Biomedical subjects

Bonghee Lee

Publications and source records attributed to Bonghee Lee.

8 recordsLinked to original sources

PubMed2006

Suppression of Egr-1 transcription through targeting of the serum response factor by oncogenic H-Ras.

The transcription factor Egr-1 functions as a key regulator in cellular growth, differentiation, and apoptosis. The loss of Egr-1 expression is closely associated with tumor development, although the molecular mechanism behind the suppression of Egr-1 is largely unknown. In this report, we show that growth factor-induced transcriptional activation of Egr-1 gene is downregulated by chronic expression of oncogenic H-Ras in NIH3T3 fibroblasts. Our results demonstrate that phosphoinositide 3-kinase (PI3K) signaling is necessary for oncogenic H-Ras-mediated reduction of Egr-1 gene expression. Aberrant activation of PI3K signaling by oncogenic Ras decreased the level of serum response factor (SRF) protein through the acceleration of proteolysis, which resulted in decreased SRF binding to the serum response element (SRE) sites within the Egr-1 promoter, leading to the suppression of Egr-1 transcription. Inhibition of PI3K signaling restored the downregulation of SRF and Egr-1 expression caused by oncogenic Ras. Our findings suggest a novel signaling mechanism by which prolonged activation of oncogenic H-Ras can trigger the loss of tumor suppressor Egr-1 through the PI3K pathway in NIH3T3 fibroblast model cell lines.

3T3 Cells↗

PubMed2006

Alteration of the glutamate and GABA transporters in the hippocampus of the Niemann-Pick disease, type C mouse using proteomic analysis.

Niemann-Pick disease type C (NPC) is a fatal autosomal recessive cholesterol disorder characterized by severe progressive neurodegeneration. To unveil the mechanism of neurodegeneration, proteomic and morphological approaches were applied to the hippocampus in NPC -/- mouse. Two-DE was utilized to resolve the hippocampal protein expression profiles of 4- and 8-week-old NPC +/+ and -/- mice. Differentially expressed protein spots were identified by MALDI-TOF MS and database searching. At 4 weeks of age, there was no significant difference in protein profiles between NPC +/+ and -/- mice. However, at the age of 8 weeks, NPC +/+ and -/- mice showed marked difference in protein expressions. Among these, glutamate receptor 2 precursor was identified. The immunohistochemical study on neurotransporters showed that glial GABA transporter (GAT-3) increased in both 4- and 8-week-old NPC -/- mouse and glutamic acid decarboxylase (GAD-6) increased in 8-week-old NPC -/- mouse. Glial glutamate transporter, excitatory amino acids carrier-1 (EAAC1), decreased in 8-week-old NPC -/- mouse. In conclusion, our data may provide insight into the understanding of the basic mechanism through perturbation of protein networks and neurotransporter systems in a single gene knockout model of NPC disease.

Amino Acid Transport System X-AG↗

PubMed2006

Profiling human brain proteome by multi-dimensional separations coupled with MS.

In our initial attempt to analyze the human brain proteome, we applied multi-dimensional protein separation and identification techniques using a combination of sample fractionation, 1-D SDS-PAGE, and MS analysis. The complexity of human brain proteome requires multiple fractionation strategies to extend the range and total number of proteins identified. According to the method of Klose (Methods Mol. Biol. 1999, 112, 67), proteins of the temporal lobe of human brain were fractionated into (i) cytoplasmic and nucleoplasmic, (ii) membrane and other structural, and (iii) DNA-binding proteins. Each fraction was then separated by SDS-PAGE, and the resulting gel line was cut into approximately 50 bands. After trypsin digestion, the resulting peptides from each band were analyzed by RP-LC/ESI-MS/MS using an LTQ spectrometer. The SEQUEST search program, which searched against the IPI database, was used for peptide sequence identification, and peptide sequences were validated by reversed sequence database search and filtered by the Protein Hit Score. Ultimately, 1533 proteins could be detected from the human brain. We classified the identified proteins according to their distribution on cellular components. Among these proteins, 24% were membrane proteins. Our results show that the multiple separation strategy is effective for high-throughput characterization of proteins from complex proteomic mixtures.

Brain↗

PubMed2005

Substance P immunoreactive cell reductions in cerebral cortex of Niemann-Pick disease type C mouse.

Niemann-Pick disease type C (NPC) is characterized by progressive neurodegeneration and arises from mutations in the NPC1 gene. Cholesterol has received most attention in the pathogenesis of NPC, but normalizing lipid levels in humans or mouse does not prevent neurodegeneration. In NPC mouse, neuronal degeneration in the cerebellum is the most commonly detected change, and thus previous studies have tended to focus on the cerebellum, especially Purkinje cells. Although numerous peptides have been found in the mammalian central nervous system, little data on neurotransmitters in NPC are available, and information on neurotransmitter system abnormalities could explain the complex and characteristic deficits of NPC. Thus, we performed an immunohistochemical study on NPC mouse cortices to compare cell numbers exhibiting vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and substance P (SP) immunoreactivity. In terms of VIP and NPY-immunoreactive (ir) cell numbers in the cerebral cortex, SP-ir cells were significantly reduced by about 90% in NPC (-/-) versus NPC (+/+) mouse, and were also mildly decreased in frontal and parietal NPC (+/-) versus NPC (+/+) mouse cortex. This study demonstrates for the first time, reduced number of SP-ir cells in the NPC mouse cortex.

Animals↗

PubMed2005

Mapping the rat somatosensory pathway from the anterior cruciate ligament nerve endings to the cerebrum.

The anterior cruciate ligament (ACL) serves as the primary restraint to anterior tibial translation. In addition to this biomechanical function, the ACL appears to have a function in neuromuscular control. This hypothesis was formulated after the discovery of mechanoreceptors within the ACL. The full somatosensory pathway from the ACL to the cerebrum has yet to be elucidated. In order to map this sensory pathway, we conducted a viral trans-synaptic tracing experiment using the neurotropic pseudorabies virus (PRV). The pseudorabies virus was injected into the ACL of rats and allowed to replicate and spread trans-synaptically for 6-7 days. The brain and spinal cord of each sacrificed rat was then removed and processed immunohistochemically to detect the presence of PRV. PRV-immunoreactive neurons were found to be localized in several different regions from the spinal cord to the cerebrum. Four nuclei in the reticular formation of the brain stem demonstrated strong positive labeling: the mesencephalic reticular nucleus, magnocellular reticular nucleus, paragigantocellular reticular nucleus, and gigantocellular reticular nucleus. This finding suggests that the nerve endings of the rat ACL project into the cerebrum and that the reticular formation may play an important role in the afferent pathway of those nerve endings.

Afferent Pathways↗

PubMed2004

Immunohistochemical study of the distribution of neuronal voltage-gated calcium channels in the nNOS knock-out mouse cerebellum.

Nitric oxide (NO) participates in synaptic plasticity, neuronal development, and apoptosis. The involvement of NO and ionic calcium in synaptic plasticity imply that NO may exert an effect on Ca2+ channels. Therefore, we investigated changes in the expressions of calcium channel subunits (Cav1.2/alpha1C, Cav1.3/alpha(1D), Cav2.1/alpha1A, and Cav2.2/alpha1B) in nNOS knock-out (-/-) (nNOS((-/-))) mouse cerebellum using an immunohistochemical approach. We found that the immunoreactivities of the Cav1.2 and Cav1.3 subunits were reduced in the cell bodies of Purkinje cells in these mice and that the signal of the Cav1.2 subunit in neurons and of the Cav1.3 subunit in the neuropils of nNOS((-/-)) mice cerebellar nuclei were significantly down-regulated. We show, for the first time, that prolonged NO deficiency in the cerebellum may affect calcium channel protein expressions, especially, of the Cav1.2 and Cav1.3 subunits.

Animals↗

PubMed2003

Amyloid beta-protein (Abeta)1-40 protects neurons from damage induced by Abeta1-42 in culture and in rat brain.

Previously, we found that amyloid beta-protein (Abeta)1-42 exhibits neurotoxicity, while Abeta1-40 serves as an antioxidant molecule by quenching metal ions and inhibiting metal-mediated oxygen radical generation. Here, we show another neuroprotective action of nonamyloidogenic Abeta1-40 against Abeta1-42-induced neurotoxicity in culture and in vivo. Neuronal death was induced by Abeta1-42 at concentrations higher than 2 microm, which was prevented by concurrent treatment with Abeta1-40 in a dose-dependent manner. However, metal chelators did not prevent Abeta1-42-induced neuronal death. Circular dichroism spectroscopy showed that Abeta1-40 inhibited the beta-sheet transformation of Abeta1-42. Thioflavin-T assay and electron microscopy analysis revealed that Abeta1-40 inhibited the fibril formation of Abeta1-42. In contrast, Abeta1-16, Abeta25-35, and Abeta40-1 did not inhibit the fibril formation of Abeta1-42 nor prevent Abeta1-42-induced neuronal death. Abeta1-42 injection into the rat entorhinal cortex (EC) caused the hyperphosphorylation of tau on both sides of EC and hippocampus and increased the number of glial fibrillary acidic protein (GFAP)-positive astrocytes in the ipsilateral EC, which were prevented by the concurrent injection of Abeta1-40. These results indicate that Abeta1-40 protects neurons from Abeta1-42-induced neuronal damage in vitro and in vivo, not by sequestrating metals, but by inhibiting the beta-sheet transformation and fibril formation of Abeta1-42. Our data suggest a mechanism by which elevated Abeta1-42/Abeta1-40 ratio accelerates the development of Alzheimer's disease (AD) in familial AD.

Amyloid beta-Peptides↗

PubMed2003

A study on the central neural pathway of the heart, Nei-Kuan (EH-6) and Shen-Men (He-7) with neural tracer in rats.

The purpose of this morphological study was to investigate the relations between meridians, acupoints and viscera using neuroanatomical tracers. The labeled areas of the spinal ganglia, sympathetic chain ganglia, spinal cord and the brain projecting to the heart, Nei-Kuan (EH-6) and Shen-Men (He-7) were observed following injection of WGA-HRP and pseudorabies virus (PRV). The results were as follows. Overlapping bilaterally labeled ganglion areas after heart, Nei-Kuan (EH-6) or Shen-Men (He-7) injection of WGA-HRP were found in middle cervical, stellate and T4 sympathetic and T2-T6 spinal ganglia. In brain, labeled neurons from all three sites were found in the A1 noradrenalin cell group/C1 adrenalin cell group/caudoventrolateral reticular n., n. tractus solitarius, n. ambiguus, rostroventrolateral n., C3 adrenaline cell group, raphe obscurus n., raphe pallidus n., raphe magnus n., lateral paragigantocellular reticular n., locus coeruleus, subcoeruleus n., Kolliker-Fuse n., A5 cell group, central gray matter, paraventricular hypothalamic n. and arcuate hypothalamic n.. In conclusion, these morphological results suggest that the interrelationship of acupoints (Nei-Kuan and Shen-Men) and viscera (heart) may be related to the central autonomic centers of the spinal cord and brain.

Acupuncture Points↗