Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

55-POS Board 14 APICAL LOCALIZATION OF THE SOUR RECEPTOR OTOP1 IN TASTE CELLS Joshua P Kaplan 1,2 ; Anne Tran 1,2 ; Paul Cohen 3 ; Emily R Liman 1,2 ; 1 University of Southern California , Section of Neurobiology, Department of Biological Sciences, Los Angeles, CA, USA 2 University of Southern California, Program in Neuroscience , Los Angeles, CA, USA 3 The Rockefeller University, Laboratory of Molecular Metabolism, New York, NY, USA Sour taste is evoked by acid stimuli that signal through a proton-selective ion channel Otopetrin- 1 (OTOP1). Within taste buds, OTOP1 expression is mostly restricted to Type III taste receptor cells that mediate sour taste. The subcellular localization of OTOP1 within those cells is not known. In particular, it is not known if OTOP1 is on the apical surface, like the sweet and bitter receptors, where it would be accessible to compounds that could modulate its activity or if it is on the basolateral surface, like the taste transduction channel TRPM5, hidden from such compounds. Previous work from our lab using a commercially available antibody did not detect membrane localization of OTOP1 in taste cells or when expressed in HEK-293 cells, in contradiction of electrophysiological evidence for OTOP1 expression on the cell membrane in these cell types. This suggests that the antibody detected only protein in the secretory pathway, where the epitope was exposed. To resolve this discrepancy and determine the subcellular localization of the correctly folded protein, we took advantage of the CRISPR-Cas9 system to engineer a mouse line in which a 2x-HA epitope tag was introduced at the N terminus of OTOP1. Confocal microscopy showed strong HA-immunoreactivity that was highly enriched at the apical surface of taste buds in microvilli. Interestingly, HA-OTOP1 did not appear to be restricted to the microvilli of taste cells but was also detected in a sub-apical zone. Localization of OTOP1 in the apical region of taste cells is consistent with its function as a sour receptor and suggests that it may be accessible to taste-modifying compounds.

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