Photoswitchable allosteric ligands to modulate metabotropic glutamate receptors
[eng] Photopharmacology has the main purpose to allow the control of protein activity with light. The most exploited strategy used to achieve this objective is the freely diffusible photopharmacology and it is based in the use of photosensitive ligands. These ligands are small bioactive molecules, w...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/181968 |
| Acceso en línea: | https://hdl.handle.net/2445/181968 http://hdl.handle.net/10803/673024 |
| Access Level: | acceso abierto |
| Palabra clave: | Fotoquímica Farmacologia Receptors de neurotransmissors Dianes farmacològiques Malalties neurodegeneratives Photochemistry Pharmacology Neurotransmitter receptors Drug targeting Neurodegenerative Diseases |
| Sumario: | [eng] Photopharmacology has the main purpose to allow the control of protein activity with light. The most exploited strategy used to achieve this objective is the freely diffusible photopharmacology and it is based in the use of photosensitive ligands. These ligands are small bioactive molecules, which include a part of their structure (i.e. photoswitch) that can experience molecular changes upon illumination with a determined wavelength of light. These ligands can freely diffuse and they can be applied with systems expressing native proteins. Azobenzene is the most common photoswitch used in photopharmacology and it can switch with near UV light from the flat and long trans isomer to a shorter bent cis configuration. The reverse photoisomerization can be achieved either with visible light or thermally with light. Thus, if we include azobenzene in the molecular scaffold of a ligand by means of a replacement of a particular moiety (azologization), we can obtain new azo compounds that will resemble to the original ligand, but their structural shape will dramatically changes upon illumination (photoisomerization). Therefore, the two possible isomers will have distinct binding modes to the target protein and will lead to different protein activities under different light conditions, which is known as photoswitching. Metabotropic Glutamate Receptors (mGluRs) belong to the class C/Glutamate family of G Protein-Coupled Receptors and control many neuronal and glial functions. mGlu receptors are endogenously activated by glutamate, which is the major excitatory neurotransmitter in the central nervous system (CNS), but they can also be activated or inactivated by allosteric modulators. They are usually considered better drug candidates than the orthosteric ligands because usually highly specific for a receptor and able to modulate the activity of a given receptor without blocking endogenous ligand binding. First of all, we designed and synthesized three families of compounds, using an azo-replacement strategy, to obtain photoswitchable allosteric modulators with possible NAM activity in mGlu5 in the cis isomers, while in the trans form they are inactive. This behavior is easily controlled by illuminating with different wavelengths and it is reversible in vitro. All the three families were inactive as NAMs, but some results suggest that the compounds could act as mGlu5 PAMs in trans form. Studies are continuing in this direction (Chapter 1). Next, we carry out the design and synthesis of compounds to improve PAM activity at the mGlu4 receptor and increase selectivity over the other group III mGluRs of at least one azo benzene candidate with a structure similar to Optogluram, the first photoswitchable positive allosteric modulator for the mGlu4 receptor. We obtained Optogluram-2 with good pharmacological potency and improved the photoisomerization properties. Under 380 nm light, the potency of Optogluram-2 is significantly reduced. The change in photoinduced potency observed is greater in Optogluram-2 than in Optogluram. Optogluram-2 has similar potency to Optogluram but is more selective for mGlu4 both on the receptors of the same group III as on the other mGluRs. All this indicates that Optogluram-2 can induce an improved activated/deactivated profile change as well as have an optimal selectivity for more complex assays, such as in vivo assays (Chapter 2). Additionally, we synthesized two series of compounds to find the first photoswitchable compound to selectively enable optical control of the endogenous mGlu1 receptor. Photoglurax-1 arose as a PAM of mGlu1 with micromolar potency in the trans isomer. Under 380nm light, the potency is significantly reduced. Photoglurax-1 turned out to be an equipotent mGlu4 PAM and therefore its general profile is not suitable for in vivo translation as a possible mGlu1 PAM tool compound. However, a dual mGlu1/mGlu4 PAM activity could be intriguing for an antipsychotic agent, since mGlu4 PAM activity can alleviate catalepsy, a major adverse event with standard antipsychotic drug treatment. In contrast, Photoglurax-2 acts as a mGlu1 PAM and does not show any observable allosteric effect on mGlu4 or activity on mGlu5, and therefore Photoglurax-2 represents a potential in vivo photoswitchable PAM mGlu1 tool compound. Reversible monitoring of mGlu1 activity obtained with light can be very advantageous in studying the pharmacological and physiological implications of mGlu1 in many diseases with unprecedented precision (Chapter 3). Finally, we designed and synthesized a family of novel photoswitchable azoheteroarenes as mGlu1 NAMs with an active trans isomer and an inactive cis isomer to reversibly inactivate the function of the mGlu1 receptor. The potencies of the trans configurations of some compounds of the family are in the micromolar range . Unfortunately, after 400 nm illumination the results were inconclusive due to artifacts that could originate from a possible toxicity of cis azo compounds. More experiments should be done with cells that do not express mGlu1 and also changing the light system to corroborate eventual toxicity (Chapter 4). Likewise, we use some of these compounds in their trans form, therefore without applying light, as tools to expand the knowledge about the nature of the intermediate states induced by mGlu receptor agonists in studies of fluorescence conformational dynamics. Analysis of the effect of mGlu1 NAMs on receptor conformational changes is reported in Chapter 4. |
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