Ryanodine Receptors Selectively Interact with L Type Calcium Channels in Mouse Taste Cells

Abstract

IntroductionWe reported that ryanodine receptors are expressed in two different types of mammalian peripheral taste receptor cells: Type II and Type III cells. Type II cells lack voltage-gated calcium channels (VGCCs) and chemical synapses. In these cells, ryanodine receptors contribute to the taste-evoked calcium signals that are initiated by opening inositol trisphosphate receptors located on internal calcium stores. In Type III cells that do have VGCCs and chemical synapses, ryanodine receptors contribute to the depolarization-dependent calcium influx.Methodology/Principal FindingsThe goal of this study was to establish if there was selectivity in the type of VGCC that is associated with the ryanodine receptor in the Type III taste cells or if the ryanodine receptor opens irrespective of the calcium channels involved. We also wished to determine if the ryanodine receptors and VGCCs require a physical linkage to interact or are simply functionally associated with each other. Using calcium imaging and pharmacological inhibitors, we found that ryanodine receptors are selectively associated with L type VGCCs but likely not through a physical linkage.Conclusions/SignificanceTaste cells are able to undergo calcium induced calcium release through ryanodine receptors to increase the initial calcium influx signal and provide a larger calcium response than would otherwise occur when L type channels are activated in Type III taste cells.

AP1 transcription factors are required to maintain the peripheral taste system

“…Isolated taste receptor cells were collected from adult mice (at ages 2, 6 or 12 months) following previously described procedures. 58, 59, 60, 61, 62, 63, 64, 65 Taste buds were harvested from CV and Fol papillae of C57BL/6 mice ( n =3 mice per sample for older mice, 4 mice per sample for 2 mo mice). Mice were killed with CO 2 and cervical dislocation.…”

Differential Effects of Diet and Weight on Taste Responses in Diet‐Induced Obese Mice

“…TRCs were harvested from taste papillae of adult mice as previously described . Briefly, tongues were removed and injected beneath the lingual epithelium with 0.2 mL of enzyme solution (3 mg of Dispase II, 0.7 mg of collagenase B [Roche Diagnostics, Indianapolis, Indiana], and 1 mg of trypsin inhibitor in 1 mL of Tyrode’s).…”

“…TRCs were harvested from taste papillae of adult mice as previously described (12,(20)(21)(22)(23)(24)(25). Briefly, tongues were removed and injected beneath the lingual epithelium with 0.…”

Calcium signaling in taste cells

“…Further analysis found that in the TRCs with both VGCCs and the PLC signaling pathway, the ryanodine receptors were exclusively contributing to the calcium influx signal generated by VGCCs and no longer contributed to the calcium release signal generated by activating the PLC signaling pathway [30]. Data indicated that the ryanodine receptors were associating with L-type VGCCs in these cells and that there is a functional, but not physical interaction, between these proteins [31]. The mechanism underlying this selective interaction has not been identified in taste cells but this specificity may be due to the localization of these different signaling components on the endoplasmic reticulum.…”

“…The distribution of VGCCs in taste cells has not been well-characterized but studies have established that multiple VGCCs are expressed in taste cells, including L-type calcium channels. It is clear that L-type calcium channels are not the only VGCCs in taste cells [20, 31, 48, 49] and the Roberts et al (2009) study indicates that there is some segregation in the expression of VGCC isoforms within taste cells. If L-type calcium channel inactivation does significantly affect the amplitude of the response peak, then NCXs may actually have an important role in controlling the initial peak response magnitude that was not measured in the earlier study [46].…”