Biomedical subjects

Minoru Yoshida

Publications and source records attributed to Minoru Yoshida.

At least 109 records · Page 6Linked to original sources

PubMed2002

E3 ubiquitin ligase that recognizes sugar chains.

N-glycosylation of proteins in the endoplasmic reticulum (ER) has a central role in protein quality control. Here we report that N-glycan serves as a signal for degradation by the Skp1-Cullin1-Fbx2-Roc1 (SCF(Fbx2)) ubiquitin ligase complex. The F-box protein Fbx2 (ref. 4) binds specifically to proteins attached to N-linked high-mannose oligosaccharides and subsequently contributes to ubiquitination of N-glycosylated proteins. Pre-integrin beta 1 is a target of Fbx2; these two proteins interact in the cytosol after inhibition of the proteasome. In addition, expression of the mutant Fbx2 Delta F, which lacks the F-box domain that is essential for forming the SCF complex, appreciably blocks degradation of typical substrates of the ER-associated degradation pathway. Our results indicate that SCF(Fbx2) ubiquitinates N-glycosylated proteins that are translocated from the ER to the cytosol by the quality control mechanism.

Animals↗

PubMed2002

Maternal-to-fetus transfer of mercury in metallothionein-null pregnant mice after exposure to mercury vapor.

This study examined the role of placenta metallothionein (MT) in maternal-to-fetal mercury transfer in MT-null and wild-type mice after exposure to elemental mercury (Hg(0)) vapor. Both strains were exposed to Hg(0) vapor at 5.5-6.7 mg/m(3) for 3 h during late gestation. Twenty-four hours after exposure to Hg(0) vapor, accumulation of mercury in the major organs, except the brain, of MT-null maternal mice was significantly lower than that in organs of wild-type mice. In contrast to mercury levels in maternal organs, fetal mercury levels were significantly higher in MT-null mice than in wild-type mice. In placenta, mercury concentrations were not significantly different between the two strains. Although MT levels in major organs, except the brain, of wild type mice were markedly elevated after the exposure to Hg(0) vapor, the placental MT levels were not elevated. However, endogenous MT level in the placenta is significantly higher than that in other organs, except the liver. Gel filtration profile of the placental cytosol in the wild-type mice revealed that a large amount of placental mercury was associated with MT. In MT-null mice, mercury in placental cytosol appeared mainly in the high-molecular-weight protein fractions. Mercury in the placenta was localized mainly in the yolk sac and decidual cells in the deep layer of the decidua in both mouse strains. The similar localization of MT was found in the placenta of wild type mice. These results suggest that MT in the placenta has a defensive role in preventing maternal-to-fetal mercury transfer.

Administration, Inhalation↗

PubMed2002

HDAC6 is a microtubule-associated deacetylase.

Reversible acetylation of alpha-tubulin has been implicated in regulating microtubule stability and function. The distribution of acetylated alpha-tubulin is tightly controlled and stereotypic. Acetylated alpha-tubulin is most abundant in stable microtubules but is absent from dynamic cellular structures such as neuronal growth cones and the leading edges of fibroblasts. However, the enzymes responsible for regulating tubulin acetylation and deacetylation are not known. Here we report that a member of the histone deacetylase family, HDAC6, functions as a tubulin deacetylase. HDAC6 is localized exclusively in the cytoplasm, where it associates with microtubules and localizes with the microtubule motor complex containing p150(glued) (ref. 3). In vivo, the overexpression of HDAC6 leads to a global deacetylation of alpha-tubulin, whereas a decrease in HDAC6 increases alpha-tubulin acetylation. In vitro, purified HDAC6 potently deacetylates alpha-tubulin in assembled microtubules. Furthermore, overexpression of HDAC6 promotes chemotactic cell movement, supporting the idea that HDAC6-mediated deacetylation regulates microtubule-dependent cell motility. Our results show that HDAC6 is the tubulin deacetylase, and provide evidence that reversible acetylation regulates important biological processes beyond histone metabolism and gene transcription.

3T3 Cells↗

PubMed2002

Stat5B shuttles between cytoplasm and nucleus in a cytokine-dependent and -independent manner.

In response to cytokine stimuli, Stats are phosphorylated and translocated to the nucleus to activate target genes. Then, most are dephosphorylated and returned to the cytoplasm. Using Ba/F3 cells, we found that the nuclear export of Stat5B by cytokine depletion was inhibited by leptomycin B (LMB), a specific inhibitor of nuclear export receptor chromosome region maintenance 1. Interestingly, LMB treatment in the absence of cytokine led to the accumulation of Stat5B in the nucleus, suggesting that Stat5B shuttles between the nucleus and the cytoplasm as a monomer without cytokine stimulation. This notion is supported by the observation that LMB-induced accumulation of Stat5B in the nucleus was also observed with Stat5B having a mutated tyrosine 699, which is essential for dimer formation. Using a series of mutant Stat5Bs, we identified a part of the coiled coil domain to be a critical region for monomer nuclear import and a more N-terminal region to be critical for the cytokine stimulation dependent import of Stat5B. Taken together, we propose a model in which Stat5B shuttles between the nucleus and cytoplasm by two different mechanisms, one being a factor-independent constitutive shuttling by monomeric form, and the other, a factor stimulation-dependent one regulated by tyrosine phosphorylation and subsequent dimerization.

Active Transport, Cell Nucleus↗

PubMed2002

Phosphorylation of p27Kip1 on serine 10 is required for its binding to CRM1 and nuclear export.

Phosphorylation of the cyclin-dependent kinase inhibitor p27(Kip1) has been thought to regulate its stability. Ser(10) is the major phosphorylation site of p27(Kip1), and phosphorylation of this residue affects protein stability. Phosphorylation of p27(Kip1) on Ser(10) has now been shown to be required for the binding of CRM1, a carrier protein for nuclear export. The p27(Kip1) protein was translocated from the nucleus to the cytoplasm at the G(0)-G(1) transition of the cell cycle, and this export was inhibited by leptomycin B, a specific inhibitor of CRM1-dependent nuclear export. The nuclear export and subsequent degradation of p27(Kip1) at the G(0)-G(1) transition were observed in cells lacking Skp2, the F-box protein component of an SCF ubiquitin ligase complex, indicating that these early events are independent of Skp2-mediated proteolysis. Substitution of Ser(10) with Ala (S10A) markedly reduced the extent of p27(Kip1) export, whereas substitution of Ser(10) with Asp (S10D) or Glu (S10E) promoted export. Co-immunoprecipitation analysis showed that CRM1 preferentially interacted with S10D and S10E but not with S10A, suggesting that the phosphorylation of p27(Kip1) on Ser(10) is required for its binding to CRM1 and for its subsequent nuclear export.

3T3 Cells↗

PubMed2002

Comprehensive mutational analysis of the VHL gene in sporadic renal cell carcinoma: relationship to clinicopathological parameters.

To delineate more precisely the somatic von Hippel-Lindau disease (VHL) gene alteration as well as to elucidate its etiologic role in renal tumorigenesis, we examined a total of 240 sporadic renal cell carcinomas (RCCs) for somatic VHL gene alterations by DNA-SSCP followed by sequencing, methylation-specific PCR assay, microsatellite LOH study, and Southern blot analysis. Intragenic mutation of the VHL gene was found exclusively in clear-cell or variant-type RCCs at a frequency of 51% (104/202). Hypermethylation of the VHL promoter region was detected in an additional 11 clear-cell RCCs. Microsatellite analysis demonstrated that LOH of the VHL locus was found in 140/155 (90%) informative clear-cell RCCs. The VHL gene therefore seems to be inactivated in a two-hit manner by intragenic mutation or hypermethylation plus allelic loss in clear-cell RCC. Genomic rearrangement of the VHL gene detected by Southern analysis was not found (0/216 cases); this is in contrast to germ lines in which Southern aberrations consisted of 7-19% of the mutations. Clinicopathologic data demonstrated that VHL mutation/LOH did not vary according to tumor progression in clear-cell RCC, including tumor diameter, stage, grading, distant metastasis, and lymph node metastasis. Interestingly, VHL mutation was significantly less frequent in RCCs occurring in younger (< or = 55 years) than that in older (> or = 56 years) patients. These data suggested that the inactivation of the VHL tumor-suppressor gene is a specific genetic change in clear-cell RCC, and that it may occur at an early or first step in the clear-cell tumorigenic pathway rather than as a late event.

Adult↗

PubMed2002

Somatic von Hippel-Lindau disease gene mutation in clear-cell renal carcinomas associated with end-stage renal disease/acquired cystic disease of the kidney.

It has been documented that renal cell carcinomas (RCCs) occur frequently in patients treated with long-term dialysis, especially in cases of end-stage renal disease (ESRD)/acquired cystic disease of the kidney (ACDK). To address the molecular pathogenesis of ESRD/ACDK-associated RCCs, we examined 14 RCCs (7 clear-cell and 7 papillary carcinomas) in patients receiving dialysis for somatic mutations of the von Hippel-Lindau disease (VHL) gene as well as of the tyrosine kinase domain of the MET oncogene. Direct sequencing analyses revealed that three tumors exhibited VHL frameshifts (618delA, 386-395del10-bp, and 723-724insTC). One of the VHL mutated tumors showed additional loss of heterozygosity at the VHL gene locus. Histopathologic and clinical data demonstrated that the three tumors having VHL mutations were clear-cell RCCs occurring in ESRD with 55, 106, and 156 months of dialysis history, respectively. We did not find any tumors with mutations in the tyrosine kinase domain of the MET. These results demonstrated that the VHL tumor-suppressor gene is also involved in a subset of clear-cell RCCs occurring in ESRD/ACDK, as in the case of sporadic clear-cell RCCs. However, mutations of the MET oncogene could not be found in the seven ESRD/ACDK-associated papillary RCCs examined.

Adenocarcinoma, Clear Cell↗

PubMed2002

Corneal remodeling by hard contact lenses to manage microstriae after laser in situ keratomileusis.

Gas-permeable hard contact lenses were prescribed to 2 patients with corneal microstriae 3 months and 9 months, respectively, after laser in situ keratomileusis. The uncorrected visual acuity (UCVA) in both patients when the hard contact lenses were prescribed was 20/30 with +2.25 -1.25 x 60 and +1.50 -2.25 x 150, respectively. At 6 months in Case 1 and 3 months in Case 2, the topographic change showed corneal remodeling, with the UCVA 20/20 in both cases.

Adult↗

PubMed2002

Cigarette smoke inhibits the growth of lung fibroblasts from patients with pulmonary emphysema.

OBJECTIVE: To investigate the proliferative characteristics of fibroblasts cultured from emphysematous lungs. METHODS: Fibroblasts were isolated and cultured from emphysematous lungs surgically resected as a consequence of lung volume reduction surgery and from non-cancerous areas of lungs obtained following resection for lung cancer as a non-emphysematous control. Their proliferative activities were compared, as was the effect of cigarette smoke extract (CSE) on fibroblast proliferation. After incubation with various concentrations of CSE, cells were harvested and cell numbers were counted. Growth curves were constructed and doubling time was calculated to compare the proliferative activity of fibroblasts from emphysematous and non-emphysematous lungs. RESULTS: The proliferation of fibroblasts from emphysematous lungs cultured with normal medium appeared suppressed compared with non-emphysematous lungs. The addition of CSE to the medium induced more obvious growth inhibition in emphysematous lung fibroblasts. The growth of both fibroblast cultures was inhibited by CSE and this appeared to be concentration dependent. CONCLUSIONS: Fibroblasts from emphysematous lungs had lower proliferative activity and were more susceptible to cigarette smoke than those from non-emphysematous lungs. Cigarette smoke may play a critical role in the development and deterioration of pulmonary emphysema by suppressing the growth of lung fibroblasts.

Aged↗

PubMed2002

Runx2 (Cbfa1, AML-3) interacts with histone deacetylase 6 and represses the p21(CIP1/WAF1) promoter.

Runx2 (Cbfa1, AML-3) is multifunctional transcription factor that is essential for osteoblast development. Runx2 binds specific DNA sequences and interacts with transcriptional coactivators and corepressors to either activate or repress transcription of tissue-specific genes. In this study, the p21(CIP/WAF1) promoter was identified as a repressible target of Runx2. A carboxy-terminal repression domain distinct from the well-characterized TLE/Groucho-binding domain contributed to Runx2-mediated p21 repression. This carboxy-terminal domain was sufficient to repress a heterologous GAL reporter. The repressive activity of this domain was sensitive to the histone deacetylase inhibitor trichostatin A but not to trapoxin B. HDAC6, which is insensitive to trapoxin B, specifically interacted with the carboxy terminus of Runx2. The HDAC6 interaction domain of Runx2 was mapped to a region overlapping the nuclear matrix-targeting signal. The Runx2 carboxy terminus was necessary for recruitment of HDAC6 from the cytoplasm to chromatin. HDAC6 also colocalized and coimmunoprecipitated with the nuclear matrix-associated protein Runx2 in osteoblasts. Finally, we show that HDAC6 is expressed in differentiating osteoblasts and that the Runx2 carboxy terminus is necessary for maximal repression of the p21 promoter in preosteoblasts. These data identify Runx2 as the first transcription factor to interact with HDAC6 and suggest that HDAC6 may bind to Runx2 in differentiating osteoblasts to regulate tissue-specific gene expression.

Animals↗

PubMed2002

Apoptotic regulation by the Crk adapter protein mediated by interactions with Wee1 and Crm1/exportin.

The adapter protein Crk contains an SH2 domain and two SH3 domains. Through binding of particular ligands to the SH2 domain and the N-terminal SH3 domain, Crk has been implicated in a number of signaling processes, including regulation of cell growth, cell motility, and apoptosis. We report here that the C-terminal SH3 domain, never shown to bind any specific signaling molecules, contains a binding site for the nuclear export factor Crm1. We find that a mutant Crk protein, deficient in Crm1 binding, promotes apoptosis. Moreover, this nuclear export sequence mutant [NES(-) Crk] interacts strongly, through its SH2 domain, with the nuclear tyrosine kinase, Wee1. Collectively, these data suggest that a nuclear population of Crk bound to Wee1 promotes apoptotic death of mammalian cells.

Active Transport, Cell Nucleus↗

PubMed2002

Short-step syntheses of all stereoisomers of preussin and their bioactivities.

All the eight stereoisomers of (+)-preussin (1b), an antifungal agent inhibiting the growth of fission yeast and human cancer cells, were synthesized in two steps by non-stereoselective reactions and chromatographic separation, starting from L- and D-N-protected-phenylalaninal (2). Their bioassay revealed all of the stereoisomers to be almost equally bioactive.

Anisomycin↗

PubMed2002

Placental to fetal transfer of mercury and fetotoxicity.

Mercury vapor is known penetrate the placental barrier more easily than inorganic mercury. A relative amount of mercury accumulates in the fetus after exposure of pregnant animals to mercury vapor. Mercury concentration in fetal organs is much lower than that in maternal organs except the liver, and fetal liver shows significantly higher mercury concentrations than maternal liver. In fetal liver, a substantial portion of mercury is bound to metallothionein (MT), which plays an important role as a reservoir of mercury during the prenatal period. The mercury retained in fetal liver is redistributed to other organs, such as the brain and kidney, with diminishing MT levels during postnatal development. Consequently, an increase in mercury concentration in the brain and kidney of the neonate is observed. In studies on animal offspring in utero exposed to mercury vapor, behavioral changes, such as radial arm maze, morris maze and lever-press durations, are observed when the levels of mercury vapor exceed the threshold limit value (TLV).

Animals↗

PubMed2002

[Issues in the development of drugs for treating deep-seated mycosis].

This review is a collection of abstracts of seven papers presented at the panel discussion Issues in the Development of Drugs for Treating Deep-Seated Mycosis - From Drug Discovery to Clinical Studies held at the 45th Annual Meeting of the Japanese Society of Medical Mycology. The first three presentations concerned the discovery of new drugs. The first discussed the screening, analysis of chemical structure and elucidation of the mechanism of action of new antifungal agents focusing on aureobasidin A. The second was on the search for and development of novel agents with selective targets of action, specifically FK463 (micafungin) which inhibits (1-3)-beta-glucan synthase. The third described the development of novel derivatives based on the structure-activity correlation of triazole agents, with CS-758 as an example. The remaining four presentations discussed the status and issues of clinical studies targeting hematological disorders and respiratory diseases, as well as various problems from the company point of view on new drug development and those from the government side concerning the approval of new drugs. This type of meeting which provides an opportunity for discussion of various multi-faceted issues from the discovery of a new drug to its preclinical and clinical studies can contribute greatly to progress in the future development of new antifungal agents.

Animals↗

PubMed2002

[Bilateral pheochromocytomas and asynchronous bilateral renal cell carcinomas associated with von Hippel-Lindau disease: a case report].

A 38-year-old man who had been followed with diagnosis of dilated cardiomyopathy and retinal angioma was referred to our hospital because of incidentally detected bilateral adrenal masses. Although he was normotensive, levels of catecholamine in urine were elevated and I131-MIBG scintigraphy showed accumulation in bilateral adrenal glands. Screening of central nervous system by MRI revealed cerebellar hemangioblastoma. Right adrenalectomy and left partial adrenalectomy were performed, both of which tumors pathologically diagnosed as pheochromocytoma, followed by resection of the cerebellar hemangioblastoma. Five months later, abdominal CT revealed a left renal tumor and underwent left partial nephrectomy, being diagnosed as renal cell carcinoma. A right renal tumor was detected on follow up CT at 1 year after the partial nephrectomy. Since cardiac function was deteriorated, we have followed with careful observation. This is the second documented case of bilateral renal cell carcinomas and bilateral pheochromocytomas with VHL in Japan.

Adrenal Gland Neoplasms↗

PubMed2002

GEX1 compounds, novel antitumor antibiotics related to herboxidiene, produced by Streptomyces sp. II. The effects on cell cycle progression and gene expression.

Six GEX1 compounds, GEX1A/herboxidiene and its related 5 novel compounds, were isolated from a culture broth of Streptomyces sp. GEX1 compounds induced both G1 and G2/M arrest in a human normal fibroblast cell line, WI-38. All six compounds up-regulated luciferase reporter gene expression directed by enhancer/promoter of various genes, such as cdc2, IL-2 and SV40 early genes. All GEX1 compounds showed cytotoxic activities in the same order of the up-regulating activities on gene expression, suggesting that these two activities are related. Despite the up-regulating activities on the reporter gene expression, GEX1A/herboxidiene did not enhance the expression of any endogenous genes involved in the cell cycle, proliferation and apoptosis. Although the unique effects of GEX1 compounds on cell cycle and the reporter gene expression were similar to those of trichostatin A (TSA), an inhibitor of histone deacetylase (HDAC), GEX1A/herboxidiene did not affect histone acetylation in cells. In addition, GEX1A/herboxidiene treatment gave rise to the shorter sized transcripts of the cdc25A and cdc2 genes as well as the normal sized ones. These results suggest that GEX1 compounds modulate gene expression by an unknown mechanism.

Antibiotics, Antineoplastic↗

PubMed2002

The effect of adjuvant 5'-deoxy-5-fluorouridine in early stage breast cancer patients: results from a multicenter randomized controlled trial.

To assess the efficacy of 5'-DFUR, an intermediate of capecitabine, for adjuvant treatment of early breast cancer, we conducted an open-labeled multi-center randomized controlled trial to compare postoperative 5'-DFUR treatment with surgery alone. We enrolled 1217 primary breast cancer patients and randomly assigned them into two treatment groups; one received six-month postoperative 5'-DFUR treatment by consecutive or intermittent administration, and the other surgery alone. Follow-up surveys were conducted once a year for all subjects simultaneously and examined their outcome/presence or absence of the cancer recurrence. The central study committee reviewed all follow-up data and judged the recurrence data to be used for the analysis. Eight-year follow-up data showed no significant differences in relapse-free and overall survival between the two groups, and 5'-DFUR treatment regimen showed an extremely high tolerance. Possible explanations are discussed for the finding of no significant survival difference between adjuvant 6-month 5'-DFUR monotherapy and surgery alone in early breast cancer.

Adult↗

PubMed2001

The cytoplasmic shuttling and subsequent degradation of p27Kip1 mediated by Jab1/CSN5 and the COP9 signalosome complex.

The fifth component of the COP9 signalosome complex, Jab1/CSN5, directly binds to and induces specific down-regulation of the cyclin-dependent kinase inhibitor p27 (p27(Kip1)). Nuclear-cytoplasmic translocation plays an important role because leptomycin B (LMB), a chemical inhibitor of CRM1-dependent nuclear export, prevents p27 degradation mediated by Jab1/CSN5. Here we show that Jab1/CSN5 functions as an adaptor between p27 and CRM1 to induce nuclear export and subsequent degradation. Jab1/CSN5, but not p27, contains a typical leucine-rich nuclear export signal (NES) sequence conserved among different species, through which CRM1 bound to Jab1/CSN5 in an LMB-sensitive manner. Alteration of conserved leucine residues to alanine within Jab1/CSN5-NES abolished the interaction with CRM1 in vitro and impaired LMB-sensitive nuclear export and the ability to induce p27 breakdown in cultured cells. A Jab1/CSN5 truncation mutant lacking NES reversed p27 down-regulation induced by the full-length Jab1/CSN5, indicating that this mutant functions as a dominant negative (DN-Jab1). Introduction of DN-Jab1 into proliferating fibroblasts increased the level of p27 protein, thereby inducing growth arrest of the cells. Random mutagenesis analysis revealed that specific aspartic acid, leucine, and asparagine residues contained in the Jab1/CSN5-binding domain of p27 were required for interaction with Jab1/CSN5 and for down-regulation of p27. Glycerol gradient and cell fractionation experiments showed that at least two different forms of Jab1/CSN5-containing complexes existed within the cell. One is the conventional 450-kDa COP9 signalosome (CSN) complex located in the nucleus, and the other is much smaller (around 100-kDa), containing only a subset of CSN components (CSN4-8 but not CSN1-3), and mainly located in the cytoplasm. Treatment of cells with LMB greatly reduced the level of the smaller complex, suggesting that it originated from the CSN complex by nuclear export. Besides Jab1/CSN5, CSN3, -6, -7, and -8 were capable of inducing p27 down-regulation, when ectopically expressed. These results indicate that cytoplasmic shuttling regulated by Jab1/CSN5 and other CSN components may be a new pathway to control the intracellular abundance of the key cell cycle regulator.

3T3 Cells↗