The conformational signature of β-arrestin2 predicts its trafficking and signalling functions

Area of Science:

• Molecular pharmacology
• Cell biology
• Biochemistry

Background:

• Arrestins are crucial cytosolic proteins regulating G-protein-coupled receptor (GPCR) functions including desensitization, internalization, trafficking, and signaling.
• Arrestin recruitment uncouples GPCRs from G proteins and targets them for internalization, while also acting as scaffolds for non-G-protein effectors.
• The precise mechanisms by which different GPCRs elicit distinct arrestin functions remain unclear.

Purpose of the Study:

• To investigate how GPCRs specify divergent arrestin functions.
• To elucidate the relationship between GPCR-ligand interactions and arrestin conformational changes.
• To determine if arrestin conformations can predict downstream signaling outcomes.

Main Methods:

• Utilized intramolecular fluorescein arsenical hairpin (FlAsH) bioluminescence resonance energy transfer (BRET) reporters.
• Monitored conformational changes in β-arrestin2 in response to GPCR activation.
• Analyzed distinct arrestin 'conformational signatures' induced by various GPCRs and ligands.

Main Results:

• GPCRs impose unique arrestin conformational signatures that correlate with receptor-arrestin complex stability.
• These signatures predict β-arrestin2's role in activating or dampening downstream signaling events.
• Ligand properties are reflected in β-arrestin2 conformation, even for distinct ligands acting on the same GPCR.
• Information regarding ligand-receptor conformation is encoded within the average β-arrestin2 conformation.

Conclusions:

• GPCRs utilize distinct arrestin conformational signatures to mediate varied signaling outcomes.
• This encoding mechanism provides insight into how a common effector (arrestin) serves diverse receptor functions.
• The findings support applications in characterizing and developing functionally selective GPCR ligands.