Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
J Neurochem. 2013 Aug;126(4):451-61. doi: 10.1111/jnc.12298. Epub 2013 Jun 25.
Synthesis of acetylcholine (ACh) by non-neuronal cells is now well established and plays diverse physiologic roles. In neurons, the Na(+) -dependent, high affinity choline transporter (CHT1) is absolutely required for ACh synthesis. In contrast, some non-neuronal cells synthesize ACh in the absence of CHT1 indicating a fundamental difference in ACh synthesis compared to neurons. The aim of this study was to identify choline transporters, other than CHT1, that play a role in non-neuronal ACh synthesis. ACh synthesis was studied in lung and colon cancer cell lines focusing on the choline transporter-like proteins, a five gene family choline-transporter like protein (CTL)1-5. Supporting a role for CTLs in choline transport in lung cancer cells, choline transport was Na(+) -independent and CTL1-5 were expressed in all cells examined. CTL1, 2, and 5 were expressed at highest levels and knockdown of CTL1, 2, and 5 decreased choline transport in H82 lung cancer cells. Knockdowns of CTL1, 2, 3, and 5 had no effect on ACh synthesis in H82 cells. In contrast, knockdown of CTL4 significantly decreased ACh secretion by both lung and colon cancer cells. Conversely, increasing expression of CTL4 increased ACh secretion. These results indicate that CTL4 mediates ACh synthesis in non-neuronal cell lines and presents a mechanism to target non-neuronal ACh synthesis without affecting neuronal ACh synthesis.
非神经元细胞合成乙酰胆碱（ACh）已得到充分证实，并发挥着多种生理作用。在神经元中，Na(+)依赖性、高亲和力胆碱转运体（CHT1）是合成 ACh 的必需物质。相比之下，一些非神经元细胞在缺乏 CHT1 的情况下也能合成 ACh，这表明与神经元相比，非神经元细胞的 ACh 合成存在根本差异。本研究旨在确定除 CHT1 以外的胆碱转运体在非神经元 ACh 合成中的作用。本研究集中于胆碱转运蛋白样蛋白（CTL）1-5，研究了肺癌和结肠癌细胞系中的 ACh 合成。支持 CTLs 在肺癌细胞中参与胆碱转运，choline 转运是 Na(+)非依赖性的，并且在所有检查的细胞中均表达 CTL1-5。CTL1、2 和 5 的表达水平最高，在 H82 肺癌细胞中敲低 CTL1、2 和 5 会降低胆碱转运。CTL1、2、3 和 5 的敲低对 H82 细胞中的 ACh 合成没有影响。相比之下，CTL4 的敲低显著降低了肺癌和结肠癌细胞中的 ACh 分泌。相反，CTL4 的表达增加会增加 ACh 的分泌。这些结果表明，CTL4 介导非神经元细胞系中的 ACh 合成，并提供了一种不影响神经元 ACh 合成而靶向非神经元 ACh 合成的机制。
