Choline is transported by vesicular acetylcholine transporter
Choline is transported by vesicular acetylcholine transporter
复制标题
DOI：
10.1111/j.1471-4159.2004.02746.x
复制
发表时间：
2004-11-01
影响因子：
4.7
通讯作者：
Parsons, SM
中科院分区：
文献类型：
--
作者：
Bravo, DT;Kolmakova, NG;Parsons, SM
先前发表的结果似乎表明，囊泡型乙酰胆碱转运体(VAChT)不转运胆碱(CH)。由于它特别适合于检测弱结合底物的运输，最近开发的一种检测底物结合部位跨膜重定向的方法被用来重新检查运输选择性。在PC12(A1237)细胞中表达大鼠血管紧张素转换酶(Vacht)，制备含核上清液的微囊，并用未标记的CH和四甲基铵(TMA)进行重定位实验。此外，[C-14]CH和[H-3]乙酰胆碱(ACh)也被用于优化的蓄积实验。结果表明，CH的输运能力至少与ACh相当，但亲和力比ACh低7倍。即使是TMA也可以运输，但亲和力要低26倍。鉴于在某些条件下CH(I)在末端细胞质中的浓度高于ACh，并且(Ii)是α7烟碱受体的激动剂，因此Vacht对CH的运输是有意义的。
Previously published results appeared to show that vesicular acetylcholine transporter (VAChT) does not transport choline (Ch). Because it is uniquely suited to detect transport of weakly bound substrates, a recently developed assay that detects transmembrane reorientation of the substrate binding site was used to re-examine transport selectivity. Rat VAChT was expressed in PC12(A1237) cells, postnuclear supernatant-containing microvesicles was prepared, and the reorientation assay was conducted with unlabeled Ch and tetramethylammonium (TMA). Also, [C-14]Ch and [H-3]acetylcholine (ACh) were used in an optimized accumulation assay. The results demonstrate that Ch is transported at least as well as ACh is, but with sevenfold lower affinity. Even TMA is transported, but with 26-fold lower affinity. Ch transport by VAChT is of interest in view of the possibilities that Ch (i) occurs at higher concentration than ACh does in terminal cytoplasm under some conditions, and (ii) is an agonist for alpha7 nicotinic receptors.