ヒグチ　ケイ   Higuchi Kei   樋口　慧    所属   東邦大学  薬学部 薬学科    職種   准教授
論文種別	原著
言語種別	英語
査読の有無	査読あり
表題	System A amino acid transporter SNAT2 shows subtype-specific affinity for betaine and hyperosmotic inducibility in placental trophoblasts.
掲載誌名	正式名：Biochimica et biophysica acta ISSNコード：0006-3002
掲載区分	国外
出版社	5
巻・号・頁	1838(5),pp.1306-12
著者・共著者	Tomohiro Nishimura,Risa Yagi,Mariko Usuda,Kenji Oda,Mai Yamazaki,Sayaka Suda,Yu Takahashi,Fumiyasu Okazaki,Yoshimichi Sai,Kei Higuchi,Tetsuo Maruyama,Masatoshi Tomi,Emi Nakashima
発行年月	2014/05
概要	Betaine uptake is induced by hypertonic stress in a placental trophoblast cell line, and involvement of amino acid transport system A was proposed. Here, we aimed to identify the subtype(s) of system A that mediates hypertonicity-induced betaine uptake. Measurement of [(14)C]betaine uptake by HEK293 cells transiently transfected with human or rat sodium-coupled neutral amino acid transporters (SNATs), SNAT1, SNAT2 and SNAT4 revealed that only human and rat SNAT2 have betaine uptake activity. The Michaelis constants (Km) of betaine uptake by human and rat SNAT2 were estimated to be 5.3 mM and 4.6 mM, respectively. Betaine exclusively inhibited the uptake activity of SNAT2 among the rat system A subtypes. We found that rat SNAT1, SNAT2 and SNAT4 were expressed at the mRNA level under isotonic conditions, while expression of SNAT2 and SNAT4 was induced by hypertonicity in TR-TBT 18d-1 cells. Western blot analyses revealed that SNAT2 expression on plasma membrane of TR-TBT 18d-1 cells was more potently induced by hypertonicity than that in total cell lysate. Immunocytochemistry confirmed the induction of SNAT2 expression in TR-TBT 18d-1 cells exposed to hypertonic conditions and indicated that SNAT2 was localized on the plasma membrane in these cells. Our results indicate that SNAT2 transports betaine, and that tonicity-sensitive SNAT2 expression may be involved in regulation of betaine concentration in placental trophoblasts.
DOI	10.1016/j.bbamem.2014.01.004
PMID	24434061