Functional and nonfunctional forms of CquiOR91, an odorant selectivity subunit of Culex quinquefasciatus

David T. Hughes, Julien Pelletier, Suhaila Rahman, Sisi Chen, Walter S. Leal, Charles W. Luetje

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

In Culex quinquefasciatus, CquiOR91 is the ortholog of 2 larvae-specific odorant receptors (ORs) from Anopheles gambiae (Agam\Or40, previously shown to respond to several odorant ligands including the broad-spectrum repellent N, N-diethyl-3-methylbenzamide, DEET) and Aedes aegypti (Aaeg\Or40). When we cloned full-length CquiOR91 from a Culex quinquefasciatus larval head RNA sample, we found 2 alleles of this OR, differing at 9 residues. Functional analysis using the Xenopus oocyte expression system and 2-electrode voltage clamp electrophysiology revealed one allele (CquiOR91.1) to be nonfunctional, whereas the other allele (CquiOR91.2) was functional. Receptors formed by CquiOR91.2 and Cqui\Orco responded to (-)-fenchone, (+)-fenchone, and DEET, similar to what has been reported for Agam\Or40. We also identified 5 novel odorant ligands for the CquiOR91.2 + Cqui\Orco receptor: 2-isobutylthiazole, veratrole, eucalyptol, d-camphor, and safranal, with safranal being the most potent. To explore possible reasons for the lack of function for CquiOR91.1, we generated a series of mutant CquiOR91.2 subunits, in which the residue at each of the 9 polymorphic residue positions was changed from what occurs in CquiOR91.2 to what occurs in CquiOR91.1. Eight of the 9 mutant versions of CquiOR91.2 formed functional receptors, responding to (-)-fenchone. Only the CquiOR91.2 Y183C mutant was nonfunctional. The reverse mutation (C183Y) conferred function on CquiOR91.1, which became responsive to (-)-fenchone and safranal. These results indicate that the "defect" in CquiOR91.1 that prevents function is the cysteine at position 183.

Original languageEnglish (US)
Article numberbjx011
Pages (from-to)333-341
Number of pages9
JournalChemical senses
Volume42
Issue number4
DOIs
StatePublished - May 1 2017

Keywords

  • Electrophysiology
  • Insect
  • Olfaction
  • Polymorphism
  • Receptor
  • Xenopus oocytes

ASJC Scopus subject areas

  • Physiology
  • Sensory Systems
  • Physiology (medical)
  • Behavioral Neuroscience

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    Hughes, D. T., Pelletier, J., Rahman, S., Chen, S., Leal, W. S., & Luetje, C. W. (2017). Functional and nonfunctional forms of CquiOR91, an odorant selectivity subunit of Culex quinquefasciatus. Chemical senses, 42(4), 333-341. [bjx011]. https://doi.org/10.1093/chemse/bjx011