Cholesterol modulates bitter taste receptor function.
Bitter taste perception in humans is believed to act as a defense mechanism against ingestion of potential toxic substances. Bitter taste is perceived by 25 distinct bitter taste receptors (T2Rs) which belong to the family of G protein-coupled receptors (GPCRs). In the overall context of the role of membrane lipids in GPCR function, we show here that T2R4, a representative member of the bitter taste receptor family, displays cholesterol sensitivity in its signaling function. In order to gain further insight into cholesterol sensitivity of T2R4, we mutated two residues Tyr114(3.59) and Lys117(3.62) present in the cholesterol recognition amino acid consensus (CRAC) motif in T2R4 with alanines. We carried out functional characterization of the mutants by calcium mobilization, followed by cholesterol depletion and replenishment. CRAC motifs in GPCRs have previously been implicated in preferential cholesterol association. Our analysis shows that the CRAC motif represents an intrinsic feature of bitter taste receptors and is conserved in 22 out of 25 human T2Rs. We further demonstrate that Lys117, an important CRAC residue, is crucial in the reported cholesterol sensitivity of T2R4. Interestingly, cholesterol sensitivity of T2R4 was observed at quinine concentrations in the lower mM range. To the best of our knowledge, our results represent the first report addressing the molecular basis of cholesterol sensitivity in the function of taste receptors.
Department of Oral Biology and Manitoba Chemosensory Biology Research Group, University of Manitoba, Winnipeg, MB R3E 0W4, Canada; Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada.
Sai Prasad
SP
Pydi
CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
Md
M
Jafurulla
Department of Oral Biology and Manitoba Chemosensory Biology Research Group, University of Manitoba, Winnipeg, MB R3E 0W4, Canada.
Lisa
L
Wai
Department of Oral Biology and Manitoba Chemosensory Biology Research Group, University of Manitoba, Winnipeg, MB R3E 0W4, Canada.
Rajinder P
RP
Bhullar
Department of Oral Biology and Manitoba Chemosensory Biology Research Group, University of Manitoba, Winnipeg, MB R3E 0W4, Canada; Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada. Electronic address: Prashen.Chelikani@umanitoba.ca.
Prashen
P
Chelikani
CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India. Electronic address: amit@ccmb.res.in.
Amitabha
A
Chattopadhyay
D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D006801:Humans; D020125:Mutation, Missense; D011803:Quinine / Q000494:pharmacology*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D000098706:Taste Receptors, Type 2
D043562:Receptors, G-Protein-Coupled; D000098706:Taste Receptors, Type 2; D002784:Cholesterol; D011803:Quinine
Bitter taste receptors; CRAC; Calcium signaling; Cholesterol; GPCR; T2R4