L-Amino Acids Elicit Diverse Response Patterns in Taste Sensory Cells: A Role for Multiple Receptors

PLoS One. 2015 Jun 25;10(6):e0130088. doi: 10.1371/journal.pone.0130088. eCollection 2015.

Abstract

Umami, the fifth basic taste, is elicited by the L-amino acid, glutamate. A unique characteristic of umami taste is the response potentiation by 5' ribonucleotide monophosphates, which are also capable of eliciting an umami taste. Initial reports using human embryonic kidney (HEK) cells suggested that there is one broadly tuned receptor heterodimer, T1r1+T1r3, which detects L-glutamate and all other L-amino acids. However, there is growing evidence that multiple receptors detect glutamate in the oral cavity. While much is understood about glutamate transduction, the mechanisms for detecting the tastes of other L-amino acids are less well understood. We used calcium imaging of isolated taste sensory cells and taste cell clusters from the circumvallate and foliate papillae of C57BL/6J and T1r3 knockout mice to determine if other receptors might also be involved in detection of L-amino acids. Ratiometric imaging with Fura-2 was used to study calcium responses to monopotassium L-glutamate, L-serine, L-arginine, and L-glutamine, with and without inosine 5' monophosphate (IMP). The results of these experiments showed that the response patterns elicited by L-amino acids varied significantly across taste sensory cells. L-amino acids other than glutamate also elicited synergistic responses in a subset of taste sensory cells. Along with its role in synergism, IMP alone elicited a response in a large number of taste sensory cells. Our data indicate that synergistic and non-synergistic responses to L-amino acids and IMP are mediated by multiple receptors or possibly a receptor complex.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Arginine / pharmacology
  • Calcium / metabolism
  • Glutamic Acid / pharmacology
  • Glutamine / pharmacology
  • Mice
  • Mice, Knockout
  • Serine / pharmacology
  • Taste / drug effects*
  • Taste / physiology
  • Taste Buds / drug effects*
  • Taste Buds / physiology
  • Taste Perception / drug effects*
  • Taste Perception / physiology
  • Toll-Like Receptor 3 / genetics
  • Toll-Like Receptor 3 / metabolism
  • Tongue / drug effects*
  • Tongue / physiology

Substances

  • TLR3 protein, mouse
  • Toll-Like Receptor 3
  • Glutamine
  • Glutamic Acid
  • Serine
  • Arginine
  • Calcium

Grant support

This study was supported by the National Science Foundation - IOS-0951016 ERD (PI) RJD (Co-PI). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.