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Information about Olfactory Receptors

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 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.[2][3] 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.[4][5]

In 2006 it was shown that another class of odorant receptors exist for volatile amines.[6] 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.[7]

See also

References

1. ^ Gilad Y, Lancet D (2003). "Population differences in the human functional olfactory repertoire.". Mol. Bio. Evol. 20 (3): 307-14. DOI:10.1093/molbev/msg013. PMID 12644552. 
2. ^ Malnic B, Hirono J, Sato T, Buck LB. Combinatorial receptor codes for odors. Cell; Mar 5 (1999). PMID 10089886
3. ^ Araneda RC, Peterlin Z, Zhang X, Chesler A, Firestein S. A pharmacological profile of the aldehyde receptor repertoire in rat olfactory epithelium. Journal of Physiology; Mar 16 (2004). PMID 14724183
4. ^ Buck L., Axel R. A novel multigene family may encode odorant receptors: a molecular basis for odor recognition., Cell; (1991). PMID 1840504
5. ^ Press Release: The 2004 Nobel Prize in Physiology or Medicine. Retrieved on 2007-06-06.
6. ^ Liberles SD, Buck LB. A second class of chemosensory receptors in the olfactory epithelium. Nature; Aug 10 (2006). PMID 16878137
7. ^ Khafizov K, Anselmi C, Menini A, Carloni P. Ligand specificity of odorant receptors. J Mol Model; Mar (2007). PMID 17120078

External links

 •  • [ 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
 •  • [ e]
Transmembrane receptor: G protein-coupled receptors
Class A: Rhodopsin likeAcetylcholine receptor (Muscarinic acetylcholine) - Adrenergic - Angiotensin - Bombesin (BRS3, GRPR, NMBR) - Bradykinin - Cannabinoid - Chemokine - Cholecystokinin - C5a - Dopamine - Eicosanoid (Prostaglandin) - Endothelin - Free fatty acid - FSH-receptor - Galanin - Ghrelin - GPER - Gonadotropin-releasing hormone - Histamine (H1, H2, H3, H4) - LHRH - Luteinizing hormone/choriogonadotropin - Lysophospholipid - Melanocortin (MC1R, MC2R) - Melatonin - Neuromedin (B, U) - Neuropeptide Y - Neurotensin - Opioid (Delta, Kappa, Mu, Nociceptin, but not Sigma) - Olfactory (TAAR) - Orexin - Oxytocin - PAF - Prokineticin - Protease-activated - Purinergics (Adenosine, A1, P2Y, P2Y12) - Somatostatin - Serotonin, all but 5-HT3 (5-HT2A) - SREB - Tachykinin (TACR1) - Thyrotropin - Thyrotropin-releasing hormone - Urotensin-II - Vasopressin (1A, 1B, 2)
Class B: Secretin likeCalcitonin - Corticotropin-releasing hormone - EMR - Glucagon (GR, GIPR, GLP1R, GLP2R) - Growth hormone releasing hormone - Parathyroid hormone - Secretin - Vasoactive intestinal peptide
Class C: Metabotropic glutamate / pheromoneGABA receptor (GABA B) - Glutamate receptor (Metabotropic glutamate) - Taste receptors (TAS2R16, TAS2R38)
Frizzled / SmoothenedFrizzled - Smoothened
 •  • [ 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
G protein-coupled receptors (GPCRs), also known as seven transmembrane receptors, 7TM receptors, heptahelical receptors, and G protein linked receptors (GPLR
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In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes, activated by second messengers resulting in
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Location olfactory epithelium in the nose
Function Detect traces of chemicals in inhaled air (sense of smell)
Neurotransmitter Glutamate
Morphology Bipolar sensory receptor
Presynaptic connections None
Postsynaptic connections
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Vertebrata
Cuvier, 1812

Classes and Clades

See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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Insecta
Linnaeus, 1758

Orders
Subclass Apterygota
* Archaeognatha (bristletails)
* Thysanura (silverfish)
Subclass Pterygota
* Infraclass Paleoptera (Probably paraphyletic)

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Antennae (singular antenna) are paired appendages connected to the front-most segments of arthropods. In crustaceans, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules.
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sperm is derived from the word spermos (meaning "seed") and refers to the male reproductive cells. Sperm cells are the smaller gametes involved in fertilization.
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Chemotaxis, a kind of taxis, is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.
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ovum (plural ova) is a haploid female reproductive cell or gamete. The word is derived from Latin, meaning egg or egg cell. Both animals and embryophytes have ova. The term ovule
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odor or odour (see spelling differences) is a volatilized chemical compound, generally at a very low concentration, which humans and other animals perceive by the sense of olfaction. Odors are also called smells, which can refer to both pleasant and unpleasant odors.
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G proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. Their nomenclature originates from their ability to function as "molecular switches", alternating between an inactive guanosine diphosphate (GDP) and
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Adenylate cyclase (EC 4.6.1.1 , also known as adenylyl cyclase or AC) is a lyase enzyme.

Types

There are nine known adenylate cyclases in mammals:
  • ADCY1
  • ADCY2
  • ADCY3
  • ADCY4
  • ADCY5

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Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism.
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Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3'-5'-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP).
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Ion channels are pore-forming proteins that help to establish and control the small voltage gradient across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient.
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Calcium (IPA: /ˈkalsiəm/) is the chemical element in the periodic table that has the symbol Ca and atomic number 20. It has an atomic mass of 40.078.
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Sodium (IPA: /ˈsəʊdiəm/) is a chemical element which has the symbol Na (Latin: natrium), atomic number 11, atomic mass 22.9898 g/mol, common oxidation number +1.
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ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion
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An action potential is a "spike" of electrical discharge that travels along the membrane of a cell. Action potentials are an essential feature of animal life, rapidly carrying information within and between tissues. They also occur in some plants.
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In animals, the brain or encephalon (Greek for "in the skull"), is the control center of the central nervous system, responsible for behavior. The brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing,
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In biology the genome of an organism is its whole hereditary information and is encoded in the DNA (or, for some viruses, RNA). This includes both the genes and the non-coding sequences of the DNA.
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The introduction to this article provides insufficient context for those unfamiliar with the subject matter.
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For a non-technical introduction to the topic, see .
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions.
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Pseudogenes are defunct relatives of known genes that have lost their protein-coding ability or are otherwise no longer expressed in the cell.[1] Although they may have some gene-like features (such as Promoters, CpG islands, and splice sites), they are nonetheless
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immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy
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20th century - 21st century - 22nd century
1970s  1980s  1990s  - 2000s -  2010s  2020s  2030s
2001 2002 2003 - 2004 - 2005 2006 2007

2004 by topic:
News by month
Jan - Feb - Mar - Apr - May - Jun
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Linda B. Buck, Ph.D., (born January 29, 1947) is an American biologist best known for her work on the olfactory system. She and Richard Axel won the 2004 Nobel Prize in Physiology or Medicine for their work on olfactory receptors.
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Richard Axel, M.D. (born July 2, 1946, New York City) is an American scientist whose work on the olfactory system won him and Linda B. Buck, a former post-doctoral scientist in his research group, the Nobel Prize in Physiology or Medicine in 2004.
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';
George Richards Minot, ';
William Parry Murphy, "for their discoveries concerning liver therapy in cases of anaemia"[31]
1935 Hans Spemann, '' German Empire "for his discovery of the organizer effect in embryonic development"[32]
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Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. Structurally amines resemble ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups.
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