GRK and PDE4 activities underlie sustained suppression of β2 adrenergic signals

β 2 adrenergic receptors (β 2 ARs) are critical links in relaying information from the extracellular space to the intracellular environment. To better understand the physiological roles of β 2 AR regulation we monitored cAMP signals in single cells using genetically encoded cyclic nucleotide‐gated (CNG) channels expressed in HEK‐293 cells. This high resolution approach has allowed us to make several observations: Exposure of cells to isoproterenol‐triggered transient increases in cAMP levels near the plasma membrane. The decay in the transient signals was prevented when 10 μM rolipram, a PDE4 inhibitor, was included in the pipette solution. The decline in the response was not significantly altered by including 20 nM PKI, a PKA inhibitor, or 3 μM 59‐74E, a GRK inhibitor, in the pipette solution; however, the decline in the response was prevented when both PKI and 59‐74E were included. Little or no recovery of the signal was observed during the second pulse of a two pulse protocol (isoproterenol stimulation, 5 min wash, and restimulation). The amplitude of the second pulse was not altered when PKI was included in the pipette solution, but was significantly increased when 59‐74E was included. Taken together, these data indicate that GRK‐mediated β 2 AR desensitization is sufficient to cause a decline in cAMP signals, and is primarily responsible for long‐term suppression of β 2 AR‐mediated signals.