Abstract 54: The many faces of antibody in G protein-coupled receptor biology

Abstract

Abstract G protein-coupled receptors (GPCRs), the largest family of cell-surface receptor proteins mediating signal transmission, play a pivotal role in many physiological functions and are involved in multiple diseases. Although receptor activities of GPCRs are successfully modulated by many small molecules which represent 30% of all marketed drugs today, in fact only a few GPCR members are targeted and many more GPCRs of interest are intractable targets of small molecules, like orphan GPCRs and GPCRs with large binding sites. Besides, small molecule drugs rarely trigger GPCR-mediated apoptosis or induce direct cell killing, which is crucial for cancer therapies. Therefore, for these GPCRs, antibody-based drug would be a good alternative. Despite being eagerly sought for, the production of monoclonal antibody (mAb) targeting GPCR is hindered by the low expression of recombinant GPCR on cell surface, and relatively small exposed regions with glycosylation and conformational heterogeneity. Therefore those conventional methods that were well established for generation of mAbs targeting soluble proteins usually showed frustrating results in the case of GPCRs. To bypass the production and purification of recombinant GPCR proteins, we developed a novel approach of transplanting immunogenic conformational epitopes of GPCR into an antibody scaffold to make a water soluble surrogate antigen of GPCR, named as GPCR-antigenized antibody which can be easily and abundantly produced in bacteria for animal immunization. In coupled with phage display technology and cell panning strategy, which allow the retrieval of specific binders from a huge number of candidates, we have successfully isolated scFv antibodies for two human GPCRs, the MAS1 receptor and the chemokine receptor CXCR4. These antibodies showed good specificity in immunofluorescent staining, flow cytometry analysis, western protein immunoblot and immunoprecipitation assay. The results demonstrated this novel approach may offer a generic and effective method to generate specific monoclonal antibody targeting GPCR for diagnostic and therapeutic applications. [The project is partly funded by a CUHK direct grant (4054300)] Citation Format: Lei Chen, Wing-Tai Cheung. The many faces of antibody in G protein-coupled receptor biology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 54. doi:10.1158/1538-7445.AM2017-54