• Biomedical Science Letters
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• v.13 no.3
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• pp.197-206
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• 2007

P2X receptors are membrane-bound ion channels that conduct $Na^+,\;K^+$, and $Ca^{2+}$ in response to ATP and its analogs. There are seven subunits identified so far ($P2X_1-P2X_7$). $P2X_2$ receptors are known to be expressed in a wide range of organs including brains and adrenal grands. PC12 cells are originated from adrenal grand and differentiated by nerve growth factor or pituitary adenylate cyclase activating poly peptide (PACAP). Previous studies indicate that $P2X_2$ receptor activation in PC12 cells couples to $Ca^{2+}-dependent$ release of catecholamine and ATP. It is known that acidic pH potentiates ATP currents at $P2X_2$ receptors. This leads to a hypothesis that $P2X_2$ receptors may play an important role in PC12 cell differentiation, one of the characteristics of which is neurite outgrowth, induced by the hormones under lower pH. In the present study, we isolated several clones which potentiate neurite outgrowth by PACAP in acidic pH (6.8), but not in alkaline pH (7.6). RT-PCR and electrophysiology data indicate that these clones express only functional $P2X_2$ receptors in the absence or presence of PACAP for 3 days. Potentiation of neurite outgrowth resulted from PACAP (100 nM) in acidic pH is inhibited by the two P2X receptor antagonists, suramin and PPADS ($100\;{\mu}M)$ each), and exogenous exprerssion of ATP-binding mutant $P2X_2$ receptor subunit ($P2X_2[K69A]$). However, acid sensing ion channels (ASICs) are not involved in PACAP-induced neurite outgrowth potentiation in lower pH since treatments of an inhibitor of ASICs, amyloride ($10\;{\mu}M$), did not give any effects to neurite extension. The vesicular proton pump ($H^+-ATPase$) inhibitor, bafilomycin (100 nM), reduced neurite extension indicating that ATP release resulted from $P2X_2$ receptor activation in PC12 cells is needed for neurite outgrowth. These were confirmed by activation of mitogen activated protein kinases, such as ERKs and p38. These results suggest roles of ATP and $P2X_2$ receptors in hormone-induced cell differentiation or neuronal synaptogenesis in local acidic environments.

• BMB Reports
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• v.41 no.4
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• pp.287-293
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• 2008

In a yeast two-hybrid screen, we identified the microtubule-destabilizing protein SCG10 as a potential effector protein of $BRI_3$. The association was verified using GST pull-down, Co-IP, and their perinuclear co-localization. The analysis of in vitro microtubule polymerization/depolymerization showed that the binding of $BRI_3$ to SCG10 effectively blocked the ability of SCG10 to induce microtubule disassembly, as determined by turbidimetric assays. In intact PC12 cells, $BRI_3$ exhibited the ability to stabilize the microtubule network and attenuate the microtubule-destabilizing activity of SCG10. Furthermore, co-expression of $BRI_3$ with SCG10 attenuated SCG10-mediated PC12 cell neurite outgrowth induced by NGF. These results identify a novel connection between a neuron-specific BRI protein and the cytoskeletal network, suggesting possible roles of BRI3 in the process of neuronal differentiation.

• Korean Journal of Biological Psychiatry
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• v.16 no.1
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• pp.5-14
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• 2009

Objectives : Most of the mechanisms reported for antidepressant drugs are the enhancement of neurite outgrowth and neuronal survival in the rat hippocampus. Neural cell adhesion molecule 140(NCAM140) has been implicated as having a role in cell-cell adhesion, neurite outgrowth, and synaptic plasticity. In this report, we have performed to elucidate a correlation among chronic antidepressant treatments, NCAM140 expression, and activation of phosphorylated cyclicAMP responsive element binding protein(pCREB) which is a downstream molecule of NCAM140-mediated intracellular signaling pathway in the rat hippocampus. Methods : Fluoxetine(10mg/kg) was injected acutely(daily injection for 5days) or chronically(daily injection for 14days) in adult rats. RNA and protein were extracted from the rat hippocampus, respectively. Real-time RT-PCR was performed to analyze the expression pattern of NCAM140 gene and western blot analyses for the activation of the phosphorylation ratio of CREB. Results : Chronic fluoxetine treatments increased NCAM140 expression 1.3 times higher than control in rat hippocampus. pCREB immunoreactivity in the rat hippocampus with chronic fluoxetine treatment was increased 4.0 times higher than that of control. Conclusion : Chronic fluoxetine treatment increased NCAM140 expression and pCREB activity in the rat hippocampus. Our data suggest that NCAM140 and pCREB may play a role in the clinical efficacy of antidepressants promoting the neurite outgrowth and neuronal survival.

• Journal of Life Science
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• v.21 no.9
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• pp.1234-1243
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• 2011

Liriope platyphylla has been used in oriental medicine as an effective medical plant to improve symptoms of cough, sputum production, neurodegenerative disorders, obesity and diabetes for long time. In order to investigate the effects of novel extracts on nerve growth factors (NGF)-stimulated neuritic outgrowth, the alteration of NGF expression and NGF receptor signaling pathway were detected in neuroblastoma cells and C57BL/6 mice. Of a total of 13 novel extracts, 4 extracts (LP-E, LP-M, LP-M50, LP2E17PJ) showed high viability on MTT assay. Also, all of these extracts induced NGF secretion and NGF mRNA expression in neuroblastoma cells. However, the NGF-induced neuritic outgrowth from PC12 cells was only stimulated by LP-E, LP-M and LP-M50. Furthermore, we selected LP-M as a best candidate, based on method and amounts of extraction, in order to verify its effect in mice. C57BL/6 mice were treated with 50 mg/kg of LP-M for 2 weeks and the effects on NGF regulation were analyzed with various methods. The expression of NGF mRNA was significantly increased in LP-M treated mice compared to vehicle treated mice. Also, the signaling pathway of p75NTR was inhibited in the cortex by LP-M treatment, with no change in the hippocampus of brain. However, the signaling pathway of TrkA was dramatically activated in only hippocampus via LP-M treatment. Therefore, these results suggest that the novel four extracts of L. platyphylla may contribute to the regulation of NGF expression and secretion in neuronal cells. LP-M was especially considered to be an excellent candidate for a neurodegenerative disease-therapeutic drug.

• Journal of Microbiology and Biotechnology
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• v.17 no.12
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• pp.2033-2041
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• 2007

For many years, it has been demonstrated that neurotrophins regulate the adult nervous system, implicating their potential as therapeutic agents for the treatment of neurodegenerative diseases. We generated adenoviral vectors encoding brain-derived neutotrophin factor (BDNF) and neurotrophin-3 (NT3) and tested either separately or together for the ability to induce differentiation of neuronal precursor cells with two different origins. Separate transduction of adenovirus delivering BDNF (BDNF-Ad) or NT3 (NT3-Ad) induced the neuronal differentiation in hippocampal and cortical precursor cells. NT3-Ad infected cells extended short neurites, whereas BDNF-Ad infected cells had longer neurites. In the early differentiation of hippocampal precursor cells, simultaneous infection of BDNF-Ad and NT3-Ad promoted further differentiation and neurite elongation compared with the separate infection of each virus. In contrast, simultaneous infection did not show the synergistic effect in the cortical precursor cells, suggesting that the neurotrophins play distinct roles in different regions of the brain. However, the numbers of neurites and spines per differentiated cells were markedly increased in cortical as well as hippocampal precursor cells, indicating the promotion of efficient neurite elongation and formation of dendritic spine, when BDNF-Ad and NT3-Ad were co-infected. These results suggest more studies in the effect of a combinatorial use of neurotrophins on different sites of brain need to be carried out to develop gene therapy protocols for neurodegenerative diseases.

• Journal of Life Science
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• v.31 no.9
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• pp.806-817
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• 2021

Increasing evidence suggests that depression is associated with impairments in neural plasticity. Sirtuin 1 plays an important role in neural plasticity, and the activation of mechanistic target of rapamycin complex 1 (mTORC1) signaling is known to improve neural plasticity. In this study, we aimed to determine whether sirtuin 1 affects dendrite outgrowth and spine formation through mTORC1 signaling. Resveratrol (sirtuin 1 activator; 1 and 10 μM) and sirtinol (sirtuin 1 inhibitor; 1 and 10 μM) were treated in primary cortical culture with and without dexamethasone (500 μM). Levels of sirtuin 1, phospho-extracellular signal regulated protein kinase 1/2 (ERK1/2), phospho-mTORC1, and phospho-p70 ribosomal protein S6 kinase (p70S6K) were evaluated using Western blot analysis. Dendritic outgrowth and spine density were assessed using immunostaining. Resveratrol significantly increased levels of sirtuin 1 expression and phosphorylation of ERK1/2 (a downstream target of sirtuin 1), mTORC1, and p70S6K (a downstream target of mTORC1) in a concentration-dependent manner under dexamethasone conditions. Resveratrol also significantly increased dendritic outgrowth and spine density. Conversely, sirtinol significantly decreased levels of sirtuin 1 expression and phosphorylation of ERK1/2, mTORC1, and p70S6K in a concentration-dependent manner under normal conditions. Moreover, sirtinol significantly decreased dendritic outgrowth and spine density. Consistent with the results of sirtinol, sirtuin 1 knockdown using sirtuin 1 siRNA transfection significantly decreased dendritic outgrowth and spine density as well as phosphorylation levels of ERK1/2 and mTORC1. These data suggest that sirtuin 1 enhances dendritic outgrowth and spine density by activating mTORC1 signaling.

• Biomedical Science Letters
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• v.15 no.4
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• pp.327-333
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• 2009

Heterotrimeric GTP binding proteins, G-proteins, mediate signal transduction generated by neurotransmitters and hormones. Among G-proteins, Go proteins are the most abundant in brain and classified as a member of Gi family. Ras-like protein in all tissues (Rit), one of the small GTPases, is a member of a Ras superfamily and identified as an important regulator of neuronal differentiation and cell transformation. Recently, we have reported that Rit functioned as a candidate downstream effector for alpha subunit of Go proteins ($Go{\alpha}$) and regulated neurite outgrowth triggered by $Go{\alpha}$ activation. In this study, we showed that the GTPase domain of $Go{\alpha}$ contributed to the direct interaction with Rit. We also demonstrated that $Go{\alpha}$ could lead to an increase of Rit activity suggesting that Rit play a role as a downstream effector of $Go{\alpha}$.

• Journal of Haehwa Medicine
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• v.25 no.1
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• pp.37-44
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• 2016

Objectives : This study was designed to investigate the effect of Gamishinchubogun-tang (JiaweiShenzhuibujian-tang; GSB) on regeneration of PC12 cells. Methods : PC12 cells have been used extensively as a model for studying the cellular and molecular effects of neuronal cells. In order to check the effect of GSB on the regeneration of PC12 cells, the morphological change of PC12 cells were observed comparatively in GSB group and control group. Results : The significant changes in neurite length of PC12 cells have been observed on GSB group. In proportion to the concentration of GSB it was observed an increase in neurite outgrowth. Conclusions : This study confirmed that GSB made a significant influence on regeneration of PC12 cells.

• Clinical and Experimental Pediatrics
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• v.54 no.6
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• pp.241-245
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• 2011

Tuberous sclerosis complex (TSC) is a genetic multisystem disorder that results from mutations in the TSC1 or TSC2 genes, and is associated with hamartomas in several organs, including subependymal giant cell tumors. The neurological manifestations of TSC are particularly challenging and include infantile spasms, intractable epilepsy, cognitive disabilities, and autism. The TSC1- and TSC2-encoded proteins modulate cell function via the mammalian target of rapamycin (mTOR) signaling cascade, and are key factors in the regulation of cell growth and proliferation. The mTOR pathway provides an intersection for an intricate network of protein cascades that respond to cellular nutrition, energy levels, and growth factor stimulation. In the brain, TSC1 and TSC2 have been implicated in cell body size, dendritic arborization, axonal outgrowth and targeting, neuronal migration, cortical lamination, and spine formation. The mTOR pathway represents a logical candidate for drug targeting, because mTOR regulates multiple cellular functions that may contribute to epileptogenesis, including protein synthesis, cell growth and proliferation, and synaptic plasticity. Antagonism of the mTOR pathway with rapamycin and related compounds may provide new therapeutic options for TSC patients.

• Molecules and Cells
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• v.41 no.7
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• pp.622-630
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• 2018

Leukocyte common antigen-related protein tyrosine phosphatases (LAR-RPTPs) are cellular receptors of heparan sulfate (HS) and chondroitin sulfate (CS) proteoglycans that regulate neurite outgrowth and neuronal regeneration. LAR-RPTPs have also received particular attention as the major presynaptic hubs for synapse organization through selective binding to numerous postsynaptic adhesion partners. Recent structural studies on LAR-RPTP-mediated trans-synaptic adhesion complexes have provided significant insight into the molecular basis of their specific interactions, the key codes for their selective binding, as well as the higher-order clustering of LAR-RPTPs necessary for synaptogenic activity. In this review, we summarize the structures of LAR-RPTPs in complex with various postsynaptic adhesion partners and discuss the molecular mechanisms underlying LAR-RPTP-mediated synaptogenesis.