A dynamic and screening-compatible nanoluciferase-based complementation assay enables profiling of individual GPCR-G protein interactions

G protein-coupled receptors (GPCRs) are
currently the target of more than 30% of the
marketed medicines. However, there is an important
medical need for ligands with improved
pharmacological activities on validated drug targets.
Moreover, most of these ligands remain poorly
characterized, notably because of a lack of
pharmacological tools. Thus, there is an important
demand for innovative assays that can detect and
drive the design of compounds with novel or
improved pharmacological properties. In particular,
a functional and screening-compatible GPCR-G
protein interaction assay is still unavailable. Here,
we report on a nanoluciferase-based
complementation technique to detect ligands that
promote a GPCR-G protein interaction. We
demonstrate that our system can be used to profile
compounds with regard to the G proteins they
activate through a given GPCR. Furthermore, we
established a proof of applicability of screening for
distinct G proteins on dopamine receptor D2 whose
differential coupling to Gαi/o family members has
been extensively studied. In a D2-Gαi1 versus D2-
Gαo screening, we retrieved five agonists that are
currently being used in antiparkinsonian
medications. We determined that in this assay,
piribedil and pergolide are full agonists for the
recruitment of Gαi1 but are partial agonists for Gαo,
that the agonist activity of ropinirole is biased in
favor of Gαi1 recruitment, and that the agonist
activity of apomorphine is biased for Gαo. We
proposed that this newly developed assay could be
used to develop molecules that selectively modulate
a particular G protein pathway.