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The structure-function role of C-terminus in human bitter taste receptor T2R4 signaling

Jasbir Upadhyaya1, Nisha Singh1, Rajinder P Bhullar2

  • 1Department of Oral Biology, College of Dentistry, University of Manitoba, Winnipeg, MB R3E 0W2, Canada; Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB R3E 0W2, Canada.

Biochimica Et Biophysica Acta
|April 11, 2015
PubMed

Insights

Researchers identified a conserved KLK/R motif in bitter taste receptors (T2Rs). Mutations in T2R4

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Pharmacology

Background:

  • Bitter taste in humans is mediated by 25 G protein-coupled receptors called bitter taste receptors (T2Rs).
  • T2Rs have diverse extraoral roles, making them potential therapeutic targets.
  • Structure-function studies have focused on transmembrane regions, with limited research on the T2R carboxyl-terminus (C-terminus).

Purpose of the Study:

  • To investigate the role of the T2R C-terminus in receptor trafficking and function.
  • To identify conserved motifs within the T2R C-terminus.
  • To elucidate the structure-function relationship of the T2R4 C-terminus.

Main Methods:

  • Site-directed mutagenesis was used to study 16 residues in the T2R4 C-terminus.
  • Mutations were analyzed for their effects on plasma membrane trafficking.
  • Receptor function was characterized using the T2R4 agonist quinine.

Main Results:

  • A conserved KLK/R motif was identified in the C-termini of 19 out of 25 T2Rs.
  • Most C-terminal mutations in T2R4 resulted in defective receptor trafficking.
  • Mutation of Lys296 in the KLK motif led to constitutive T2R4 activity, indicating its crucial role.

Conclusions:

  • The T2R C-terminus, particularly the KLK motif, plays a critical role in receptor trafficking and function.
  • Specific residues like Lys294, Leu295, and Lys296 are essential for T2R4 activity.
  • This study provides novel mechanistic insights into T2R C-terminus structure-function relationships.
Keywords:
Bitter taste receptor (T2R)Carboxyl-terminus (C-terminus)Constitutively active mutant (CAM)G protein-coupled receptor (GPCR)Membrane proximal basic residue (MPBR)

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