Two gates mediate NMDA receptor activity and are under subunit-specific regulation.

Area of Science:

• Neuroscience
• Molecular Biology
• Biophysics

Background:

• NMDA receptors (NMDARs) are crucial for synaptic plasticity and cognitive functions.
• NMDAR ion channel kinetics, including opening and closing, are vital for their signaling roles.
• Conserved glycines in transmembrane helices modulate NMDAR channel gating.

Purpose of the Study:

• To investigate the subunit-specific roles of conserved glycines in NMDAR channel kinetics.
• To elucidate the mechanisms by which GluN1 and GluN2 glycines regulate NMDAR gating.
• To understand how distinct gating mechanisms contribute to NMDAR function.

Main Methods:

• Molecular dynamics simulations were employed to model NMDAR gating.
• Functional experiments were conducted to validate simulation findings.
• Single channel recordings were analyzed to characterize channel activity.

Main Results:

• GluN1 glycine primarily regulates single channel events within clusters.
• GluN2 glycine primarily controls entry into and exit from channel clusters.
• Distinct gating mechanisms, involving M3 and M2 loop regions, are regulated by specific subunits.

Conclusions:

• NMDAR kinetics are governed by two distinct gates, each under subunit-specific control.
• The GluN1 and GluN2 subunits differentially regulate channel gating, leading to unique kinetic properties.
• This subunit-specific dual-gate mechanism underlies the precise role of NMDARs in synaptic signaling.