Oike Hideaki, Matsumoto Ichiro, Abe Keiko
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
J Comp Neurol. 2006 Feb 20;494(6):876-86. doi: 10.1002/cne.20848.
The taste buds are composed of heterogeneous cell populations with diverse properties and at different stages of maturity. It is important to define the relationships between cell properties and cell maturity to understand the molecular events involved in intracellular taste signaling. In the present study, in situ hybridization analysis indicated that group IIA phospholipase A(2) (PLA(2)-IIA) is expressed in a subset of taste bud cells. Immunohistochemical studies showed that PLA(2)-IIA was expressed in a subset of cells expressing phospholipase Cbeta2, a molecule essential for taste signaling in taste receptor cells, and also that some PLA(2)-IIA-positive cells expressed gustducin (Ggust), a bitter-taste-signaling molecule. Although PLA(2)-IIA and Ggust were expressed at similar frequencies in taste buds, bromodeoxyuridine (BrdU) chase experiments indicated that the expression of Ggust began 2 days after BrdU injection, whereas the expression of PLA(2)-IIA commenced after 4 days. In addition, PLA(2)-IIA was coexpressed with SNAP-25, a synaptosomal-associated protein. These results indicated that PLA(2)-IIA is expressed in mature taste receptor cells that possess exocytotic machinery.
味蕾由具有不同特性且处于不同成熟阶段的异质细胞群体组成。定义细胞特性与细胞成熟度之间的关系对于理解细胞内味觉信号传导所涉及的分子事件很重要。在本研究中，原位杂交分析表明，IIA 组磷脂酶 A(2)（PLA(2)-IIA）在一部分味蕾细胞中表达。免疫组织化学研究表明，PLA(2)-IIA 在表达磷脂酶 Cβ2（味觉受体细胞中味觉信号传导所必需的分子）的一部分细胞中表达，并且一些 PLA(2)-IIA 阳性细胞表达味觉传导素（Ggust），一种苦味信号分子。尽管 PLA(2)-IIA 和 Ggust 在味蕾中的表达频率相似，但溴脱氧尿苷（BrdU）追踪实验表明，Ggust 的表达在 BrdU 注射后 2 天开始出现，而 PLA(2)-IIA 的表达在 4 天后开始。此外，PLA(2)-IIA 与突触体相关蛋白 SNAP-25 共表达。这些结果表明，PLA(2)-IIA 在具有胞吐机制的成熟味觉受体细胞中表达。
