In vitro and in vivo antagonism of a G protein-coupled receptor (S1P3) with a novel blocking monoclonal antibody

Background

S1P₃ is a lipid-activated G protein-couple receptor (GPCR) that has been implicated in the pathological processes of a number of diseases, including sepsis and cancer. Currently, there are no available high-affinity, subtype-selective drug compounds that can block activation of S1P₃. We have developed a monoclonal antibody (7H9) that specifically recognizes S1P₃ and acts as a functional antagonist.

Methodology/Principal Findings

Specific binding of 7H9 was demonstrated by immunocytochemistry using cells that over-express individual members of the S1P receptor family. We show, in vitro, that 7H9 can inhibit the activation of S1P₃-mediated cellular processes, including arrestin translocation, receptor internalization, adenylate cyclase inhibiton, and calcium mobilization. We also demonstrate that 7H9 blocks activation of S1P₃ in vivo, 1) by preventing lethality due to systemic inflammation, and 2) by altering the progression of breast tumor xenografts.

Conclusions/Significance

We have developed the first-reported monoclonal antibody that selectively recognizes a lipid-activated GPCR and blocks functional activity. In addition to serving as a lead drug compound for the treatment of sepsis and breast cancer, it also provides proof of concept for the generation of novel GPCR-specific therapeutic antibodies.