• Molecules and Cells
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• v.25 no.1
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• pp.99-104
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• 2008

Gangliosides, sialic acid-containing glycosphingolipids, are implicated in many neuronal diseases, but the precise molecular mechanisms underlying their pathological activities are poorly understood. Here we report that TLR2 participates in the initiation of ganglioside-triggered inflammatory signaling responses. Using FACS analysis and immunofluorescence microscopy, we found that gangliosides rapidly enhanced the cell surface expression of TLR2 in microglia, while reducing that of TLR4. The ganglioside-dependent increase of TLR2 expression was also observed at the messenger and protein levels. We also showed that gangliosides stimulate the interaction of TLR2 with Myd88, an adaptor for TLRs, and obtained evidence that lipid raft formation is closely associated with the ganglioside-induced activation of TLR2 and subsequent inflammatory signaling. These results collectively suggest that TLR2 contributes to the ability of gangliosides to cause inflammatory conditions in the brain.

• Journal of the Korean Chemical Society
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• v.68 no.1
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• pp.25-31
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• 2024

The p97 adenosine triphosphatase is a key player in protein homeostasis, responsible for unfolding ubiquitylated substrates. It engages with various adaptor proteins through its N-terminal domain, with the p97-p47 complex attracting particular attention for its involvement in membrane remodeling. Although the structures of p97 in complex with the Ubiquitin regulatory X (UBX) domain from various adaptors have been reported, the stoichiometry is conflicting. Here, we report the crystal structure of the p97 N-D1 hexamer in complex with the p47 UBX domain at a resolution of 2.7 Å. The structure reveals a stoichiometry of 6:6 between the p97 N-D1 and the p47 UBX domain. These findings provide valuable insights into the binding stoichiometry of p97 N-D1 and p47 UBX domain, which are crucial for understanding the role of p97 and adaptor proteins in cellular processes such as the ubiquitin-proteasome pathway, membrane fusion, and cell cycle regulation.

• Molecules and Cells
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• v.40 no.10
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• pp.706-713
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• 2017

Osteoclasts are bone-resorbing cells that are derived from hematopoietic precursor cells and require macrophage-colony stimulating factor and receptor activator of nuclear factor-${\kappa}B$ ligand (RANKL) for their survival, proliferation, differentiation, and activation. The binding of RANKL to its receptor RANK triggers osteoclast precursors to differentiate into osteoclasts. This process depends on RANKL-RANK signaling, which is temporally regulated by various adaptor proteins and kinases. Here we summarize the current understanding of the mechanisms that regulate RANK signaling during osteoclastogenesis. In the early stage, RANK signaling is mediated by recruiting adaptor molecules such as tumor necrosis factor receptorassociated factor 6 (TRAF6), which leads to the activation of mitogen-activated protein kinases (MAPKs), and the transcription factors nuclear factor-${\kappa}B$ (NF-${\kappa}B$) and activator protein-1 (AP-1). Activated NF-${\kappa}B$ induces the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), which is the key osteoclastogenesis regulator. In the intermediate stage of signaling, the co-stimulatory signal induces $Ca^{2+}$ oscillation via activated phospholipase $C{\gamma}2$ ($PLC{\gamma}2$) together with c-Fos/AP-1, wherein $Ca^{2+}$ signaling facilitates the robust production of NFATc1. In the late stage of osteoclastogenesis, NFATc1 translocates into the nucleus where it induces numerous osteoclast-specific target genes that are responsible for cell fusion and function.

• BMB Reports
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• v.46 no.9
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• pp.471-476
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• 2013

The PIDDosome, which is an oligomeric signaling complex composed of PIDD, RAIDD and caspase-2, can induce proximity-based dimerization and activation of caspase-2. In the PIDDosome assembly, the adaptor protein RAIDD interacts with PIDD and caspase-2 via CARD:CARD and DD:DD, respectively. To analyze the PIDDosome assembly, we purified all of the DD superfamily members and performed biochemical analyses. The results revealed that caspase-2 CARD is an insoluble protein that can be solubilized by its binding partner, RAIDD CARD, but not by full-length RAIDD; this indicates that full-length RAIDD in closed states cannot interact with caspase-2 CARD. Moreover, we found that caspase-2 CARD can be solubilized and interact with full-length RAIDD in the presence of PIDD DD, indicating that PIDD DD initially binds to RAIDD, after which caspase-2 can be recruited to RAIDD via a CARD:CARD interaction. Our study will be useful in determining the order of assembly of the PIDDosome.

• Molecules and Cells
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• v.41 no.1
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• pp.35-44
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• 2018

Mitochondria are responsible for supplying of most of the cell's energy via oxidative phosphorylation. However, mitochondria also can be deleterious for a cell because they are the primary source of reactive oxygen species, which are generated as a byproduct of respiration. Accumulation of mitochondrial and cellular oxidative damage leads to diverse pathologies. Thus, it is important to maintain a population of healthy and functional mitochondria for normal cellular metabolism. Eukaryotes have developed defense mechanisms to cope with aberrant mitochondria. Mitochondria autophagy (known as mitophagy) is thought to be one such process that selectively sequesters dysfunctional or excess mitochondria within double-membrane autophagosomes and carries them into lysosomes/vacuoles for degradation. The power of genetics and conservation of fundamental cellular processes among eukaryotes make yeast an excellent model for understanding the general mechanisms, regulation, and function of mitophagy. In budding yeast, a mitochondrial surface protein, Atg32, serves as a mitochondrial receptor for selective autophagy that interacts with Atg11, an adaptor protein for selective types of autophagy, and Atg8, a ubiquitin-like protein localized to the isolation membrane. Atg32 is regulated transcriptionally and post-translationally to control mitophagy. Moreover, because Atg32 is a mitophagy-specific protein, analysis of its deficient mutant enables investigation of the physiological roles of mitophagy. Here, we review recent progress in the understanding of the molecular mechanisms and functional importance of mitophagy in yeast at multiple levels.

• Journal of Gastric Cancer
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• v.3 no.2
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• pp.80-83
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• 2003

Purpose: Evidence exists that dysregulation of apoptosis is involved in the pathogenesis of cancer development. Fasassociated death domain (FADD) protein, an adaptor protein of death receptors, is a critical regulatory component of the extrinsic cell- death pathway that exerts its pro-apoptotic effect upon binding with death receptors. Expression of the FADD protein has not been reported in stomach cancer. The aim of this study was to explore the expression status of the FADD protein in stomach cancers. Materials and Methods: In the current study, we analyzed the expression of the FADD protein in 60 advanced stomach cancer by using immunohistochemistry and a tissue microarray approach. Results: Immunopositivity (defined as $\geq\30\%$) was observed for the FADD protein in 23 ($38\%$) of the 60 cancers. Normal gastric mucosal cells showed expression of the FADD protein. Conclusion: Taken together, these results indicate that decreased expression of the FADD protein is a frequent event in stomach cancers and suggest that to avoid apoptosis, stomach cancer cells in vivo may need loss of FADD expression, which might contribute to tumor development.

• Journal of Life Science
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• v.33 no.11
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• pp.868-875
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• 2023

Kinesin-1 is a motor protein identified as the first member of the kinesin superfamily (KIF), which plays a role in intracellular cargo transport by acting as microtubule-dependent motor proteins within cells. Kinesin-1 consists of two heavy chains (KHCs, also known as KIF5s) and two light chains (KLCs). The 93 amino acids in the carboxyl (C)-terminal tail region of KIF5A are not homologous to the C-terminal tail region of KIF5B or the C-terminal tail region of KIF5C. In this study, we used a yeast two-hybrid screen to identify the binding proteins that interacted with the C-terminal region of KIF5A. We found an association between KIF5A and CUE domain containing 2 (CUEDC2), which is proposed to function as an adaptor protein involved in ubiquitination pathways and protein trafficking. CUEDC2 bound to the C-terminal region of KIF5A and did not interact with KIF5B (the motor of kinesin-1), KIF3A (the motor of kinesin-2), or kinesin light chain 1 (KLC1). KIF5A specifically bound to the C-terminal region of CUEDC2. Furthermore, KIF5A did not interact with another isoform: CUEDC1. In addition, glutathione S-transferase (GST) pull-downs showed that KIF5A directly bound GST-CUEDC2 but did not interact with GST-CUEDC1 and GST alone. When myc-KIF5A and EGFP-CUEDC2 were co-expressed in HEK-293T cells, CUEDC2 co-immunoprecipitated with kinesin-1, and myc-KIF5A and FLAG-CUEDC2 colocalized in the cells. These results suggest that in intracellular cargo transport by kinesin-1, CUEDC2 serves as an adaptor protein connecting kinesin-1 and cargo by binding to KIF5A.

• BMB Reports
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• v.31 no.5
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• pp.468-474
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• 1998

Membrane depolarization in PC12 cells induces calcium influx via an L-type voltage-sensitive calcium channel (L-VSCC) and increases intracellular free calcium, which leads to tyrosine phosphorylation of epidermal growth factor (EGF) receptor and the associated adaptor protein, She. This activated EGF receptor complex then can activate mitogen-activated protein (MAP) kinase, as in nerve growth factor (NGF) receptor activation. In the present study, we investigated the role of EGF receptor in the signaling pathway initiated by membrane depolarization of PC12 cells. Prolonged membrane depolarization induced phosphorylation of extracellular signal-regulated kinase (ERK) within 1 min in undifferentiated PC12 cells. Pretreatment of PC12 cells with the calcium chelator EGTA abolished depolarization-stimulated ERK phosphorylation, but NGF-induced phosphorylation of ERK was not affected. The chronic treatment of phorbol ester, which down-regulated the activity of protein kinase C (PKC), did not affect the phosphorylation of ERK upon depolarization. In the presence of an inhibitor of EGF receptor, neither depolarization nor calcium ionophore increased the level of ERK phosphorylation. These data imply that the EGF receptor is functionally necessary to activate ERK and neurite outgrowth in response to the prolonged depolarization in PC12 cells, and also that PKC is apparently not involved in this signaling pathway.

• Korean Journal of Pharmacognosy
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• v.51 no.4
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• pp.317-324
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• 2020

Mast cells play a key role in IgE-mediated allergic response. We investigated whether Swertia pseudochinensis Hara extract (SPE) inhibits IgE-mediated allergic response in mast cells and an allergic animal model. Additionally, we explored SPE's mechanism of action in mast cells. Our results showed that SPE inhibited both antigen-stimulated degranulation and the production of TNF-α and IL-4 in bone marrow-derived mast cells (BMMCs) and rat basophilic leukemia (RBL)-2H3 cells. SPE also suppressed allergic response in IgE-mediated passive cutaneous anaphylaxis (PCA) in mice. As for the mechanism of action of SPE in mast cells, it inhibited the activation of Syk kinase, a critical signaling protein in the FcεRI-mediated signaling pathway, and also the activation of LAT, a downstream adaptor protein of Syk. We further observed the reduced activation of mitogen-activated protein (MAP) kinases (P38, ERK1/2, and JNK) and Akt in mast cells. Our results described for the first time that SPE has an anti-allergic effect by suppressing mast cells through the inhibition of Syk kinase. Therefore, SPE may be useful for the treatment of type I allergic diseases.

• Korean Journal of Poultry Science
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• v.46 no.1
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• pp.31-37
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• 2019

A chicken clathrin-associated adaptor protein $3-{\delta}$ subunit 2 (AP3S2) is a subunit of AP3, which is involved in cargo protein trafficking to target membrane with clathrin-coated vesicles. AP3S2 may play a role in virus entry into host cells through clathrin-dependent endocytosis. AP3S2 is also known to participate in metabolic disease developments of progressions, such as liver fibrosis with hepatitis C virus infection and type 2 diabetes mellitus. Chicken AP3S2 (chAP3S2) gene was originally identified as one of the differentially expressed genes (DEGs) in chicken kidney which was fed with different calcium doses. This study aims to characterize the molecular characteristics, gene expression patterns, and transcriptional regulation of chAP3S2 in response to the stimulation of Toll-like receptor 3 (TLR3) to understand the involvement of chAP3S2 in metabolic disease in chicken. As a result, the structure prediction of chAP3S2 gene revealed that the gene is highly conserved among AP3S2 orthologs from other species. Evolutionarily, it was suggested that chAP3S2 is relatively closely related to zebrafish, and fairly far from mammal AP3S2. The transcriptional profile revealed that chAP3S2 gene was highly expressed in chicken lung and spleen tissues, and under the stimulation of poly (I:C), the chAP3S2 expression was down-regulated in DF-1 cells (P<0.05). However, the presence of the transcriptional inhibitors, BAY 11-7085 (Bay) as an inhibitor for nuclear factor ${\kappa}B$ ($NF{\kappa}B$) or Tanshinone IIA (Tan-II) as an inhibitor for activated protein 1 (AP-1), did not affect the expressional level of chAP3S2, suggesting that these transcription factors might be dispensable for TLR3 mediated repression. These results suggest that chAP3S2 gene may play a significant role against viral infection and be involved in TLR3 signaling pathway. Further study about the transcriptional regulation of chAP3S2 in TLR3 pathways and the mechanism of chAP3S2 upon virus entry shall be needed.