TAS2R4 is a G protein-coupled bitter taste receptor that functions as a gustducin-coupled chemosensor for bitter compounds including denatonium and N(6)-propyl-2-thiouracil 1. The receptor signals through phospholipase C β2 (PLCB2) and downstream calcium mobilization to activate the cation channel TRPM5 2. Beyond taste perception in the oral cavity, TAS2R4 exhibits diverse extraoral functions. In the gastrointestinal tract, TAS2R4 responds to bitter peptides formed during gastric digestion, stimulating proton secretion and serotonin release in parietal cells to promote satiety 3. TAS2R4 activation ameliorates diabetic nephropathy by suppressing podocyte injury through inhibition of NF-κB-mediated NLRP3 inflammasome activation 2. In scalp hair follicles, TAS2R4 stimulation inhibits hair growth via enhanced TGF-β2 production and premature catagen entry 4. TAS2R4 additionally modulates intestinal GDF15 and GLP-1 expression, satiety-promoting hormones relevant to obesity management 5. In airway epithelial cells, TAS2R4 activation increases intracellular calcium and stimulates ciliary beat frequency, contributing to anti-inflammatory effects in allergic airway disease 6. Genetic polymorphisms in TAS2R4 influence bitter taste sensitivity and may predict therapeutic responsiveness to bitter compounds 7. These findings establish TAS2R4 as a promising therapeutic target for metabolic, renal, dermatological, and respiratory disorders.