Tryptophan Depletion Modulates Tryptophanyl-tRNA Synthetase-Mediated High-Affinity Tryptophan Uptake into Human Cells

Genes (Basel). 2020 Nov 27;11(12):1423. doi: 10.3390/genes11121423.

Abstract

The novel high-affinity tryptophan (Trp)-selective transport system is present at elevated levels in human interferon-γ (IFN-γ)-treated and indoleamine 2,3-dioxygenase 1 (IDO1)-expressing cells. High-affinity Trp uptake into cells results in extracellular Trp depletion and immune suppression. We have previously shown that both IDO1 and tryptophanyl-tRNA synthetase (TrpRS), whose expression levels are increased by IFN-γ, have a crucial function in high-affinity Trp uptake into human cells. Here, we aimed to elucidate the relationship between TrpRS and IDO1 in high-affinity Trp uptake. We demonstrated that overexpression of IDO1 in HeLa cells drastically enhances high-affinity Trp uptake upon addition of purified TrpRS protein to uptake assay buffer. We also clarified that high-affinity Trp uptake by Trp-starved cells is significantly enhanced by the addition of TrpRS protein to the assay buffer. Moreover, we showed that high-affinity Trp uptake is also markedly elevated by the addition of TrpRS protein to the assay buffer of cells overexpressing another Trp-metabolizing enzyme, tryptophan 2,3-dioxygenase (TDO2). Taken together, we conclude that Trp deficiency is crucial for high-affinity Trp uptake mediated by extracellular TrpRS.

Keywords: amino acid transport; aminoacyl-tRNA synthetase; indoleamine 2,3-dioxygenase; interferon-γ; tryptophan 2,3-dioxygenase; tryptophan uptake; tryptophanyl-tRNA synthetase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport / drug effects
  • Buffers
  • Culture Media
  • HeLa Cells
  • Humans
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / genetics
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / physiology
  • Interferon-gamma / pharmacology
  • Interferon-gamma / physiology
  • Mutation, Missense
  • Point Mutation
  • Recombinant Proteins / metabolism
  • Transfer RNA Aminoacylation
  • Tryptophan / deficiency*
  • Tryptophan / metabolism
  • Tryptophan Oxygenase / metabolism
  • Tryptophan-tRNA Ligase / pharmacology
  • Tryptophan-tRNA Ligase / physiology*
  • Up-Regulation

Substances

  • Buffers
  • Culture Media
  • IDO1 protein, human
  • Indoleamine-Pyrrole 2,3,-Dioxygenase
  • Recombinant Proteins
  • Interferon-gamma
  • Tryptophan
  • Tryptophan Oxygenase
  • Tryptophan-tRNA Ligase