3-(2-Carboxyethyl)indole-2-carboxylic Acid Derivatives: Structural Requirements and Properties of Potent Agonists of the Orphan G Protein-Coupled Receptor GPR17.

The orphan receptor GPR17 may be a novel drug target for inflammatory diseases. 3-(2-Carboxyethyl)-4,6-dichloro-1 H-indole-2-carboxylic acid (MDL29,951, 1) was previously identified as a moderately potent GPR17 agonist. In the present study, we investigated the structure-activity relationships (SARs) of 1. Substitution of the indole 1-, 5-, or 7-position was detrimental. Only small substituents were tolerated in the 4-position while the 6-position accommodated large lipophilic residues. Among the most potent compounds were 3-(2-carboxyethyl)-1 H-indole-2-carboxylic acid derivatives containing the following substituents: 6-phenoxy (26, PSB-1737, EC50 270 nM), 4-fluoro-6-bromo (33, PSB-18422, EC50 27.9 nM), 4-fluoro-6-iodo (35, PSB-18484, EC50 32.1 nM), and 4-chloro-6-hexyloxy (43, PSB-1767, EC50 67.0 nM). (3-(2-Carboxyethyl)-6-hexyloxy-1 H-indole-2-carboxylic acid (39, PSB-17183, EC50 115 nM) behaved as a partial agonist. Selected potent compounds tested at human P2Y receptor subtypes showed high selectivity for GPR17. Docking into a homology model of the human GPR17 and molecular dynamic simulation studies rationalized the observed SARs.

Decoding signaling and function of the orphan G protein-coupled receptor GPR17 with a small-molecule agonist.

Replacement of the lost myelin sheath is a therapeutic goal for treating demyelinating diseases of the central nervous system (CNS), such as multiple sclerosis (MS). The G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor (GPCR) GPR17, which is phylogenetically closely related to receptors of the "purinergic cluster," has emerged as a modulator of CNS myelination. However, whether GPR17-mediated signaling positively or negatively regulates this critical process is unresolved. We identified a small-molecule agonist, MDL29,951, that selectively activated GPR17 even in a complex environment of endogenous purinergic receptors in primary oligodendrocytes. MDL29,951-stimulated GPR17 engaged the entire set of intracellular adaptor proteins for GPCRs: G proteins of the Gα(i), Gα(s), and Gα(q) subfamily, as well as ß-arrestins. This was visualized as alterations in the concentrations of cyclic adenosine monophosphate and inositol phosphate, increased Ca²âº flux, phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), as well as multifeatured cell activation recorded with label-free dynamic mass redistribution and impedance biosensors. MDL29,951 inhibited the maturation of primary oligodendrocytes from heterozygous but not GPR17 knockout mice in culture, as well as in cerebellar slices from 4-day-old wild-type mice. Because GPCRs are attractive targets for therapeutic intervention, inhibiting GPR17 emerges as therapeutic strategy to relieve the oligodendrocyte maturation block and promote myelin repair in MS.

Key determinants of nucleotide-activated G protein-coupled P2Y(2) receptor function revealed by chemical and pharmacological experiments, mutagenesis and homology modeling.

The P2Y(2) receptor, which is activated by UTP, ATP, and dinucleotides, was studied as a prototypical nucleotide-activated GPCR. A combination of receptor mutagenesis, determination of its effects on potency and efficacy of agonists and antagonists, homology modeling, and chemical experiments was applied. R272 (extracellular loop EL3) was found to play a gatekeeper role, presumably responsible for recognition and orientation of the nucleotides. R272 is also directly involved in binding of dinucleotides, which behaved as partial agonists. Y118A (3.37) mutation led to dramatically reduced efficacy of agonists; it is part of the entry channel as well as the triphosphate binding site. While the Y114A (3.33) mutation did not have any effect on agonist activities, the antagonist Reactive Blue 2 (6) was completely inactive at that mutant. The disulfide bridge Cys25-Cys278 was found to be important for agonist potency but neither for agonist efficacy nor for antagonist potency.

Discovery of potent and selective agonists for the free fatty acid receptor 1 (FFA(1)/GPR40), a potential target for the treatment of type II diabetes.

A series of 4-phenethynyldihydrocinnamic acid agonists of the free fatty acid receptor 1 (FFA(1)) has been discovered and explored. The preferred compound 20 (TUG-424, EC(50) = 32 nM) significantly increased glucose-stimulated insulin secretion at 100 nM and may serve to explore the role of FFA(1) in metabolic diseases such as diabetes or obesity.