| Autor: |
Anisha Korde, Michelle Glass, David B. Finlay, V. Kiran Vemuri, Morag R. Hunter, Natasha L. Grimsey, Erin E. Cawston, Alexandros Makriyannis |
| Rok vydání: |
2017 |
| Předmět: |
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| Zdroj: |
British Journal of Pharmacology. 174:2545-2562 |
| ISSN: |
0007-1188 |
| DOI: |
10.1111/bph.13866 |
| Popis: |
BACKGROUND AND PURPOSE CB1 cannabinoid receptor signalling is canonically mediated through inhibitory Gαi proteins, but signalling through other G proteins occurs under some circumstances; Gαs being the most characterised secondary pathway. Determinants of this signalling switch identified to date include Gαi blockade, CB1/D2 dopamine receptor co-stimulation, CB1 agonist class, and cell background. The aim of this study was to examine the effects of receptor number and ligand dependence on CB1 signalling. EXPERIMENTAL APPROACH CB1 was expressed in HEK cells at different levels, and signalling characterisation was performed for cAMP by real-time BRET biosensor – CAMYEL – and for phospho-ERK by AlphaScreen. Characterisation of a novel irreversible antagonist of CB1, AM6544, was performed by homogenate and whole cell radioligand binding assays. KEY RESULTS In HEK cells expressing high levels of CB1, agonist treatment resulted in cAMP stimulation; a response not previously known to be mediated by receptor number. Δ9-THC and BAY59-3074 increased cAMP only in high-expressing cells that had been pre-treated with pertussis toxin, and agonists demonstrated more diverse signalling profiles in the stimulatory pathway than they elicited in the canonical inhibitory pathway. CB1 pharmacological knockdown and Gαi1 supplementation were sufficient to restore canonical Gαi signalling to high expressing cells. Constitutive signalling in both lower- and higher-expressing cells was Gαi-mediated. CONCLUSION AND IMPLICATIONS CB1 coupling to opposing G proteins is determined by both receptor and G protein number, and this underpins a mechanism for non-canonical signalling in a fashion consistent with Gαs signalling. CB1 is known to mediate opposite consequences in endpoints such as tumour viability receptor number-dependently, and our study may help to explain such effects at the level of G protein coupling. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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