Schnabolk Gloriane W, Youngblood Geri L, Sweet Douglas H
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Am J Physiol Renal Physiol. 2006 Aug;291(2):F314-21. doi: 10.1152/ajprenal.00497.2005. Epub 2006 Feb 14.
Recently, a novel Slc22 gene family member expressed in murine olfactory mucosa was identified and based on sequence homology proposed to be an organic anion transporter [Oat6 (Slc22a20); J. C. Monte, M. A. Nagle, S. A. Eraly, and S. K. Nigam. Biochem Biophys Res Commun 323: 429-436, 2004]. However, no functional data for Oat6 was reported. In the present study, we demonstrate that murine Oat6 mediates the inhibitable transport of estrone sulfate using both Xenopus oocyte expression assay and Chinese hamster ovary (CHO) cells stably transfected with mOat6 (CHO-mOat6). Uptake was virtually eliminated by probenecid and the anionic herbicide 2,4-dichlorophenoxyacetate. The organic anions ochratoxin A, salicylate, penicillin G, p-aminohippurate, and urate inhibited mOat6-mediated accumulation to varying degrees. Transport of estrone sulfate by mOat6 was demonstrated to be saturable, and K(m) estimates of 109.8 +/- 22.6 microM in oocytes and 44.8 +/- 7.3 microM in CHO-mOat6 cells were obtained. Inhibitory constants for 2,4-dichlorophenoxyacetate (15.7 +/- 2.0 microM), salicylate (49.0 +/- 4.4 microM), probenecid (8.3 +/- 2.5 microM), and penicillin G (1,450 +/- 480 microM) were also determined. Accumulation of estrone sulfate mediated by mOat6 was significantly trans-stimulated by glutarate, indicating that mOat6 functions as an organic anion/dicarboxylate exchanger. These data demonstrate for the first time that the novel murine gene Oat6 (Slc22a20) encodes a functional organic anion transporter and mOat6 is indeed the newest member of the OAT gene family.
最近，在小鼠嗅觉黏膜中表达的一种新型Slc22基因家族成员被鉴定出来，并基于序列同源性推测其为一种有机阴离子转运体[Oat6 (Slc22a20); J. C. Monte, M. A. Nagle, S. A. Eraly, and S. K. Nigam. Biochem Biophys Res Commun 323: 429 - 436, 2004]。然而，尚未有关于Oat6功能数据的报道。在本研究中，我们通过非洲爪蟾卵母细胞表达试验以及稳定转染了mOat6的中国仓鼠卵巢(CHO)细胞(CHO - mOat6)，证明小鼠Oat6介导硫酸雌酮的可抑制转运。丙磺舒和阴离子除草剂2,4 - 二氯苯氧乙酸几乎完全消除了摄取。有机阴离子赭曲霉毒素A、水杨酸盐、青霉素G、对氨基马尿酸盐和尿酸盐对mOat6介导的积累有不同程度的抑制作用。mOat6介导的硫酸雌酮转运具有饱和性，在卵母细胞中K(m)估计值为109.8±22.6 microM，在CHO - mOat6细胞中为44.8±7.3 microM。还测定了2,4 - 二氯苯氧乙酸(15.7±2.0 microM)、水杨酸盐(49.0±4.4 microM)、丙磺舒(8.3±2.5 microM)和青霉素G(1,450±480 microM)的抑制常数。戊二酸显著反刺激mOat6介导的硫酸雌酮积累，表明mOat6作为一种有机阴离子/二羧酸交换体发挥作用。这些数据首次证明新型小鼠基因Oat6 (Slc22a20)编码一种功能性有机阴离子转运体，且mOat6确实是OAT基因家族的最新成员。
