Probenecid Inhibits the Human Bitter Taste Receptor TAS2R16 and Suppresses Bitter Perception of Salicin

Bitter taste stimuli are detected by a diverse family of G protein-coupled receptors (GPCRs) expressed in gustatory cells. Each bitter taste receptor (TAS2R) responds to an array of compounds, many of which are toxic and can be found in nature. For example, human TAS2R16 (hTAS2R16) responds to β-glucosides such as salicin, and hTAS2R38 responds to thiourea-containing molecules such as glucosinolates and phenylthiocarbamide (PTC). While many substances are known to activate TAS2Rs, only one inhibitor that specifically blocks bitter receptor activation has been described. Here, we describe a new inhibitor of bitter taste receptors, p-(dipropylsulfamoyl)benzoic acid (probenecid), that acts on a subset of TAS2Rs and inhibits through a novel, allosteric mechanism of action. Probenecid is an FDA-approved inhibitor of the Multidrug Resistance Protein 1 (MRP1) transporter and is clinically used to treat gout in humans. Probenecid is also commonly used to enhance cellular signals in GPCR calcium mobilization assays. We show that probenecid specifically inhibits the cellular response mediated by the bitter taste receptor hTAS2R16 and provide molecular and pharmacological evidence for direct interaction with this GPCR using a non-competitive (allosteric) mechanism. Through a comprehensive analysis of hTAS2R16 point mutants, we define amino acid residues involved in the probenecid interaction that result in decreased sensitivity to probenecid while maintaining normal responses to salicin. Probenecid inhibits hTAS2R16, hTAS2R38, and hTAS2R43, but does not inhibit the bitter receptor hTAS2R31 or non-TAS2R GPCRs. Additionally, structurally unrelated MRP1 inhibitors, such as indomethacin, fail to inhibit hTAS2R16 function. Finally, we demonstrate that the inhibitory activity of probenecid in cellular experiments translates to inhibition of bitter taste perception of salicin in humans. This work identifies probenecid as a pharmacological tool for understanding the cell biology of bitter taste and as a lead for the development of broad specificity bitter blockers to improve nutrition and medical compliance

Use of computerized manometry for the detection of pharyngoesophageal spasm in tracheoesophageal speech

OBJECTIVE: To evaluate the utility Of Computerized manometry (CM) to identify pharyngoesophageal segment (PES) spasm during tracheoesophageal speech. STUDY DESIGN: Prospective clinical, controlled study. SUBJECTS AND METHODS: Intraluminal pressures of the PES were collected in 12 tracheoesophageal speakers without spasm and 8 tracheoesophageal speakers with PES spasm before and after localized injection of botulinum toxin to the PES. All subjects underwent voice analysis and videofluoroscopy in addition to CM before and after treatment. RESULTS: All tracheoesphageal speakers with PES spasm presented with mean intraluminal pressures greater than 16 mmHg (mean, 25.36 mmHg). In contrast, mean intraluminal pressures of subjects without spasm was 11.76 mmHg (P < 0.05). The negative predictive value associated with the use of 16 mmHg its a threshold value for spasm was 100%. CONCLUSION: CM is a clinically useful tool to aid in speech rehabilitation for tracheoesophageal speakers. Intraluminal pressures of greater than 16 mmHg was highly predictive for PES spasm. (c) 2008 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.139344945