STOM inhibits ASIC3 via a direct interaction. (A) Topological cartoon of STOM interaction with ASIC3. Shown are several of STOM's topological features that influence its localization and interaction with membrane proteins including: palmitoylation sites, a hydrophobic hairpin, an SPFH domain, and a cholesterol recognition motif (CARC). (B) Left: Representative pH 5.5–evoked ASIC3 currents alone (black) and cotransfected with STOM (red). Right: Plot shows every measurement made for the two conditions plotted as the current density (peak current amplitude/cell capacitance) superimposed onto a boxplot that summarizes the data. Average current densities of the control and +STOM conditions were 364.0 ± 32.6 pA/pF (n = 45) and 2.0 ± 0.4 pA/pF (n = 27), respectively. (C) Identical experiments as in B performed for ASIC1a. Average current densities of ASIC1a in the absence (black) and presence (red) of STOM were 122.5 ± 22.9 pA/pF (n = 8) and 200.3 ± 33.7 pA/pF (n = 7), respectively. (D) Cartoon showing FRET photobleaching assay. Bottom panel shows a representative cell where the YFP was bleached, which led to a corresponding increase in CER intensity. The displayed images are 36 x 36 μm. (E) FRET efficiency measured between ASIC3-CER and STOM-YFP and ASIC1a-CER and STOM-YFP. FRET efficiencies for ASIC3-CER and ASIC1a-CER were 12.5 ± 1.2% (n = 11) and 1.2 ± 0.6% (n = 8), respectively. All data are given as mean ± SEM.