Structural basis for Ca2+-dependent, RyR2-selective stabilization by Ryanozole in CPVT

Otori, Y.; Murayama, T.; Tsutsumi, A.; Ishida, R.; Takeuchi, S.; Burton-Smith, R. N.; Murata, K.; Sakurai, T.; Kagechika, H.; Kurebayashi, N.; Ogawa, H.

doi:10.64898/2026.05.11.724262

bioRxiv · 10.64898/2026.05.11.724262

Structural basis for Ca2+-dependent, RyR2-selective stabilization by Ryanozole in CPVT

Otori, Y.·Murayama, T.·Tsutsumi, A.·Ishida, R.·Takeuchi, S.·Burton-Smith, R. N.·Murata, K.·Sakurai, T.·Kagechika, H.·Kurebayashi, N.·Ogawa, H.

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Abstract

The cardiac ryanodine receptor (RyR2) is a Ca{superscript 2} release channel essential for excitation-contraction coupling. RyR2 mutations cause severe arrhythmogenic disorders, including catecholaminergic polymorphic ventricular tachycardia (CPVT), through gain-of-function (GOF) effects leading to aberrant Ca{superscript 2} release. We have recently developed Ryanozole, a potential therapeutic compound for CPVT, which selectively stabilizes RyR2 in a Ca2+-dependent manner. Here, we define the mechanism of action of Ryanozole by combining high-resolution cryo-electron microscopy, targeted mutagenesis and functional assays. Ryanozole binds to the interface between the Ca{superscript 2}-binding site and the pore-forming S6 helix, interfering with conformational changes required for Ca{superscript 2}-induced channel opening at low Ca2+. We identified key residues for the binding and isoform-specific modulation of Ryanozole. Notably, Ryanozole-bound RyR2 retains its ability to open at high Ca2+ via unique conformational changes. These findings provide a structural basis for CPVT-targeted therapy and redefine the paradigm of small molecule-based regulation of large ion channels.

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Otori, Y., Murayama, T., Tsutsumi, A., Ishida, R., Takeuchi, S., Burton-Smith, R. N., Murata, K., Sakurai, T., Kagechika, H., Kurebayashi, N., Ogawa, H.. 2026-05-14. Structural basis for Ca2+-dependent, RyR2-selective stabilization by Ryanozole in CPVT. https://doi.org/10.64898/2026.05.11.724262

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