Forced unbinding of GPR17 ligands from wild type and R255I mutant receptor models through a computational approach

MD suggested that GPR17 nucleotide binding pocket is enclosed between the helical bundle and extracellular loop (EL) 2. The driving interaction involves R255 and the UDP phosphate moiety. To support this hypothesis, steered MD experiments showed that the energy required to unbind UDP is higher for the WT receptor than for R255I. Three potential binding sites for pranlukast where instead found and analysed. In one of its preferential docking conformations, pranlukast tetrazole group is close to R255 and phenyl rings are placed into a subpocket highly conserved among GPCRs. Pulling forces developed to break polar and aromatic interactions of pranlukast were comparable. No differences between the WT receptor and the R255I receptor were found for the unbinding of pranlukast.These data thus suggest that, in contrast to which has been hypothesized for nucleotides, the lack of the R255 residue doesn't affect the binding of pranlukast a crucial role for R255 in binding of nucleotides to GPR17. Aromatic interactions are instead likely to play a predominant role in the recognition of pranlukast, suggesting that two different binding subsites are present on GPR17.Extracellular adenine and uracil nucleotides (e.g., ATP, ADP, UTP, UDP and sugar nucleotides) are signaling molecules involved in several patho physiological phenomena, from short-term signaling (neurotransmission, mechanosensory transduction, secretion and vasodilatation) to long-term functions (proliferation, differentiation, survival and death, development and post-injury repair) [1]. Conversely, cysteinyl-leukotrienes (cysteinyl-LTs) are inflammatory lipid mediators derived from arachidonic acid through the 5-lypoxigenase (5-LO) pathway, and are implicated in bronchial asthma, stroke and cardiovascular diseases [2]. Despite the fact that nucleotides and cysteinyl-LTs originate from totally independent metabolic pathways, several data suggest important functional interactions between two families of signaling molec