Phosphorylation of protease-activated receptor-2 differentially regulates desensitization and internalization

Area of Science:

• Cellular Biology
• Molecular Pharmacology
• G protein-coupled receptor signaling

Background:

• Protease-activated receptor 2 (PAR2) is a G protein-coupled receptor activated by proteases.
• PAR2 signaling involves coupling to G alpha(q), G alpha(i), and G alpha(12/13) proteins.
• Phosphorylation and beta-arrestin binding typically regulate G protein-coupled receptor desensitization and internalization.

Purpose of the Study:

• To investigate the role of phosphorylation in regulating PAR2 signaling and trafficking.
• To determine if PAR2 C-tail phosphorylation is essential for desensitization and internalization.
• To elucidate the specific pathways involved in PAR2 desensitization and endocytosis.

Main Methods:

• Generation of a PAR2 mutant (PAR2 0P) with serine and threonine residues in the C-tail converted to alanines.
• Assessment of wild-type PAR2 and PAR2 0P phosphorylation upon agonist stimulation in mammalian cells.
• Analysis of receptor desensitization, beta-arrestin binding, and internalization pathways (dynamin, clathrin, beta-arrestin dependent/independent).

Main Results:

• Wild-type PAR2 undergoes rapid phosphorylation in its C-tail upon agonist stimulation, unlike the PAR2 0P mutant.
• PAR2 0P signaling desensitization was significantly impaired compared to wild-type PAR2.
• Wild-type PAR2 internalized via a canonical beta-arrestin-dependent pathway, while PAR2 0P internalized via a non-canonical, beta-arrestin-independent pathway.

Conclusions:

• PAR2 C-tail phosphorylation is crucial for beta-arrestin binding and uncoupling from G protein signaling.
• Phosphorylation regulates PAR2 desensitization and internalization through distinct mechanisms.
• The serine and threonine residues in the PAR2 C-tail normally inhibit constitutive internalization via a non-canonical pathway.