The taste bud and the predicted structure of the taste receptor for fat, CD36, expressed on the apical surface of taste cells. (A) Schematic structure of a taste bud, which contains 50–100 taste cells. One such taste cell is highlighted, showing CD36 expression on its apical surface. Following interaction of CD36 with FAs derived from hydrolysis of triglycerides by lingual lipase, a signal is transduced to nerve fibers, which leads to taste perception and release of bile acid, preparing the digestive system for fat absorption. (B) The predicted structure of membrane CD36, which is proposed to function as a taste receptor recognizing long-chain FAs (10). CD36 is heavily glycosylated (orange circles) and also N-myristoylated and palmitoylated at multiple sites adjacent to both the N and C termini (not shown). CD36 binds FAs with high affinity, presumably in its extracellular domain, and facilitates their transfer into the cell, a process that may involve interaction with other proteins. In taste bud cells, interaction of the FA with CD36 may be sufficient to initiate signaling events without internalization. Alternatively, internalization and generation of intracellular FA derivatives may be required for signal transduction.