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Mol Pharmacol. 2017 Feb;91(2):75-86. doi: 10.1124/mol.116.104638. Epub 2016 Nov 28.

Cannabinoid Receptor Interacting Protein 1a Competition with β-Arrestin for CB1 Receptor Binding Sites.

Author information

1
Department of Physiology and Pharmacology (L.C.B., T.P, K.E., S.L.-K., A.A.I., B.M.K., J.E.O., C.E.B., A.C.H.) and Department of Biochemistry and Center for Structural Biology (R.R.H., W.T.L.), Wake Forest University Health Sciences, Winston-Salem, North Carolina; Department of Chemistry (T.P.) and Center for Molecular Signaling (W.T.L., A.C.H.), Wake Forest University, Winston-Salem, North Carolina; Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (D.E.S.); and AL Azhar Faculty of Medicine, New Damietta, Egypt (K.E.).
2
Department of Physiology and Pharmacology (L.C.B., T.P, K.E., S.L.-K., A.A.I., B.M.K., J.E.O., C.E.B., A.C.H.) and Department of Biochemistry and Center for Structural Biology (R.R.H., W.T.L.), Wake Forest University Health Sciences, Winston-Salem, North Carolina; Department of Chemistry (T.P.) and Center for Molecular Signaling (W.T.L., A.C.H.), Wake Forest University, Winston-Salem, North Carolina; Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia (D.E.S.); and AL Azhar Faculty of Medicine, New Damietta, Egypt (K.E.) ahowlett@wakehealth.edu.

Abstract

Cannabinoid receptor interacting protein 1a (CRIP1a) is a CB1 receptor (CB1R) distal C-terminal-associated protein that alters CB1R interactions with G-proteins. We tested the hypothesis that CRIP1a is capable of also altering CB1R interactions with β-arrestin proteins that interact with the CB1R at the C-terminus. Coimmunoprecipitation studies indicated that CB1R associates in complexes with either CRIP1a or β-arrestin, but CRIP1a and β-arrestin fail to coimmunoprecipitate with each other. This suggests a competition for CRIP1a and β-arrestin binding to the CB1R, which we hypothesized could attenuate the action of β-arrestin to mediate CB1R internalization. We determined that agonist-mediated reduction of the density of cell surface endogenously expressed CB1Rs was clathrin and dynamin dependent and could be modeled as agonist-induced aggregation of transiently expressed GFP-CB1R. CRIP1a overexpression attenuated CP55940-mediated GFP-CB1R as well as endogenous β-arrestin redistribution to punctae, and conversely, CRIP1a knockdown augmented β-arrestin redistribution to punctae. Peptides mimicking the CB1R C-terminus could bind to both CRIP1a in cell extracts as well as purified recombinant CRIP1a. Affinity pull-down studies revealed that phosphorylation at threonine-468 of a CB1R distal C-terminus 14-mer peptide reduced CB1R-CRIP1a association. Coimmunoprecipitation of CB1R protein complexes demonstrated that central or distal C-terminal peptides competed for the CB1R association with CRIP1a, but that a phosphorylated central C-terminal peptide competed for association with β-arrestin 1, and phosphorylated central or distal C-terminal peptides competed for association with β-arrestin 2. Thus, CRIP1a can compete with β-arrestins for interaction with C-terminal CB1R domains that could affect agonist-driven, β-arrestin-mediated internalization of the CB1R.

PMID:
27895162
PMCID:
PMC5267523
DOI:
10.1124/mol.116.104638
[Indexed for MEDLINE]
Free PMC Article

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