Functionally Selective Dopamine D1 Receptor Endocytosis and Signaling by Catechol and Noncatechol Agonists

Area of Science:

• Neuropharmacology
• Molecular Pharmacology

Background:

• The dopamine D1 receptor (D1R) is crucial for movement and memory, making it a key drug target.
• Existing D1R agonists have poor pharmacokinetics due to their catechol structure.
• Novel non-catechol D1R agonists exhibit biased signaling, influencing receptor function.

Purpose of the Study:

• To investigate functional selectivity of catechol and non-catechol D1R agonists.
• To determine the impact of biased signaling on D1R endocytosis.
• To explore the relationship between β-arrestin2 recruitment and D1R endocytosis.

Main Methods:

• Assessed G protein and β-arrestin2 signaling for various D1R agonists.
• Quantified agonist-induced D1R endocytosis.
• Correlated β-arrestin2 recruitment efficacy with D1R endocytosis.

Main Results:

• Most non-catechol D1R agonists displayed G protein biased signaling with reduced β-arrestin2 recruitment.
• Compound 19 showed balanced signaling, while A-77636 was a β-arrestin2 super agonist.
• Balanced agonists and the β-arrestin2 super agonist induced D1R endocytosis; G protein biased agonists did not.

Conclusions:

• Functional selectivity of D1R agonists significantly impacts D1R endocytosis, irrespective of the pharmacophore.
• β-arrestin2 recruitment efficacy strongly correlates with the extent of D1R endocytosis.
• These findings offer valuable tools for studying D1R signaling, trafficking, and therapeutic applications.