• Molecules and Cells
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• v.25 no.1
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• pp.124-130
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• 2008

Astrocyte ion channels participate in ionic homeostasis in the brain. Inward rectifying potassium channels (Kir channels) in astrocytes have been particularly implicated in $K^+$ homeostasis because of their high open probability at resting potential and their increased conductance at high concentrations of extracellular $K^+$. We examined the expression of the Kir2.1 subunit, one of the Kir channel subunits, in the mouse brain by immunohistochemistry. Kir2.1 channels were widely distributed throughout the brain, with high expression in the olfactory bulb and the cerebellum. Interestingly, they were abundantly expressed in astrocytes of the olfactory bulb, while astrocytes in other brain regions including the hippocampus did not show any detectable expression. However, Kir2.1 channel-expressing cells were dramatically increased in the hippocampus by kainic acid-induced seizure and the cells were glial fibrillary acidic protein (GFAP)-positive, which confirms that astrocytes in the hippocampus express Kir2.1 channels under pathological conditions. Our results imply that Kir2.1 channels in astrocyte may be involved in buffering $K^+$ against accumulated extracellular $K^+$ caused by neuronal hyperexcitability under phathophysiological conditions.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.6
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• pp.565-574
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• 2021

Astrocytes are activated in response to brain damage. Here, we found that expression of Kir4.1, a major potassium channel in astrocytes, is increased in activated astrocytes in the injured brain together with upregulation of the neural stem cell markers, Sox2 and Nestin. Expression of Kir4.1 was also increased together with that of Nestin and Sox2 in neurospheres formed from dissociated P7 mouse brains. Using the Kir4.1 blocker BaCl₂ to determine whether Kir4.1 is involved in acquisition of stemness, we found that inhibition of Kir4.1 activity caused a concentration-dependent increase in sphere size and Sox2 levels, but had little effect on Nestin levels. Moreover, induction of differentiation of cultured neural stem cells by withdrawing epidermal growth factor and fibroblast growth factor from the culture medium caused a sharp initial increase in Kir4.1 expression followed by a decrease, whereas Sox2 and Nestin levels continuously decreased. Inhibition of Kir4.1 had no effect on expression levels of Sox2 or Nestin, or the astrocyte and neuron markers glial fibrillary acidic protein and β-tubulin III, respectively. Taken together, these results indicate that Kir4.1 may control gain of stemness but not differentiation of stem cells.

• IMMUNE NETWORK
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• v.6 no.2
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• pp.67-75
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• 2006

Background: Cytotoxic function of killer cells is inhibited by specific recognition of class I MHC molecules on target cells by inhibitory killer Ig-like receptors (KIR) expressed on NK cells and some cytotoxic T cells. The inhibitory effect of KIR is accomplished by recruitment of SH2-containing protein tyrosine phosphatase (SHP) to the phosphotyrosine residues in the cytoplasmic tail. Methods: By in vitro coprecipitation experiments and transfection analysis, we investigated the association of KIR with an adaptor protein Shc in Jurkat T cells. Results: The cytoplasmic tail of KIR appeared to associate with an adaptor protein Shc in Jurkat T celilysates. Similar in vitro experiments showed that phosphorylated KIR cytoplasmic tail bound SHP-1 and Shc in Jurkat T cell lysates. The association of KIR with Shc was further confirmed by transfection analysis in 293T cells. Interestingly, however, Shc appeared to be replaced by SHP-2 upon engagement of KIR in 293T cells. Conclusion: Our data indicate that KIR associate with an adaptor protein Shc in Jurkat T cells, and suggest that KIR might have an additional role which is mediated by this adaptor protein.

• IMMUNE NETWORK
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• v.5 no.3
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• pp.179-185
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• 2005

Background: Psoriasis is a multifactorial autoimmune skin disease with a pathogenesis that has remained obscure. Recently, T cells bearing natural killer receptors (NKRs) were precisely and strongly targeted as new putative pathogenic immunocytes in psoriasis. Among NKRs, killer cell immunoglobulin-like receptor (KIR) is the major molecule recognizing HLA class I allotypes and might be closely related to psoriasis. Methods: To investigate the association of KIR genotype and patients with psoriasis in Korean, we defined the 14 KIR genotypes in 96 patients with psoriasis and 86 healthy controls using PCR-SSP methods. Results: The frequencies of KIR2DS4 and KIR3DL1 were significantly decreased in psoriasis compared with controls (RR=0.21, p<0.02). When patients were divided into two subgroups at the age of onset, type I (<30 years) and type II ($({\geq}30$ years) respectively, these phenomena were similarly observed independent of groups divided (type I: RR=0.26, p<0.005; type II: RR=0.14, p<0.0006). When the patients were divided into subgroups according to the age of onset and family history, the frequencies of KIR2DS4, KIR3DL1, and KIR2DS3 were significantly decreased in type I compared with type II psoriasis (3DL1, 2DS4: p<0.004; 2DS3: p<0.04) and were significantly decreased in psoriasis without family history compared to with family history (3DL1, 2DS4: p<0.007; 2DS3: p<0.05). The frequency of haplotype combination BB was significantly increased in psoriasis compared with controls (RR=2.74, p<0.009). Conclusion: These results suggest that KIR genotype is a factor for the occurrence and development of psoriasis and in future how combinations of HLA and KIR genes influence psoriasis needs to be defined.

• Clinical and Experimental Reproductive Medicine
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• v.47 no.2
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• pp.122-129
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• 2020

Objective: The survival of a semi-allogeneic fetus depends on several immunological mechanisms, and it has been suggested that recurrent pregnancy loss (RPL) could develop as a result of one or more immunological abnormalities. Methods: Compatibility between partners for human leukocyte antigen (HLA) genotypes and the relationships between maternal killer-cell immunoglobulin-like receptor (KIR) and paternal HLA-Bw4/Bw6 and HLA-C1/C2 supra-groups were investigated in 25 couples with RPL in comparison to healthy couples with children. HLA and KIR genotyping was performed using polymerase chain reaction with sequence-specific primers and/or sequence-specific oligonucleotides. Results: HLA class I incompatibility between partners, especially in HLA-B alleles, was more common in the RPL group (p= 0.01). HLA-C2 homozygosity was more frequent in the male partners of RPL couples than in other groups (p= 0.03). The KIR2DL5 gene frequency was significantly higher in both the female and male partners of RPL couples, whereas the KIR2DS3 gene frequency in male partners of RPL couples was significantly reduced (p= 0.03). The presence of KIR2DL3 in women with RPL was correlated with the presence of HLA-C2 alleles in their spouses (p= 0.03). Conclusion: Our data from a Turkish population suggest that male HLA-C2 homozygosity may play an important role in RPL. Additionally, an incidental match between male HLA-C2 and female HLA-C1 ligand KIR receptors might perturb the balance between activatory and inhibitory KIR-ligand interactions during pregnancy in couples affected by RPL. The roles of orphan KIR2DL5 and orphan KIR2DS3 in RPL remain obscure.

• Genomics & Informatics
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• v.12 no.4
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• pp.283-288
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• 2014

Among all serious diseases globally, diabetes (type 1 and type 2) still poses a major challenge to the world population. Several target proteins have been identified, and the etiology causing diabetes has been reasonably well studied. But, there is still a gap in deciding on the choice of a drug, especially when the target is mutated. Mutations in the KCNJ11 gene, encoding the kir6.2 channel, are reported to be associated with congenital hyperinsulinism, having a major impact in causing type 1 diabetes, and due to the lack of its 3D structure, an attempt has been made to predict the structure of kir6.2, applying fold recognition methods. The current work is intended to investigate the affinity of four phytochemicals namely, curcumin (Curcuma longa), genistein (Genista tinctoria), piperine (Piper nigrum), and pterostilbene (Vitis vinifera) in a normal as well as in a mutant kir6.2 model by adopting a molecular docking methodology. The phytochemicals were docked in both wild and mutated kir6.2 models in two rounds: blind docking followed by ATP-binding pocket-specific docking. From the binding pockets, the common interacting amino acid residues participating strongly within the binding pocket were identified and compared. From the study, we conclude that these phytochemicals have strong affinity in both the normal and mutant kir6.2 model. This work would be helpful for further study of the phytochemicals above for the treatment of type 1 diabetes by targeting the kir6.2 channel.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.4
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• pp.199-205
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• 2006

The functional expression of potassium $(K^+)$ channels has electrophysiologically been studied in bone cells from several species, however, their identity and regulation of gene expressions in bone cells are not well known. In the present study, to investigate how $K^+$ channel expressions are regulated by estrogen, we measured changes of transcript levels of various $Ca^{2+}$-activated ($K_{Ca}$) and ATP-sensitive $K^+$ channels in rat osteoblastic ROS 17/2.8 cells after treatment with estrogen. Application of 17${\beta}$-estradiol $(E_2)$ for 24 h and 48 h increased mRNA and protein expressions of inwardly rectifying $K^+$ channel (Kir) 6.2 and type 2 small conductance $K_{Ca}$ channel (SK2), respectively. Combined treatment of cells with 17${\beta}-E_2$ and ICI 182,780, a pure antiestrogen, suppressed 17${\beta}-E_2$-induced alterations of SK2 and Kir6.2 mRNA levels. In addition, treatment of cells with U0126, a specific inhibitor of extracellular receptor kinases (ERK)1/2, and SP600125, a specific inhibitor of c-jun N-terminal kinase (JNK) blocked the enhancing effects of 17${\beta}-E_2$ on SK2 and Kir6.2 protein expressions. On the other hand, blocking of p38 mitogen-activated protein kinase had no effect. Taken together, these results indicate that 17${\beta}-E_2$ modulates SK2 and Kir6.2 expressions through the estrogen receptor, involving ERK1/2 and JNK activations.

• 대한약리학회:학술대회논문집
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• 2006.10a
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• pp.115.1-115.1
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• 2006

• Journal of The Korean Society of Inherited Metabolic disease
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• v.6 no.1
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• pp.52-57
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• 2006

Permanent neonatal diabetes(PND) is a rare form of diabetes characterized by insulin-requiring hyperglycemia that is diagnosed within the first 3 months of life. In most cases, the causes are not known. Recently, mutations in the gene KCNJ11 encoding the Kir6.2 subunit of the ATP-sensitive K+ charmel have been described in patients with PND. We report a child with PND due to a lysine-to-arginine substitution at position 170(K170R) of gene encoding Kir6.2 Our patient was diagnosed at 7 weeks of age and had been treated with subcutaneous insulin for 6.5 years. Recently, our patient has been changed from subcutaneous insulin to oral glibenclamide therapy at a daily dose of 7.5 mg 3 times a day(0.9 mg/kg/day) at the age of 6.5 years. Before glibenclamide therapy, c-peptide level was 0.1 ng/ml(normal 1.0-3.5 ng/ml) and hemoglobin HbA1c level was 7.8%(normal <6%). After 6 days of treatment, her c-peptide and insulin levels were 2.3 ng/ml and $9.6{\mu}U/ml$(normal $5-25{\mu}U/ml$), respectively. After 1 month later, the insulin and c-peptide levels were in the nonnal range without any episodes of hyper- or hypoglycemia. This case demonstrated that oral sulfonylurea may be the treatment of choice in PND patients with KCNJ11 mutation even at a young age.

• Journal of Life Science
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• v.20 no.3
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• pp.457-461
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• 2010

Familial hypokalemic periodic paralysis (HOKPP) is an autosomal dominant disorder characterized by reversible flaccid paralysis and intermittent hypokalemia. Although it has been reported that decreased activity in the $K_{ATP}$ channels of the skeletal muscle cell membrane plays a role in the pathogenesis of HOKPP, a clear mechanism has not yet been established. This study aimed to investigate the molecular biological mechanism underlying the decreased activity of $K_{ATP}$ channels in the skeletal muscles of familial HOKPP patients by studying the levels of the $K_{ATP}$ channel subunit Kir6.2. We found that when cells obtained from healthy individuals (normal cells) and HOKPP patients (patient cells) were treated with 4 mM potassium buffer, there was no quantitative change in the KCNJ11 mRNA levels and no difference in the Kir6.2 protein expression in the cytosol and cell membrane. On the other hand, when 1 mM potassium buffer was used, normal cells showed decreased expression of KCNJ11 mRNA as well as decreased expression of Kir6.2 protein in the cell membrane. However, patient cells treated with the same buffer showed no quantitative change in the levels of KCNJ11 mRNA or in the levels of Kir6.2 protein in the cytosol and cell membrane. Thus, in HOKPP patients, the Kir6.2 protein cannot be transported from the cell membrane to the cytosol, leading to closure of the $K_{ATP}$ channels, induction of depolarization, and subsequently, to the paralytic symptoms observed in the patient. Our findings thus provide new insights into the pathogenesis of HOKPP.