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Cell Signal. 2015 Mar;27(3):716-726. doi: 10.1016/j.cellsig.2014.11.006. Epub 2014 Nov 17.

Cannabinoid receptor interacting protein (CRIP1a) attenuates CB1R signaling in neuronal cells.

Author information

1
Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, NC 27157 USA.
2
Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298 USA.
#
Contributed equally

Abstract

CB1 cannabinoid receptors (CB1R) are one of the most abundantly expressed G protein coupled receptors (GPCR) in the CNS and regulate diverse neuronal functions. The identification of GPCR interacting proteins has provided additional insight into the fine-tuning and regulation of numerous GPCRs. The cannabinoid receptor interacting protein 1a (CRIP1a) binds to the distal carboxy terminus of CB1R, and has been shown to alter CB1R-mediated neuronal function [1]. The mechanisms by which CRIP1a regulates CB1R activity have not yet been identified; therefore the focus of this investigation is to examine the cellular effects of CRIP1a on CB1R signaling using neuronal N18TG2 cells stably transfected with CRIP1a over-expressing and CRIP1a knockdown constructs. Modulation of endogenous CRIP1a expression did not alter total levels of CB1R, ERK, or forskolin-activated adenylyl cyclase activity. When compared to WT cells, CRIP1a over-expression reduced basal phosphoERK levels, whereas depletion of CRIP1a augmented basal phosphoERK levels. Stimulation of phosphoERK by the CB1R agonists WIN55212-2, CP55940 or methanandamide was unaltered in CRIP1a over-expressing clones compared with WT. However, CRIP1a knockdown clones exhibited enhanced ERK phosphorylation efficacy in response to CP55940. In addition, CRIP1a knockdown clones displayed a leftward shift in CP55940-mediated inhibition of forskolin-stimulated cAMP accumulation. CB1R-mediated Gi3 and Go activation by CP99540 was attenuated by CRIP1a over-expression, but robustly enhanced in cells depleted of CRIP1a. Conversely, CP55940-mediated Gi1 and Gi2 activation was significant enhanced in cells over-expressing CRIP1a, but not in cells deficient of CRIP1a. These studies suggest a mechanism by which endogenous levels of CRIP1a modulate CB1R-mediated signal transduction by facilitating a Gi/o protein subtype preference for Gi1 and Gi2, accompanied by an overall suppression of G-protein-mediated signaling in neuronal cells.

KEYWORDS:

CB(1) receptor; CRIP1a; ERK1/2; Endocannabinoid; G protein; cAMP

PMID:
25446256
PMCID:
PMC4332989
DOI:
10.1016/j.cellsig.2014.11.006
[Indexed for MEDLINE]
Free PMC Article

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