Bitter taste is one of the basic taste modalities including the bitterness, sweetness, umaminess, saltiness, acidness, and fatness (Besnard et al., 2016; Roper and Chaudhari, 2017). Evolutionarily, bitter taste is pivotal to the survival by protecting organisms from the consumption of potentially poisonous substances, which often taste bitter. Perception of the bitter taste is mainly mediated by the taste receptors type 2 (Tas2Rs) family of G-protein coupled receptors (GPCRs) on the apical membrane of the taste receptor cells located in the taste buds (Jaggupilli et al., 2016; Roper and Chaudhari, 2017). Intriguingly, Tas2Rs are also expressed in the extra-oral tissues, e.g., the gastrointestinal tract and respiratory system, etc., indicating that they are also intricately involved in the other crucial biological processes (Clark et al., 2012; Shaik et al., 2016).