The hydroxycarboxylic acid receptor 2 (HCAR2. also known as GPR109A) is a G protein-coupled receptor (GPCR) belonging to the hydroxycarboxylic acid receptor family. Initially identified as a high-affinity receptor for nicotinic acid (niacin), HCAR2 is activated by endogenous ligands like β-hydroxybutyrate (a ketone body) and exogenous compounds, including niacin. It is primarily expressed in immune cells (e.g., macrophages, dendritic cells), adipocytes, and epithelial tissues, where it mediates anti-inflammatory and metabolic effects. HCAR2 signaling involves coupling to Gi/o proteins, leading to reduced cAMP levels and modulation of pathways like MAPK/ERK.
Research highlights its role in lipid metabolism, inflammation, and immune regulation. HCAR2 activation by niacin contributes to its lipid-lowering effects but also causes side effects like flushing. In recent years, HCAR2 has gained attention in diseases such as atherosclerosis, neurodegenerative disorders (e.g., Alzheimer’s), and cancer, where its anti-inflammatory and immunomodulatory properties are explored. Antibodies targeting HCAR2 are essential tools for studying receptor localization, expression dynamics, and functional interactions in vitro and in vivo. They enable precise detection in techniques like immunohistochemistry, flow cytometry, and Western blotting, aiding drug development and mechanistic studies. HCAR2 antibodies also help validate therapeutic strategies aiming to modulate receptor activity in metabolic or inflammatory disorders.