Current HCA receptor nomenclature and receptor properties For further details, see IJzerman et al. (2010).
| Properties | HCA1 | HCA2 | HCA3 |
|---|---|---|---|
| Previous names/aliases | GPR81, GPR104, TA-GPCR, LACR, FKSG80 | GPR109A, HM74a (human), PUMA-G (mouse), HM74b, NIACR1 | GPR109B, HM74, NIACR2 |
| Genomic location | 12q24.31 (human), 5F (mouse) | 12q24.31 (human), 5F (mouse) | 12q24.31 (human) |
| Amino acid length | 346 (human), 343 (mouse) | 363 (human), 360 (mouse) | 387 (human) |
| Naturally occurring specific agonists (pEC50) | 2-OH-propanoate (2.5–2.8) | 3-OH-butyrate (3.1), nicotinic acid (6.6–7.2) | 3-OH-octanoate (5.1), 2-OH-octanoate (5.4), D-phenylalanine (5.0), D-tryptophan (5.4) |
| Specific synthetic agonists (pEC50) | acipimox (5.2–5.6) | 1-Isopropylbenzo-triazole-5-carboxylic acid (6.4), 5-methyl-5-(5-methyl-thio-phen-3-yl)-4-oxo-4,5-dihydro-furan-2-carboxylic acid (6.7) | |
| G-protein coupling | Gi/Go | Gi/Go | Gi/Go |
| Expression in human tissue | Adipocytes | Adipocytes, macrophages, neutrophils, epidermal Langerhans cells, keratinocytes, intestinal epithelial cells | Adipocytes, neutrophils, macrophages, intestinal epithelial cells |
| Cellular function | Inhibition of lipolysis | Inhibition of lipolysis, activation of immune cells | Inhibition of lipolysis, activation of immune cells |
| Phenotype of mice lacking receptor | Reduced insulin-induced antilipolysis | Lack of nicotinic acid effects on lipid plasma levels and of nicotinic acid-induced flushing |