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Biomedical subjects

Akira Kikuchi

Publications and source records attributed to Akira Kikuchi.

At least 37 records · Page 2Linked to original sources
PubMed2006

Food antigen causes TH2-dependent enteropathy followed by tissue repair in T-cell receptor transgenic mice.

BACKGROUND: Clarification of the mechanisms underlying the development of food-sensitive intestinal inflammation will provide an important clue to combating food allergies. OBJECTIVE: To establish a model of intestinal inflammation caused by oral administration of antigen without additional treatments, we focused on the ovalbumin (OVA) 23-3 T-cell receptor transgenic mouse, which had been reported to have high serum antigen-specific IgE responses to the feeding of an egg white diet. METHODS: Changes in body weight of mice fed an egg white diet were monitored throughout the 28-day experimental period. After the 28-day feeding, intestinal tissues were harvested for histologic examination. Endogenous production of cytokines and histamine in the jejunum, and production of cytokines secreted by OVA-specific CD4+ T cells purified from mesenteric lymph nodes, were analyzed. RESULTS: Egg white diet-fed OVA23-3 mice developed weight loss and inflammation with villous atrophy and goblet cell hyperplasia, especially in the jejunum. A further characteristic feature was evidence of weight recovery and tissue repair. Jejunal inflammation was also observed in egg white diet-fed recombination activating gene (RAG)-2-deficient OVA23-3 mice. In addition, tissue sections revealed significant infiltration of specific IgE-positive cells and IgE-positive degranulating mast cells. Higher levels of IL-4 and significant levels of histamine were detected in the tissues. In the supernatant of OVA-stimulated T cells, IL-10 levels were also markedly elevated. CONCLUSION: We report that high-dose and continuous intake of primitive OVA alone induces enteropathy containing regions under repair in OVA23-3 mice. Antigen-specific T cells and inflammatory cells primed by T(H)2 responses play important roles in regulation of development and improvement of the disease. CLINICAL IMPLICATIONS: Long-term antigen intake causes T(H)2-dependent and food-sensitive enteropathy followed by tissue repair.

Animals↗
PubMed2006

Suppression of STAT3 activity by Duplin, which is a negative regulator of the Wnt signal.

Duplin was originally isolated as a negative regulator of beta-catenin-dependent T-cell factor (Tcf) transcriptional activity in the Wnt signaling pathway. However, Duplin knockout mice exhibit embryonic lethality at 5.5-em day, suggesting that Duplin has important roles other than as a negative regulator of the Wnt signal. To identify new roles of Duplin, the Duplin-binding proteins were screened. PIAS3, which is a SUMO E3 ligase and acts as an inhibitor of signal transducer and activator of transcription (STAT3), was identified as a Duplin-binding protein. Duplin was sumoylated, but PIAS3 affected neither the sumoylation of Duplin nor its ability to inhibit Tcf-4 activity. Like PIAS3, Duplin suppressed the leukemia-inhibitory factor (LIF)-induced STAT3 transcriptional activity. Duplin did not affect the LIF-dependent tyrosine phosphorylation or nuclear localization of STAT3 but inhibited the formation of complex between STAT3 and DNA. Although STAT3 is not modified with SUMO, PIAS3 inhibited the STAT3 activity in a manner partially depending on its SUMO E3 ligase activity. Duplin suppressed the LIF-dependent STAT3 activity independently of sumoylation. These results demonstrate that Duplin inhibits not only Tcf-4 but also STAT3, suggesting that Duplin may act as a repressor for multiple transcriptional factors.

Animals↗
PubMed2006

Pns12 protein of Rice dwarf virus is essential for formation of viroplasms and nucleation of viral-assembly complexes.

Cytoplasmic inclusion bodies, known as viroplasms or viral factories, are assumed to be the sites of replication of members of the family Reoviridae. Immunocytochemical and biochemical analyses were carried out to characterize the poorly understood viroplasms of the phytoreovirus Rice dwarf virus (RDV). Within 6 h of inoculation of cells, viroplasms, namely discrete cytoplasmic inclusions, were formed that contained the non-structural proteins Pns6, Pns11 and Pns12 of RDV, which appeared to be the constituents of the inclusions. Formation of similar inclusions in non-host insect cells upon expression of Pns12 in a baculovirus system and the association of molecules of Pns12 in vitro suggested that the inclusions observed in RDV-infected cells were composed basically of Pns12. Core proteins P1, P3, P5 and P7 and core virus particles were identified in the interior region of the inclusions. In contrast, accumulation of the outer capsid proteins P2, P8 and P9 and of intact virus particles was evident in the peripheral regions of the inclusions. These observations suggest that core particles were constructed inside the inclusions, whereas outer capsid proteins were assembled at the periphery of the inclusions. Viral inclusions were shown to be the sites of viral RNA synthesis by labelling infected cells with 5-bromouridine 5'-triphosphate. The number of viroplasms decreased with time post-inoculation as their sizes increased, suggesting that inclusions might fuse with one another during the virus-propagation process. Our results are consistent with a model, proposed for vertebrate reoviruses, in which viroplasms play a pivotal role in virus assembly.

Animals↗
PubMed2006

Recurrent childhood anaplastic large cell lymphoma: a retrospective analysis of registered cases in Japan.

This report presents a retrospective study of 26 Japanese children with recurrent anaplastic large cell lymphoma. The first relapses were documented at a median of 10.5 months after the initial diagnosis. Twenty-four patients achieved a second remission. After a median follow-up period of 47 months, 18 patients are still alive: 15 patients are in second complete remission (CR), three patients are in third CR or later. The 5 year overall and relapse-free survival rates were 61 +/- 12% and 51 +/- 12% respectively. The patients who received allogeneic haematopoietic stem cell transplantation during second CR showed a superior outcome to other patients.

Adolescent↗
PubMed2006

Prophylactic therapy for patients with reproductive failure who were positive for anti-phospholipid antibodies.

PROBLEM: To elucidate the efficacy of the treatment using a Japanese-modified Chinese herbal medicine, Sairei-to, and low-dose aspirin with or without a corticosteroid hormone for the patients with adverse pregnancy histories positive for anti-phospholipid antibodies. METHOD OF STUDY: Fifteen cases positive for anti-phospholipid antibodies, who had experienced preterm delivery in which an extremely low birthweight infant (<1000 g) was born as a result of intrauterine growth restriction with or without severe preeclampsia, were treated with the medication according to the current protocol. Four cases with the same condition, who were treated with only low-dose aspirin, or without medication, were chosen as a control population. The pregnancy outcome was compared between the two groups. RESULTS: The rate of patients in whom the next pregnancy continued until the 36th week of gestation or later was significantly higher in treated patients (80.0%) compared with the control population (0%). CONCLUSIONS: In this series, we obtained case report data that Sairei-to may provide some benefit for patients with reproductive disorders positive for anti-phospholipid antibodies; however, randomized controlled trial evidence is needed before current treatment can be recommended.

Adult↗
PubMed2006

The spread of Rice dwarf virus among cells of its insect vector exploits virus-induced tubular structures.

Various cytopathological structures, known as inclusion bodies, are formed upon infection of cultured leafhopper cells by Rice dwarf virus, a member of the family Reoviridae. These structures include tubules of approximately 85 nm in diameter which are composed of the nonstructural viral protein Pns10 and contain viral particles. Such tubular structures were produced in heterologous non-host insect cells that expressed Pns10 of the virus. These tubules, when associated with actin-based filopodia, were able to protrude from the surface of cells and to penetrate neighboring cells. A binding assay in vitro revealed the specific binding of Pns10 to actin. Infection of clusters of cells was readily apparent 5 days after inoculation at a low multiplicity of infection with the virus, even in the presence of neutralizing antibodies. However, treatment of host cells with drugs that inhibited the elongation of actin filaments abolished the extension of Pns10 tubules from the surface of cells, with a significant simultaneous decrease in the extent of infection of neighboring cells. These results together revealed a previously undescribed aspect of the intercellular spread of Rice dwarf virus, wherein the virus exploits tubules composed of a nonstructural viral protein and actin-based filopodia to move into neighboring cells.

Actins↗
PubMed2006

Glycogen synthase kinase 3 and h-prune regulate cell migration by modulating focal adhesions.

h-prune, which has been suggested to be involved in cell migration, was identified as a glycogen synthase kinase 3 (GSK-3)-binding protein. Treatment of cultured cells with GSK-3 inhibitors or small interfering RNA (siRNA) for GSK-3 and h-prune inhibited their motility. The kinase activity of GSK-3 was required for the interaction of GSK-3 with h-prune. h-prune was localized to focal adhesions, and the siRNA for GSK-3 or h-prune delayed the disassembly of paxillin. The tyrosine phosphorylation of focal adhesion kinase (FAK) and the activation of Rac were suppressed in GSK-3 or h-prune knocked-down cells. GSK-3 inhibitors suppressed the disassembly of paxillin and the activation of FAK and Rac. Furthermore, h-prune was highly expressed in colorectal and pancreatic cancers, and the positivity of the h-prune expression was correlated with tumor invasion. These results suggest that GSK-3 and h-prune cooperatively regulate the disassembly of focal adhesions to promote cell migration and that h-prune is useful as a marker for tumor aggressiveness.

Animals↗
PubMed2006

An experience of laser surgery for feto-fetal transfusion syndrome complicated with unexpected feto-fetal hemorrhage in a case of monochorionic triamniotic triplets.

Feto-fetal transfusion syndrome (FFTS) in monochorionic triplets is a rare clinical entity which may share the principal adverse perinatal outcomes of twin-twin transfusion syndrome. Recently, favorable prognoses regarding morbidity and mortality in twins after selective laser photocoagulation of placental communicating vessels (SLPCV) have been described. But descriptions of this procedure in monochorionic triplet cases are limited. This is the case report of an experience of SLPCV applied to monochorionic triamniotic triplets with FFTS. Triplet A had polyhydramnios, while absent end-diastolic flow in the umbilical artery of triplet B, the triplet with anhydramnios, was persistent. Triplet C looked normal, vertical amniotic pocket and Doppler studies yielding normal results. At the beginning of the SLPCV procedure, feto-fetal hemorrhage, subsequent to the fetal death of the donor triplet, occurred. Both surviving cofetuses showed persistent bradycardia; and 1 fetus died while the other recovered from the fetal bradycardia. All vascular anastomoses between the 3 triplets could be identified and obliterated, requiring two trocars. Our fetoscopic observation revealed feto-fetal hemorrhage after demise of monochorionic triplet, which led to injury of other fetuses due to hypovolemia in an instant. In conclusion, SLPCV might be a valid option for FFTS in triplet cases, while further experience is required in order to evaluate the risks and benefits of this procedure in triplet cases.

Adult↗
PubMed2005

Abscisic acid and stress treatment are essential for the acquisition of embryogenic competence by carrot somatic cells.

Studies of carrot embryogenesis have suggested that abscisic acid (ABA) is involved in somatic embryogenesis. A relationship between endogenous ABA and the induction of somatic embryogenesis was demonstrated using stress-induced system of somatic embryos. The embryonic-specific genes C-ABI3 and embryogenic cell proteins (ECPs) were expressed during stress treatment prior to the formation of somatic embryos. The stress-induction system for embryogenesis was clearly distinguished by two phases: the acquisition of embryogenic competence and the formation of a somatic embryo. Somatic embryo formation was inhibited by the application of fluridone (especially at 10(-4) M), a potent inhibitor of ABA biosynthesis, during stress treatment. The inhibitory effect of fluridone was nullified by the simultaneous application of fluridone and ABA. The level of endogenous ABA increased transiently during stress. However, somatic embryogenesis was not significantly induced by the application of only ABA to the endogenous level, in the absence of stress. These results suggest that the induction of somatic embryogenesis, in particular the acquisition of embryogenic competence, is caused not only by the presence of ABA but also by physiological responses that are directly controlled by stresses.

Abscisic Acid↗
PubMed2005

Implication of galectin-3 in Wnt signaling.

Galectin-3 (gal-3), a member of the beta-galactoside-binding proteins family, was identified as a binding partner of beta-catenin. Analysis of the human gal-3 sequence reveled a structural similarity to beta-catenin as it also contains the consensus sequence (S92XXXS96) for glycogen synthase kinase-3beta (GSK-3beta) phosphorylation and can serve as its substrate. In addition, Axin, a regulator protein of Wnt that complexes with beta-catenin, also binds gal-3 using the same sequence motif identified here by a deletion mutant analysis. The data presented here give credence to the suggestion that gal-3 is a key regulator in the Wnt/beta-catenin signaling pathway and highlight the functional similarities between gal-3 and beta-catenin.

Animals↗
PubMed2005

GSK-3beta regulates phosphorylation of CRMP-2 and neuronal polarity.

Neurons are highly polarized and comprised of two structurally and functionally distinct parts, an axon and dendrites. We previously showed that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate, possibly by promoting neurite elongation via microtubule assembly. Here, we showed that glycogen synthase kinase-3beta (GSK-3beta) phosphorylated CRMP-2 at Thr-514 and inactivated it. The expression of the nonphosphorylated form of CRMP-2 or inhibition of GSK-3beta induced the formation of multiple axon-like neurites in hippocampal neurons. The expression of constitutively active GSK-3beta impaired neuronal polarization, whereas the nonphosphorylated form of CRMP-2 counteracted the inhibitory effects of GSK-3beta, indicating that GSK-3beta regulates neuronal polarity through the phosphorylation of CRMP-2. Treatment of hippocampal neurons with neurotrophin-3 (NT-3) induced inactivation of GSK-3beta and dephosphorylation of CRMP-2. Knockdown of CRMP-2 inhibited NT-3-induced axon outgrowth. These results suggest that NT-3 decreases phosphorylated CRMP-2 and increases nonphosphorylated active CRMP-2, thereby promoting axon outgrowth.

Animals↗
PubMed2005

Novel Daple-like protein positively regulates both the Wnt/beta-catenin pathway and the Wnt/JNK pathway in Xenopus.

Wnt signaling pathways are essential in various developmental processes including differentiation, proliferation, cell migration, and cell polarity. Wnt proteins execute their multiple functions by activating distinct intracellular signaling cascades, although the mechanisms underlying this activation are not fully understood. We identified a novel Daple-like protein in Xenopus and named it xDal (Xenopus Daple-like). As with Daple, xDal contains several leucine zipper-like regions (LZLs) and a putative PDZ domain-binding motif, and can interact directly with the dishevelled protein. In contrast to mDaple, injection of xDal mRNA into the dorso-vegetal blastomere does not induce ventralization and acted synergistically with xdsh in secondary axis induction. XDal also induced expression of siamois and xnr-3, suggesting that XDal functions as a positive regulator of the Wnt/beta-catenin pathway. Injection of xDal mRNA into the dorso-animal blastomere, however, induced gastrulation-defective phenotypes in a dose-dependent manner. In addition, xDal inhibited activin-induced elongation of animal caps and enhanced c-jun phosphorylation. Based on these findings, xDal is also thought to function in the Wnt/JNK pathway. Moreover, functional domain analysis with several deletion mutants indicated that xDal requires both a putative PDZ domain-binding motif and at least one LZL for its activity. These findings with xDal will provide new information on the Wnt signaling pathways.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Ubiquitin-interacting motifs of Epsin are involved in the regulation of insulin-dependent endocytosis.

Epsin is a key molecule in receptor-mediated endocytosis. Epsin is phosphorylated and ubiquitinated, and these post-translational modifications are necessary for the regulation of endocytosis. Since human Epsin (hEpsin) has two ubiquitin-interacting motifs (UIMs), we investigated the roles of these UIMs in endocytosis. hEpsin formed a complex with ubiquitinated proteins but did not bind to monoubiquitin. Neither of the two UIMs of hEpsin alone was sufficient to form a complex with ubiquitinated proteins: both UIMs were necessary. Mutations of Asp209 and Asp210 to Ala in UIM (hEpsinDA) abolished the binding activity of hEpsin to ubiquitinated proteins. However, hEpsinDA interacted with Eps15, POB1, and AP-2, which are involved in receptor-mediated endocytosis, as efficiently as wild-type hEpsin. Expression of hEpsinDA in CHO-IR cells affected neither the binding of insulin to nor insulin-dependent autophosphorylation of its receptor. Expression of wild-type hEpsin inhibited the internalization of insulin, whereas that of hEpsinDA did not. These results suggest that the UIM motifs of hEpsin interact with proteins modified with ubiquitin, and that the complex formation is involved in insulin-dependent receptor endocytosis.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Phosphorylation of beta-catenin by cyclic AMP-dependent protein kinase stabilizes beta-catenin through inhibition of its ubiquitination.

The mechanism of cross talk between the Wnt signaling and cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]) pathways was studied. Prostaglandin E(1) (PGE(1)), isoproterenol, and dibutyryl cAMP (Bt(2)cAMP), all of which activate PKA, increased the cytoplasmic and nuclear beta-catenin protein level, and these actions were suppressed by a PKA inhibitor and RNA interference for PKA. PGE(1) and Bt(2)cAMP also increased T-cell factor (Tcf)-dependent transcription through beta-catenin. Bt(2)cAMP suppressed degradation of beta-catenin at the protein level. Although PKA did not affect the formation of a complex between glycogen synthase kinase 3beta (GSK-3beta), beta-catenin, and Axin, phosphorylation of beta-catenin by PKA inhibited ubiquitination of beta-catenin in intact cells and in vitro. Ser675 was found to be a site for phosphorylation by PKA, and substitution of this serine residue with alanine in beta-catenin attenuated inhibition of the ubiquitination of beta-catenin by PKA, PKA-induced stabilization of beta-catenin, and PKA-dependent activation of Tcf. These results indicate that PKA inhibits the ubiquitination of beta-catenin by phosphorylating beta-catenin, thereby causing beta-catenin to accumulate and the Wnt signaling pathway to be activated.

Alprostadil↗
PubMed2005

SUMO-1 modification of PIASy, an E3 ligase, is necessary for PIASy-dependent activation of Tcf-4.

We have previously shown that modification of Tcf-4, a transcription factor in the Wnt pathway, with SUMO by PIASy, a SUMO E3 ligase, enhances its transcriptional activity. Since PIASy itself was also modified with SUMO-1, we studied the role of sumoylation of PIASy in the regulation of Tcf-4. Lys(35) was found to be a sumoylation site of PIASy. PIASy(K35R), in which Lys(35) was mutated to Arg, did not enhance sumoylation of Tcf-4, although this PIASy mutant did not lose the ligase activity of sumoylation for other proteins. Wild-type PIASy and PIASy(K35R) showed a distinct distribution in the nucleus, although both were colocalized with Tcf-4. Promyelocytic leukemia protein, which is involved in transcriptional regulation, was associated with PIASy(K35R) more frequently than wild-type PIASy in the nucleus. PIASy(K35R) could not stimulate the transcriptional activity of Tcf-4 under the conditions in which wild-type PIASy enhanced it. Conjugation of SUMO-1 to the amino terminus of PIASy(K35R) neither enhanced sumoylation of Tcf-4 nor stimulated the transcriptional activity of Tcf-4. These results suggest that sumoylation of Lys(35) in PIASy determines the nuclear localization of PIASy and that it is necessary for PIASy-dependent sumoylation and transcriptional activation of Tcf-4.

Amino Acid Substitution↗
PubMed2005

Aberrations of the CHK2 gene are rare in pediatric solid tumors.

In pediatric solid tumors, such as neuroblastoma (NB), it has been reported that the frequency of TP53 gene alterations is lower than that in adult tumors, suggesting that other tumor suppressor genes may play more important roles in the development of pediatric solid tumors. The CHK2 gene, whose product is a checkpoint kinase that plays a central role in DNA damage response and acts upstream of TP53, has been found to be mutated in a subset of Li-Fraumeni syndrome without mutations of TP53 and in some other sporadic human tumors, earmarking this serine/threonine kinase as a candidate tumor suppressor gene. Thus, we analyzed the CHK2 gene to address whether it is a candidate tumor suppressor gene for pediatric solid tumors. We screened for mutations of the CHK2 gene in 25 NB, 8 rhbdomyosarcoma, 12 Ewing sarcoma, and 26 other pediatric solid tumor cell lines as well as 77 fresh tumors including two cases of multiple cancers. Using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis and reverse transcriptase (RT)-PCR-SSCP followed by direct sequence analysis, we detected only one missense mutation (S505T) in one NB cell line and two silent mutations in one NB cell line and one NB fresh tumor, respectively. Through RT-PCR and subcloning analysis, we detected a similar expression of the CHK2 gene in all of the NB cell lines and fresh tumors; however, we identified at least three isoforms of the CHK2 gene, two of which have not been reported previously. These results suggest that aberrations of the CHK2 gene are rare in pediatric solid tumors.

Base Sequence↗
PubMed2004

The receptor tyrosine kinase Ror2 associates with and is activated by casein kinase Iepsilon.

Ror2, a member of the mammalian Ror family of receptor tyrosine kinases, plays important roles in developmental morphogenesis, although the mechanism underlying activation of Ror2 remains largely elusive. We show that when expressed in mammalian cells, Ror2 associates with casein kinase Iepsilon (CKIepsilon), a crucial regulator of Wnt signaling. This association occurs primarily via the cytoplasmic C-terminal proline-rich domain of Ror2. We also show that Ror2 is phosphorylated by CKIepsilon on serine/threonine residues, in its C-terminal serine/threonine-rich 2 domain, resulting in autophosphorylation of Ror2 on tyrosine residues. Furthermore, it was found that association of Ror2 with CKIepsilon is required for its serine/threonine phosphorylation by CKIepsilon. Site-directed mutagenesis of tyrosine residues in Ror2 reveals that the sites of phosphorylation are contained among the five tyrosine residues in the proline-rich domain but not among the four tyrosine residues in the tyrosine kinase domain. Moreover, we show that in mammalian cells, CKIepsilon-mediated phosphorylation of Ror2 on serine/threonine and tyrosine residues is followed by the tyrosine phosphorylation of G protein-coupled receptor kinase 2, a kinase with a developmental expression pattern that is remarkably similar to that of Ror2. Intriguingly, a mutant of Ror2 lacking five tyrosine residues, including the autophosphorylation sites, fails to tyrosine phosphorylate G protein-coupled receptor kinase 2. This indicates that autophosphorylation of Ror2 is required for full activation of its tyrosine kinase activity. These findings demonstrate a novel role for CKIepsilon in the regulation of Ror2 tyrosine kinase.

3T3 Cells↗