Affinage

GPR55

G-protein coupled receptor 55 · UniProt Q9Y2T6

Length
319 aa
Mass
36.6 kDa
Annotated
2026-04-28
100 papers in source corpus 37 papers cited in narrative 37 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GPR55 is a class A G protein-coupled receptor activated by lysophosphatidylinositol (LPI) and select cannabinoid ligands that signals through Gα13, Gq, and G12 to regulate small GTPases (RhoA, Cdc42, Rac1), intracellular calcium mobilization, and downstream ERK1/2, NFAT, NF-κB, and CREB transcriptional programs (PMID:17765871, PMID:17876302, PMID:18757503, PMID:20136841). LPI-activated GPR55 couples to RhoA via Gα13 to elicit IP3 receptor-mediated Ca²⁺ release and voltage-gated Ca²⁺ channel influx, driving diverse cellular responses including neurite retraction, growth cone remodeling, presynaptic neurotransmitter release enhancement, osteoclast polarization, insulin secretion from pancreatic β-cells, and regulation of intraepithelial lymphocyte migration (PMID:18263732, PMID:21904624, PMID:23472002, PMID:19805329, PMID:21885477, PMID:29222090). GPR55 forms functional heteromers with CB1 and CB2 cannabinoid receptors that bidirectionally modulate each partner's signaling output, including ERK1/2 and NFAT activation (PMID:23161546, PMID:25048571). GPR55 deficiency in mice increases trabecular bone volume due to impaired osteoclast resorption and reduces peripheral insulin sensitivity with increased adiposity, establishing non-redundant physiological roles in bone homeostasis and metabolic regulation (PMID:19805329, PMID:30148676).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 2007 High

    Establishing that GPR55 is a functional receptor for cannabinoid ligands and LPI resolved its deorphanization and identified its primary G-protein coupling partner Gα13 and downstream small GTPase effectors RhoA, Cdc42, and Rac1.

    Evidence GTPγS binding, G-protein blocking antibodies/peptides, ERK phosphorylation, and Ca²⁺ imaging in GPR55-transfected HEK293 cells with cannabinoid and LPI stimulation

    PMID:17765871 PMID:17876302

    Open questions at the time
    • Relative physiological importance of LPI vs. cannabinoid ligands in vivo was unresolved
    • Crystal structure of GPR55 with ligand not available
    • Coupling selectivity between Gα13, Gq, and G12 not fully dissected
  2. 2008 High

    Defining the intracellular signaling cascade — Gq/G12→RhoA→PLC→IP3R Ca²⁺ store release — in both native neurons and heterologous cells established the canonical GPR55 Ca²⁺ signaling pathway and showed GPR55 also inhibits M-type K⁺ current.

    Evidence Ca²⁺ imaging in DRG neurons and HEK293 cells with pharmacological pathway dissection; M-current electrophysiology; siRNA/antibody knockdown of G-proteins and NFAT reporter assays

    PMID:18263732 PMID:18757503

    Open questions at the time
    • Whether G13 vs. Gq dominates in specific native cell types remained unclear
    • Mechanism of M-current inhibition not fully resolved
  3. 2009 High

    Demonstrating that putative CB1 antagonists (AM251, rimonabant) are GPR55 agonists while CP55,940 acts as a GPR55 antagonist reframed the pharmacological tool compound landscape and revealed biased agonism at GPR55.

    Evidence β-arrestin trafficking, PKCβII membrane recruitment, ERK1/2 phosphorylation, and receptor internalization assays in GPR55-expressing cells

    PMID:19723626

    Open questions at the time
    • Whether biased agonism translates to differential physiological outcomes in vivo was unknown
    • Structural basis for agonist vs. antagonist activity not determined
  4. 2009 High

    GPR55 knockout mice revealed a physiological role in bone homeostasis: GPR55 drives osteoclast polarization and resorption via Rho/ERK, and its absence increases trabecular bone volume.

    Evidence In vitro osteoclast resorption assays from GPR55⁻/⁻ macrophages, Rho/ERK activation, micro-CT and histomorphometry in knockout mice

    PMID:19805329

    Open questions at the time
    • Whether GPR55 also regulates osteoblast function was not tested
    • Mechanism linking RhoA to osteoclast sealing zone formation not detailed
  5. 2010 High

    Identification of an autocrine LPI/GPR55 signaling loop in cancer cells — with LPI synthesized by cPLA2 and exported by ABCC1/MRP1 — provided a mechanistic basis for GPR55-driven cancer cell proliferation and revealed ligand-specific biased signaling profiles across NFAT, NF-κB, CREB, and ERK pathways.

    Evidence siRNA knockdown of GPR55 and ABCC1 in cancer cells, Ca²⁺ imaging, Akt/ERK phosphorylation; multi-assay signaling profiling with diverse ligands in GPR55-HEK293 cells

    PMID:20136841 PMID:20838378

    Open questions at the time
    • In vivo relevance of autocrine LPI loop in tumors not established at this point
    • Structural determinants of biased agonism unknown
  6. 2011 High

    GPR55 functions in native neuronal and endocrine cells: it induces neurite retraction via G13/RhoA in PC12 cells, augments glucose-stimulated insulin secretion in pancreatic β-cells, and modulates neutrophil migration through cross-talk with CB2 at the level of Rac2/Cdc42.

    Evidence siRNA knockdown and GPR55 KO in PC12 neurons, β-cell Ca²⁺ imaging and insulin secretion assays with KO mice, GTPase activity and migration assays in primary neutrophils

    PMID:21467997 PMID:21885477 PMID:21904624

    Open questions at the time
    • RhoA-dependent neurite retraction pathway components between RhoA and cytoskeleton not mapped
    • Molecular interface of GPR55–CB2 cross-talk not defined
  7. 2012 High

    Demonstration that GPR55 and CB1 form heteromers that reciprocally modulate each other's signaling (CB1 inhibits GPR55→NFAT/ERK; GPR55 enhances CB1→ERK/NFAT) established that GPR55 functions not only as a standalone receptor but as an allosteric modulator within cannabinoid receptor complexes.

    Evidence Co-immunoprecipitation, FRET, NFAT/SRE reporters, and ERK phosphorylation in co-transfected HEK293 cells

    PMID:23161546

    Open questions at the time
    • Heteromer stoichiometry and interface residues unknown
    • Native tissue demonstration of CB1-GPR55 heteromers not provided
  8. 2013 High

    GPR55 operates presynaptically at hippocampal CA3-CA1 synapses to increase glutamate release probability via Ca²⁺ release from presynaptic stores, and inhibits neurogenic contractions in the colon, establishing circuit-level roles in synaptic transmission and gut motility.

    Evidence Two-photon presynaptic Ca²⁺ imaging and optical quantal analysis in GPR55 KO hippocampal slices; isometric tension recordings in colonic strips from GPR55⁻/⁻ and CB1⁻/⁻/CB2⁻/⁻ mice

    PMID:22759743 PMID:23472002

    Open questions at the time
    • Identity of the presynaptic phospholipid synthesis pathway downstream of GPR55 not determined
    • Whether presynaptic GPR55 engages Gα13/RhoA or an alternative pathway in boutons was unresolved
  9. 2014 High

    GPR55-CB2 heteromerization was confirmed by BRET and co-IP, with functional consequences — reduced NFAT/NF-κB but potentiated ERK signaling — that alter antitumoral cannabinoid efficacy in vivo, linking heteromer biology to cancer pharmacology.

    Evidence BRET, co-IP, signaling reporters, label-free DMR, and in vivo tumor models

    PMID:24942731 PMID:25048571

    Open questions at the time
    • Whether heteromer-selective ligands can be developed was untested
    • Contribution of GPR55-CB2 heteromers in non-cancer immune contexts not examined
  10. 2015 High

    GPR55 was shown to guide retinal ganglion cell axon growth and branching during development and to regulate nociception via IP3R/P/Q-type Ca²⁺ channels in PAG neurons, extending its neural roles beyond synaptic modulation to developmental wiring and pain processing.

    Evidence Growth cone morphology and chemotaxis assays in GPR55 KO retinal neurons with in vivo axonal branching; Ca²⁺ imaging, electrophysiology, and intra-PAG microinjection with nociception testing

    PMID:25972448 PMID:26730399

    Open questions at the time
    • Downstream effectors linking GPR55 to growth cone cytoskeleton remodeling not fully identified
    • Whether GPR55 nociceptive role is tonic or only activated under specific conditions was unclear
  11. 2015 High

    LPI/GPR55 promotes cancer cell migration, adhesion, and metastasis via ERK-dependent transcription factor ETV4/PEA3 activation and disruption of endothelial barriers, positioning GPR55 as a prometastatic receptor in colorectal and breast cancers.

    Evidence siRNA knockdown, pharmacological GPR55 antagonism (CID16020046, CBD), endothelial permeability assays, in vivo liver metastasis and breast cancer metastasis models

    PMID:26436760 PMID:27340777

    Open questions at the time
    • Whether GPR55 antagonism has therapeutic efficacy in established tumors not tested
    • Relative contribution of autocrine vs. stromal LPI not dissected in vivo
  12. 2017 High

    GPR55 negatively regulates intraepithelial lymphocyte migration in the small intestine and potentiates hippocampal LTP, and mediates endothelium-dependent vasorelaxation via biphasic PLC-IP3/ROCK-RhoA Ca²⁺ signaling and blood-brain barrier permeability modulation.

    Evidence Intravital imaging of GPR55⁻/⁻ IELs; hippocampal slice electrophysiology in KO mice; wire myography and single-cell Ca²⁺ imaging in mesenteric artery endothelial cells; in vivo BBB permeability assay with Evans Blue

    PMID:25652040 PMID:28653801 PMID:29222090 PMID:31279825

    Open questions at the time
    • Molecular mechanism of GPR55-dependent LTP potentiation beyond presynaptic release probability not defined
    • Whether BBB permeability effects are physiologically relevant or only pharmacological not established
  13. 2018 High

    GPR55 deficiency causes systemic insulin resistance with reduced Akt phosphorylation in muscle, adipose, and liver, while GPR55 expression is itself regulated by p53 via miR-34b-3p, connecting GPR55 to both metabolic homeostasis and tumor-suppressor pathways.

    Evidence GPR55 KO mouse metabolic phenotyping, insulin signaling Western blots across tissues, siRNA in myotubes; miR-34b-3p overexpression and luciferase reporter assays in pancreatic cancer cells with KPC mouse model

    PMID:30061636 PMID:30148676

    Open questions at the time
    • Whether metabolic and oncogenic GPR55 functions are mechanistically linked or independent was unknown
    • Tissue-specific GPR55 KO models not employed
  14. 2019 High

    GPR55 activates the ROCK/p38 MAPK pathway in cardiomyocytes to exacerbate ischemia/reperfusion injury, and GPR55 agonists protect β-cells from ER stress-induced apoptosis via CREB/Bcl-2, revealing context-dependent protective vs. pathological outcomes.

    Evidence Dynamic mass redistribution in iPSC cardiomyocytes, isolated perfused heart I/R in GPR55⁻/⁻ mice, ROCK inhibitor; cell viability and CREB/Bcl-2 Western blots in β-cell lines

    PMID:30841431 PMID:31149342

    Open questions at the time
    • β-cell protective effects not validated in GPR55 KO islets
    • How GPR55 engages ROCK in cardiomyocytes but not consistently RhoA in β-cells is unexplained

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the high-resolution structure of GPR55 with LPI or heteromer partners, the identity of tissue-specific signaling complexes that determine divergent outcomes (e.g., cardioprotective vs. cardiotoxic), and whether GPR55-selective therapeutics can achieve pathway-biased efficacy in metabolic disease or cancer.
  • No experimental structure (cryo-EM or crystal) of GPR55 exists
  • No conditional tissue-specific knockout studies reported
  • No clinical trials targeting GPR55 documented in the timeline

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060089 molecular transducer activity 5 GO:0008289 lipid binding 2
Localization
GO:0005829 cytosol 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-162582 Signal Transduction 6 R-HSA-112316 Neuronal System 4 R-HSA-1643685 Disease 4 R-HSA-1430728 Metabolism 3 R-HSA-168256 Immune System 2 R-HSA-1266738 Developmental Biology 1
Partners
CDC42CNR1CNR2GNA12GNA13GNAQRAC1RHOA
Complex memberships
GPR55-CB1 heteromerGPR55-CB2 heteromer

Evidence

Reading pass · 37 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 GPR55 binds the cannabinoid ligand CP55940 and is activated by endocannabinoids including anandamide and virodhamine (nM potencies); it couples to Gα13 and mediates activation of RhoA, Cdc42, and Rac1 downstream. GTPγS binding assay in GPR55-transfected cells; antibody/peptide G-protein blocking; downstream signaling pathway measurements British journal of pharmacology High 17876302
2007 Lysophosphatidylinositol (LPI) is an endogenous ligand for GPR55: LPI specifically induces ERK phosphorylation, Ca2+ transient, and GTPγS binding in GPR55-expressing HEK293 cells but not in vector-transfected controls. ERK phosphorylation assay, Ca2+ imaging, GTPγS binding in stably/transiently GPR55-expressing vs. control HEK293 cells Biochemical and biophysical research communications High 17765871
2008 GPR55 activation by cannabinoids (Δ9-THC, methanandamide, JWH015) increases intracellular calcium in dorsal root ganglion neurons and HEK293 cells via Gq, G12, RhoA, actin, phospholipase C, and IP3R-gated Ca2+ stores; GPR55 also inhibits M current. Ca2+ imaging in DRG neurons and HEK293 cells; pharmacological dissection of signaling pathway; electrophysiology (M current recording) Proceedings of the National Academy of Sciences of the United States of America High 18263732
2008 LPI induces marked GPR55 internalization and a sustained, oscillatory Ca2+ release pathway in GPR55-stable HEK293 cells that is dependent on Gα13 and requires RhoA activation; this cascade leads to NFAT nuclear translocation. AM251 also evokes GPR55-mediated Ca2+ signaling. Ca2+ imaging, siRNA/antibody knockdown of G-proteins, RhoA activity assay, NFAT reporter assay, receptor internalization assay in stable GPR55-HEK293 cells FASEB journal High 18757503
2009 AM251 and SR141716A (rimonabant), CB1 antagonists, act as GPR55 agonists inducing β-arrestin trafficking and PKCβII membrane recruitment; CP55,940 acts as a GPR55 antagonist/partial agonist, blocking GPR55 internalization and ERK1/2 phosphorylation. β-arrestin–GFP biosensor trafficking assay, PKCβII membrane recruitment assay, ERK1/2 phosphorylation, receptor internalization assay The Journal of biological chemistry High 19723626
2009 GPR55 is expressed in osteoclasts and GPR55 agonists (O-1602, LPI) stimulate osteoclast polarization and resorption, activating Rho and ERK1/2; these stimulatory effects are attenuated in osteoclasts from GPR55−/− macrophages. GPR55−/− mice show increased trabecular bone volume and unresorbed cartilage. In vitro osteoclast resorption assays, Rho/ERK activation assays, GPR55−/− macrophage-derived osteoclasts, histomorphometry and micro-CT in knockout mice Proceedings of the National Academy of Sciences of the United States of America High 19805329
2009 GPR55 atypical cannabinoids O-1602 and abnormal cannabidiol stimulate GPR55-dependent GTPγS activity (EC50 ~2 nM) in GPR55-expressing HEK293T cells; however, GPR55 genetic deletion does not alter the vasodilator responses to these compounds in mice, dissociating GPR55 activation from vascular effects. GTPγS assay in GPR55-transfected cells; blood pressure measurement and isolated artery myography in GPR55 KO vs. WT mice British journal of pharmacology High 17704827
2010 GPR55 mediates LPI-induced calcium mobilization and activation of Akt and ERK1/2 in prostate and ovarian cancer cells; LPI is synthesized by cytosolic phospholipase A2 and pumped out via ABCC1/MRP1 transporter, establishing an autocrine LPI/GPR55 loop that regulates cancer cell proliferation. siRNA knockdown, pharmacological blockade, Ca2+ imaging, Western blot for Akt/ERK phosphorylation, ABCC1/MRP1 transporter assays Oncogene High 20838378
2010 GPR55 ligands (LPI, AM251, AM281, SR141716A) promote coupling to multiple downstream signaling pathways including Ca2+ signaling, ERK1/2 MAPK, and transcription factors NFAT, NF-κB, and CREB, with ligand-specific differences in potency and efficacy depending on the assay used. Ca2+ assay, ERK1/2 phosphorylation, NFAT/NF-κB/CREB reporter assays, receptor endocytosis, label-free optical dynamic mass redistribution in stable GPR55-HEK293 cells British journal of pharmacology High 20136841
2011 LPI causes neurite retraction in differentiated PC12 cells through endogenous GPR55 via a G13- and RhoA-dependent (but Gq-independent) pathway; cannabinoids do not activate endogenous GPR55 in these cells. GPR55 localizes to plasma membrane and growth cones in differentiated PC12 cells. siRNA knockdown, C3 toxin RhoA inactivation, Ca2+ imaging, ERK1/2 assay, immunofluorescence localization in PC12 cells endogenously expressing GPR55 PloS one High 21904624
2011 GPR55 and CB2 receptor interfere with each other's signaling at the level of small GTPases Rac2 and Cdc42 in human neutrophils; GPR55 activation augments CB2-mediated migration while inhibiting degranulation and ROS production, using GPR55-expressing HEK293, HL60 cells, and primary neutrophils. GTPase activity assays (Rac2, Cdc42), cell migration assays, degranulation/ROS assays in primary neutrophils and cell lines Cell research High 21467997
2012 GPR55 and CB1 receptor co-expressed in HEK293 cells form heteromers, and CB1 co-expression specifically inhibits GPR55-mediated NFAT and SRF transcription factor activation and ERK1/2 phosphorylation; conversely, GPR55 presence enhances CB1R-mediated ERK1/2 and NFAT activation. Co-immunoprecipitation, FRET/co-localization, NFAT/SRE reporter assays, ERK1/2 phosphorylation in HEK293 cells The Journal of biological chemistry High 23161546
2013 GPR55 activation at CA3-CA1 synapses transiently increases release probability via Ca2+ release from presynaptic Ca2+ stores; GPR55 co-localizes with vesicular glutamate transporter 1 (vGluT1) in axonal boutons. Postsynaptic Ca2+ stores are unaffected. The cascade involves presynaptic phospholipid synthesis. Two-photon Ca2+ imaging in presynaptic boutons, optical quantal analysis in postsynaptic spines, GPR55 KO slices, pharmacological antagonism, immunolocalization in hippocampal slices Proceedings of the National Academy of Sciences of the United States of America High 23472002
2014 GPR55 and CB2 receptor form heteromers in HEK293 cells as demonstrated by co-immunoprecipitation and BRET; heteromerization reduces GPR55-mediated NFAT/NF-κB/CRE activation but potentiates ERK1/2 MAPK activation, and modulates CB2R-mediated signaling; modulation of these heteromers alters antitumoral cannabinoid activity in vivo. Co-immunoprecipitation, BRET assay, ERK1/2 phosphorylation, NF-κB/NFAT/CRE reporter assays, label-free DMR and impedance assays, in vivo tumor models British journal of pharmacology High 25048571
2014 CB2R and GPR55 form heteromers with unique signaling properties in cancer cells; modulation of these heteromers alters the antitumoral activity of cannabinoids in vivo. Co-immunoprecipitation, BRET, signaling assays, in vivo cancer models The Journal of biological chemistry High 24942731
2011 GPR55 activation in rat pancreatic β-cells increases glucose-stimulated Ca2+ transients and insulin secretion; this effect is partly GPR55-dependent (blunted in Gpr55 KO mice); systemic GPR55 activation increases glucose tolerance and plasma insulin in vivo. Ca2+ imaging, insulin secretion assay, GPR55 KO mice, in vivo glucose tolerance test The Journal of endocrinology High 21885477
2015 LPI activates GPR55 in rat periaqueductal gray (PAG) neurons causing Ca2+ release from endoplasmic reticulum via IP3 receptors and Ca2+ entry via P/Q-type voltage-gated Ca2+ channels, depolarizes PAG neurons, and reduces nociceptive threshold following intra-PAG injection in a GPR55-dependent manner. Ca2+ imaging in dissociated PAG neurons, pharmacological dissection, electrophysiology, intra-PAG microinjection with hot-plate nociception test Molecular pharmacology High 25972448
2017 GPR55 negatively regulates TCRγδ intraepithelial lymphocyte migration in the small intestine: GPR55 mediates migration inhibition in response to LPI; GPR55-deficient IELs migrate faster and interact more extensively with epithelial cells. GPR55 also negatively regulates T cell homing to the small intestine and γδT cell egress from Peyer's patches. Intravital imaging of GPR55−/− vs. WT IELs, homing assays, GPR55 antagonist treatment, intestinal permeability assay Science immunology High 29222090
2016 LPI activates GPR55 in mouse and human islets, stimulating Ca2+ increase and insulin secretion via O-1602; O-1602-induced Ca2+ and insulin responses are abolished in GPR55−/− mouse islets. However, LPI and CBD also stimulate islets via GPR55-independent pathways. O-1602 does not activate RhoA in MIN6 β-cells. Fura-2 microfluorimetry, dynamic insulin secretion (radioimmunoassay), GPR55−/− islets, RhoA pull-down assay Diabetes, obesity & metabolism High 27561953
2011 GPR55 agonist binding site modeled using novel selective high-potency agonists (CID1792197, CID1172084, CID2440433) identified by β-arrestin HTS screen; ligands with inverted-L or T shapes bind vertically deep in the receptor pocket with broad head regions occupying a horizontal pocket near extracellular loops, mimicking LPI shape and electrostatics. β-arrestin high-throughput screen of ~300,000 compounds; computational modeling of GPR55 activated state; comparison of agonist binding conformations Biochemistry Medium 21534610
2013 GPR55 antagonist binding site involves a head region occupying extracellular loop horizontal pocket and a pendant aromatic ring; selective GPR55 antagonists identified by β-arrestin HTS (IC50 0.16–2.72 μM) with no activity at GPR35, CB1, or CB2 up to 20 μM. β-arrestin high-throughput screen of ~300,000 compounds; computational modeling of GPR55 inactive state Biochemistry Medium 24274581
2015 GPR55 promotes migration and adhesion of HCT116 colon cancer cells and liver metastasis in vivo; LPI activates GPR55 to decrease endothelial monolayer integrity; these effects are blocked by GPR55 antagonists CID16020046 and cannabidiol or GPR55 siRNA knockdown. Adhesion and migration assays, GPR55 siRNA knockdown, endothelial permeability assay, in vivo liver metastasis mouse model British journal of pharmacology High 26436760
2015 LPI/GPR55 promotes metastasis in triple-negative breast cancer cells via coupling to Gq/11 proteins and subsequent ERK-mediated activation of the transcription factor ETV4/PEA3, conferring pro-invasive features in vitro and in vivo. In vitro invasion assays, in vivo metastasis models, pharmacological and siRNA inhibition of GPR55, ERK inhibition, ETV4 reporter assays Oncotarget High 27340777
2019 LPI/GPR55 activates the ROCK/p38 MAPK pathway in cardiomyocytes and exacerbates myocardial ischemia/reperfusion injury; this GPR55/ROCK-dependent worsening of injury is absent in GPR55−/− mouse hearts and blocked by ROCK inhibitor Y-27632. Dynamic mass redistribution assay in mouse and human iPSC cardiomyocytes, ROCK/p38 MAPK phosphorylation assays, isolated perfused heart I/R model in WT vs. GPR55−/− mice Pharmacology research & perspectives High 31149342
2018 GPR55 inhibition in pancreatic cancer reduces MAPK signaling and ribonucleotide reductase M1 levels, slowing cell cycle progression; GPR55 protein expression is regulated by p53 through microRNA miR34b-3p. siRNA/pharmacological inhibition (CBD) of GPR55, MAPK signaling Western blots, RRM1 protein quantification, KPC transgenic mouse model, miR34b-3p luciferase reporter and miRNA overexpression assays Oncogene High 30061636
2015 GPR55 is expressed in retinal ganglion cell axons during development and regulates growth cone morphology (size, filopodia number) and axon outgrowth; LPI and O-1602 produce chemo-attraction and increase GC size, while CBD produces chemo-repulsion; GPR55−/− mice show reduced axonal branching in visual targets. In vitro neuron culture with GPR55 KO, growth cone morphology analysis, chemotaxis assay, intraocular LPI/CBD injection with axonal branching quantification in vivo eNeuro High 26730399
2017 LPI activates GPR55 in rat mesenteric artery endothelial cells causing biphasic Ca2+ elevation via PLC-IP3 pathway (early phase) and ROCK-RhoA pathway (late phase); LPI induces endothelium-dependent vasorelaxation via Ca2+-sensitive K+ channels and reduces systemic arterial pressure. Wire myography, single-cell Ca2+ imaging, pharmacological pathway dissection (thapsigargin, U73122, Y-27632, charybdotoxin, iberiotoxin), GPR55 expression confirmed by RT-PCR British journal of pharmacology High 25652040
2017 LPI activates GPR55 on brain microvascular endothelial cells causing Ca2+ influx via voltage-gated Ca2+ channels (PLC-independent), membrane depolarization followed by hyperpolarization via Ca2+-activated K+ channels, transient disruption of tight/adherens junctions, and increased blood-brain barrier permeability in vivo. Ca2+ imaging, ECIS (electrical resistance), immunofluorescence of junction proteins, in vivo Evans Blue BBB permeability assay, GPR55 antagonist ML-193 Neuroscience High 31279825
2017 LPI potentiates long-term potentiation (LTP) at CA1 hippocampal synapses in a GPR55-dependent manner; this effect is absent in GPR55−/− mice and blocked by GPR55 antagonist CID16020046; paired-pulse ratio is enhanced by LPI in GPR55+/+ but not GPR55−/− mice. Electrophysiology (LTP induction) in hippocampal slices from GPR55+/+ and GPR55−/− mice, pharmacological antagonism Hippocampus High 28653801
2011 Anandamide (AEA) and virodhamine act as partial agonists/modulators at GPR55, enhancing agonist-mediated β-arrestin2 recruitment at low concentrations while inhibiting it at high concentrations, and significantly attenuating agonist-induced GPR55 internalization. β-arrestin2 distribution assay, GPR55 internalization assay in GPR55-transfected U2OS cells (minimal CB1/CB2 expression) Journal of neuroimmune pharmacology Medium 22454039
2017 N-arachidonoyl glycine (NAGly) is an endogenous agonist of GPR55, inducing concentration-dependent Ca2+ mobilization and MAPK activity in HAGPR55/CHO cells, attenuated by selective GPR55 antagonist ML193. Ca2+ mobilization assay, MAPK activity assay, GPR55 antagonist ML193 in GPR55-transfected CHO cells Biochemical and biophysical research communications Medium 28698140
2019 GPR55 agonists O-1602 and abnormal cannabidiol (Abn-CBD) protect pancreatic β-cells from ER stress-induced apoptosis by inducing CREB phosphorylation via CaMKIV, ERK1/2, and PKA, thereby upregulating anti-apoptotic genes Bcl-2 and Bcl-xL. Cell viability assays, Western blot for CREB phosphorylation and Bcl-2/Bcl-xL, kinase activation assays in MIN6 and Beta-TC-6 β-cell lines Biomedicine & pharmacotherapy Medium 30841431
2019 GPR55 activation in the ventral hippocampus with palmitoylethanolamide (PEA) produces a hyper-dopaminergic state (increased VTA dopaminergic firing/bursting) and disrupts social interaction, recognition memory, spatial and fear memory; effects are blocked by selective GPR55 antagonist and depend on NMDA receptor transmission. In vivo electrophysiology (VTA dopamine neuron recordings), behavioral pharmacology (social interaction, Morris water maze, fear conditioning), intra-vHipp stereotaxic microinjections, pharmacological antagonism Cannabis and cannabinoid research Medium 28861501
2022 Curcumin activates GPR55; the F190(5.47) residue of GPR55 is important for curcumin interaction; GPR55 activation by curcumin induces serum response element/SRF transcription via Rho kinase and stimulates GLP-1 secretion in GLUTag cells in a GPR55-dependent manner. GPCR activation screening, SRE-luciferase reporter, Rho kinase inhibitor, GPR55 antagonist, GLP-1 secretion assay, molecular docking/mutagenesis (F190 residue) NPJ science of food Medium 35031622
2018 GPR55 deficiency in mice results in decreased insulin sensitivity in skeletal muscle, adipose tissue, and liver (reduced PKB/Akt phosphorylation and downstream targets), increased adiposity, and reduced physical activity; GPR55 activation enhances insulin signaling in cultured muscle cells, adipocytes, and hepatocytes. GPR55 KO mouse phenotyping, insulin signaling Western blots (pAkt, downstream targets), cell-based insulin signaling assays, GPR55 siRNA knockdown in L6 myotubes FASEB journal High 30148676
2015 LPI enhances migration of placental venous endothelial cells via GPR55; this effect is inhibited by GPR55 antagonist O-1918, and is specific to venous but not arterial endothelial cells. Cell migration assay in primary placental endothelial cells, GPR55 antagonist O-1918, GPR55 expression confirmed by qPCR and immunocytochemistry Histochemistry and cell biology Medium 25869640
2013 GPR55 activation inhibits neurogenic contractions in mouse colon in a concentration-dependent manner; this effect is significantly reduced in GPR55−/− mice and is independent of CB1/CB2 receptors; the effect is predominantly prejunctional. Isometric tension recordings in colonic tissue strips from WT, GPR55−/−, and CB1−/−/CB2−/− mice Pharmacology High 22759743

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 The orphan receptor GPR55 is a novel cannabinoid receptor. British journal of pharmacology 1238 17876302
2008 GPR55 is a cannabinoid receptor that increases intracellular calcium and inhibits M current. Proceedings of the National Academy of Sciences of the United States of America 550 18263732
2007 Identification of GPR55 as a lysophosphatidylinositol receptor. Biochemical and biophysical research communications 374 17765871
2009 The putative cannabinoid receptor GPR55 affects osteoclast function in vitro and bone mass in vivo. Proceedings of the National Academy of Sciences of the United States of America 255 19805329
2009 The enigmatic pharmacology of GPR55. Trends in pharmacological sciences 236 19233486
2008 The GPR55 ligand L-alpha-lysophosphatidylinositol promotes RhoA-dependent Ca2+ signaling and NFAT activation. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 233 18757503
2009 Atypical responsiveness of the orphan receptor GPR55 to cannabinoid ligands. The Journal of biological chemistry 215 19723626
2008 The putative cannabinoid receptor GPR55 plays a role in mechanical hyperalgesia associated with inflammatory and neuropathic pain. Pain 214 18502582
2007 The novel endocannabinoid receptor GPR55 is activated by atypical cannabinoids but does not mediate their vasodilator effects. British journal of pharmacology 189 17704827
2010 The putative cannabinoid receptor GPR55 defines a novel autocrine loop in cancer cell proliferation. Oncogene 184 20838378
2009 Receptors for acylethanolamides-GPR55 and GPR119. Prostaglandins & other lipid mediators 182 19615459
2010 Pharmacological characterization of GPR55, a putative cannabinoid receptor. Pharmacology & therapeutics 178 20298715
2013 Cannabinoid- and lysophosphatidylinositol-sensitive receptor GPR55 boosts neurotransmitter release at central synapses. Proceedings of the National Academy of Sciences of the United States of America 170 23472002
2007 GPR55: a new member of the cannabinoid receptor clan? British journal of pharmacology 170 17876300
2010 GPR55 ligands promote receptor coupling to multiple signalling pathways. British journal of pharmacology 169 20136841
2011 GPR55 regulates cannabinoid 2 receptor-mediated responses in human neutrophils. Cell research 158 21467997
2011 The L-α-lysophosphatidylinositol/GPR55 system and its potential role in human obesity. Diabetes 143 22179809
2011 Minireview: recent developments in the physiology and pathology of the lysophosphatidylinositol-sensitive receptor GPR55. Molecular endocrinology (Baltimore, Md.) 132 21964594
2011 Modulation of L-α-lysophosphatidylinositol/GPR55 mitogen-activated protein kinase (MAPK) signaling by cannabinoids. The Journal of biological chemistry 128 22027819
2010 A role for L-alpha-lysophosphatidylinositol and GPR55 in the modulation of migration, orientation and polarization of human breast cancer cells. British journal of pharmacology 122 20590578
2014 Heteromerization of GPR55 and cannabinoid CB2 receptors modulates signalling. British journal of pharmacology 107 25048571
2009 Differential changes in GPR55 during microglial cell activation. FEBS letters 107 19464294
2014 Targeting CB2-GPR55 receptor heteromers modulates cancer cell signaling. The Journal of biological chemistry 98 24942731
2011 A role for the putative cannabinoid receptor GPR55 in the islets of Langerhans. The Journal of endocrinology 97 21885477
2013 GPR55, a G-protein coupled receptor for lysophosphatidylinositol, plays a role in motor coordination. PloS one 95 23565223
2017 Advances in the Physiology of GPR55 in the Central Nervous System. Current neuropharmacology 94 27488130
2015 The therapeutic potential of orphan GPCRs, GPR35 and GPR55. Frontiers in pharmacology 92 25926795
2016 GPR55 - a putative "type 3" cannabinoid receptor in inflammation. Journal of basic and clinical physiology and pharmacology 88 26669245
2018 GPR55 signalling promotes proliferation of pancreatic cancer cells and tumour growth in mice, and its inhibition increases effects of gemcitabine. Oncogene 85 30061636
2015 GPR55 promotes migration and adhesion of colon cancer cells indicating a role in metastasis. British journal of pharmacology 84 26436760
2018 Lysophosphatidylinositols, from Cell Membrane Constituents to GPR55 Ligands. Trends in pharmacological sciences 82 29588059
2015 Down-regulation of miR-675-5p contributes to tumor progression and development by targeting pro-tumorigenic GPR55 in non-small cell lung cancer. Molecular cancer 82 25889562
2012 The cannabinoid receptor CB1 modulates the signaling properties of the lysophosphatidylinositol receptor GPR55. The Journal of biological chemistry 81 23161546
2011 A novel CB receptor GPR55 and its ligands are involved in regulation of gut movement in rodents. Neurogastroenterology and motility 77 21726355
2012 The endocannabinoids anandamide and virodhamine modulate the activity of the candidate cannabinoid receptor GPR55. Journal of neuroimmune pharmacology : the official journal of the Society on NeuroImmune Pharmacology 76 22454039
2018 Anti-neuroinflammatory effects of GPR55 antagonists in LPS-activated primary microglial cells. Journal of neuroinflammation 72 30453998
2013 The actions and metabolism of lysophosphatidylinositol, an endogenous agonist for GPR55. Prostaglandins & other lipid mediators 72 23714700
2013 Evaluation of the insulin releasing and antihyperglycaemic activities of GPR55 lipid agonists using clonal beta-cells, isolated pancreatic islets and mice. British journal of pharmacology 70 23992544
2011 Anandamide exerts its antiproliferative actions on cholangiocarcinoma by activation of the GPR55 receptor. Laboratory investigation; a journal of technical methods and pathology 67 21464819
2019 Some Prospective Alternatives for Treating Pain: The Endocannabinoid System and Its Putative Receptors GPR18 and GPR55. Frontiers in pharmacology 66 30670965
2018 Localization of cannabinoid receptors CB1, CB2, GPR55, and PPARα in the canine gastrointestinal tract. Histochemistry and cell biology 64 29882158
2017 GPR55 regulates intraepithelial lymphocyte migration dynamics and susceptibility to intestinal damage. Science immunology 61 29222090
2010 GPR55: Current knowledge and future perspectives of a purported "Type-3" cannabinoid receptor. Current medicinal chemistry 61 20166924
2011 Identification of the GPR55 agonist binding site using a novel set of high-potency GPR55 selective ligands. Biochemistry 60 21534610
2011 L-α-lysophosphatidylinositol meets GPR55: a deadly relationship. Trends in pharmacological sciences 57 21367464
2018 Activation of GPR55 induces neuroprotection of hippocampal neurogenesis and immune responses of neural stem cells following chronic, systemic inflammation. Brain, behavior, and immunity 55 30465881
2017 The novel cannabinoid receptor GPR55 mediates anxiolytic-like effects in the medial orbital cortex of mice with acute stress. Molecular brain 53 28800762
2015 Role of the lysophosphatidylinositol/GPR55 axis in cancer. Advances in biological regulation 53 26588872
2011 Lysophosphatidylinositol causes neurite retraction via GPR55, G13 and RhoA in PC12 cells. PloS one 53 21904624
2018 GPR55 deficiency is associated with increased adiposity and impaired insulin signaling in peripheral metabolic tissues. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 52 30148676
2012 A potential role for GPR55 in gastrointestinal functions. Current opinion in pharmacology 52 23063456
2017 GPR55: a new promising target for metabolism? Journal of molecular endocrinology 51 28196832
2017 A putative lysophosphatidylinositol receptor GPR55 modulates hippocampal synaptic plasticity. Hippocampus 51 28653801
2016 GPR55-dependent stimulation of insulin secretion from isolated mouse and human islets of Langerhans. Diabetes, obesity & metabolism 49 27561953
2015 Central administration of GPR55 receptor agonist and antagonist modulates anxiety-related behaviors in rats. Fundamental & clinical pharmacology 48 25620584
2015 The Lysophosphatidylinositol Receptor GPR55 Modulates Pain Perception in the Periaqueductal Gray. Molecular pharmacology 48 25972448
2022 The neuroprotective effects of GPR55 against hippocampal neuroinflammation and impaired adult neurogenesis in CSDS mice. Neurobiology of disease 47 35490927
2012 Off-target cannabinoid effects mediated by GPR55. Pharmacology 47 22433274
2013 Identification of the GPR55 antagonist binding site using a novel set of high-potency GPR55 selective ligands. Biochemistry 46 24274581
2017 Palmitoylethanolamide Modulates GPR55 Receptor Signaling in the Ventral Hippocampus to Regulate Mesolimbic Dopamine Activity, Social Interaction, and Memory Processing. Cannabis and cannabinoid research 45 28861501
2014 GPR55: from orphan to metabolic regulator? Pharmacology & therapeutics 45 24972076
2013 Antagonists for the orphan G-protein-coupled receptor GPR55 based on a coumarin scaffold. Journal of medicinal chemistry 45 23679955
2012 GPR55 and GPR35 and their relationship to cannabinoid and lysophospholipid receptors. Life sciences 45 22820167
2015 Role of GPR55 during Axon Growth and Target Innervation. eNeuro 43 26730399
2020 Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors. British journal of pharmacology 42 31877572
2021 GPR119 and GPR55 as Receptors for Fatty Acid Ethanolamides, Oleoylethanolamide and Palmitoylethanolamide. International journal of molecular sciences 41 33494185
2010 GPR55, a lysophosphatidylinositol receptor with cannabinoid sensitivity? Current topics in medicinal chemistry 40 20370712
2017 Lysophosphatidylcholine and its phosphorothioate analogues potentiate insulin secretion via GPR40 (FFAR1), GPR55 and GPR119 receptors in a different manner. Molecular and cellular endocrinology 39 29225068
2016 Activation of the orphan receptor GPR55 by lysophosphatidylinositol promotes metastasis in triple-negative breast cancer. Oncotarget 37 27340777
2013 A potential role for GPR55 in the regulation of energy homeostasis. Drug discovery today 37 24370891
2016 Advances Towards The Discovery of GPR55 Ligands. Current medicinal chemistry 36 27109575
2018 Activation of GPR55 increases neural stem cell proliferation and promotes early adult hippocampal neurogenesis. British journal of pharmacology 35 29888782
2013 Genetic background can result in a marked or minimal effect of gene knockout (GPR55 and CB2 receptor) in experimental autoimmune encephalomyelitis models of multiple sclerosis. PloS one 35 24130809
2010 The putative cannabinoid receptor GPR55 promotes cancer cell proliferation. Oncogene 35 21057532
2021 Activation of GPR55 attenuates cognitive impairment and neurotoxicity in a mouse model of Alzheimer's disease induced by Aβ1-42 through inhibiting RhoA/ROCK2 pathway. Progress in neuro-psychopharmacology & biological psychiatry 34 34363866
2011 Functional polymorphism in the GPR55 gene is associated with anorexia nervosa. Synapse (New York, N.Y.) 34 20506567
2015 Activation of GPR55 Receptors Exacerbates oxLDL-Induced Lipid Accumulation and Inflammatory Responses, while Reducing Cholesterol Efflux from Human Macrophages. PloS one 33 25970609
2022 Activation of GPR55 attenuates cognitive impairment, oxidative stress, neuroinflammation, and synaptic dysfunction in a streptozotocin-induced Alzheimer's mouse model. Pharmacology, biochemistry, and behavior 32 35090841
2017 Inflammatory and Neuropathic Nociception is Preserved in GPR55 Knockout Mice. Scientific reports 31 28428628
2017 The LPI/GPR55 axis enhances human breast cancer cell migration via HBXIP and p-MLC signaling. Acta pharmacologica Sinica 31 29188802
2019 Targeting CB1 and GPR55 Endocannabinoid Receptors as a Potential Neuroprotective Approach for Parkinson's Disease. Molecular neurobiology 30 30687889
2015 The GPR55 agonist lysophosphatidylinositol relaxes rat mesenteric resistance artery and induces Ca(2+) release in rat mesenteric artery endothelial cells. British journal of pharmacology 30 25652040
2019 Potential metabolic and behavioural roles of the putative endocannabinoid receptors GPR18, GPR55 and GPR119 in feeding. Current neuropharmacology 29 31146657
2017 Lysophosphatidylcholine elicits intracellular calcium signaling in a GPR55-dependent manner. Biochemical and biophysical research communications 29 28552522
2012 Evidence for the putative cannabinoid receptor (GPR55)-mediated inhibitory effects on intestinal contractility in mice. Pharmacology 29 22759743
2013 Rod photoreceptors express GPR55 in the adult vervet monkey retina. PloS one 28 24244730
2022 The Cytotoxic Effects of Cannabidiol and Cannabigerol on Glioblastoma Stem Cells May Mostly Involve GPR55 and TRPV1 Signalling. Cancers 27 36497400
2016 Deletion of Gpr55 Results in Subtle Effects on Energy Metabolism, Motor Activity and Thermal Pain Sensation. PloS one 27 27941994
2009 Is GPR55 an anandamide receptor? Vitamins and hormones 27 19647110
2021 GPR55 in the brain and chronic neuropathic pain. Behavioural brain research 25 33745983
2019 l-α-Lysophosphatidylinositol (LPI) aggravates myocardial ischemia/reperfusion injury via a GPR55/ROCK-dependent pathway. Pharmacology research & perspectives 25 31149342
2022 Identification of G protein-coupled receptor 55 (GPR55) as a target of curcumin. NPJ science of food 24 35031622
2017 N-arachidonoyl glycine, another endogenous agonist of GPR55. Biochemical and biophysical research communications 24 28698140
2016 Treatment with the GPR55 antagonist CID16020046 increases neutrophil activation in mouse atherogenesis. Thrombosis and haemostasis 24 27465665
2021 Effects of a Novel GPR55 Antagonist on the Arachidonic Acid Cascade in LPS-Activated Primary Microglial Cells. International journal of molecular sciences 23 33801492
2019 Novel protective effect of O-1602 and abnormal cannabidiol, GPR55 agonists, on ER stress-induced apoptosis in pancreatic β-cells. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 23 30841431
2019 GPR55-mediated effects on brain microvascular endothelial cells and the blood-brain barrier. Neuroscience 23 31279825
2015 A role for GPR55 in human placental venous endothelial cells. Histochemistry and cell biology 23 25869640
2013 Regulation of GPR55 in rat white adipose tissue and serum LPI by nutritional status, gestation, gender and pituitary factors. Molecular and cellular endocrinology 23 24378736
2022 The oncogenic lysophosphatidylinositol (LPI)/GPR55 signaling. Life sciences 22 35500681