Identification of thyroid hormone transporters in humans: Different molecules are involved in a tissue-specific manner

Koh Fujiwara, Hisanobu Adachi, Toshiyuki Nishio, Michiaki Unno, Taro Tokui, Mitsunori Okabe, Tohru Onogawa, Takehiro Suzuki, Naoki Asano, Masayuki Tanemoto, Makoto Seki, Kenichi Shiiba, Masanori Suzuki, Yoshiaki Kondo, Kazuo Nunoki, Tooru Shimosegawa, Kazuie Iinuma, Sadayoshi Ito, Seiki Matsuno, Takaaki Abe

Research output: Contribution to journalArticlepeer-review

170 Citations (Scopus)


We have recently identified that rat organic anion transporters, polypeptide2 (oatp2) and oatp3, both of which transport thyroid hormones. However, in humans the molecular organization of the organic anion transporters has diverged, and the responsible molecule for thyroid hormone transport has not been clarified, except for human liver-specific transporter (LST-1) identified by us. In this study we isolated and characterized a novel human organic anion transporter, OATP-E from human brain. The isolated complementary DNA encodes a polypeptide of 722 amino acids with 12 transmembrane domains. A rat counterpart, oatp-E, was also identified. Homology analysis and the phylogenetic tree analysis revealed that OATP-E/oatp-E is a subfamily of the organic anion transporter. Human OATP-E transported 3,3′,5-triiodo-L-thyronine (Km, 0.9 μM), thyronine, and rT3 in a Na+-independent manner. Although the clone was isolated from the brain, OATP-E messenger RNA was abundantly expressed in various peripheral tissues. The rat counterpart, oatp-E, also transported 3,3′,5-triiodo-L-thyronine. In addition, in this study we revealed that human OATP, which is exclusively expressed in the brain, transported 3,3′,5-triiodo-L-thyronine (Km, 6.5 μM), T4 (Kin, 8.0 μM), and rTs. These data suggest that in humans, several different molecules are involved in transporting thyroid hormone: OATP in the brain, LST-1 in the liver, and OATP-E in peripheral tissues.

Original languageEnglish
Pages (from-to)2005-2012
Number of pages8
Issue number5
Publication statusPublished - 2001


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