Group IIA phospholipase A(2) is coexpressed with SNAP-25 in mature taste receptor cells of rat circumvallate papillae.

The taste buds are composed of heterogeneous cell populations with diverse properties and at different stages of maturity. It is important to define the relationships between cell properties and cell maturity to understand the molecular events involved in intracellular taste signaling. In the present study, in situ hybridization analysis indicated that group IIA phospholipase A(2) (PLA(2)-IIA) is expressed in a subset of taste bud cells. Immunohistochemical studies showed that PLA(2)-IIA was expressed in a subset of cells expressing phospholipase Cbeta2, a molecule essential for taste signaling in taste receptor cells, and also that some PLA(2)-IIA-positive cells expressed gustducin (Ggust), a bitter-taste-signaling molecule. Although PLA(2)-IIA and Ggust were expressed at similar frequencies in taste buds, bromodeoxyuridine (BrdU) chase experiments indicated that the expression of Ggust began 2 days after BrdU injection, whereas the expression of PLA(2)-IIA commenced after 4 days. In addition, PLA(2)-IIA was coexpressed with SNAP-25, a synaptosomal-associated protein. These results indicated that PLA(2)-IIA is expressed in mature taste receptor cells that possess exocytotic machinery.