Structure-based development of caged dopamine D2/D3 receptor antagonists

Abstract

Dopamine is a neurotransmitter of great physiological relevance. Disorders in dopaminergic signal transduction are associated with psychiatric and neurological pathologies such as parkinson's disease, schizophrenia and substance abuse. therefore, a detailed understanding of dopaminergic neurotransmission may provide access to novel therapeutic strategies for the treatment of these diseases. caged compounds with photoremovable groups represent molecular tools to investigate a biological target with high spatiotemporal resolution. Based on the crystal structure of the D 3 receptor in complex with eticlopride, we have developed caged D 2 /D 3 receptor ligands by rational design. We initially found that eticlopride, a widely used D 2 /D 3 receptor antagonist, was photolabile and therefore is not suitable for caging. Subtle structural modification of the pharmacophore led us to the photostable antagonist dechloroeticlopride, which was chemically transformed into caged ligands. Among those, the 2-nitrobenzyl derivative 4 (MG307) showed excellent photochemical stability, pharmacological behavior and decaging properties when interacting with dopamine receptor-expressing cells. Photopharmacology substantially contributes to our understanding of receptor function, potentially paving the way for new therapeutics 1. Hence, photoswitchable small molecules and neuropeptides have facilitated optical control of GPCR function 2. Moreover, photoactivable agonists and antagonists (caged ligands) have been developed 3. The rapid spatiotemporal control of such ligands upon photo-uncaging provides valuable insights into kinetics of association, dissociation as well as receptor-induced signalling. In vivo photopharmacology has been a significant challenge, because delivery of UV light to deep tissue infusion is technically challenging. However, new wireless devices being able to co-deliver light and drug or prodrug simultaneously may be a major breakthrough 4. Caged compounds consist of a biologically active molecule masked by a photolabile protective group, to prevent target binding and thus attenuate biological activity. Upon suitable illumination, photolytic cleavage of the cage leads to rapid release of the active molecule towards cellular targets via concentration jumps, ideally within the time span of a light pulse 5,6. Most prominent photosensitive masking groups are nitrobenzyl derivatives. These well-established cages have previously been introduced to a wide range of functionalities including ions 7,8 , phosphates 9 , phenols 10-13 , amines 13 and carboxylic acids 14. Photolytic cleavage of nitrobenzyl-type cages proceeds via a radical mechanism and is triggered by UV illumination with excitatory wavelengths ranging from 300 to 400 nm 15. Simple structural modifications involving formal introduction of two methoxy substituents allowed a cleavage with light of longer wavelengths 13,15,16. The neurotransmitter dopamine is critically involved in the regulation of movement, fine-motor control, emotions and behavior. Its physiolog...

Dopamine Receptor Subtypes, Physiology and Pharmacology: New Ligands and Concepts in Schizophrenia

“…Shorter D3 ligands will necessarily reside instead only in within the orthosteric pocket. Some interesting caged ligands for the D2/D3 orthosteric pocket could possibly help further pharmacological studies on this subject in native systems ( Gienger et al., 2020 ). There is a second interesting aspect in the pharmacology of D3 bitopic ligands.…”

Design and validation of the first family of photo-activatable ligands for melatonin receptors

“…For electrophysiological experiments rats (n=5) were euthanized with sodium pentobarbital and transcardially perfused with ice-cold and oxygenated (95%O2/5%CO 2 ) 'slicing' solution containing (in mM) sucrose (214), KCl (2.0), NaH 2 PO4 (1.2), NaHCO 3 (26), MgSO 4 (1.3), CaCl 2 (2.4), Dglucose (10). Following decapitation, the brain was extracted and the meninges gently removed.…”

“…Whole cell current-and voltage-clamp recordings were performed with pipettes (3-7MΩ when filled with intracellular solution) made from borosilicate glass capillaries (World Precision Instruments, Hitchin, Herts, UK) pulled on a P-97 Flaming/Brown micropipette puller (Sutter, Novato, CA, USA). The intracellular recording solution contained (in mM) K-gluconate (140), KCl (10), HEPES (10), EGTA (1), Na 2 ATP (2), pH 7.3 (with KOH). Recordings were performed using a Multiclamp 700B amplifier and pClamp11 software (Molecular Devices, San Jose, CA, USA).…”

“…In particular, light-controlled release of the active ligand upon uncaging provide valuable insights about receptor-induced signaling or binding kinetics. 10 Photopharmacology has never been applied to melatonin receptors but would be very useful tools for precise spatial-temporal activation of melatonin receptor in vitro and in vivo. Using the well-known photo-cleavable groups o -nitrobenzyl ( o- NB) and coumarin derivatives, we have developed here the first family of caged melatonin ligands, with the objective to modulate the activation of melatonin receptors in a light-controlled manner in vitro and in vivo.…”

Photopharmacology of Proteolysis-Targeting Chimeras: A New Frontier for Drug Discovery

“…However, there is a barrier to this technique. For instance, low energy of UV-Vis light is susceptible to absorption by endogenous substances, scattered in tissue, and blocked owing to the depth of tissue ( Gienger et al, 2020 ). Furthermore, high-intensity light, especially UV, triggers photodamage in cells and accelerates gene mutation, which may have significant impacts on health.…”