Optical biosensor differentiates signaling of endogenous PAR1 and PAR2 in A431 cells

BMC Cell Biol. 2007 Jun 22;8:24. doi: 10.1186/1471-2121-8-24.


Background: Protease activated receptors (PARs) consist of a family of four G protein-coupled receptors. Many types of cells express several PARs, whose physiological significance is mostly unknown.

Results: Here, we show that non-invasive resonant waveguide grating (RWG) biosensor differentiates signaling of endogenous protease activated receptor subtype 1 (PAR1) and 2 (PAR2) in human epidermoid carcinoma A431 cells. The biosensor directly measures dynamic mass redistribution (DMR) resulted from ligand-induced receptor activation in adherent cells. In A431, both PAR1 and PAR2 agonists, but neither PAR3 nor PAR4 agonists, trigger dose-dependent Ca2+ mobilization as well as Gq-type DMR signals. Both Ca2+ flux and DMR signals display comparable desensitization patterns upon repeated stimulation with different combinations of agonists. However, PAR1 and PAR2 exhibit distinct kinetics of receptor re-sensitization. Furthermore, both trypsin- and thrombin-induced Ca2+ flux signals show almost identical dependence on cell surface cholesterol level, but their corresponding DMR signals present different sensitivities.

Conclusion: Optical biosensor provides an alternative readout for examining receptor activation under physiologically relevant conditions, and differentiates the signaling of endogenous PAR1 and PAR2 in A431.

MeSH terms

  • Biosensing Techniques*
  • Calcium / metabolism
  • Cell Line, Tumor
  • Cholesterol / pharmacology
  • Epidermal Growth Factor / pharmacology
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism
  • Humans
  • Optics and Photonics
  • Receptor, PAR-1 / agonists
  • Receptor, PAR-1 / metabolism*
  • Receptor, PAR-2 / agonists
  • Receptor, PAR-2 / metabolism*
  • Signal Transduction* / drug effects


  • Receptor, PAR-1
  • Receptor, PAR-2
  • Epidermal Growth Factor
  • Cholesterol
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • Calcium