RESUMEN
Most G protein-coupled receptors (GPCRs) signal through both heterotrimeric G proteins and ß-arrestins (ßarr1 and ßarr2). Although synthetic ligands can elicit biased signaling by G protein- vis-à-vis ßarr-mediated transduction, endogenous mechanisms for biasing signaling remain elusive. Here we report that S-nitrosylation of a novel site within ßarr1/2 provides a general mechanism to bias ligand-induced signaling through GPCRs by selectively inhibiting ßarr-mediated transduction. Concomitantly, S-nitrosylation endows cytosolic ßarrs with receptor-independent function. Enhanced ßarr S-nitrosylation characterizes inflammation and aging as well as human and murine heart failure. In genetically engineered mice lacking ßarr2-Cys253 S-nitrosylation, heart failure is exacerbated in association with greatly compromised ß-adrenergic chronotropy and inotropy, reflecting ßarr-biased transduction and ß-adrenergic receptor downregulation. Thus, S-nitrosylation regulates ßarr function and, thereby, biases transduction through GPCRs, demonstrating a novel role for nitric oxide in cellular signaling with potentially broad implications for patho/physiological GPCR function, including a previously unrecognized role in heart failure.