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Chemical Modification of Brain Glutamate Dehydrogenase Isoproteins with Phenylglyoxal
Ahn, Jee-Yin,Cho, Eun-Hee,Lee, Kil-Soo,Choi, Soo-Young,Cho, Sung-Woo Korean Society for Biochemistry and Molecular Biol 1999 Journal of biochemistry and molecular biology Vol.32 No.5
Incubation of two types of glutamate dehydrogenase isoproteins from bovine brain with the arginine-specific dicarbonyl reagent phenylglyoxal resulted in a biphasic loss of enzyme activity. Reaction of the glutamate dehydrogenase isoproteins with phenylglyoxal caused a rapid loss of 53~62% of the enzyme activities and modification of two residues of arginine per enzyme subunit. Prolonged incubation of the glutamate dehydrogenase isoproteins with phenylglyoxal resulted in the modification of an additional four residues of arginine per enzyme subunit without further loss of the residual activities. Partial protection against inactivation was provided by the coenzyme NADH or substrate 2-oxoglutarate. The most marked decrease in the rate of inactivation was observed by the combined addition of NADH and 2-oxoglutarate, suggesting that the first two modified arginine residues are in the vicinity of the catalytic site. However, inactivation of the glutamate dehydrogenase isoproteins by phenylglyoxal appears to be partial with approximately 40% activity remained after an extended reaction time with excess reagent, suggesting that the modified arginine residues may not be directly involved in catalysis. The lack of complete protection by substrates also suggest the possibility that the modified arginine residues are not directly involved at the active site, and the partial loss of activity by the modification of arginine residues may be due to a conformational change. There were no significant differences between the two glutamate dehydrogenase isoproteins in sensitivities to inactivation by phenylglyoxal, indicating that the microenvironmental structures of the glutamate dehydrogenase isoproteins are very similar to each other.
Le Xuan Nguyen, Truong,Ahn, Jee-Yin Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.6
Src homology (SH) domains of phospholipase C-$\gamma1$ (PLC-$\gamma1$) impair NGF-mediated PC12 cells differentiation. However, whether the enzymatic activity is also implicated in this process remains elusive. Here, we report that the enzymatic activity of phospholipase C-$\gamma1$ (PLC-$\gamma1$) is at least partially involved to the blockage of neuronal differentiation via an abrogation of MAPK activation, as well as sustained Akt activation. By contrast, Overexpression of WT-PLC-$\gamma1$ exhibited sustained NGF-induced MAPK activation, and triggered transient Akt activation resulting in profound inhibition of neurite outgrowth. However, lipase-inactive mutant (LIM) PLC-$\gamma1$ cells fail to suppress neurite outgrowth, although it contains intact SH domains, specifically enhancing the expression of cyclin D1 and p21 proteins, which regulate the function of retinoblastoma Rb protein. These observations show that the lipase inactive mutant of PLC-$\gamma1$ does not alter NGF-induced neuronal differentiation via enzymatic inability and the modulation of cell cycle regulatory proteins independent on SH3 domain.
Chemical Modification of Brain Glutamate Dehydrogenase Isoproteins with Phenylglyoxal
Cho, Sung-Woo,Ahn, Jee-Yin,Cho, Eun-Hee,Lee, Kil-Soo,Choi, Soo-Young The Korea Science and Technology Center 1999 BMB Reports Vol.32 No.5
Incubation of two types of glutamate dehydrogenase isoproteins from bovine brain with the arginine-specific dicarbonyl reagent phenylglyoxal resulted in a biphasic loss of enzyme activity. Reaction of the glutamate dehydrogenase isoproteins with phenylglyoxal caused a rapid loss of 53∼62% of the enzyme activities and modification of two residues of arginine per enzyme subunit. Prolonged incubation of the glutamate dyhydrogenase isoproteins with phenylglyoxal resulted in the modification of an additional four residues of arginine per enzyme subunit without further loss of the residual activities. Partial protection against inactivation was provided by the coenzyme NADH or substrate 2-oxoglutarate. The most marked decreased in the rate of inactivation was observed by the combined addition of NADH and 2-oxoglutarate, suggesting that the first two modified arginine residues are in the vicinity of the catalytic site. However, inactivation of the glutamate dehydrogenase isoproteins by phenylglyoxal appears to be partial with approximately 40% activity remained after an extended reaction time with excess reagent, suggesting that the modified arginine residues may not be directly involved in catalysis. The lack of complete protection by substrates also suggest the possibility that the modified arginine residues are not directly involved at the active site, and the partial loss of activity by the modification of arginine residues may be due to a conformational change. There were no significant differences between the two glutamate dehydrogenase isoproteins in sensitivities to inactivation by phenylglyoxal, indicating that the microenvironmental structures of the glutamate dehydrogenase isoproteins are very similar to each other.
CHO, SUNG-WOO,AHN, JEE-YIN,BAHN, JAE HOON,JEON, SEONG GYU,PARK JINSEU,LEE, KIL SOO,CHOI, SOO YOUNG 한국미생물 · 생명공학회 2000 Journal of microbiology and biotechnology Vol.10 No.5
Monoclonal antibodies against glutamate dehydrogenase (GDH) from Sulfolobus solfataricus were produced and characterized using epitope mapping and biosensor technology. Five monoclonal antibodies raised against S. solfataricus GDH were each identified as a single protein band that comigrated with purified S. solfataricus GDH on the SDS-polyacrylamide gel electrophoresis and immunoblot. Epitope mapping analysis showed that only one subgroup among the antibodies tested recognized the same peptide fragments of GDH. Using the anti-S. solfataricus GDH antibodies as probes, the cross-reactivities of GDHs from various sources were investigated and it was found that the mammalian GDH is not immunologically related to S. solfataricus GDH. The structural differences between the microbial and mammalian GDHs were further investigated using biosensor technology (Pharmacia BlAcore) and monoclonal antibodies against S. solfataricus and bovine brain. The binding affinity of S. solfataricus glutamate dehydrogenase anti-S. solfataricus for GDH (K_D=11nM) was much tighter than that of anti-bovine for GDH (K_D=450nM). These results, together with the epitope mapping analysis, suggest that there may be structural differences between the two GDH species, in addition to their different biochemical properties.
Suppression of Lipopolysaccharide-Induced Microglial Activation by a Benzothiazole Derivative
Kim, Eun-A,Kim, Han-Wook,Ahn, Jee-Yin,Hahn, Hoh-Gyu,Kim, Key-Sun,Kim, Tae-Ue,Cho, Sung-Woo Korean Society for Molecular and Cellular Biology 2010 Molecules and cells Vol.30 No.1
We previously reported that KHG21834, a benzothiazole derivative, attenuates the beta-amyloid (A${\beta}$)-induced degeneration of both cortical and mesencephalic neurons in vitro. Central nervous system inflammation mediated by activated microglia is a key event in the development of neurodegenerative disease. In this study, we show that KHG21834 suppresses inflammation-mediated cytokine upregulation. Specifically, KHG21834 induces significant reductions in the lipopolysaccharide-induced activation of microglia and production of proinflammatory mediators such as tumor necrosis factor-${\alpha}$, interlukin-1${\beta}$, nitric oxide, and inducible nitric oxide synthase. In addition, KHG21834 blocks the expression of mitogen-activated protein kinases, including ERK, p38 MAPK, JNK, and Akt. In vivo intracerebroventricular infusion of KHG21834 also leads to decreases the level of interleukin-1${\beta}$ and tumor necrosis factor-${\alpha}$ in brain. These results, in combination with our previous findings on A${\beta}$-induced degeneration, support the potential therapeutic efficacy of KHG21834 for the treatment of neurodegenerative disorders via the targeting of key glial activation pathways.
Chaperone-E3 Ligase Complex HSP70-CHIP Mediates Ubiquitination of Ribosomal Protein S3
Hwang, Inwoo,Cho, Sung-Woo,Ahn, Jee-Yin MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.9
<P>In addition to its role in ribosome biogenesis, ribosomal protein S3 (RPS3), a component of the 40S ribosomal subunit, has been suggested to possess several extraribosomal functions, including an apoptotic function. In this study, we demonstrated that in the mouse brain, the protein levels of RPS3 were altered by the degree of nutritional starvation and correlated with neuronal apoptosis. After endurable short-term starvation, the apoptotic function of RPS3 was suppressed by Akt activation and Akt-mediated T70 phosphorylation, whereas after prolonged starvation, the protein levels of RPS3 notably increased, and abundant neuronal death occurred. These events coincided with ubiquitination and subsequent degradation of RPS3, controlled by HSP70 and the cochaperone E3 ligase: carboxy terminus of heat shock protein 70-interacting protein (CHIP). Thus, our study points to an extraribosomal role of RPS3 in balancing neuronal survival or death depending on the degree of starvation through CHIP-mediated polyubiquitination and degradation.</P>