Subcellular distribution, trafficking and signal transduction of G protein-coupled receptors for energy metabolites

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G protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane receptors but accumulating evidence reveals that GPCRs are present and functional not only at the plasma membrane but may also signal from intracellular compartments. GPCR signaling from inside the cell is an aspect highly relevant in the context of metabolite-sensing GPCRs (msGPCRs), which are activated by (intracellularly synthesized) metabolic intermediates of central processes such as glycolysis, citric acid cycle or β-oxidation. Here, we will continue our effort to better understand, if and how selected msGPCRs that reside in intracellular compartments mediate their signal from there. As one representative msGPCR, succinate receptor is in the focus, for which we aim to understand the mechanisms behind its activation, signaling and trafficking dependent on its localization. Succinate receptor exhibits a strong link to metabolism and its agonist succinate gains increasingly relevance as oncometabolite. Therefore, we intent to develop a sensor that enables detection of succinate in live cells. On the other hand, we extent our focus to the oxoeicosanoid receptor and its evolutionary closely related family of hydroxycarboxylic acid receptors (HCAR). The oxoeicosanoid receptor exhibits unique structural features, an unusual subcellular distribution and is rather poorly understood. We aim to dismantle components involved in signaling and trafficking of this receptor in comparison to the msGPCRs of the HCAR family. Using bioluminescence and fluorescence resonance energy transfer (BRET/FRET), dynamic mass redistribution and multi-parametric surface plasmon resonance analyses in combination with several signal transduction assay systems and imaging techniques, we will address the challenging question of location-dependent signal transduction and trafficking of these msGPCRs. Our results will fundamentally increase our knowledge about selected GPCRs activated by energy metabolites and provide further evidence for their ‘not plasma membrane bound’ function.Ultimately, our study will result in an extended understanding of the molecular mechanism and structural requirements of (localization-dependent) signal transduction, trafficking and pharmacology of the selected msGPCRs. These results will be of great value for the assessment of their potential as targets for the development of anti-inflammatory or anti-cancer drugs.