• BMB Reports
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• v.49 no.10
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• pp.542-547
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• 2016

Acid-sensing ion channels (ASICs) are proton-gated cation channels widely expressed in the nervous system. Proton sensing by ASICs has been known to mediate pain, mechanosensation, taste transduction, learning and memory, and fear. In this study, we investigated the differential subcellular localization of ASIC2a and ASIC3 in heterologous expression systems. While ASIC2a targeted the cell surface itself, ASIC3 was mostly accumulated in the ER with partial expression in the plasma membrane. However, when ASIC3 was co-expressed with ASIC2a, its surface expression was markedly increased. By using bimolecular fluorescence complementation (BiFC) assay, we confirmed the heteromeric association between ASIC2a and ASIC3 subunits. In addition, we observed that the ASIC2a-dependent surface trafficking of ASIC3 remarkably enhanced the sustained component of the currents. Our study demonstrates that ASIC2a can increase the membrane conductance sensitivity to protons by facilitating the surface expression of ASIC3 through herteromeric assembly.

• Journal of Applied Biological Chemistry
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• v.61 no.4
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• pp.379-382
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• 2018

Trafficking process of viral glycoprotein to cell surface results in the syncytium formation when baby hamster kidney (BHK) cells was infected by Newcastle disease virus (NDV). Rhus chinensis gall, well-known as a medicinal plant, inhibited not only syncytium formation, but also trafficking of glycoprotein, hemagglutinin-neuramidase (HN) to the cell-surface. Modification of viral glycoprotein is processed within the endoplasmic reticulum and golgi body during trafficking into surface. R. chinensis gall extracts showed the strong inhibitory activities ($IC_{50}$ $12.5{\mu}g/mL$) against ${\alpha}-glucosidase$, when compared with the ${\beta}-glucosidase$. And this inhibitory activities is increased by the samples in a dose-depedent pattern. These data showed that the extracts of R. chinensis gall inhibited the cell-surface expression of NDV-hemagglutinin-neuramidase glycoprotein without significantly affecting HN glycoprotein synthesis in NDV-infected BHK cells.

• The Korean Journal of Physiology and Pharmacology
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• v.28 no.5
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• pp.435-447
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• 2024

Secretory proteins, including plasma membrane proteins, are generally known to be transported to the plasma membrane through the endoplasmic reticulum-to-Golgi pathway. However, recent studies have revealed that several plasma membrane proteins and cytosolic proteins lacking a signal peptide are released via an unconventional protein secretion (UcPS) route, bypassing the Golgi during their journey to the cell surface. For instance, transmembrane proteins such as the misfolded cystic fibrosis transmembrane conductance regulator (CFTR) protein and the Spike protein of coronaviruses have been observed to reach the cell surface through a UcPS pathway under cell stress conditions. Nevertheless, the precise mechanisms of the UcPS pathway, particularly the molecular machineries involving cytosolic motor proteins, remain largely unknown. In this study, we identified specific kinesins, namely KIF1A and KIF5A, along with cytoplasmic dynein, as critical players in the unconventional trafficking of CFTR and the SARS-CoV-2 Spike protein. Gene silencing results demonstrated that knockdown of KIF1A, KIF5A, and the KIF-associated adaptor protein SKIP, FYCO1 significantly reduced the UcPS of △F508-CFTR. Moreover, gene silencing of these motor proteins impeded the UcPS of the SARS-CoV-2 Spike protein. However, the same gene silencing did not affect the conventional Golgi-mediated cell surface trafficking of wild-type CFTR and Spike protein. These findings suggest that specific motor proteins, distinct from those involved in conventional trafficking, are implicated in the stress-induced UcPS of transmembrane proteins.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.81-81
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• 2017

Nanotechnology is of great importance to molecular biology and medicine because life processes are maintained by the action of a series of molecular nanomachines in the cell machinery. Recent advances in nanoscale materials that possess emergent physical properties and molecular organization hold great promise to impact human health in the diagnostic and therapeutic arenas. In order to be effective, nanomaterials need to navigate the host biology and traffic to relevant biological structures, such as diseased or pathogenic cells. Moreover, nanoparticles intended for human administration must be designed to interact with, and ideally leverage, a living host environment. Inspired by nature, we use peptides to transfer biological trafficking properties to synthetic nanoparticles to achieve targeted delivery of payloads. In this talk, development of nanoscale materials will be presented with a particular focus on applications to three outstanding health problems: bacterial infection, cancer detection, and traumatic brain injury. A biodegradable nanoparticle carrying a peptide toxin trafficked to the bacterial surface has antimicrobial activity in a pneumonia model. Trafficking of a tumor-homing nanoprobes sensitively detects cancer via a high-contrast time-gated imaging system. A neuron-targeted nanoparticle carrying siRNA traffics to neuronal populations and silences genes in a model of traumatic brain injury. Unique combinations of material properties that can be achieved with nanomaterials provide new opportunities in translational nanomedicine. This framework for constructing nanomaterials that leverage bio-inspired molecules to traffic diagnostic and therapeutic payloads can contribute on better understanding of living systems to solve problems in human health.

• Food Science and Preservation
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• v.21 no.5
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• pp.735-739
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• 2014

Ephedra sinica Stapf, known as a medicinal plant, inhibited not only syncytium formation, but also trafficking of viral glycoprotein, hemagglutinin-neuramidase (HN) to the cell-surface. Trafficking of viral glycoprotein to the surface of infected-cells results in syncytium formation in Newcastle disease virus (NDV)-infected baby hamster kidney (BHK) cells. Viral glycoprotein in the infected-cell is processed within the endoplasmic reticulum during routing into surface. The processing of viral glycoprotein like a N-linked oligosaccharide trimming by ${\alpha}$-glucosidase in cell is necessary for virus infection. Methanol extracts showed inhibitory activities ($IC_{50}$ $15{\mu}g/mL$) against ${\alpha}$-glucosidase. This suggested that E. sinica extracts inhibited the cell-surface expression of NDV-HN glycoprotein without significantly affecting HN glycoprotein synthesis in NDV-infected BHK cells.

• Molecules and Cells
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• v.44 no.10
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• pp.758-769
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• 2021

Calcium homeostasis modulator 1 (CALHM1) is a membrane protein with four transmembrane helices that form an octameric ion channel with voltage-dependent activation. There are four conserved cysteine (Cys) residues in the extracellular domain that form two intramolecular disulfide bonds. We investigated the roles of C42-C127 and C44-C161 in human CALHM1 channel biogenesis and the ionic current (I_CALHM1). Replacing Cys with Ser or Ala abolished the membrane trafficking as well as I_CALHM1. Immunoblotting analysis revealed dithiothreitol-sensitive multimeric CALHM1, which was markedly reduced in C44S and C161S, but preserved in C42S and C127S. The mixed expression of C42S and wild-type did not show a dominant-negative effect. While the heteromeric assembly of CALHM1 and CALHM3 formed active ion channels, the co-expression of C42S and CALHM3 did not produce functional channels. Despite the critical structural role of the extracellular cysteine residues, a treatment with the membrane-impermeable reducing agent tris(2-carboxyethyl) phosphine (TCEP, 2 mM) did not affect I_CALHM1 for up to 30 min. Interestingly, incubation with TCEP (2 mM) for 2-6 h reduced both I_CALHM1 and the surface expression of CALHM1 in a time-dependent manner. We propose that the intramolecular disulfide bonds are essential for folding, oligomerization, trafficking and maintenance of CALHM1 in the plasma membrane, but dispensable for the voltage-dependent activation once expressed on the plasma membrane.

• Molecules and Cells
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• v.39 no.10
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• pp.762-767
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• 2016

Fasciclin II (FasII), the Drosophila ortholog of neural cell adhesion molecule (NCAM), plays a critical role in synaptic stabilization and plasticity. Although this molecule undergoes constitutive cycling at the synaptic membrane, how its membrane trafficking is regulated to ensure proper synaptic development remains poorly understood. In a genetic screen, we recovered a mutation in Drosophila mical-like that displays an increase in bouton numbers and a decrease in FasII levels at the neuromuscular junction (NMJ). Similar phenotypes were induced by presynaptic, but not postsynaptic, knockdown of mical-like expression. FasII trafficking assays revealed that the recycling of internalized FasII molecules to the cell surface was significantly impaired in mical-like-knockdown cells. Importantly, this defect correlated with an enhancement of endosomal sorting of FasII to the lysosomal degradation pathway. Similarly, synaptic vesicle exocytosis was also impaired in mical-like mutants. Together, our results identify Mical-like as a novel regulator of synaptic growth and FasII endocytic recycling.

• Journal of Microbiology and Biotechnology
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• v.21 no.3
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• pp.263-266
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• 2011

Methylelaiophylin isolated from Streptomyces melanosporofaciens was selected as an ${\alpha}$-glucosidase inhibitor with an $IC_{50}$ value of 10 ${\mu}M$. It showed mixed-type inhibition of ${\alpha}$-glucosidase with a $K_i$ value of 5.94 ${\mu}M$. In addition, methylelaiophylin inhibited the intracellular trafficking of hemagglutinin-neuramidase (HN), a glycoprotein of Newcastle disease virus (NDV), in baby hamster kidney (BHK) cells. Methylelaiophylin inhibited the cell surface expression of NDV-HN glycoprotein without significantly affecting HN glycoprotein synthesis in NDV-infected BHK cells.

• Molecules and Cells
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• v.41 no.7
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• pp.676-683
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• 2018

Cilia are highly specialized antennae-like organelles that extend from the cell surface and act as cell signaling hubs. Intraflagellar transport (IFT) is a specialized form of intracellular protein trafficking that is required for the assembly and maintenance of cilia. Because cilia are so important, mutations in several IFT components lead to human disease. Thus, clarifying the molecular functions of the IFT proteins is a high priority in cilia biology. Live imaging in various species and cellular preparations has proven to be an important technique in both the discovery of IFT and the mechanisms by which it functions. Live imaging of Drosophila cilia, however, has not yet been reported. Here, we have visualized the movement of IFT in Drosophila cilia using time-lapse live imaging for the first time. We found that NOMPB-GFP (IFT88) moves according to distinct parameters depending on the ciliary segment. NOMPB-GFP moves at a similar speed in proximal and distal cilia toward the tip (${\sim}0.45{\mu}m/s$). As it returns to the ciliary base, however, NOMPB-GFP moves at ${\sim}0.12{\mu}m/s$ in distal cilia, accelerating to ${\sim}0.70{\mu}m/s$ in proximal cilia. Furthermore, while live imaging NOMPB-GFP, we observed one of the IFT proteins required for retrograde movement, Oseg4 (WDR35), is also required for anterograde movement in distal cilia. We anticipate our time-lapse live imaging analysis technique in Drosophila cilia will be a good starting point for a more sophisticated analysis of IFT and its molecular mechanisms.

• Korean Journal of Food Science and Technology
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• v.46 no.2
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• pp.245-248
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• 2014

Trafficking of viral glycoproteins to the cell surface results in syncytium formation in baby hamster kidney (BHK) cells infected with Newcastle disease virus (NDV). An extract from the medicinal Areca catechu L plant inhibited not only syncytium formation, but also trafficking of the hemagglutinin-neuramidase (HN) glycoprotein to the cell-surface. The viral glycoprotein was processed within the endoplasmic reticulum during transit to the cell membrane. Fungal extracts showed inhibitory activities ($IC_{50}10{\mu}g/mL$) against ${\alpha}$-glucosidase. These results suggested that A. catechu L. extracts inhibited the cell-surface expression of NDV-HN glycoprotein without significantly affecting HN glycoprotein synthesis in NDV-infected BHK cells.