GPCR kinases differentially modulate biased signaling downstream of CXCR3 depending on their subcellular localization
Julia Gardner1, Dylan Scott Eiger2, Chloe Hicks1
1Trinity College, Duke University, Durham, NC 27710, USA.
Abstract:
Some G protein-coupled receptors (GPCRs) demonstrate biased signaling such that ligands of the same receptor exclusively or preferentially activate certain downstream signaling pathways over others. This phenomenon may result from ligand-specific receptor phosphorylation by GPCR kinases (GRKs). GPCR signaling can also exhibit location bias because GPCRs traffic to and signal from subcellular compartments in addition to the plasma membrane. Here, we investigated whether GRKs contributed to location bias in GPCR signaling. GRKs translocated to endosomes after stimulation of the chemokine receptor CXCR3 or other GPCRs in cultured cells. GRK2, GRK3, GRK5, and GRK6 showed distinct patterns of recruitment to the plasma membrane and to endosomes depending on the identity of the biased ligand used to activate CXCR3. Analysis of engineered forms of GRKs that localized to either the plasma membrane or endosomes demonstrated that biased CXCR3 ligands elicited different signaling profiles that depended on the subcellular location of the GRK. Each GRK exerted a distinct effect on the regulation of CXCR3 engagement of β-arrestin, internalization, and activation of the downstream effector kinase ERK. Our work highlights a role for GRKs in location-biased GPCR signaling and demonstrates the complex interactions between ligands, GRKs, and cellular location that contribute to biased signaling.
Insights
GPCR kinases (GRKs) contribute to biased signaling by directing G protein-coupled receptors (GPCRs) to different cellular locations. This location bias influences downstream signaling pathways, revealing complex ligand-receptor-GRK interactions.
Area of Science:
- Cellular signaling
- Molecular pharmacology
- Biochemistry
Background:
- G protein-coupled receptors (GPCRs) exhibit biased signaling, activating specific pathways over others.
- Ligand-specific phosphorylation by GPCR kinases (GRKs) may cause biased signaling.
- GPCRs signal from various subcellular locations, leading to location bias.
Purpose of the Study:
- Investigate the role of GRKs in location bias of GPCR signaling.
- Determine if GRK translocation to endosomes contributes to biased signaling.
- Elucidate the complex interplay between ligands, GRKs, and cellular location in biased signaling.
Main Methods:
- Studied GRK translocation to plasma membrane and endosomes after GPCR stimulation.
- Utilized engineered GRKs localized to specific cellular compartments.
- Analyzed biased ligand effects on GPCR signaling profiles and downstream effectors.
Main Results:
- GRKs translocated to endosomes upon GPCR stimulation.
- Distinct GRK recruitment patterns to plasma membrane and endosomes were observed, dependent on biased ligands.
- Biased ligands induced different signaling profiles based on GRK subcellular location.
- GRKs differentially regulated CXCR3-mediated β-arrestin engagement, internalization, and ERK activation.
Conclusions:
- GRKs play a significant role in location-biased GPCR signaling.
- Cellular location of GRKs is critical in determining biased signaling outcomes.
- Complex interactions between ligands, GRKs, and subcellular localization govern biased GPCR signaling.
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