GPR55 ligands promote receptor coupling to multiple signalling pathways

Abstract

Background and purpose: Although GPR55 is potently activated by the endogenous lysophospholipid, L-alysophosphatidylinositol (LPI), it is also thought to be sensitive to a number of cannabinoid ligands, including the prototypic CB1 receptor antagonists AM251 and SR141716A (Rimonabant ® ). In this study we have used a range of functional assays to compare the pharmacological activity of selected cannabinoid ligands, AM251, AM281 and SR141716A with LPI in a HEK293 cell line engineered to stably express recombinant, human GPR55. Experimental approach: We evaluated Ca 2+ signalling, stimulation of extracellular signal regulated kinase (ERK1/2) mitogen activated kinase MAP-kinases, induction of transcriptional regulators that are downstream of GPR55, including nuclear factor of activated T cells (NFAT), nuclear factor-kB (NF-kB) and cAMP response element binding protein (CREB), as well as receptor endocytosis. In addition, we assessed the suitability of a novel, label-free assay for GPR55 ligands that involves optical measurement of dynamic mass redistribution following receptor activation. Key results: GPR55 linked to a range of downstream signalling events and that the activity of GPR55 ligands was influenced by the functional assay employed, with differences in potency and efficacy observed. Conclusions and implications:Our data help to resolve some of the issues surrounding the pharmacology of cannabinoid ligands at GPR55 and highlight some differences in effector coupling associated with distinct GPR55 ligands. (2010) AM281, 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide; CREB, cAMP response element binding protein; ERK1/2, extracellular signal regulated kinase 1/2; G13, Ga13 protein; GFP, green fluorescent protein; GPR55, G protein-coupled receptor 55; GPR55-HEK293, stable HEK293 cells expressing 3xHA-GPR55; HA, haemaglutinin; HBS, HEPES-buffered saline; LPI, L-alysophosphatidylinositol; MAP, mitogen activated kinase; NFAT, nuclear factor of activated T British Journal of Pharmacology

Modulation of l-α-Lysophosphatidylinositol/GPR55 Mitogen-activated Protein Kinase (MAPK) Signaling by Cannabinoids

“…In some studies, SR141716A is reported to be an inhibitor (6), and in other studies, the compound is reported to be an agonist of GPR55 (5,13,14). This is of major importance as SR141716A (Rimonabant) was widely prescribed to patients as an anti-obesity agent and was withdrawn because of mental health issues.…”

“…To date, certain arylpyrazole CB 1 receptor antagonists such as Rimonabant (also known as SR141716A or Acomplia) and AM251 have been reported to be GPR55 agonists (5,13,14). However, other groups have suggested that Rimonabant is a GPR55 antagonist (6,8).…”

“…Among these factors, the most investigated is ERK1/2 (5-9, 11, 15-17). Other nuclear transcription factors recruited by GPR55 activation are nuclear factor of activated T cells (NFAT) (9,13), cAMP-response element-binding protein (CREB), nuclear factor -light chain enhancer of activated T cells (NF-B) (4, 9, 13), p38 MAPK (18), and Akt serine/threonine protein kinase (8,11).…”

The orphan G protein-coupled receptor GPR55 promotes cancer cell proliferation via ERK

“…Nonetheless, all the functions described so far for LPI on GPR55 come from experiments in which LPI was exogenously added to the cultured cells, and therefore evidence for the role of the naturally occurring lipid in more physiological settings is still missing. It has also been shown that several cannabinoid-type compounds modulate this receptor (Ryberg et al, 2007;Lauckner et al, 2008;WaldeckWeiermair et al, 2008;Henstridge et al, 2009Henstridge et al, , 2010Kapur et al, 2009;Yin et al, 2009). However, the inconsistencies among the pharmacological results obtained so far (some compounds being active in some reports and inactive in others, some being agonists in some studies and antagonists in others, and so on) do not entirely clarify whether GPR55 is an actual cannabinoid receptor (Brown and Robin Hiley, 2009;Ross, 2009).…”

Resonant waveguide grating imager for live cell sensing

“…[4][5][6][7][8][9][10][11] Conventional systems employ a stationary array of fiber optics to repetitively scan a microtiter plate. 12 As a result, only cells along the scanning path ͑ϳ100 m in width͒ are sampled to generate an averaged response.…”