Olfactory receptor

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Olfactory receptors are class A G protein-coupled receptor which play a role in signal transduction to olfactory receptor neurons.

Expression

In vertebrates, the olfactory receptors are located in the cilia of the olfactory sensory neurons. In insects, olfactory receptors are located on the antennae. Sperm cells also express odor receptors, which are thought to be involved in chemotaxis to find the egg cell.

Function

Rather than binding specific ligands like most receptors, olfactory receptors display affinity for binding a range of odor molecules. Once the odorant has bound to the odor receptor, the receptor undergoes structural changes and it binds and activates the olfactory-type G protein on the inside of the olfactory receptor neuron. The G protein (Golf and/or Gs) in turn activates the lyase - adenylate cyclase - which converts ATP into cyclic AMP(cAMP). The cAMP opens cyclic nucleotide-gated ion channels which allow calcium and sodium ions to enter into the cell, depolarizing the olfactory receptor neuron and beginning an action potential which carries the information to the brain.

Diversity

There are a wide range of different odor receptors, with as many as 1,000 in the mammalian genome. Olfactory receptors may make up as much as 3% of the genome. Only a portion of these potential genes form functional odor receptors. According to an analysis of the Human genome project, humans have approximately 400 functional genes coding for olfactory receptors and approximately 600 putative pseudogenes remain.^[1]

The reason for the large number of different odor receptors is to provide a system for detecting as many different odors as possible. Even so, each odor receptor does not correspond to just one odor. Each individual odor receptor is broadly tuned to be activated by a number of similar structures.^[1][1] Like the immune system, this system allows molecules that have never been encountered before to be characterized. Also most odors activate more than one type of odor receptor. This aspect provides for the identification of an almost limitless number of different molecules.

History and research

In 2004 Linda B. Buck and Richard Axel won the Nobel Prize in Physiology or Medicine for their work on olfactory receptors.^[1][1]

In 2006 it was shown that another class of odorant receptors exist for volatile amines.^[1] This class of receptors consists of the trace amine-associated receptors (TAAR) with the exception of TAAR1 which is a receptor for thyronamines.

Unfortunately, there is still a lack of experimental structures at atomic level for olfactory receptors and structural information is essentially based on computational methods.^[1]

See also

• Receptor
• Trace amine-associated receptor
• Odorant

References

External links

• Olfactory Receptor Database
• Human Olfactory Receptor Data Exploratorium (HORDE)
• MeSH Olfactory+Receptor+Protein

v • d • e Sensory system: Olfactory system/Olfaction
Olfactory bulb • Olfactory nerve • Olfactory epithelium • Glomeruli • Olfactory mucosa • Olfactory receptor neurons • Mitral cells • Piriform cortex
Rhinencephalon • Olfactory tract • Olfactory trigone

v • d • e G protein-coupled receptors: olfactory receptors
Family 1	A1 - A2 - B1 - C1 - D2 - D4 - D5 - E1 - E2 - F1 - F2 - G1 - I1 - J1 - J2 - J4 - K1 - L1 - L3 - L4 - L6 - L8 - M1 - N1 - N2 - Q1 - S1 - S2
Family 2	A2 - A4 - A5 - A7 - A12 - A14 - A25 - A42 - AE1 - AG1 - AG2 - AJ1 - AK2 - AP1 - AT4 - B2 - B3 - B6 - B8 - B11 - C1 - C3 - D2 - D3 - F1 - F2 - G2 - G3 - G6 - H1 - H2 - J1 - J2 - J3 - K2 - L2 - L3 - L5 - L8 - L13 - M2 - M3 - M4 - M5 - M7 - S2 - T1 - T2 - T3 - T4 - T5 - T6 - T8 - T10 - T11 - T12 - T27 - T29 - T33 - T34 - T35 - V1 - V2 - W1 - W3 - W5 - Y1 - Z1
Family 3	A1 - A2 - A3 - A4
Family 4	A5 - A15 - A16 - A47 - B1 - C3 - C5 - C6 - C11 - C12 - C13 - C15 - C16 - C45 - C46 - D1 - D2 - D5 - D6 - D9 - D10 - D11 - E2 - F4 - F5 - F6 - F15 - F17 - F21 - F29 - K1 - K2 - K3 - K5 - K13 - K14 - K15 - K17 - L1 - M1 - M2 - N2 - N4 - N5 - P4 - Q3 - S1 - S2 - X1 - X2
Family 5	A1 - A2 - AC2 - AK2 - AK3 - AN1 - AP2 - AR1 - AS1 - AT1 - AU1 - AY1 - B2 - B3 - B12 - B17 - B21 - BF1 - BU1 - C1 - D13 - D14 - D16 - D18 - F1 - H1 - H2 - H6 - H14 - H15 - I1 - J2 - K1 - K2 - K3 - K4 - L1 - L2 - M1 - M3 - M8 - M9 - M10 - M11 - P2 - P3 - R1 - T1 - T2 - T3 - U1 - V1 - W2
Family 6	A2 - B1 - B2 - B3 - C1 - C2 - C3 - C4 - C6 - C65 - C68 - C70 - C74 - C75 - C76 - F1 - J1 - K2 - K3 - K6 - M1 - N1 - N2 - P1 - Q1 - S1 - T1 - V1 - X1 - Y1
Family 7	A2 - A5 - A10 - A17 - C1 - C2 - D2 - D4 - E24 - G1 - G2 - G3
Family 8	A1 - B2 - B3 - B4 - B8 - B12 - D1 - D2 - D4 - G1 - G2 - G5 - H1 - H2 - H3 - I2 - J1 - J3 - K1 - K3 - K5 - S1 - U1
Family 9	A2 - A4 - G1 - G4 - I1 - K2 - Q1 - Q2
Family 10	A2 - A3 - A4 - A5 - A6 - A7 - AD1 - C1 - D4 - G2 - G3 - G4 - G6 - G7 - G8 - G9 - H1 - H2 - H3 - H4 - H5 - J1 - J3 - J5 - J6 - K1 - K2 - P1 - Q1 - R2 - S1 - T2 - V1 - W1 - X1 - Z1
Family 11	A1 - G2 - H1 - H4 - H6 - L1
Family 12	D2 - D3
Family 13	A1 - C2 - C3 - C4 - C5 - C8 - C9 - D1 - F1 - G1 - H1 - J1
Family 17	-1
Family 51	A2 - A4 - A7 - B2 - B4 - B5 - B6 - D1 - E1 - E2 - F1 - F2 - G1 - G2 - H1 - I1 - I2 - L1 - M1 - Q1 - S1 - T1 - V1
Family 52	A1 - A4 - A5 - B2 - B4 - B6 - D1 - E1 - E2 - E4 - E5 - E6 - E8 - H1 - I1 - I2 - J3 - K1 - K2 - L1 - L2 - M1 - N1 - N2 - N4 - N5 - P1 - R1 - W1
Family 56	A1 - A3 - A4 - B1 - B4

v • d • e Transmembrane receptor: G protein-coupled receptors
Class A: Rhodopsin like	Acetylcholine (M1, M2, M3, M4, M5) - Adrenergic (α1 (A, B, D), α2 (A, B, C), β1, β2, β3) - Adrenomedullin - Anaphylatoxin (C3a, C5a) - Angiotensin (1, 2) - Apelin - Bile acid - Bombesin (BRS3, GRPR, NMBR) - Bradykinin (B1, B2) - Cannabinoid (CB1, CB2) - Chemokine - Cholecystokinin (A, B) - Dopamine (D1, D2, D3, D4, D5) - Eicosanoid (CysLT (1, 2), LTB4 (1, 2), FPRL1, OXE, Prostaglandin ((DP (1, 2), EP (1, 2, 3, 4), PGF, Prostacyclin, Thromboxane) - EBI2 - Endothelin (A, B) - Estrogen - Formyl peptide (1, L1, L2) - Free fatty acid (1, 2, 3, 4) - FSH - Galanin (1, 2, 3) - Gonadotropin-releasing hormone (1, 2) - GPR (1, 3, 4, 6, 12, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 31, 32, 33, 34, 35, 37, 39, 42, 44, 45, 50, 52, 55, 61, 62, 63, 65, 68, 75, 77, 78, 79, 82, 83, 84, 85, 87, 88, 92, 101, 103, 119, 120, 132, 135, 139, 141, 142, 146, 148, 149, 150, 151, 152, 153, 160, 161, 162, 171, 172, 173, 174, 176, 182) - Ghrelin - Histamine (H1, H2, H3, H4) - Kisspeptin - Luteinizing hormone/choriogonadotropin - Lysophospholipid (1, 2, 3, 4, 5, 6, 7, 8) - MAS (1, 1L, D, E, F, G, X1, X2, X3, X4) - Melanocortin (1, 2, 3, 4, 5) - MCHR (1, 2) - Melatonin (1A, 1B)- Motilin - Neuromedin (B, U (1, 2)) - Neuropeptide (B/W (1, 2), FF (1, 2), S, Y (1, 2, 4, 5)) - Neurotensin (1, 2) - Opioid (Delta, Kappa, Mu, Nociceptin, but not Sigma) - Olfactory - Opsin (3, 4, 5, 1LW, 1MW, 1SW, RGR, RRH) - Orexin (1, 2) - Oxytocin - Oxoglutarate - PAF - Prokineticin (1, 2) - Prolactin-releasing peptide - Protease-activated (1, 2, 3, 4) - Purinergics (Adenosine (A1, A2a, A2b, A3), P2Y, (1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14)) - Relaxin (1, 2, 3, 4) - Somatostatin (1, 2, 3, 4, 5) - Serotonin, all but 5-HT3 (5-HT1 (A, B, D, E, F), 5-HT2 (A, B, C), 5-HT (4, 5A, 6, 7)) - SREB - Succinate - TAAR (1, 2, 3, 5, 6, 8, 9) - Tachykinin (1, 2, 3) - Thyrotropin - Thyrotropin-releasing hormone - Urotensin-II - Vasopressin (1A, 1B, 2)
Class B: Secretin like	Brain-specific angiogenesis inhibitor (1, 2, 3) - Cadherin (1, 2, 3) - Calcitonin - CD97 - Corticotropin-releasing hormone (1, 2) - EMR (1, 2, 3) - Glucagon (GR, GIPR, GLP1R, GLP2R) - Growth hormone releasing hormone - PACAPR1- GPR (56, 64, 97, 98, 110, 111, 112, 113, 114, 115, 116, 123, 124, 125, 126, 128, 133, 143, 144, 157) - Latrophilin (1, 2, 3, ELTD1) - Parathyroid hormone (1, 2) - Secretin - Vasoactive intestinal peptide (1, 2)
Class C: Metabotropic glutamate / pheromone	Calcium-sensing receptor - GABA B (1, 2) - Glutamate receptor (Metabotropic glutamate (1, 2, 3, 4, 5, 6, 7, 8)) - GPRC6A - GPR (156, 158, 179) - RAIG (1, 2, 3, 4) - Taste receptors (TAS1R (1, 2, 3) TAS2R (1, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50))
Frizzled / Smoothened	Frizzled (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) - Smoothened

v • d • e Membrane proteins, receptors: transmembrane receptors
Asialoglycoprotein receptor - Autoreceptors - Biogenic amine receptor - Eicosanoid receptor (Prostaglandin receptor) - G protein-coupled receptor - Immune receptor - N-Acetylglucosamine receptor - Neuropilins - Neurotransmitter receptor - Olfactory receptor - Protease-activated receptor - Purinergic receptor - Transferrin receptor

ja:嗅覚受容体

Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .