What are the names of different receptors in the human body?

Receptor Classification in the Human Body

The human body contains multiple major receptor families, with G protein-coupled receptors (GPCRs) representing the largest and most diverse system, organized into three main classes (A, B, and C) along with other critical receptor types including adrenergic, serotonergic, and dopaminergic receptors. 1

Major GPCR Classes

Class A GPCRs

Class A represents the largest group of GPCRs and includes numerous receptor families with diverse ligands 1:

• Adrenergic receptors: Divided into alpha (α1, α2) and beta (β1, β2, β3) subtypes 2, 3, 4

  • α1-adrenergic receptors: Further subdivided into α1A, α1B, and α1C subtypes, mediating vasoconstriction and excitatory effects 3, 4
  • α2-adrenergic receptors: Three subtypes that inhibit adenylate cyclase and regulate noradrenaline release 3, 4
  • β1-adrenergic receptors: High affinity for both noradrenaline and adrenaline, found in heart, brain, and adipose tissue 4, 5
  • β2-adrenergic receptors: Low affinity for noradrenaline, mediate smooth muscle relaxation and metabolic effects 4, 5

• Dopamine receptors: D1, D2, D3, and D4 subtypes (Ki=11-31 nM for olanzapine binding) 6, 7

• Serotonin (5-HT) receptors: Multiple subtypes including 5-HT1A, 5-HT2A/2C, 5-HT3, 5-HT4, 5-HT6, and 5-HT7 8, 6, 7

  • 5-HT3 receptors are unique as ligand-gated ion channels, unlike other 5-HT subtypes that are G-protein coupled 8

• Trace amine receptors: TA1 receptor activated by tyramine and β-phenylethylamine 1

• Free fatty acid receptors: FFA1, FFA2, and FFA3 1

• Mas-related GPCRs (MRGs): Including MRGPRD (activated by β-alanine), MRGPRX1 (activated by BAM22), and MRGPRX2 (activated by cortistatin-14) 1

• Lysophospholipid receptors: LPA, S1P, LPI, and LysoPS receptors 1

• Chemokine receptors: Including CMKLR1 1

• Oxysterol receptors: GPR183 (EBI2) activated by 7α,25-dihydroxycholesterol 1

• Cannabinoid receptors: CB2 receptors 9

Class B GPCRs

Class B includes receptors with a GPCR proteolytic site-containing stalk region 1:

• Glucagon-like peptide-1 (GLP-1) receptors: Located on myenteric plexus, regulate gastric motility 10
• Adhesion receptors: Including BAI1 and GPR56 1
• As of 2013,28 Class B receptors (excluding pseudogenes) remained classified as orphans 1

Class C GPCRs

Class C receptors possess a venus flytrap domain (VFT) in their large extracellular domain and function as obligate dimers 1:

• Metabotropic glutamate (mGlu) receptors: Including mGlu1 and mGlu5, which form homodimers stabilized by disulfide bridges 1
• GABAB receptors: Require dimerization of two distinct subunits for functional activity 1
• Calcium-sensing receptors 1
• GPRC6a: Receptor for basic amino acids 1
• T1 receptors: Receptors for sweet and umami taste compounds 1
• Orphan receptors: Including GPRC5A-D, GABABL (GPR156), GPR158, and GPR179 1
• Seven orphan receptors remained in Class C as of 2013 1

Additional Receptor Families

Histamine Receptors

• H1 receptors: Bound by olanzapine with Ki=7 nM 6

Muscarinic Receptors

• M1-M5 subtypes: Cholinergic muscarinic receptors involved in parasympathetic signaling 10, 6
  • Muscarinic receptors on GI tract increase motility via parasympathetic stimulation 10

Relaxin Family Peptide Receptors

• RXFP1, RXFP2, RXFP3, and RXFP4: Distributed across reproductive tissues, brain, heart, and other organs 1

Other Notable Receptors

• Apelin receptor: Previously designated as GPR30/APJ 1
• Kisspeptin receptor: Previously designated as GPR54 1
• Ghrelin receptor: GHS-R1a 1
• Neuropeptide B and W receptors: NPBW1 (GPR7) and NPBW2 (GPR8) 1
• Estrogen GPCR (GPER): Previously GPR30 1
• Bile acid receptor (GPBA): GPR131 1
• LGR4, LGR5, and LGR6: Receptors for R-spondins that enhance Wnt/β-catenin signaling 1

Orphan Receptors

As of 2013,57 human Class A receptors (excluding pseudogenes) remained classified as orphans without confirmed cognate ligands, representing ongoing targets for drug discovery. 1 The International Union of Basic and Clinical Pharmacology (IUPHAR) maintains updated databases tracking receptor-ligand pairings and orphan receptor status 1.

Clinical Significance

The diversity of receptor subtypes enables tissue-specific and receptor-selective drug development 2, 11:

• β2-selective agonists like terbutaline cause bronchodilation with less cardiac stimulation than nonselective agents 2, 11
• β1-selective antagonists like metoprolol control cardiac excitation while preserving pulmonary function better than nonselective blockers 2
• α1-selective blockers like prazosin evoke vasodilation with less reflex tachycardia than nonselective α-blockers 2
• 5-HT3 antagonists (ondansetron, granisetron, palonosetron) control chemotherapy-induced nausea and vomiting 8