Molecular basis for gating of cardiac ryanodine receptor explains the mechanisms for gain- and loss-of function...

Area of Science:

• Cardiovascular Biology
• Molecular Physiology
• Structural Biology

Background:

• Cardiac ryanodine receptor (RyR2) is a critical Ca2+ release channel essential for heart excitation-contraction coupling.
• RyR2 dysfunction due to mutations is linked to serious cardiac arrhythmias.
• The structural mechanisms governing RyR2 channel gating and the impact of mutations remain poorly understood.

Purpose of the Study:

• To elucidate the atomic-level gating mechanisms of the cardiac ryanodine receptor (RyR2).
• To investigate how specific mutations alter RyR2 channel function and contribute to arrhythmogenic diseases.

Main Methods:

• High-resolution cryo-electron microscopy (cryo-EM) to determine RyR2 structures.
• Quantitative functional analysis of RyR2 channels with targeted residue mutations.

Main Results:

• Identified two key gating mechanisms: pore-proximal interactions stabilizing the channel and surrounding interactions enabling Ca2+ activation.
• Demonstrated that mutations in pore-proximal regions lead to gain-of-function (hyperactivity).
• Showed that mutations in surrounding activation regions result in loss-of-function.

Conclusions:

• Revealed fundamental gating principles of the RyR2 channel at the atomic level.
• Provided structural insights into how pathogenic mutations cause gain- and loss-of-function RyR2 channelopathies.
• Established a structural framework for understanding RyR2-related cardiac diseases.