Yasuyo Nakajima

Gunma University, Maebashi-shi, Gunma-ken, Japan

Are you Yasuyo Nakajima?

Claim your profile

Publications (13)42.42 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Emerging evidence has indicated that the transcription and processing of precursor mRNA (pre-mRNA) are functionally coupled to modulate gene expression. In collaboration with coregulators, several steroid hormone receptors have previously been shown to directly affect alternative pre-mRNA splicing coupled to hormone-induced gene transcription; however, the roles of the thyroid hormone receptor (TR) and its coregulators in alternative splicing coordinated with transcription remain unknown. In the present study, we constructed a luciferase reporter and CD44 alternative splicing (AS) minigene driven by a minimal promoter carrying 2 copies of the palindromic thyroid hormone-response element. We then examined whether TR could modulate pre-mRNA processing coupled to triiodothyronine (T3)-induced gene transcription using luciferase reporter and splicing minigene assays in HeLa cells. In the presence of cotransfected TRβ1, T3 increased luciferase activities along with the inclusion of the CD44 variable exons 4 and 5 in a dose- and time-dependent manner. In contrast, cotransfected TRβ1 did not affect the exon-inclusion of the CD44 minigene driven by the cytomegalovirus promoter. T3-induced two-exon inclusion was significantly increased by the cotransfection of the TR-associated protein, 150-kDa, a subunit of the TRAP/Mediator complex that has recently been shown to function as a splicing factor. In contrast, T3-induced two-exon inclusion was significantly decreased by cotransfection of the polypyrimidine tract-binding protein-associated splicing factor, which was previously shown to function as a corepressor of TR. These results demonstrated that liganded TR in cooperation with its associating cofactors could modulate alternative pre-mRNA splicing coupled to gene transcription.
    Biochemical and Biophysical Research Communications 08/2014; · 2.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Somatic mutations of the catalytic subunit of the cyclic AMP-dependent protein kinase (PRKACA) gene have recently been identified in about 35% of cortisol-producing adenomas (CPAs), with the affected patients showing overt Cushing's syndrome. Since we recently reported higher prevalence of mutations of the KCNJ5 gene and associations with autonomous cortisol secretion in Japanese aldosterone-producing adenomas than in Western countries, there might be different features of CPAs between Japan and the West. We therefore investigated mutations of the PRKACA gene in Japanese patients with several adrenal tumors secreting cortisol, including overt Cushing's syndrome, subclinical Cushing's syndrome, and aldosterone-producing adenomas (APAs) co-secreting cortisol operated on at Gunma University Hospital. Of the 13 patients with CPA who showed overt Cushing's syndrome, 3 (23%) had recurrent somatic mutations of the PRKACA gene, p.L206R (c.617 T>G), and there were no mutations in subclinical Cushing's syndrome. Among 33 APAs, 24 had somatic mutations of the KCNJ5 gene, either G151R or L168R, 11 (33%) had autonomous cortisol secretion, but there were no mutations of the PRKACA gene. We established a PCR-restriction fragment length polymorphism assay and revealed that the mutated allele was expressed at a similar level to the wild-type allele. These findings demonstrated that 1) the prevalence of Japanese patients with CPA who showed overt Cushing's syndrome and whose somatic mutations in the PRKACA gene was similar to that in Western countries, 2) the mutation might be specific for CPAs causing overt Cushing's syndrome, and 3) the mutant PRKACA allele was expressed appropriately in CPAs.
    Endocrine Journal 07/2014; · 2.02 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Context:Subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) increase with age, however their relation remains unclear.Objective:Our objective was to investigate the relation between SCH and indices of metabolic syndrome, and follow-up subjects for one year.Design:Cross-sectional and longitudinal follow-up studies of cases were collected from Takasaki Hidaka Hospital between 2003 and 2007.Participants:Overall, 11,498 participants of health check ups were analyzed. The mean age was 48 ± 9 years.Main Outcome Measures:Relation between SCH and indices of MetS were examined.Results:Serum free T4 (FT4) levels were lower in women than men in most of the age groups, and the prevalence of SCH, 6.3 % in women versus 3.4 % in man, increased with age, reaching 14.6 % in 70∼ year-old women. Multivariate logistic-regression analyses revealed that waist circumference, and the serum triglyceride and LDL-cholesterol levels were significantly higher in subjects with SCH than without among women. Reflecting these findings, the adjusted odds ratio (OR) of MetS in patients with SCH was higher than in the euthyroid subjects in women with OR, 2.7 (95% CI, 1.1-5.6; p=0.017), but not in men. Furthermore, progression from euthyroid into SCH resulted in a significant increase in the serum triglyceride level but not LDL-C in women.Conclusion:Japanese women exhibited a high prevalence of SCH associated with low FT4 levels. There was a strong association between SCH and several indices of metabolic syndrome in women. SCH may affect serum triglyceride levels and be a risk factor for metabolic syndrome.Precis:Subclinical hypothyroidism may affect the serum triglyceride level and be a risk factor for metabolic syndrome in Japanese women.
    The Journal of Clinical Endocrinology and Metabolism 06/2013; · 6.31 Impact Factor
  • Yasuyo Nakajima, Masanobu Yamada
    [Show abstract] [Hide abstract]
    ABSTRACT: Subclinical thyroid disease is defined as a disorder involving an abnormal serum thyroid-stimulating hormone level (TSH), but free thyroxine (FT4) and triiodothyronine (FT3) levels within the reference range. The prevalence of subclinical hypothyroidism is about 4 to 8.5 percent of the population, and may rise to about 20 percent in women older than 60 years. The clinical significance of subclinical thyroid disease remains controversial. Several studies have reported that subclinical hypothyroidism may be a risk factor for atherosclerosis and cardiovascular disorders, and subclinical hyperthyroidism for atrial fibrillation and reduced bone mineral density. However, there is a little evidence showing the significance of early treatment for both disorders. In this review, we discuss the prevalence, diagnosis, natural history, and potential pathophysiological consequences of subclinical hypo- and hyperthyroidism.
    Nippon rinsho. Japanese journal of clinical medicine 11/2012; 70(11):1865-71.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Adrenal aldosterone-producing adenomas (APA) are rarely associated with the clear co-secretion of cortisol. Somatic mutations of the potassium channel KCNJ5 gene, with the hotspots G151R and L168R, have been recently identified in patients with APA. However, whether APAs that secrete cortisol have these mutations remains unclear. We examined three patients with APAs showing clear autonomous secretion of cortisol who possessed a 1 mg dexamethasone suppression test (DST) with a failure of the serum cortisol level to drop below 3.0 μg/dL, a morning plasma ACTH level of less than 10 pg/mL, and suppressed accumulation in the intact adrenal on (131)I- adosterol scintigraphy, or postoperative adrenal insufficiency. Laparoscopic adrenectomy revealed all tumors to be golden yellow, and histological examination confirmed them to be adrenocortical adenomas. All these patients required replacement therapy with hydrocortisone after surgery. Sequencing demonstrated that 2 of three cases showed a mutation of the KCNJ5 gene, one with c.451G>A, p.G151R and one with c.503T>G, p.L168R. Furthermore, the mRNA levels of steroidogenic enzymes including CYP11B1, CYP11B2, HSD3B2, CYP17A1, CYP11A1 and KCNJ5 in the 3 cases did not differ from those in 8 pure APAs not showing any of the above conditions for autonomous cortisol secretion. In addition, all 8 pure APAs harbored mutations of the KCNJ5 gene. These findings suggested that at least some aldosterone- and cortisol-co-secreting adrenal tumors have mutations of the KCNJ5 gene, suggesting the origin to be APA, and pure APAs may show a high incidence of KCNJ5 mutations.
    Endocrine Journal 08/2012; 59(8):735-41. · 2.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Thyrotropin-releasing hormone (TRH) is a major stimulator of thyrotropin-stimulating hormone (TSH) synthesis in the anterior pituitary, though precisely how TRH stimulates the TSHβ gene remains unclear. Analysis of TRH-deficient mice differing in thyroid hormone status demonstrated that TRH was critical for the basal activity and responsiveness to thyroid hormone of the TSHβ gene. cDNA microarray and K-means cluster analyses with pituitaries from wild-type mice, TRH-deficient mice and TRH-deficient mice with thyroid hormone replacement revealed that the largest and most consistent decrease in expression in the absence of TRH and on supplementation with thyroid hormone was shown by the TSHβ gene, and the NR4A1 gene belonged to the same cluster as and showed a similar expression profile to the TSHβ gene. Immunohistochemical analysis demonstrated that NR4A1 was expressed not only in ACTH- and FSH- producing cells but also in thyrotrophs and the expression was remarkably reduced in TRH-deficient pituitary. Furthermore, experiments in vitro demonstrated that incubation with TRH in GH4C1 cells increased the endogenous NR4A1 mRNA level by approximately 50-fold within one hour, and this stimulation was inhibited by inhibitors for PKC and ERK1/2. Western blot analysis confirmed that TRH increased NR4A1 expression within 2 h. A series of deletions of the promoter demonstrated that the region between bp -138 and +37 of the TSHβ gene was responsible for the TRH-induced stimulation, and Chip analysis revealed that NR4A1 was recruited to this region. Conversely, knockdown of NR4A1 by siRNA led to a significant reduction in TRH-induced TSHβ promoter activity. Furthermore, TRH stimulated NR4A1 promoter activity through the TRH receptor. These findings demonstrated that 1) TRH is a highly specific regulator of the TSHβ gene, and 2) TRH mediated induction of the TSHβ gene, at least in part by sequential stimulation of the NR4A1-TSHβ genes through a PKC and ERK1/2 pathway.
    PLoS ONE 07/2012; 7(7):e40437. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mutations of the KCNJ5 gene have recently been identified in patients with aldosterone-producing adenomas (APA). Our objective was to investigate the expression and mutations of the KCNJ5 gene in Japanese patients with APA. We sequenced KCNJ5 cDNA and measured KCNJ5 mRNA levels in 23 patients with APA operated on at Gunma University Hospital. Mutations and mRNA levels of the KCNJ5 gene were examined and compared to those in cortisol-producing adenomas (Cushing's syndrome) and pheochromocytomas. Of the 23 patients with APA, 15 (65.2%) had two somatic mutations of the KCNJ5 gene: 12 cases of p.G151R (eight with c.451G>A, and four with c.451G>C) and three cases of p.L168R (c.503T>G). Levels of KCNJ5 mRNA were significantly higher in the APA with mutations than those without. Immunohistochemistry also showed a stronger staining of KCNJ5 on the cell membrane in the tumor with a mutation. Furthermore, a PCR-restriction fragment length polymorphism assay with c.503T>G revealed the mutant mRNA to be expressed at a similar level to the wild type. The level of KCNJ5 mRNA in cortisol-producing adenomas was approximately 30% of that in APA, and almost no expression was observed in pheochromocytomas. We found that: 1) a significant number of patients with APA had somatic mutations of the KCNJ5 gene; 2) KCNJ5 mRNA levels were higher in the APA with KCNJ5 mutations; and 3) the expression of KCNJ5 mRNA was significantly higher in APA than cortisol-producing adenomas and pheochromocytomas.
    The Journal of Clinical Endocrinology and Metabolism 01/2012; 97(4):1311-9. · 6.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Primary aldosteronism (PA) is sometimes associated with the autonomous secretion of cortisol. Our objective was to investigate the effect of autonomous cortisol secretion on the prevalence of cardiovascular events (CVE) in patients with PA. This was a retrospective cross-sectional study of cases collected from Gunma University Hospital between 2002 and 2010. Seventy-six consecutive patients hospitalized for an evaluation of PA were analyzed. Rates of CVE dependent on autonomous cortisol secretion were examined. Of the 76 patients with PA, 21 (28%) had a history of CVE, including 14 with stroke, one with myocardial infarction, and six with atrial fibrillation. The multivariate logistic-regression and receiver operating characteristic analyses revealed that PA patients with CVE had significantly higher midnight cortisol levels than those without CVE; the adjusted odds ratio with a cutoff value of 7.4 μg/dl was 7.0 (95% confidence interval, 1.8-30.6; P = 0.006). In addition, results of the 1-mg dexamethasone suppression test with a cutoff value of 3.0 μg/dl differed significantly (odds ratio, 5.0; 95% confidence interval, 1.4-20.7; P = 0.018). Conversely, 67 and 50% of the PA patients with a midnight cortisol level of at least 7.4 μg/dl and 1-mg dexamethasone suppression test of at least 3.0 μg/dl had a history of CVE. Other factors such as age, expected glomerular filtration rate, blood pressure, glucose intolerance, the serum aldosterone concentration, plasma renin activity, and the duration of hypertension had no effect. The patients with PA associated with autonomous cortisol secretion had high incidence of CVE, and this association may further increase the risk of CVE in patients with PA.
    The Journal of Clinical Endocrinology and Metabolism 05/2011; 96(8):2512-8. · 6.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe a rare case of congenital hypothyroidism and an extremely high serum thyrotropin (TSH) level caused by a combination of resistance to thyroid hormone (RTH) and a lingual thyroid. As the RTH mutant, R316C, was new, the optimum dose of levothyroxine was unclear. To aid in assessment of the therapy, we characterized the mutant R316C thyroid hormone receptor (TR) and compared it with a common mutant, R316H, using in vitro studies. The patient was a newborn female having severe hypothyroidism with a free thyroxine level of 0.36 ng/dL and a serum TSH level of 177 microU/mL. A scintiscan showed ectopic lingual thyroid tissue without a normal thyroid gland. Supplementation with levothyroxine at a dose of >350 microg/day did not normalize the serum TSH level; however, the patient showed normal growth and intelligence at 14 years of age. Consistent with the results of a computer analysis, the binding of R316C to triiodothyronine (T3) was significantly decreased to 38% that of the wild type. Electrophoretic mobility shift assay demonstrated that like R316H, R316C did not form a homodimer, but formed a heterodimer with RXR. However, a glutathione-S-transferase pull-down assay showed reduced binding of R316C with NCoR in the absence of T3 and impaired release in the presence of T3. In addition, transient transfection experiments demonstrated that unlike R316H, R316C had severe impairment of transcriptional activity on genes both positively and negatively regulated by thyroid hormone. It also had a clear dominant negative effect on genes negatively, but not positively, regulated by thyroid hormone, including the TSH-releasing hormone and TSHbeta genes. This is the first reported case of a R316C TR mutation. The characteristics of the R316C mutant differed from those of the R316H mutant. Our findings suggest that R316C causes reduced association with and impaired release of NCoR, resulting in RTH predominantly at the pituitary level, and that slightly elevated serum TSH level with high dose of levothyroxine might be optimum for normal growth.
    Thyroid: official journal of the American Thyroid Association 08/2010; 20(8):917-26. · 2.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 19S regulatory particles (19SRP) of 26S proteasome participate in multiple steps of gene transcription in yeast. We previously showed that Tat-binding protein-1 (TBP-1), an ATPase of 19SRP, interacts with thyroid hormone receptor (TR) and enhances TR-mediated transcription synergistically with steroid receptor coactivator-1 (SRC-1). To further elucidate the roles of ATPases and a non-ATPase component of 19SRP in gene regulation by TR, we investigated whether knockdown (KO) of TBP-1, TRIP1 or Rpn10 using small interfering RNA affects TR-mediated transactivation in HeLa cells. KO of individual subunits attenuated TR-mediated transactivation through the thyroid hormone response element (TRE) in the absence or presence of cotransfected SRC-1 without altering TR and SRC-1 protein levels. KO of TBP-1 disrupted ligand-induced loading of TR, SRC-1, and RNA polymerase II in chromatin immunoprecipitation assays. Collectively, both ATPase and non-ATPase components of 19SRP play critical roles in TR-mediated transactivation by coordinating the proper loading of liganded TR to TRE.
    Biochemical and Biophysical Research Communications 09/2009; · 2.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 26S proteasome, which degrades ubiquitinated proteins, appears to contribute to the cyclical loading of androgen receptor (AR) to androgen response elements of target gene promoters; however, the mechanism whereby the 26S proteasome modulates AR recruitment remains unknown. Using yeast two-hybrid screening, we previously identified Tat-binding protein-1 (TBP-1), an adenosine triphosphatase of 19S regulatory particles of the 26S proteasome, as a transcriptional coactivator of thyroid hormone receptor. Independently, TBP-1-interacting protein (TBPIP) was also identified as a coactivator of several nuclear receptors, including AR. Here, we investigated whether TBP-1 could interact with and modulate transcriptional activation by AR cooperatively with TBPIP. TBP-1 mRNA was ubiquitously expressed in human tissues, including the testis and prostate, as well as in LNCaP cells. TBP-1 directly bound TBPIP through the amino-terminal domain possessing the leucine zipper structure. AR is physically associated with TBP-1 and TBPIP in vitro and in LNCaP cells. TBP-1 similarly and additively augmented AR-mediated transcription upon coexpression with TBPIP, and the ATPase domain, as well as leucine zipper structure in TBP-1, was essential for transcriptional enhancement. Overexpression of TBP-1 did not alter AR protein and mRNA levels. In the chromatin immunoprecipitation assay, TBP-1 was transiently recruited to the proximal androgen response element of the prostate-specific antigen gene promoter in a ligand-dependent manner in LNCaP cells. These findings suggest that a component of 19S regulatory particles directly binds AR and might participate in AR-mediated transcriptional activation in cooperation with TBPIP.
    Endocrinology 04/2009; 150(7):3283-90. · 4.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hachimi-jio-gan is widely used to improve several disorders associated with diabetes, but its mechanism remains poorly understood. In an attempt to clarify the mechanism of Hachimi-jio-gan, we investigated the effects of this herbal medicine and its components in transfection studies of CV1 cells, especially nuclear receptor-mediated actions. One half (0.5) mg/ml of Hachimi-jio-gan activated peroxisome proliferator-activated receptor (PPARalpha), mediating the activation by 3.1-fold on DR1 response elements; however, it did not affect PPARgamma, thyroid hormone receptor, androgen receptor, estrogen receptor or RXR. In addition, this activation was observed in a dose-dependent manner. Next, to determine which components of Hachimi-jio-gan activate PPARalpha-mediated transcription, 8 of its components (rehmanniae radix, orni fructus, dioscoreae rhizoma, alismatis rhizoma, hoelen, moutan cortex, cinnamomi cortex, aconiti) were tested. Only cinnamomi cortex (1.0 mg/ml) increased PPARalpha-mediated transcription by 4.1-fold, and this activation was specific for PPAR alpha, and not for other nuclear receptors. Moreover, this PPARalpha-related activation by cinnamomi cortex is specifically observed in renal cells. Taken together, these findings indicate that Hachimi-jio-gan and cinnamomi cortex may have a pharmacological effect through the target site for PPARalpha.
    Endocrine Journal 08/2008; 55(3):529-33. · 2.02 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The role of thyroid hormone (T3) in the regulation of growth and development of the central nervous system including the cerebellum has been well established. However, the effects of thyroid hormone on malignant tumors derived from the cerebellum remain poorly understood. Our analysis mainly focused on expression levels of TR isoforms and the effects of thyroid hormone in human medulloblastoma HTB-185 cells. Northern blot analysis revealed TRalpha2 mRNA but not TRalpha1, beta1 or beta2 mRNA in the cell. The TRalpha1 and TRbeta1 mRNAs were detected only by RT-PCR method and TRbeta2 was not expressed. Incubation of T3 for 24 h decreased TRalpha1, TRalpha2 and TRbeta1 mRNA. Addition of actinomycin D caused an acute increase in the basal TR mRNA levels and the rate of decrease of all kinds of TR isoform mRNA was accelerated in the T3-treated groups compared to controls, indicating that the stability of TR mRNA was affected by T3. Incubation with cycloheximide also blocked a decrease in TR mRNA levels in the T3-treated HTB-185 cells suggesting that down-regulation of TR mRNA required the synthesis of new protein. Our data provide novel evidence for the expression of TRs down-regulated by T3 in HTB-185 cells, suggesting that TR expression is post-transcriptionally regulated by T3 at the level of RNA stability.
    Endocrine Journal 05/2006; 53(2):181-7. · 2.02 Impact Factor