Relevant molecular and functional g-protein coupled receptor interactions in neuroinflammation and addiction
- Autores: Edgar Angelats Canals
- Directores de la Tesis: Rafael Franco Fernandez (codir. tes.), Gemma Navarro Brugal (codir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Francisco J. López Soriano (presid.), Daniel Fourmy (secret.), Eva Martínez-Pinilla (voc.)
- Programa de doctorado: Programa de Doctorado en Biomedicina por la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
The thesis project has focused in members of the G-protein coupled receptor (GPCR) superfamily: the CB1 and CB2 cannabinoid receptors, which are part of the endocannabinoid system, and the ghrelin receptor GHS-R1a. The endocannabinoid system regulates, in mammals, body temperature, neurotransmission or immune response among others. Indeed, the endocannabinoid system has been related to processes coursing with neuroinflammation, in particular those that are derived from neurodegenerative diseases like Alzheimer’s disease (AD) or Parkinson’s disease (PD). It has been investigated the role of CB1-CB2 receptor heteromers in a neuroinflammatory context. Both in an immortalised microglial cell line, N9, and microglial primary cultures, there is an increase of CB2R and CB1-CB2 heteromer expression upon treatment of the cells with LPS and INF-γ. Interestingly, the characteristic negative cross-talk of CB1-CB2 receptor heteromers becomes positive after the treatment. Such change in the cannabinoid receptor signalling was observed in an animal model of the AD. In addition, in the hemilesioned rat model of PD, the administration of levodopa and acquisition of dyskinesia leads to a significant increase in CB1-CB2 heteroreceptor expression.
GPCR activity can be regulated by interaction with diverse proteins. The thesis project has focused in the potential interaction of the cannabinoid CB1R with calcium-binding proteins. Calcium sensor proteins modulate cell events depending on the concentration of cytosolic Ca2+. First of all, an interaction of NCS1 and calneuron1 (but not caldendrin) calcium sensors with the receptor has been established. At low intracellular calcium levels, the predominant interaction occurs between CB1R and NCS1, while at high intracellular calcium levels CB1R-calneuron1 interactions are more likely to occur. At the functional level, the cAMP signalling of CB1R is abolished when calneuron1 is interacting with the receptor, whereas the CB1R-NCS1 interaction does not promote any signalling disturbance in the cAMP-mediated pathway.
Whereas GHS-R1a is a GPCR, an alternative splicing of the gene that codes for the receptor generates the GHS-R1b isoform. This is a truncated protein that lacks the 6th and 7th transmembrane domains: it is unable to bind ligands or to signal. In this thesis, it has been addressed the role of the GHS-R1b isoform. The results show that the GHS-R1b isoform enables GHS-R1a expression at the plasma membrane due to heteromerization. Moreover, GHS-R1b can allosterically modulate GHS-R1a. When there is a low GHS-R1b/GHS-R1a expression ratio, GHS-R1a is functional, but at high GHS-R1b/GHS-R1a expression ratio, GHS-R1b negatively modulates GHS-R1a activity. These results obtained in a heterologous expression system were confirmed in striatal and hippocampal neuron cultures.
GHS-R1a, a receptor expressed in the reward pathway, exerts a role in controlling food intake. In this thesis project, a molecular relationship between GHS-R1a and cocaine consumption has been discovered. First of all, an interaction of GHS-R1a and sigma-1 receptor was demonstrated. Secondly, cocaine binding to sigma-1 receptor leads to a negative modulation of GHS-R1a signalling. Moreover, GHS-R1a-sigma-1 interactions are increased in rats after acute cocaine consumption, while its presence in rats chronically treated with cocaine is similar to that in controls. A molecular mechanism is suggested through which cocaine, via GHS-R1a/sigma-1 receptor complexes, can influence food consumption.
