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Structure-activity relationship study of indole-2-carboxamides identifies a potent allosteric modulator for the cannabinoid receptor 1 (CB1).

ABSTRACT: The cannabinoid CB1 receptor is involved in complex physiological functions. The discovery of CB1 allosteric modulators generates new opportunities for drug discovery targeting the pharmacologically important CB1 receptor. 5-Chloro-3-ethyl-N-(4-(piperidin-1-yl)phenethyl)-1H-indole-2-carboxamide (ORG27569; 1) represents a new class of indole-2-carboxamides that exhibit allostery of CB1. To better understand the SAR, a group of indole-2-carboxamide analogues were synthesized and assessed for allostery of the CB1 receptor. We found that within the structure of indole-2-carboxamides, the presence of the indole ring is preferred for maintaining the modulator's high binding affinity for the allosteric site but not for generating allostery on the orthosteric site. However, the C3 substituents of the indole-2-carboxamides significantly impact the allostery of the ligand. A robust CB1 allosteric modulator 5-chloro-N-(4-(dimethylamino)phenethyl)-3-pentyl-1H-indole-2-carboxamide (11j) was identified. It showed an equilibrium dissociation constant (KB) of 167.3 nM with a markedly high binding cooperativity factor (? = 16.55) and potent antagonism of agonist-induced GTP?S binding.

SUBMITTER: Mahmoud MM

PROVIDER: S-EPMC3880629 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Structure-activity relationship study of indole-2-carboxamides identifies a potent allosteric modulator for the cannabinoid receptor 1 (CB1).

Mahmoud Mariam M MM Ali Hamed I HI Ahn Kwang H KH Damaraju Aparna A Samala Sushma S Pulipati Venkata K VK Kolluru Srikanth S Kendall Debra A DA Lu Dai D

Journal of medicinal chemistry 20131007 20

The cannabinoid CB1 receptor is involved in complex physiological functions. The discovery of CB1 allosteric modulators generates new opportunities for drug discovery targeting the pharmacologically important CB1 receptor. 5-Chloro-3-ethyl-N-(4-(piperidin-1-yl)phenethyl)-1H-indole-2-carboxamide (ORG27569; 1) represents a new class of indole-2-carboxamides that exhibit allostery of CB1. To better understand the SAR, a group of indole-2-carboxamide analogues were synthesized and assessed for allos ...[more]

PMID: 24053617

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Project description:The cannabinoid receptor 1 (CB1), a member of the class A G protein-coupled receptor family, is expressed in brain tissue where agonist stimulation primarily activates the pertussis toxin-sensitive inhibitory G protein (G(i)). Ligands such as CP55940 ((1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3- hydroxypropyl)cyclohexan-1-ol) and ?(9)-tetrahydrocannabinol are orthosteric agonists for the receptor, bind the conventional binding pocket, and trigger G(i)-mediated effects including inhibition of adenylate cyclase. ORG27569 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)ethyl]amide) has been identified as an allosteric modulator that displays positive cooperativity for CP55940 binding to CB1 yet acts as an antagonist of G protein coupling. To examine this apparent conundrum, we used the wild-type CB1 and two mutants, T210A and T210I (D'Antona, A. M., Ahn, K. H., and Kendall, D. A. (2006) Biochemistry 45, 5606-5617), which collectively cover a spectrum of receptor states from inactive to partially active to more fully constitutively active. Using these receptors, we demonstrated that ORG27569 induces a CB1 receptor state that is characterized by enhanced agonist affinity and decreased inverse agonist affinity consistent with an active conformation. Also consistent with this conformation, the impact of ORG27569 binding was most dramatic on the inactive T210A receptor and less pronounced on the already active T210I receptor. Although ORG27569 antagonized CP55940-induced guanosine 5'-3-O-(thio)triphosphate binding, which is indicative of G protein coupling inhibition in a concentration-dependent manner, the ORG27569-induced conformational change of the CB1 receptor led to cellular internalization and downstream activation of ERK signaling, providing the first case of allosteric ligand-biased signaling via CB1. ORG27569-induced ERK phosphorylation persisted even after pertussis toxin treatment to abrogate G(i) and occurs in HEK293 and neuronal cells.

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Structure-activity relationship study of indole-2-carboxamides identifies a potent allosteric modulator for the cannabinoid receptor 1 (CB1).

Publications

Structure-activity relationship study of indole-2-carboxamides identifies a potent allosteric modulator for the cannabinoid receptor 1 (CB1).

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