研究者詳細 - 辰巳佐和子

論文 - 辰巳佐和子

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Targeted ablation of Osteocytes induces osteoporosis with defective mechanotransduction 査読

Sawako Tatsumi, Kiyoaki Ishii, Norio Amizuka, Minqi Li, Toshihiro Kobayashi, Kenji Kohno, Masako Ito, Sunao Takeshita, Kyoji Ikeda

CELL METABOLISM 5 ( 6 ) 464 - 475 2007年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CELL PRESS

Bone remodeling is performed by osteoclasts and osteoblasts at the bone surface. Inside of bone is a network of numerous osteocytes, whose specific function hasremained anenigma. Here we describe a transgenic mouse model in which inducible and specific ablation of osteocytes is achieved in vivo through targeted expression of diphtheria toxin (DT) receptor. Following a single injection of DT, approximately 70%-80% of the osteocytes, but apparently no osteoblasts, were killed. Osteocyte-ablated mice exhibited fragile bone with intracortical porosity and microfractures, osteolblastic dysfunction, and trabecular bone loss with microstructural deterioration and adipose tissue proliferation in the marrow space, all of which are hallmarks of the aging skeleton. Strikingly, these "osteocyte-less" mice were resistant to unloading-induced bone loss, providing evidence for the role of osteocytes in mechano-transduction. Thus, osteocytes represent an attractive target for the development of diagnostics and therapeutics for bone diseases, such as osteoporosis.

DOI： 10.1016/j.cmet.2007.05.001

Web of Science

PubMed

[alpha Klotho and inorganic phosphate metabolism]. 査読

Miyamoto K, Segawa H, Ito M, Tatsumi S

Clinical calcium 17 ( 5 ) 698 - 703 2007年5月

Characterization of the molecular mechanisms involved in the increased insulin secretion in rats with acute liver failure. 国際誌

Kuwahata M, Tomoe Y, Harada N, Amano S, Segawa H, Tatsumi S, Ito M, Oka T, Miyamoto K.

Biochim Biophys Acta. 1772 ( 1 ) 60 - 65 2007年1月

Unique uptake and efflux systems of inorganic phosphate in osteoclast-like cells. 国際誌

Ito M, Haito S, Furumoto M, Uehata Y, Sakurai A, Segawa H, Tatsumi S, Kuwahata M, Miyamoto K.

Am J Physiol Cell Physiol. 292 ( 1 ) C526 - C534 2007年1月

Characterization of the molecular mechanisms involved in the increased insulin secretion in rats with acute liver failure 査読

Masashi Kuwahata, Yuka Tomoe, Nagakatsu Harada, Saki Amano, Hiroko Segawa, Sawako Tatsumi, Mikiko Ito, Tatsuzo Oka, Ken-ichi Miyamoto

BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR BASIS OF DISEASE 1772 ( 1 ) 60 - 65 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

To investigate the mechanism of hypermsulinaemia in rats with acute liver failure induced by the administration of D-galactosamine (GaIN), we focused on the role of polyprimidine tract-binding protein (PTB) in islet insulin synthesis. Recent reports indicate that PTB binds and stabilizes mRNA encoding insulin and insulin secretory granule proteins, including islet cell autoantigen 512 (ICA512), prohormone convertase 1/3 (PC1/3), and PC2. In the present study, glucose-stimulated insulin secretion was significantly increased in GalN-treated rats compared to controls. Levels of mRNA encoding insulin 1, ICA512, and PC1/3 were increased in the pancreatic islets of GalN-treated rats. This mRNA level elevation was not prevented by pretreatment with actinomycin D. When the PTB-binding site in insulin I mRNA was incubated with the islet cytosolic fraction, the RNA-protein complex level was increased in the cytosolic fraction obtained from GalN-treated rats compared to the level in control rats. The cytosolic fraction obtained from pancreatic islets obtained from GalN-treated rats had an increased PTB level compared to the levels obtained from the pancreatic islets of control rats. These findings suggest that, in rats with acute liver failure, cytosolic PTB binds and stabilizes mRNA encoding insulin and its secretory granule proteins. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bbadis.2006.10.001

Web of Science

Characterization of the molecular mechanisms involved in the increased insulin secretion in rats with acute liver failure. 査読

Kuwahata M, Tomoe Y, Harada N, Amano S, Segawa H, Tatsumi S, Ito M, Oka T, Miyamoto K

Biochimica et biophysica acta 1772 ( 1 ) 60 - 65 2007年1月

Unique uptake and efflux systems of inorganic phosphate in osteoclast-like cells 査読

Mikiko Ito, Sakiko Haito, Mari Furumoto, Yoko Uehata, Aya Sakurai, Hiroko Segawa, Sawako Tatsumi, Masashi Kuwahata, Ken-ichi Miyamoto

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY 292 ( 1 ) C526 - C534 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSIOLOGICAL SOC

During bone resorption, a large amount of inorganic phosphate (P-i) is generated within the osteoclast hemivacuole. The mechanisms involved in the disposal of this P-i are not clear. In the present study, we investigated the efflux of P-i from osteoclast-like cells. P-i efflux was activated by acidic conditions in osteoclast-like cells derived by the treatment of RAW264.7 cells with receptor activator of nuclear factor-kappa B ligand. Acid-induced P-i influx was not observed in renal proximal tubule-like opossum kidney cells, osteoblast-like MC3T3-E1 cells, or untreated RAW264.7 cells. Furthermore, P-i efflux was stimulated by extracellular P-i and several P-i analogs [phosphonoformic acid (PFA), phosphonoacetic acid, arsenate, and pyrophosphate]. P-i efflux was time dependent, with 50% released into the medium after 10 min. The efflux of P-i was increased by various inhibitors that block P-i uptake, and extracellular P-i did not affect the transport of [C-14] PFA into the osteoclast-like cells. Preloading of cells with P-i did not stimulate P-i efflux by PFA, indicating that the effect of P-i was not due to transstimulation of P-i transport. P-i uptake was also enhanced under acidic conditions. Agents that prevent increases in cytosolic free Ca2+ concentration, including acetoxymethyl ester of 1,2-bis(2-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid, 2-aminoethoxydiphenyl borate, and bongkrekic acid, significantly inhibited P-i uptake in the osteoclast-like cells, suggesting that P-i uptake is regulated by Ca2+ signaling in the endoplasmic reticulum and mitochondria of osteoclast-like cells. These results suggest that osteoclast-like cells have a unique P-i uptake/efflux system and can prevent P-i accumulation within osteoclast hemivacuoles.

DOI： 10.1152/ajpcell.00357.2006

Web of Science

PubMed

Control of phosphate appetite in young rats 査読

Ritsuko Ohnishi, Hiroko Segawa, Eri Kawakami, Junya Furutani, Mikiko Ito, Sawako Tatsumi, Masashi Kuwahata, Ken-Ichi Miyamoto

Journal of Medical Investigation 54 ( 3-4 ) 366 - 369 2007年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In the present study, we investigated whether a diet deficient in inorganic phosphate (Pi) stimulates an ingestive behavior to seek sources of Pi. Male Wistar rats were placed in individual cages with unrestricted access to tap water and a low (LPD, 0.02% Pi) or normal (NPD, 0.6% Pi) Pi diet for 6 days. On day 7, LDP rats were given unlimited access to a solution of 25 mM potassium phosphate water (Pi-water) for 9 additional days. Rats fed LPD consumed 70-100% more Pi-water then those fed NPD. The increase in Pi-water intake resulted in a marked rise in the growth rate of rats fed LPD during day 9. A similar intake of Pi was induced after only 2 days of LPD and was associated with significant reductions in both plasma and cerebrospinal fluid (CSF) levels of Pi
these levels remained low throughout Pi restriction, despite a significant intake of Pi-water. Replenishment with a high-Pi diet rapidly quenched the appetite for Pi-water and was associated with restoration of both plasma and CSF Pi levels. These findings suggest that an appetite for Pi can be induced in rats, perhaps through lowered plasma and CSF Pi levels.

DOI： 10.2152/jmi.54.366

Scopus

PubMed

Correlation between hyperphosphatemia and type II Na/Pi cotransporter activity in klotho mice. 査読

Segawa H, Yamanaka S, Ohno Y, Onitsuka A, Shiozawa K, Aranami F, Furutani J, Tomoe Y, Ito M, Kuwahata M, Tatsumi S, Imura A, Nabeshima Y, Miyamoto KI

Am J Physiol Renal Physiol 292 ( 2 ) F769-79 - F779 2007年

New aspect of renal phosphate reabsorption: The type IIc sodium-dependent phosphate transporter 査読

Ken-Ichi Miyamoto, Mikiko Ito, Sawako Tatsumi, Masashi Kuwahata, Hiroko Segawa

AMERICAN JOURNAL OF NEPHROLOGY 27 ( 5 ) 503 - 515 2007年

記述言語：英語出版者・発行元：KARGER

Abnormalities of the inorganic phosphate ( Pi) reabsorption in the kidney result in various metabolic disorders. Na+-dependent Pi (Na/Pi) transporters in the brush border membrane of proximal tubular cells mediate the rate-limiting step in the overall Pi-reabsorptive process. Type IIa and type IIc Na/Pi cotransporters are expressed in the apical membrane of proximal tubular cells and mediate Na/Pi cotransport; the extent of Pi reabsorption in the proximal tubules is determined largely by the abundance of the type IIa Na/Pi cotransporter. However, several studies suggest that the type IIc cotransporter in Pi reabsorption may also play a role in this process. For example, mutation of the type IIc Na/Pi cotransporter gene results in hereditary hypophosphatemic rickets with hypercalciuria, suggesting that the type IIc transporter plays an important role in renal Pi reabsorption in humans and may be a key determinant of the plasma Pi concentration. The type IIc Na/Pi transporter is regulated by parathyroid hormone, dietary Pi, and fibroblast growth factor 23, and studies suggest a differential regulation of the IIa and IIc transporters. Indeed, differences in temporal and/or spatial expression of the type IIa and type IIc Na/Pi transporters may be required for normal phosphate homeostasis and bone development. This review will briefly summarize the regulation of renal Pi transporters in various Pi-wasting disorders and highlight the role of a relatively new member of the Na/Pi cotransporter family: the type IIc Na/Pi transporter/ SLC34A3. Copyright (c) 2007 S. Karger AG, Basel.

DOI： 10.1159/000107069

Web of Science

PubMed

Activation of pre-mRNA splicing by human RNPS1 is regulated by CK2 phosphorylation. 国際誌

Trembley JH, Tatsumi S, Sakashita E, Loyer P, Slaughter CA, Suzuki H, Endo H, Kidd VJ, Mayeda A.

Mol Cell Biol. 25 ( 4 ) 1446 - 1457 2005年2月

Activation of pre-mRNA splicing by human RNPS1 is regulated by CK2 phosphorylation 査読

JH Trembley, S Tatsumi, E Sakashita, P Loyer, CA Slaughter, H Suzuki, H Endo, VJ Kidd, A Mayeda

MOLECULAR AND CELLULAR BIOLOGY 25 ( 4 ) 1446 - 1457 2005年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC MICROBIOLOGY

Human RNPS1 was originally characterized as a pre-mRNA splicing activator in vitro and was shown to regulate alternative splicing in vivo. RNPS1 was also identified as a protein component of the splicing-dependent mRNP complex, or exon-exon junction complex (EJC), and a role for RNPS1 in postsplicing processes has been proposed. Here we demonstrate that RNPS1 incorporates into active spliceosomes, enhances the formation of the ATP-dependent A complex, and promotes the generation of both intermediate and final spliced products. RNPS1 is phosphorylated in vivo and interacts with the CK2 (casein kinase II) protein kinase. Serine 53 (Ser-53) of RNPS1 was identified as the major phosphorylation site for CK2 in vitro, and the same site is also phosphorylated in vivo. The phosphorylation status of Ser-53 significantly affects splicing activation in vitro, but it does not perturb the nuclear localization of RNPS1. In vivo experiments indicated that the phosphorylation of RNPS1 at Ser-53 influences the efficiencies of both splicing and translation. We propose that RNPS1 is a splicing regulator whose activator function is controlled in part by CK2 phosphorylation.

DOI： 10.1128/MCB.25.4.1446-1457.2005

Web of Science

PubMed

Human RNPS1 and its associated factors: a versatile alternative pre-mRNA splicing regulator in vivo. 国際誌

Sakashita E, Tatsumi S, Werner D, Endo H, Mayeda A.

Mol Cell Biol. 24 ( 3 ) 1174 - 1187 2004年2月

Human RNPS1 and its associated factors: A versatile alternative pre-mRNA splicing regulator in vivo 査読

E Sakashita, S Tatsumi, D Werner, H Endo, A Mayeda

MOLECULAR AND CELLULAR BIOLOGY 24 ( 3 ) 1174 - 1187 2004年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC MICROBIOLOGY

Human RNPS1 was originally purified and characterized as a pre-mRNA splicing activator, and its role in the postsplicing process has also been proposed recently. To search for factors that functionally interact with RNPS1, we performed a yeast two-hybrid screen with a human cDNA library. Four factors were identified: p54 (also called SRp54; a member of the SR protein family), human transformer 2beta (hTra2beta; an exonic splicing enhancer-binding protein), hLucA (a potential component of U1 snRNP), and pinin (also called DRS and MemA; a protein localized in nuclear speckles). The N-terminal region containing the serine-rich (S) domain, the central RNA recognition motif (RRM), and the C-terminal arginine/serine/proline-rich (RS/P) domain of RNPS1 interact with p54, pinin, and hTra2beta, respectively. Protein-protein binding between RNPS1 and these factors was verified in vitro and in vivo. Overexpression of RNPS1 in HeLa cells induced exon skipping in a model beta-globin pre-mRNA and a human tra-2beta pre-mRNA. Coexpression of RNPS1 with p54 cooperatively stimulated exon inclusion in an ATP synthase gamma-subunit pre-mRNA. The RS/P domain and RRM are necessary for the exon-skipping activity, whereas the S domain is important for the cooperative effect with p54. RNPS1 appears to be a versatile factor that regulates alternative splicing of a variety of pre-mRNAs.

DOI： 10.1128/MCB.24.3.1174-1187.2004

Web of Science

PubMed

Molecular mechanisms of mammalian inorganic phosphate homeostasis. 招待国際誌

Takeda E, Taketani Y, Morita K, Tatsumi S, Katai K, Nii T, Yamamoto H, Miyamoto K.

Advances in Enzyme Regulation 40 ( 1 ) 285 - 302 2002年6月

Growth-related renal type II Na/Pi cotransporter. 国際誌

Segawa H, Kaneko I, Takahashi A, Kuwahata M, Ito M, Ohkido I, Tatsumi S, Miyamoto K.

J Biol Chem. 277 ( 22 ) 19665 - 19672 2002年5月

Identification and functional analysis of three isoforms for the Na+-dependent phosphate co-transporter (NaPi-2) in rat kidney. 招待国際誌

Miyamoto K, Tatsumi S, Segawa H, Ohkido I, Takeda E.

Nephrol Dial Transplant. 15 ( Suppl 6 ) 31 - 33 2002年5月

Growth-related renal type IINa/P-i cotransporter 査読

H Segawa, Kaneko, I, A Takahashi, M Kuwahata, M Ito, Ohkido, I, S Tatsumi, K Miyamoto

JOURNAL OF BIOLOGICAL CHEMISTRY 277 ( 22 ) 19665 - 19672 2002年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Growth is critically dependent on the retention of a variety of nutrients. The kidney contributes to this positive external balance. In the present study, we isolated a cDNA from the human and rat kidney that encodes a growth-related Na+-dependent inorganic phosphate (P-i) cotransporter (type IIc). Microinjection of type IIc cRNA into Xenopus oocytes demonstrated sodium-dependent P-i cotransport activity. Affinity for P-i was 0.07 mm in 100 mm Na+. The transport activity was dependent on extracellular pH. In electrophysiological studies, type IIc Na/P-i cotransport was electroneutral, whereas type IIa was highly electrogenic. In Northern blotting analysis, the type IIc transcript was only expressed in the kidney and highly in weaning animals. In immunohistochemical analysis, the type IIc protein was shown to be localized at the apical membrane of the proximal tubular cells in superficial and midcortical nephrons of weaning rat kidney. Hybrid depletion experiments suggested that type IIc could function as a Na/P-i cotransporter in weaning animals, but its role is reduced in adults. The finding of the present study suggest that the type IIc is a growth-related renal Na/P-i cotransporter, which has a high affinity for P-i and is electroneutral.

DOI： 10.1074/jbc.M200943200

Web of Science

PubMed

Identification and functional analysis of three isoforms for the Na+-dependent phosphate co-transporter (NaPi-2) in rat kidney 査読

K Miyamoto, S Tatsumi, H Segawa, Ohkido, I, E Takeda

NEPHROLOGY DIALYSIS TRANSPLANTATION 15 31 - 33 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OXFORD UNIV PRESS

We have isolated three unique NaPi-2-related protein cDNAs (NaPi-2 alpha, NaPi-2 beta and NaPi-2 gamma) from a rat kidney library. NaPi-2 alpha cDNA encodes 337 amino acids which have high homology to the N-terminal half of NaPi-2 containing three transmembrane domains. NaPi-2 beta encodes 327 amino acids which are identical to the N-terminal region of NaPi-2 containing four transmembrane domains, whereas the 146 amino acids in the C-terminal region are completely different. In contrast, NaPi-2 gamma encodes 268 amino acids which are identical to the C-terminal half of NaPi-2. An analysis of phage and cosmid clones indicated that the three related proteins were produced by alternative splicing in the NaPi-2 gene. In a rabbit reticulocyte lysate system, NaPi-2 alpha, beta and gamma were found to be 36, 36 and 29 kDa polypeptides, respectively. NaPi-2 alpha and NaPi-2 gamma were glycosylated and revealed to be 45 and 35 kDa proteins, respectively. A functional analysis demonstrated that NaPi-2 gamma and alpha markedly inhibited NaPi-2 activity in Xenopus oocytes. The results suggest that these short isoforms may function as a dominant-negative inhibitor of the full-length transporter.

Web of Science

Molecular mechanisms of mammalian inorganic phosphate homeostasis. 査読

Takeda E, Taketani Y, Morita K, Tatsumi S, Katai K, Nii T, Yamamoto H, Miyamoto K

Advances in enzyme regulation 40 285 - 302 2000年

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