Selective expression of muscarinic acetylcholine receptor subtype M3 by mouse type III taste bud cells.
Selective expression of muscarinic acetylcholine receptor subtype M3 by mouse type III taste bud cells.
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DOI：
10.1007/s00424-016-1879-5
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发表时间：
2016-11
期刊：
影响因子：
--
通讯作者：
Ohtubo Y
中科院分区：
文献类型：
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作者：
Mori Y;Eguchi K;Yoshii K;Ohtubo Y
每种类型的味蕾细胞（TBC）对不同的味道有反应。先前，我们发现一种未识别的细胞类型在功能上表达一种毒蕈碱乙酰胆碱（ACh）受体亚型M3，并提出了其味觉反应性的ACh依赖性修饰。在本研究中，我们发现M3由III型tbc表达，这是味蕾中唯一与味觉神经纤维有突触接触的细胞类型。乙酰胆碱对小鼠蕈状tbc基底外膜的原位处理使每个味蕾2.4±1.4个细胞内Ca2+浓度升高（mean±SD, n = 14）。在Ca2+成像后，我们用荧光染料Lucifer yellow CH （LY）对II型细胞（磷脂酶Cβ2 [PLCβ2]-免疫反应细胞）进行了上标记，并研究了ach应答细胞和LY标记细胞之间的位置关系。固定后，对tbc进行免疫组织染色，以研究免疫组织化学分类细胞与ly标记细胞之间的位置关系。通过叠加ly标记细胞获得的两个位置关系叠加显示，所有的ach应答细胞都是III型细胞（突触体相关蛋白25 [SNAP-25]-免疫反应细胞）。ACh反应不需要在沐浴液中添加Ca2+。1 μM U73122抑制了乙酰胆碱的反应，而阴性对照1 μM U73343对乙酰胆碱的反应没有影响。这些结果表明，III型细胞对ACh有反应，并从细胞内储存中释放Ca2+。我们还讨论了Ca2+反应的潜在机制和M3在III型细胞中的作用。
Each taste bud cell (TBC) type responds to a different taste. Previously, we showed that an unidentified cell type(s) functionally expresses a muscarinic acetylcholine (ACh) receptor subtype, M3, and we suggested the ACh-dependent modification of its taste responsiveness. In this study, we found that M3 is expressed by type III TBCs, which is the only cell type that possesses synaptic contacts with taste nerve fibers in taste buds. The application of ACh to the basolateral membrane of mouse fungiform TBCs in situ increased the intracellular Ca2+ concentration in 2.4 ± 1.4 cells per taste bud (mean ± SD, n = 14). After Ca2+ imaging, we supravitally labeled type II cells (phospholipase C β2 [PLCβ2]-immunoreactive cells) with Lucifer yellow CH (LY), a fluorescent dye and investigated the positional relationship between ACh-responding cells and LY-labeled cells. After fixation, the TBCs were immunohistostained to investigate the positional relationships between immunohistochemically classified cells and LY-labeled cells. The overlay of the two positional relationships obtained by superimposing the LY-labeled cells showed that all of the ACh-responding cells were type III cells (synaptosomal-associated protein 25 [SNAP-25]-immunoreactive cells). The ACh responses required no added Ca2+ in the bathing solution. The addition of 1 μM U73122, a phospholipase C inhibitor, decreased the magnitude of the ACh response, whereas that of 1 μM U73343, a negative control, had no effect. These results suggest that type III cells respond to ACh and release Ca2+ from intracellular stores. We also discuss the underlying mechanism of the Ca2+ response and the role of M3 in type III cells.