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Figure 2.
Sites in the body where cells express the canonical taste receptor cascade
Taste buds comprise three types of elongated cells, one of which (type II/receptor cells, identified by green fluorescence) expresses the taste receptor (TR)-mediated transduction cascade culminating in activation of TrpM5. In the nasal cavity (top right), solitary chemosensory cells express the “taste” transduction cascade and synapse onto nerve fibers (red) arising from the trigeminal nerve [9]. In the trachea (upper left), the “taste”-like cells are brush cells, which release acetylcholine upon stimulation [40]. Some also make contacts with sensory nerve fibers (red) from the vagus nerve. In the stomach (center lower right), a variety of enteroendocrine cells express elements of the taste transduction cascade [18,20,22] and release into the gut a variety of peptide hormones. Numerous brush cells in the gall bladder and bile ducts express the canonical taste transduction cascade [15,20]; their function is unknown. In the upper part of the small intestine (e.g., duodenum, lower right), a variety of enteroendocrine cells express taste receptors and the associated downstream transduction cascade [16,17]. Some of these extend into the intestinal lumen while others do not. When activated, these cells release a variety of gut peptides as discussed in the main text. Micrographs courtesy of Dr. Marco Tizzano. |
