Cysteine redox state regulates human β2-adrenergic receptor binding and function

Bronchoconstrictive airway disorders such as asthma are characterized by inflammation and increases in reactive oxygen species (ROS), which produce a highly oxidative environment. beta 2-adrenergic receptor (beta 2AR) agonists are a mainstay of clinical therapy for asthma and provide bronchorelaxation upon inhalation. We have previously shown that beta 2AR agonism generates intracellular ROS, an effect that is required for receptor function, and which post-translationally oxidizes beta 2AR cysteine thiols to Cys-S-sulfenic acids (Cys-S-OH). Furthermore, highly oxidative environments can irreversibly oxidize Cys-S-OH to Cys-S-sulfinic (Cys-SO2H) or S-sulfonic (Cys-SO3H) acids, which are incapable of further participating in homeostatic redox reactions (i.e., redox-deficient). The aim of this study was to examine the vitality of beta 2AR-ROS interplay and the resultant functional consequences of beta 2AR Cys-redox in the receptors native, oxidized, and redox-deficient states. Here, we show for the first time that beta 2AR can be oxidized to Cys-S-OH in situ, moreover, using both clonal cells and a human airway epithelial cell line endogenously expressing beta 2AR, we show that receptor redox state profoundly influences beta 2AR orthosteric ligand binding and downstream function. Specifically, homeostatic beta 2AR redox states are vital toward agonist-induced cAMP formation and subsequent CREB and G-protein-dependent ERK1/2 phosphorylation, in addition to beta -arrestin-2 recruitment and downstream arrestin-dependent ERK1/2 phosphorylation and internalization. On the contrary, redox-deficient beta 2AR states exhibit decreased ability to signal via either G alpha s or beta -arrestin. Together, our results demonstrate a beta 2AR-ROS redox axis, which if disturbed, interferes with proper receptor function.