Odorant Receptor Inhibition Is Fundamental to Odor Encoding

Patrick Pfister, Benjamin C. Smith, Barry J. Evans, Jessica H. Brann, Casey Trimmer, Mushhood Sheikh, Randy Arroyave, Gautam Reddy, Hyo Young Jeong, Daniel A. Raps, Zita Peterlin, Massimo Vergassola, Matthew E. Rogers

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Most natural odors are complex mixtures of volatile components, competing to bind odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) of the nose. To date, surprisingly little is known about how OR antagonism shapes neuronal representations in the detection layer of the olfactory system. Here, we investigated its prevalence, the degree to which it disrupts OR ensemble activity, and its conservation across phylogenetically related ORs. Calcium imaging microscopy of dissociated OSNs revealed significant inhibition, often complete attenuation, of responses to indole—a commonly occurring volatile associated with both floral and fecal odors—by a set of 36 tested odorants. To confirm an OR mechanism for the observed inhibition, we performed single-cell transcriptomics on OSNs exhibiting specific response profiles to a diagnostic panel of odorants and identified three paralogous receptors—Olfr740, Olfr741, and Olfr743—which, when tested in vitro, recapitulated OSN responses. We screened ten ORs from the Olfr740 gene family with ∼800 perfumery-related odorants spanning a range of chemical scaffolds and functional groups. Over half of these compounds (430) antagonized at least one of the ten ORs. OR activity fitted a mathematical model of competitive receptor binding and suggests normalization of OSN ensemble responses to odorant mixtures is the rule rather than the exception. In summary, we observed OR antagonism occurred frequently and in a combinatorial manner. Thus, extensive receptor-mediated computation of mixture information appears to occur in the olfactory epithelium prior to transmission of odor information to the olfactory bulb. Odors activate and inhibit olfactory sensory neurons in the olfactory epithelium, modulating their representation at the point of detection. Pfister et al. show that neuronal inhibition is odorant-receptor mediated, widespread, combinatorial, and may represent a convergent evolutionary solution to the complexity of natural odors.

Original languageEnglish (US)
Pages (from-to)2574-2587.e6
JournalCurrent Biology
Volume30
Issue number13
DOIs
StatePublished - Jul 6 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Neuroscience
  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences

Keywords

  • antagonism
  • G protein-coupled
  • odor mixtures
  • odorant
  • olfaction
  • receptor
  • sensory neurons

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