SPLTRAK Abstract Submission
Both Form and Function of Type I Taste Cells Suggest a Role in Taste Signal Transmission and/or Modulation
Courtney E Wilson1,2, Eric D Larson1, Catherine B Anderson1, Aurelie Vandenbeuch1, Ruibiao Yang2, Thomas E Finger2, Sue C Kinnamon1
1Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, United States
2Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, United States

Type I taste cells are often described as the glial-like support cells of mammalian taste buds. Type I cells wrap around neighboring cells, and likely remove neurotransmitter released by receptor cells. To test whether Type I taste cells might play a role in modulation or transmission of taste information, we examined aspects of Type I morphology and physiology. Using serial EM images of mouse circumvallate taste buds, we observed regions of apparent specialized contact between some Type I cells and nerve fibers. These nerve fibers “nest” in invaginations of these Type I cells, being separated from the nucleus only by the plasma membrane and a thin rim of cytosol. At these contact points, the area between the Type I cell nuclear envelope and the section of outer membrane that abuts the nerve fiber is more electron dense than the surrounding cytoplasm, suggestive of a point of specialized contact. Morphologically, Type I cells, which separate Type II and Type III cells, are well poised to participate in cell-cell communication within the bud. If this is the case, Type I cells should respond to neurotransmitters released by taste receptor cells including ATP which is released by Type II cells. To test whether Type I cells respond to ATP, we used calcium imaging of isolated Type I cells as marked by tdTomato fluorescence driven by a Gad65-Cre construct. Type I cells were identified as fluorescently marked cells that did not show depolarization-evoked calcium influx. These Type I cells did show calcium increases in response to extracellularly applied ATP. These data indicate a more expansive role for Type I cells in the transduction and integration of signals in the mammalian taste bud than has been considered previously.