Potent and Selective Peptide-based Inhibition of the G Protein Gαq

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• Direct modulation of heterotrimeric G proteins, unlike G protein-coupled receptors, remains challenging due to limited available compounds.
• Active Gαq interacts with its effectors, phospholipase C (PLC)-β and Rho guanine nucleotide exchange factors (RhoGEFs), via a conserved binding site.

Purpose of the Study:

• To design and characterize novel peptide inhibitors targeting the active Gαq protein.
• To evaluate the specificity and efficacy of these peptides in cellular and in vivo models.

Main Methods:

• Peptide synthesis based on the Gαq-effector binding interface.
• In vitro binding assays to assess Gαq affinity and specificity.
• Cellular assays measuring Gαq-dependent effector activation (PLC-β3, p63RhoGEF).
• In vivo electrophysiology in mouse prefrontal cortex to assess neuronal depolarization.
• Genetically encoded peptide expression for cellular inhibition studies.

Main Results:

• Synthesized peptides bound active Gαq in vitro with high affinity, competing with effectors.
• The representative peptide demonstrated specificity for active Gαq, not binding inactive forms or other Gα subunits.
• Peptides effectively inhibited Gαq-mediated activation of PLC-β3 and p63RhoGEF in cells.
• Peptides prevented G protein-coupled receptor-induced neuronal depolarization downstream of Gαq.
• Genetically encoded peptides also inhibited Gαq-dependent PLC-β3 activation.

Conclusions:

• Novel peptides effectively inhibit active Gαq signaling by targeting its effector binding site.
• These peptides exhibit high specificity and can be delivered cell-penetratingly or genetically encoded.
• The developed peptides represent promising molecular probes, drug leads, and biosensors for Gαq research.