Expression of an epitope tagged human C5a receptor and antibody-mediated immobilization of detergent-solubilized receptor for drug discovery screening.

In order to screen combinatorial libraries of peptides and/or small organic molecules against the human C5a receptor, we have developed a novel method for immobilizing and screening 7-transmembrane segment (7-TMS) receptors. The epitope for a high affinity monoclonal antibody (mAb179) was added to the C-terminus of the human C5a receptor, and CHO cell lines expressing the epitope tagged receptor (C5aR-KH) and the wild-type receptor (C5aR) were established. The addition of the epitope tag did not affect the affinity of C5aR-KH for C5a. The epitope tag allowed for mAb179-mediated immobilization of active receptor either in intact membranes or following detergent extraction with digitonin or Chaps. If this method is generally applicable to other 7-TMS receptors it may have broad utility for drug discovery screening as well as other applications.