The structural study of mutation-induced inactivation of human muscarinic receptor M4

Area of Science:

• Biochemistry
• Pharmacology
• Structural Biology

Background:

• Human muscarinic receptor M4 (a GPCR) is a key target for Alzheimer's and schizophrenia treatments.
• Developing selective ligands for muscarinic acetylcholine receptor (mAchR) subtypes is challenging due to similar binding pockets.
• M4 receptor activity influences motor symptoms in Parkinson's disease.

Purpose of the Study:

• To develop a strategy for stabilizing the M4 receptor in an inactive conformation.
• To facilitate the design of selective M4 antagonists.
• To enable structure determination of the inactive M4 receptor.

Main Methods:

• Rational design of an N449^7.49R mutation to mimic allosteric sodium binding and induce an inactive state.
• Determination of the crystal structure of the mutation-induced inactive M4 receptor.
• Comparative analysis with other mAchR structures and functional assays.
• Virtual screening using the determined inactive M4 structure.

Main Results:

• The N449^7.49R mutation successfully stabilized the M4 receptor in an inactive state.
• The crystal structure of the inactive M4 receptor was determined.
• Functional assays confirmed the stabilization of the inactive state.
• Virtual screening revealed that the inactive M4 state preferentially binds antagonists over agonists.

Conclusions:

• The N449^7.49R mutation provides a powerful method to stabilize GPCRs, including M4, in inactive conformations.
• This approach enhances the feasibility of determining GPCR structures.
• The findings support the development of selective M4 antagonists for neurological disorders.