RyR1-related myopathy mutations in ATP and calcium binding sites impair channel regulation

Area of Science:

• Biochemistry
• Molecular Biology
• Muscle Physiology

Background:

• The type 1 ryanodine receptor (RyR1) is crucial for skeletal muscle contraction, regulating intracellular calcium (Ca²⁺) release.
• RYR1-related disorders (RYR1-RD), including RYR1-related myopathy (RYR1-RM), are linked to inherited RyR1 mutations causing muscle weakness.
• Understanding RyR1 regulation by Ca²⁺ and ATP is vital for elucidating RYR1-RD pathophysiology.

Purpose of the Study:

• To investigate the functional significance of Ca²⁺ and ATP binding sites in RyR1 using structural insights.
• To determine how mutations in these sites affect RyR1 channel activity and regulation.
• To correlate RyR1 binding site mutations with clinical manifestations in RYR1-RD patients.

Main Methods:

• Utilized high-resolution cryogenic electron microscopy structures of skeletal muscle RyR1.
• Introduced specific mutations into putative Ca²⁺ and ATP binding sites of RyR1.
• Assessed the functional consequences of these mutations on RyR1 channel regulation and activity.

Main Results:

• Mutations in the Ca²⁺ binding site disrupted both low (activating) and high (inhibitory) affinity Ca²⁺ regulation, indicating a single regulatory site.
• Mutations affecting ATP binding abrogated binding, while those targeting the triphosphate tail modulated activation.
• Patients with mutations at these identified Ca²⁺ or ATP binding sites exhibit muscle weakness.

Conclusions:

• The study confirms the functional importance of Ca²⁺ and ATP binding sites in RyR1 regulation.
• Impaired Ca²⁺ or ATP binding/regulation of RyR1 channels can contribute to the muscle weakness seen in RYR1-RD.
• Structural information provides a basis for understanding RyR1-RD mechanisms and potential therapeutic targets.