• Biomedical Science Letters
• /
• v.20 no.4
• /
• pp.237-243
• /
• 2014

Triglyceride (TG) can cause death of macrophages and formation of foam cells thereby increasing inflammation in atherosclerotic plaques. Accumulation of cholesterol in macrophages is another critical event that promotes development of inflammatory cardiovascular diseases. Several proteins are known to transport intracellular cholesterol outside of the cell and these proteins are thought to be protective against atherosclerosis pathogenesis. It is unknown whether TG can affect cholesterol efflux in macrophages. In the current study, we examined mRNA expression levels of genes that promote efflux of cholesterol (ABCA1, ABCG1 and SR-B1). We found that TG treated THP-1 macrophages exhibited an increase in ABCG1 expression in a dose- and time-dependent manner. In contrast, the expression of ABCA1 and SR-B1 remained unchanged. To identify cell signaling pathways that participate in up-regulation of ABCG1, THP-1 macrophages were treated with various cell signaling inhibitors. We found that inhibition of the JNK and p38 MAPK pathway completely abrogated up-regulation of ABCG1 whereas inhibition of MEK1 further enhanced ABCG1 expression in TG treated THP-1 macrophages. Also, TG induced phosphorylation of JNK and p38 MAPK in THP-1 macrophages. These results suggest that TG may potentially influence cholesterol efflux in macrophages.

• BMB Reports
• /
• v.35 no.1
• /
• pp.41-46
• /
• 2002

• Proceedings of the Korean Society of Potoscience Conference
• /
• 2005.06a
• /
• pp.41-41
• /
• 2005

• The Korean Journal of Physiology and Pharmacology
• /
• v.13 no.1
• /
• pp.39-47
• /
• 2009

Gaegurin 4(GGN 4), an antimicrobial peptide isolated from a Korean frog, is five times more potent against Gram-positive than Gram-negative bacteria, but has little hemolytic activity. To understand the mechanism of such cell selectivity, we examined GGN4-induced $K^+$ efflux from target cells, and membrane conductances in planar lipid bilayers. The $K^+$ efflux from Gram-positive M. luteus(2.5 ${\mu}g/ml$) was faster and larger than that from Gram-negative E. coli(75 ${\mu}g/ml$), while that from RBC was negligible even at higher concentration(100 ${\mu}g/ml$). GGN4 induced larger conductances in the planar bilayers which were formed with lipids extracted from Gram-positive B. subtilis than in those from E. coli(p<0.01), however, the effects of GGN4 were not selective in the bilayers formed with lipids from E. coli and red blood cells. Addition of an acidic phospholipid, phosphatidylserine to planar bilayers increased the GGN4-induced membrane conductance(p<0.05), but addition of phosphatidylcholine or cholesterol reduced it(p<0.05). Transmission electron microscopy revealed that GGN4 induced pore-like damages in M. luteus and dis-layering damages on the outer wall of E. coli. Taken together, the present results indicate that the selectivity of GGN4 toward Gram-positive over Gram-negative bacteria is due to negative surface charges, and interaction of GGN4 with outer walls. The selectivity toward bacteria over RBC is due to the presence of phosphatidylcholine and cholesterol, and the trans-bilayer lipid asymmetry in RBC. The results suggest that design of selective antimicrobial peptides should be based on the composition and topology of membrane lipids in the target cells.

• Molecules and Cells
• /
• v.38 no.2
• /
• pp.180-186
• /
• 2015

Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the ${\alpha}$-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.

• BMB Reports
• /
• v.28 no.6
• /
• pp.552-555
• /
• 1995

Treatment of microsomal vesicles isolated from etiolated Pisum sativum L cv. Alaska epicotyl tissue with agents inhibiting protein dephosphorylation, namely NaF and/or ATP, resulted in increased binding of the phytotropin NPA to the putative auxin efflux carriers localized on the plasma membrane. The phytotropin effect was especially conspicuous if the vesicles were simultaneously treated with Triton X-100. Kinetic analysis of the binding indicated the existance of two distinct sites for NPA, each having different affinities. Increased binding of the phytotropin to the membrane where protein dephosphorylation was inhibited was attributable to the increased ligand affinity of both sites. Treatment of tissue segments with flubride was found to enhance in vivo auxin transport. Implications of covalent modification of the auxin efflux carrier complex for the regulation of membrane transport of auxin molecules are discussed.

• Proceedings of the Plant Resources Society of Korea Conference
• /
• 2018.04a
• /
• pp.59-59
• /
• 2018

Panax ginseng Meyer (Korean ginseng) is in the spotlight of Oriental medicine and is proclaimed as the king of medicinal plants owing to its adaptogenic characteristics. Ginseng root rot is a devastating disease caused by the fungus, Ilyonectria mors-panacis that generally attacks younger roots (~2 years), leading to defects in root quality, ginsenoside accumulation and also life cycle of the plant. Hence, there is an indispensable need to develop strategies resulting in tolerance against ginseng root rot. In the present study, we evaluated the effect of silica nanoparticles(N-SiO2) in Panax ginseng during I. mors-panacis infection. Long term analysis (30 dpi) revealed a striking 50% reduction in disease severity index upon 1mM and 2mM treatment of N-SiO2. However, N-SiO2 did not have any direct antifungal activity against I. mors-panacis. Membrane bound sugar efflux transporter, SWEET (Sugars Will Eventually be Exported Transporters) was identified in ginseng and as expected, its expression was suppressed upon N-SiO2 treatment in the root rot pathosystem. Furthermore, the total and reducing sugars in the apoplastic fluid clearly revealed that N-SiO2 regulates sugar efflux into apoplast. In a nut shell, N-SiO2 administration induces transcriptional reprogramming in ginseng roots, leading to regulated sugar efflux into apoplast resulting in enhanced tolerance against I. mors-panacis.

• The Korean Journal of Pharmacology
• /
• v.18 no.2
• /
• pp.89-102
• /
• 1982

The $Na^+-and\;K^+-induced\;Ca^{++}$ release was measured isotopically by millipore filter technique in pig heart mitochondria. With EGTA-quenching technique, the characteristics of mitochondrial $Ca^{++}-pool$ and the sources of $Ca^{++}$ released from mitochondria by $Na^+\;or\;K^+$ were analyzed. The mitochondrial $Ca^{++}-pool$ could be distinctly divided into two components: internal and external ones which were represented either by uptake through inner membrane, or by energy independent passive binding to external surface of mitochondria, respectively. In energized mitochondria, a large portion of $Ca^{++}$was transported into internal pool with little external binding, while in de-enerigzed state, a large portion of transported $Ca^{++}$ existed in the external pool with limited amount of $Ca^{++}$ in the internal pool which was possibly transported through the $Ca^{++}-carrier$ present in the inner membrane. $Na^+$ induced the $Ca^{++}$ release from both internal pool and external pool and external binding pool of mitochondria. In contrast, $K^+$ did not affect $Ca^{++}$ of the internal pool, but, displaced $Ca^{++}$ bound to external surface of the mitochondria. When the $Ca^{++}-reuptake$ was blocked by EGTA, the $Ca^{++}$ release from the internal pool by $Na^+$ was rapid; the rate of $Ca^{++}-efflux$ appeared to be a function of $[Na^+]^2$ and about 8mM $Na^+$ was required to elicit half-maximal velocity of $Ca^{++}-efflux$. So it was revealed that $Ca^{++}-efflux$ velocity was particulary sensitive to small changes of the $Na^+$ concentration in physiological range. Energy independent $Ca^{++}-binding$ sites of mitochondrial external surface showed unique characteristics. The total number of external $Ca^{++}-binding$ sites of pig heart mitochondria was 29 nmoles per mg protein and the dissociation constant(Kd) was $34{\mu}M$. The $Ca^{++}-binding$ to the external sites seemed to be competitively inhibited by $Na^+\;and\;K^+$; the inhibition constant(Ki) were 9.7 mM and 7.1 mM respectively. Considering the intracellular ion concentrations and large proportion of $Ca^{++}$ uptake in energized mitochondria, the external $Ca^{++}-binding$ pool of the mitochondria did not seem to play a significant role on the regulation of intracellular free $Ca^{++}$ concentration. From this experiment, it was suggested that a small change of intracellular free $Na^+$ concentration might play a role on regulation of free $Ca^{++}$ concentration in cardiac cell by influencing $Ca^{++}-efflux$ from the internal pool of mitochondria.

• Proceedings of the Zoological Society Korea Conference
• /
• 1998.10b
• /
• pp.77-77
• /
• 1998

No Abstract, See Full Text

• Journal of Pharmaceutical Investigation
• /
• v.31 no.4
• /
• pp.209-216
• /
• 2001

The purpose of the present study was to investigate the hepatic uptake and biliary excretion of l-anilino-8-naphthalene sulfonate (ANS) in vivo. The plasma concentration and liver concentration of ANS were determined after its i.v. bolus administration at a dose of $30\;{\mu}mol/kg$ in rats. The hepatic uptake clearance $(CL_{uptake})$ of ANS was 0.1 ml/min/g liver. On the basis of the unbound concentration of ANS, the permeability-surface area product $(PS_{influx})$ was calculated to be l0.4 ml/min/g liver, being comparable of in vitro data. On the other hand, we determined the plasma concentration, liver concentration and biliary excretion rate of ANS at steady-state after its i. v. infusion $(0.2-1.6\;{\mu}mol/min/kg)$ in rats. The excretion clearance $(CL_{excretion})$ of ANS showed Michaelis-Menten kinetics with increasing the infusion rate. The permeability-surface area product $(PS_{excretion})$ based on the unbound concentration in the liver was calculated to be 0.0165 ml/min/g liver, which is negligible compared with the intrinsic clearance $(CL_{int}=3.3\;ml/min/g\;liver)$ by rat liver microsomes. The sequestration process of ANS, therefore, was considered to be mainly due to the metabolic process in the liver $(PS_{seq}{\risingdotseq}CL_{int})$. Furthermore, $PS_{efflux}$ value calculated from $PS_{influx}$ and $PS_{seq}$ was 4.4 ml/min/g liver, which was comparable of in vitro data. In conclusion, in vivo parameters such as $PS_{influx}$, $PS_{efflux}$ and $PS_{seq}$ in the present study showed good in vivo-in vitro relationship. Thus, the kinetic analysis method proposed in the present study would be useful to analyze the hepatic transport of drugs in vivo.