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Electrochemical Based Biosensors
Biosensors 2012, 2(3), 273-290; doi:10.3390/bios2030273
Article

A Comparative Study of Impedance versus Optical Label-Free Systems Relative to Labelled Assays in a Predominantly Gi Coupled GPCR (C5aR) Signalling

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Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
* Author to whom correspondence should be addressed.
Received: 30 May 2012 / Revised: 11 July 2012 / Accepted: 24 July 2012 / Published: 26 July 2012
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Abstract

Profiling ligand function on G-protein coupled receptors (GPCRs) typically involves using transfected cells over-expressing a target of interest, a labelled ligand, and intracellular secondary messenger reporters. In contrast, label-free assays are sensitive enough to allow detection in native cells, which may provide a more physiologically relevant readout. Here, we compare four agonists (native agonists, a peptide full agonist and a peptide partial agonist) that stimulate the human inflammatory GPCR C5aR. The receptor was challenged when present in human monocyte-derived macrophages (HMDM) versus stably transfected human C5aR-CHO cells. Receptor activation was compared on label-free optical and impedance biosensors and contrasted with results from two traditional reporter assays. The rank order of potencies observed across label-free and pathway specific assays was similar. However, label-free read outs gave consistently lower potency values in both native and transfected cells. Relative to pathway-specific assays, these technologies measure whole-cell responses that may encompass multiple signalling events, including down-regulatory events, which may explain the potency discrepancies observed. These observations have important implications for screening compound libraries against GPCR targets and for selecting drug candidates for in vivo assays.
Keywords: GPCR; impedance and optical biosensors; label-free; secondary messenger; signal transduction GPCR; impedance and optical biosensors; label-free; secondary messenger; signal transduction
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Halai, R.; Croker, D.E.; Suen, J.Y.; Fairlie, D.P.; Cooper, M.A. A Comparative Study of Impedance versus Optical Label-Free Systems Relative to Labelled Assays in a Predominantly Gi Coupled GPCR (C5aR) Signalling. Biosensors 2012, 2, 273-290.

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