脑型和味型代谢性谷氨酸受体的不同功能

VARIANT FUNCTIONS OF METABOTROPIC GLUTAMATE RECEPTORS BETWEEN TASTE AND BRAIN TYPE

目的 利用脑型及味型mGluR4在体内外的表达 ,检测两种受体结构功能上的差异 ,从而证实它们在信号转导功能上的不同。 方法 将克隆得到的脑型及味型mGluR4分别通过脂质体介导转染CHO细胞。在L MSG和L AP4的作用下 ,检测两种受体的功能。利用WesternBlot及原位杂交技术 ,分别检测它们在体内外的表达。 结果 转染脑型及味型mGluR4的CHO细胞 ,表达两种不同分子量的免疫活性蛋白 ,其中脑型分子量约为 12 0kD而味型约为 6 8kD。在L MSG和L AP4作用下 ,味型mGluR4对刺激物反应的浓度远高于脑型mGluR4。对大鼠脑组织及舌味蕾的原位杂交证明 ,mGluR4在小脑颗粒细胞有很高的表达 ,而在味蕾细胞表达率较低 ,阳性细胞仅占味蕾细胞的 5 %。 结论 味组织中的mGluR4与脑组织中mGluR4在结构和功能上有明显不同。味型mGluR4特异性表达于味蕾细胞 ,在高于脑内的浓度下 ,结合细胞外的谷氨酸 ,通过降低cAMP的浓度引发味觉信号转导。

Objective To prove the structural and functional differences between brain\|mGluR4 and taste\|mGluR4 by their expression in CHO cells. Methods Cloned genes of brain\|mGluR4 and taste\|mGluR4 were transfected into CHO cells by a method of cationic lipid.In situ hybridization and Western blot were used to detect in vivo and in vitro gene expression.The receptor functions of the transfected CHO cells were measured by using the ligands of L\|MSG and L\|AP4. Results In transfected CHO cells the proteins of taste and brain mGluR4 were expressed.Brain\|mGluR4 molecular weight was about 102kD and taste\|mGluR4 was about 68kD.Functions of different receptor were detected by cellular cAMP concentration with L\|MSG and L\|AP4.The higher concentration of L\|MSG and L\|AP4 was responded to taste\|mGluR4 expressed in CHO cells than those to the brain\|mGluR4. In situ hybridization performed in rat brain and taste buds using sense and anti\|sense mGluR4 probes with digoxigenin labeling showed a high expression of mGluR4 in granular cells of the cerebellum and a low expression in taste bud cells which were only 5% in total taste bud cells.Conclusions\ Different mGluR4 have differences of structure and function in taste and brain respectively.Taste\|mGluR4 particularly expressed in taste bud cells and bound extracellular glutamate in relatively high concentration.The similarity of its properties to MSG taste suggests that this receptor is a taste receptor for glutamate.\;[