Structure-function relationships in sensory G protein-coupled receptors
(English) Perception of the world by an organism is not possible unless decoding the received information through its sensory systems. In vertebrates, G-protein-coupled receptors (GPCRs) and ion channels are principal categories of sensory receptors. This study has been dedicated to GPCRs which is o...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/692064 |
| Acceso en línea: | http://hdl.handle.net/10803/692064 https://dx.doi.org/10.5821/dissertation-2117-413885 |
| Access Level: | acceso abierto |
| Palabra clave: | Àrees temàtiques de la UPC::Enginyeria agroalimentària Àrees temàtiques de la UPC::Enginyeria química Àrees temàtiques de la UPC::Ciències de la salut 577 617 663/664 |
| Sumario: | (English) Perception of the world by an organism is not possible unless decoding the received information through its sensory systems. In vertebrates, G-protein-coupled receptors (GPCRs) and ion channels are principal categories of sensory receptors. This study has been dedicated to GPCRs which is one of the largest superfamily of membrane proteins in eukaryotes. GPCRs are widely studied because of their potential use as pharmacological targets in drug development. Currently, approximately thirty to forty percent of marketed pharmaceuticals target GPCRs. ln this thesis, the focus has been on bitter taste receptors and the visual photoreceptor rhodopsin (Rho). In particular, the effect of valproic acid (in its salt form, sodium valproate, VPA) on mutations associated with the retina! degenerative disease retinitis pigmentosa (RP) has been analyzed. Bitter taste receptors, called taste receptor type 2 (TAS2R), are G protein coupled receptors that protect humans from ingesting toxins also acting effectively in bitter compounds detection not only in the oral cavity, but in extra-oral tissues. One of the aims of this study was to analyze the potential expression of TAS2Rs in human skin cells. In this regard, the expression of different TAS2Rs subtypes (such as TAS2R4 and TAS2R20) in fibroblasts and keratinocytes of human primary skin cell cultures has been detected. Rho is a major protein of the retina that functions as a light receptor in the rod outer segment (ROS) of photoreceptor cells. Missense mutations in Rho can cause retinal degenerative diseases, including RP, that are mostly related to defects in Rho folding and/or trafficking. VPA is made of naturally occurring valeric acid and chemically is a simple eight-carbon branched-chain fatty acid. Recent work has investigated its use as an adjunct agent in cancer, neurodegenerative disease, human immunodeficiency virustherapy and Rho mutations and retinal disease because of its function as a histone deacetylase inhibitor. One of the main aims of this work is to find new ligands that can compensate for the harmful effects of RP mutations. We have found that VPA, in its sodium form, could be one of the candidate molecules for this purpose. To this aim, the effect of VPA on the structure and function of Rho has been studied. We have focused on the analysis of the conformational stability of heterologously expressed Rho, bovine wild-type (WT) and human WT Rho, and a Rho mutant, I307N, which has been shown to be an appropriate mouse model for studying retinal degeneration. We found no sign of enhanced stability far the dark inactive conformation of the I307N Rho mutant. Moreover, the photoactivated conformation of the mutant appeared to be destabilized by VPA as indicated by a faster decay of its active conformation. The Rho results obtained by carefully analyzing the spectral and biochemical properties of Rho heterologously expressed in cell cultures showed that VPA did not improve the structural stability of dark state conformation of the protein. The Meta II decay process, which could be interpreted as reflecting the active state conformational stability, did not show improved stability either. Therefore, our results support a destabilizing effect of VPA on Rho 1307N mutant associated with retinal degeneration. Our report opens up new opportunities for research on the effect of VPA on downstream Rho signaling elements. Analysis of protein properties for different concentrations of protein and VPA would require needs further investigation. These findings, at the molecular level, agree with recent clinical studies reporting negative effects of sodium valproate on the visual function of RP patients. |
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