PTX和EGS对α_(2B)受体预结合的影响

Influence of PTX and EGS on Precoupling of α_(2B) Receptors

目的研究PTX和EGS对α_(2B)受体预结合的影响。方法使用细胞培养、膜制备和处理、同位素结合实验等。结果PTX处理含α_(2B)受体的细胞膜增加了3H-RAU结合的Bmax，降低了Kd值；存在Na+和Gpp（NH）p时处理比未处理膜的Bmax更高，减少了R／G复合物的亲和力；增加的Bmax反映了预结合的程度。EGS通过交互联结形成R／G复合物，以剂量依赖的方式减少了’H-RAU的Bmax，此作用可为Gpp（NH）和Na+所逆转。结击至少40％以上的α_(2B)受体与G蛋白预结合成R／G复合物，因而不能与3H-RAU结合。

Objective To investigate the influence of PTX and EGS on precoupling ofa2B receptors. Methods The assays of cell culture, membrane preparation and treatment,radioligand binding were applied in this research. ResuIts PTX pretreatthent membranewhich expressed a cloned a2B receptor caused an increase in Bmax fOr 3H - RAU and reducedits Kd- Whereas in the presence of Na+ and Gpp(NH)p binding was higher in the untreatedmembranes, because these agents acted to reduce R/G affinity, the increased binding mayrenect the extent of precoupling. EGs was used to crosslink precoupled receptor andG - protein. Bmax of 3H - RAU was reduced by EGS in a dose - dependent manner) and thisaction was reversed by prior incubation with Na+ and Gpp(NH)p- CoDcIusion It indicatesthat at least 40% of α_(2B) receptors exist as a precoupled R/G complex and fail to bind3H - RAU.