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To visualize and investigate the regulation of the localization patterns of G_s and an associated receptor during cell signaling, we produced functional fluorescent fusion proteins and imaged them in HEK-293 cells. α_s-CFP, with cyan fluorescent protein (CFP) inserted into an internal loop of α_s, localized to the plasma membrane and exhibited similar receptor-mediated activity to that of α_s. Functional fluorescent β₁γ₇ dimers were produced by fusing an amino-terminal yellow fluorescent protein (YFP) fragment to β₁ (YFP-N-β₁) and a carboxyl-terminal YFP fragment to γ₇ (YFP-C-γ₇). When expressed together, YFP-N-β₁ and YFP-C-γ₇ produced fluorescent signals in the plasma membrane that were not seen when the subunits were expressed separately. Isoproterenol stimulation of cells co-expressing α_s-CFP, YFP-N-β₁/YFP-C-γ₇, and the β₂-adrenergic receptor (β₂AR) resulted in internalization of both fluorescent …