File:Olfaction signal transduction.JPG: Difference between revisions

Olfaction signal transduction

"Signal transduction in the OSN. (A) Representation of the receptors, enzymes, and ion channels—present in the olfactory cilia—that transduce activity of the odorant receptor (OR) into changes in membrane potential and gene expression. Binding of an odorant to its cognate OR results in the activation of heterotrimeric G protein (Gαolf plus Gβγ). Activated Gαolf in turn activates type III adenylyl cyclase (AC3), leading to the production of cyclic AMP (cAMP) from ATP. cAMP gates or opens the cyclic nucleotide-gated (CNG) ion channel, leading to the influx of Na+ and Ca2+, depolarizing the cell. This initial depolarization is amplified through the activation of a Ca2+-dependent Cl− channel. In addition, cAMP activates protein kinase A (PKA), which can regulate other intracellular events, including transcription of cAMP-regulated genes. (B) Events in the nucleus of OSNs important for establishing and maintaining sensory neuron identity. Selection of a particular OR gene by the cell is thought to occur via interaction of a cis-regulatory locus control region with the proximal promoter of a single OR gene within a cluster of OR genes. This choice is stabilized—and the expression from all other OR genes in the genome is silenced—by an OR-dependent feedback loop, which ensures the expression of a single OR per sensory neuron. The mechanism underlying OR-mediated, OR gene silencing is at present not understood. OR-mediated activity also leads to transcriptional regulation of cAMP response element binding protein (CREB)–dependent gene expression via CREB's phosphorylation by PKA".

Published November 1, 2010 // JCB vol. 191 no. 3 443-452 The Rockefeller University Press, doi: 10.1083/jcb.201008163 © 2010 DeMaria and Ngai

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