Droplet-Surface Immunoassay by Fluorescence Relocation (D-SIRE) for Hight Throughput anti-GPCR antibody discovery: towards a deeper understanding of adrenergic receptors in heart. – DSIRE_GPCR_Ab

G Protein-Coupled Receptors (GPCRs) are central players in the complex relationship of inter-cellular signaling. They act in concert by activating and influencing each other according to the context or the pathology in a complex web whose figures and meanings remain, even today, often indecipherable. Advances in the study of these phenomena is made difficult by the lack of molecular tools, in particular specific antibodies (Abs), allowing to point and modulate very precisely one of these proteins among many similar ones. Although highly anticipated, the development of such tools is hampered by the difficulty to identify among a plethora of inactive candidates the few that possess a high affinity and selectivity for one single receptor of interest. In this context, we propose an approach taking advantage of new methods for Ab production against these elusive targets and then to measure one by one, on millions, the affinity of the Abs thus obtained for the native protein in its membrane environment. This precise measurement is made possible via microfluidic technologies which, combined with a biocompatible chemistry, allows the formation of millions of microcapsules whose surface serves as sensors. These sensors allow to measure finely the protein-Ab interaction at a speed of a thousand events per second, to sort the best ones and to recover the producing clones alive. The methodology will be applied to the development of Abs specifically targeting the ß1 and ß2 adrenergic receptors, key GPCRs involved in the heart physiology. In a second step, a measure of selectivity between several targets will be directly integrated into the sorting criterion in order to reach the very rare specific antibodies. These candidates will be produced on a large scale and validated by biophysical measurements. They will be then used to decipher the precise involvement of ß1 and ß2 adrenergic receptors in heart cardiomyocytes and their relative contribution in heart failure phenomena.