Conformational Sensors and Domain Swapping Reveal Structural and Functional Differences between β-Arrestin Isoforms

Area of Science:

• Molecular Biology
• Cell Signaling
• Pharmacology

Background:

• Multifunctional adaptor proteins, beta-arrestins (βarrs), regulate G-protein-coupled receptor (GPCR) desensitization, signaling, and trafficking.
• The two βarr isoforms (βarr1 and βarr2) often yield distinct functional outcomes in GPCR regulation despite high sequence and structural similarity.
• The mechanistic basis for this functional divergence remains unclear.

Purpose of the Study:

• To elucidate the structural basis for the functional divergence of βarr1 and βarr2 in GPCR regulation.
• To investigate structural differences between βarr1 and βarr2 upon interaction with activated, phosphorylated receptors.

Main Methods:

• Utilized antibody-fragment-based conformational sensors.
• Employed domain-swapped chimeras of βarr isoforms.
• Conducted functional assays to assess βarr activity.

Main Results:

• Discovered distinct structural differences between βarr1 and βarr2 when bound to activated and phosphorylated receptors.
• Demonstrated robust complementation in functional assays using domain-swapped βarr chimeras.
• Linked observed structural differences to divergent functional outcomes mediated by βarr isoforms.

Conclusions:

• βarr isoforms exhibit distinct structures upon receptor interaction, explaining their differential functional roles.
• Domain-swapping experiments confirm the link between structural variations and functional divergence.
• These findings are critical for understanding biased agonism and receptor regulation by βarrs.