteins from genetically engineered microbes is a huge challenge in the field of molecular biology. In order to explore the expression bottlenecks of LTm in E. coli, we constructed a series of recombinant plasmids based on various considerations and gene expression strategies. After comparing the protein expression among strains containing different recombinant plasmids, the signal sequence was found to be critical for the expression of LTm and its subunits. When the signal sequence was present, the strong hydrophobicity and instability of this amino acid sequence greatly restricted the generation of subunits. However, when the signal sequence was removed, abundantly expressed subunits formed inactive inclusion bodies that could not be assembled into the hexameric native form, although the inclusion body subunits could be refolded and the biological activity recovered in vitro. Therefore, the dilemma choice of signal sequence formed bottlenecks in the expression of LTm. These results reveal the expression bottlenecks of LTm, provide guidance for the preparation of LTm and its subunits, and certainly help to promote efficient preparation of this mucosal adjuvant protein.

• KSBB Journal
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• v.26 no.6
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• pp.517-522
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• 2011

In our previous study, we isolated and characterized a 1-deoxynojirimycin (DNJ)-producing bacterium, Bacillus subtilis MORI, from chungkookjang, a Korean traditional food. B. subtilis MORI was subjected to ${\gamma}$-irradiation and the resulting bacteria were screened for increased DNJ production. A mutant was identified that produced 7.6 times more DNJ and named B. subtilis MORI 3K-85. In this study, the protein profiles of both strains were compared by one-dimensional and two-dimensional gel electrophoresis (1-DE and 2-DE, respectively) under both native and denaturing conditions. The 1-DE native-PAGE and 1-DE SDS-PAGE analyses identified 5 and 7 bands, respectively, that were found at higher concentrations in B. subtilis MORI 3K-85 than in B. subtilis MORI. Similarly, 2-DE analyses identified 20 protein spots which were found at higher concentrations in B. subtilis MORI 3K-85. The peptide mass profiles of these 20 proteins were analyzed by MALDI-TOF and compared with peptide sequences of B. subtilis and B. amyloliquefaciens in the MASCOT database. This screening suggested that three dehydrogenases, an aldolase, a synthetase, an isomerase, a reductase, and a peroxidase are elevated in B. subtilis MORI 3K-85. Based on this data, one or more of the elevated 8 enzymes might be related to the DNJ biosynthetic pathway.

• Journal of Life Science
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• v.20 no.10
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• pp.1451-1457
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• 2010

Serotonin (5-hydroxytryptamine, 5-HT) is an important mediator of cell-cell signaling in neuronal systems. The serotonin transporter (SERT) on the plasma membrane controls the extracellular 5-HT level by reuptake of released 5-HT from the synaptic cleft, but the underlying regulation mechanism is unclear. Here, we used the yeast two-hybrid system to identify the specific binding protein(s) that interacts with the carboxyl (C)-terminal region of SERT and found a specific interaction with protein kinase C-$\varepsilon$ (PKC-$\varepsilon$), a PKC isotype that is characterized as a calcium-independent and phorbol ester/diacylglycerol-sensitive serine/threonine kinase. PKC-$\varepsilon$ bound to the tail region of SERT but not to other members of the $Na^+/Cl^-$ dependent SLC6 gene family in the yeast two-hybrid assay. The C-terminal region of PKC-$\varepsilon$ is essential for interaction with SERT. In addition, these proteins showed specific interactions in the glutathione S-transferase (GST) pull-down assay. PKC-$\varepsilon$ phosphorylated the peptide of the SERT amino (N)-terminus in vitro. These results suggest that the phosphorylation of SERT by PKC-$\varepsilon$ may regulate SERT activity in plasma membrane.