Applying label-free dynamic mass redistribution technology to frame signaling of G protein–coupled receptors noninvasively in living cells

Ralf Schröder, Johannes Schmidt, Stefanie Blättermann, Lucas Peters, Nicole Janssen, Manuel Grundmann, Wiebke Seemann, Dorina Kaufel, Nicole Merten, Christel Drewke, Jesus Gomeza, Graeme Milligan, Klaus Mohr, Evi Kostenis

Label-free dynamic mass redistribution (DMR) is a cutting-edge assay technology that enables real-time detection of integrated cellular responses in living cells. It relies on detection of refractive index alterations on biosensor-coated microplates that originate from stimulus-induced changes in the total biomass proximal to the sensor surface. Here we describe a detailed protocol to apply DMR technology to frame functional behavior of G protein-coupled receptors that are traditionally examined with end point assays on the basis of detection of individual second messengers, such as cAMP, Ca(2+) or inositol phosphates. The method can be readily adapted across diverse cellular backgrounds (adherent or suspension), including primary human cells. Real-time recordings can be performed in 384-well microtiter plates and be completed in 2 h, or they can be extended to several hours depending on the biological question to be addressed. The entire procedure, including cell harvesting and DMR detection, takes 1-2 d.