• The Korean Journal of Pharmacology
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• v.32 no.3
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• pp.311-321
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• 1996

Both $M_1$ and $M_2$ muscarinic receptors contain a triplet of amino acid residues consisting of leucine (L), tyrosine (Y) and threonine (T) at C-terminus ends of the second putative transmembrane domains. This triplet is repeated as LYT-LYT in $M_2$ receptors at the interface between the second transmembrane domain and the first extracellular loop. Interestingly, however, it is repeated in a transposed fashion (LYT-TYL) in the sequence of $M_1$ receptors. In this work, we employed site-directed mutagenesis to investigate the possible significance of this unique sequence diversity for determining the distinct differential cellular function at the two receptor subtypes. Mutation of the LYTTYL sequence of $M_1$ receptors to the corresponding $M_2$ receptor LYTLYT sequence did not result in a significant change in the binding affinity of the agonist carbachol. The reverse mutation at the $M_2$ receptor also did not modify agonist affinity. Surprisingly, the LYTLYT $M_1$ receptor mutant demonstrated markedly enhanced coupling to activation of phospholipase C without a change in its coupling to increased cyclic AMP formation. There was also an enhanced receptor sensitivity in transducing elevation of intracellular $Ca^{2+}$. On the other hand, the reverse $LYTLYT{\rightarrow}LYTTYL$ mutation in the $M_2$ receptor did not alter its coupling to inhibition of adenylate cyclase, but slightly enhanced its coupling to stimulation of phosphoinositide (PI) hydrolysis. Our data suggest that the LYTTYL/LYTLYT sequence differences between $M_1$ and $M_2$ muscarinic receptors are not important for specifying ligand binding and coupling of various subtypes of muscarinic receptors to different cellular signaling pathways although they might play a role in the modulation of muscarinic reseptor coupling to PI hydrolysis.

• Journal of Life Science
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• v.13 no.5
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• pp.596-603
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• 2003

Cells respond to an accumulation of unfolded proteins in the endoplasmic reticulum (ER) by increasing transcription of genes encoding molecular chaperones and folding enzymes. The information is transmitted from the ER lumen to the nucleus by intracellular signaling pathway, called the unfolded protein response (UPR). To obtain genes related to UPR from B. mori, the cDNA library was constructed with mRNA isolated from Bm5 cell lines in which N-glycosylation was inhibited by tunicamycin treatment. From the cDNA library, we selected 40 clones that differentially expressed when cells were treated with tunicamycin. Among these clones, we have isolated ATFC gene showing similarity with Hac1p, encoding a bZIP transcription factor of 5. cerevisiae. Basic-leucine zipper (bZIP) domain in amino acid sequences of ATFC shared homology with yeast Hac1p. Also, ATFC is up-regulated by accumulation of unfolded proteins in the ER through the treatment of ER stress drugs. Therefore we suggest that ATFC represents a major component of the putative transcription factor responsible for the UPR leading to the induction of ER-localized stress proteins.

• Development and Reproduction
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• v.2 no.1
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• pp.9-20
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• 1998

It has been wel known that phospholipase C(PLC) plays an important role in the intracellular signaling in a variety of cell types. However, involvement of PLC in mouse oocyte maturation and preimplantation embryo development remains unknown. The present study examined the expression patterns of the mouse PLC \beta 1 and \gamma 1 during oocyte maturatio and preimplantation embryo development study examined the expression patterns of the mouse PLC \beta 1 and \gamma 1 during oocyte maturation and preimplantation embryo development by the competitive reverse transcription-polymerase chain reaction (RT-PCR method). PLC \gamma 1 mRNA (0.1 fg) was readily detected in germinal vesicle (GV)-stage oocyte and its level was reduced as meiotic resumption proceeded. PLC-\beta 1 mRNA (<0.1 fg) as detected at low level at GV-stage oocytes and scarcely detected at germinal vescle breakdown (GVBD)-stage oocytes. After fertilization, both PLC \beta 1 and \gamma 1 mRNA levels began to increase at morula-stage embryos (0.2 fg) and were more prominent in blastocyst-stage embryos(1 fg). to elucidate the possible involvement of PLC via protein kinase C(PKC) pathway during oocyte maturation and preimplantation embryo development , the effects of sphingosine (PKC inhibitor), sn-$diC_{8}$(PKC activator) anc U73122 (PLC ingibitor) were examined. Treatment of GV-stage oocytes with sphingosine (20 \mu M) facilitated the meiotic resuption by 10-20 over the control within 1 h as judged by GVBD, whereas U73122 failed to show any significant effect. U73122 (10 \mu M) effectively blocked the compaction of morula, while sn-$diC_{8}$(50 \mu M). In summary, the present study shows that the mouse PLC \beta 1 and \gamma 1 are expressed in a developmental stage-specific manner and PLC-PKC pathway may be involved in early preimplantation embryo development.

• Journal of Life Science
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• v.14 no.4
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• pp.670-675
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• 2004

We have examined the effects of S-nitroso-N-acetylpenicillamine (SNAP), prostaglandin $E_2$ (PG $E_2$) and dibutric cyclic AMP (dbcAMP) on the methylation of interferon- ${\gamma}$ (IFN- ${\gamma}$ ) gene in human Jurkat T cells. The CpG dinucleotide which is critical for promoter function of IFN- ${\gamma}$ gene was methylated by treatment with SNAP, PG $E_2$ and dbcAMP, respectively. The DNA methylation induced by PG $E_2$ was suppressed by the addition of 2',5'-dideoxyadenosine (DDA), an inhibitor of adenylyl cyclase, but the suppression was not observed in SNAP treated cells. The NO production was not enhanced in PG $E_2$ or dbcAMP treated cells. The methylation induced by PG $E_2$ and dbcAMP was not suppressed by the addition of $N^{G}$-methyl-L-arginine (L-NMMA), NO synthase inhibitor. In conclusion, the inhibition of INF- ${\gamma}$ gene expression by PG $E_2$ was associated with the methylation of INF- ${\gamma}$ gene by elevation of intracellular cAMP in human Jurkat T cells. However, the methylation induced by PG $E_2$ might not be mediated through the NO production.rough the NO production.

• Journal of Life Science
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• v.27 no.10
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• pp.1191-1198
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• 2017

Vesicles and organelles are transported along microtubule and delivered to appropriate compartments in cells. The intracellular transport process is mediated by molecular motor proteins, kinesin, and dynein. Kinesin is a plus-end-directed molecular motor protein that moves the various cargoes along microtubule tracks. Kinesin 1 is first isolated from squid axoplasm is a dimer of two heavy chains (KHCs, also called KIF5s), each of which is associated with the light chain (KLC). KIF5s interact with many different binding proteins through their carboxyl (C)-terminal tail region, but their binding proteins have yet to be specified. To identify the interacting proteins for KIF5A, we performed the yeast two-hybrid screening and found a specific interaction with Ras-GTPase-activating protein (GAP) Src homology3 (SH3)-domain-binding protein 2 (G3BP2), which is involved in stress granule formation and mRNA-protein (mRNP) localization. G3BP2 bound to the C-terminal 73 amino acids of KIF5A but did not interact with the KIF5B, nor the KIF5C in the yeast two-hybrid assay. The arginine-glycine-glycine (RGG)/Gly-rich region domain of G3BP2 is a minimal binding domain for interaction with KIF5A. However, G3BP1 did not interact with KIF5A. When co-expressed in HEK-293T cells, G3BP2 co-localized with KIF5A and was co-immunoprecipitated with KIF5A. These results indicate that G3BP2, which was originally identified as a Ras-GAP SH3 domain-binding protein, is a protein that interacts with KIF5A.

• Journal of Life Science
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• v.25 no.6
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• pp.693-702
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• 2015

Blocking new blood-vessel formation (angiogenesis) is now recognized as a useful approach to the therapeutic treatment of many solid tumors. The best validated approach to date is to target the vascular endothelial growth-factor (VEGF) pathway, a key regulator of angiogenesis. Many natural products and extracts that contain a variety of chemopreventive compounds have been shown to suppress the development of malignancies through their anti-angiogenic properties. Phellodendron amurense, which is widely used in Korean traditional medicine, has been shown to possess antitumor, antimicrobial, and anti-inflammatory properties, among others. The present study investigated the effects of P. amurense hot-water extract (PAHWE) on angiogenesis, a key process in tumor growth, invasion, and metastasis. To investigate PAHWE’s anti-angiogenic properties, this study’s authors performed an analysis of angiogenesis and endothelial-cell proliferation, migration, invasion, and tube formation, as well as zymogram assays and the rat aortic ring-sprouting assay. PAHWE inhibited cell growth, mobility, and vessel formation in response to VEGF in vitro and ex vivo. Furthermore, it reduced VEGF-induced intracellular signaling events, such as the activation of matrix metalloproteinases (MMPs) -2 and -9. These results indicate that PAHWE’s anti-angiogenic properties might lead to the development of potential drugs for treating angiogenesis-associated diseases such as cancer.

• Journal of Life Science
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• v.32 no.2
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• pp.108-118
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• 2022

The subventricular zone (SVZ) in the brain contains neural stem cells (NSCs) that generate new neurons throughout one's lifetime. Many extracellular and intracellular factors that affect cell proliferation and neuronal differentiation of NSCs are already well-known. Recently, L-type calcium channels have been reported to regulate neural development and are present in NSCs, differentiating neuroblasts, and mature neurons in the SVZ. Nifedipine, a blocker of L-type calcium channels, has been long used as a therapeutic drug for hypertension. However, studies on the use of nifedipine to inhibit L-type calcium channels of NSCs are lacking. Herein, we treated NSCs cultured from mouse postnatal SVZ with nifedipine during neuronal differentiation. Nifedipine increased the number of Tuj1-positive neurons but did not significantly change the number of Olig2-positive oligodendrocytes. Nifedipine increased cell division during early differentiation, which was detected using the 5-ethynyl-2'-deoxyuridine incorporation assay and immunocytochemistry assessment by staining the cells with phosphorylated histone H3, a mitosis marker. Nifedipine increased the transcription of Dlx2, a neurogenic transcription factor, and the level of Mash1, a marker for early neurogenesis. In addition to nifedipine, verapamil, which is also an L-type calcium channel blocker, showed a slight increase in neurogenesis, but its statistical significance was very low. In contrast, pimozide, a T-type calcium channel blocker, did not affect neurogenesis, although T-type calcium channel genes Cav3.1, Cav3.2, and Cav3.3 were expressed. In summary, nifedipine might promote the neuronal fate of NSCs during early differentiation and calcium signaling through L-type calcium channels might be involved in neuronal differentiation, especially during the early stages of differentiation.