Gi蛋白βγ亚单位在氨甲酰胆碱所致CCL137细胞磷脂酰A_2激活中的作用

Involvement of Giβγ subunits in carbacholstimulated phospholipase A2 activation in CCL137 cells

为研究氨甲酰胆碱（ＣＣｈ）所致ＣＣＬ１３７细胞中毒蕈碱型乙酰胆碱受体（ｍＡＣｈＲ）失敏时磷脂酶Ａ２（ＰＬＡ２）激活的机理，应用百日咳杆菌毒素（ＰＴＸ），抗－βγ血清和纯化的Ｇｉβγ，分别观察了它们对ＰＬＡ２活性的影响．当在培养液中加入ＰＴＸ或抗－βγ血清时，可见ＣＣｈ不再能引起ＣＣＬ１３７细胞中ｍＡＣｈＲ失敏和ＰＬＡ２激活．反之，加入Ｇｉβγ或ＧＴＰ－γ－Ｓ则使ＰＬＡ２激活，且呈剂量依赖关系，前者尤为明显．结果表明，Ｇｉβγ在ＣＣｈ所致ＣＣＬ１３７细胞的ＰＬＡ２激活中起重要作用．

That the activation of phospholipase A2 (PLA2)played an important role in carbacholinduced desensitization of mAChR has been reported previously by us. In the present study, pertussis toxin(PTX), antiβγ sera and purified Giβγ from bovine brain were used to elucidate the mechanism of PLA2 activation. The mAChR desensitization and PLA2 activation induced by carbachol were abolished when PTX or antiGiβγ serum was involved in the reaction system. On the other hand, the addition of Giβγ or GTPγS, which binds to Gα subunit with high affinity and releases free Gβγ, activated phospholipase A2 in a concentrationdependent manner. These data suggest that the Giβγ subunit is involved in the carbacholinduced activation of PLA2 in CCL137 cells.