Re-routing GPR56 signalling using Gα_12/13 G protein chimeras.

Area of Science:

• Molecular Pharmacology
• G protein-coupled receptor signaling

Background:

• Adhesion G protein-coupled receptors (aGPCRs) are a major GPCR subclass, yet lack clinically approved drugs.
• GPR56/ADGRG1, an aGPCR, is linked to polymicrogyria and cancer, making it a key therapeutic target.
• Studying Gα12/13 signaling, common in aGPCRs like GPR56, is difficult due to the absence of direct second messenger readouts.

Purpose of the Study:

• To engineer a method for detecting Gα12/13 signaling from aGPCRs.
• To validate the use of chimeric G proteins to translate Gα12/13 activity into a measurable signal.
• To assess the potential of these tools for drug discovery and aGPCR research.

Main Methods:

• Development of Gαq chimeric proteins (GαΔ6q12myr and GαΔ6q13myr) to couple Gα12/13 to Gαq signaling pathways.
• Utilized transcription factor luciferase reporter systems to detect GPR56 signaling.
• Performed inositol-3-phosphate assays to measure second messenger generation.

Main Results:

• Chimeric G proteins successfully translated basal and ligand-enhanced Gα12/13 signaling of GPR56 into a Gαq-mediated readout.
• Peptide ligands P7 and P19 were shown to enhance GPR56 signaling through the chimeric system.
• Direct influence on second messenger generation was demonstrated using inositol-3-phosphate assays.

Conclusions:

• Engineered chimeric G proteins provide a viable method to study Gα12/13 signaling in aGPCRs like GPR56.
• These tools can facilitate functional studies, drug screening, and the deorphanization of other aGPCRs.
• This approach overcomes a significant hurdle in aGPCR pharmacology and drug development.