• BMB Reports
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• v.45 no.3
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• pp.159-164
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• 2012

CD99 is known to be involved in the regulation of cell-cell adhesion. However, it remains unclear whether CD99 controls cell-extracellular matrix adhesion. In this study, the effects of CD99 activation on cell-extracellular matrix adhesion were investigated. It was found that engagement of CD99 with the stimulating antibody YG32 downregulated the adhesion of MCF-7 cells to fibronectin, laminin and collagen IV in a dose-dependent manner. The CD99 effect on cell-ECM adhesion was inhibited by overexpression of the dominant negative form of CD99 or CD99 siRNA transfection. Treatment of cells with $Mn^{2+}$ or by ${\beta}_1$ integrin-stimulating antibody restored the inhibitory effect of CD99 on cell-ECM adhesion. Cross-linking CD99 inactivated ${\beta}_1$ integrin through conformational change. CD99 activation caused dephosphorylation at Tyr-397 in FAK, which was restored by the ${\beta}_1$ stimulating antibody. Taken together, these results provide the first evidence that CD99 inhibits cell-extracellular matrix adhesion by suppressing ${\beta}_1$ integrin affinity.

• Bulletin of the Korean Chemical Society
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• v.22 no.9
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• pp.979-983
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• 2001

Thermoanaerobacter ethanolicus is a strictly anaerobic and thermophilic bacterium whose optimum temperature ranges over $65-68^{\circ}C.$ T. ethanolicus was known to contain a bipolar very long chain fatty acyl component such as $\alpha$, $\omega-1316-dimethyloctacosanedioate$, as one of the major membrane components. However, exact physiological role of this unusual component in the membrane remains unknown. Such a very long chain fatty acyl component, $\alpha$, ${\omega}-1316-dimethyloctacosanedioate$, dimethyl ester (DME C30), was isolated, and purified from the membrane of T. ethanolicus. As a function of added concentrations of the $\alpha$, $\omega-1316-dimethyloctacosanedioate$, dimethyl ester (DME C30) or cholesterol into the standard liposomes, the acyl chain ordering effect was investigated by the steady-state anisotropy with 1,6-diphenyl-1,3,5-hexatriene (DPH) as a fluorescent probe. Acyl chain order parameter (S) of vesicles containing DME C30 is higher comparing with phosphatidylcholine (PC) only vesicles. This result was discussed thermodynamically with the aid of the simulated annealing molecular dynamics simulations. Through the investigation of all the possible conformational changes of DME C30 or cholesterol, we showed that DME C30 is very flexible and its conformation is variable depending on the temperature comparing with cholesterol, which is rigid and restricted at overall temperature. We propose that the conformational change of DME C30, not the configurational change, may be involved in the regulation of the membrane fluidity against the changes of external temperature.

• Molecules and Cells
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• v.28 no.1
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• pp.25-30
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• 2009

${\beta}$-Arrestins turn off G protein-mediated signals and initiate distinct G protein-independent signaling pathways. We previously demonstrated that angiotensin $AT_1$ receptorbound ${\beta}$-arrestin 1 is cleaved after $Phe^{388}$ upon angiotensin II stimulation. The mechanism and signaling pathway of angiotensin II-induced ${\beta}$-arrestin cleavage remain largely unknown. Here, we show that protein Tyr phosphatase activity is involved in the regulation of ${\beta}$-arrestin 1 cleavage. Tagging of green fluorescent protein (GFP) either to the N-terminus or C-terminus of ${\beta}$-arrestin 1 induced conformational changes and the cleavage of ${\beta}$-arrestin 1 without angiotensin $AT_1$ receptor activation. Orthovanadate and molybdate, inhibitors of protein Tyr phosphatase, attenuated the cleavage of C-terminal GFP-tagged ${\beta}$-arrestin 1 in vitro. The inhibitory effects of okadaic acid and pyrophosphate, which are inhibitors of protein Ser/Thr phosphatase, were less than those of protein Tyr phosphatase inhibitors. Cell-permeable pervanadate inhibited angiotensin II-induced cleavage of ${\beta}$-arrestin 1 in COS-1 cells. Our findings suggest that Tyr phosphorylation signaling is involved in the regulation of angiotensin II-induced ${\beta}$-arrestin cleavage.

• BMB Reports
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• v.32 no.3
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• pp.215-225
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• 1999

Phytochromes (with gene family members phyA, B, C, D, and E) are a wavelength-dependent light sensor or switch for gene regulation that underscore a number of photo responsive developmental and morphogenic processes in plants. Recently, phytochrome-like pigment proteins have also been discovered in prokaryotes, possibly functioning as an auto-phosphorylating/phosphate-relaying two-component signaling system (Yeh et al., 1997). Phytochromes are photochromically convertible between the light sensing Pr and regulatory active Pfr forms. Red light converts Pr to Pfr, the latter having a "switch-on" conformation. The Pfr form triggers signal transduction pathways to the downstream responses including the expression of photosynthetic and other growth-regulating genes. The components involved in and the molecular mechanisms of the light signal transduction pathways are largely unknown, although G-proteins, protein kinases, and secondary messengers such as $Ca^{2+}$ ions and cGMP are implicated. The 124-127 kDa phytochromes form homodimeric structures. The N-terminal half contains the tetrapyrrolic phytochromobilin for red/far-red light absorption. The C-terminal half includes both a dimerization motif and regulatory box where the red light signal perceived by the chromophore-domain is recognized and transduced to initiate the signal transduction cascade. A working model for the inter-domain signal communication within the phytochrome molecule is proposed in this Review.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.4
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• pp.1599-1603
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• 2012

Objectives: Since methylenetetrahydrofolate reductase (MTHFR) maintains the balance of circulating folate and methionine and blocks the formation of homocysteine, its regulation in relation to different cancers has extensively been studied in different populations. However, information on Pakistani breast cancer patients is lacking. The MTHFR gene has two most common mutations that are single nucleotide additions which result in change of amino acids C677T to Ala222val and A1298C to Glu429Ala. Methodology: 110 sporadic breast patients with no prior family history of cancer or any other type of genetic disorders along with 110 normal individuals were screened for mutations in exons 1 to exon 9 using single strand conformational polymorphism, RFLP and sequencing analyzer. Results: The p values for the 677CC, 677CT, and 677TT genotypes were 0.223, 0.006, and 0.077, respectively. Those for the 1298AA, 1298AC, and 1298CC genotypes were 0.555, 0.009, and 0.003, respectively. Conclusions: We found an overall a significant, weak inverse association between breast cancer risk and the 677TT genotype and an inverse association with the 1298C variant. These results for MTHFR polymorphism might be population specific in sporadic breast cancer affected patients but many other factors need to be excluded before making final conclusions including folate intake, population and disease heterogeneity.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2008.04a
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• pp.89-99
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• 2008

GPCRs are large families of cell surface receptors that transmit signals through conformational changes upon ligand activation and an interaction with the heterotrimeric G-proteins. GPCRs regulate the cell-signaling pathways and participate in the regulation of physiological processes through the G-proteins defined by their ${\alpha}$ subunits. A family of 20 G protein-coupled receptors (GPCRs) that provide a large class of tractable drug targets for new anti-inflammatory drugs and, in certain instances, for the treatment of the inflammatory indications such as atherosclerosis, rhinitis, asthma, pulmonary disease and arthritis. In view of the important findings showing that $G{\alpha}_{12}/G{\alpha}_{13}$ regulate the various cellular processes such as actin-stress fiber formation, neurite retraction, platelet aggregation, gene induction, and apoptosis, we became interested in whether, after coupling to the activated GPCRs, the G-proteins and their downstream molecules might be involved in the pathologic processes of chronic inflammatory diseases (e.g., liver fibrosis). In this symposium, the possible link of the G-proteins with the pathophysiology will be discussed with the aim of finding potential new drug targets.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.408-412
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• 2008

FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1) in Arabidopsis are homologous proteins that perform opposite functions: FT is an activator of flowering, and TFL1 is a repressor. It was shown before that change of a single amino acid (His88) of TFL1 to the corresponding amino acid (Tyr) of FT is enough to convert the floral repressor to an activator. However, structural basis of the functional conversion has not been understood. In our molecular dynamics simulations on modified TFL1 proteins, a hydrogen bond present in native TFL1 between the His88 residue and a residue (Asp144) in a neighboring external loop became broken by change of His88 to Tyr. This breakage induced conformational change of the external loop whose structure was previously reported to be another key functional determinant. These findings reveal that the two important factors determining the functional specificities of the floral regulators, the key amino acid (His88) and the external loop, are correlated, and the key amino acid determines the functional specificity indirectly by affecting the conformation of the external loop.

• Molecules and Cells
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• v.43 no.8
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• pp.705-717
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• 2020

While the growth factors like insulin initiate a signaling cascade to induce conformational changes in the mechanistic target of rapamycin complex 1 (mTORC1), amino acids cause the complex to localize to the site of activation, the lysosome. The precise mechanism of how mTORC1 moves in and out of the lysosome is yet to be elucidated in detail. Here we report that microtubules and the motor protein KIF11 are required for the proper dissociation of mTORC1 from the lysosome upon amino acid scarcity. When microtubules are disrupted or KIF11 is knocked down, we observe that mTORC1 localizes to the lysosome even in the amino acid-starved situation where it should be dispersed in the cytosol, causing an elevated mTORC1 activity. Moreover, in the mechanistic perspective, we discover that mTORC1 interacts with KIF11 on the motor domain of KIF11, enabling the complex to move out of the lysosome along microtubules. Our results suggest not only a novel way of the regulation regarding amino acid availability for mTORC1, but also a new role of KIF11 and microtubules in mTOR signaling.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.864-869
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• 1995

Investigation of the structures of the gangliosides has proven to be very important in the understanding of their biological roles such as regulation of differentiation and growth of cells. We used nuclear magnetic resonance spectros-copy in order to investigate the structure of GA1. In order to do this, the assignment of spectra is a prerequisite. Since GA1 does not have polar sialic acid, the spectral overlap is severe. In order to solve this problem, we use 2D NMR spectroscopy and heteronuclear 1H/13C correlated spectroscopy in this study. Here, we report the complete assignment of the proton and the carbon spectra of the GA1 in DMSO-d6-D20 (98:2, v/v). These assignments will be useful for interpreting 1H and 13C NMR data from uncharacterized oligosaccharides and for determining the linkage position, the number of sugar rings, and the sequence of new ganglioside. Amide proton in ring Ⅲ shows many interring nOes and has intramolecular hydrogen bonding. This appears to be an important factor in tertiary folding of GA1. Based on this assignment, determination of three dimensional structure of GA1 will be carried out. Studies on the conformational properties of GA1 may lead to a better understanding of the molecular basis of its functions.

• YAKHAK HOEJI
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• v.56 no.6
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• pp.352-357
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• 2012

FGFR3 is a member of the fibroblast growth factor receptor family which interacts with fibroblast growth factors, setting in motion a cascade of downstream signals, ultimately influencing mitogenesis and differentiation. This particular family member binds acidic and basic fibroblast growth hormone and plays a role in bone development and maintenance. Accumulated evidence suggests that aberrant regulation of FGFR3 and genetic alterations are implicated in the development and progression of various cancers. Despite a high incidence of FGFR3 over-expression, no such investigation has been performed in hepatocellular carcinoma. Thus, we investigated genetic alterations of the FGFR3 gene in 73 cases of hepatocellular carcinoma by single-strand conformational polymorphism (SSCP) and sequencing. One silent mutation (A369A) was found in the extracellular domain of FGFR3, and one genetic alteration in the immunoglobulin-like III domain of FGFR3 appeared to be polymorphism. Taken together, we concluded that over-expression of FGFR3 in hepatocellular carcinoma is not associated with genetic alterations of FGFR3 gene, and we suggest that there could be another underlying mechanism of aberrant FGFR3 expression in hepatocellular carcinoma.