In silico interaction analysis of cannabinoid receptor interacting protein 1b (CRIP1b) – CB1 cannabinoid receptor

Abstract

Cannabinoid Receptor Interacting Protein isoform 1b (CRIP1b) is known to interact with the CB1 receptor. Alternative splicing of the CNRIP1 gene produces CRIP1a and CRIP1b with a difference in the third exon only. Exons 1 and 2 encode for a functional domain in both proteins. CRIP1a is involved in regulating CB1 receptor internalization, but the function of CRIP1b is not very well characterized. Since there are significant identities in functional domains of these proteins, CRIP1b is a potential target for drug discovery. We report here predicted structure of CRIP1b followed by its interaction analysis with CB1 receptor by in-silico methods. A number of complementary computational techniques, including, homology modeling, ab-initio and protein threading, were applied to generate three-dimensional molecular models for CRIP1b. The computed model of CRIP1b was refined, followed by docking with C terminus of CB1 receptor to generate a model for the CRIP1b- CB1 receptor interaction. The structure of CRIP1b obtained by homology modelling using RHO_GDI-2 as template is a sandwich fold structure having beta sheets connected by loops, similar to predicted CRIP1a structure. The best scoring refined model of CRIP1b in complex with the CB1 receptor C terminus peptide showed favourable polar interactions. The overall binding pocket of CRIP1b was found to be overlapping to that of CRIP1a. The Arg82 and Cys126 of CRIP1b are involved in the majority of hydrogen bond interactions with the CB1 receptor and are possible key residues required for interactions between the CB1 receptor and CRIP1b.

Cannabinoid Receptor Interacting Protein 1a (CRIP1a): Function and Structure

“…It is important to remember, however, that given the low sequence identity (15.9 % and 25.7% sequence identity for CRIP1a and CRIP1b, respectively), the structure needs to be evaluated carefully. A subsequent study by Singh and colleagues confirmed the structure prediction for CRIP1a and extended the analysis to CRIP1b using similar methods [55].…”

“…In particular, they highlighted that the Lys130 side chain nitrogen atom stabilizes the backbone conformation of Ser464, Thr465, and Asp466. Similar studies of CRIP1b predicted that the binding pocket for the CB 1 C-terminus included residues Asn61, Ile64, Leu68, Glu77, Asp79, Arg82, Tyr85, Tyr89, Cys126, Tyr124, and Met128 [55]. Given the ambiguity of the potential binding sites, significantly more work is required to understand the structure of CRIP1a/b and how it interacts with the CB 1 receptor.…”

“…The primary structure of CRIP1a has been identified and found to be highly conserved across species (Figure 2). However, there appears to be no amino acid sequence homology with other known proteins [10,54,55]. Due to the fact that there are currently no experimentally-determined structures of CRIP1a and CRIP1b, researchers have had to rely on ab initio modeling and in silico binding experiments in an attempt to develop and test hypotheses concerning the interaction between the CB 1 receptor and CRIP1a/b.…”

“…Computational studies on CRIP1a by Ahmed and colleagues [54] used a general strategy that included analysis of the protein sequence, and then used homology modeling to establish an ab initio model. The predicted model showed greatest structural homology with the protein guanine nucleotide dissociation inhibitor 2 (Rho-GDI2) [54,55]. The structure was energy minimized to satisfy chemical restraints and Ramachandran plot requirements.…”

Bioligands Acting on the Cannabinoid Receptor CB1 for the Treatment of Withdrawal Syndrome Caused by Cannabis sativa

“…There are several computational methods; among them, homology modeling is being used in cannabinoid studies [103], considering that the drugs utilized during the withdrawal syndrome of C. sativa act at a symptomatic level. The resolution of the crystalline structure of the CB1cannabinoid receptor is recent [19], and this fact favored in silico studies that evolve toward the planning of molecules that act as selective agonists of this receptor, mainly studies related to better understanding of the interaction and the relation structure-activity of Recent Advances in Cannabinoid Research synthetic cannabinoids [104].…”