Abstract
GPR56/ADGRG1 is an adhesion GPCR and mutations on this receptor cause
cortical malformation due to the over-migration of neural progenitor
cells on the brain surface. At the pial surface, GPR56 interacts with
collagen III, induces Rho dependent activation through Gα12/13 and
inhibits the neuronal migration. In human glioma cells, GPR56 inhibits
cell migration through Gαq/11 dependent Rho pathway. GPR56-tetraspanin
complex is known to couple with Gαq/11. GPR56 is an aGPCR that couples
with various G proteins and signals through different downstream
pathways. In this study, BFPP mutants disrupting GPR56 function but
remain to be expressed on plasma membrane were used to study receptor
signaling through Gα12, Gα13 and Gα11 with BRET biosensors. GPR56 showed
coupling with all three G proteins and activated heterotrimeric G
protein signaling upon stimulation with Stachel peptide. However, BFPP
mutants showed different signaling defects for each G protein indicative
of distinct activation and signaling properties of GPR56 for Gα12, Gα13
or Gα11. β-arrestin recruitment was also investigated following the
activation of GPR56 with Stachel peptide using BRET biosensors.
N-terminally truncated GPR56 showed enhanced β-arrestin recruitment,
however neither wild-type receptor nor BFPP mutants gave any measurable
recruitment upon Stachel stimulation, pointing different activation
mechanisms for β-arrestin involvement.