GPCRs are increasingly recognized to initiate signaling via heterotrimeric G proteins as they move through the endocytic network, but little is known about how relevant G protein effectors are localized. Here we report selective trafficking of adenylyl cyclase type 9 (AC9) from the plasma membrane to endosomes while adenylyl cyclase type 1 (AC1) remains in the plasma membrane, and stimulation of AC9 trafficking by ligand-induced activation of Gs-coupled GPCRs. AC9 transits a similar, dynamin-dependent early endocytic pathway as ligand-activated GPCRs. However, unlike GPCR traffic control which requires β-arrestin but not Gs, AC9 traffic control requires Gs but not β-arrestin. We also show that AC9, but not AC1, mediates cAMP production stimulated by endogenous receptor activation in endosomes. These results reveal dynamic and isoform-specific trafficking of adenylyl cyclase in the endocytic network, and a discrete role of a heterotrimeric G protein in regulating the subcellular distribution of a relevant effector.

SummaryGPCRs are increasingly recognized to initiate signaling via heterotrimeric G proteins as they move through the endocytic network, but little is known about how relevant G protein effectors are localized. Here we report dynamic trafficking of adenylyl cyclase type 9 (AC9) from the plasma membrane to endosomes, while adenylyl cyclase type 1 (AC1) remains in the plasma membrane, and stimulation of AC9 trafficking by ligand-induced activation of Gs-coupled GPCRs or Gs. AC9 transits a similar dynamin-dependent early endocytic pathway as activated GPCRs but, in contrast to GPCR trafficking which is regulated by β-arrestin but not Gs, AC9 trafficking is regulated by Gs but not β-arrestin. We also show that AC9, but not AC1, contributes to cAMP production from endosomes. These results reveal dynamic and isoform-specific trafficking of adenylyl cyclase in the endocytic network, and a discrete role of a heterotrimeric G protein in controlling subcellular location of a relevant effector.

The G protein-coupled receptor (GPCR) cascade leading to production of the second messenger cAMP is replete with pharmacologically targetable receptors and enzymes with the exception of the stimulatory G protein α subunit, Gαs. GTPases remain largely undruggable given the difficulty of displacing high affinity guanine nucleotides and the lack of other drug binding sites. We 5 explored a chemical library of 10 12 cyclic peptides in order to expand the chemical search for inhibitors of this enzyme class. We identified a macrocyclic peptide, GsIN-1, that antagonizes the GTP-bound active state of Gαs with high G protein specificity and nucleotide-binding-state selectivity. A 1.57 Å co-crystal structure reveals that GsIN-1 binds to a novel switch II / α3 pocket in Gαs and directly blocks adenylyl cyclase activation. GsIN-1 inhibits isoproterenol-stimulated 10 Gαs activation through binding to the crystallographically defined pocket. The discovery of GsIN-1 provides path for the development of state-dependent GTPase inhibitors. 15 20 One sentence summary: Targeting the previously undruggable ON-state of the GTPase Gαs with a macrocyclic peptide inhibitor.

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