Biomedical subjects

M Shimizu

Publications and source records attributed to M Shimizu.

At least 19 recordsLinked to original sources

PubMed2001

Effects of maternal age on teratogenicity of di-n-butyltin diacetate in rats.

The present study was designed to assess changes in the teratogenic potency of di-n-butyltin diacetate (DBTA) with increasing maternal age in rats. Pregnant Wistar rats of 3, 7.5 or 12 months were treated orally with DBTA at 0, 7.5, 10, 15 or 22 mg/kg on day 8 of gestation. Cesarean sections were performed on day 20 of gestation. Maternal age had greater impact on litter size in the 7.5- and 12-month dams than the 3-month dams. The death of most of the fetuses of the 12-month dams made it difficult to evaluate the teratogenic potency of DBTA. In 3-month groups, fetuses with external malformation, such as cleft mandible, cleft lower lip, ankyloglossia and/or schistoglossia, which are malformations typical of DBTA, were observed at 15 and 22 mg/kg, while similar malformations were observed in 7.5-month groups at doses of 10 mg/kg and above. At 15 and 22 mg/kg, the incidences of these malformations in 7.5-month groups were similar to these from 3-month groups. In our previous studies, however, single DBTA-treatment at 10 mg/kg on day 8 of gestation has not produced such malformations from 3-month dams. The results suggest that the teratogenic potency of DBTA in 7.5-month dams may be greater than in 3-month dams.

Abnormalities, Drug-Induced↗

PubMed2001

Synthetic activity of Sso DNA polymerase Y1, an archaeal DinB-like DNA polymerase, is stimulated by processivity factors proliferating cell nuclear antigen and replication factor C.

DNA replication efficiency is dictated by DNA polymerases (pol) and their associated proteins. The recent discovery of DNA polymerase Y family (DinB/UmuC/RAD30/REV1 superfamily) raises a question of whether the DNA polymerase activities are modified by accessory proteins such as proliferating cell nuclear antigen (PCNA). In fact, the activity of DNA pol IV (DinB) of Escherichia coli is enhanced upon interaction with the beta subunit, the processivity factor of DNA pol III. Here, we report the activity of Sso DNA pol Y1 encoded by the dbh gene of the archaeon Sulfolobus solfataricus is greatly enhanced by the presence of PCNA and replication factor C (RFC). Sso pol Y1 per se was a distributive enzyme but a substantial increase in the processivity was observed on poly(dA)-oligo(dT) in the presence of PCNA (039p or 048p) and RFC. The length of the synthesized DNA product reached at least 200 nucleotides. Sso pol Y1 displayed a higher affinity for DNA compared with pol IV of E. coli, suggesting that the two DNA polymerases have distinct reason(s) to require the processivity factors for efficient DNA synthesis. The abilities of pol Y1 and pol IV to bypass DNA lesions and their sensitive sites to protease are also discussed.

Amino Acid Sequence↗

PubMed2001

Direct demonstration of rapid degradation of nuclear sterol regulatory element-binding proteins by the ubiquitin-proteasome pathway.

Sterol regulatory element-binding proteins (SREBPs) are synthesized as membrane-bound precursors and processed to generate transcriptionally active forms. The active SREBPs translocate to the nucleus, induce the expression of responsive genes, and are degraded very rapidly. Treatment with proteasome inhibitors elevates the amount of the endogenous nuclear SREBPs, but not the precursors, in HeLa cells. Nuclear forms of human SREBP-1a (amino acids 1-487) and SREBP-2 (amino acids 1-481), which are transiently expressed in stable Chinese hamster ovary cell lines (CHO-487 and -481), are also stabilized by proteasome inhibitors, suggesting that the nuclear SREBPs are likely to be substrates for the proteasome-dependent proteolysis. The stabilized nuclear SREBPs actively induce the expression of responsive genes including hydroxymethylglutaryl (HMG)-CoA synthase, fatty acid synthase, and the low density lipoprotein receptor. The rapid turnover of nuclear SREBP-1a is not affected by the intracellular sterol levels, and the half-life is estimated to be approximately 3 h. The nuclear SREBPs are found conjugated with a polyubiquitin chain. When this conjugation is inhibited by overexpression of mutant ubiquitin that is defective in polyubiquitination, the nuclear SREBPs are partly stabilized and induce the expression of the responsive gene, suggesting that the ubiquitin-conjugated SREBPs are substrates for the proteasome. Taken together, these results demonstrate that the ubiquitin-proteasome system degrades SREBPs and that this system controls the expression of SREBP-responsive genes.

Animals↗

PubMed2001

A C-terminal segment with properties of alpha-helix is essential for DNA binding and in vivo function of zinc finger protein Rme1p.

Rme1p plays important roles in the control of meiosis and in cell cycle progression through binding to upstream regions of IME1 and CLN2 in Saccharomyces cerevisiae. Rme1p has three zinc finger segments, and two of them are atypical. To determine DNA binding domain of Rme1p, a series of Rme1p derivatives fused with maltose-binding protein were purified and characterized by gel mobility shift assay. We show that not only three zinc fingers, but also the neighboring C-terminal region is essential for DNA binding. Mutational analysis of this region revealed that basic residues Arg-287, Lys-290, and Arg-291 and the hydrophobic residues Phe-288, Leu-292, Ile-295, and Leu-296 are critical for DNA binding. In addition, double substitutions by proline at Asn-289 and Lys-293, each of which was not essential for DNA binding, abolished DNA binding. These results suggest that the C-terminal segment forms an amphipathic helical structure. Furthermore, it was shown that the mutations in the important basic residues abolish or impair Rme1p function in vivo for repression and inhibition of spore formation. Thus, the C-terminal segment is essential and acts as a novel accessory domain for DNA binding by zinc fingers.

Amino Acid Sequence↗

PubMed2001

Nickel-catalyzed intramolecular homoallylation of omega-dienyl aldehyde.

[reaction: see text] In the presence of a catalytic amount of Ni(acac)(2), Et(3)B and Et(2)Zn nicely promote a reductive homoallylic cyclization of omega-dienyl aldehydes and provide 2-allylcyclopentanols and -cyclohexanols with high stereoselectivity in excellent yield. The reaction requires only two kinds of commercially available, inexpensive reagents, Ni(acac)(2) and Et(2)Zn or Et(3)B, and completes at room temperature within 30 min with Et(2)Zn and 1-2 days with Et(3)B. No ligand additives (e.g., phosphine, nitrogen compounds) are required.

Journal Article↗

PubMed2001

Role of stem cell factor and c-kit signaling in regulation of fetal intestinal epithelial cell adhesion to fibronectin.

The interaction of stem cell factor (SCF) and c-kit is considered to be an important signaling event for the homeostasis of the epithelial barrier function in the intestinal tract. This study was designed to investigate the role of the SCF and c-kit signaling pathway in adhesion of intestinal epithelial cells (IECs) to fibronectin (FN) using primary cells. Fetal murine IECs were prepared from the small intestine of mouse fetus. The mRNAs coding for SCF in mesenchymes and c-kit in IECs were detected by reverse transcription-PCR. The expression of FN receptor VLA-5 on IECs was examined by flow cytometry. A cell adhesion assay showed that the stimulation of IECs with SCF increased the number of cells adhering to FN. Experiments using specific antibody against SCF indicated that this increase in cell adhesion was SCF-dependent. On the other hand, SCF did not influence the expression of VLA-5 on IECs. The IEC adhesion to FN was inhibited by specific antibody against the FN receptor (VLA-5), as well as competitive Arg-Gly-Asp (RGD) peptide. When alteration of intracellular signal transduction induced by SCF was examined, it was found that SCF stimulated a tyrosine-specific c-kit autophosphorylation cascade of IECs. Further, preincubation of IECs with an optimal concentration of genistein resulted in the inhibition of SCF-induced c-kit phosphorylation and adhesion of IECs to FN. These results suggested that adhesion of immature IECs to FN is regulated by activation of RGD-dependent VLA-5 through the SCF and c-kit signal transduction pathway. SCF, which may be produced by mesenchymes locally, is an important regulatory factor for the adhesion of immature IECs to basement membrane matrix via VLA-5 and FN interaction. This cytokine-regulated interaction between VLA-5 and FN may play an important role in the development and wound repair of the intestinal tract.

Animals↗

PubMed2001

Proteolytic activation of SREBPs during adipocyte differentiation.

A member of sterol regulatory element-binding protein (SREBP) family, SREBP-1, is a key regulator of adipocyte differentiation. Expression of the SREBP-1 gene is induced during adipocyte differentiation, but proteolytic activation of the synthesized precursor form of SREBP-1 has not been well analyzed. The proteolytic processing of SREBPs is severely suppressed in sterol loaded culture cells. Here we report that a splicing isoform, SREBP-1a, is predominantly expressed in 3T3-L1 preadipocytes and adipocytes, and that the nuclear active form of SREBP-1 protein increases in adipocyte differentiation. We further show that the amount of nuclear SREBP-2 protein also increases despite no increase in SREBP-2 mRNA, suggesting that proteolytic cleavage of SREBPs is induced in lipid loaded adipocytes. Northern blot analyses reveal that mRNA levels for SREBP cleavage-activating protein (SCAP), Site-1 protease (S1P), and Site-2 protease (S2P), which participate in the proteolytic processing of SREBPs, are relatively unaffected in adipogenesis. These results demonstrate that SREBP-2 appears to promote adipocyte differentiation as well as SREBP-1 and that the proteolytic activation of SREBPs may be induced by an as-yet unidentified mechanism in lipid loaded adipocytes.

3T3 Cells↗

PubMed2001

A DAF-1-binding protein BRA-1 is a negative regulator of DAF-7 TGF-beta signaling.

We have identified homologs of a human BMP receptor-associated molecule BRAM1 in Caenorhabditis elegans. One of them, BRA-1, has been found to bind DAF-1, the type I receptor in the DAF-7 transforming growth factor-beta pathway through the conserved C-terminal region. As analyzed using a BRA-1GFP (green fluorescent protein) fusion gene product, the bra-1 gene is expressed in amphid neurons such as ASK, ASI, and ASG, where daf-1 is also expressed. A loss-of-function mutation in bra-1 exhibits robust suppression of the Daf-c phenotype caused by the DAF-7 pathway mutations. We propose that BRA-1 represents a novel class of receptor-associated molecules that negatively regulate transforming growth factor-beta pathways.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Prognostic significance of combined conventional and immunocytochemical cytology for peritoneal washings in endometrial carcinoma.

BACKGROUND: Noncancerous cells simulating adenocarcinoma cells may interfere with the analysis of peritoneal cytology (PC) in patients with endometrial carcinoma. Immunocytochemistry (ICC) may improve the diagnosis of PC. METHODS: PC slides from 115 patients with endometrial carcinoma were reviewed. Suspicious or positive cell clusters were recovered with a cell transfer method and were subjected to ICC for MOC-31, cytokeratin 5/6, and p53. Conventional Papanicolaou staining and ICC results were compared directly on the same cells. RESULTS: By combined conventional and immunocytochemical PC (CONV-ICC-PC), cytodiagnosis was positive in 18 of 115 patients (15.7%) and suspicious in 3 of 115 patients (2.6%). According to a multivariate Cox regression analysis of patients with tumors confined to the uterus that included grade, myometrial invasion, cervical involvement, and CONV-ICC-PC, only CONV-ICC-PC was an independent prognostic factor (P < 0.05). A multivariate analysis for all of the patients studied that compared CONV-ICC-PC with staging variables revealed that only peritoneal metastasis (P < 0.0001) and lymph node metastasis (P < 0.01) were independent prognostic factors. When peritoneal metastases were excluded, CONV-ICC-PC (P < 0.01) and lymph node metastasis (P < 0.0025) were the independent prognostic factors. By cell transfer and p53 immunostaining in samples from 14 patients with malignant cells in their peritoneal washings, no deaths occurred among 5 patients with negative p53, whereas 5 of 9 patients with positive p53 died of disease at the time of data analysis. CONCLUSIONS: MOC-31 immunostaining improves the diagnosis of PC in endometrial carcinoma. Positive PC is an important prognostic factor for patients with endometrial carcinoma confined to the uterus. The p53 positive cells in PC have possible prognostic significance.

Adult↗

PubMed2001

Reactions of PhSCH(2)Li and NCCH(2)Li with benzaldehyde and benzophenone: when does the mechanism change from ET to polar?

The carbonyl-carbon kinetic isotope effect (KIE) and the substituent effect were measured for the reaction of phenylthiomethyllithium (PhSCH(2)Li, 1) with benzaldehyde and benzophenone, and cyanomethyllithium (NCCH(2)Li, 2) with benzaldehyde, and the results were compared with those for other lithium reagents such as MeLi, PhLi, CH(2)=CHCH(2)Li, and CH(2)=C(OLi)C(CH(3))(3). It was previously shown that the reactions of MeLi, PhLi, and CH(2)=CHCH(2)Li proceed via a rate-determining electron transfer (ET) process whereas the reaction of lithium pinacolone enolate goes through the polar (PL) mechanism. The reaction of 1 with benzaldehyde gave no carbonyl-carbon KIE ((12)k/(13)k = 0.999 +/- 0.004), similar to that measured previously for the MeLi reaction with benzophenone ((12)k/(14)k = 1.000). The effect of substituents of the aromatic ring of benzaldehyde and benzophenone on the reactivity gave very small Hammett rho values of 0.17 +/- 0.03 and 0.26 +/- 0.05, respectively. These small rho values are again similar to that observed for the reaction of MeLi. Likewise the reactions of 2 with benzaldehydes gave small KIE and the rho value ((12)k/(13)k = 0.996 +/- 0.004, rho = 0.14 +/- 0.02). Dehalogenation and enone-isomerization probe experiments for 2 showed no evidence for the presence of radical-ion pair of sufficient lifetime during the course of the reaction. It is concluded that the reactions of 1 and 2 with the aromatic carbonyl compounds proceed via the electron transfer-radical coupling mechanism with rate-determining ET as in the reactions of MeLi, PhLi, and CH(2)=CHCH(2)Li.

Journal Article↗

PubMed2001

Atypical protein kinase C is involved in the evolutionarily conserved par protein complex and plays a critical role in establishing epithelia-specific junctional structures.

We have previously shown that during early Caenorhabditis elegans embryogenesis PKC-3, a C. elegans atypical PKC (aPKC), plays critical roles in the establishment of cell polarity required for subsequent asymmetric cleavage by interacting with PAR-3 [Tabuse, Y., Y. Izumi, F. Piano, K.J. Kemphues, J. Miwa, and S. Ohno. 1998. Development (Camb.). 125:3607--3614]. Together with the fact that aPKC and a mammalian PAR-3 homologue, aPKC-specific interacting protein (ASIP), colocalize at the tight junctions of polarized epithelial cells (Izumi, Y., H. Hirose, Y. Tamai, S.-I. Hirai, Y. Nagashima, T. Fujimoto, Y. Tabuse, K.J. Kemphues, and S. Ohno. 1998. J. Cell Biol. 143:95--106), this suggests a ubiquitous role for aPKC in establishing cell polarity in multicellular organisms. Here, we show that the overexpression of a dominant-negative mutant of aPKC (aPKCkn) in MDCK II cells causes mislocalization of ASIP/PAR-3. Immunocytochemical analyses, as well as measurements of paracellular diffusion of ions or nonionic solutes, demonstrate that the biogenesis of the tight junction structure itself is severely affected in aPKCkn-expressing cells. Furthermore, these cells show increased interdomain diffusion of fluorescent lipid and disruption of the polarized distribution of Na(+),K(+)-ATPase, suggesting that epithelial cell surface polarity is severely impaired in these cells. On the other hand, we also found that aPKC associates not only with ASIP/PAR-3, but also with a mammalian homologue of C. elegans PAR-6 (mPAR-6), and thereby mediates the formation of an aPKC-ASIP/PAR-3-PAR-6 ternary complex that localizes to the apical junctional region of MDCK cells. These results indicate that aPKC is involved in the evolutionarily conserved PAR protein complex, and plays critical roles in the development of the junctional structures and apico-basal polarization of mammalian epithelial cells.

Actins↗

PubMed2001

A risk-stratification model of non-small cell lung cancers using cyclin E, Ki-67, and ras p21: different roles of G1 cyclins in cell proliferation and prognosis.

A large number of biological factors that seem to have important prognostic significance have been identified in non-small cell lung cancers (NSCLCs). In the present study, we have characterized expression of cyclin D1 and cyclin E in a cohort of 217 resected NSCLCs from a single institution by immunohistochemistry to analyze their expression in relation to the growth fraction determined by Ki-67 and to prognosis, and then we have constructed a risk-stratification model of cancer death by multiple biological factors in p-stage I NSCLCs. The cyclin E labeling index (LI) was significantly associated with the Ki-67 LI (r = 0.45; P < 0.001). Tumors having high-level cyclin E expression (cyclin E LI > or =30%) showed a significantly higher Ki-67 LI than tumors having low-level cyclin E expression (cyclin E LI <30%; P < 0.001), whereas positive or negative cyclin D1 expression was not associated with the Ki-67 LI (P = 0.1). Cyclin E expression was a significant and independent unfavorable prognostic factor (hazards ratio = 2.09; P = 0.03), as reported previously (Clin. Cancer Res., 6: 11-16, 2000), whereas cyclin D1 expression was not. These findings indicate different roles of cyclin D1 and cyclin E in cell proliferation and in the prognosis of NSCLCs. Furthermore, we stratified this cohort of p-stage I NSCLCs into different survival groups by using biological factors, including cyclin E, Ki-67, and ras p21, which previously we have found to be independent prognostic factors among 10 factors studied in p-stage I NSCLCs. Four groups of patients with markedly different survivals were identified with 5-year survival rates that ranged from 96% for patients with no factors altered to 41% for patients with all three factors altered (P < 0.001). This combination of biological factors was a significant and independent prognostic factor (hazards ratio = 7.94; P = 0.001).

Aged↗

PubMed2001

Sequential analysis of morphological and biological properties of beta-catenin-accumulated crypts, provable premalignant lesions independent of aberrant crypt foci in rat colon carcinogenesis.

Our previous study (Cancer Res., 60: 3323-3327, 2000) showed that frequent beta-catenin gene mutations are present in beta-catenin-accumulated crypts, which occur early in rodent colonic carcinogenesis, with a lack of the appearance of aberrant crypt foci (ACF). To clarify the nature of such lesions, we performed a sequential analysis of the morphological and biological properties of beta-catenin-accumulated crypts. Azoxymethane was administered s.c. to male F344 rats (15 mg/kg body weight) once a week for 3 weeks, and the animals were sacrificed at 5, 10, and 20 weeks after the carcinogen treatment. Both the number of crypts/lesion and the diameter of beta-catenin-accumulated crypts were significantly increased with time courses of 5, 10, and 20 weeks from carcinogen exposure (P < 0.01). Likewise, the histological abnormality in those crypts, assessed by semiquantitative analyses, was also increased with time (P < 0.01). Conversely, ACF did not show any increase in histological abnormality during the time course and maintained a monotonous histology throughout the experiment. The histological abnormality score for beta-catenin-accumulated crypts was significantly higher than for ACF at every time point (P < 0.001). The number of AgNOR/nucleus in beta-catenin-accumulated crypts was significantly higher than in ACF (P < 0.001). Beta-catenin-accumulated crypts were accompanied frequently by Paneth cells and had decreased hexosaminidase activity. Such data, together with the results in our previous report, strongly suggest that beta-catenin-accumulated crypts, which are independent of ACF, are truly premalignant lesions for colon cancer.

Animals↗

PubMed2001

Characterization of blood group ABO(H)-active gangliosides in type AB erythrocytes and structural analysis of type A-active ganglioside variants in type A human erythrocytes.

Several monosialogangliosides containing the type A-active epitope have been detected in type A erythrocytes on immunological analysis with a monoclonal antibody, and three of them were purified by repeated silica bead column chromatography and by scraping from the TLC plate. Two of these A-active gangliosides were characterized by methylation analysis by GC/MS, negative SIMS, MALDI-TOF/MS, proton nuclear magnetic resonance spectroscopy, and immunological assays, and their structures were concluded to be as follows. A-active ganglioside I:A-active ganglioside II:The reactivity of the purified gangliosides to the anti-A monoclonal antibodies (mAbs) exhibited enhancement after removal of the sialic acid. Therefore, the sialic residue has been shown to inhibit the binding to the terminal A-active epitope through the formation of an immune complex. To confirm the presence of A- (including S-A-I, -II and -III) and B-active gangliosides, the reactivity of anti-A and -B mAbs were investigated using total gangliosides from type A, -B and -AB erythrocytes on TLC plate. The results were that the gangliosides from types A and AB showed positive reaction to anti-A mAbs, whereas in the anti-B mAbs binding the gangliosides from types B and AB were positive. Thus, it revealed that A-active gangliosides were present in type A and -AB, and B-active gangliosides in types B and AB. As there was no difference in respective gangliosides on type AB erythrocytes of 22 individuals, both A- and B-active gangliosides are equally present in type AB erythrocytes. The biological significance of these A- and B-active ganglioside variants remains vague at present. As these molecules exhibit different reactivities to the anti-A mAbs, it is very likely that they can regulate the antigenicity of the A-epitope on the cell surface.

ABO Blood-Group System↗

PubMed2001

Damaged DNA-binding protein DDB stimulates the excision of cyclobutane pyrimidine dimers in vitro in concert with XPA and replication protein A.

Human cells contain a protein that binds to UV-irradiated DNA with high affinity. This protein, damaged DNA-binding protein (DDB), is a heterodimer of two polypeptides, p127 and p48. Recent in vivo studies suggested that DDB is involved in global genome repair of cyclobutane pyrimidine dimers (CPDs), but the mechanism remains unclear. Here, we show that in vitro DDB directly stimulates the excision of CPDs but not (6-4)photoproducts. The excision activity of cell-free extracts from Chinese hamster AA8 cell line that lacks DDB activity was increased 3-4-fold by recombinant DDB heterodimer but not p127 subunit alone. Moreover, the addition of XPA or XPA + replication protein A (RPA), which themselves enhanced excision, also enhanced the excision in the presence of DDB. DDB was found to elevate the binding of XPA to damaged DNA and to make a complex with damaged DNA and XPA or XPA + RPA as judged by both electrophoretic mobility shift assays and DNase I protection assays. These results suggest that DDB assists in the recognition of CPDs by core NER factors, possibly through the efficient recruitment of XPA or XPA.RPA, and thus stimulates the excision reaction of CPDs.

Base Sequence↗

PubMed2001

Acute effects of ovariectomy on wound healing of alveolar bone after maxillary molar extraction in aged rats.

Acute effects of ovariectomy on the bone wound healing processes after maxillary molar extraction in aged rats were examined by means of quantitative scanning electron microscopy (SEM), backscattered electron image (BSE) analysis and energy-dispersive X-ray (EDX) microanalysis. Six-month-old female rats underwent either sham operation or bilateral ovariectomy, and 7 days postoperatively, the maxillary first molars were extracted. On post-extraction days 7, 30 and 60, the dissected maxillary bone surfaces were examined by SEM to reveal the bone formative and resorptive areas around the extracted alveolar sockets. In addition, the resin-embedded maxillae were micromilled in the transverse direction through the extracted alveolar sockets, and the newly-formed bone mass on the buccal bone surfaces and within the extracted sockets was examined by BSE analysis. Compared with sham-operated controls, the extent of newly-formed bone mass on the buccal bone surfaces in OVX rats was significantly decreased, due to increased bone resorption. On the other hand, new bone formation within the extracted sockets was similar in the experimental groups. In EDX microanalysis of these newly-formed bone matrices, both Ca and P weight % and Ca/P molar ratio were similar in the experimental groups. Our results suggest that 1) acute estrogen deficiency induced by ovariectomy stimulates sustained bone resorption, but has less effect on bone formation, and 2) bone wound healing after maxillary molar extraction within extracted alveolar sockets is not significantly delayed by ovariectomy, but bony support by newly-formed bone mass on the maxillary bone surfaces at the buccal side of the extracted sockets is significantly decreased, due to increased bone resorption.

Acute Disease↗

PubMed2001

Involvement of the pro-oncoprotein TLS (translocated in liposarcoma) in nuclear factor-kappa B p65-mediated transcription as a coactivator.

In this study, we have demonstrated that translocated in liposarcoma (TLS), also termed FUS, is an interacting molecule of the p65 (RelA) subunit of the transcription factor nuclear factor kappaB (NF-kappaB) using a yeast two-hybrid screen. We confirmed the interaction between TLS and p65 by the pull-down assay in vitro and by a coimmunoprecipitation experiment followed by Western blot of the cultured cell in vivo. TLS was originally identified as part of a fusion protein with CHOP arising from chromosomal translocation in human myxoid liposarcomas. TLS has been shown to be involved in TFIID complex formation and associated with RNA polymerase II. However, the role of TLS in transcriptional regulation has not yet been clearly elucidated. We found that TLS enhanced the NF-kappaB-mediated transactivation induced by physiological stimuli such as tumor necrosis factor alpha, interleukin-1beta, and overexpression of NF-kappaB-inducing kinase. TLS augmented NF-kappaB-dependent promoter activity of the intercellular adhesion molecule-1 gene and interferon-beta gene. These results suggest that TLS acts as a coactivator of NF-kappaB and plays a pivotal role in the NF-kappaB-mediated transactivation.

Cell Line↗

PubMed2001

Inhibition of cytochrome c release in Fas-mediated signaling pathway in transgenic mice induced to express hepatitis C viral proteins.

Persistent hepatitis C virus (HCV) infection often progresses to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Numerous viruses have been reported to escape from apoptotic mechanism to maintain persistent infection. In the present study, we characterized the effect of HCV proteins on the Fas signal using HCV transgenic mice, which expressed core, E1, E2, and NS2 proteins, regulated by the Cre/loxP switching system. The transgene expression of HCV transgenic mice caused resistance to Fas antibody stimulated lethality. Apoptotic cell death in the liver of HCV protein expressing mice was significantly reduced compared with nonexpressing mice. Histopathological analysis and DNA fragmentation analysis revealed that the HCV proteins suppressed Fas-mediated apoptotic cell death. To identify the target pathway of HCV proteins, we characterized caspase activity. The activation of caspase-9 and -3/7 but not caspase-8 was inhibited by HCV proteins. Cytochrome c release from mitochondria was inhibited in HCV protein expressing mice. These results indicated that the expression of HCV proteins may directly or indirectly inhibit Fas-mediated apoptosis and death in mice by repressing the release of cytochrome c from mitochondria, thereby suppressing caspase-9 and -3/7 activation. These results suggest that HCV may cause persistent infection, as a result of suppression of Fas-mediated cell death.

Animals↗