Endocytosis drives active cAMP signal discrimination among natively co-expressed GPCRs

Many G protein-coupled receptors (GPCRs) initiate a second phase of signaling after activation-induced endocytosis, but GPCRs vary considerably in their ability to internalize when activated. Here we show that this fundamental trafficking difference distinguishes the downstream signaling profiles of natively co-expressed GPCRs through the cAMP cascade. We focus on signaling to the nucleus stimulated by three different Gs-coupled GPCRs that are each endogenously co-expressed in human embryonic kidney cells but differ in their ability to internalize after activation: the adenosine-2B receptor that does not detectably internalize, the vasoactive intestinal peptide receptor-1 that internalizes very rapidly, and the β2-adrenergic receptor that internalizes less rapidly. We show that each GPCR produces a distinct signaling profile differentiated by endocytosis. Our results support a model in which endocytosis compresses chemical information sensed by distinct GPCRs into a spatiotemporal cAMP code by setting receptor-specific differences in the amount and duration of cAMP production from endosomes relative to the plasma membrane and that this is 'decoded' downstream in the pathway through sequential layers of processing by cytoplasmic and nuclear PKA activities. We propose that this biological information processing strategy has parallels to how computational encoder-decoder (autoencoder) networks denoise and recognize latent patterns in complex electrical signals.