Moniri Nader H, Daaka Yehia
Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Mercer University, 3001 Mercer University Drive, Atlanta, GA 30341, United States.
Biochem Pharmacol. 2007 Jun 30;74(1):64-73. doi: 10.1016/j.bcp.2007.03.016. Epub 2007 Mar 24.
Generation of reactive oxygen species (ROS) can occur upon agonist stimulation of surface receptors to modulate downstream signaling processes. Here, we show that activation of the beta2 adrenergic receptor (beta2AR) by stimulation with the agonist isoproterenol leads to generation of ROS that is required for beta2AR signal transduction. Specifically, we show that inhibition of NADPH oxidase with diphenyliodonium chloride, inhibition of the small GTPase Rac1 with NSC23766, and inhibition of formed ROS with the antioxidant N-acetyl-L-cysteine decreases beta2AR-mediated cAMP formation, protein kinase A activation, and receptor phosphorylation and internalization, but does not impact ligand binding. The results also show that inhibition of ROS attenuates active beta2AR-mediated binding of GTP to alpha subunits of heterotrimeric G proteins. Based on these results, we propose that agonist-dependent ROS formation is needed for beta2AR signal transduction, perhaps through stabilization of active receptor conformers by redox-mediated modification of receptor and/or Galpha proteins cysteine residues.
激动剂刺激表面受体时可产生活性氧（ROS），以调节下游信号传导过程。在此，我们表明，用激动剂异丙肾上腺素刺激激活β2肾上腺素能受体（β2AR）会导致产生β2AR信号转导所需的ROS。具体而言，我们表明，用二苯基碘鎓氯化物抑制NADPH氧化酶、用NSC23766抑制小GTP酶Rac1以及用抗氧化剂N-乙酰-L-半胱氨酸抑制已形成的ROS，会降低β2AR介导的cAMP形成、蛋白激酶A激活以及受体磷酸化和内化，但不影响配体结合。结果还表明，抑制ROS会减弱活性β2AR介导的GTP与异源三聚体G蛋白α亚基的结合。基于这些结果，我们提出，β2AR信号转导可能需要激动剂依赖性的ROS形成，这可能是通过氧化还原介导的受体和/或Gα蛋白半胱氨酸残基修饰来稳定活性受体构象实现的。
