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Morphologic characterization of rat taste receptor cells that express components of the phospholipase C signaling pathway
Author(s) -
Clapp Tod R.,
Yang Ruibiao,
Stoick Cristi L.,
Kinnamon Sue C.,
Kinnamon John C.
Publication year - 2003
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.10963
Subject(s) - taste bud , biology , umami , cell type , microbiology and biotechnology , transduction (biophysics) , taste receptor , signal transduction , phospholipase c , immunoelectron microscopy , inositol trisphosphate receptor , endoplasmic reticulum , taste , receptor , cell , biochemistry , inositol , immunology , immunohistochemistry
Abstract Rat taste buds contain three morphologically distinct cell types that are candidates for taste transduction. The physiologic roles of these cells are, however, not clear. Inositol 1,4,5‐triphosphate (IP 3 ) has been implicated as an important second messenger in bitter, sweet, and umami taste transductions. Previously, we identified the type III IP 3 receptor (IP 3 R3) as the dominant isoform in taste receptor cells. In addition, a recent study showed that phospholipase Cβ 2 (PLCβ 2 ) is essential for the transduction of bitter, sweet, and umami stimuli. IP 3 R3 and PLCβ 2 are expressed in the same subset of cells. To identify the taste cell types that express proteins involved in PLC signal transduction, we used 3,3′diaminobenzidine tetrahydrochloride immunoelectron microscopy and fluorescence microscopy to identify cells with IP 3 R3. Confocal microscopy was used to compare IP 3 R3 or PLCβ 2 immunoreactivity with that of some known cell type markers such as serotonin, protein gene‐regulated product 9.5, and neural cell adhesion molecule. Here we show that a large subset of type II cells and a small subset of type III cells display IP 3 R3 immunoreactivity within their cytoplasm. These data suggest that type II cells are the principal transducers of bitter, sweet, and umami taste transduction. However, we did not observe synapses between type II taste cells and nerve fibers. Interestingly, we observed subsurface cisternae of smooth endoplasmic reticulum at the close appositions between the plasma membrane of type II taste cells and nerve processes. We speculate that some type II cells may communicate to the nervous system via subsurface cisternae of smooth endoplasmic reticulum in lieu of conventional synapses. J. Comp. Neurol. 468:311–321, 2004. © 2003 Wiley‐Liss, Inc.