Normal Mode Analysis of a Novel RYR2 Mutation in a Family with Recessively Inherited Ventricular Fibrillation Suggests a Dose Dependent Increase in Protein Flexibility - The 65th Annual Conference of the Israel Heart Society & The Israel Society of Cardiothoracic Surgery, 24-25 April 2018

Ayelet Shauer Cardiology, Hadassah-Hebrew University, Jerusalem, Please Select, Israel Oded Shor Cardiology, Hadassah-Hebrew University, Jerusalem, Please Select, Israel Yair Elitzur Cardiology, Hadassah-Hebrew University, Jerusalem, Please Select, Israel Nataly Kucherenko Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel Yulia Einav Faculty of Engineering, Holon Institute of Technology, Holon, Israel David Luria Cardiology, Hadassah-Hebrew University, Jerusalem, Please Select, Israel

Background: The cardiac ryanodine receptors (RyR2) play a major role in regulation of Ca²⁺ homeostasis in the sarcoplasmic reticulum. Mutations in RYR2 typically cause a dominant type Catecholamineric Polymorphic Ventricular Tachycardia (CPVT1). A family with cardiac arrest and ventricular fibrillation was found to have a novel missense mutation, G3118R. The mode of inheritance of the disease was autosomal recessive. The mechanism by which this mutation determines the clinical phenotype is unknown.

Aims: To model the effect of G3118R on RyR2 protein function and stability using a computational model.

Methods: Coarse-grained normal mode analysis (NMA) of the 3D tetrameric structure of human RyR2 solved by cryo-electron microscopy. The analysis was repeated after introducing the mutation into a single monomer, two, three or four monomers to capture the difference in protein flexibility in each case.

Results: G3118R caused an increase of flexibility in the adjacent monomers at a maximal distance of 68 ångströms. Each monomer harboring G3118R increased flexibility in an adjacent region on the neighboring monomer. We found a correlation between the amount of G3118R monomers and the number of monomers affected: with a single monomer harboring G3118R, an increase in flexibility was observed solely in the neighboring non mutated monomer, whereas when all four monomers were mutated, an increase in flexibility was observed in all four monomers. As a control we inserted N4104K missense mutation, known to cause a dominant type CPVT1. Here, a single mutated monomer was sufficient to increase flexibility in all four monomers.

Conclusion: We suggest G3118R missense mutation causes a recessively inherited fatal disease by regionally increasing the flexibility of a neighboring monomer in the tetrameric RyR2 protein structure. This is a novel mechanism for RyR2 mutation pathogenicity.