35 research outputs found
Optical biosensor differentiates signaling of endogenous PAR1 and PAR2 in A431 cells
<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Results</p> <p>Here, we show that non-invasive resonant waveguide grating (RWG) biosensor differentiates signaling of endogenous protease activated receptor subtype 1 (PAR<sub>1</sub>) and 2 (PAR<sub>2</sub>) 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 PAR<sub>1 </sub>and PAR<sub>2 </sub>agonists, but neither PAR<sub>3 </sub>nor PAR<sub>4 </sub>agonists, trigger dose-dependent Ca<sup>2+ </sup>mobilization as well as G<sub>q</sub>-type DMR signals. Both Ca<sup>2+ </sup>flux and DMR signals display comparable desensitization patterns upon repeated stimulation with different combinations of agonists. However, PAR<sub>1 </sub>and PAR<sub>2 </sub>exhibit distinct kinetics of receptor re-sensitization. Furthermore, both trypsin- and thrombin-induced Ca<sup>2+ </sup>flux signals show almost identical dependence on cell surface cholesterol level, but their corresponding DMR signals present different sensitivities.</p> <p>Conclusion</p> <p>Optical biosensor provides an alternative readout for examining receptor activation under physiologically relevant conditions, and differentiates the signaling of endogenous PAR<sub>1 </sub>and PAR<sub>2 </sub>in A431.</p