Subcellular location defines GPCR signal transduction

Abstract

G protein-coupled receptors in intracellular organelles can be activated in response to membrane permeant ligands, which contributes to the diversity and specificity of agonist action. The opioid receptors (ORs) provide a striking example, where opioid drugs activate ORs in the Golgi apparatus within seconds of drug addition. Till date, our knowledge on the signaling of intracellular GPCRs remains incomplete and it is unknown if the downstream effects triggered by ORs in plasma membrane and Golgi apparatus differ. To address this gap, we first assess the recruitment of signal transducers to ORs in both compartments. We find that Golgi-localized ORs couple to Gai/o probes and are phosphorylated by GPCR kinases (GRK2/3), but unlike plasma membrane receptors, do not recruit b-arrestin or a specific Ga probe. Subsequent molecular dynamics simulations with OR-transducer complexes in model bilayers mimicking plasma membrane or Golgi composition reveal that the lipid environment promotes location selective coupling. Unbiased global analyses then show that OR activation in the plasma membrane and Golgi apparatus has strikingly different downstream effects on transcription and protein phosphorylation. Taken together, the study delineates OR signal transduction with unprecedented spatial resolution and reveals that the subcellular location defines the signaling effect of opioid drugs.

Cannabinoid Receptor Signaling is Dependent on Sub-Cellular Location

“…Next, we investigated whether these effects were directly mediated by G-protein coupling or through alternative mechanistic pathways. Heterotrimeric G proteins and adenylated cyclase have been observed not only associated to the plasma membrane but also to intracellular compartments such as endosomes or the Golgi, supporting the concept of endo-membrane based G-protein signaling(10, 11, 31, 32). Recently, it has been demonstrated that the β1-adrenergic receptor and the opioid receptor mu can both localize at the Golgi and activate Gαs and Gαi respectively (10, 11).…”

“…Emerging data are giving rise to a new signaling model where ligands bind and activate GPCR both at the cell surface and at internal membranes. For example, the B1 adrenergic receptor can stimulate an intracellular Gαs-mediated cAMP signal from the Golgi apparatus, thereby significantly contributing to the increase in cAMP levels (10), while the opioid receptors mu and delta can also couple to Gαi/o at the Golgi apparatus(11). This location bias can dramatically modulate the activity of therapeutics as it requires the drug to either be actively transported or passively diffusing to the receptor’s sub-localization.…”

GRK2 Kinases in the Primary Cilium Initiate SMOOTHENED-PKA Signaling in the Hedgehog Cascade

“…Initial attempts to visualize GRK2 in the cilium via immunofluorescence were confounded by an abundant GRK2 signal in the cell body (data not shown). Because kinase-substrate interactions are typically fleeting and dynamic 49,50 , we suspected that sensitive imaging methods capable of tracking GRK2 localization over extended time periods might reveal patterns of transient, low-level ciliary localization over the high GRK2 signal emanating from the cell body.…”

Multi-faceted roles of β-arrestins in G protein-coupled receptors endocytosis

“…The extensive dataset shown here provides a valuable resource for research in GPCR signaling. Although internalization was initially linked to receptor desensitization and resensitization, compelling pieces of evidence indicate that the receptors can induce various signaling within cellular compartments [60][61][62][63] . It has been demonstrated that some GPCRs mediate sustained G protein signaling 64 and activate the arrs-dependent mitogen-activated protein kinases at endosome 14 .…”