KEGG   PATHWAY: ko04740Help
Entry
ko04740                     Pathway                                

Name
Olfactory transduction
Description
Within the compact cilia of the olfactory receptor neurons (ORNs) a cascade of enzymatic activity transduces the binding of an odorant molecule to a receptor into an electrical signal that can be transmitted to the brain. Odorant molecules bind to a receptor protein (R) coupled to an olfactory specific Gs-protein (G) and activate a type III adenylyl cyclase (AC), increasing intracellular cAMP levels. cAMP targets an olfactory-specific cyclic-nucleotide gated ion channel (CNG), allowing cations, particularly Na and Ca, to flow down their electrochemical gradients into the cell, depolarizing the ORN. Furthermore, the Ca entering the cell is able to activate a Ca-activated Cl channel, which would allow Cl to flow out of the cell, thus further increasing the depolarization. Elevated intracellular Ca causes adaptation by at least two different molecular steps: inhibition of the activity of adenylyl cyclase via CAMKII-dependent phosphorylation and down-regulation of the affinity of the CNG channel to cAMP.Longer exposure to odorants can stimulate particulate guanylyl cyclase in cilia to produce cGMP and activate PKG, leading to a further increase in amount and duration of intracellular cAMP levels, which may serve to convert inactive forms of protein kinase A (PKA2) to active forms (PKA*). As part of a feedback loop, PKA can inhibit the activation of particulate guanylyl cyclase.
Class
Organismal Systems; Sensory system
BRITE hierarchy
Pathway map
Olfactory transduction
ko04740

All organismsOrtholog table
Other DBs
BSID: 
GO: 
Orthology
K04257  
olfactory receptor
K04633  
guanine nucleotide-binding protein G(olf) subunit alpha
K04345  
protein kinase A [EC:2.7.11.11]
K08327  
phosducin
K07376  
protein kinase, cGMP-dependent [EC:2.7.11.12]
K08043  
adenylate cyclase 3 [EC:4.6.1.1]
K04515  
calcium/calmodulin-dependent protein kinase (CaM kinase) II [EC:2.7.11.17]
K02183  
calmodulin
K08328  
guanylate cyclase activator 1
K04950  
cyclic nucleotide gated channel alpha 3
K04951  
cyclic nucleotide gated channel alpha 4
K04952  
cyclic nucleotide gated channel beta 1
K05027  
calcium-activated chloride channel regulator 1
K05028  
calcium-activated chloride channel regulator 2
K05030  
calcium-activated chloride channel regulator 4
Compound
C00076  
Calcium cation
C00575  
3',5'-Cyclic AMP
C00698  
Cl-
C00942  
3',5'-Cyclic GMP
C01330  
Sodium cation
Reference
  Authors
Firestein S.
  Title
How the olfactory system makes sense of scents.
  Journal
Nature 413:211-8 (2001)
Reference
  Authors
Ache BW, Young JM.
  Title
Olfaction: diverse species, conserved principles.
  Journal
Neuron 48:417-30 (2005)
Reference
  Authors
Nakamura T.
  Title
Cellular and molecular constituents of olfactory sensation in vertebrates.
  Journal
Comp Biochem Physiol A Mol Integr Physiol 126:17-32 (2000)
Reference
  Authors
Zufall F, Leinders-Zufall T.
  Title
The cellular and molecular basis of odor adaptation.
  Journal
Chem Senses 25:473-81 (2000)
Reference
PMID:9547228
  Authors
Moon C, Jaberi P, Otto-Bruc A, Baehr W, Palczewski K, Ronnett GV.
  Title
Calcium-sensitive particulate guanylyl cyclase as a modulator of cAMP in olfactory receptor neurons.
  Journal
J Neurosci 18:3195-205 (1998)
Reference
  Authors
Ronnett GV, Moon C.
  Title
G proteins and olfactory signal transduction.
  Journal
Annu Rev Physiol 64:189-222 (2002)
Reference
  Authors
Barry PH.
  Title
The relative contributions of cAMP and InsP3 pathways to olfactory responses in vertebrate olfactory receptor neurons and the specificity of odorants for both pathways.
  Journal
J Gen Physiol 122:247-50 (2003)
Reference
  Authors
Kohout TA, Lefkowitz RJ.
  Title
Regulation of G protein-coupled receptor kinases and arrestins during receptor desensitization.
  Journal
Mol Pharmacol 63:9-18 (2003)
Reference
PMID:9020189
  Authors
Boekhoff I, Touhara K, Danner S, Inglese J, Lohse MJ, Breer H, Lefkowitz RJ.
  Title
Phosducin, potential role in modulation of olfactory signaling.
  Journal
J Biol Chem 272:4606-12 (1997)

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