Localization of TRPM5 and PKD2L1 in taste receptor cells. A-C and G-I, TRPM5 immunoreactivity is concentrated in taste receptor cell processes below the taste pore. Double label IHC for the tight junction protein ZO-1 (A, G) and TRPM5 (B, H) reveals that TRPM5 immunoreactivity is localized to basolateral membranes beneath tight junctions in the merged images (C, I). D-F and K-M, PKD2L1 immunoreactivity is concentrated in taste receptor cell processes at the taste pore. Double label IHC for the tight junction protein ZO-1 (D, K) and PKD2L1 (E, L) reveals that PKD2L1 immunoreactivity is localized, in part, to apical membranes above tight junctions in the merged images (F, M). Images are from CV papilla and are longitudinal sections. Images in A-F illustrate low magnification of multiple taste buds; images in G-I and K-M illustrate high magnification of single taste buds with the taste pore at the top. J, Zoom of taste pore region. TRPM5 immunoreactivity (red) is prevalent in basolateral membranes (Bl) beneath tight junctions, labelled with ZO-1 (green), but absent from apical membranes (Ap) above tight junctions. N, Zoom of taste pore region. PKD2L1 immunoreactivity (red) is enriched in Ap membranes above tight junctions. Arrows denote taste pore region and apical side of taste bud. White dashed line illustrates boundary between apical and basolateral membrane domains. Scale bar is 20 μm in C and represents scale for A-F, 10 μm in I and represents scale for G-I and K-M, and 5 μm in J and represents scale for J and N.