AUTHOR=Zhang Yadan , Seidel Monika , Rabesahala de Meritens Camille , Beckmann Astrid , Ahmed Syeda , Hurtz Melanie , Lai F. Anthony , Zorio Esther , Parthimos Dimitris , Zissimopoulos Spyros 

TITLE=Disparate molecular mechanisms in cardiac ryanodine receptor channelopathies

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=Volume 11 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2024.1505698

DOI=10.3389/fmolb.2024.1505698

ISSN=2296-889X

ABSTRACT=AimsMutations in the cardiac ryanodine receptor (RyR2) are associated with catecholaminergic polymorphic ventricular tachycardia (CPVT). This study investigates the underlying molecular mechanisms for CPVT mutations within the RyR2 N-terminus domain (NTD).Methods and ResultsWe consulted the high-resolution RyR2 structure in both open and closed configuration to identify mutations G357S/R407I and A77T, which lie within the NTD intra- and inter-subunit interface with the Core Solenoid (CSol), respectively. Their structural and functional roles were compared to R169L, a mutation that lies within the NTD-NTD inter-subunit interface. Using chemical cross-linking and co-immunoprecipitation assays, we show that R169L disrupts NTD tetramerization, while it does not alter the NTD-CSol interaction. Single cell Ca2+ imaging revealed that R169L increases the number of spontaneous Ca2+ transients and the proportion of oscillating cells, while reducing the Ca2+ store content. G357S and R407I do not affect NTD tetramerization, but they also do not alter the NTD-CSol interaction. Functionally, RyR2G357S-expressing cells have Ca2+ handling properties similar to RyR2WT. A77T enhances the NTD-CSol interaction, while it does not affect NTD tetramerization. Like R169L, A77T also increases the number of spontaneous Ca2+ transients and the proportion of oscillating cells, and it reduces the Ca2+ store content. However, unlike R169L that displays Ca2+ transients of normal amplitude and shorter duration, Ca2+ transients for A77T are of smaller amplitude and normal duration.ConclusionThe NTD-CSol inter-subunit interface variant, A77T, produces a hyperactive channel by altering a different structure-function parameter to other CPVT mutations within the RyR2 NTD. Reduced NTD-NTD inter-subunit interaction and reinforced NTD inter-subunit interaction with CSol are distinct molecular mechanisms for gain-of-function RyR2 arrhythmogenic mutations.