G‐protein coupled receptor array technologies: Site directed immobilisation of liposomes containing the H 1 ‐histamine or M 2 ‐muscarinic receptors

This paper describes a novel strategy to create a microarray of G‐protein coupled receptors (GPCRs), an important group of membrane proteins both physiologically and pharmacologically. The H 1 ‐histamine receptor and the M 2 ‐muscarinic receptor were both used as model GPCRs in this study. The receptor proteins were embedded in liposomes created from the cellular membrane extracts of Spodoptera frugiperda ( Sf9 ) insect cell culture line with its accompanying baculovirus protein insert used for overexpression of the receptors. Once captured onto a surface these liposomes provide a favourable lipidic environment for the integral membrane proteins. Site directed immobilisation of these liposomes was achieved by introduction of cholesterol‐modified oligonucleotides (oligos). These oligo/cholesterol conjugates incorporate within the lipid bilayer and were captured by the complementary oligo strand exposed on the surface. Sequence specific immobilisation was demonstrated using a quartz crystal microbalance with dissipation (QCM‐D). Confirmatory results were also obtained by monitoring fluorescent ligand binding to GPCRs captured on a spotted oligo microarray using Confocal Laser Scanning Microscopy and the ZeptoREADER microarray imaging system. Sequence specific immobilisation of such biologically important membrane proteins could lead to the development of a heterogeneous self‐sorting liposome array of GPCRs which would underpin a variety of future novel applications.