Niacin receptor 1

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Hydroxycarboxylic acid receptor 2
Symbols HCAR2 ; GPR109A; HCA2; HM74a; HM74b; NIACR1; PUMAG; Puma-g
External IDs OMIM609163 MGI1933383 HomoloGene4391 IUPHAR: 312 ChEMBL: 3785 GeneCards: HCAR2 Gene
Species Human Mouse
Entrez 338442 80885
Ensembl ENSG00000182782 ENSMUSG00000045502
UniProt Q8TDS4 Q9EP66
RefSeq (mRNA) NM_177551 NM_030701
RefSeq (protein) NP_808219 NP_109626
Location (UCSC) Chr 12:
123.19 – 123.19 Mb
Chr 5:
123.86 – 123.87 Mb
PubMed search [1] [2]

Niacin receptor 1, also known as NIACR1 or GPR109A, is a protein which in humans is encoded by the NIACR1 gene.[1][2][3][4]


GPR109A is a high-affinity receptor for nicotinic acid (niacin),[3][4] and is a member of the nicotinic acid receptor family of G protein-coupled receptors (the other identified member being Niacin receptor 2, also known as GPR109B).

GPR109A is a Gi / Go protein-coupled receptor with high affinity for nicotinic acid.[3]

Clinical significance[edit]

Niacin receptor 1 is an important biomolecular target of niacin which is a widely prescribed drug for the treatment of dyslipidemia and to increase HDL cholesterol but whose therapeutic use is limited by flushing.[5] In NIACR1 knockout mice, the effects of niacin on both lipids[6] and flushing[7] is eliminated. Furthermore, in arrestin beta 1 knockout mice, niacin's effect on flushing is greatly reduced while the lipid modifying effects are maintained.[8]

The precise mechanism of action of niacin therapeutic effects has not been fully elucidated, but appears to work in part through activation of NIACR1 which reduces the levels of intracellular cAMP thereby inhibiting lipolysis in adipocytes.[9] In contrast, the flushing effect is due to NIACR1 activation of ERK 1/2 MAP kinase[10] mediated by arrestin beta 1.[8] Activation of MAP kinase in turn causes release of prostaglandin D2 from Langerhans cells in the skin.[11]


The mouse ortholog of NIACR1, Niacr1, has recently been proposed to mediate the ability of 5-oxo-ETE, a member of the 5-HETE family of eicosanoids, to stimulate the production of steroidogenic acute regulatory protein mRNA, Steroidogenic acute regulatory protein, and thereby progesterone in mouse cultured MA-10 Leydig cells.[12] Human tissues respond to 5-oxo-ETE and other 5-HETE family members though the OXER1 G protein-coupled receptor. The roles, if any, of Niacr1 in the response of leydig cells to other 5-HETE family members, of Niacr1 in the response of other mouse cells to 5-HETE family members, and the role of NIACR1 in the response of human tissues to 5-HETE family members has not been determined.


  1. ^ Takeda S, Kadowaki S, Haga T, Takaesu H, Mitaku S (Jun 2002). "Identification of G protein-coupled receptor genes from the human genome sequence". FEBS Letters 520 (1-3): 97–101. doi:10.1016/S0014-5793(02)02775-8. PMID 12044878. 
  2. ^ "Entrez Gene: GPR109A G protein-coupled receptor 109A". 
  3. ^ a b c Wise A, Foord SM, Fraser NJ, Barnes AA, Elshourbagy N, Eilert M et al. (Mar 2003). "Molecular identification of high and low affinity receptors for nicotinic acid". The Journal of Biological Chemistry 278 (11): 9869–74. doi:10.1074/jbc.M210695200. PMID 12522134. 
  4. ^ a b Soga T, Kamohara M, Takasaki J, Matsumoto S, Saito T, Ohishi T et al. (Mar 2003). "Molecular identification of nicotinic acid receptor". Biochemical and Biophysical Research Communications 303 (1): 364–9. doi:10.1016/S0006-291X(03)00342-5. PMID 12646212. 
  5. ^ Pike NB (Dec 2005). "Flushing out the role of GPR109A (HM74A) in the clinical efficacy of nicotinic acid". The Journal of Clinical Investigation 115 (12): 3400–3. doi:10.1172/JCI27160. PMC 1297267. PMID 16322787. 
  6. ^ Tunaru S, Kero J, Schaub A, Wufka C, Blaukat A, Pfeffer K et al. (Mar 2003). "PUMA-G and HM74 are receptors for nicotinic acid and mediate its anti-lipolytic effect". Nature Medicine 9 (3): 352–5. doi:10.1038/nm824. PMID 12563315. 
  7. ^ Benyó Z, Gille A, Kero J, Csiky M, Suchánková MC, Nüsing RM et al. (Dec 2005). "GPR109A (PUMA-G/HM74A) mediates nicotinic acid-induced flushing". The Journal of Clinical Investigation 115 (12): 3634–40. doi:10.1172/JCI23626. PMC 1297235. PMID 16322797. 
  8. ^ a b Walters RW, Shukla AK, Kovacs JJ, Violin JD, DeWire SM, Lam CM et al. (May 2009). "beta-Arrestin1 mediates nicotinic acid-induced flushing, but not its antilipolytic effect, in mice". The Journal of Clinical Investigation 119 (5): 1312–1321. doi:10.1172/JCI36806. PMC 2673863. PMID 19349687. 
  9. ^ Zhang Y, Schmidt RJ, Foxworthy P, Emkey R, Oler JK, Large TH et al. (Aug 2005). "Niacin mediates lipolysis in adipose tissue through its G-protein coupled receptor HM74A". Biochemical and Biophysical Research Communications 334 (2): 729–32. doi:10.1016/j.bbrc.2005.06.141. PMID 16018973. 
  10. ^ Richman JG, Kanemitsu-Parks M, Gaidarov I, Cameron JS, Griffin P, Zheng H et al. (Jun 2007). "Nicotinic acid receptor agonists differentially activate downstream effectors". The Journal of Biological Chemistry 282 (25): 18028–36. doi:10.1074/jbc.M701866200. PMID 17452318. 
  11. ^ Tang Y, Zhou L, Gunnet JW, Wines PG, Cryan EV, Demarest KT (Jun 2006). "Enhancement of arachidonic acid signaling pathway by nicotinic acid receptor HM74A". Biochemical and Biophysical Research Communications 345 (1): 29–37. doi:10.1016/j.bbrc.2006.04.051. PMID 16674924. 
  12. ^ Cooke M, Di Cónsoli H, Maloberti P, Cornejo Maciel F (2013). "Expression and function of OXE receptor, an eicosanoid receptor, in steroidogenic cells". Mol. Cell. Endocrinol. 371 (1-2): 71–8. doi:10.1016/j.mce.2012.11.003. PMID 23159987. 

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