| Title: | In situ tip-recordings found no evidence for an Orco-based ionotropic mechanism of pheromone-transduction in Manduca sexta |
| Author(s): | Nolte A; Funk NW; Mukunda L; Gawalek P; Werckenthin A; Hansson BS; Wicher D; Stengl M; |
| Address: | "Department of Animal Physiology, University of Kassel, Kassel, Germany" |
| DOI: | 10.1371/journal.pone.0062648 |
| ISSN/ISBN: | 1932-6203 (Electronic) 1932-6203 (Linking) |
| Abstract: | "The mechanisms of insect odor transduction are still controversial. Insect odorant receptors (ORs) are 7TM receptors with inverted membrane topology. They colocalize with a conserved coreceptor (Orco) with chaperone and ion channel function. Some studies suggest that insects employ exclusively ionotropic odor transduction via OR-Orco heteromers. Other studies provide evidence for different metabotropic odor transduction cascades, which employ second messenger-gated ion channel families for odor transduction. The hawkmoth Manduca sexta is an established model organism for studies of insect olfaction, also due to the availability of the hawkmoth-specific pheromone blend with its main component bombykal. Previous patch-clamp studies on primary cell cultures of M. sexta olfactory receptor neurons provided evidence for a pheromone-dependent activation of a phospholipase Cbeta. Pheromone application elicited a sequence of one rapid, apparently IP3-dependent, transient and two slower Ca(2+)-dependent inward currents. It remains unknown whether additionally an ionotropic pheromone-transduction mechanism is employed. If indeed an OR-Orco ion channel complex underlies an ionotropic mechanism, then Orco agonist-dependent opening of the OR-Orco channel pore should add up to pheromone-dependent opening of the pore. Here, in tip-recordings from intact pheromone-sensitive sensilla, perfusion with the Orco agonist VUAA1 did not increase pheromone-responses within the first 1000 ms. However, VUAA1 increased spontaneous activity of olfactory receptor neurons Zeitgebertime- and dose-dependently. We conclude that we find no evidence for an Orco-dependent ionotropic pheromone transduction cascade in M. sexta. Instead, in M. sexta Orco appears to be a slower, second messenger-dependent pacemaker channel which affects kinetics and threshold of pheromone-detection via changes of intracellular Ca(2+) baseline concentrations" |
| Keywords: | "*Action Potentials Animals Calcium Signaling HEK293 Cells Humans Insect Proteins/*metabolism Ion Channels/*metabolism Manduca/cytology/*physiology Olfactory Receptor Neurons/physiology Pheromones/pharmacology/*physiology Receptors, Odorant/metabolism Smel;" |
| Notes: | "MedlineNolte, Andreas Funk, Nico W Mukunda, Latha Gawalek, Petra Werckenthin, Achim Hansson, Bill S Wicher, Dieter Stengl, Monika eng Research Support, Non-U.S. Gov't 2013/05/15 PLoS One. 2013 May 3; 8(5):e62648. doi: 10.1371/journal.pone.0062648. Print 2013" |
