有机磷杀虫剂对M2受体磷酸化的影响

Effects of organophosphorus insecticides on G-protein coupled receptor kinase 2-mediated phosphorylation of m2 muscarinic receptors

目的研究有机磷类杀虫剂对G蛋白结合受体激酶2介导的毒蕈碱乙酰胆碱m2受体磷酸化的影响和可能存在的其他作用途径。方法将纯化的毒蕈碱乙酰胆碱m2受体,G蛋白结合受体激酶-2,[γ-p32]ATP与对氧磷(PO)、氧毒死蜱(CPO)共同保温,聚丙烯酰胺凝胶电泳分离蛋白,放射性自显影检测m2受体磷酸化结果。结果氧毒死蜱完全抑制m2受体的磷酸化,其半数抑制浓度为(IC50)70μmol/L;毒死蜱也抑制m2受体的磷酸化,而对氧磷与对硫磷不抑制m2受体的磷酸化。结论不同的有机磷杀虫剂对m2受体的磷酸化有完全不同的作用;毒死蜱阻断m2受体的磷酸化,提示有机磷杀虫剂的毒性作用存在其他途径。

Objective To explore the effect of organophosphorus insecticides（OPs） on G-protein coupled receptor kinase 2-mediated phosphorylation of m2 muscarinic receptors in vitro and to understand alternative target of the OPs for human and other animals. Methods In vitro experiments, purified m2 receptor was incubated with varying concentration of paraoxon, chlorpyrifos oxon or the parent insecticides along with G-protein coupled receptor kinase 2（GRK2） and [y-p^32] ATP. Proteins were separated by electrophoresis and autoradiograms developed. Results Chlorpyrifos oxon inhibited phosphorylation of m2 muscarinic receptors by GRK2 with a median inhibition concentration（IC50） of approximately 70/μmol/L. Chlorpyrifos also inhibited m2 receptors phosphorylation, but was less potent and less efficacious than that of chlo rpyrifos oxon. Interestingly, paraoxon and parathion had little effect on the receptor phosphorylation under the same conditions. Conclusion Chlorpyrifos oxon and chlorpyrifos may therefore alter GRK2-mediated regulatory pathways for m2 receptors by direct interaction with m2 recptor. These differential actions could contribute to differences in toxicity following exposure to different organophosphorus toxicants