Present address: Hagedorn Research Institute, Novo Nordisk A/S, Gentofte, Denmark
The GPCR-associated sorting protein 1 regulates ligand-induced down-regulation of GPR55
Version of Record online: 23 MAR 2012
© 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society
British Journal of Pharmacology
Special Issue: Themed Section: Cannabinoids in Biology and Medicine, Part II. Guest Editors: Itai Bab and Steve Alexander
Volume 165, Issue 8, pages 2611–2619, April 2012
How to Cite
Kargl, J., Balenga, N., Platzer, W., Martini, L., Whistler, J. and Waldhoer, M. (2012), The GPCR-associated sorting protein 1 regulates ligand-induced down-regulation of GPR55. British Journal of Pharmacology, 165: 2611–2619. doi: 10.1111/j.1476-5381.2011.01562.x
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- Issue online: 23 MAR 2012
- Version of Record online: 23 MAR 2012
- Accepted manuscript online: 30 JUN 2011 01:40PM EST
- Received; 17 February 2011; Revised; 8 June 2011; Accepted; 12 June 2011
BACKGROUND AND PURPOSE Many GPCRs, including the CB1 cannabinoid receptor, are down-regulated following prolonged agonist exposure by interacting with the GPCR-associated sorting protein-1 (GASP-1). The CB1 receptor antagonist rimonabant has also recently been described to be an agonist at GPR55, a cannabinoid-related receptor. Here we investigated the post-endocytic properties of GPR55 after agonist exposure and tested whether GASP-1 is involved in this process.
EXPERIMENTAL APPROACH We evaluated the direct protein-protein interaction of GPR55 with GASP-1 using (i) GST-binding assays and (ii) co-immunoprecipitation assays in GPR55-HEK293 cells with endogenous GASP-1 expression. We further tested the internalization, recycling and degradation of GPR55 using confocal fluorescence microscopy and biotinylation assays in the presence and absence of GASP-1 (lentiviral small hairpin RNA knockdown of GASP-1) under prolonged agonist [rimonabant (RIM), lysophosphatidylinositol (LPI)] stimulation.
KEY RESULTS We showed that the prolonged activation of GPR55 with rimonabant or LPI down-regulates GPR55 via GASP-1. GASP-1 binds to GPR55 in vitro, and this interaction was required for targeting GPR55 for degradation. Disrupting the GPR55-GASP-1 interaction prevented post-endocytic receptor degradation, and thereby allowed receptor recycling.
CONCLUSION AND IMPLICATIONS These data implicate GASP-1 as an important regulator of ligand-mediated down-regulation of GPR55. By identifying GASP-1 as a key regulator of the trafficking and, by extension, functional expression of GPR55, we may be one step closer to gaining a better understanding of this receptor in response to cannabinoid drugs.
LINKED ARTICLES This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7