PT - JOURNAL ARTICLE AU - Lawrence C. Blume AU - Theresa Patten AU - Khalil Eldeeb AU - Sandra Leone-Kabler AU - Alexander A. Ilyasov AU - Bradley M. Keegan AU - Jeremy E. O’Neal AU - Caroline E. Bass AU - Roy R. Hantgan AU - W. Todd Lowther AU - Dana E. Selley AU - A­llyn C. Howlett TI - Cannabinoid Receptor Interacting Protein 1a Competition with <em>β</em>-Arrestin for CB<sub>1</sub> Receptor Binding Sites AID - 10.1124/mol.116.104638 DP - 2017 Feb 01 TA - Molecular Pharmacology PG - 75--86 VI - 91 IP - 2 4099 - http://molpharm.aspetjournals.org/content/91/2/75.short 4100 - http://molpharm.aspetjournals.org/content/91/2/75.full SO - Mol Pharmacol2017 Feb 01; 91 AB - 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.