Evaluation of a high-throughput deorphanization strategy to identify cytochrome p450s important for odor degradation inDrosophila

Abstract

Members of the cytochrome p450 (CYP) enzyme family are abundantly expressed in insect olfactory tissues, where they are thought to act as Odorant Degrading Enzymes (ODEs). However, their contribution to olfactory signaling in vivo is poorly understood. This is due in part to the challenge of identifying which of the dozens of antennal-expressed CYPs might inactivate a given odorant. Here, we tested a high-throughput deorphanization strategy in Drosophila to identify CYPs that are transcriptionally induced by exposure to a plant volatile. We discovered three CYPs selectively upregulated by the odorant using transcriptional profiling. Although these CYPs are shown to be broadly expressed in the antenna in non-neuronal cells, electrophysiological recordings from CYP mutants did not reveal any changes in olfactory neuron responses to the odorant. Neurons were desensitized by pre-exposing flies to the odorant, but this effect was similar in CYP mutants. Together, our data suggest that this transcriptomic approach may not be useful for identifying CYPs that contribute to olfactory signaling. We go on to show that some CYPs have highly restricted expression patterns in the antenna, and suggest that such CYPs may be useful candidates for further studies on olfactory CYP function.

Functional Interaction Between Drosophila Olfactory Sensory Neurons and Their Support Cells

“…For example, they are thought to play a passive role in lymph maintenance by releasing various ''helper'' proteins into the sensillum lymph to aid in stimulus recognition (Rihani et al, 2021). Among these are the odor-degrading enzymes (ODEs), a poorly-defined set of catabolic enzymes which play a role in odor degradation and clearance (Younus et al, 2014;Baldwin et al, 2021), and chemosensory proteins (CSPs) which act as extracellular holdase chaperones in their ability to bind and transport chemicals in aqueous environments (Pelosi et al, 2018;Zhu et al, 2019). In insect olfactory tissues, the best-studied accessory proteins are the odor-binding proteins (OBPs), which have long been posited to influence odor responsiveness by allowing less soluble odors to traverse the lymph and interact with olfactory receptors.…”

Functional interaction between Drosophila olfactory sensory neurons and their support cells

“…They are thought to play a passive role in lymph maintenance by releasing various 'helper' proteins into the sensillum lymph to aid in stimulus recognition (Rihani et al, 2021). Among these are the odor-degrading enzymes (ODEs), a poorly-defined set of catabolic enzymes which play a role in odor degradation and clearance (Younus et al, 2014;Baldwin et al, 2021), and chemosensory proteins (CSPs) which act as extracellular holdase chaperones in their ability to bind and transport chemicals in aqueous environments (Pelosi et al, 2018;Zhu et al, 2019). In insect olfactory tissues, the best studied accessory proteins are the odor-binding proteins (OBPs), which have long been posited to influence odor responsiveness by allowing less soluble odors to traverse the lymph and interact with olfactory receptors.…”