GPR55 is an orphan G protein-coupled receptor that functions as a lipid sensor activated by endogenous lysophosphatidylinositol (LPI) and related lipids 1. Upon activation, GPR55 initiates rapid intracellular signaling through heterotrimeric G13 proteins and ERK pathways, triggering calcium release from intracellular stores and cytoskeletal reorganization via RHOA-mediated stress fiber formation 1. The receptor exhibits broad tissue distribution with roles in metabolic regulation, vascular function, and bone homeostasis 2. Pharmacologically, GPR55 is modulated by diverse ligands including endocannabinoids, phytocannabinoids like cannabidiol, and synthetic agonists 34. In macrophages, GPR55 activation suppresses ABCA1-mediated cholesterol efflux, promoting foam cell formation and atherosclerotic pathology. Clinically, GPR55 dysregulation is implicated in multiple disease states: the LPI/GPR55 axis promotes oncogenic processes including proliferation, migration, and metastasis across cancer types 2, while receptor modulation shows therapeutic promise for epilepsy, pain, inflammation, and metabolic disorders including type 2 diabetes 56. GPR55 and its ligands are emerging as potential biomarkers for cancer diagnosis and progression.