Biomedical subjects

Fuminori Yamaguchi

Publications and source records attributed to Fuminori Yamaguchi.

11 recordsLinked to original sources

PubMed2007

p90 RSK-1 associates with and inhibits neuronal nitric oxide synthase.

Evidence is presented that RSK1 (ribosomal S6 kinase 1), a downstream target of MAPK (mitogen-activated protein kinase), directly phosphorylates nNOS (neuronal nitric oxide synthase) on Ser847 in response to mitogens. The phosphorylation thus increases greatly following EGF (epidermal growth factor) treatment of rat pituitary tumour GH3 cells and is reduced by exposure to the MEK (MAPK/extracellular-signal-regulated kinase kinase) inhibitor PD98059. Furthermore, it is significantly enhanced by expression of wild-type RSK1 and antagonized by kinase-inactive RSK1 or specific reduction of endogenous RSK1. EGF treatment of HEK-293 (human embryonic kidney) cells, expressing RSK1 and nNOS, led to inhibition of NOS enzyme activity, associated with an increase in phosphorylation of nNOS at Ser847, as is also the case in an in vitro assay. In addition, these phenomena were significantly blocked by treatment with the RSK inhibitor Ro31-8220. Cells expressing mutant nNOS (S847A) proved resistant to phosphorylation and decrease of NOS activity. Within minutes of adding EGF to transfected cells, RSK1 associated with nNOS and subsequently dissociated following more prolonged agonist stimulation. EGF-induced formation of the nNOS-RSK1 complex was significantly decreased by PD98059 treatment. Treatment with EGF further revealed phosphorylation of nNOS on Ser847 in rat hippocampal neurons and cerebellar granule cells. This EGF-induced phosphorylation was partially blocked by PD98059 and Ro31-8220. Together, these data provide substantial evidence that RSK1 associates with and phosphorylates nNOS on Ser847 following mitogen stimulation and suggest a novel role for RSK1 in the regulation of nitric oxide function in brain.

Amino Acid Sequence↗

PubMed2006

Clinical significance of Skp2 expression, alone and combined with Jab1 and p27 in epithelial ovarian tumors.

We have previously demonstrated the inverse correlation of Jab1 and p27 proteins, as well as prognostic significance in epithelial ovarian carcinomas. In order to investigate Skp2 protein and its correlation with Jab1, p27, and clinical outcome, we evaluated Skp2 expression in a group of epithelial ovarian tumors. Immunohistochemical analysis was performed on 80 cases of ovarian tumors (33 benign and 47 malignant), and 26 of the 80 cases were evaluated by Western blot analysis. Immunofluorescence was carried out in the human ovarian adenocarcinoma cell line OVCAR-3. Skp2 expression was detected in 53.2% of malignant tumors and 18.2% of benign tumors. The positive ratio of Skp2 expression was increased from benign to malignant ovarian tumors (p=0.002). A negative correlation between Skp2 and p27 was found in benign and malignant ovarian tumors (p=0.006 and p<0.0001, respectively). Skp2 expression was significantly associated with high tumor grade (p=0.001), lymph node metastasis (p=0.01), and residual disease (p=0.012). Kaplan-Meier survival analysis showed that Skp2 expression was significantly associated with poor prognosis (p=0.013), and patients with Skp2(+)/Jab1(+)p27(-) expression had the worst prognosis among all phenotypes of Skp2/Jab1/p27 expression (p=0.0007). Our results suggest that Skp2 expression was significantly associated with malignancy, and the Skp2 protein level may be a valuable prognostic factor for epithelial ovarian carcinomas. Furthermore, the combined evaluation of Skp2/Jab1/p27 proteins provides important prognostic information on patients with epithelial ovarian carcinoma.

Blotting, Western↗

PubMed2006

Alteration and clinical relevance of PTEN expression and its correlation with survivin expression in epithelial ovarian tumors.

The tumor suppressor PTEN, phosphatase and tensin homolog on chromosome 10, plays an essential role in regulating signaling pathways involved in cell growth and apoptosis and is inactivated in a wide variety of tumors. Survivin, a member of the inhibitor of apoptosis protein family (IAP), is associated with cell proliferation, and overexpressed in common human tumors. Both PTEN and survivin proteins can regulate cell cycle and apoptosis, but their biological effects are adverse. We have previously investigated the role of survivin expression in epithelial ovarian tumors. In this study, we evaluated the alteration and clinical relevance of PTEN expression and further assessed its correlation with survivin expression in epithelial ovarian tumors. Immunohistochemical analysis was performed in 103 cases of ovarian tumors, and 26 of the 103 cases were evaluated by Western blot analysis. PTEN expression was reduced from benign to malignant ovarian tumors (p=0.0003), and an inverse correlation between PTEN and survivin was found in benign, borderline, and malignant tumors (p=0.004, p=0.015 and p=0.0005, respectively). PTEN expression was significantly associated with tumor grade (p=0.001), histological subtype (p=0.037), ascites (p=0.038), and residual disease (p=0.0006). Kaplan-Meier survival analysis showed that the loss of PTEN expression was significantly associated with poor overall survival (p=0.021), and patients with PTEN(-)/survivin(+) expression had the worst prognosis among all phenotypes of PTEN/survivin expression (p=0.039). Our results suggest that the altered PTEN expression and its inverse correlation with survivin may be involved in the development and progression of ovarian tumors, and the combined detection of PTEN and survivin proteins might be more valuable in the evaluation of malignancy and prognosis in epithelial ovarian tumors.

Epithelial Cells↗

PubMed2005

Inhibition of neuronal nitric-oxide synthase by phosphorylation at Threonine1296 in NG108-15 neuronal cells.

We demonstrate that neuronal nitric-oxide synthase (nNOS) is directly inhibited through the phosphorylation of Thr(1296) in NG108-15 neuronal cells. Treatment of NG108-15 cells expressing nNOS with calyculin A, an inhibitor of protein phosphatase 1 and 2A, revealed a dose-dependent inhibition of nNOS enzyme activity with concomitant phosphorylation of Thr(1296) residue. Cells expressing a phosphorylation-deficient mutant in which Thr(1296) was changed to Ala proved resistant to phosphorylation and suppression of NOS activity. Mimicking phosphorylation mutant of nNOS in which Thr(1296) is changed to Asp showed a significant decrease in nNOS enzyme activity, being competitive with NADPH, relative to the wild-type enzyme. These data suggest that phosphorylation of nNOS at Thr(1296) may involve the attenuation of nitric oxide production in neuronal cells through the decrease of NADPH-binding to the enzyme.

Animals↗

PubMed2005

Prognostic significance of Jab1 expression in laryngeal squamous cell carcinomas.

PURPOSE: Jun activation domain-binding protein 1 (Jab1) is known as a coactivator of AP1 transcription factor, which contributes to tumor progression by degrading the p27kip1 protein. The purpose of this study is to investigate whether Jab1 expression is correlated with p27kip1 level and cell proliferation, as well as whether Jab1 expression is associated with clinicopathologic variables and prognosis of laryngeal squamous cell carcinoma (LSCC). EXPERIMENTAL DESIGN: Immunohistochemical and/or Western blot analysis was done in HEp-2 cells and 102 cases of LSCCs. RESULTS: Jab1 expression was negatively associated with p27kip1 expression and was positively associated with cell proliferation both in HEp-2 cells and LSCCs. Jab1 overexpression was detected in 51% LSCCs and was significantly associated with unfavorable clinicopathologic variables. Survival analysis revealed that Jab1 overexpression is significantly associated with short disease-free and overall survival (P = 0.0036 and P = 0.0001, respectively). When Jab1 and p27kip1 are combined, patients with Jab1(+)/p27kip1(-) revealed poor disease-free and overall survival (P= 0.0008 and P < 0.0001, respectively). When Jab1 expression and lymph node status are combined, patients with Jab1(+)/lymph node(+) revealed poorer disease-free andoverall survival than others (P < 0.0001 and P < 0.0001, respectively). Furthermore, patients with the phenotype of Jab1(+)/p27kip1(-)/lymph node(+) revealed the worst disease-free and overall survival (P < 0.0001 and P < 0.0001, respectively). Multivariate analysis revealed that Jab1 protein is an independent prognostic indicator for overall survival. CONCLUSIONS: These findings suggested that Jab1 protein may contribute to the tumor progression and represent a novel prognostic indicator for LSCCs.

Adult↗

PubMed2005

Neuroprotective effect of D-psicose on 6-hydroxydopamine-induced apoptosis in rat pheochromocytoma (PC12) cells.

We evaluated the neuroprotective effects of D-psicose, one of the rare sugars, on 6-hydroxydopamine (6-OHDA)-induced apoptosis in catecholaminergic PC12 cells, the in vitro model of Parkinson's disease (PD). Apoptotic characteristics of PC12 cells were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling (TUNEL) assay. The results showed that D-psicose at a concentration of 50 mM, exerted significant protective effects against the 6-OHDA (200 muM)-induced PC12 cell apoptosis, while other sugars had little or no protective effects. We have observed a significant increase in the level of intracellular glutathione after 24 h in 6-OHDA (200 muM) treated cells, while a decrease in the level was observed at 3 h and 6 h. Also, a synergistic exposure to D-psicose and 6-OHDA for 24 h showed a significant increase in intracellular glutathione level. Therefore, these results suggest that D-psicose may play a potential role as a neuroprotective agent in the treatment of neurodegenerative diseases by inducing an up-regulation of intracellular glutathione.

Adrenergic Agents↗

PubMed2005

The inhibitory effect and possible mechanisms of D-allose on cancer cell proliferation.

Rare sugars are monosaccharides distributed rarely in nature, because of its very limited amount and cost, the biological effect has hardly been studied. Recently, an effective strategy for mass production of rare sugars has been developed. As a result, a wide range of study of rare sugars from the basic to applied research has become possible. For biological application of rare sugars, it is necessary to fundamentally investigate the relationships between rare sugars and living cells in terms of physiology. Therefore, we firstly examined the effect of rare sugars including D-psicose, D-allose, D-altrose and D-talitol on cell proliferation using certain cell lines in vitro. Cell growth was evaluated by MTT assay after 24-, 48- and 72-h treatment. The result shows that D-allose has a significant inhibitory effect on cancer cell proliferation in a dose-dependent manner. Although the exact mechanism remains unclear, this finding represents a novel aspect of the biological profile of D-allose and suggests that D-allose may be an effective adjuvant therapeutic agent against cancer in the future.

Apoptosis↗

PubMed2004

Calcium/calmodulin-dependent protein kinase I inhibits neuronal nitric-oxide synthase activity through serine 741 phosphorylation.

We demonstrate here that neuronal nitric-oxide synthase (nNOS) is phosphorylated and inhibited by a constitutively active form of Ca2+/calmodulin (CaM)-dependent protein kinase I (CaM-K I1-293). Substitution of Ser741 to Ala in nNOS blocked the phosphorylation and the inhibitory effect. Mimicking phosphorylation at Ser741 by Ser to Asp mutation resulted in decreased binding of and activation by CaM, since the mutation was within the CaM-binding domain. CaM-K I1-293 gave phosphorylation of nNOS at Ser741 in transfected cells, resulting in 60-70% inhibition of nNOS activity. Wild-type CaM-K I also did phosphorylate nNOS at Ser741 in transfected cells, but either CaM-K II or CaM-K IV did not. These results raise the possibility of a novel cross-talk between nNOS and CaM-K I through the phosphorylation of Ser741 on nNOS.

Alanine↗

PubMed2004

Phosphohippolin expression in the rat central nervous system.

The FXYD family is a small single-span membrane protein family; recently, we have identified a novel member of this family from the cDNA library of the rat hippocampus and named phosphohippolin (Php) (Mol. Br. Res. vol. 86, 2001). The deduced amino acid sequence of this novel Php comprises 93 residues with a core motif of FXYD and a single transmembrane domain. This indicates that Php belongs to FXYD6 subfamily of the seven FXYD subfamilies (FXYD1-7). Php shows a 48.1% homology with rat phospholemman (FXYD1), a transmembrane family protein. In this study, polyclonal antibodies against the carboxyl-terminal sequence of rat Php were raised and purified. The spatial expression of the Php protein was in the neuronal fibers of the medial part of lateral habenula nucleus, thalamus, hypothalamus, stria terminalis, zona incerta, amygdaloid body and cingulum, olfactory bulb, hippocampus, cerebral cortex and cerebellum. A unique Php distribution was identified in the cerebellum, with a predominant expression pattern in the granule layer of lobules VI-IX of the posterior lobe. Developmental studies demonstrated that the highest level of Php expression was seen in the postnatal (PN) 3-week-old rat brain, and a significant amount of Php still existed in the adult brain. These findings suggest that Php may play an important role in the excitability of neurons in the central nervous system during postnatal development, as well as those in the adult brain.

Aging↗

PubMed2003

A novel inhibitory effect of D-allose on production of reactive oxygen species from neutrophils.

The rare sugar D-allose produced from D-psicose using an immobilized L-rhamnose isomerase bioreactor was shown to have weak scavenging activity toward reactive oxygen species (ROS) and potent inhibitory effect on production of ROS from stimulated neutrophils. These findings may have important implications in understanding the ameliorative effect of D-allose in transplantation and ischemia/reperfusion injury.

Journal Article↗

PubMedDate not supplied

Growth inhibitory effect of D-allose on human ovarian carcinoma cells in vitro.

BACKGROUND: D-allose is a rare sugar found in nature and, because of its very limited amount and of the high cost associated with its synthesis, its physiological functions remain virtually unknown. The aim of the current study was to investigate the effect of D-allose on the proliferation of human ovarian carcinoma cells in vitro. MATERIALS AND METHODS: Human ovarian carcinoma cells (OVCAR-3 cell line) were exposed to rare sugars including D-allose, D-altrose, D-psicose and D-talitol. Cell growth was evaluated by MTT assay. Cell cycle analysis was carried out by flow cytometric assay. The expression of cell cycle regulatory proteins was determined by Western blot analysis. TUNEL assay was employed for the detection of apoptotic cells. RESULTS: D-allose had a significant inhibitory effect on ovarian cancer cell proliferation in a dose-dependent manner, and caused a moderate G2/M arrest in the cell cycle, up-regulation of Cdk inhibitors p21 and p27 levels, and the induction of apoptosis in OVCAR-3 cells. CONCLUSION: Our results show, for the first time, that D-allose inhibits the growth of ovarian carcinoma cells in vitro. Although the exact mechanisms remain unclear, these findings suggest that D-allose possesses a novel inhibitory property on ovarian carcinoma cell proliferation, and may represent a new class of compounds with possible therapeutic potential.

Adenocarcinoma↗