Nicotinic acid receptor subtypes and their ligands

Area of Science:

• Pharmacology
• Medicinal Chemistry
• Molecular Biology

Background:

• Nicotinic acid (niacin) was the first oral drug for high cholesterol, improving lipoprotein balance.
• Its mechanism of action was recently elucidated via the cloning of the G protein-coupled receptor HM74A (GPR109A).
• HM74A responds to nicotinic acid and beta-hydroxybutyrate, a ketone body potentially serving as the endogenous ligand.

Purpose of the Study:

• To review the pharmacology and medicinal chemistry of HM74A and the related HM74 (GPR109B) receptor.
• To discuss the developing ligand repertoire, including agonists and the lack of antagonists.
• To explore the receptor's role in nicotinic acid's side effects, such as flushing.

Main Methods:

• Review of existing literature on HM74A and HM74 receptor pharmacology.
• Analysis of mutagenesis experiments to identify ligand binding sites.
• Discussion of the receptor's presence in skin immune cells and its link to flushing.

Main Results:

• The G protein-coupled receptor HM74A has been identified as a key mediator of nicotinic acid's effects.
• Ligand repertoire for HM74A is expanding, with identified full and partial agonists.
• Mutagenesis suggests an arginine residue in transmembrane domain 3 is crucial for binding nicotinic acid.

Conclusions:

• HM74A and HM74 receptors are promising therapeutic targets for managing cholesterol levels and improving HDL.
• Understanding the HM74A receptor is crucial for developing effective treatments for dyslipidemia.
• Further research, including the development of antagonists, is needed for thorough pharmacological studies.