Thesis, COLLÉGIALITÉ

Abstract

G protein-coupled receptors (GPCRs) are the largest class of drug targets for human diseases. An important number of them remain devoid of confirmed ligands. GPR101 is one of these orphan receptors, which constitutively activates Gs, Gq/11 and G12/13, and is expressed notably in the hypothalamus, but also in other organs such as the pituitary gland. Here we studied the role of extracellular loop 2 (ECL2), the longest and most diverse of the rhodopsin-like GPCRs, which contains a highly conserved cysteine through which it binds to the top of the transmembrane domain 3 (TM3). To address the function of the GPR101 ECL2, we used site-directed mutagenesis. Three mutants were designed and made: a substitution of both the cysteine at position 182 and the tryptophan at position 186, as well as a complete deletion of the ECL2 sequence. Using computational approaches, the ECL2 structure of GPR101 was proposed to consist of a pair of antiparallel β-sheets, which could belong to so-called “group B” of the newly established classification system for ECL2. At this stage, questions surrounding the function of ECL2 in GPR101 remain unanswered. Consequently, efforts need to be directed towards understanding the function of this receptor.