Molecular structure and function of angiotensin type 2 receptor

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Multiple angiotensin receptor isoforms exist, distinguished by ligand selectivity.
• The physiological roles of the angiotensin type 2 receptor (AT2) remain largely unknown despite its presence in fetal tissues.

Purpose of the Study:

• To determine the molecular structure of the angiotensin type 2 receptor (AT2).
• To characterize the binding properties and signaling pathways of AT2.

Main Methods:

• Expression cloning of AT2 receptor cDNA from rat pheochromocytoma cells (PC12w).
• Analysis of AT2 receptor's amino acid sequence and transmembrane domains.
• Ligand binding assays using specific AT2 ligands (125I-CGP42112A) and angiotensin II analogs.
• Investigation of AT2-mediated signaling via G protein-coupled pathways in COS-7 cells.

Main Results:

• A 2,868-nucleotide cDNA clone encoding a 363 amino acid AT2 protein with seven transmembrane domains was obtained.
• High-affinity binding to an AT2-specific ligand (Kd = 0.11 nM) and selective inhibition by PD123319 confirmed AT2 receptor characteristics.
• AT2 shares 32% amino acid identity with the angiotensin type 1 receptor (AT1), indicating evolutionary relatedness.
• Angiotensin II activation of AT2 receptors in COS-7 cells modulated protein tyrosine phosphatase activity through a pertussis toxin-sensitive G protein.

Conclusions:

• The molecular structure and binding characteristics of the AT2 receptor have been elucidated.
• AT2 receptor signaling involves pertussis toxin-sensitive G proteins, impacting cellular functions.
• The precise physiological function of AT2 in fetal development, particularly in the kidney, requires further investigation.