Functional Selective Oxytocin-derived Agonists Discriminate between Individual G Protein Family Subtypes

Abstract

Background:The oxytocin receptor couples to multiple G proteins, leading to different physiological responses. Results: We screened for functional selective oxytocin receptor agonists and identified two analogs that activate individual G i subunits. Conclusion: Functional selective analogs discriminate among different receptor conformations coupled to G i proteins. Significance: These compounds will contribute to the development of selective drugs with new selectivity and therapeutic profiles.

Advances in the role of oxytocin receptors in human parturition

“…In human amnion, OTR was found to initiate its pro-inflammatory signal transduction via G αi -dependent signalling [53], whilst mainly G αq/11 coupling has been found to be involved in OT-induced myometrial contractions [52]. Recent findings show ligand-dependent discrimination of G protein family subtypes [54]. It has been suggested that binding of OTRantagonist, Atosiban, to myometrial OTR drive anti-labour signalling in the myometrium through inhibition of G αq/11 -dependent OT-mediated contractions but initiate pro-labour signalling in the amnion via G αi , resulting in activation of inflammation [53] (Figure 2).…”

Selective and Potent Agonists and Antagonists for Investigating the Role of Mouse Oxytocin Receptors

“…Even as OT has been recently reported to improve cognitive deficits in autistic patients (Modi and Young, 2012), its use is hampered by several of the following factors: 1) OT does not cross the blood-brain barrier and is administered intranasally, with unknown pharmacokinetics; 2) it also binds to and activates the V1aR and V1bR, which are highly expressed in the brain, where they exert different and even opposite effects (Pittman and Spencer, 2005); and 3) OT promotes the coupling of the OTR to different G proteins and b-arrestins (Busnelli et al, 2012) and, consequently, activates multiple signaling pathways whose precise roles within the brain are currently unknown. The development of more selective, potent, and therefore, longer-lasting analogs acting on brain is a priority in the field to understand how (in terms of biologic mechanisms) and where (in terms of neural specificity) OT exerts its effects.…”

Specific roles of Gi protein family members revealed by dissecting SST5 coupling in human pituitary cells

“…All G protein subunits coding plasmids for BRET experiments (Galphaq-97-Rluc, Galphai1-91-Rluc, Galphai2-91-Rluc, Galphai3-91-Rluc, GalphaoA-91-Rluc8 or GalphaoB-91-Rluc8) were previously described (Busnelli et al, 2012;Saulière et al, 2012). Ga oA C351I (Ga oA(PTX-r) ) and Ga oB C351I (Ga oB(PTX-r) ) plasmids were purchased from Missouri S&T cDNA Resource Center.…”

“…To investigate the specific ligand-induced G protein activation by wild-type SST5, we co-transfected HEK293 with wild-type SST5, Ga-RLuc, Gc2-GFP10 and complementary Gb1 subunit. In particular, we tested six different Ga-RLuc subunits (Ga i1,i2,i3,q,oA,oB ) by transfecting the corresponding plasmids (described in Saulière et al, 2012;Busnelli et al, 2012). A significant (P,0.001 versus PBS treated cells) BRET signal ratio decrease was obtained following wild-type SST5 activation by specific agonist BIM23206 (100 nM) with the Ga i1,2,3 and Ga oA,B subunits, whereas no decrease was observed with Ga q , as shown in Fig.…”

“…In order to identify the Ga protein family members involved in these effects, we employed a BRET biosensor that monitors the conformational rearrangements between probes inserted in heterotrimeric G protein complex (Galés et al, 2006;Busnelli et al, 2012;Saulière et al, 2012). In particular, the GDP/GTP exchange that occurs during receptor activation is translated into a decrease in the energy transfer between the donor (Renilla luciferase, Rluc, fused to a specific Ga subunit) and the acceptor (a variant of green fluorescent protein, GFP10 fused to the Gc 2 subunit).…”