Bile Acids Are Potential Negative Allosteric Modulators of M1 Muscarinic Receptors

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Bile acids have expanded roles in cell signaling beyond fat digestion.
• Bile acids are known to interact with muscarinic receptors.
• Cholesterol allosterically binds to M1 muscarinic receptors (M1R).

Purpose of the Study:

• To computationally test if bile acids allosterically bind to M1R.
• To investigate the mechanism of M1R activation and bile acid modulation.
• To explore the implications of bile acid-M1R interactions in cancer.

Main Methods:

• De novo site identification using the ligand competitive saturation (SILCS) method.
• Molecular dynamics simulations to analyze M1R activation and allosteric modulation.
• Computational testing of bile acid allosteric binding to M1R.

Main Results:

• Putative novel allosteric binding sites for bile acids on M1R were identified.
• Allosteric binding of bile acids negatively impacts M1R activation.
• Findings align with M1R's role in inhibiting colon cancer cell proliferation.

Conclusions:

• Bile acids may inhibit the tumor suppressor functions of M1R.
• This inhibition could contribute to increased colon cancer risk.
• Further experimental validation is needed to confirm these findings and explore broader implications for G protein-coupled receptors.