研究者詳細 - 辰巳佐和子

論文 - 辰巳佐和子

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An apical expression signal of the renal type IIc Na+-dependent phosphate cotransporter in renal epithelial cells 査読

Mikiko Ito, Aya Sakurai, Keiji Hayashi, Akiko Ohi, Natsumi Kangawa, Takashi Nishiyama, Sakiko Sugino, Yoko Uehata, Akihiro Kamahara, Masae Sakata, Sawako Tatsumi, Masashi Kuwahata, Yutaka Taketani, Hiroko Segawa, Ken-Ichi Miyamoto

American Journal of Physiology - Renal Physiology 299 ( 1 ) F243 - F254 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

The type IIc Na+-dependent phosphate cotransporter (NaPi-IIc) is specifically targeted to, and expressed on, the apical membrane of renal proximal tubular cells and mediates phosphate transport. In the present study, we investigated the signals that determine apical expression of NaPi-IIc with a focus on the role of the N- and the C-terminal tails of mouse NaPi-IIc in renal epithelial cells [opossum kidney (OK) and Madin-Darby canine kidney cells]. Wild-type NaPi-IIc, the cotransporter NaPi-IIa, as well as several IIa-IIc chimeras and deletion mutants, were fused to enhanced green fluorescent protein (EGFP), and their cellular localization was analyzed in polarized renal epithelial cells by confocal microscopy and by cell-surface biotinylation. Fluorescent EGFP-fused NaPi-IIc transporter proteins are correctly expressed in the apical membrane of OK cells. The apical expression of N-terminal deletion mutants (deletion of N-terminal 25, 50, or 69 amino acids) was not affected by truncation. In contrast, C-terminal deletion mutants (deletion of C-terminal 45, 50, or 62 amino acids) did not have correct apical expression. A more detailed mutational analysis indicated that a domain (amino acids WLHSL) in the cytoplasmic C terminus is required for apical expression of NaPi-IIc in renal epithelial cells. We conclude that targeting of NaPi-IIc to the apical cell surface is regulated by a unique amino acid motif in the cytoplasmic C-terminal domain. © 2010 the American Physiological Society.

DOI： 10.1152/ajprenal.00189.2009

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PubMed

An apical expression signal of the renal type IIc Na+-dependent phosphate cotransporter in renal epithelial cells 査読

AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY 299 ( 1 ) F243 - F254 2010年7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

Ito M, Sakurai A, Hayashi K, Ohi A, Kangawa N, Nishiyama T, Sugino S, Uehata Y, Kamahara A, Sakata M, Tatsumi S, Kuwahata M, Taketani Y, Segawa H, Miyamoto K. An apical expression signal of the renal type IIc Na+-dependent phosphate cotransporter in renal epithelial cells. Am J Physiol Renal Physiol 299: F243-F254, 2010. First published April 21, 2010; doi: 10.1152/ajprenal.00189.2009.-The type IIc Na+-dependent phosphate cotransporter (NaPi-IIc) is specifically targeted to, and expressed on, the apical membrane of renal proximal tubular cells and mediates phosphate transport. In the present study, we investigated the signals that determine apical expression of NaPi-IIc with a focus on the role of the N- and the C-terminal tails of mouse NaPi-IIc in renal epithelial cells [opossum kidney (OK) and Madin-Darby canine kidney cells]. Wild-type NaPi-IIc, the cotransporter NaPi-IIa, as well as several IIa-IIc chimeras and deletion mutants, were fused to enhanced green fluorescent protein (EGFP), and their cellular localization was analyzed in polarized renal epithelial cells by confocal microscopy and by cell-surface biotinylation. Fluorescent EGFP-fused NaPi-IIc transporter proteins are correctly expressed in the apical membrane of OK cells. The apical expression of N-terminal deletion mutants (deletion of N-terminal 25, 50, or 69 amino acids) was not affected by truncation. In contrast, C-terminal deletion mutants (deletion of C-terminal 45, 50, or 62 amino acids) did not have correct apical expression. A more detailed mutational analysis indicated that a domain (amino acids WLHSL) in the cytoplasmic C terminus is required for apical expression of NaPi-IIc in renal epithelial cells. We conclude that targeting of NaPi-IIc to the apical cell surface is regulated by a unique amino acid motif in the cytoplasmic C-terminal domain.

DOI： 10.1152/ajprenal.00189.2009

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PubMed

Phosphaturic action of fibroblast growth factor 23 in Npt2 null mice. 国際誌

Tomoe Y, Segawa H, Shiozawa K, Kaneko I, Tominaga R, Hanabusa E, Aranami F, Furutani J, Kuwahara S, Tatsumi S, Matsumoto M, Ito M, Miyamoto K.

Am J Physiol Renal Physiol. 298 ( 6 ) F1341 - F1350 2010年6月

Phosphaturic action of fibroblast growth factor 23 in Npt2 null mice 査読

Yuka Tomoe, Hiroko Segawa, Kazuyo Shiozawa, Ichiro Kaneko, Rieko Tominaga, Etsuyo Hanabusa, Fumito Aranami, Junya Furutani, Shoji Kuwahara, Sawako Tatsumi, Mitsutu Matsumoto, Mikiko Ito, Ken-ichi Miyamoto

AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY 298 ( 6 ) F1341 - F1350 2010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：AMER PHYSIOLOGICAL SOC

Tomoe Y, Segawa H, Shiozawa K, Kaneko I, Tominaga R, Hanabusa E, Aranami F, Furutani J, Kuwahara S, Tatsumi S, Matsumoto M, Ito M, Miyamoto K. Phosphaturic action of fibroblast growth factor 23 in Npt2 null mice. Am J Physiol Renal Physiol 298: F1341-F1350, 2010. First published March 31, 2010; doi: 10.1152/ajprenal.00375.2009.-In the present study, we evaluated the roles of type II and type III sodium-dependent P(i) cotransporters in fibroblast growth factor 23 (FGF23) activity by administering a vector encoding FGF23 with the R179Q mutation (FGF23M) to wild-type (WT) mice, Npt2a knockout (KO) mice, Npt2c KO mice, and Npt2a(-/-)Npt2c(-/-) mice (DKO mice). In Npt2a KO mice, FGF23M induced severe hypophosphatemia and markedly decreased the levels of Npt2c, type III Na-dependent P(i) transporter (PiT2) protein, and renal Na/P(i) transport activity. In contrast, in Npt2c KO mice, FGF23M decreased plasma phosphate levels comparable to those in FGF23M-injected WT mice. In DKO mice with severe hypophosphatemia, FGF23M administration did not induce an additional increase in urinary phosphate excretion. FGF23 administration significantly decreased intestinal Npt2b protein levels in WT mice but had no effect in Npt2a, Npt2c, and DKO mice, despite marked suppression of plasma 1,25(OH)(2)D(3) levels in all the mutant mice. The main findings were as follow: 1) FGF23-dependent phosphaturic activity in Npt2a KO mice is dependent on renal Npt2c and PiT-2 protein; 2) in DKO mice, renal P(i) reabsorption is not further decreased by FGF23M, but renal vitamin D synthesis is suppressed; and 3) downregulation of intestinal Npt2b may be mediated by a factor(s) other than 1,25(OH)(2)D(3). These findings suggest that Npt2a, Npt2c, and PiT-2 are necessary for the phosphaturic activity of FGF23. Thus complementary regulation of Npt2 family proteins may be involved in systemic P(i) homeostasis.

DOI： 10.1152/ajprenal.00375.2009

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PubMed

Phosphaturic action of fibroblast growth factor 23 in Npt2 null mice 査読

American Journal of Physiology - Renal Physiology 298 ( 6 ) F1341 - F1350 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

In the present study, we evaluated the roles of type II and type III sodium-dependent Pi cotransporters in fibroblast growth factor 23 (FGF23) activity by administering a vector encoding FGF23 with the R179Q mutation (FGF23M) to wild-type (WT) mice, Npt2a knockout (KO) mice, Npt2c KO mice, and Npt2a-/-Npt2c-/- mice (DKO mice). In Npt2a KO mice, FGF23M induced severe hypophosphatemia and markedly decreased the levels of Npt2c, type III Na-dependent Pi transporter (PiT2) protein, and renal Na/Pi transport activity. In contrast, in Npt2c KO mice, FGF23M decreased plasma phosphate levels comparable to those in FGF23M-injected WT mice. In DKO mice with severe hypophosphatemia, FGF23M administration did not induce an additional increase in urinary phosphate excretion. FGF23 administration significantly decreased intestinal Npt2b protein levels in WT mice but had no effect in Npt2a, Npt2c, and DKO mice, despite marked suppression of plasma 1,25(OH)2D3 levels in all the mutant mice. The main findings were as follow: 1) FGF23-dependent phosphaturic activity in Npt2a KO mice is dependent on renal Npt2c and PiT-2 protein
2) in DKO mice, renal Pi reabsorption is not further decreased by FGF23M, but renal vitamin D synthesis is suppressed
and 3) downregulation of intestinal Npt2b may be mediated by a factor(s) other than 1,25(OH)2D3. These findings suggest that Npt2a, Npt2c, and PiT-2 are necessary for the phosphaturic activity of FGF23. Thus complementary regulation of Npt2 family proteins may be involved in systemic Pi homeostasis. Copyright © 2010 the American Physiological Society.

DOI： 10.1152/ajprenal.00375.2009

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PubMed

新規リン利尿因子の探索

野村憲吾, 辰巳佐和子, 菊井聡子, 齋藤友紀子, 塩崎雄治, 山口誠一, 木戸慎介, 宮本賢一

日本栄養・食糧学会大会講演要旨集 64回 105 - 105 2010年5月

Fibroblast growth factor 23 mediates the phosphaturic actions of cadmium. 国際誌

Aranami F, Segawa H, Furutani J, Kuwahara S, Tominaga R, Hanabusa E, Tatsumi S, Kido S, Ito M, Miyamoto K.

J Med Invest. 57 ( 1,2 ) 95 - 108 2010年2月

Fibroblast growth factor 23 mediates the phosphaturic actions of cadmium 査読

Fumito Aranami, Hiroko Segawa, Junya Furutani, Shoji Kuwahara, Rieko Tominaga, Etsuyo Hanabusa, Sawako Tatsumi, Shinsuke Kido, Mikiko Ito, Ken-Ichi Miyamoto

Journal of Medical Investigation 57 ( 1-2 ) 95 - 108 2010年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Phosphaturia has been documented following cadmium (Cd) exposure in both humans and experimental animals. The fibroblast growth factor 23 (FGF23)/klotho axis serves as an essential phosphate homeostasis pathway in the bone-kidney axis. In the present study, we investigated the effects of Cd on phosphate (Pi) homeostasis in mice. Following Cd injection into WT mice, plasma FGF23 concentration was significantly increased. Urinary Pi excretion levels were significantly higher in Cd-injected WT mice than in control group. Plasma Pi concentration decreased only slightly compared with control group. No change was observed in plasma parathyroid hormone and 1,25-dihydroxy vitamin D3 in both group of mice. We observed a decrease in phosphate transport activity and also decrease in expression of renal phosphate transporter SLC34A3 [NaPi-IIc/NPT2c], but not SLC34A1 [NaPi-IIa/NPT2a]. Furthermore, we examined the effect of Cd on Npt2c in Npt2a-knockout (KO) mice which expresses Npt2c as a major NaPi co-transporter. Injecting Cd to Npt2aKO mice induced significant increase in plasma FGF23 concentration and urinary Pi excretion levels. Furthermore, we observed a decrease in phosphate transport activity and renal Npt2c expression in Cd-injected Npt2a KO mice. The present study suggests that hypophosphatemia induced by Cd may be closely associated with the FGF23/klotho axis.

DOI： 10.2152/jmi.57.95

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PubMed

Localization of polypyrimidine-tract-binding protein is involved in the regulation of albumin synthesis by branched-chain amino acids in HepG2 cells. 国際誌

Kuwahata M, Yoshimura T, Sawai Y, Amano S, Tomoe Y, Segawa H, Tatsumi S, Ito M, Ishizaki S, Ijichi C, Sonaka I, Oka T, Miyamoto K.

J Nutr Biochem. 19 ( 7 ) 438 - 447 2008年7月

Localization of polypyrimidine-tract-binding protein is involved in the regulation of albumin synthesis by branched-chain amino acids in HepG2 cells 査読

Masashi Kuwahata, Tomoyo Yoshimura, Yukiko Sawai, Saki Amano, Yuka Tomoe, Hiroko Segawa, Sawako Tatsumi, Mikiko Ito, Sonoko Ishizaki, Chiori Ijichi, Ichiro Sonaka, Tatsuzo Oka, Ken-ichi Miyamoto

JOURNAL OF NUTRITIONAL BIOCHEMISTRY 19 ( 7 ) 438 - 447 2008年7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 INC

Long-term supplementation of branched-chain amino acids (BCAA) improves hypoalbuminemia in patients with cirrhosis. Our previous findings have suggested that the binding of polypyrimidine-tract-binding protein (PTB) to rat albumin mRNA attenuates its translation. The aim of the present study was to investigate the role of PTB in the regulation of albumin synthesis by BCAA in human hepatoma cells. HepG2 cells were cultured in a medium containing no amino acids (AA-free medium), a medium containing only I amino acid (a BCAA: valine, leucine or isoleucine) or a medium containing all 20 amino acids (AA-complete medium). HepG2 cells cultured in AA-complete medium secreted much more albumin than cells cultured in AA-free medium, with no difference in albumin mRNA levels. In cells cultured in AA-free medium, nuclear export of PTB was observed, and the level of the albumin mRNA-PTB complex was greater than in cells cultured in AA-complete medium. Addition of amino acids stimulated nuclear import of PTB. However, addition of amino acids with rapamycin inhibited the nuclear import of PTB. The addition of leucine, but not of valine or isoleucine, to AA-free medium increased albumin secretion and stimulated the nuclear import of PTB. These data indicate that the mammalian target of rapamycin is involved in the regulation of PTB localization and that leucine promotes albumin synthesis by inhibiting the formation of the albumin mRNA-PTB complex. (c) 2008 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jnutbio.2007.05.01

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Polypyrimidine tract-binding protein is involved in regulation of albumin synthesis in response to food intake. 国際誌

Kuwahata M, Kuramoto Y, Sawai Y, Amano S, Tomoe Y, Segawa H, Tatsumi S, Ito M, Kobayashi Y, Kido Y, Oka T, Miyamoto K.

J Nutr Sci Vitaminol (Tokyo). 54 ( 2 ) 142 - 147 2008年4月

Polypyrimidine tract-binding protein is involved in regulation of albumin synthesis in response to food intake 査読

Masashi Kuwahata, Yasuko Kuramoto, Yukiko Sawai, Saki Amano, Yuka Tomoe, Hiroko Segawa, Sawako Tatsumi, Mikiko Ito, Yukiko Koayashi, Yasuhiro Krdo, Tatsuzo Oka, Ken-Ichi Miyamoto

JOURNAL OF NUTRITIONAL SCIENCE AND VITAMINOLOGY 54 ( 2 ) 142 - 147 2008年4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：CENTER ACADEMIC PUBL JAPAN

Our recent study demonstrates that polypyrimidine tract-binding protein (PTB), which is a sequence specific RNA-binding protein, attenuates albumin synthesis in a cell-free translation system. In this study, the effects of food intake on regulation of albumin synthesis through binding of PTB to albumin messenger RNA (mRNA) were investigated. Rats were divided into 1 of 3 groups: fed; fasted for 36 h; or fasted for 36 h and then refed for 24 h. No significant differences in albumin mRNA levels were found among fed, fasted and refed rats. However, a decrease in the proportion of albumin mRNA associated with polysomes was identified in fasted rats. Furthermore, UV-cross linking analysis demonstrated that levels of albumin mRNA-PTB complex were increased in liver extracts from fasted rats. No significant differences in PTB levels in liver homogenate were found among the experimental groups. However, PTB level in the cytoplasmic fraction was higher in fasted rats than in fed rats. In refed rats, PTB level in the cytoplasmic fraction returned to a level comparable to that in fed rats, but was inhibited by treatment with rapamycin, a mammalian target of rapamycin (mTOR) inhibitor. These results suggest that localization of PTB is regulated by food intake through mTOR signaling, and alterations in level of albumin mRNA-PTB complex play a role in mediating the effects of food intake on albumin synthesis in the rat liver.

DOI： 10.3177/jnsv.54.142

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Life-long caloric restriction reveals biphasic and dimorphic effects on bone metabolism in rodents. 国際誌

Tatsumi S*, Ito M, Asaba Y, Tsutsumi K, Ikeda K.

Endocrinology. 149 ( 2 ) 634 - 641 2008年2月

Life-long caloric restriction reveals biphasic and dimorphic effects on bone metabolism in rodents 査読

Sawako Tatsumi, Masako Ito, Yutaro Asaba, Kumi Tsutsumi, Kyoji Ikeda

ENDOCRINOLOGY 149 ( 2 ) 634 - 641 2008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：ENDOCRINE SOC

Caloric restriction (CR) extends the lifespan of various organisms and slows the onset of age-related disorders; however, little is known about the long-term effects of CR per se on bone. In the present study, we have examined the effects of life-long CR vs. ad libitum (AD) feeding, mainly on the trabecular bone of proximal tibiae in male C57BL/ 6 mice and F344 rats. Micro-computed tomography scanning of tibiae revealed that CR for 3-9 months caused a substantial decrease in three-dimensional bone volume with structural derangements. Bone histomorphometry revealed the reduced bone mass was due mainly to suppression of bone formation. In db/ db mice with defective leptin receptor, CR was unable to decrease bone mass and suppress bone formation. The effect of CR on bone mass was inhibited by administration of a beta-adrenergic renergic blocker, propranolol. Thus, CR may regulate bone formation through leptin signaling and elevated sympathetic nervous tone. Interestingly, the difference in bone volume between the CR and AD groups disappeared after 1 yr of age, and mice and rats on an additional extension of CR to natural death maintained higher bone mass than the AD groups, with reduced bone turnover, suggesting that CR slows skeletal aging by regulating the rate of bone turnover. This is the first report, to our knowledge, that has examined the effects of lifelong CR on bone metabolism and trabecular microstructure and documents its contrasting effects during maturation vs. the postmaturational, involutional period.

DOI： 10.1210/en.2007-1089

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[New aspect of renal phosphate reabsorption and phosphate metabolism]. 査読

Miyamoto K, Tatsumi S, Ito M, Segawa H

Clinical calcium 17 ( 10 ) 1485 - 1492 2007年10月

Control of phosphate appetite in young rats. 国際誌

Ohnishi R, Segawa H, Kawakami E, Furutani J, Ito M, Tatsumi S, Kuwahata M, Miyamoto K.

J Med Invest. 54 ( 3, 4 ) 366 - 369 2007年8月

New aspect of renal phosphate reabsorption: the type IIc sodium-dependent phosphate transporter. 招待国際誌

Miyamoto K, Ito M, Tatsumi S, Kuwahata M, Segawa H.

Am J Nephrol. 27 ( 5 ) 503 - 5015 2007年8月

Targeted ablation of osteocytes induces osteoporosis with defective mechanotransduction. 国際誌

Tatsumi S, Ishii K, Amizuka N, Li M, Kobayashi T, Kohno K, Ito M, Takeshita S, Ikeda K.

Cell Metab. 5 ( 6 ) 464 - 475 2007年6月

Overexpression of gamma-glutamyltransferase in transgenic mice accelerates bone resorption and causes osteoporosis. 国際誌

Hiramatsu K, Asaba Y, Takeshita S, Nimura Y, Tatsumi S, Katagiri N, Niida S, Nakajima T, Tanaka S, Ito M, Karsenty G, Ikeda K.

Endocrinology. 148 ( 6 ) 2708 - 2715 2007年6月

Overexpression of gamma-glutamyltransferase in transgenic mice accelerates bone resorption and causes osteoporosis 査読

Kiyoshi Hiramatsu, Yutaro Asaba, Sunao Takeshita, Yuji Nimura, Sawako Tatsumi, Nobuyoshi Katagiri, Shumpei Niida, Toshihiro Nakajima, Sakae Tanaka, Masako Ito, Gerard Karsenty, Kyoji Ikeda

ENDOCRINOLOGY 148 ( 6 ) 2708 - 2715 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：ENDOCRINE SOC

We previously identified gamma-glutamyltransferase (GGT) by expression cloning as a factor inducing osteoclast formation in vitro. To examine its pathogenic role in vivo, we generated transgenic mice that overexpressed GGT in a tissue-specific manner utilizing the Cre-loxP recombination system. Systemic as well as local production of GGT accelerated osteoclast development and bone resorption in vivo by increasing the sensitivity of bone marrow macrophages to receptor activator of nuclear factor-kappa B ligand, an essential cytokine for osteoclastogenesis. Mutated GGT devoid of enzyme activity was as potent as the wild-type molecule in inducing osteoclast formation, suggesting that GGT acts not as an enzyme but as a cytokine. Recombinant GGT protein increased receptor activator of nuclear factor-kappa B ligand expression in marrow stromal cells and also stimulated osteoclastogenesis from bone marrow macrophages at lower concentrations. Thus, GGT is implicated as being involved in diseases characterized by accelerated osteoclast development and bone destruction and provides a new target for therapeutic intervention.

DOI： 10.1210/en.2007-0215

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