Modulation of Cannabinoid Receptor Interacting Protein 1a (CRIP1a) Expression Using Adeno‐Associated Virus and Effects on Striatal Neuropharmacology and Neuronal Cells in Culture

Abstract

CB1 cannabinoid receptors and the D2 dopamine receptors are both GPCRs that associate with interacting proteins (CRIP1a and DRIP) that bind to the C‐terminus of the receptor. The DRIP neuronal calcium sensor‐1 is involved in Ca2+ mediated regulation of the D2 receptor, whereas the recently discovered cannabinoid receptor interacting protein (CRIP1a), has been shown to suppress the tonic inhibition of voltage‐gated Ca2+ channels induced by CB1 (Niehaus et al., 2007). Therefore, CRIP1a may provide a new avenue for modulation of the endocannabinoid system.AAV that contain transgenes to express shRNA designed to knock down CB1, D2R, or CRIP1a were created and injected via stereotaxically. Striata from AAV‐D2R and AAV‐CB1 shRNA‐treated rats displayed a significant reduction in D2 and CB1 mRNA levels, respectively. The AAV overexpressing CRIP1a virus increased CRIP1a mRNA levels without altering CB1 levels. However, significant reductions occurred in levels of preprodynorphin(Pdyn) and preproenkephalin‐1(Penk‐1).In vitro, N18TG2 stably transfected with CRIP1a‐pcDNA3.1 displayed increased levels of CRIP1a, Pdyn, and delta opioid receptor mRNA levels without effecting CB1 levels. Additionally, CRIP1a overexpressers had a significant reduction in CB1 mediated phosphorylation of ERK during Rimonabant‐sensitive basal conditions. However, CB1 agonist mediated effects on maximum ERK phosphorylation were unaltered in CRIP1a overexpressors.These studies provide both in vivo and in vitro insight into the mechanisms involved in CRIP1a modulation of CB1 receptors.