SH3 binding domains in the dopamine D4 receptor

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• The dopamine D4 receptor is a G protein-coupled receptor (GPCR) in the dopamine D2-like family.
• D2-like receptors typically inhibit adenylyl cyclase.
• Dopamine D4 receptors possess putative SH3 binding domains, particularly in the third intracellular loop.

Purpose of the Study:

• To investigate the interaction of the dopamine D4 receptor's third intracellular loop with SH3 domains.
• To determine the role of SH3 binding sites in dopamine D4 receptor function and signaling.

Main Methods:

• Utilized interaction studies to assess the binding of various SH3 domains to the D4 receptor.
• Generated deletion mutants of the D4 receptor lacking SH3 binding domains.
• Assessed ligand binding, G protein coupling, adenylyl cyclase and MAPK activity, and receptor internalization in mutant receptors.

Main Results:

• The third intracellular loop of the dopamine D4 receptor interacts with diverse SH3 domains, notably with adapter proteins Grb2 and Nck.
• SH3 domain interaction involves cooperative binding to sites flanking the repeat sequence, not the repeat itself.
• D4 receptor mutants lacking SH3 binding domains retained ligand binding but showed impaired dopamine-mediated adenylyl cyclase and MAPK modulation.
• These mutants exhibited constitutive internalization, suggesting a link between SH3 sites, internalization, and functional signaling.

Conclusions:

• The dopamine D4 receptor contains functional SH3 binding sites within its third intracellular loop.
• These SH3 binding sites are critical for regulating receptor internalization and subsequent functional signaling.
• SH3 domain interactions play a significant role in the downstream signaling of the dopamine D4 receptor.