GPR55 is a G protein-coupled receptor that is weakly activated by some cannabinoids (CBs) at nM concentrations but displays a 5- to 10-fold greater stimulation in response to 1 μM lysophosphatidylinositol (LPI). ML-184 is a potent synthetic agonist of GPR55 (EC50 = 0.26 μM). It does not act at the related kynurenic acid receptor GPR35 and is a weak antagonist of CB1 and CB2 (IC50s = 21.8 and 15.1 μM, respectively). Like LPI, ML-184 induces phosphorylation of ERK1/2 and translocation of PKCβII to the plasma membrane by activating GPR55.
