A Novel Role for Odorant Binding Proteins in Deactivation of Drosophila Olfactory Neurons
In insects, odorant binding proteins are a large and diverse group of low molecular weight proteins secreted into the fluid bathing olfactory and gustatory dendrites. The best-characterized OBP, known as LUSH, is required in Drosophila melanogaster for the detection of physiological levels of the male-specific pheromone cVA. While LUSH acts as a sensitizing factor for pheromone detection, the role of other OBPs encoded in the Drosophila genome is largely unknown. In an effort to characterize members of this family, I used CRISPR-Cas9 to generate and characterize a deletion of two genes encoding the homologous OBPs OS-E and OS-F. These OBPs are nearly 70% identical and their expression is restricted to a small set of antennal chemosensory sensilla. Electrophysiological analysis of the olfactory neurons within these sensilla revealed no major difference in odorant sensitivity or specificity in the mutants but did reveal a striking deactivation defect to a subset of odorants. Surprisingly, other odorants detected by the same receptor are differentially affected by the absence of OS-E and OS-F, revealing an odorant-specific role for these OBPs in deactivation kinetics. Activation kinetics remain normal for the affected odorants in mutants. Genomic rescue experiments revealed that OS-E and OS-F are also functionally redundant, as either OBP is sufficient to revert the mutant phenotype. My findings reveal a new role for OBPs in deactivation of olfactory neurons and expand our understanding of the range of OBP functions.
Carrier Proteins, Drosophila Proteins, Loss of Function Mutation, Phenotype
University of Texas Southwestern Medical Center
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