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Biomedical subjects

M Takekawa

Publications and source records attributed to M Takekawa.

At least 19 recordsLinked to original sources
PubMed2005

Regulation of the antioncogenic Chk2 kinase by the oncogenic Wip1 phosphatase.

The antioncogenic Chk2 kinase plays a crucial role in DNA damage-induced cell-cycle checkpoint regulation. Here we show that Chk2 associates with the oncogenic protein Wip1 (wild-type p53-inducible phosphatase 1) (PPM1D), a p53-inducible protein phosphatase. Phosphorylation of Chk2 at threonine68 (Thr68), a critical event for Chk2 activation, which is normally induced by DNA damage or overexpression of Chk2, is inhibited by expression of wild-type (WT), but not a phosphatase-deficient mutant (D314A) of Wip1 in cultured cells. Furthermore, an in vitro phosphatase assay revealed that Wip1 (WT), but not Wip1 (D314A), dephosphorylates Thr68 on phosphorylated Chk2 in vitro, resulting in the inhibition of Chk2 kinase activity toward glutathione S-transferase-Cdc25C. Moreover, inhibition of Wip1 expression by RNA interference results in abnormally sustained Thr68 phosphorylation of Chk2 and increased susceptibility of cells in response to DNA damage, indicating that Wip1 acts as a negative regulator of Chk2 in response to DNA damage.

Amino Acids↗
PubMed2003

Angiogenesis after sintered bone implantation in rat parietal bone.

We studied the effect of bone substitutes on revascularization and the restart of blood supply after sintered bone implantation in comparison with synthetic hydroxyapatite implantation and fresh autogenous bone transplantation (control) in rat parietal bones. Methods for the study included the microvascular corrosion cast method and immunohistochemical techniques were also used. The revascularization of the control group was the same as that for usual wound healing in the observations of the microvascular corrosion casts. The sintered bone implantation group was quite similar to that of the control group. In the synthetic hydroxyapatite group, immature newly-formed blood vessels existed even on the 21st day after implantation and the physiological process of angiogenesis was interrupted. Immunohistochemically, vascular endothelial growth factor (VEGF), which activates angiogenesis, appeared at the early stages of both the control group and the sintered bone implantation group. VEGF reduced parallel with the appearance of the transforming growth factor factor-beta-1 (TGF-beta-1), which obstructs angiogenesis, and the angiogenesis passed gradually into the mature stage. In the hydroxyapatite implantation group, TGF-beta-1 appeared at the early stage of the implants. The appearance of VEGF lagged and it existed around the pores of hydroxyapatite even on the 21st day of the implantation. Proliferation and wandering of endothelial cells continued without any maturing of the vessels. These findings suggest that the structure and the components of the implant material affect angiogenesis after implantation as well as new bone formation.

Animals↗
PubMed2002

MEK/ERK pathway protects ionizing radiation-induced loss of mitochondrial membrane potential and cell death in lymphocytic leukemia cells.

MEK/ERK-mediated signals have recently been found to inhibit Fas-mediated cell death through inhibition of caspase-8 activity. It remains unknown whether MEK/ERK-mediated signals affect ionizing radiation (IR)-induced cell death. Here we demonstrate that MEK/ERK-mediated signals selectively inhibit IR-induced loss of mitochondrial membrane potential (DeltaPsi(m)) and subsequent cell death. In Jurkat cells, TPA strongly activated ERK and inhibited the IR-induced caspase-8/Bid cleavage and the loss of DeltaPsi(m). The inhibitory effect of TPA was mostly abrogated by pretreatment of a specific MEK inhibitor PD98059, indicating that the effect depends upon MEK/ERK-mediated signals. Moreover, BAF-B03 transfectants expressing IL-2 receptor (IL-2R) beta(c) chain lacking the acidic region, which is responsible for MEK/ERK-mediated signals, revealed higher sensitivity to IR than the transfectants expressing wild-type IL-2R. Interestingly, the signals could neither protect the DeltaPsi(m) loss nor cell death in UV-irradiated cells. These data imply that the anti-apoptotic effect of MEK/ERK-mediated signals appears to selectively inhibit the IR-induced cell death through protection of the DeltaPsi(m) loss. Our data enlighten an anti-apoptotic function of MEK/ERK pathway against IR-induced apoptosis, thereby implying its contribution to radioresistance.

BH3 Interacting Domain Death Agonist Protein↗
PubMed2002

Analysis of gene expression during maturation of immature dendritic cells derived from peripheral blood monocytes.

Dendritic cells (DCs) are the most important antigen-presenting cells. Many recent studies have compared the function of immature DCs (iDCs) and mature DCs (mDCs), but there have been few reports of the molecular changes that occur in DCs during maturation. Here, we report on differential gene expression in iDCs generated from peripheral blood monocytes compared with mDCs. Gene expression was evaluated using the differential display method after activation of iDCs with a low concentration of lipopolysaccharide (LPS) to induce maturation. Proteasome subunit alpha type 3 (PSMA3), transcription factor EC (TFEC) isoform and BTK region clone 2f10-rpi were transiently upregulated. Tryptophanyl-tRNA synthetase and CD63 antigen were upregulated for at least 24 h. Neuronal apoptosis inhibitory protein (NAIP) and transforming growth factor-beta-induced 68 kDa protein were downregulated. This is the first report of NAIP expression in human DCs. By comparing the expression of NAIP with that of other members of the inhibitor of apoptosis protein (IAP) family and the Bcl-2 family, only NAIP was found to be strongly expressed in iDCs before stimulation by LPS. PSMA3 was also induced in the DCs stimulated with immune complex. These findings might contribute to our understanding of DC maturation and the effectiveness of DC-based vaccines.

Apoptosis↗
PubMed2002

Nuclear export of glucocorticoid receptor is enhanced by c-Jun N-terminal kinase-mediated phosphorylation.

The c-Jun N-terminal kinase (JNK) phosphorylates the glucocorticoid receptor (GR) and inhibits GR-mediated transcription. However, the biological effect of the GR phosphorylation remains unknown. Here we demonstrate that activated JNK phosphorylates human GR at Ser226 and enhances its nuclear export after withdrawal of a ligand for GR, dexamethasone. At 1 h after dexamethasone withdrawal, green fluorescent protein-GR molecules were mostly retained at the nucleus, whereas UV exposure enhanced its nuclear export, and approximately 30-40% of cells revealed distinct nuclear export. JNK overexpression alone mimics UV exposure and enhanced GR export accompanied by inhibition of GR-mediated transcription. However, mutation of the Ser226 JNK phosphorylation site in GR abrogated UV-mediated enhancement of GR nuclear export. Furthermore, overexpression of a dominant negative SEK1 mutant also abrogated the effects of UV exposure on GR export. Taken together, these findings suggest that JNK-mediated phosphorylation of the GR-Ser226 enhances GR nuclear export and may contribute to termination of GR-mediated transcription.

Active Transport, Cell Nucleus↗
PubMed2000

p53-inducible wip1 phosphatase mediates a negative feedback regulation of p38 MAPK-p53 signaling in response to UV radiation.

The stress-responsive p38 MAPK, when activated by genotoxic stresses such as UV radiation, enhances p53 activity by phosphorylation and leads to cell cycle arrest or apoptosis. Here we report that a member of the protein phosphatase type 2C family, Wip1, has a role in down-regulating p38-p53 signaling during the recovery phase of the damaged cells. Wip1 was originally identified as a gene whose expression is induced following gamma or UV radiation in a p53-dependent manner. We found that Wip1 is also inducible by other environmental stresses, such as anisomycin, H(2)O(2) and methyl methane sulfonate. UV-induction of Wip1 requires p38 activity in addition to the wild-type p53. Wip1 selectively inactivates p38 by specific dephosphorylation of its conserved threonine residue. Furthermore, Wip1 expression attenuates UV-induced p53 phosphorylation at Ser33 and Ser46, residues previously reported to be phosphorylated by p38. Wip1 expression also suppresses both p53-mediated transcription and apoptosis in response to UV radiation. These results suggest that p53-dependent expression of Wip1 mediates a negative feedback regulation of p38-p53 signaling and contributes to suppression of the UV-induced apoptosis.

Animals↗
PubMed2000

Histone deacetylase inhibitors suppress IL-2-mediated gene expression prior to induction of apoptosis.

Histone deacetylase (HDAC) inhibitors can induce transcriptional activation of a number of genes and induce cellular differentiation as histone acetylation levels increase. Although these inhibitors induce apoptosis in several cell lines, the precise mechanism by which they do so remains obscure. This study shows that HDAC inhibitors, sodium butyrate and trichostatin A (TSA), abrogate interleukin (IL)-2-mediated gene expression in IL-2-dependent cells. The HDAC inhibitors readily induced apoptosis in IL-2-dependent ILT-Mat cells and BAF-B03 transfectants expressing the IL-2 receptor betac chain, whereas they induced far less apoptosis in cytokine-independent K562 cells. However, these inhibitors similarly increased acetylation levels of histones in both cells. Although histone hyperacetylation is believed to lead to transcriptional activation, the results showed an abrogation of IL-2-mediated induction of c-myc, bag-1, and LC-PTP gene expression. This observed abrogation of gene expression occurred prior to phosphatidylserine externalization, a process that occurs in early apoptotic cells. Considering the biologic role played by IL-2-mediated gene expression in cell survival, these data suggest that its abrogation may contribute to the apoptotic process induced by HDAC inhibitors. (Blood. 2000;96:1490-1495)

Animals↗
PubMed2000

Effect of irradiation on autogenous bone transplantation in rat parietal bone.

To determine the appropriate time for bone reconstruction after irradiation, the healing process after autogenous iliac bone transplantation in the irradiated parietal bone was examined by scanning electron microscopy and light microscopy. Bone transplantation was carried out at the second and the fourth weeks after Cobalt-sixty (60Co) irradiation with calculated dose and fractionation. Animals without irradiation were used as control. The results show the appearance of mesenchymal cells and blood vessels around the transplantation to be extremely few one week after transplantation which was carried out at the second week after irradiation. These inhibitions were still seen two weeks after transplantation. Four weeks after transplantation, there were no differences in the bone formation among the experimental groups. Bone formation in the transplantation at the fourth week after irradiation was similar to that of the control group. Microvascularization in the transplantation at the second week after irradiation was inhibited one week after transplantation. The delay in bone healing was responsible for the retardation of revascularization and caused microcirculatory failures as well as the damage of osteogenic cells. It is quite clear that damaged cells and tissues recovered by the elapse of time under the irradiation procedure employed in this study and also that bone formation was carried out in the physiological process. We think that bone transplantation after irradiation should be done after recovery from the radiation damage to the periosteal cells and the blood vessels.

Animals↗
PubMed2000

[Antibody treatment for cancer].

The previous pessimistic view of monoclonal antibodies as cancer therapeutics was largely influenced by the negative results of multiple clinical trials initiated shortly after the introduction of hybridoma technology. Although murine antibodies are of value in cancer therapy, their effectiveness is limited because murine monoclonal antibodies have a short survival time in humans and induce an immune response that neutralizes their therapeutic effect. Furthermore, the responses induced by murine antibodies are limited because they only weakly recruit human effector elements. To circumvent these problems, genetically engineered antibodies were produced which were mouse-human chimeric monoclonal antibodies and humanized antibodies. These antibodies combine the murine variable or hypervariable regions with the human constant or constant and variable framework regions. Numerous published studies demonstrate that erbB-2 oncogene product overexpression is a frequent cause of breast, ovarian, lung, and gastric cancers. Recently, an anti-erbB-2 humanized monoclonal antibody has been generated and used in clinical trials with high clinical response rates. We generated the anti-erbB-2 mouse-human chimeric monoclonal antibody CH401, which was able to kill cancer cells. An analysis of the mechanism of its tumor growth inhibition revealed that the cytotoxicity was induced by apoptosis. This cytotoxic mechanism is not the same a that of other anti-erbB-2 antibodies previously reported.

Animals↗
PubMed2000

[Polyarthralgia as the initial manifestation of isolated ACTH deficiency].

A 57-year-old man, employed as a taxi driver, noticed arthralgia of his fingers beginning in May 1999. He was unable to work due to the arthralgia and the accompanying general malaise and anorexia, and was thus admitted to a local hospital in July 1999. Since a diagnosis of rheumatic disease was suspected due to elevated inflammatory reactions and joint symptoms, he was referred to our hospital in September 1999. Although no joint swelling was observed, severe tenderness was present in both the fingers and wrists. His grasping power had decreased markedly and fever was intermittently observed. All autoantibodies aside from antinuclear antibody were negative. Given that hyponatremia (126 mEq/l) and fasting hypoglycemia were demonstrated, an endocrinological examination, in particular for hypopituitary-adrenal function, was performed. Both plasma and urinary cortisol concentrations were very low, and an associated low concentration of plasma ACTH (6.0 pg/ml) was noted. The ACTH circadian rhythm was absent and there was no response to the administration of corticotropin releasing hormone. All other pituitary hormones were secreted at normal levels and brain MRI revealed a normal appearance of a pituitary gland. Based on these findings, the patient was diagnosed as having isolated ACTH deficiency. Arthralgia and general malaise both improved soon after replacement of glucocorticoid, and CRP levels were normalized. Isolated ACTH deficiency should be considered in the differential diagnosis of patients suffering from polyarthralgia, given that fever and increased inflammatory reactions occasionally develop and that rheumatic symptoms are also present, as in the present case.

Adrenocorticotropic Hormone↗
PubMed1999

Functional role for protein kinase Cbeta as a regulator of stress-activated protein kinase activation and monocytic differentiation of myeloid leukemia cells.

Human myeloid leukemia cells respond to 12-O-tetradecanoylphorbol-13-acetate (TPA) and other activators of protein kinase C (PKC) with induction of monocytic differentiation. The present studies demonstrated that treatment of U-937 and HL-60 myeloid leukemia cells with TPA, phorbol-12,13-dibutyrate, or bryostatin 1 was associated with the induction of stress-activated protein kinase (SAPK). In contrast, TPA-resistant TUR and HL-525 cell variants deficient in PKCbeta failed to respond to activators of PKC with the induction of SAPK. A direct role for PKCbeta in TPA-induced SAPK activity in TUR and HL-525 cells that stably express PKCbeta was confirmed. We showed that TPA induced the association of PKCbeta with MEK kinase 1 (MEKK-1), an upstream effector of the SAPK/ERK kinase 1 (SEK1)-->SAPK cascade. The results also demonstrated that PKCbeta phosphorylated and activated MEKK-1 in vitro. The functional role of MEKK-1 in TPA-induced SAPK activity was further supported by the demonstration that the expression of a dominant negative MEKK-1 mutant abrogated this response. These findings indicate that PKCbeta activation is necessary for activation of the MEKK-1-->SEK1-->SAPK cascade in the TPA response of myeloid leukemia cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Increased serum concentration of circulating soluble receptor for interleukin-2 and its effect as a prognostic indicator in cachectic patients with gastric and colorectal cancer.

Serum concentration of soluble interleukin-2 receptor (sIL-2R) was measured in noncachectic patients with 42 gastric and 32 colorectal cancers, 39 cachectic cancer patients and 15 normal volunteers. It increased with the advance of cancer, being highest in the cachectic patients. It was inversely correlated with the serum concentrations of nutriotional parameters such as prealbumin and transferrin, and positively correlated with the serum concentration of immunosuppressive acidic protein, soluble tumor necrosis factor receptor 1 and neopterin. The length of survival of cachectic patients (days) was inversely correlated also with the serum concentration of sIL-2R. These findings suggest that sIL-2R might be of use an important parameter to predict the progress of gastric and colorectal cancers, deterioration of the patients' nutriotional status and immune activity as well as their prognosis.

Cachexia↗
PubMed1998

A family of stress-inducible GADD45-like proteins mediate activation of the stress-responsive MTK1/MEKK4 MAPKKK.

The stress-responsive p38 and JNK MAPK pathways regulate cell cycle and apoptosis. A human MAPKKK, MTK1 (= MEKK4), mediates activation of both p38 and JNK in response to environmental stresses. Using a yeast two-hybrid method, three related proteins, GADD45alpha (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound to an N-terminal domain of MTK1. These proteins activated MTK1 kinase activity, both in vivo and in vitro. The GADD45-like genes are induced by environmental stresses, including MMS, UV, and gamma irradiation. Expression of the GADD45-like genes induces p38/JNK activation and apoptosis, which can be partially suppressed by coexpression of a dominant inhibitory MTK1 mutant protein. We propose that the GADD45-like proteins mediate activation of the p38/JNK pathway, via MTK1/ MEKK4, in response to environmental stresses.

Amino Acid Sequence↗
PubMed1998

Protein phosphatase 2Calpha inhibits the human stress-responsive p38 and JNK MAPK pathways.

MAPK (mitogen-activated protein kinase) cascades are common eukaryotic signaling modules that consist of a MAPK, a MAPK kinase (MAPKK) and a MAPKK kinase (MAPKKK). Because phosphorylation is essential for the activation of both MAPKKs and MAPKs, protein phosphatases are likely to be important regulators of signaling through MAPK cascades. To identify protein phosphatases that negatively regulate the stress-responsive p38 and JNK MAPK cascades, we screened human cDNA libraries for genes that down-regulated the yeast HOG1 MAPK pathway, which shares similarities with the p38 and JNK pathways, using a hyperactivating yeast mutant. In this screen, the human protein phosphatase type 2Calpha (PP2Calpha) was found to negatively regulate the HOG1 pathway in yeast. Moreover, when expressed in mammalian cells, PP2Calpha inhibited the activation of the p38 and JNK cascades induced by environmental stresses. Both in vivo and in vitro observations indicated that PP2Calpha dephosphorylated and inactivated MAPKKs (MKK6 and SEK1) and a MAPK (p38) in the stress-responsive MAPK cascades. Furthermore, a direct interaction of PP2Calpha and p38 was demonstrated by a co-immunoprecipitation assay. This interaction was observed only when cells were stimulated with stresses or when a catalytically inactive PP2Calpha mutant was used, suggesting that only the phosphorylated form of p38 interacts with PP2Calpha.

Amino Acid Sequence↗
PubMed1998

Increased serum concentrations of soluble tumor necrosis factor receptor I in noncachectic and cachectic patients with advanced gastric and colorectal cancer.

The serum levels of soluble tumor necrosis factor receptor I (sTNF-RI) were measured in 74 noncachectic patients including 42 with gastric cancer and 32 with colorectal cancer, as well as in 39 patients with severe cachexia and 15 healthy volunteers. The sTNF-RI levels increased with the advance of disease, being highest in the cachectic patients. The levels were inversely correlated with the serum concentrations of nutritional parameters such as prealbumin, transferrin, retinol binding protein, and the percentages of CD3(+) cells in the peripheral blood lymphocytes, and positively correlated with the serum concentration of immunosuppressive acidic protein (IAP) and soluble interleukin-2 receptors. These findings suggest that sTNF-RI could be an important prognostic factor to predict the advance of gastric and colorectal cancers and deterioration of the patient's nutritional and immune activity.

Antigens, CD↗
PubMed1998

Signal transduction by MAP kinase cascades in budding yeast.

Budding yeast contain at least four distinct MAPK (mitogen activated protein kinase) cascades that transduce a variety of intracellular signals: mating-pheromone response, pseudohyphal/invasive growth, cell wall integrity, and high osmolarity adaptation. Although each MAPK cascade contains a conserved set of three protein kinases, the upstream activation mechanisms for these cascades are diverse, including a trimeric G protein, monomeric small G proteins, and a prokaryotic-like two-component system. Recently, it became apparent that there is extensive sharing of signaling elements among the MAPK pathways; however, little undesirable cross-talk occurs between various cascades. The formation of multi-protein signaling complexes is probably centrally important for this insulation of individual MAPK cascades.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

A human homolog of the yeast Ssk2/Ssk22 MAP kinase kinase kinases, MTK1, mediates stress-induced activation of the p38 and JNK pathways.

A human homolog of the yeast Ssk2 and Ssk22 mitogen-activated protein kinase kinase kinases (MAPKKK) was cloned by functional complementation of the osmosensitivity of the yeast ssk2delta ssk22delta sho1delta triple mutant. This kinase, termed MTK1 (MAP Three Kinase 1), is 1607 amino acids long and is structurally highly similar to the yeast Ssk2 and Ssk22 MAPKKKs. In mammalian cells (COS-7 and HeLa), MTK1 overexpression stimulated both the p38 and JNK MAP kinase pathways, but not the ERK pathway. MTK1 overexpression also activated the MKK3, MKK6 and SEK1 MAPKKs, but not the MEK1 MAPKK. Furthermore, MTK1 phosphorylated and activated MKK6 and SEK1 in vitro. Overexpression of a dominant-negative MTK1 mutant [MTK1(K/R)] strongly inhibited the activation of the p38 pathway by environmental stresses (osmotic shock, UV and anisomycin), but not the p38 activation by the cytokine TNF-alpha. The dominant-negative MTK1(K/R) had no effect on the activation of the JNK pathway or the ERK pathway. These results indicate that MTK1 is a major mediator of environmental stresses that activate the p38 MAPK pathway, and is also a minor mediator of the JNK pathway.

Amino Acid Sequence↗