The Mechanisms of GPR55 Receptor Functonal Selectivity

The objective of the study was to establish the mechanisms of multidirectional signal transmission through the same G-protein coupled receptor GPR55. Using the CRISPR-Cas9 system, clones of the MDA-MB-231 line knockout for the GPR55, CB1, CB2, GPR18, and TRPV1 receptor genes were obtained. On clones of the MDA-MB-231 line with a knockout CB2 receptor, the cytotoxic activity of the pro-apoptotic ligand docosahexaenoyldopamine (DHA-DA) did not change or slightly increased, while the pro-proliferative activity of the most active synthetic ligand of the GPR55 receptor (ML-184) completely disappeared. On the original line MDA-MB-231, the stimulatory effect of ML-184 is removed by the CB2 receptor blocker, but not by GPR55. At the same time, the stimulating effect of ML-184 is practically not manifested on cell lines knockout at the GPR55 receptor. Thus, it can be confidently assumed that when proliferation is stimulated with the participation of the GPR55 receptor, a signal is transmitted from the CB2 receptor to the GPR55 receptor due to the formation of a heterodimer. GPR18 and TRPV1 receptors are additionally involved in the implementation of the cytotoxic effect of DHA-DA, while the CB1 receptor is not involved. In the implementation of the cytotoxic action of DHA-DA, the predominant participation of one of the G subunits was not found, but the G13 subunit plays a decisive role in the implementation of the proproliferative action.