Allosteric rescuing of loss-of-function FFAR2 mutations

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• The free fatty acid receptor 2 (FFAR2), also known as GPR43, is a cell surface receptor activated by short-chain fatty acids (SCFAs) such as acetate and propionate.
• SCFAs are produced by gut microbiota and play roles in host metabolism and inflammation.
• Understanding FFAR2 activation mechanisms is crucial for developing therapeutics targeting metabolic and inflammatory diseases.

Purpose of the Study:

• To elucidate the molecular determinants responsible for FFAR2 activation by its endogenous ligands, acetate and propionate.
• To investigate the role of specific amino acid residues within the transmembrane domains of FFAR2 in ligand binding and receptor activation.
• To explore the potential for allosteric modulation of FFAR2 function.

Main Methods:

• Site-directed mutagenesis was employed to introduce specific amino acid substitutions in FFAR2.
• Receptor activation was assessed in response to acetate and a synthetic allosteric agonist.
• Analysis focused on residues within transmembrane domains (TM) 3, 4, 5, 6, and 7.

Main Results:

• Mutational analysis identified critical residues in TM 3, 4, 5, 6, and 7 essential for acetate binding and subsequent receptor activation.
• A mutation within the conserved D(E)RY motif significantly impaired acetate-induced FFAR2 activation.
• This impairment could be fully rescued by a novel synthetic allosteric agonist, indicating a distinct binding site and mechanism of action.

Conclusions:

• Specific residues in transmembrane domains of FFAR2 are vital for endogenous SCFA binding.
• FFAR2 activation can be modulated through allosteric mechanisms, independent of direct endogenous ligand binding sites.
• These findings provide a foundation for designing targeted allosteric ligands to modulate FFAR2 activity for therapeutic benefit in various disease contexts.